EP3697861A1

EP3697861A1 - Adhesive strips with partially foamed self-adhesive mass

Info

Publication number: EP3697861A1
Application number: EP18789335.9A
Authority: EP
Inventors: Anika PETERSEN; Franciska Lohmann; Axel Burmeister; Anna Blazejewski
Original assignee: Tesa SE
Current assignee: Tesa SE
Priority date: 2017-10-17
Filing date: 2018-10-05
Publication date: 2020-08-26
Also published as: DE102018200957A1; TW201922997A; CN111247221A; KR20190105140A; KR102108719B1; WO2019076652A1; CN111247221B

Abstract

The invention relates to adhesive strips having at least one layer (SK1) of a self-adhesive mass partially foamed with microballoons, wherein the degree of foaming of the layer (SK1) is at least 20% and less than 100%. The invention also relates to a method for the production thereof and to the use thereof for adhesively bonding components such as, in particular, batteries and electronic devices such as, in particular, mobile devices.

Description

Pressure-sensitive adhesive strip with partially foamed self-adhesive

The invention relates to a pressure-sensitive adhesive strip with teilgeschäumter self-adhesive, a process for its preparation and its use for the bonding of components such as in particular batteries and electronic devices such as mobile devices in particular.

Adhesive tapes are often used for the bonding of micro components, for example in devices in the consumer electronics industry. In order to make this possible, it is necessary for the shape of the adhesive tape section to be adapted to the shape of the component. In this case, often difficult geometries are necessary, which are obtained by punching the tape. For example, web widths of stamped parts of a few millimeters or even less are not uncommon. When applying these sensitive tapes to the components, it often results in deformation of the stamped parts.

In order to suppress or at least reduce the deformation, it has proven to be advantageous to integrate a film, for example a PET film, into the adhesive tapes as a middle layer in order to absorb the tensile forces during application.

Adhesions with such adhesive tapes are also increasingly used when the component is exposed to shock loads. Bonding with pressure-sensitive adhesive strips which have a viscoelastic, syntactically foamed core, a stabilizing film and two self-adhesive layers on the outer layers have proved to be particularly shock-resistant.

These pressure-sensitive adhesive strips are so powerful that, under shock load, a cohesive break can be observed within the pressure-sensitive adhesive strip. The bond between the foamed core and the stabilizing film fails, and foam and film separate from each other.

Foamed PSA systems have long been known and described in the prior art. In principle, polymer foams can be produced in two ways. On the one hand by the action of a propellant gas, whether it is added as such or resulting from a chemical reaction, on the other hand by the incorporation of hollow spheres in the material matrix. Foams made in the latter way are called syntactic foams.

In a syntactic foam, hollow spheres such as glass spheres or ceramic hollow spheres (microspheres) or microballoons are incorporated in a polymer matrix. As a result, the voids are separated from one another in a syntactic foam and the substances (gas, air) located in the cavities are separated from the surrounding matrix by a membrane.

With micro hollow balls foamed masses are characterized by a defined cell structure with a uniform size distribution of the foam cells. With hollow microspheres, closed-cell foams are obtained without cavities, which are distinguished, among other things by a better sealing effect against dust and liquid media compared to open-cell variants. In addition, chemically or physically foamed materials are more prone to irreversible collapse under pressure and temperature, and often exhibit lower cohesive strength.

Particularly advantageous properties can be achieved if expandable microspheres (also referred to as "microballoons") are used as microspheres for foaming. By virtue of their flexible, thermoplastic polymer shell, such foams have a higher adaptability than those which are compatible with non-expandable, non-polymeric hollow microspheres (for example They are more suitable for compensating for manufacturing tolerances, which are the rule for injection molded parts, for example, and because of their foam character they can also better compensate for thermal stresses For example, even if the foam has a lower density than the matrix, it is possible to produce foams having a higher cohesive strength than the polymer matrix alone foam properties such as adaptability rough substrates with a high cohesive strength for self-adhesive foams can be combined.

The devices in the consumer electronics industry include electronic, optical and precision mechanical devices in the meaning of this application, in particular such devices as those in Class 9 of the International Classification of Goods and Services for the Registration of Marks (Classification of Nice); 10th edition (NCL (10-2013)); in the case of electronic, optical or fine mechanical equipment, and in particular watches and timepieces in accordance with Class 14 (NCL (10-2013))

• Scientific, nautical, surveying, photographic, film, optical,

Weighing, measuring, signaling, checking (supervision), life-saving and teaching apparatus and instruments;

• apparatus and instruments for conducting, switching, transforming, storing, regulating and controlling electricity;

• image recording, processing, transmitting and reproducing apparatus, such as

for example TV and the like

Acoustic recording, processing, transmitting and reproducing apparatus such as radios and the like

· Computers, computing devices and data processing equipment, math instruments and instruments, computer accessories, office equipment - such as printers, fax machines, copiers, typewriters -, data storage devices

• Remote communication and multifunction devices with remote communication function, such as telephones, answering machines

· Chemical and physical measuring instruments, control devices and instruments, such as

for example, battery chargers, multimeters, lamps, tachometers

• Nautical equipment and instruments

• Optical devices and instruments

• Medical equipment and instruments and those for athletes

· Watches and chronometers

Solar cell modules, such as electrochemical dye solar cells, organic

Solar cells, thin-film cells,

• Fire extinguishers. The technical development is increasingly aimed at such devices that are becoming smaller and lighter, so that they can be carried by their owner at any time and are usually carried regularly. Today, this is increasingly done by implementing small weights and / or suitable size of such devices. Such devices are referred to in this document as mobile devices or portable devices. In this development trend, precision mechanical and optical devices are increasingly (also) provided with electronic components, which increases the possibilities of minimization. Due to the entrainment of the mobile devices, they are subject to increased loads, in particular mechanical loads, for example due to abutment against edges, dropping, contact with other hard objects in the pocket, or even permanent movement due to being carried along. However, mobile devices are also exposed to heavier loads due to moisture, temperature effects and the like than such "immobile" devices that are usually installed indoors and are not or hardly moved.

Accordingly, the invention particularly preferably relates to mobile devices, since the pressure-sensitive adhesive strip used according to the invention has a particular benefit here due to the unexpectedly good, namely even better, properties (very high shock resistance). Below are some portable devices listed without wishing to be unnecessarily limited by the specific representatives in this list with respect to the subject invention.

• Cameras, digital cameras, photography accessories (such as light meters, flash units, irises, camera housings, lenses, etc.), movie cameras, video cameras · small computers (mobile computers, handheld computers, calculators), laptops, notebooks, netbooks, ultrabooks, tablet computers, handhelds, electronic diaries and organizers (so-called "electronic organizers" or "personal digital assistants", PDA, palmtops), modems,

• computer accessories and control units for electronic devices, such as mice, drawing pads, graphics tablets, microphones, speakers, game consoles, gamepads,

Remote controls, remote controls, touch pads

• Monitors, displays, screens, touch screens (touch screens, touch screen devices), projectors

• electronic book readers ("e-books"),

· Small TV sets, pocket televisions, movie players, video players • Radios (also small and pocket radios), Walkmen, Discmen, music players for example CD, DVD, Bluray, cassettes, USB, MP3, headphones

• Cordless phones, mobile phones, smart phones, two-way radios, hands-free kits, pagers (pagers, beepers)

• Mobile defibrillators, blood glucose meters, blood pressure monitors, pedometers, heart rate monitors

• Flashlights, laser pointers

• Mobile detectors, optical enlargers, remote vision devices, night vision devices · GPS devices, navigation devices, portable interface devices of the

satellite communications

• Data storage devices (USB sticks, external hard drives, memory cards)

• Wrist watches, digital watches, pocket watches, chain watches, stop watches. For these devices in particular adhesive tapes are required, which have a high holding power.

Furthermore, it is important that the adhesive tapes do not fail in their holding performance if the mobile device, for example a mobile phone, is dropped and hits the ground. The adhesive strip must therefore have a very high shock resistance.

EP 2 832 780 A1 relates to a pressure-sensitive adhesive foam containing a rubber elastomer, at least one hydrocarbon tackifier and a crosslinker selected from the group of multifunctional (meth) acrylate compounds.

JP 2010 / 070,655 A relates to a composition containing a styrene-based thermoplastic elastomer (A), a tackifier (B) and heat-expandable microcapsule-type foaming agent.

DE 10 2008 056 980 A1 relates to a self-adhesive composition consisting of a mixture comprising:

A polymer blend of thermoplastic and / or non-thermoplastic elastomers with at least one vinylaromatic block copolymer which contains greater than 30% by weight of 1,2-linked diene in the elastomer block, • at least one adhesive resin

Expanded polymeric microspheres.

WO 2009/0901 19 A1 relates to a pressure-sensitive adhesive which contains expanded microballoons, wherein the adhesive force of the adhesive containing the expanded microballoons in comparison to the bond strength of a composition and formulation-identical adhesive which defoams by destroying the cavities formed by the expanded microballoons is reduced by a maximum of 30%. WO 2003/01 1954 A1 relates to a foamed pressure-sensitive adhesive article, the article a) comprising a polymer mixture comprising at least one styrenic block copolymer and at least one polyarylene oxide, and b) one or more foamable polymer microspheres. WO 00/006637 A1 relates to an article comprising a polymer foam having a substantially smooth surface with an R _a of less than about 75 μm, the foam containing a plurality of microspheres, at least one of which is an expandable polymeric microsphere. WO 2010/147888 A2 relates to a foam comprising a polymer, a plurality of at least partially expanded expandable polymer microspheres, and from 0.3 to 1.5% by weight of a silica having a surface area of at least 300 square meters per gram according to ASTM D1993-03 (2008). DE 10 2015 206 076 A1 relates to a pressure-sensitive adhesive strip, which can be detached again by stretching stretching essentially in the bonding plane without residues and without destruction, from one or more adhesive layers, all of which consist of a pressure-sensitive adhesive foamed with microballoons, and optionally from one or more intermediate carrier layers, characterized in that the pressure-sensitive adhesive strip consists exclusively of said adhesive layers and optionally present intermediate carrier layers and the one outer upper and one outer lower surface of the pressure-sensitive adhesive strip are formed by the adhesive layer (s). The removable pressure-sensitive adhesive strip is characterized by its pronounced shock resistance. DE 10 2016 202 479 A1 describes a four-layered adhesive tape in which a foamed inner layer is additionally reinforced by a PET stabilizing film. With such a structure, particularly shock-resistant adhesive tapes could be offered.

The still unpublished patent application DE 10 2016 209 707 of the same applicant as this document describes a pressure-sensitive adhesive strip of three layers, comprising an inner layer F of a non-stretchable film carrier, a layer SK1 of a self-adhesive mass, which is disposed on one of the surfaces of the film support layer F and which is based on a foamed acrylate compound,

and a self-adhering layer SK2 disposed on the surface of the film support layer F opposite to the layer SK1 and based on a foamed acrylate composition. Such a structure also offered shock-resistant adhesive tapes.

The still unpublished EP 17 182 443 relates to a pressure-sensitive adhesive strip of at least three layers, comprising an inner layer F of a non-extensible film carrier, a layer SK1 of a self-adhesive mass, which is disposed on one of the surfaces of the film support layer F and on one with microballoons foamed Vinylaromatenblockcopolymermasse, and a layer SK2 of a self-adhesive mass, which is disposed on the surface of the film support layer F opposite the layer SK1 and which is based on a microballoon foamed Vinylaromatenblockcopolymer mass, wherein the average diameter of the cavities formed by the microballoons in the self-adhesive layers SK1 and SK2 are each independently 20 to 60 μηη. The pressure-sensitive adhesive strip has a high shock resistance.

The still unpublished EP 17 182 447 relates to a pressure-sensitive adhesive strip which comprises at least one layer SK1 of a self-adhesive composition based on a vinylaromatic block copolymer composition foamed with microballoons, wherein the average diameter of the voids formed in the self-adhesive composition layer SK1 45 to 1 10 μηη is. The pressure-sensitive adhesive strip has in particular an improved heat resistance. Object of the present invention over the prior art is to provide a further pressure-sensitive adhesive strip with a high shock resistance, preferably the shock resistance should be further improved. In particular, there is a need for such a pressure-sensitive adhesive strip in the production of mobile devices in which bonding composites with high shock resistance are to be realized.

The object is surprisingly achieved with a generic pressure-sensitive adhesive strip according to the invention, as laid down in the main claim 1. The subject of the dependent claims are advantageous embodiments of the pressure-sensitive adhesive strip.

Accordingly, the invention relates to a pressure-sensitive adhesive strip which comprises at least one layer SK1, preferably exactly one layer SK1, of a self-adhesive mass partially foamed with microballoons (MBs), the degree of foaming of the layer SK1 being at least 20% and less than 100%.

The pressure-sensitive adhesive strips according to the invention with partially foamed self-adhesive composition surprisingly have comparable and often even improved shock resistance compared with the corresponding pressure-sensitive adhesive strips with fully foamed self-adhesive composition of the prior art. Thus, the impact strength in the z-direction (breakdown strength) and preferably also the impact resistance in the x, y-direction (transverse impact strength) are comparable or frequently even improved. In addition, the pressure-sensitive adhesive strips with partially foamed self-adhesive composition typically have improved bonding strengths (bond strengths) compared to the corresponding pressure-sensitive adhesive strips with fully foamed self-adhesive composition from the prior art.

The present invention further relates to a process for the preparation of such a pressure-sensitive adhesive strip in which the self-adhesive layers SK1 and optionally SK2 partially foamed with microballoons are produced by heat-treating the corresponding self-adhesive layers containing unexpanded microballoons at a temperature suitable for foaming for such a period of time the subsequent cooling of the layers, the desired degree of partial foaming is achieved.

Moreover, the present invention relates to the use of the pressure-sensitive adhesive strip for bonding components such as in particular batteries and electronic devices such as especially mobile devices, such as cell phones. With regard to its property profile, the use of the pressure-sensitive adhesive strip according to the invention in the automotive sector, in construction and in the printing industry is also of particular interest.

By exposing a self-adhesive composition layer containing unexpanded microballoons, also referred to as "unfoamed" self-adhesive layer in the present invention, to an appropriate elevated temperature, the microballoons expand, causing the layer to foam Further temperature increase softens the shell, whereupon the microballoons expand, and if the temperature is kept constant or increased further, the continual expansion results in an increasingly thinner shell and ever larger microballoon diameters The skilled person knows that the temperature chosen for the foaming in addition to the Mikroballontyp further from the desired Schäu speed depends. The absolute density of the layer decreases by the continuous foaming over a certain period of time. The state of lowest density is defined as full expansion, full foaming, 100% expansion and 100% foaming, respectively. In the processes of the prior art, the microballoon-containing layers are usually completely expanded, since it is assumed that the desired properties of the layers are achieved with the lowest possible amount of microballoon or to optimize the properties of the layers for a given microballoon fraction. The Vollexpansion is therefore considered economically or technically advantageous. Subsequently, however, the expanded microballoons shrink together again at the selected foaming temperature and an overexpanded state is achieved, wherein the density of the layer in the overexpanded state is greater again. The reason for the overexpansion is that the propellant begins to diffuse increasingly through the shell and to form free gas bubbles in the surrounding polymer. The overexpansion is undesirable, especially as the escaping gas collects in the surrounding polymer and forms there with increasing time ever larger free gas bubbles, which reduce the cohesion. In addition, these free gases diffuse into the environment through the surrounding polymer over time, and the polymer loses foam. On the other hand, if the layer is cooled before full foaming is achieved, the expansion of the microballoons stops and with it the decrease of the layer density. The term "cooling" here and in the following also includes passive cooling by removing the heating, ie typically cooling at room temperature (20 ° C.) Furthermore, according to the invention, the term "cooling" also includes heating at a lower temperature. This results in a teilgeschäumte layer. The process of foaming by means of microballoons makes it possible to adjust the degree of expansion of the microballoons by suitable choice of the parameters temperature and time, which of course also includes an expansion of 100%, ie full foaming. The energy input required to achieve the desired degree of expansion also depends on the thickness of the adhesive layer to be foamed, with higher energy input being required as the thickness increases. In practice, typically the various parameters are iteratively changed until the desired degree of foaming is achieved. FIGS. 3 a to 4 e show unfoamed, partly foamed, fully expanded and overexpanded self-adhesive layers under the reflected-light microscope.

The degree of foaming (degree of expansion) of the partially foamed layer can now be calculated as follows: Foaming degree = (density of the layer containing unexpanded microballoons minus density of the partially foamed layer) / (density of the layer containing unexpanded microballoons minus density of the fully foamed layer).

The degree of foaming is thus the quotient

(i) the difference in the density of the layer containing unexpanded microballoons and the density of the partially-foamed layer, and

(ii) the difference in the density of the layer containing unexpanded microballoons and the density of the fully-foamed layer. As an alternative to determining the degree of foaming over the densities of the unfoamed, partially foamed and fully foamed layer, the degree of foaming can also be determined analogously via the thicknesses of the unfoamed, partially foamed and fully foamed layer. The degree of foaming is determined in this case as the quotient (i) the difference in thickness of the partially-foamed layer and the thickness of the layer containing unexpanded microballoons, and

(ii) the difference in the thickness of the fully-foamed layer and the thickness of the layer containing unexpanded microballoons.

The layer containing unexpanded microballoons, the partially-foamed layer and the fully-foamed layer are, of course, surface-weight and formulation-identical layers in these calculation formulas. the partially-foamed as well as the fully-foamed layer may be provided by the foaming of the layer containing unexpanded microballoons at a suitable temperature and for a suitable time.

Alternatively, the degree of foaming of a partially foamed layer can also be determined retrospectively, i. starting from the already finished partly foamed product. Again, one of the above calculation formulas can be used. The fully foamed layer can be provided by subsequent foaming of the partially foamed layer at a suitable temperature and for a suitable time. In place of the layer containing unexpanded microballoons, however, in the calculation formulas, in each case, those surface weight and formulation-identical layer which is defoamed by the destruction of the cavities of the partially foamed layer which are formed by the expanded microballoons occurs. In order to destroy the foamed microballoons of the partially foamed layer, the sample to be examined is pressed under vacuum. The parameters of the press are as follows: - Temperature: 150 ° C

- Contact pressure: 10 kN

Vacuum: 0.9 bar (i.e., 0.9 bar vacuum or 100 mbar residual pressure)

- pressing time: 90 s The degree of foaming of a fully expanded layer is accordingly 100%. For overexpanded layers, a negative degree of foaming is indicated. It is determined to what extent the increase in thickness or the density decrease, which takes place during the transition from the unexpanded to the fully expanded state, is lost or gained again by the subsequent overexpansion. The fact that the partially foamed self-adhesive composition according to the invention with a degree of foaming of 20 to less than 100% comparable or even - obviously depending on the selected degree of partial foaming - improved shock resistance than the corresponding fully expanded layers is particularly surprising in that the partially foamed system, the microballoons are foamed less than in the fully foamed system. The person skilled in the art would therefore have rather expected that the partially-foamed self-adhesive layers would have to have a lower shock resistance than the corresponding fully-foamed self-adhesive layers.

The pressure-sensitive adhesive strips according to the invention having at least one partially foamed self-adhesive with microballoons are typically storage-stable. This means according to the invention that the degree of partial foaming of the partially foamed self-adhesive composition (s) present in the pressure-sensitive adhesive strip increases by less than 5 relative percent at room temperature (20 ° C.) within 10 minutes, preferably by less than 1 relative percent.

Preferably, the pressure-sensitive adhesive strip consists of a single self-adhesive layer SK1, so that the pressure-sensitive adhesive strip constitutes a single-layer system. Such a single-layer, double-sided self-adhesive tape, i. double-sided adhesive tape, also referred to as "transfer tape".

The self-adhesive layer or self-adhesive layers of the pressure-sensitive adhesive strip according to the invention typically have a thickness of 10 to 2000 μm. In a preferred embodiment, they have a thickness of less than 75 μηη, more preferably less than 20 μηη, more preferably of at most 15 μηη, such as 10 μηη. In an alternative likewise preferred embodiment, the self-adhesive layers can also have a thickness of from 80 μm to 2000 μm, and in particular from 100 to 300 μm, such as, for example, 150 μm.

In a further preferred embodiment, in addition to a layer SK1, the pressure-sensitive adhesive strip also comprises a layer T of a (permanent) carrier, in particular a film carrier, wherein the layer SK1 is arranged on one of the surfaces of the carrier layer T. Such a pressure-sensitive adhesive strip constitutes a single-sided adhesive tape. Particularly preferably, the single-sided adhesive tape consists exclusively of the layer SK1 and the backing layer T. According to the present application, the terms "pressure-sensitive adhesive tape" and "adhesive tape" are used interchangeably.

The layer T from a carrier is synonymous in the context of this document simply referred to as a carrier or as a carrier layer.

In a particularly preferred embodiment, the pressure-sensitive adhesive strip moreover comprises a layer SK2 of a self-adhesive mass, which is arranged on the surface of the carrier layer T opposite the layer SK1. Preferably, the layer SK2 is based on a partially foamed mass with microballoons, the degree of foaming of the layer SK2 being at least 20% and less than 100%. Such a pressure-sensitive adhesive strip constitutes a double-sided adhesive tape. In particular, the double-sided adhesive tape consists exclusively of the layers SK1, SK2 and the carrier layer T.

In such a single-sided or double-sided adhesive tape, the (film) carrier layer preferably has a thickness of 5 to 150 μm. The film backing layer may be non-stretchable, preferably having a thickness of 5 to 125 μm, more preferably 5 to 40 μm, and more preferably less than 10 μm, such as 6 μm. Alternatively, the film backing layer can be stretchable, wherein the film backing layer preferably has a thickness of 50 to 150 μηη, more preferably 60 to 100 μηη and in particular from 70 μηη to 75 μηη, such as 70 μηη having.

A "non-stretchable film carrier" according to the invention means, in particular, a film carrier which has an elongation at break of less than 300%, preferably both in the longitudinal direction and in the transverse direction The non-expandable film carrier also has, preferably independently of one another both in the longitudinal direction and also in the transverse direction, preferably an elongation at break of less than 200%, more preferably less than 150%, even more preferably less than 100%, and most preferably less than 70%, such as less than 50% refer in each case to the measuring method R1 given below.

By "stretchable film carrier" is meant according to the invention in particular a film carrier which, preferably in both the longitudinal direction and in the transverse direction, a Elongation at break of at least 300%. The stretchable film carrier also has, preferably independently of one another both in the longitudinal direction and in the transverse direction, an elongation at break of at least 500%, for example of at least 800%. The values given refer to the measuring method R1 given further down.

The partial foaming makes it possible to produce pressure-sensitive adhesive strips whose microballoon-containing self-adhesive composition layers have extremely low thicknesses of in particular less than 20 μm, for example 10 to 15 μm. In such partially-foamed self-adhesive layers, the average diameter of the cavities formed by the microballoons is typically less than 20 μm, more preferably not more than 15 μm, such as 10 μm. The determination of the mean diameter of the cavities formed by the microballoons in a self-adhesive layer is based on cryogenic breaking edges of the pressure-sensitive adhesive strip in the scanning electron microscope (SEM) at 500 × magnification. The diameter of the microballoons of the self-adhesive composition layer to be examined is graphically determined from the micrographs of the PSA strip to be examined on SEM images, the arithmetic mean of all determined diameters being the mean diameter of the voids of the self-adhesive composition layer formed by the microballoons in the context of the present application represents. The diameters of the microballoons to be seen on the recordings are determined graphically in such a way that from the SEM images for each individual microballoon of the self-adhesive composition layer to be examined its maximum extent is taken in any (two-dimensional) direction and is regarded as its diameter. The use of such thin pressure-sensitive adhesive strips is of particular interest for bonding of such components and electronic devices in which only little space is available for bonding, in particular in mobile devices such as mobile phones.

The pressure-sensitive adhesive strip in the form of a single-sided adhesive tape thus preferably has a thickness of 15 to 2150 μm. The pressure-sensitive adhesive strip in the form of a double-sided adhesive tape with (permanent) carrier thus preferably has a thickness of 20 to 2300 μm.

In the present application, by "arrangement" of the layers SK1 or SK2 on the surfaces of the carrier layer T, an arrangement may be meant in which the Layers SK1 and / or SK2 are in direct contact with the surfaces of the carrier layer T, ie are arranged directly on the surface. Alternatively, this may also mean an arrangement in which at least one further layer is present between the layer SK1 and the one surface of the carrier layer T and / or between the layer SK2 and the surface SK of the carrier layer opposite the layer SK1. Preferably, in the pressure-sensitive adhesive strip according to the invention with carrier layer T, the layers SK1 and, if present, SK2 are in direct contact with one of the surfaces of the carrier layer T or with the surface of the carrier layer T opposite the layer SK1.

The outer areas of the pressure-sensitive adhesive strip which are accessible to adhesion are preferably formed by the partial-foamed self-adhesive compositions according to the invention having a degree of foaming of from 20% to less than 100%. As a result, the inventively found advantage of high shock resistance is particularly well realized. Of central importance for shock resistance is the partial foam present in the self-adhesive layers SK1 or SK2.

Accordingly, the single-sided adhesive tape according to the invention is preferably a pressure-sensitive adhesive strip consisting of the carrier layer T and the self-adhesive composition layer SK1, which is arranged on one of the surfaces of the carrier layer T. There, the outer surface of the pressure-sensitive adhesive strip which is accessible to the bond is formed by the partial-foamed self-adhesive composition layer SK1. Accordingly, the double-sided adhesive tape with carrier according to the invention is also preferably a pressure-sensitive adhesive strip consisting of the carrier layer T, partially foamed self-adhesive layer SK1 disposed on one of the surfaces of the carrier layer T and the self-adhesive layer SK2 facing the layer SK1 Surface of the carrier layer T is arranged. There, one of the two outer surfaces of the pressure-sensitive adhesive strip accessible to the bond is formed by the partial-foamed self-adhesive composition layer SK1. More preferably, the layer SK2 is also based on a partially foamed with microballoons mass with a degree of foaming of at least 20% and less than 100%. Adhesive adhesive strips having more than one layer of a self-adhesive composition according to the invention are preferably self-adhesive layers which are based on a composition partially foamed with microballoons, the degree of foaming of the layers being at least 20% and less than 100%. Such pressure-sensitive adhesive strips have particularly high shock resistance. Carrier-coated double-sided adhesive tapes according to the invention, in which both self-adhesive layers SK1 and SK2 are partially foamed with microballoons to a degree of foaming of at least 20% and less than 100%, accordingly exhibit particularly high shockresistance.

The self-adhesive mass layers SK1 and SK2 are also referred to as self-adhesive layers SK1 and SK2, simply as layers SK1 and SK2 or else as external layers, adhesive compositions or pressure-sensitive adhesive layers SK1 and SK2. The term "outboard" refers in particular to the preferably three-layer structure of the double-sided adhesive tape of the (permanent) carrier and partially foamed layers SK1 and SK2, without prejudice to any liners provided on the outer surfaces of the self-adhesive layers (see below) Foaming degree of the partially-foamed self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2 each independently, 25 to 98%, more preferably 35 to 95%, even more preferably 50 to 90% and especially 65 to 90%, such as 70 to 80% pressure-sensitive adhesive strips containing such partially foamed self-adhesive layers have particularly high shock resistance.

Preferably, the proportion of the microballoons in the partially foamed self-adhesive layers SK1 and / or SK2, preferably in both layers SK1 and SK2, each independently of one another, is up to 12 wt.%, Preferably 0.25 wt.% To 5 wt. more preferably 0.5 to 4% by weight, more preferably 0.8 to 3% by weight, in particular 1 to 2.5% by weight, for example 1 to 2% by weight, in each case based on the total composition the self-adhesive layer. In these areas, self-adhesive layers or pressure-sensitive adhesive strips comprising such self-adhesive layers can be provided, which have particularly good shock resistance. This typically results in partially foamed self-adhesive layers SK1 and / or SK2 having an absolute density of 400 to 990 kg / m ³ , preferably 500 to 900 kg / m ³ , more preferably 600 to 850 kg / m ³ and in particular 650 to 800 kg / m ³ , such as 700 to 800 kg / m ³ , and / or having a relative density of 0.35 to 0.99, preferably 0.45 to 0.90, and especially 0.50 to 0.85. The relative density describes the ratio of the density of the partially foamed self-adhesive composition to the density of the formulation-identical, unfoamed self-adhesive composition. In these areas, self-adhesive layers or pressure-sensitive adhesive strips comprising such self-adhesive layers can be provided, which have particularly good shock resistance.

In the double-sided adhesive tape with carrier, the self-adhesive composition layer SK 2 is preferably based on a mass partially foamed with microballoons, the degree of foaming of the layer SK 2 being at least 20% and less than 100%. In a particularly preferred embodiment of the pressure-sensitive adhesive strip, this has a symmetrical structure with regard to the composition of the layers, in that the partially foamed masses of the two self-adhesive layers SK1 and SK2 are chemically identical and advantageously also, if additives have been added to them, identical and identical Quantity are used. In particular, the pressure-sensitive adhesive strip has a completely symmetrical structure, that is to say both with respect to the chemical composition of the two partially foamed self-adhesive layers SK1 and SK2 (including their optionally present additives), as well as with respect to its structural configuration in which both surfaces of the carrier T are pretreated identically and the two Self-adhesive layers SK1 and SK2 have the same thickness and density. "Fully symmetrical" refers in particular to the z-direction ("thickness", direction perpendicular to the pressure-sensitive adhesive layer) of the pressure-sensitive adhesive strip, but of course also to the geometry in the plane of the surface (x and y directions, ie length and width of the pressure-sensitive adhesive strip) relate.

The double-sided adhesive tape with carrier preferably has a structure which is structurally symmetrical in the z-direction, in that the two self-adhesive layers SK1 and SK2 have the same thickness and / or the same density. According to the invention, a double-sided adhesive tape can be realized in which the self-adhesive layers SK1 and SK2 are the same thickness and / or have the same density, but are chemically different.

The following statements explicitly apply without exception also to the completely symmetrical embodiment variant of the double-sided adhesive tape according to the invention.

The self-adhesive masses of the layers SK1 and SK2 are each a PSA (pressure-sensitive adhesives). The terms "self-adhesive" and "pressure-sensitive adhesive" are used interchangeably in the context of this document.

Pressure-sensitive adhesives are, in particular, those polymeric compositions which are permanently tacky and tacky at the application temperature (unless otherwise defined, at room temperature, ie 20 ° C.), optionally by suitable addition with further components such as, for example, tackifier resins, and at a large number of surfaces upon contact Adhere, in particular immediately adhere (a so-called "Tack" [stickiness or Anfassklebrigkeit] exhibit.) They are able already at the application temperature without an activation by solvents or by heat - but usually by the influence of a more or less high pressure - To wet a substrate to be bonded sufficiently, so that between the mass and the substrate for the adhesion sufficient interactions can form.For this influence parameters include the pressure and the contact time Among other things, the particular properties of the PSAs are e back to their viscoelastic properties. Thus, for example, weakly or strongly adhering adhesives can be produced; furthermore, those which can be glued only once and permanently, so that the bond can not be released without destroying the adhesive and / or the substrates, or those which are easily removable and, if necessary, can be glued several times. Pressure-sensitive adhesives can in principle be produced on the basis of polymers of different chemical nature. The pressure-sensitive adhesive properties are influenced inter alia by the nature and the proportions of the monomers used in the polymerization of the polymers on which the PSA is based, their average molecular weight and molecular weight distribution, and by the nature and amount of the PSA additives, such as tackifier resins, plasticizers and the like. To achieve the viscoelastic properties, the monomers on which the PSA-based polymers are based, as well as the optional further components of the PSA, are chosen such that the PSA has a glass transition temperature (according to DIN 53765) below the application temperature (ie usually below room temperature , ie 20 ° C).

Optionally, it may be advantageous to increase and / or shift the temperature range in which a polymer composition has tack-adhesive properties by suitable cohesion-increasing measures, such as crosslinking reactions (formation of bridge-forming linkages between the macromolecules). The scope of the PSAs can thus be optimized by adjusting the flowability and cohesion of the mass. A PSA is permanently tacky at room temperature (20 ° C), so it has a sufficiently low viscosity and a high tack, so that it wets the surface of the respective Klebegrunds already at low pressure. The adhesiveness of the adhesive is based on its adhesive properties and the removability on their cohesive properties.

In a preferred embodiment, the pressure-sensitive adhesive strip can be detached again by stretching stretching essentially in the bonding plane without residue or destruction. The term "residue-free detachment" of the pressure-sensitive adhesive strip, according to the invention, means that it leaves no adhesive residue on the bonded surfaces of the components.Furthermore, "non-destructive peeling" of the pressure-sensitive adhesive strip means according to the invention that it does not damage the bonded surfaces of the components during detachment, for example destroyed.

So that pressure-sensitive adhesive strips can be detached again without residue and without destruction by stretching in the bonding plane, they must possess certain adhesive properties. For example, when sticking, the stickiness of the pressure-sensitive adhesive strips must drop markedly. The lower the adhesive power in the stretched state, the less strongly the substrate is damaged during detachment, or the less pronounced there is the danger that residues will remain on the bonding substrate. This property is particularly evident in the case of PSAs based on Vinyl aromatic block copolymers, in which near the yield point, the tackiness drops below 10%.

So that pressure-sensitive adhesive strips can be removed again easily by stretched stretching and residue-free, they must also possess certain mechanical properties in addition to the adhesive properties described above. Particularly advantageous is the ratio of the tensile strength (tear strength) and the stripping force greater than two, preferably greater than three. The stripping force is the force that has to be expended in order to redetach a pressure-sensitive adhesive strip from an adhesive joint by stretching in the bonding plane. This stripping force is composed of the force needed to peel off the pressure-sensitive adhesive tape from the bonding substrates as described above and the force that must be expended to deform the pressure-sensitive adhesive tape. The force required to deform the pressure-sensitive adhesive strip depends on the thickness of the pressure-sensitive adhesive strip. In contrast, the force required for detachment is independent of the thickness of the pressure-sensitive adhesive strip in the considered thickness range of the pressure-sensitive adhesive strip.

If in the following statements on preferred embodiments of the invention of a "self-adhesive layer" or "Selbstklebemasseschichten" or one is spoken, this may refer to the layer SK1, on the layer SK2 or on both layers, unless expressly stated otherwise ,

Self-Adhesive Layers that Can be Used According to the Invention The layer SK1 of the pressure-sensitive adhesive strip according to the invention is based on a self-adhesive mass partially foamed with microballoons. The layer SK2 of the pressure-sensitive adhesive strip according to the invention in the form of a double-sided adhesive tape with carrier is likewise based on a self-adhesive composition, which is preferably partially foamed with microballoons. The pressure-sensitive adhesive layers contained in the pressure-sensitive adhesive strips according to the invention can be based on various polymer compositions, usually together with tackifier resin. Based on a polymer or a particular polymer composition in this sense typically means that the said polymer predominantly takes over the function of the elastomer component. Preferably, said polymer is solely as Elastomer component provided or at least to at least 50 wt .-% based on the total amount of all elastomer components.

Preferably, they are based on chemically or physically crosslinked synthetic rubber compounds, such as vinyl aromatic block copolymer compositions. Synthetic rubbers typically have high tack (due to the tackifier resins), very good adhesion to polar and nonpolar substrates such as polypropylene and polyethylene and are suitable for a wide range of applications.

Likewise, the pressure-sensitive adhesive layers may preferably be based on acrylate compounds. Typically, these are transparent, highly resistant to aging, temperature, UV radiation, ozone, moisture, solvents or plasticizers and have a very good bond strength to polar substrates.

Also possible are pressure-sensitive adhesive layers based on natural rubber compounds. These are typically characterized by a high tackiness (by the adhesive resins), a very good bond strength on polar and on non-polar substrates and a residue-free removability.

(a) Self-adhesive layers based on a vinyl aromatic block copolymer mass

The layers SK1 and / or SK2 may be based on vinyl aromatic block copolymer compositions.

At least one synthetic rubber in the form of a block copolymer having a structure AB, ABA, (AB) _n , (AB) _n X or (ABA) _n X is preferably used in the layer SK1 and / or in the layer SK2 as the vinylaromatic block copolymer, in which

the blocks A independently represent a polymer formed by

Polymerization of at least one vinyl aromatic,

the blocks B independently of one another for a polymer formed by polymerization of conjugated dienes having 4 to 18 C atoms, or for a partially hydrogenated derivative of such a polymer, X for the remainder of a coupling reagent or initiator and

n stand for an integer> 2.

Particularly preferred are all synthetic rubbers of the self-adhesive composition layer of the invention block copolymers having a structure AB, ABA, (AB) _n , (AB) _n X or (ABA) _n X as set forth above. The self-adhesive composition layer according to the invention can thus also contain mixtures of different block copolymers having a structure as described above.

Suitable block copolymers (vinylaromatic block copolymers) thus comprise one or more rubbery blocks B (soft blocks) and one or more glassy blocks A (hard blocks). More preferably, at least one synthetic rubber of the self-adhesive composition of the invention is a block copolymer having a structure AB, ABA, (AB) ₂ X, (AB) ₃ X or (AB) ₄ X, where A, B and X are as defined above. Very particularly preferably all synthetic rubbers the self-adhesive layer according to the invention block copolymers having a structure AB, ABA, (AB) 2X are (AB) sX or (AB) ₄ X, where apply for A, B and X have the above meanings. In particular, the synthetic rubber of the self-adhesive composition according to the invention is a mixture of block copolymers having a structure AB, ABA, (AB) ₂ X, (AB) ₃ X or (AB) ₄ X, preferably at least diblock copolymers AB and / or triblock copolymers ABA and / or ( AB) ₂ X contains.

Also advantageous is a mixture of diblock and triblock copolymers and (AB) _n or (AB) nX block copolymers with n greater than or equal to 3. Further advantageous is a mixture of diblock and multiblock copolymers and (AB) _n - or (AB) nX Block copolymers with n greater than or equal to 3.

Thus, for example, diblock copolymers AB in combination with other of the abovementioned block copolymers can be used as vinylaromatic block copolymers. About the proportion of Diblockcopolymeren the Auffließverhalten the self-adhesive compositions and their bond strength can be adjusted. Vinyl aromatic block copolymer used in the present invention preferably has a diblock copolymer content of from 0% to 70%, and more preferably from 15% to 50% by weight. A higher proportion of diblock copolymer in vinylaromatic block copolymer leads to a significant reduction in the cohesion of the adhesive. Preferred self-adhesives are those based on block copolymers comprising polymer blocks (i) predominantly formed from vinylaromatics (A blocks), preferably styrene, and at the same time (ii) those predominantly formed by polymerization of 1,3-dienes (B blocks), such as for example butadiene and isoprene or a copolymer of both, application.

Particular preference is given to self-adhesives according to the invention being based on styrene block copolymers, for example the block copolymers of the self-adhesive compositions have polystyrene endblocks.

The block copolymers resulting from the A and B blocks may contain the same or different B blocks. The block copolymers may have linear A-B-A structures. It is also possible to use block copolymers of radial form as well as star-shaped and linear multiblock copolymers. As further components, A-B diblock copolymers may be present. All of the aforementioned polymers may be used alone or in admixture with each other.

In a vinylaromatic block copolymer used according to the invention, in particular a styrene block copolymer, the proportion of polyvinylaromatics, in particular polystyrene, is preferably at least 12% by weight, more preferably at least 18% by weight and more preferably at least 25% by weight and also preferably at most 45 % By weight and more preferably at most 35% by weight.

Instead of the preferred polystyrene blocks can also be used as vinyl aromatic polymer blocks based on other aromatic homo- and copolymers (preferably Cs to C12 aromatics) with glass transition temperatures of greater than 75 ° C as for example omethylstyrolhaltige aromatic blocks. Furthermore, the same or different A blocks may be included. The vinylaromatics for the construction of the block A preferably comprise styrene, methyl styrene and / or other styrene derivatives. The block A can thus be present as a homo- or copolymer. More preferably, block A is a polystyrene.

Preferred conjugated dienes as monomers for the soft block B are in particular selected from the group consisting of butadiene, isoprene, ethyl butadiene, Phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene and dimethyl butadiene and any mixtures of these monomers. Block B can also be present as a homopolymer or as a copolymer. The conjugated dienes are particularly preferred as monomers for the soft block B selected from butadiene and isoprene. For example, the soft block B is a polyisoprene, a polybutadiene or a partially hydrogenated derivative of one of these two polymers such as in particular polybutylene butadiene, or a polymer of a mixture of butadiene and isoprene. Most preferably, the block B is a polybutadiene.

In the context of this invention, A blocks are also referred to as "hard blocks." B blocks are also called "soft blocks" or "elastomer blocks." This mirrors the inventive selection of the blocks according to their glass transition temperatures (for A blocks at least 25 ° C.). in particular at least 50 ° C and for B blocks at most 25 ° C, in particular at most -25 ° C).

The proportion of vinylaromatic block copolymers, in particular styrene block copolymers, is preferably in total, based on the total self-adhesive composition layer, at least 20% by weight, preferably at least 30% by weight, more preferably at least 35% by weight. Too low a proportion of vinylaromatic block copolymers has the consequence that the cohesion of the PSA is relatively low.

The maximum proportion of vinylaromatic block copolymers, in particular styrene block copolymers, in total, based on the total self-adhesive composition, is at most 75% by weight, preferably at most 65% by weight, very particularly preferably at most 55% by weight. Too high a proportion of vinylaromatic block copolymers, in turn, has the consequence that the PSA is barely tacky.

Accordingly, the proportion of the vinylaromatic block copolymers, in particular styrene block copolymers, in total based on the total self-adhesive composition is preferably at least 20% by weight, more preferably at least 30% by weight, more preferably at least 35% by weight and at the same time at most 75% by weight. , more preferably at most 65% by weight, most preferably at most 55% by weight. The pressure-sensitive adhesiveness of the self-adhesive compositions can be achieved by adding adhesive resins which are miscible with the elastomer phase. The self-adhesive compositions generally have, in addition to the at least one vinylaromatic block copolymer, at least one adhesive resin in order to increase the adhesion in the desired manner. The adhesive resin should be compatible with the elastomeric block of the block copolymers.

An "adhesive resin" (tackifier) is understood, according to the general expert understanding, to be a low molecular weight, oligomeric or polymeric resin which increases the adhesion (tack, inherent tack) of the pressure-sensitive adhesive in comparison with the otherwise non-adhesive-containing, otherwise identical pressure-sensitive adhesive.

If adhesive resin is contained in the self-adhesive compositions, preferably at least 75% by weight, based on the total resin content, of a resin having a DACP (diacetone alcohol cloud point) of greater than 0 ° C., preferably greater than 10 ° C., of an MMAP ( mixed methylcyclohexane aniline point) of at least 50 ° C, preferably of at least 60 ° C, and / or a softening temperature (Ring & Ball) greater than or equal to 70 ° C, preferably greater than or equal to 100 ° C. Particularly preferably, said adhesive resin simultaneously has a DACP value of less than 50 ° C., if there are no isoprene blocks in the elastomer phase, or of less than 65 ° C., if isoprene blocks are present in the elastomer phase. Likewise, particularly preferably, said adhesive resin simultaneously has an MMAP value of at most 90 ° C., if no isoprene blocks are present in the elastomer phase, or of at most 100 ° C., provided isoprene blocks are present in the elastomer phase. Likewise particularly preferably, the softening temperature of said adhesive resin is up to 150 ° C.

The adhesive resins are particularly preferably hydrocarbon resins or terpene resins or a mixture of the like, in particular at least 75% by weight, based on the total resin content. In particular, nonpolar hydrocarbon resins, for example hydrogenated and nonhydrogenated polymers of dicyclopentadiene, nonhydrogenated, partially, selectively or completely hydrogenated hydrocarbon resins based on Cs, C5 / C9 or Cg have been found to be tackifiers for the PSA (s). Monomer streams, polyterpene resins based on α-pinene and / or β-pinene and / or δ-limonene can be used advantageously. The aforementioned adhesive resins can be used alone as well as in the Mixture be used. Both solid and liquid resins can be used at room temperature (20 ° C.). Adhesive resins, hydrogenated or non-hydrogenated, which also contain oxygen, may optionally be used preferably up to a maximum proportion of 25% based on the total mass of the resins in the adhesive, such as rosin and / or rosin ester resins and / or terpene phenolic resins.

The proportion of liquid at room temperature (20 ° C) optionally usable liquid resins or plasticizers is according to a preferred variant up to 15 wt .-%, preferably up to 10 wt .-% based on the total self-adhesive.

In a preferred embodiment, in the self-adhesive layers 20 to 60 wt .-% of at least one adhesive resin, based on the total weight of the self-adhesive composition, preferably 30 to 50 wt .-% of at least one adhesive resin, based on the total weight of the self-adhesive composition included.

As further additives can typically be used:

Plasticizers such as plasticizer oils, or low molecular weight liquid polymers such as low molecular weight polybutenes,

preferably with a proportion of 0.2 to 5 wt .-% based on the total weight of the self-adhesive

primary antioxidants such as hindered phenols,

preferably in a proportion of 0.2 to 1 wt .-% based on the total weight of the self-adhesive

Secondary antioxidants, such as phosphites, thioesters or thioethers, preferably in a proportion of 0.2 to 1 wt .-% based on the total weight of the self-adhesive

Process stabilizers such as C radical scavengers,

Light stabilizers, for example UV absorbers or sterically hindered amines, preferably in an amount of from 0.2 to 1% by weight, based on the total weight of the self-adhesive composition

Processing aids,

preferably in a proportion of 0.2 to 1 wt .-% based on the total weight of the self-adhesive endblock reinforcer resins,

preferably in a proportion of 0.2 to 10 wt .-% based on the total weight of the self-adhesive and

optionally further polymers of preferably elastomeric nature; correspondingly useful elastomers include, but are not limited to those based on pure hydrocarbons, for example, unsaturated polydienes such as natural or synthetically produced polyisoprene or polybutadiene, chemically substantially saturated elastomers such as saturated ethylene-propylene copolymers, α-olefin copolymers, polyisobutylene, butyl rubber, ethylene Propylene rubber, as well as chemically functionalized hydrocarbons such as halogen-containing, acrylate-containing, allyl or vinyl ether-containing polyolefins,

preferably with a proportion of 0.2 to 10 wt .-% based on the total weight of the self-adhesive. The type and amount of the blending components can be selected as needed. It is also according to the invention if the adhesive does not have some, preferably all, of the additives mentioned above.

In one embodiment of the present invention, the self-adhesive also contains other additives, by way of example but not by way of limitation, crystalline or amorphous oxides, hydroxides, carbonates, nitrides, halides, carbides or mixed oxide / hydroxide / halide compounds of aluminum, silicon, zirconium, Titanium, tin, zinc, iron or the (alkaline) alkali metals. These are essentially clays such as aluminas, boehmite, bayerite, gibbsite, diaspore and the like. Particularly suitable are layered silicates such as bentonite, montmorillonite, hydrotalcite, hectorite, kaolinite, boehmite, mica, vermiculite or mixtures thereof. But also carbon blacks or other modifications of the carbon, such as carbon nanotubes, can be used. The adhesives may also be colored with dyes or pigments. The adhesives may be white, black or colored.

As plasticizers, for example mineral oils, (meth) acrylate oligomers, phthalates, cyclohexanedicarboxylic acid esters, water-soluble plasticizers, soft resins, phosphates or polyphosphates can be added. The addition of silicic acids, advantageously precipitated silica modified with dimethyldichlorosilane, can be used to further increase the thermal resistance of the self-adhesive composition.

According to a preferred embodiment of the invention, the adhesive consists only of vinylaromatic block copolymers, tackifier resins, microballoons and optionally the above-mentioned additives.

With further preference the adhesive consists of the following composition:

Vinylaromatic block copolymers 20 to 75% by weight

Adhesive resins 24.6 to 60% by weight

Microballoons 0.2 to 10% by weight

Additives 0.2 to 10% by weight

With further preference the adhesive consists of the following composition

Vinylaromatic block copolymers 35 to 65% by weight

Adhesive resins 34.6 to 45% by weight

Microballoons 0.2 to 10% by weight

Additives 0.2 to 10% by weight

With further preference the adhesive consists of the following composition:

Vinylaromatic block copolymers 30 to 75% by weight

Adhesive resins 24.8 to 60% by weight

Microballoons 0.2 to 10% by weight

The self-adhesive composition SK1 according to the invention is partly foamed with microballoons, and also the self-adhesive composition SK2 according to the invention is preferably partly foamed with microballoons. The partial foaming typically takes place in each case by the introduction and subsequent expansion of microballoons.

The term "microballoons" is understood as meaning elastic hollow microspheres which are expandable in their ground state and which have a thermoplastic polymer shell These spheres are filled with low-boiling liquids or liquefied gas Hydrocarbons of lower alkanes, for example isobutane or isopentane, which are enclosed as liquefied gas under pressure in the polymer shell.

By acting on the microballoons, in particular by a heat, softens the outer polymer shell. At the same time, the liquid propellant gas in the casing changes into its gaseous state. The microballoons expand irreversibly and expand in three dimensions. A Vollexpansion is achieved when the internal and the external pressure equalize. According to the invention, the expansion is previously stopped by cooling or cooling to give a degree of foaming of at least 20% to less than 100%. As the polymeric shell is retained, a closed-cell foam is obtained.

A variety of unexpanded types of microballoons are commercially available which differ substantially in their size and starting temperatures (75 to 220 ° C) needed for expansion. An example of commercially available unexpanded microballoons are the Expancel® DU (dry unexpanded) grades from Akzo Nobel. In the type designation Expancel xxx DU yy (Dry unexpended), "xxx" stands for the composition of the microballoon mixture, and "yy" for the size of the microballoons in the expanded state.

Unexpanded microballoon types are also available as an aqueous dispersion having a solids or microballon content of about 40 to 45 wt%, and also as polymer bound microballoons (masterbatches), for example, in ethylvinyl acetate having a microballoon concentration of about 65 wt%. Both the microballoon dispersions and the masterbatches, like the DU types, are suitable for producing a foamed self-adhesive composition according to the invention.

A partially-foamed self-adhesive SK1 and / or SK2 of the invention may also be pre-expanded to the desired degree, i. partially expanded, microballoons are generated. In this group, the part expansion takes place even before the mixing into the polymer matrix.

In the processing of already partially expanded microballoon types, it may happen that the microballoons, due to their low density in the polymer matrix into which they are to be incorporated, tend to flotate, ie in the polymer matrix during the This results in an uneven distribution of the microballoons in the layer, more microballoons are found in the upper region of the layer (z-direction) than in the lower region of the layer, so that a density gradient is established across the layer thickness.

To prevent such a density gradient largely or almost completely, according to the invention preferably no or only slightly pre-expanded microballoons are incorporated into the polymer matrix of the layer SK1 or the layer SK2 or preferably both layers SK1 and SK2. Only after incorporation into the layer are the microballoons expanded to the desired degree of foaming. This results in a more uniform distribution of the microballoons in the polymer matrix.

Preferably, the microballoons are chosen such that the ratio of the density of the polymer matrix to the density of the (non-or only slightly pre-expanded) microballoons to be incorporated into the polymer matrix is between 1 and 1: 6. Only after or immediately after incorporation is the part expansion then carried out. In the case of solvent-containing compositions, the microballoons are preferably expanded only after incorporation, coating, drying (solvent evaporation). DU types are therefore preferably used according to the invention.

If partially foamed by means of microballoons, then the microballoons can be supplied as a batch, paste or as uncut or blended powder of the formulation. Furthermore, they may be suspended in solvent. A self-adhesive composition SK1 or SK2 containing expandable hollow microspheres according to the invention may additionally contain non-expandable hollow microspheres. The decisive factor is that almost all gas-containing caverns are closed by a permanently dense membrane, regardless of whether this membrane consists of an elastic and thermoplastic polymer mixture or about elastic and - in the range of possible in plastics processing temperatures - non-thermoplastic glass.

(b) Self-adhesive Compositions Based on an Acrylic Compound In a further preferred embodiment, the self-adhesive composition layers SK1 and / or SK2, preferably both layers SK1 and SK2, are based on an acrylate composition. In one embodiment, self-adhesive compositions of (meth) acrylic acid and esters thereof having 1 to 25 carbon atoms, maleic, fumaric and / or itaconic acid and / or their esters, substituted (meth) acrylamides, maleic anhydride and other vinyl compounds such as vinyl esters , in particular vinyl acetate, vinyl alcohols and / or vinyl ethers used. The residual solvent content should be below 1% by weight.

Another preferred embodiment is a pressure-sensitive adhesive which contains a polyacrylate polymer. This is a polymer which is obtainable by radical polymerization of acrylic monomers, which are also understood to mean methylacrylic monomers, and optionally other copolymerizable monomers.

According to the invention, it may be a polyacrylate crosslinkable with epoxide groups. Accordingly, as monomers or comonomers it is preferred to use functional monomers crosslinkable with epoxide groups; in particular monomers having acid groups (especially carboxylic acid, sulfonic acid or phosphonic acid groups) and / or hydroxyl groups and / or acid anhydride groups and / or epoxide groups and / or amine groups are used; preferred are carboxylic acid group-containing monomers. It is particularly advantageous if the polyacrylate has copolymerized acrylic acid and / or methacrylic acid.

Further monomers which can be used as comonomers for the polyacrylate are, for example, acrylic acid and / or methacrylic acid esters having up to 30 carbon atoms, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures of these monomers. Preferably, a polyacrylate is used to form the acrylate composition of the self-adhesive layers which can be attributed to the following monomer composition:

(i) acrylic acid (ester) and / or methacrylic acid (ester) of the following formula

CH ₂ = C (R ¹ ) (COOR ² ) where R ^{1 is} H or CH 3 and R ^{2 is} H or linear, branched or cyclic, saturated or unsaturated alkyl radicals having 1 to 30, in particular 4 to 18, carbon atoms,

(ii) optionally olefinically unsaturated comonomers having functional groups which cause crosslinkability with epoxide groups,

(iii) optionally further acrylates and / or methacrylates and / or olefinically unsaturated monomers which are copolymerizable with component (i).

Preferably, (i) is acrylic acid ester and / or methacrylic acid ester of the formula mentioned.

Further preferably, the proportions of the corresponding components (i), (ii), and (iii) are selected such that the polymerization product in particular has a glass transition temperature of less than or equal to 15 ° C for use of the polyacrylate.

It is very advantageous for the preparation of pressure-sensitive adhesives, the monomers of component (i) in a proportion of 45 to 99 wt .-%, the monomers of component (ii) in a proportion of 1 to 15 wt .-% and the monomers of Component (iii) in an amount of 0 to 40 wt .-% to choose (the data are based on the monomer mixture for the "base polymer", ie without additives of any additives to the finished polymer, such as resins).

The monomers of component (i) are especially plasticizing and / or nonpolar monomers. For the monomers (i), preference is given to using acrylic monomers which comprise acrylic and methacrylic acid esters having alkyl groups consisting of 4 to 18 C atoms, preferably 4 to 9 C atoms. Examples of such monomers are n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate , Isooctylmethacrylat and their branched isomers such as 2-ethylhexyl acrylate or 2-ethylhexyl methacrylate.

Preference is given to using for the component (ii) monomers having such functional groups selected from the following list: hydroxy, carboxy, sulfonic or phosphonic acid groups, acid anhydrides, epoxides, amines. Particularly preferred examples of monomers of component (ii) are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, itaconic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate,

6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate.

Exemplary monomers for component (iii) are: methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butyl acrylate, tert. Butylacrylate, phenylacrylate, phenylmethacrylate, isobornylacrylate, isobornylmethacrylate, t-butylphenylacrylate, t-butylaphenylmethacrylate, dodecylmethacrylate, isodecylacrylate, laurylacrylate, n-undecylacrylate, stearylacrylate, tridecylacrylate, behenylacrylate, cyclohexylmethacrylate, cyclopentylmethacrylate, phenoxyethylacrlylate Butoxyethyl acrylate, 3,3,5-trimethylcyclohexylacrylate, 3,5-dimethyladamantylacrylate, 4-cumylphenylmethacrylate, cyanoethylacrylate, cyanoethylmethacrylate, 4-biphenylacrylate, 4-biphenylmethacrylate, 2-naphthylacrylate, 2-naphthylmethacrylate, tetrahydrofuran I-acrylate, Diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, 3-methoxyacrylic acid methyl ester, 3-methoxybutyl acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycol methacrylate, ethylene glycol acrylate, ethylene nglycolmonomethyl acrylate, methoxy polyethylene glycol methacrylate 350, methoxy polyethylene glycol methacrylate 500, propylene glycol monomethacrylate, butoxy diethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,3,3-hexafluoroisopropyl acrylate, 1, 1, 1, 3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3, 3,4,4, 4-heptafluorobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8, 8-pentadecafluorooctyl methacrylate, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N- (1-methyl-undecyl) acrylamide, N- (n-butoxymethyl) acrylamide, N- (butoxymethyl) methacrylamide, N (ethoxymethyl) acrylamide, N- (n-octadecyl) acrylamide, furthermore Ν, Ν-dialkyl-substituted amides such as Ν, Ν-dimethylacrylamide, N, N-dimethylmethacrylamide, N benzylacrylamides, N isopropylacrylamide, N-tert. Butylacrylamide, N-tert. Octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, acrylonitrile, methacrylonitrile, vinyl ethers such as vinyl methyl ether, ethyl vinyl ether, vinyl isobutyl ether, Vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4- n-decylstyrene, 3,4-dimethoxystyrene, macromonomers such as 2-polystyrene ethyl methacrylate and poly (methyl methacrylate) ethyl methacrylate.

Monomers of component (iii) may advantageously also be chosen such that they contain functional groups which promote a subsequent radiation-chemical crosslinking (for example by electron beams, UV). Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers that promote electron beam crosslinking, for example, tetrahydrofurfuryl acrylate, N-tert-butylacrylamide, allyl acrylate, but this list is not exhaustive. Furthermore, the pressure-sensitive adhesive may contain crosslinking agents, in particular based on epoxide. In particular, multifunctional epoxides are used as substances containing epoxide groups, ie those which have at least two epoxide units per molecule (ie are at least bifunctional). These may be both aromatic and aliphatic compounds. Epoxy-based crosslinkers can also be used in oligomeric or polymeric form.

The mixture of acrylates may in turn preferably have the following composition: (I) 90 to 99% by weight of n-butyl acrylate and / or 2-ethylhexyl acrylate

(II) 1 to 10% by weight of an ethylenically unsaturated monomer having an acid or acid anhydride function,

wherein preferably (I) and (II) add up to 100 wt .-%. Preferably, the monomer (I) forms a mixture of 2-ethylhexyl acrylate and n-butyl acrylate, more preferably in equal parts.

Suitable monomers (II) are, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and / or maleic anhydride. Preference is given to acrylic acid or methacrylic acid, if appropriate the mixture of the two. To achieve tacky properties, the adhesive should be at its processing temperature above its glass transition temperature to have viscoelastic properties. The glass transition temperature of the pressure-sensitive adhesive composition (polymer tackifier mixture) is therefore preferably below +15 ° C.

Due to the possible addition of tackifiers, the glass transition temperature inevitably increases by about 5 to 40 K, depending on the amount added, compatibility and softening temperature. Acrylate copolymers with a glass transition temperature of at most 0 ° C. are therefore preferred.

Likewise, the pressure-sensitive adhesives preferably comprise at least the following two components:

(P) a first polyacrylate-based polymer component, i. Polyacrylate component, and (E) a second elastomeric-based polymer component substantially immiscible with the polyacrylate component, i. Elastomer component, which is preferably formed by one or more synthetic rubbers or comprises one or more synthetic rubbers. The polyacrylate-based polymer component (P) is preferably contained in a proportion of 60% by weight to 90% by weight, more preferably 65% by weight to 85% by weight, and the elastomer-based polymer component (E) is preferably contained in one portion from 10% to 40%, more preferably 15% to 35%, by weight of the total (100%) of the two components (P) and (E). The overall composition of the adhesive may be limited in particular to these two components, but other components such as additives and the like may also be added.

The second polymer component (elastomer component (E)) according to the invention with the first polymer component (polyacrylate component (P)) is substantially immiscible, so that the adhesive is present in the adhesive layer in at least two separate phases. In particular, one phase forms a matrix and the other phase a plurality of domains arranged in the matrix.

Homogeneous mixtures are substances mixed at the molecular level, homogeneous systems accordingly single-phase systems. The underlying substances are under Accordingly, two or more components are synonymously "non-homogeneously miscible", "incompatible" and "incompatible" if, after intimate blending, they are not "synonymously miscible", "compatible" and "compatible" homogeneous system, but at least two phases form. As a synonym "partially homogeneously miscible", "partially compatible", "partially compatible" and "partially compatible" are considered components which intimately mixed together (for example by shearing, in the melt or in solution and then eliminating the solvent) at least two Forming phases that are rich in each of the components, but one or both of the phases may each have a more or less large part of the other components homogeneously mixed.

The polyacrylate component (P) is preferably a homogeneous phase. The elastomer component (E) may be homogeneous in itself, or may have in itself a multiphase, as is known from microphase-segregating block copolymers. Polyacrylate and elastomer component are presently chosen so that they are - after intimate mixing - at 20 ° C (ie the usual application temperature for adhesives) are substantially immiscible. "Substantially immiscible" means that the components are either not homogeneously miscible with each other, so that none of the phases has a portion of the second component mixed homogeneously, or that the components are only partially compatible - so that one or both components only that the partial compatibility is insignificant for the invention, that is, the teaching according to the invention is not detrimental, the corresponding components being in the sense of this document then as "essentially free" of the respective other component considered.

Accordingly, the adhesive used according to the invention is present at least at room temperature (20 ° C.) in at least two-phase morphology. Most preferably, the polyacrylate component (P) and the elastomer component (E) are substantially non-homogeneously miscible in a temperature range of from 0 ° C to 50 ° C, more preferably from -30 ° C to 80 ° C.

For the purposes of this document, components are defined as "essentially immiscible with one another" in particular if the formation of at least two more resistant ones Physically and / or chemically detect phases, wherein the one phase rich in one component - the polyacrylate component (P) - and the second phase rich in the other component - the elastomer component (E) - is. A suitable analysis system for a phase separation is, for example, scanning electron microscopy. However, phase separation can also be recognized, for example, by the fact that the different phases have two mutually independent glass transition temperatures. Phase separation according to the invention is present if it can be clearly demonstrated by at least one of the analytical methods. In particular, the phase separation may be implemented such that there are discrete regions ("domains") rich in one component (formed essentially from one component and free from the other component) in a continuous matrix rich in the other Component is composed (essentially of the other component and free of the first component).

The phase separation for the adhesives used according to the invention takes place in particular such that the elastomer component (E) is dispersed in a continuous matrix of the polyacrylate component (P). The regions (domains) formed by the elastomer component (E) are preferably substantially spherical in shape. The regions (domains) formed by the elastomer component (E) can also deviate from the spherical shape, in particular distorted, such as, for example, elongated and oriented in the coating direction. The size of the elastomer domains is in its greatest extent typically - but not necessarily - between 0.5 μηη and 150 μηη, in particular between 1 μηη and 30 μηη. Other domain shapes are also possible, such as layered or rod-shaped, although these may differ in shape from ideal structures and may be bent or distorted, for example.

The polyacrylate component (P) and the elastomer component (E) each consist of a base polymer component, which may be a homopolymer, a copolymer or a mixture of polymers (homopolymers and / or copolymers), and optionally additives (co-components, additives). For the sake of simplicity, the base polymer component will be referred to below as the "base polymer" without it being intended to exclude polymer blends for the respective base polymer component, and accordingly the term "polyacrylate base polymer" will refer to the base polymer component of the polyacrylate component and "elastomer base polymer" means the base polymer component of the elastomer component of the adhesive.

The polyacrylate component (P) and / or the elastomer component (E) can each be present as 100% systems, that is based exclusively on their respective base polymer component and without further admixture of resins, additives or the like. In a further preferred manner, one or both of these two components are mixed with other components in addition to the base polymer component, such as, for example, resins.

In an advantageous embodiment of the invention, the polyacrylate component (P) and the elastomer component (E) are composed exclusively of their respective base polymer component, so that no further polymeric components are present, in particular no resins are present. In a further development, the entire adhesive, apart from the two base polymer components, comprises no further constituents.

The polyacrylate-based adhesive or the polyacrylate component (P) are in particular advantageously mixed with one or more crosslinkers for chemical and / or physical crosslinking. Since, in principle, radiation-crosslinking of the polyacrylate component (P) is also possible, however, crosslinkers are not necessarily present.

Crosslinkers are those - especially bifunctional or polyfunctional, usually low molecular weight compounds - which can react under the chosen crosslinking conditions with suitable - especially functional - groups of the polymers to be crosslinked, thus two or more polymers or polymer sites link together ("bridges" form) and The degree of crosslinking depends on the number of bridges formed, In principle, all crosslinking systems known to the person skilled in the art are suitable crosslinkers for the purpose of the present invention in particular covalent, coordinative or associative bonding systems with appropriately equipped (meth) acrylate monomers, depending on the nature of the selected polymers and their functional groups Examples of chemical crosslinking systems are di- or polyfunctional isocyanates or di- or multi-functional epoxides or di- or polyfunctional hydroxides or di- or multi-functional amines or di- or polyfunctional acid anhydrides. Combinations of different crosslinkers are also conceivable.

Further suitable crosslinkers include chelate formers which, in combination with acid functionalities in polymer chains, form complexes which act as crosslinking points.

For effective crosslinking, it is particularly advantageous if at least some of the polyacrylates have functional groups with which the respective crosslinkers can react. Preference is given to using monomers having functional groups which are selected from the group comprising: hydroxyl, carboxy, sulfonic or phosphonic acid groups, acid anhydrides, epoxides, amines.

Particularly preferred examples of monomers for polyacrylates are acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, B-hydroxyhexyl methacrylate, allyl alcohol, Glycidyl acrylate, glycidyl methacrylate.

It has proved to be particularly advantageous, as a crosslinker, 0.03 to 0.2 parts by weight, in particular 0.04 to 0.15 parts by weight of N, N, N ', N'-tetrakis (2,3-epoxypropyl) -m-xylene -a, α'-diamine (tetraglycidyl-meta-xylenediamine; CAS 63738-22-7) based on 100 parts by weight of polyacrylate base polymer.

Alternatively or additionally, it may be advantageous to cross-link the adhesive by radiation chemistry. Ultraviolet light (especially if the formulation contains suitable photoinitiators or at least one polymer in the acrylate component contains comonomers with units of photoinitizing functionality) and / or electron beams are suitable for this purpose.

For the radiation-induced crosslinking, it may be advantageous if some of the monomers used contain functional groups which promote a subsequent radiation-chemical crosslinking. Suitable copolymerizable photoinitiators are, for example, benzoin acrylate and acrylate-functionalized Benzophenone derivatives. Monomers which promote electron beam crosslinking are, for example, tetrahydrofurfuryl acrylate, N-tert-butylacrylamide and allyl acrylate. Reference is made in particular to the relevant prior art for the chemical and / or physical and / or radiation-induced crosslinking.

To achieve desired properties of the PSA, for example in order to achieve a sufficient cohesion of the PSAs, the PSAs are usually crosslinked, that is, the individual macromolecules are linked together by bridge bonds. The networking can be done in different ways, so there are physical, chemical or thermal crosslinking methods. Crosslinking of polymers is especially referred to as a reaction in which many initially linear or branched macromolecules are linked by bridge formation between the individual macromolecules to form a more or less branched network. The bridging takes place in particular by suitable chemical molecules - so-called crosslinkers or crosslinking agents - react with the macromolecules, for example with certain functional groups of the macromolecules, which are particularly vulnerable to the respective crosslinking molecule. The sites of the crosslinker molecule which attack the macromolecules are usually referred to as "reactive centers." Crosslinker molecules can link two macromolecules together - by reacting one and the same crosslinker molecule with two different macromolecules, ie in particular having at least two reactive centers. or crosslinker molecules can also have more than two reactive centers, so that a single crosslinker molecule can then also link together three or more macromolecules.As a side reaction, intramolecular reactions can occur if one and the same crosslinker molecule binds to at least two of its reactive centers. and in the sense of effective crosslinking of the polymer, such side reactions are generally undesirable.

A distinction can be made between various types of crosslinkers, namely 1) covalent crosslinkers, namely those which covalently attack the macromolecules to be linked and thus a covalent chemical bond between their corresponding reactive center and the site of attack - especially the functional group - educate on the macromolecule. In principle, all imaginable covalent bonds forming chemical reactions come into question.

2.) coordinative crosslinkers, namely those that coordinate to the macromolecules to be linked and thus form a coordinative bond between their corresponding reactive center and the site of attack - especially the functional group - on the macromolecule. In principle, all conceivable coordinative bonds forming chemical reactions come into question. The present invention further relates to a crosslinked pressure-sensitive adhesive strip obtainable by crosslinking the self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2.

The self-adhesive layers based on an acrylate composition may contain further constituents, in particular microballoons, tackifier resins and / or additives. With regard to their type and quantity, the remarks on the self-adhesive composition layers based on a vinylaromatic block copolymer composition apply analogously.

(b.1) Special type of self-adhesive layers based on an acrylate compound

The adhesives of the layer SK1, the layer SK2 or preferably both layers SK1 and SK2 are according to a particularly preferred embodiment of the invention - hereinafter referred to as "special embodiment" - crosslinkable adhesives, which preferably comprise

(a) at least a first base component with

(a1) as the first polymer component a base polymer component of a homopolymer, a copolymer or a homogeneous mixture of several homopolymers, several copolymers or one or more homopolymers with one or more copolymers, wherein at least one of the homopolymers or at least one of the copolymers, in particular all of the polymers the base polymer component have functional groups which bring about crosslinkability, in particular with epoxide groups, and (a2) optionally further components which are homogeneously miscible or soluble in the base polymer component, such as resins, additives, monomer residues, short-chain polymerization by-products, and / or impurities,

(b) optionally a second component with

(b1) as a further polymer component with the base polymer component substantially immiscible miscible polymers, in particular those without crosslinkable groups, and

(b2) if appropriate, further constituents which are substantially not homogeneously miscible with the base polymer component and insoluble in the latter, for example certain resins or additives, the component (b2) being in particular wholly or partially homogeneously miscible with the further polymer component (b1),

(c) crosslinker, viz

(c1) at least one covalent crosslinker, in particular epoxy-based, and / or (c2) at least one coordinative crosslinker, and

(d) optionally solvents or solvent residues.

In particular, the crosslinkable self-adhesive compositions SK1 and / or SK2 consist of the said constituents (a), (b), (c) and, if appropriate, (d). The first base component (a) may in particular be a polyacrylate component (P) and the second component (b) in particular an elastomer component (E) in the sense of the above statements.

Suitable polymers for the base polymer component (a1) for the specific embodiment are, in particular, those polymers and polymer mixtures which can be crosslinked both by covalent and by coordinative crosslinkers. These are in particular polymers which have free acid groups for crosslinking. Acrylate copolymers can be used as preferred base polymers, in particular those polymers (copolymers, polymer blends) which are attributable to at least 50% by weight of acrylic monomers. As comonomers for the introduction of the crosslinkable groups, free acid groups having copolymerizable monomers are selected, more preferably, acrylic acid is used. Acid group-containing monomers, such as acrylic acid, have the property of influencing the pressure-sensitive adhesive properties of the PSA. If acrylic acid is used, it is preferred in a proportion of up to maximum 12.5 wt .-%, based on the total of the monomers of the base polymer component used. Depending on the amount of crosslinker used in each case, preferably at least so much acrylic acid is copolymerized in that sufficient acid groups are present that essentially complete conversion of the crosslinkers can occur.

The polyacrylate component (a) of the advantageous PSA of the specific embodiment preferably constitutes a homogeneous phase per se. The elastomer component (b) can be homogeneous in itself or can exhibit multiphase properties in itself, as is known from microphase-separating block copolymers. Polyacrylate and elastomer component are presently chosen so that they are - after intimate mixing - at 20 ° C (ie the usual application temperature for adhesives) are substantially immiscible. "Substantially immiscible" means that the components are either not homogeneously miscible with each other, so that none of the phases has a portion of the second component mixed homogeneously, or that the components are only partially compatible - so that one or both components only that the partial compatibility is insignificant for the invention, that is, the teaching according to the invention is not detrimental, the corresponding components being in the sense of this document then as "essentially free" of the respective other component considered.

Accordingly, the advantageous adhesive of the specific embodiment is present at least at room temperature (20 ° C.) in at least two-phase morphology. Most preferably, the polyacrylate component and the elastomer component are substantially non-homogeneously miscible in a temperature range of 0 ° C to 50 ° C, more preferably still from -30 ° C to 80 ° C.

The polyacrylate component and / or the elastomer component can each be present as 100% systems, that is to say exclusively based on their respective polymer component ((a1) or (b1)) and without further admixture of resins, additives or the like. In a further preferred manner, one or both of these two components in addition to the base polymer component other components are added, such as resins. In a further development, the polymer content of the total adhesive comprises the two polymer components (a1) and (b1) no further constituents (without prejudice to crosslinking agents in the sense of component (c) and optionally present solvents (residues) (d)).

The polyacrylate component (a) of the advantageous adhesive of the specific embodiment particularly comprises one or more polyacrylate-based polymers constituting the base polymer component (a1).

Polyacrylate-based polymers are, in particular, those polymers which are at least predominantly, in particular more than 60% by weight, due to acrylic acid esters and / or methacrylic acid esters, and optionally their free acids, as monomers (referred to below as "acrylic monomers") are preferably obtainable by free radical polymerization.Polyacrylates may optionally contain other building blocks based on further, non-acrylic copolymerizable monomers.The polyacrylates may be homopolymers and / or in particular copolymers.The term "copolymer" for the purposes of this invention both those copolymers in which the comonomers used in the polymerization are purely randomly incorporated, and those in which gradients in the comonomer composition and / or local accumulations of individual comonomer species as well as whole blocks of a monomer in the polymer chains occur alternating comonomer sequences are conceivable.

The polyacrylates may be, for example, of linear, branched, star or grafted structure, and may be homopolymers or copolymers. Advantageously, the average molecular weight (weight average Mw) of at least one of the polyacrylates of the polyacrylate base polymer, with several polyacrylates present advantageously the majority of weight of the polyacrylates, especially all existing Poylacrylate in the range of 250 000 g / mol to 10 000 000 g / mol, preferably in the range of 500,000 g / mol to 5,000,000 g / mol. In a very preferred procedure, the crosslinkers of component (c) of the specific embodiment are homogeneously mixable into the base component, optionally after previous solution in suitable solvents.

As covalent crosslinkers (component (c1)) for the specific embodiment, glycidylamines are preferably used. As the invention particularly preferred representatives Examples are N, N, N ', N'-tetrakis (2,3-epoxypropyl) cyclohexane-1, 3-dimethylamine and N, N, N', N'-tetrakis (2,3-epoxypropyl) -m-xylene -a, called a'-diamine.

It is also advantageous to use polyfunctional epoxides, in particular epoxycyclohexyl carboxylates, as covalent crosslinkers. In particular, 2,2-bis (hydroxymethyl) -1,3-propanediol or (3,4-epoxycyclohexane) methyl-3,4-epoxycyclohexylcarboxylate is exemplified here.

Furthermore, multifunctional azeridines can be used according to the invention. For example, trimethylolpropanes tris (2-methyl-1-aziridinepropionate) may be mentioned for this purpose. As covalent crosslinkers it is further possible to use isocyanates, in particular polyfunctional isocyanate compounds. As multifunctional isocyanate compound, for example, tolylene diisocyanate (TDI), 2,4-tolylene diisocyanate dimer, naphthylene-1,5-diisocyanate (NDI), o-tolylene diisocyanate (TODI), diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, tris (pisocyanatophenyl) thiophosphite, polymethylene polyphenylisocyanate be used. They may be used alone or in a combination of two or more kinds thereof.

In the specific embodiment, at least one covalent crosslinker is used according to the invention, but it is also possible to use two or more covalent crosslinkers, for example the two abovementioned diamine compounds in combination with one another.

Suitable coordinative crosslinkers (component (c2)) for the specific embodiment are, in particular, chelate compounds, in particular polyvalent metal chelate compounds. By the term "polyvalent metal chelate compound" is meant those compounds in which a polyvalent metal is coordinately bonded to one or more organic compounds. As the polyvalent metal atom, Al (III), Zr (IV), Co (II), Cu (I), Cu (II), Fe (II), Fe (III), Ni (II), V (II), V (III), V (IV), V (V), Zn (II), In (III), Ca (II), Mg (II), Mn (II), Y (III), Ce (II), Ce (IV), St (II), Ba (II), Mo (II), Mo (IV), Mo (VI), La (III), Sn (II) Sn (IV), Ti (IV) and the like become. Of these, Al (III), Zr (IV) and Ti (IV) are preferable.

As ligands of the coordinative crosslinkers of the specific embodiment, basically all known ligands can use these. The coordinative binding of the However, atoms used for organic compounds may in particular be those atoms which have electron pairs, such as, for example, oxygen atoms, sulfur atoms, nitrogen atoms and the like. As the organic compound, for example, alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, ketone compounds and the like can be used. Specifically, titanium chelate compounds such as titanium dipropoxide bis (acetylacetonate), titanium dibutoxide bis (octylene glycolate), titanium dipropoxide bis (ethylacetoacetate), titanium dipropoxide bis (lactate), titanium dipropoxide bis (triethanolaminate), titanium di-n-butoxide bis (triethanolaminate), titanium tri-n-butoxide monostearate, butyl titanate dimer, poly ( titanium acetylacetonate) and the like; Aluminum chelate compounds such as aluminum diisopropoxide monoethyl acetate, aluminum di-n-butoxide monomethylacetoacetate, aluminum di-i-butoxide monomethyl acetoacetate, aluminum di-n-butoxide monoethyl acetoacetate, aluminum disec-butoxide monoethyl acetoacetate, aluminum triacetylacetonate, aluminum triethylacetoacetonate,

Aluminum monoacetylacetonate bis (ethylacetoacetonate) and the like, and zirconium chelate compounds such as zirconium tetraacetylacetonate and the like are illustratively shown. Of these, aluminum triacetylacetonate and aluminum dipropoxide are preferred. They may be used alone or in a combination of two or more kinds thereof.

Covalent crosslinkers (c1) are preferably used in the specific embodiment in a total amount of 0.015 to 0.04, preferably 0.02 to 0.035 parts by weight, based on 100 parts by weight of the base polymer component (a1), more preferably in an amount of 0.03 wt .%.

Coordinative crosslinkers (c2) in the specific embodiment are preferably used in an amount of 0.03 to 0.15, preferably 0.04 to 0.1 part by weight based on 100 parts by weight of the base polymer component (a1).

Further preferably, covalent crosslinkers and coordinating crosslinkers are used in the specific embodiment such that the coordinative crosslinkers are present in molar excess, based on the covalent crosslinkers. The crosslinkers are preferably used in the abovementioned quantitative ranges, specifically in such a way that the molar ratio of covalent crosslinkers to coordinative crosslinkers-that is, the ratio of the amount of substance n _k ov of the covalent crosslinker to the amount of substance used nkoord of coordinative crosslinkers in the range of 1 : 1, 3 to 1: 4.5, accordingly 1, 3 ^ nkoord nkov ^ 4,5. Very preferred is a molar ratio of covalent crosslinkers to coordinating crosslinkers of 1: 2 to 1: 4.

(b.2) Elastomer component of the self-adhesive layers based on an acrylate material

As stated above, the adhesive used according to the invention, also in the form of its specific embodiment, may comprise substantially non-homogeneously miscible polymers, in particular an elastomer component, with the polyacrylate component or the base polymer. The elastomer component which is substantially incompatible with the polyacrylate component in turn advantageously comprises one or more than one independently chosen synthetic rubber as the base polymer component. The synthetic rubber used is preferably at least one vinylaromatic block copolymer in the form of a block copolymer having a structure AB, ABA, (AB) _n , (AB) _n X or (ABA) _n X, ABX (A'-B ') _n

the blocks A and A independently of one another for a polymer formed by polymerization of at least one vinyl aromatic such as styrene or α-methylstyrene;

the blocks B and B 'independently of one another for a polymer formed by polymerization of conjugated dienes having 4 to 18 carbon atoms and / or a polymer of an isoprene, butadiene, a Farnesen isomer or a mixture of butadiene and isoprene or a mixture from butadiene and styrene, or containing completely or partially ethylene, propylene, butylene and / or

Isobutylene and / or a partially or fully hydrogenated derivative of such a polymer; X for the remainder of a coupling reagent or initiator and

n stand for an integer> 2.

In particular, all synthetic rubbers are block copolymers having a structure as set forth above. The synthetic rubber may thus also contain mixtures of various block copolymers having a structure as above.

Suitable block copolymers (vinylaromatic block copolymers) thus comprise one or more rubbery blocks B or B '(soft blocks) and one or more glassy blocks A and A '(hard blocks). Particularly preferred is a block copolymer having a structure AB, ABA, (AB) sX or (AB) ₄ X, where A, B and X are as defined above. Very particular preference is given to all synthetic rubbers block copolymers having a structure AB, ABA, (AB) sX or (AB) ₄ X, where A, B and X are as defined above. In particular, the synthetic rubber is a mixture of block copolymers having a structure AB, ABA, (AB) 3X or (AB) ₄ X, which preferably contains at least diblock copolymers AB and / or triblock copolymers ABA. Also advantageous is a mixture of diblock and triblock copolymers and (AB) _n or (AB) nX block copolymers with n greater than or equal to 3.

In some advantageous embodiments, a block copolymer which is a multi-arm block copolymer is additionally or exclusively used. This is described by the general formula wherein Q represents one arm of the multi-arm block copolymer and m again represents the number of arms where m is an integer of at least 3. Y is the residue of a multifunctional linking reagent derived, for example, from a coupling reagent or a multifunctional initiator. In particular, each arm Q independently has the formula A ^* -B ^* , where A ^* and B ^{* are} each selected independently of the remaining arms according to the above definitions for A and A 'and B and B', respectively, such that each A ^{* is} a glassy one Block and B ^{* represents} a soft block. Of course it is also possible to choose identical A ^* and / or identical B ^* for several arms Q or all arms Q.

The blocks A, A 'and A ^* will hereinafter be referred to collectively as A-blocks. The blocks B, B 'and B ^* are hereinafter referred to collectively as B-blocks.

A blocks are generally glassy blocks each having a glass transition temperature above room temperature (below room temperature, in the context of this invention, is understood to be 20 ° C). In some advantageous embodiments, the glass transition temperature of the glassy block is at least 40 ° C, preferably at at least 60 ° C, more preferably at least 80 ° C, or most preferably at least 100 ° C.

The vinyl aromatic block copolymer also generally has one or more rubbery B blocks having a glass transition temperature less than room temperature (20 ° C). In some embodiments, the T _{g of} the soft block is less than -30 ° C or even less than -60 ° C.

In addition to the above-mentioned and particularly preferred monomers for the B blocks, further advantageous embodiments comprise a polymerized conjugated diene, a hydrogenated derivative of a polymerized conjugated diene or a combination thereof. In some embodiments, the conjugated dienes comprise 4 to 18 carbon atoms. Preferred conjugated dienes as monomers for soft block B are in particular selected from the group consisting of butadiene, isoprene, ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene and dimethylbutadiene and also any desired mixtures of these monomers. Block B can also be present as a homopolymer or as a copolymer.

By way of example, ethylbutadiene, phenylbutadiene, piperylene, pentadiene, hexadiene, ethylhexadiene and dimethylbutadiene may additionally be mentioned for further advantageous conjugated dienes for the B blocks, it being possible for the polymerized conjugated dienes to be present as homopolymer or as copolymer. The conjugated dienes are particularly preferred as monomers for the soft block B selected from butadiene and isoprene. For example, the soft block B is a polyisoprene, a polybutadiene or a partially or fully hydrogenated derivative of one of these two polymers, in particular polybutylene-butadiene; or a polymer of a mixture of butadiene and isoprene. Most preferably, the block B is a polybutadiene.

The proportion of A blocks based on the total block copolymers is on average preferably 10 to 40 wt .-%, more preferably 15 to 33 wt .-%.

Preferred as a polymer for A blocks is polystyrene. Preferred as polymers for B blocks polybutadiene, polyisoprene, polyarnarnic and their partially or fully hydrogenated derivatives such as polyethylene butylene, polyethylene-propylene, polyethylene-ethylene-propylene or polybutylene-butadiene or polyisobutylene. Very preferred is polybutadiene.

Mixtures of different block copolymers can be used. Preference is given to using triblock copolymers ABA and / or diblock copolymers AB.

Block copolymers can be linear, radial or star-shaped (multiarm).

(b.3) Crosslinking of self-adhesive layers based on an acrylate material

The layer SK1, the layer SK2 or preferably both layers SK1 and SK2 based on an acrylate composition are preferably crosslinked in the pressure-sensitive adhesive strip according to the invention. The crosslinking preferably takes place on the layer or film of the pressure-sensitive adhesive.

The crosslinking reaction can take place in particular as follows:

In an advantageous procedure, the two substances are pre-dissolved as pure substance or in a suitable solvent to the polymer present in solution, then the polymer thoroughly mixed with the crosslinkers, coated on a temporary or permanent support and then dried under suitable conditions, wherein the crosslinking takes place.

In an optional procedure which is particularly suitable for very reactive systems, first of all one of the crosslinkers is added in pure form or pre-dissolved to the polymer solution. The second crosslinker is supplied shortly before the coating, for example via an in-line metering with a downstream active or static mixer and subsequent coating and drying. The pot life (processing time) of the coordinative crosslinkers can be increased by adding the previously described ligands to the polymer crosslinker solution. The excess ligand is then removed on drying; only then are the coordinative crosslinkers (fully) reactive. The drying conditions (temperature and residence time) are very preferably chosen so that not only the solvent is removed, but also the crosslinking is completed to a large extent, so that a stable level of crosslinking - especially at higher temperatures - is achieved. In particular, the adhesive is completely crosslinked.

Complete crosslinking of an adhesive is understood in accordance with the invention to mean that its maximum shear distance "max" in the micro-shear test under the conditions specified therein for repeated (for example daily) micro-shear path measurement within a period of 48 hours only within the accuracy of the measurement method (approximately to to a maximum of 5%) changes when the adhesive is stored at room temperature (20 ° C) under otherwise normal conditions.

Depending on the field of application of the adhesive, the detection of complete crosslinking can also be carried out for other temperatures (for example 40 ° C., in particular those temperatures which correspond to the respective application temperatures).

Advantageously, the pressure-sensitive adhesive strip according to the invention can be used for bonding components of precision mechanical, optical, electrical and / or electronic devices, for example during their manufacture, repair, decoration or the like. In this case, for example, materials such as plastics, glasses, metals and the like come for bonding. carrier

In principle, all known (permanent) carriers can be used as optional carrier material present in the pressure-sensitive adhesive strip according to the invention, such as scrims, woven fabrics, knitted fabrics, nonwovens, papers, tissues, and films. Typically, films are used, which may be foamed (such as thermoplastic foams) or unfoamed. For the production of the film carrier typically film-forming or extrusion-capable polymers are used, which may additionally be mono- or biaxially oriented. The film carriers may be single-layered or multi-layered, preferably they are single-layered. Furthermore, the film carriers may have cover layers, for example barrier layers which prevent the penetration of components from the adhesive into the film or vice versa. These cover layers may also have barrier properties so as to prevent diffusion of water vapor and / or oxygen.

The back side of the film supports may be subjected to an anti-adhesive physical treatment or coating.

In order to produce a film carrier, it may be appropriate to add additives and further components which improve the film-forming properties, reduce the tendency to form crystalline segments and / or specifically improve or even worsen the mechanical properties.

The film carrier optionally contained in a pressure-sensitive adhesive strip according to the invention may be a non-stretchable film carrier or a stretchable film carrier. The use of a non-stretchable film carrier in the pressure-sensitive adhesive strip according to the invention facilitates the processability of the resulting pressure-sensitive adhesive strip; in particular, the stamping processes can be facilitated. Furthermore, the use of a non-stretchable film carrier, for example polyethylene terephthalate (PET), in the pressure-sensitive adhesive strip according to the invention can lead to improved shock resistance compared to the use of a stretchable film carrier. The shock resistance of the pressure-sensitive adhesive strip according to the invention can be influenced not only by the teilgeschäumte (n) self-adhesive (s), but surprisingly also by the nature of the film carrier used and its thickness. The materials used for the film of the non-stretchable film carrier T are preferably polyesters, in particular polyethylene terephthalate (PET), polyamide (PA), polyimide (PI) or mono- or biaxially oriented polypropylene (PP). Most preferably, the non-stretchable film carrier is polyethylene terephthalate. Also possible is the use of multilayer laminates or coextrudates, in particular from the aforementioned materials. Preferably, the non-stretchable film carrier is single-layered.

In an advantageous procedure, one or both surfaces of the non-stretchable film carrier layer T are physically and / or chemically pretreated. Such pretreatment can be carried out, for example, by etching and / or corona treatment and / or plasma pretreatment and / or priming, preferably by etching. If both surfaces of the carrier layer are pretreated, the pretreatment of each surface can be different or, in particular, both surfaces can be pretreated the same.

In order to achieve very good roughening results, it is recommended to use as reagent for etching the film trichloroacetic acid (C 2 -C -COOH) or trichloroacetic acid in combination with inert pulverulent compounds, preferably silicon compounds, more preferably [SiO 2] x. The purpose of the inert compounds is to be incorporated in the surface of the film, in particular the PET film, in order to increase the roughness and the surface energy in this way.

Corona treatment is a chemical-thermal process for increasing the surface tension / surface energy of polymeric substrates. Between two electrodes, electrons are strongly accelerated in a high-voltage discharge, which leads to an ionization of the air. When a plastic substrate is introduced into the path of these accelerated electrodes, the accelerated electrodes thus produced strike the substrate surface at 2 to 3 times the energy needed to superficially disrupt the molecular bonds of most of the substrates. This leads to the formation of gaseous reaction products and highly reactive, free radicals. These free radicals can react rapidly in the presence of oxygen and the reaction products to form various chemical functional groups on the substrate surface. Functional groups resulting from these oxidation reactions contribute most to increasing the surface energy. The corona treatment can be done with two-electrode, but also with single-electrode systems. During corona pretreatment, different process gases, such as nitrogen, can be used (in addition to conventional air) to form a protective gas atmosphere or support corona pretreatment. The plasma treatment - in particular low-pressure plasma treatment - is a known method for surface pretreatment of adhesives. The plasma leads to an activation of the surface in the sense of a higher reactivity. This leads to chemical changes of the surface, whereby for example the behavior of the adhesive against polar and non-polar surfaces can be influenced. This pretreatment is essentially surface phenomena.

Coatings or primers are generally referred to as primers which in particular have adhesion-promoting and / or passivating and / or corrosion-inhibiting effects. In the context of the present invention, the adhesion-promoting effect is particularly important. Adhesion-promoting primers, often also referred to as adhesion promoters or adhesion promoters, are widely known in the form of commercial products or from the technical literature. A suitable non-stretchable film carrier is available under the trade name Hostaphan® RNK. This film is highly transparent, biaxially oriented and consists of three coextruded layers.

The tensile strength of a non-stretchable film carrier according to the invention is preferably greater than 100 N / mm ² , more preferably greater than 150 N / mm ² , even more preferably greater than 180 N / mm ² and in particular greater than 200 N / mm ² , for example greater than 250 N / mm ² , in the longitudinal direction and preferably at greater than 100 N / mm ² , more preferably greater than 150 N / mm ² , even more preferably greater than 180 N / mm ² , and in particular greater than 200 N / mm ² , such as in greater than 250 N / mm ² , in the transverse direction (given values in each case in relation to the measuring method R1 indicated further down). The film carrier significantly determines the tensile strength of the pressure-sensitive adhesive strip. Preferably, the pressure-sensitive adhesive strip has the same values for the tensile strength as the film carrier used. The modulus of elasticity of the non-stretchable film carrier is preferably more than 0.5 GPa, more preferably more than 1 GPa and especially more than 2.5 GPa, preferably both in the longitudinal direction and in the transverse direction.

If an extensible film carrier is used in the pressure-sensitive adhesive strip according to the invention, then the extensibility of the film carrier is typically sufficient to prevent detachment of the film carrier To ensure pressure-sensitive adhesive strip by stretching stretching substantially in the bonding plane. Preferably, the stretchable film carrier is a carrier having an elongation at break of at least 500%, in particular at least 800%, and optionally a resilience of over 50%. The film carrier preferably has the specified elongation at break values and / or the specified resilience both in the longitudinal direction and in the transverse direction. For example, very extensible films can serve as film carriers. Examples of advantageously usable stretchable film carriers are embodiments of WO 201 1/124782 A1, DE 10 2012 223 670 A1, WO 2009/1 14683 A1, WO 2010/077541 A1, WO 2010/078396 A1. Preferably, the tensile strength of the stretchable carrier material is adjusted so that the pressure-sensitive adhesive strip can be detached again by stretching stretching out of an adhesive bond residue-free and non-destructive.

In a preferred embodiment of a stretchable film carrier, polyolefins are used. Preferred polyolefins are prepared from ethylene, propylene, butylene and / or hexylene, it being possible in each case for the pure monomers to be polymerized or for mixtures of the monomers mentioned to be copolymerized. The polymerization process and the choice of monomers can be used to control the physical and mechanical properties of the polymer film, such as, for example, the softening temperature and / or the tear strength. Particularly preferred is polyethylene, in particular polyethylene foam.

Furthermore, polyurethanes can be used advantageously as starting materials for extensible film carriers. Polyurethanes are chemically and / or physically crosslinked polycondensates, which are typically composed of polyols and isocyanates. Depending on the nature and use ratio of the individual components, expandable materials are available which can be advantageously used in the context of this invention. Raw materials which are available to the formulator for this purpose are mentioned, for example, in EP 0 894 841 B1 and EP 1 308 492 B1. The person skilled in the art is familiar with further raw materials from which expandable film carriers according to the invention can be constructed. Particularly preferred is polyurethane foam.

Furthermore, it is advantageous to use rubber-based materials in extensible film carriers in order to realize stretchability. As rubber or synthetic rubber or blends derived therefrom as starting material for The natural rubber can be stretched from the film of all available grades such as crepe, RSS, ADS, TSR or CV grades, depending on the required level of purity and viscosity, and the synthetic rubber or synthetic rubbers from the group of random copolymerized styrene Butadiene rubbers (BR), the synthetic polyisoprenes (IR), the butyl rubbers (II FR), the halogenated butyl rubbers (XIIR), the ethylene vinyl acetate rubber (SBR), the styrene block copolymers (SBC), the butadiene rubbers (BR) Copolymers (EVA) and the polyurethanes and / or their blends are selected. Particularly advantageous materials for stretchable film carriers are block copolymers. In this case, individual polymer blocks are covalently linked to one another. The block linkage may be in a linear form, but also in a star or graft copolymer variant. An example of a block copolymer which can be used advantageously is a linear triblock copolymer whose two terminal blocks have a softening temperature of at least 40.degree. C., preferably at least 70.degree. C. and whose middle block has a softening temperature of at most 0.degree. C., preferably at most -30.degree. Higher block copolymers, such as tetrablock copolymers, can also be used. It is important that at least two polymer blocks of the same or different type are contained in the block copolymer, which have a softening temperature of at least 40 ° C., preferably at least 70 ° C., and which have at least one polymer block with a softening temperature of at most 0 ° C., preferably at most. 30 ° C are separated from each other in the polymer chain. Examples of polymer blocks are polyethers such as polyethylene glycol, polypropylene glycol or polytetrahydrofuran, polydienes such as polybutadiene or polyisoprene, hydrogenated polydienes such as polyethylene butylene or polyethylene propylene, polyesters such as polyethylene terephthalate, polybutanediol adipate or polyhexanediol adipate, polycarbonate, polycaprolactone, polymer blocks of vinyl aromatic monomers such as polystyrene or poly [a] -methylstyrene, polyalkylvinylether and polyvinylacetate. The person skilled in the corresponding softening temperatures are known. Alternatively, he suggests it, for example, in the Polymer Handbook [J. Brandrup, EH Immergut, EA Grulke (ed.), Polymer Handbook, 4th Ed. 1999, Wiley, New York]. Polymer blocks may be composed of copolymers.

In particular, when in the pressure-sensitive adhesive strips according to the invention, the self-adhesive layers based on vinylaromatic block copolymer such as Styrene block copolymer, the stretchable film support is preferably based on polyvinyl aromatic polydiene block copolymer, in particular of polyvinyl aromatic polybutadiene block copolymer, and typically of tackifier resin. Such a film carrier convinces above all by a low stripping force, which allows easy removability of the pressure-sensitive adhesive strip, as well as a low susceptibility to tear when redetaching the pressure-sensitive adhesive strip.

Furthermore, sheet-like foams (for example made of polyethylene or polyurethane) are conceivable as extensible film carriers.

Furthermore, polyacrylate cores are conceivable as expandable film carriers. According to the invention, these are not foamed.

For better anchoring of the self-adhesive on the stretchable film carriers, the film carrier can be pretreated with the known measures such as corona, plasma or flame. The use of a primer is possible. Ideally, however, pretreatment can be dispensed with.

Preferred embodiment of the pressure-sensitive adhesive strip

Advantageously, the outer, exposed surfaces of the outer layers of adhesive layers of the pressure-sensitive adhesive strips according to the invention can be equipped with anti-adhesive materials such as a release paper or a release film, also called liner, as a temporary carrier. A liner may also be antiadhesive coated material on both sides, such as siliconized material on both sides. A liner (release paper, release film) is not part of a pressure-sensitive adhesive strip, but only an aid for its production, storage and / or for further processing by punching. In addition, unlike a tape carrier, a liner is not firmly bonded to an adhesive layer.

Typical formatting forms of the pressure-sensitive adhesive strips according to the invention are adhesive tape rolls - the pressure-sensitive adhesive strips, in particular in web form, can be produced in the form of rolls, ie in the form of Archimedean spirals, on themselves - as well as adhesive strips, as obtained, for example, in the form of diecuts. Preferably, all layers have substantially the shape of a cuboid. Further preferably, all layers are connected to each other over the entire surface. This compound can be optimized by pretreating the film surfaces. For the purposes of this invention, the general term "adhesive strips" (pressure-sensitive adhesives), also known as "adhesive tape", encompasses all planar structures such as films or foil sections stretched in two dimensions, strips of extended length and limited width, strip sections and the like Diecuts or labels.

The pressure-sensitive adhesive strip thus has a longitudinal extent (x-direction) and a width extent (y-direction). The pressure-sensitive adhesive strip also has a thickness extending perpendicularly to the two dimensions (z-direction), the width dimension and longitudinal extent being many times greater than the thickness. The thickness over the entire length and width determined surface extent of the pressure-sensitive adhesive strip as equal as possible, preferably exactly the same.

The pressure-sensitive adhesive strip according to the invention is in particular in web form. Under a track is understood to be an object whose length (extension in the x direction) is greater by a multiple than the width (extension in the y direction) and the width along the entire length in approximately preferably exactly the same formed.

The use of a non-stretchable film carrier in the pressure-sensitive adhesive strip according to the invention leads to an advantageous handling of the pressure-sensitive adhesive strip, in particular also of filigree diecuts. The non-stretchable film carrier usable in the pressure-sensitive adhesive strip of the invention results in pronounced rigidity in the diecuts, so that the stamping process and the placement of the diecuts are simplified. A stamped product formed from a pressure-sensitive adhesive strip according to the invention with a non-stretchable film carrier can, in particular, have an outer punching edge and an inner recess, so that it is in the shape of a frame. In this case, individual webs may have a width of less than 5 mm or less than 2.5 mm or even less than 1 mm.

The use of a stretchable film carrier in the pressure-sensitive adhesive strip according to the invention allows other advantageous product configurations. It will be in particular Adhesive strips accessible, which can be removed by stretching stretch residue and non-destructive from a bond.

Particularly preferred according to the invention is a pressure-sensitive adhesive strip comprising a film support layer T, a self-adhesive layer SK1 and possibly a self-adhesive layer SK2, which can be detached again by stretching stretching essentially in the bond plane without residue and destruction, wherein the layers SK1 and / or SK2, preferably the two layers SK1 and SK2,

an elastomeric member (a1) containing at least one kind of a polyvinyl aromatic polydiene block copolymer, preferably a polyvinyl aromatic-polybutadiene block copolymer, wherein the elastomeric member (a1) consists of at least 90% by weight of polyvinyl aromatic polydiene block copolymers, the content of Polyvinylaromaten to the polyvinyl aromatic-polydiene block copolymers at least 12 wt .-% and at most 35 wt .-%, and preferably at least 20 wt .-% and at most 32 wt .-%, and the proportion of the elastomer part (a1) based to the corresponding layer SK1 or SK2 is at least 40 wt .-% and at most 55 wt .-%, and preferably at least 45 wt .-%, and

an adhesive resin part (a2) containing at least one kind of an adhesive resin, the adhesive resin part (a2) being at least 90% by weight, preferably at least 95% by weight, substantially compatible with the polydiene blocks and with the polyvinylaromatic Blocks substantially incompatible hydrocarbon resins and the proportion of the adhesive resin part (a2) based on the corresponding layer SK1 or SK2 is at least 40 wt .-% and at most 60 wt .-%, and

optionally a soft resin part (a3), wherein the soft resin part (a3) based on the corresponding layer SK1 or SK2 at 0 wt .-% to at most 5 wt .-%, and

optionally contain further additives (a4), and

wherein the preferably unfoamed film carrier layer T

an elastomeric part (b1) based on at least one kind of a polyvinyl aromatic polydiene block copolymer, wherein the elastomeric part (b1) comprises at least 90% by weight of polyvinyl aromatic polydiene block copolymers, preferably polyvinyl aromatic polybutadiene block copolymers and / or polyvinyl aromatic polyisoprene Block copolymers, the content of polyvinylaromatics on the polyvinylaromatic-polydiene block copolymers is at least 20% by weight and at most 45% by weight, preferably at least 25% by weight and at most 35% by weight, within the elastomer part, the proportion of at least one triblock copolymer or linear or radial multiblock copolymer is at least 80% by weight, preferably at least 90% by weight, the molecular weight of the triblock copolymer or multiblock copolymer (peak molecular weight MP according to GPC) being at least 85,000 g / mol is, and the proportion of diblock copolymers at less than 20 wt .-%, preferably at most 10 wt .-% and in particular at 0 wt .-%, and the proportion of elastomers (b1) based on the formulation of the film support layer T is at least 40% by weight and at most 60% by weight, preferably at least 45% by weight and at most 55% by weight, and

an adhesive resin part (b2) containing at least one kind of an adhesive resin, the adhesive resin part (b2) being at least 90% by weight, preferably at least 95% by weight, substantially compatible with the polydiene blocks and with the polyvinylaromatics Blocks of substantially incompatible hydrocarbon resins and the proportion of the adhesive resin part (b2) based on the total formulation of the film support layer T is at least 40 wt .-% and at most 60 wt .-%, and optionally a soft resin part (b3), wherein the soft resin content (b3) based on the total formulation of the film support layer T is 0 wt .-% to at most 5 wt .-%,

and optionally contains further additives (b4),

and wherein the density of the film support layer T is at least 950 g / cm ³ .

Preferably, the adhesive resin part (a2) and the adhesive resin part (b2) are chemically identical. Production of the pressure-sensitive adhesive strip

The production and processing of the invention can be used self-adhesive compositions SK1 or SK2 can be carried out both from the solution and from the melt (hot melt). The application of the inventively employable self-adhesive compositions SK1 or SK2 on carrier layers can be effected by direct coating or by lamination, in particular hot lamination.

In a typical process for producing a self-adhesive composition layer according to the invention, all constituents of the adhesive are dissolved in a solvent mixture such as, for example, gasoline / toluene / acetone. For example, the microballoons are slurried in gasoline and stirred into the dissolved adhesive. For this purpose, in principle, the known compounding and stirring units can be used, it being important to ensure that the microballoons do not expand during mixing. Once the microballoons are homogeneously dispersed in the solution, the adhesive can be coated, again using coating systems according to the prior art. For example, the coating can be done by a doctor blade on a conventional PET liner. In the next step, the coated adhesive is dried, for example at 100 ° C for 15 min, and optionally crosslinked. In none of the above steps does an expansion of the microballoons occur. After drying, the adhesive layer is covered with a second layer PET liner or with a carrier and partially foamed in a suitable temperature window, for example at 130 ° C to 180 ° C, in the oven, covered between the two liners or between the liner and the carrier to produce a particularly smooth surface. The partial foaming is achieved by timely cooling, for example at room temperature (20 ° C), so that sets the desired degree of foaming.

If the dried adhesive layer between the two liners is foamed, the result is a pressure-sensitive adhesive strip according to the invention which consists of the self-adhesive layer. If the self-adhesive layer is foamed between the liner and the backing, the result is a pressure-sensitive adhesive strip according to the invention in the form of a one-sided adhesive tape.

Alternatively, prior to the foaming of the dried self-adhesive layer located between the liner and the carrier, a second likewise dried microballoon self-adhesive layer can be laminated onto the surface of the carrier opposite the dried self-adhesive layer, which in turn is applied to a liner, so that an unfoamed three-layer composite of one internal support and two standing in direct contact with the support, self-adhesive layers, which are in turn provided on their outer surfaces with liners, can be provided. Such a three-layer composite can also be provided by simultaneously coating the carrier T with the microballoon-containing unfoamed self-adhesives, whereupon the self-adhesive layers are dried at 100 ° C. for 15 minutes and then covered with liners. After drying, the adhesive layers in a suitable temperature-time window in the oven partially foamed (see above), and covered between the two liners to a particularly smooth surface to create. This results in an inventive pressure-sensitive adhesive strip in the form of a double-sided adhesive tape with carrier.

The surface of the partially expanded self-adhesive composition layer produced by the solvent method typically has a roughness R _a of less than 15 μm, preferably less than 10 μm, more preferably less than 5 μm and very particularly preferably less than 3 μm. The surface roughness R _a is an industry standard unit for surface finish quality and represents the average height of the roughness, in particular the average absolute distance from the centerline of the roughness profile within the evaluation range. In other words, R _a is the arithmetic mean roughness, ie the arithmetic mean of all profile values of the roughness profile. R _a is measured in the present application by means of laser triangulation. Low surface roughness in particular has the advantage that results in an improved shock resistance of the pressure-sensitive adhesive strip. Furthermore, typically improved bond strengths arise.

A particularly low surface roughness R _{a of} a partially expanded self-adhesive layer of typically less than 3 μm, preferably less than 2 μm, and in particular less than 1 μm, can surprisingly be produced according to the solvent method when a suitable degree of foaming is selected, especially when the self-adhesive composition layer is a monolayer Having microballoons. A self-adhesive composition layer then has a monolayer of microballoons if there are not several microballoons stored one above the other within the self-adhesive composition layer. In the self-adhesive composition layer, the microballoons preferably lie approximately in one plane (see FIGS. 5a and 6a). Such a monolayer can be provided, for example, by the self-adhesive composition layer having a mass application, measured in g / m ² , which is smaller than the mean diameter of the voids formed by the microballoons in the self-adhesive composition layer, measured in μηη. In the context of the present application, the mass application relates to the dry weight of the applied adhesive mixture. The ratio of the mass application of the adhesive layer (in g / m ² ) to the mean diameter of the cavities formed by the microballoons (in μηη) is preferably 0.6-0.9, particularly preferably 0.7-0.8. By a suitable choice and combination of adhesive, liner and foaming process, even larger microballoons, which are also present in the adhesive layer due to the particle size distribution, can become smoother Product surface are held in the tape. The foaming between two liners promotes, for example, the production of pressure-sensitive adhesive strips with particularly smooth surfaces. The present invention can therefore provide pressure-sensitive adhesive strips which are thin at the same time and have a low surface roughness R _a , and thus high bond strengths and shock resistance. Such pressure-sensitive adhesive strips are of particular interest for bonding such components and electronic devices in which only little space is available for bonding, in particular in mobile devices such as mobile phones. In particular, unsuitable foaming parameters may lead to microballoons emerging from the adhesive and consequently to a rough surface. Especially with small thicknesses of the self-adhesive layers, high degrees of foaming, in particular full foaming, can cause microballoons to protrude from the adhesive layer after foaming and thus cause increased roughness R _a . This phenomenon can be prevented, in particular, by suitable degrees of partial foaming, which are already apparent to the person skilled in the art with the respective application of mass or the respective type of microballoon through a few experiments. In particular, the expansion temperature is chosen to be higher than the drying temperature in order to avoid expansion of the microballoons during drying.

Alternatively, the production of the self-adhesive layers SK1 or SK2 can be carried out from the melt. The degree of foaming is typically set by the temperature and residence time of the adhesive mixture in the extruder.

Accordingly, the invention includes, for example, a method for producing a self-adhesive composition layer according to the invention, wherein

the ingredients for forming an adhesive such as polymers, resins or fillers and unexpanded microballoons are mixed in a first mixing unit and heated to expansion temperature,

partially expand the microballoons during mixing,

the adhesive mixture together with the partially expanded microballoons in one

Roll applicator is formed into a layer, and if appropriate, the adhesive mixture, together with the partially expanded microballoons, is applied to a web-shaped carrier or release material. Furthermore, the invention comprises a method for producing a self-adhesive composition layer according to the invention, wherein

The components for forming an adhesive, such as polymers, resins or fillers and unexpanded microballoons, are mixed in a first mixing unit and heated to the expansion temperature under excess pressure,

parts of the microballoons exiting the mixing unit,

the adhesive mixture is formed together with the partially expanded microballoons in a roll applicator to form a layer, and

if appropriate, the adhesive mixture, together with the partially expanded microballoons, is applied to a web-shaped carrier or release material.

Likewise, the invention comprises a method for producing a self-adhesive composition layer according to the invention, wherein

the constituents for forming an adhesive, such as polymers, resins or fillers, are mixed with unexpanded microballoons in a first mixing unit under overpressure and at a temperature below the expansion temperature of the

Tempered microballoons,

· The mixed, in particular homogeneous adhesive from the first

Mixing unit are transferred to a second unit and heated to expansion temperature,

the microballoons are partially expanded in the second aggregate or on exit from the second aggregate,

The adhesive mixture, together with the partially expanded microballoons, is formed into a layer in a roll applicator, and

if appropriate, the adhesive mixture, together with the partially expanded microballoons, is applied to a web-shaped carrier or release material. Likewise, the invention relates to a method for producing a self-adhesive composition layer according to the invention, wherein

the constituents for forming an adhesive, such as polymers, resins or fillers, are mixed in a first mixing unit, the mixed, in particular homogeneous, adhesive is transferred from the first mixing unit into a second mixing unit into which the unexpanded microballoons are also deposited,

the microballoons are partially expanded in the second mixing unit or on leaving the second mixing unit,

the adhesive mixture, together with the partially expanded microballoons, is formed into a layer in a roll applicator,

The described hotmelt processes for producing a self-adhesive composition layer according to the invention thus each represent a process in which a pressure-sensitive adhesive strip consisting of a single self-adhesive composition layer can be provided, i. a transfer tape. Optionally, the self-adhesive composition layer may be provided with sheet release material, i. a liner, be covered. Preferably, the self-adhesive composition layer is covered on both surfaces with a liner.

If in the described method the self-adhesive composition layer obtained is applied to a web-shaped carrier material, for example a film carrier, the result is a one-sided adhesive tape. Optionally, the surface of the self-adhesive composition layer facing the carrier layer T can subsequently be coated with web-shaped release material, i. a liner, be covered. If, in the three-layer system comprising carrier layer T, self-adhesive composition layer and liner, a further self-adhesive composition layer is applied to the surface of carrier layer T facing the self-adhesive composition layer, a double-sided adhesive tape with carrier according to the invention results. Optionally, the surface of the self-adhesive composition layer facing the carrier layer T can subsequently be coated with web-shaped release material, i. a liner, be covered.

With microballoons teilgeschäumte masses usually need not be degassed before coating to obtain a uniform, closed coating image. The part-expanding microballoons displace the air trapped in the adhesive during compounding. At high flow rates, it is still advisable, the Degas masses before coating to obtain a uniform mass template in the nip. The degassing is ideally carried out immediately before the roll applicator at mixing temperature and a differential pressure to the ambient pressure of at least 200 mbar.

Furthermore, it is advantageous if

the first mixing unit is a continuous unit, in particular a planetary roller extruder, a twin-screw extruder or a pin extruder,

the first mixing aggregate is a discontinuous aggregate, in particular a Z-kneader or an internal mixer,

the second mixing unit is a planetary roller extruder, a single-screw or twin-screw extruder or a pin extruder and / or

the Ausformaggregat in which the adhesive is formed together with the partially expanded microballoons to form a layer, a calender, a Walzenauftragswerk or a gap formed by a roller and a stationary doctor blade is.

With the hotmelt process according to the invention, all the previously known components of adhesives described in the literature, in particular self-adhesive, are solvent-free processable.

Many aggregates for the continuous production and processing of solvent-free polymer systems are known. In most cases, screw machines such as single-screw and twin-screw extruders of very different process lengths and equipment are used. But there are also continuously operating kneaders of various types, for example, combinations of kneaders and screw machines, or even planetary roller extruder used for this task.

Planetary roller extruders have been known for some time and were first used in the processing of thermoplastics such as PVC, where they were mainly used to feed the follower units such as calenders or rolling mills. Its advantages of the large surface renewal for material and heat exchange, with which the energy introduced by friction can be dissipated quickly and effectively, as well as the low residence time and the narrow residence time spectrum has lately been extended, inter alia, to compounding processes which include a require particularly temperature-controlled driving. Depending on the manufacturer, planetary roller extruders are available in various designs and sizes. Depending on the desired throughput, the diameters of the roll cylinders are typically between 70 mm and 400 mm.

Planetary roller extruders usually have a filling part and a compounding part.

The filling part consists of a screw conveyor, to which all solid components are continuously metered. The screw conveyor then transfers the material to the compounding section. The area of the filling part with the screw is preferably cooled in order to avoid caking of materials on the screw. But there are also embodiments without screw part, in which the material is placed directly between the central and planetary spindles. However, this is not important for the effectiveness of the method according to the invention.

The compounding part consists of a driven central spindle and a plurality of planetary spindles, which rotate around the central spindle within one or more roller cylinders with internal helical gearing. The speed of the central spindle and thus the rotational speed of the planetary spindles can be varied and is thus an important parameter for controlling the compounding process.

The materials are circulated between central and planetary spindles or between planetary spindles and helical gearing of the roller part, so that the dispersion of the materials into a homogeneous compound takes place under the influence of shear energy and external tempering.

The number of rotating in each roller cylinder planetary spindles can be varied and thus adapted to the requirements of the process. The number of spindles influences the free volume within the planetary roller extruder, the dwell time of the material in the process and also determines the area size for the heat and material exchange. The number of planetary spindles has an influence on the compounding result via the shear energy introduced. With a constant roll diameter, a better homogenization and dispersing performance or a larger product throughput can be achieved with a larger number of spindles. The maximum number of planetary spindles that can be installed between the central spindle and the roll cylinder depends on the diameter of the roll cylinder and the diameter of the planetary spindles used. When using larger roll diameter, as they are necessary to achieve throughput rates on a production scale, or smaller diameter for the planetary spindles, the roll cylinders can be equipped with a larger number of planetary spindles. Typically, with a roll diameter of D = 70 mm, up to seven planetary spindles are used, while with a roll diameter of D = 200 mm, for example, ten and for a roll diameter of D = 400 mm, for example, 24 planetary spindles can be used.

According to the invention, it is proposed to carry out the coating of the partly-foamed adhesives solvent-free with a Mehrwalzenauftragswerk. These can be commissioned works consisting of at least two rolls with at least one nip up to five rolls with three nips.

Also conceivable are coating units such as calenders (I, F, L calenders), so that the partially-foamed adhesive is shaped to the desired thickness when passing through one or more nips.

The preferred 4-roll applicator is formed by a metering roll, a doctor blade which determines the thickness of the layer on the substrate and which is arranged parallel to the metering roll, and a transfer roll which is located below the metering roll. On the lay-up roller, which forms a second nip together with the transfer roller, the mass and the web-shaped material are brought together.

In order to improve the transfer behavior of the molded mass layer from one roll to another, it is also possible to use antiadhesive-treated rolls or anilox rolls. In order to produce a sufficiently precisely shaped adhesive film, the circumferential speeds of the rolls may have differences.

Depending on the type of web-shaped carrier material to be coated, the coating can be carried out in a synchronous or countercurrent process. The forming unit can also be formed by a gap which results between a roller and a stationary doctor blade. The fixed squeegee may be a knife blade or a fixed (half) roller.

When forming the adhesive composition into a layer in the roller applicator, the partially expanded microballoons are pressed back into the polymer matrix of the adhesive, thus producing a smooth surface. The adhesion loss through the microballoons can be significantly reduced. The surface of the self-adhesive composition layer thus produced typically has a roughness R _{a of} less than 15 μm, particularly preferably less than 10 μm, very particularly preferably of less than 3 μm.

It has been proven to adapt the temperature of the rolls to the expansion temperature of the microballoons. Ideally, the roll temperature of the first rolls is above the expansion temperature of the microballoons to allow re-foaming of the microballoons to the desired degree of foaming without destroying them. The last roll should have a temperature equal to or lower than the expansion temperature, so that the microballoon shell can solidify and form the smooth surface according to the invention.

Alternatively, the roll temperature of all rolls may be at or below the expansion temperature of the microballoons so that the microballoon shell can solidify early, thereby minimizing post-foaming. Also in this procedure, the inventive smooth surface forms.

It has proven to be particularly advantageous to choose the temperature control of the individual rolls so that optionally controlled re-foaming can take place in such a way that transferring rolls can have a temperature above or equal to the foaming temperature of the selected microballoon type, while decreasing rolls should have a temperature below or equal to the foaming temperature to prevent uncontrolled foaming, and all rolls can be individually set at temperatures of 30 to 220 ° C. characters

With reference to the figures described below, particularly advantageous embodiments of the invention are explained in more detail, without wishing to unnecessarily limit the invention.

FIG. 1 shows the schematic structure of a three-layer pressure-sensitive adhesive strip according to the invention consisting of three layers 1, 2, 3 as a cross section. The strip comprises a stretchable film carrier 1 (layer T), for example based on vinylaromatic block copolymer. Alternatively, the strip comprises a non-stretchable film carrier 1 (layer T), for example in the form of a transparent PET film. On the upper side and on the underside of the film carrier 1 there are two outer partially foamed self-adhesive layers 2, 3 (layer SK1 and layer SK2), preferably each based on vinylaromatic block copolymer. The self-adhesive layers 2, 3 (layers SK1 and SK2) are in turn covered with a liner 4, 5 in the exemplary embodiment shown.

FIG. 2 furthermore shows the schematic structure of a single-layer pressure-sensitive adhesive strip according to the invention consisting of a layer 2 as a cross-section.

The strip comprises a partially foamed self-adhesive layer 2 (layer SK1), preferably based on vinylaromatic block copolymer. The self-adhesive layer 2 (layer SK1) is covered in the illustrated exemplary embodiment with a liner 4, 5 each.

FIG. 3a shows a photomicrograph of the vinylaromatic block copolymer-based partially foamed self-adhesive composition SK1 according to the invention (microballoon type: Expancel 920 DU20, degree of expansion: 44%) from example 4.

FIG. 3b shows a photomicrograph of the vinylaromatic block copolymer-based partially foamed self-adhesive composition SK1 according to the invention (micro balloon type: Expancel 920 DU20, degree of expansion: 49%) from Example 5. FIG. 3c shows a photomicrograph of the non-foamed vinyl aromatic block copolymer-based self-adhesive composition layer (micro balloon type: Expancel 920 DU20, degree of expansion: 0%) from Comparative Example 6 (not according to the invention).

FIG. 3d shows a photomicrograph of the fully-foamed vinyl aromatic block copolymer-based self-adhesive composition layer (micro balloon type: Expancel 920 DU20, degree of expansion: 100%) from Comparative Example 7 (not according to the invention).

FIG. 3e shows an incident light micrograph of the overexpanded vinyl aromatic block copolymer-based self-adhesive composition (micro balloon type: Expancel 920 DU20, degree of expansion: -88%) from Comparative Example 8 (not according to the invention).

FIG. 4a shows a photomicrograph of the vinylaromatic block copolymer-based partially foamed self-adhesive composition SK1 according to the invention (micro balloon type: Expancel 920 DU40, degree of expansion: 29%) from Example 9. FIG. 4b shows an incident light micrograph of the vinylaromatic block copolymer-based partially foamed self-adhesive composition SK1 according to the invention (microballoon type: Expancel 920 DU40, degree of expansion : 69%) from example 10.

FIG. 4c shows a photomicrograph of the non-foamed self-adhesive composition layer based on vinylaromatic block copolymer (microballoon type:

Expancel 920 DU40, degree of expansion: 0%) from Comparative Example 1 1 (not according to the invention).

FIG. 4 d shows an up-light microscopic image of the fully-foamed self-adhesive composition layer based on vinylaromatic block copolymer (microballoon type:

Expancel 920 DU40, degree of expansion: 100%) from Comparative Example 12 (not according to the invention).

FIG. 4e shows a transmitted-light micrograph of the overexpanded self-adhesive composition layer based on vinylaromatic block copolymer (microballoon type: Expancel 920 DU40, degree of expansion: -12%) from Comparative Example 13 (not according to the invention).

FIG. 5 a shows an SEM image of a cryobreak edge of the partially-foamed self-adhesive composition SK 1 based on vinylaromatic block copolymer (micropump type: Expancel 920 DU20, degree of expansion: 73%, mass application: 10 g / m ² , thickness: 13 μm) from Example 17. The microballoons are present in a monolayer. The surface of the layer SK1 is smooth. The monolayer of the microballoons is also illustrated by the sketch of the self-adhesive composition layer SK1 from FIG. 5b.

FIG. 6a shows a SEM image of another cryobreak edge of the partially foamed self-adhesive composition SK1 based on vinylaromatic block copolymer (micro balloon type: Expancel 920 DU20, degree of expansion: 73%, mass application: 10 g / m ² , thickness: 13 μm) from Example 17. The microballoons are present also in a monolayer. It is noticeable that even a larger microballoon, which is also present in the adhesive layer due to the particle size distribution, is held in the adhesive tape with a smooth product surface. The monolayer of the microballoons is also illustrated by the sketch of the self-adhesive composition SK1 of FIG. 6b. The invention will be explained in more detail by some examples. With reference to the examples described below, particularly advantageous embodiments of the invention are explained in more detail, without wishing to unnecessarily limit the invention.

Examples

In the following, the production of pressure-sensitive adhesive strips according to the invention will be described, each consisting of a single self-adhesive layer SK1 based on an adhesive partially foamed with microballoons (MBs). The base adhesive, the micro balloon type and content as well as the application of the composition were varied. The mass application refers to the dry weight of the applied adhesive solution.

Example 1 :

An inventive pressure-sensitive adhesive strip based on a styrene block copolymer (SBC) composition was prepared. For this purpose, first a 40 wt .-% adhesive solution in gasoline / toluene / acetone made of 50.0 wt .-% Kraton D1 102AS, 45.0 wt .-% Dercolyte A1 15, 4.5 wt .-% Wingtack 10th and 0.5% by weight of antiaging agent Irganox 1010 (also called adhesive solution 1). The weight fractions of the dissolved constituents in each case relate to the dry weight of the resulting solution. The constituents of the adhesive are characterized as follows:

Kraton D1 102AS: Styrene-butadiene-styrene triblock copolymer from Kraton Polymers with 17% by weight diblock, block polystyrene content: 30% by weight

Dercolyte A1 15: solid a-pinene adhesive resin with a ring and ball softening temperature of 1 15 ° C and a DACP of 35 ° C

Wingtack 10: Liquid hydrocarbon resin from Cray Valley

Irganox 1010: pentaerythritol tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) from BASF SE

The solution was then spiked with 3.3% by weight Unexpanded Expancel 920 DU20 microballoon using the microballoons as a slurry in gasoline. The weight fractions of the microballoons in the examples refer in each case to the dry weight of the solution used to which they were added (ie the dry weight of the solution used is set as 100%). The resulting mixture was then spread with a brush on a PET liner equipped with a separating silicone in such a layer thickness that, after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying of the mass layer, a mass order of 75 g / m ² .

Subsequently, a second PET liner was laminated to the free surface of the prepared and dried adhesive layer and the adhesive layer then partially foamed for 30 s at 140 ° C between the two liners in the oven. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a foaming degree of 76%, a thickness of 1 1 1 μηη, a density of 674 kg / m ³ and a surface roughness R _a of less than 10 μηη on. By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained. Comparative Examples 2 and 3:

As Comparative Example 2 is the pressure-sensitive adhesive strip of Example 1, but before foaming. The adhesive layer (without PET liner) had a thickness of 75 μm, a density of 1000 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 3 is the pressure-sensitive adhesive strip of Example 1, wherein in the production of Example 1, the adhesive layer was fully expanded at 175 ° C between the two liners in the oven for 30 s, ie to an expansion of 100%. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a thickness of 131 μηη, a density of 572 kg / m ³ and a roughness R _a of less than 10 μηη on.

By punching out a pressure-sensitive adhesive strip of the desired dimensions was obtained in each case.

Examples 4 and 5:

Adhesive Solution 1 (from Example 1) was spiked with 1% by weight Unexpanded Expancel 920 DU20 microballoon using the microballoons as a slurry in gasoline. The mixture obtained was then spread with a brush on a PET liner equipped with a separating silicone, in such a layer thickness, that after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying of the mass layer, a mass order of 38 g / m ² .

Subsequently, a second PET liner was laminated on the free surface of the prepared and dried adhesive layer and the adhesive layer then for 30 s at 140 ° C (Example 4) or for 10 s at 175 ° C (Example 5) between the two liners in Partially foamed oven. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) of Example 4 had a degree of foaming of 44%, a thickness of 42 μηη, a density of 906 kg / m ³ and a roughness R _a of less than 10 μηη on; the adhesive layer (without PET liner) from Example 5 had a foaming degree of 49%, a thickness of 42 μm, a density of 895 kg / m ³ and a roughness R _a of less than 10 μm. By punching out, a pressure-sensitive adhesive strip according to the invention of the desired dimensions was obtained in each case. Comparative Examples 6 to 8:

As Comparative Example 6, the pressure-sensitive adhesive strip of Example 4 or 5, but before foaming is used. The adhesive layer (without PET liner) had a thickness of 38 μm, a density of 1000 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 7 is the pressure-sensitive adhesive strip of Example 4 or 5, wherein in the manufacture of divergent from Example 4 or 5, the adhesive layer for 15 s at 175 ° C between the two liners in the furnace was completely expanded, ie to an expansion of 100%. After cooling at room temperature (20 ° C.), the adhesive layer (without PET liner) had a thickness of 48 μm, a density of 786 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 8 is the pressure-sensitive adhesive strip of Example 4 or 5, wherein in the production of Example 4 or 5, the adhesive layer was overexpanded for 120 s at 175 ° C between the two liners in the oven to - 88%. The value "-88%" means that the increase in thickness of the unexpanded pressure-sensitive adhesive strip on the fully expanded pressure-sensitive adhesive strip was again 88% lost due to the overexpansion After cooling at room temperature (20 ° C.), the adhesive layer (without PET liner) exhibited a thickness of 39 μηη, a density of 975 kg / m ³ and a roughness R _a of less than 10 μηη on.

By punching out a pressure-sensitive adhesive strip of the desired dimensions was obtained in each case. Examples 9 and 10:

Adhesive Solution 1 (from Example 1) was charged with 1.5% by weight Unexpanded Expancel 920 DU40 microballoon, the microballoons being used as a slurry in gasoline. The resulting mixture was then coated with a coating bar onto a PET liner equipped with a separating silicone in such a layer thickness struck that after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying the mass layer, a mass application of 60 g / m ² resulted. Subsequently, a second PET liner was laminated to the free surface of the prepared and dried adhesive layer and the adhesive layer then for 30 s at 140 ° C (Example 9) or for 10 s at 175 ° C (Example 10) between the two liners in Partially foamed oven. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) of Example 9 had a foaming degree of 29%, a thickness of 71 μηη, a density of 885 kg / m ³ and a roughness R _a of less than 10 μηη on; the adhesive layer (without PET liner) from Example 10 had a foaming degree of 69%, a thickness of 89 μm, a density of 722 kg / m ³ and a roughness R _a of less than 10 μm. By punching out, a pressure-sensitive adhesive strip according to the invention of the desired dimensions was obtained in each case.

Comparative Examples 1 1 to 13: As Comparative Example 1 1, the pressure-sensitive adhesive strip from Examples 9 and 10, respectively, but before foaming, is used. The adhesive layer (without PET liner) had a thickness of 61 μm, a density of 1000 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 12 is the pressure-sensitive adhesive strip of Example 9 or 10, wherein in the production of Example 9 or 10, the adhesive layer for 15 s at 175 ° C between the two liners in the oven was completely expanded, ie to an expansion of 100%. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a thickness of 103 μηη, a density of 595 kg / m ³ and a roughness R _a of less than 10 μηη.

As a comparative example 13 is the pressure-sensitive adhesive strip of Example 9 or 10, wherein in the production of Example 9 or 10, the adhesive layer was overexpanded for 60 s at 175 ° C between the two liners in the oven to - 12%. The value "-12%" means that the thickness increase of the unexpanded pressure-sensitive adhesive strip on the fully expanded pressure-sensitive adhesive strip by the overexpansion again to 12% lost. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a thickness of 95 μηη, a density of 645 kg / m ³ and a roughness R _a of less than 10 μηη. By punching out a pressure-sensitive adhesive strip of the desired dimensions was obtained in each case.

EXAMPLES 14-18 Adhesive Solution 1 (from Example 1) was charged with 1.5% by weight unexpanded Expancel 920 DU20 microballoon, the microballoons being used as a slurry in gasoline. The mixture obtained was then spread with a brush on a PET liner equipped with a separating silicone, in such a layer thickness that, after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying the mass layer, a potting order of 10 g / m ² .

Subsequently, a second PET liner was laminated on the free surface of the prepared and dried layer of adhesive and the adhesive layer then for 10 s at 130 ° C (Example 14), for 20 s at 130 ° C (Example 15), for 60 s at 130 ° C (Example 16), partially foamed for 20 s at 140 ° C (Example 17) or 60 s at 150 ° C (Example 18) between the two liners in the oven. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) of Example 14 had a foaming degree of 27%, a thickness of 1 μηη, a density of 913 kg / m ³ and a roughness R _a of less as 10 μηη on; the adhesive layer (without PET liner) of Example 15 had a foaming degree of 38%, a thickness of 1 1, 5 μm, a density of 878 kg / m ³ and a roughness R _a of less than 10 μm; the adhesive layer (without PET liner) of Example 16 had a degree of foaming of 59%, a thickness of 12.5 μm, a density of 813 kg / m ³ and a roughness R _a of less than 10 μm; the adhesive layer (without PET liner) from Example 17 had a degree of foaming of 73%, a thickness of 13 μm, a density of 768 kg / m ³ and a roughness R _a of less than 10 μm; the adhesive layer (without PET liner) from Example 18 had a degree of foaming of 86%, a thickness of 13.5 μm, a density of 725 kg / m ³ and a roughness R _a of less than 10 μm. By punching out, a pressure-sensitive adhesive strip according to the invention of the desired dimensions was obtained in each case.

Comparative Examples 19 to 21:

As comparative example 19, the pressure-sensitive adhesive strip from examples 14 to 18, but before foaming, is used. The adhesive layer (without PET liner) had a thickness of 10 μm, a density of 1000 kg / m ³ and a roughness R _a of less than 10 μm. As a comparative example 20, the pressure-sensitive adhesive strip from Examples 14 to 18 is used, wherein, unlike in Examples 14 to 18, the adhesive layer was fully expanded at 170 ° C. between the two liners in the oven for 20 seconds, ie to a degree of expansion of 100%. After cooling at room temperature (20 ° C.), the adhesive layer (without PET liner) had a thickness of 14 μm and a density of 680 kg / m ³ .

As a comparative example 21, the pressure-sensitive adhesive strip from Examples 14 to 18 is used, wherein, unlike Examples 14 to 18, the adhesive layer was overexpanded for 60 s at 170 ° C. between the two liners in the oven to -62%. The value "-62%" means that the increase in thickness of the unexpanded pressure-sensitive adhesive strip on the fully expanded pressure-sensitive adhesive strip was again lost by over-expansion by 62% After cooling at room temperature (20 ° C.), the adhesive layer (without PET liner) exhibited a thickness of 1 1, 5 μηη and a density of 880 kg / m ³ on.

Example 22:

An inventive pressure-sensitive adhesive strip based on an acrylate composition was produced.

For this purpose, the base polymer P1, ie the polyacrylate, was first prepared by a free radical polymerization in solution. One more conventional for radical polymerizations Reactor was charged with 47.5 kg of 2-ethylhexyl acrylate, 47.5 kg of n-butyl acrylate, 5 kg of acrylic acid and 66 kg of gasoline / acetone (70/30). After passage of nitrogen gas for 45 minutes with stirring, the reactor was heated to 58 ° C and 50 g of AI BN was added. Subsequently, the outer heating bath was heated to 75 ° C and the reaction was carried out constantly at this external temperature. After 1 h, 50 g of AIBN were again added and after 4 h was diluted with 20 kg of gasoline / acetone mixture. After 5.5 hours and after 7 hours, in each case 150 g of bis (4-tert-butylcyclohexyl) peroxydicarbonate were re-initiated. After a reaction time of 22 hours, the polymerization was stopped and cooled to room temperature (20 ° C). The polyacrylate has an average molecular weight of M _w = 386,000 g / mol and a polydispersity PD (M _w / M _n ) = 7.6.

100% by weight of the base polymer P1 was then adjusted to a solids content of 38% by weight by the addition of gasoline and acetone. Following were 0.075 wt .-% of the covalent crosslinker Erysis GA 240 (N, N, N ', N'-tetrakis (2,3-epoxypropyl) -m-xylene-a, a'-diamine) from Emerald Performance Materials added, based on the weight of the base polymer used. The mixture was stirred for 15 minutes with the addition of 2% by weight Unexpanded Expancel 920 DU20 microballoons in gas / acetone at room temperature (20 ° C). The mixture obtained was then spread with a brush on a PET liner equipped with a separating silicone, in such a layer thickness, that after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying of the mass layer, a mass order of 85 g / m ² .

Subsequently, a second PET liner was laminated to the free surface of the prepared and dried layer of adhesive, and then the adhesive layer was partially foamed in the oven for 20 s at 160 ° C between the two liners. After cooling at room temperature (20 ° C.), the adhesive layer (without PET liner) had a degree of foaming of 78%, a thickness of 105 μm, a density of 805 kg / m ³ and a roughness R _a of less than 10 μm , By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained. Comparative Examples 23 and 24:

The pressure-sensitive adhesive strip of Example 22 is used as Comparative Example 23, but before foaming. The adhesive layer (without PET liner) had a thickness of 80 μm, a density of 1056 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 24, the pressure-sensitive adhesive strip from Examples 22 is used, wherein, unlike Example 21, the adhesive layer was volumpandiert in the oven for 30 s at 160 ° C between the two liners, ie to an expansion of 100%. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a thickness of 1 15 μηη, a density of 735 kg / m ³ and a roughness R _a of less than 10 μηη on.

Example 25:

A pressure-sensitive adhesive strip based on a polyacrylate-styrene block copolymer (SBC) blend was prepared according to the invention.

For this purpose, a mixture was prepared comprising 42.425 wt .-% base polymer P1 as described above under Example 21, 37.5 wt.% Resin Dertophene T and 20 wt .-% Kraton D 1 1 18. Dertophene T is a terpene phenolic resin (Softening point 1 10 ° C, M _w = 500 to 800 g / mol, PD = 1.50) of DRT resins. Kraton 1 18 is a styrene-butadiene-styrene block copolymer from Kraton Polymers with 78% by weight of 3 block, 22% by weight of 2 block, a block polystyrene content of 33% by weight and one Molecular weight M _{w of} the 3-block portion of 150,000 g / mol. The addition of gasoline set a solids content of 38% by weight. The mixture of polymer and resin was stirred until the resin was visibly completely dissolved. Subsequently, 0.075% by weight of the covalent crosslinker Erysis GA 240 (N, N, N ', N'-tetrakis (2,3-epoxypropyl) -m-xylene-α, α'-diamine) from Emerald Performance Materials was added , The weight fractions of the dissolved constituents are each based on the dry weight of the resulting solution. The mixture was unexpanded for 15 minutes with the addition of 0.8% by weight Microballoons Expancel 920 DU20 stirred at room temperature (20 ° C). The resulting mixture was then spread with a brush on a PET liner equipped with a separating silicone in such a layer thickness, that after the subsequent evaporation of the solvent at 100 ° C for 15 min and thus drying of the mass layer, a mass order of 130 g / m ² .

Subsequently, a second PET liner was laminated to the free surface of the prepared and dried layer of adhesive, and then the adhesive layer was partially foamed in the oven for 20 s at 160 ° C between the two liners. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a foaming degree of 40%, a thickness of 105 μm, a density of 963 kg / m ³ and a roughness R _a of less than 10 μm , By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained. Comparative Examples 26 and 27:

The pressure-sensitive adhesive strip of Example 25 is used as Comparative Example 26, but before foaming. The adhesive layer (without PET liner) had a thickness of 127 μm, a density of 1024 kg / m ³ and a roughness R _a of less than 10 μm.

As a comparative example 27, the pressure-sensitive adhesive strip of Example 25 is used, wherein, unlike Example 24, the adhesive layer was volumpandiert in the oven for 30 seconds at 160 ° C between the two liners, ie to an expansion of 100%. After cooling at room temperature (20 ° C), the adhesive layer (without PET liner) had a thickness of 149 μηη, a density of 872 kg / m ³ and a roughness R _a of less than 10 μηη on.

Table 1 below shows the shock resistance (breakdown strengths) and the bond strengths on steel of the single-layer pressure-sensitive adhesive strips according to the invention (examples) and the non-inventive single-layer pressure-sensitive adhesive strips as comparative examples. Trial Base MB Type and Expansion Adhesive Dupont Droptower polymer content grade (%) (N / cm) (z) (J) (J, Fmax)

Example 1 SBC 3.3% by weight 76 11.26 0.66 0.56; - 920DU20

Comparative SBC 3.3% by weight 0 14.70 0.49 0.35; - Example 2 920DU20

Comparative SBC 3.3% by weight 100 11.11 0.35 0.35; - Example 3 920DU20

Example 4 SBC 1% by weight 44 9.83 0.37 0.49; - 920DU20

Example 5 SBC 1% by weight 49 9.47 0.34 0.50; - 920DU20

Comparative SBC 1% by weight 0 11.91 0.20 0.25; - Example 6 920DU20

Comparative SBC 1% by weight 100 9.27 0.44 0.52; - Example 7 920DU20

Comparative SBC 1 wt% -88 10.16 0.42 0.33; - Example 8 920DU20

Example 9 SBC 1.5 wt% 29 12.92 0.52 0.48; - 920DU40

Example 10 SBC 1.5% by weight 69 12.10 0.59 0.71; -920DU40

Comparative SBC 1.5% by weight 0 16.09 0.35 0.29; - Example 11 920DU40

Comparative SBC 1.5% by weight 100 11.83 0.54 0.58; - Example 12 920DU40

Comparative SBC 1.5 wt% -12 11.59 0.50 0.51; - Example 13 920DU40

Example 14 SBC 1.5 wt% 27 - 0.13 0.129; - 920DU20

Example 15 SBC 1.5 wt% 38 - 0.10 0.131; - 920DU20

Example 16 SBC 1.5 wt% 59 - 0.13 0.152; - 920DU20

Example 17 SBC 1.5% by weight 73 - 0.19 0.171; - 920DU20

Example 18 SBC 1.5 wt% 86 - 0.18 0.161; - 920DU20

Comparative SBC 1.5 wt% 0 - 0.10 0.073; - Example 19 920DU20

Comparative SBC 1.5 wt% 100 - 0.17 0.066; - Example 20 920DU20

Comparative SBC 1.5% by weight -62 - 0.15 0.033; - Example 21 920DU20

Example 22 P1 2 wt% 78 - - 0.91; 1153

920DU20

Comparative P1 2% by weight 0-0.57; 1113 example 23 920DU20

Comparative P1 2 wt% 100 - - 0.74; 1086 example 24 920DU20

Example 25 P1 / SBC 0.8 wt% 40 - - 1.16; 2288

920DU20 Trial Base MB Type and Expansion Adhesive Dupont Droptower polymer content grade (%) (N / cm) (z) (J) (J; Fmax)

Comparative P1 / SBC 0.8 wt% 0 - - 0.42; 1770 example 26 920DU20

Comparative P1 / SBC 0.8 wt% 100 - - 0.80; 1930 example 27 920DU20

Table 1: Shock resistance and bond strengths of single-layer pressure-sensitive adhesive strips according to the invention and comparative examples. The exemplary pressure-sensitive adhesive strips show that partially foamed self-adhesive compositions surprisingly have comparable and often even improved shock resistance compared with the corresponding pressure-sensitive adhesive strips with fully-foamed self-adhesive composition from the comparative examples. Thus, the impact strength in the z-direction (breakdown strength) is comparable or often even improved. Particularly at a degree of foaming of about 65 to about 90%, such as from about 70 to about 80%, show - regardless of the base polymer used, micro balloon type and content as well as the application order - again significantly improved full-blown to breakthrough toughness. Moreover, when using a blend of a polyacrylate with a styrene block copolymer in the pressure-sensitive adhesive strip, a significantly improved breakthrough toughness compared to the corresponding pressure-sensitive adhesive strip with full foaming was already evident at a foaming degree of only about 40%, cf. Example 25 with Comparative Example 27.

In particular, the pressure-sensitive adhesive strips with a very low application rate of 10 g / m ² prove to be advantageous with respect to the shock resistance to a suitable degree of partial foaming over the corresponding fully foamed pressure-sensitive adhesive strip, cf. Examples 17 and 18 with Comparative Example 20. This is attributed, without being bound to this theory, in particular to the fact that the microballoons obviously form a monolayer in the partially foamed self-adhesive layer (see FIGS. 5a and 6a). On the other hand, with such a small application, even the comparatively small unexpanded Expancel 920DU20 microballoons used often protrude from the adhesive after full foaming, which is undesirable according to the invention. In addition, the exemplary PSA strips with teilgeschäumter self-adhesive compared to the corresponding pressure-sensitive adhesive strips with fully foamed self-adhesive from the comparative examples typically have improved bonding strengths, ie bond strengths.

By contrast, the unfoamed and over-expanded pressure-sensitive adhesive strips of the comparative examples fall off with respect to the impact resistance compared with the corresponding fully-foamed pressure-sensitive adhesive strips. The production of pressure-sensitive adhesive strips according to the invention is also described below, each of which is composed of a permanent support coated on both sides with a self-adhesive layer SK1 based on a vinylaromatic block copolymer adhesive partially foamed with microballoons (MBs). The adhesive solution used in the preparation of the self-adhesive layers, the micro balloon type (Expancel 920DU20) and content (1, 5 wt .-%) and the application rate (10 g / m ² ) respectively correspond to Examples 14 to 18, unless stated otherwise. The type and thickness of the carrier were varied.

Examples 28 to 30:

The unexpanded microballoon-containing mixture was in each case coated with a brush on a PET liner, equipped with a separating silicone, in a compound application of 10 g / m ² , then the solvent was evaporated at 100 ° C for 15 min and dried so the mass layer ,

A transparent etched PET film having a thickness of 36 μm (Example 28), a transparent etched PET film having a thickness of 23 μm (Example 29) or a black PET film were applied to the free surface of the adhesive layer thus prepared and dried Thickness of 12 μηη (Example 30) laminated.

On the second surface of the free surface of a second identically prepared, also dried adhesive layer (also in a order of 10 g / m ² ) was laminated, so that a symmetrical three-layer composite of the inner film layer and two provided with liners adhesive layers resulted. After drying, the adhesive layers were partially foamed in the oven for 15 s at 138 ° C between the two liners. After cooling at room temperature (20 ° C), the adhesive layer had a degree of foaming of 88% and a density of 720 kg / m ³ (Example 28), a degree of foaming of 78% and a density of 750 kg / m ³ (Example 29). or a degree of foaming of 94% and a density of 700 kg / m ³ (Example 30). The thickness of the three-layer system (without PET liner) was 70 μηη (Example 28), 54 μηη (Example 29) and 44 μηη (Example 30). By punching out, a pressure-sensitive adhesive strip according to the invention of the desired dimensions was obtained in each case.

Comparative Examples 31 to 33:

As Comparative Examples 31 to 33 serve the pressure-sensitive adhesive strips of Examples 28 to 30, but before foaming. The adhesive layers each had a density of 1000 kg / m ³ . The pressure-sensitive adhesive strips (without PET liner) had a thickness of 62 μm (comparative example 31), 52 μm (comparative example 32) and 36 μm (comparative example 33). By punching out a pressure-sensitive adhesive strip of the desired dimensions was obtained in each case. Example 34:

The pressure-sensitive adhesive strip from Example 28 serves as Example 34, but instead of the transparent etched PET film, a colorless polyurethane film (PU film) with a thickness of 30 μm was used. After cooling at room temperature (20 ° C), the adhesive layer had a foaming degree of 69% and a density of 780 kg / m ³ . The thickness of the three-layer system (without PET liner) was 57 μηη. By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained.

Comparative Example 35

The pressure-sensitive adhesive strip of Example 34 is used as Comparative Example 35, but before foaming. The adhesive layer had a density of 1000 kg / m ³ . The pressure-sensitive adhesive strip (without PET liner) had a thickness of 54 μm. By punching a pressure-sensitive adhesive strip of the desired dimensions was obtained. Example 36:

The pressure-sensitive adhesive strip from Example 28 serves as Example 36, but instead of the transparent, etched PET film, a polyethylene foam core (PE foam core) with a thickness of 70 μm was used. After cooling at room temperature (20 ° C), the adhesive layer had a foaming degree of 78% and a density of 750 kg / m ³ . The thickness of the three-layer system (without PET liner) was 107 μm. By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained. Example 37:

The pressure-sensitive adhesive strip from example 36 serves as example 37, but the two adhesive layers were characterized by a mass application of in each case 35 g / m ² . After cooling at room temperature (20 ° C), the adhesive layer had a foaming degree of 81% and a density of 740 kg / m ³ . The thickness of the three-layer system (without PET liner) was 165 μηη. By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained.

Comparative Example 38

The pressure-sensitive adhesive strip of Example 36 is used as Comparative Example 38, but before foaming. The adhesive layer had a density of 1000 kg / m ³ . The pressure-sensitive adhesive strip (without PET liner) had a thickness of 97 μm. By punching a pressure-sensitive adhesive strip of the desired dimensions was obtained.

Example 39:

The pressure-sensitive adhesive strip from Example 28 serves as Example 39, but instead of the transparent, etched PET film, a film based on styrene block copolymer (SBC) with a thickness of 70 μm was used. Further, instead of 15 s at 138 ° C for 20 s at 150 ° C partially foamed. After cooling at room temperature (20 ° C), the adhesive layer had a foaming degree of 78% and a density of 750 kg / m ³ . The thickness of the three-layer system (without PET liner) was 100 μηη. By punching an inventive pressure-sensitive adhesive strip of the desired dimensions was obtained. Comparative Examples 40 to 42:

The pressure-sensitive adhesive strip of Example 39, but before foaming, serves as comparative example. The adhesive layer had a density of 1000 kg / m ³ . The pressure-sensitive adhesive strip (without PET liner) had a thickness of 92 μm. By punching a pressure-sensitive adhesive strip of the desired dimensions was obtained.

As Comparative Examples 41 and 42, the pressure-sensitive adhesive strip of Example 39, but each was foamed for 20 s at 170 ° C in each case. In Comparative Example 42, a film based on styrene block copolymer having a smaller thickness of 50 μm was also used. The adhesive layer each had a density of 680 kg / m ³ . The pressure-sensitive adhesive strip had a thickness of 1 1 1 μηη (Comparative Example 41) or 100 μηη (Comparative Example 42). By punching out a pressure-sensitive adhesive strip of the desired dimensions was obtained in each case.

Table 2 below shows the shock resistances (breakdown strengths) and the fracture patterns which are registered when carrying out the Dropto test (as described in the measuring method section), the three-layer pressure-sensitive adhesive strips according to the invention (examples) and the non-inventive three-layer pressure-sensitive adhesive strips as comparative examples.

The properties of the three-layer pressure-sensitive adhesive strips of the examples and comparative examples from Table 2 allow the same conclusions as in the single-layer pressure-sensitive adhesive strips from Table 1. Thus, in particular, the three-layer pressure-sensitive adhesive strips with teilgeschäumten self-adhesive compositions compared to the corresponding pressure-sensitive adhesive strips with fully foamed self-adhesive surprisingly comparable or have improved shock resistance (breakdown strengths). Furthermore, the pressure-sensitive adhesive strips with unfoamed self-adhesive compositions clearly fall with regard to the impact strength with respect to the corresponding pressure-sensitive adhesive strips with partially foamed self-adhesive compositions.

^" Abelle 2: shock resistance and Bruchbilc he inventive three-layered

Pressure-sensitive adhesive strips and of comparative examples.

A comparison of Examples 36 and 37 also shows that in a size application of the partially foamed self-adhesive layers SK1 of only 10 g / m ^2, a three-layer pressure-sensitive adhesive strip can be provided which has a shock resistance comparable to the shock resistance of a corresponding pressure-sensitive adhesive strip with a partially foamed self-adhesive layers SK1 of 35 g / m ² (see in particular the values of the Dropto test). Surprisingly, thinner partially-foamed self-adhesive layers SK1 do not lead to worse shock values. In addition, the experiments with increasing degree of foaming of the self-adhesive composition layer in the droplet test show a tendency to foam-splitting the self-adhesive composition layer instead of the adhesion failure (see the pressure-sensitive adhesive strips containing a PET, PU or SBC support). It is also interesting to note that the partial expansion of the outer layers (self-adhesive layers) already leads to the fact that the overall structure of the anchoring break, ie the break between self-adhesive layer and PE foam carrier, merges into a splitting of the PE foam carrier. Obviously, the partial foaming of the self-adhesive layers leads to an improvement of their anchoring with the PE foam carrier. Example 36 also shows that even a coating of the partially foamed self-adhesive layers SK1 of only 10 g / m ² provides a three-layer pressure-sensitive adhesive strip with polyethylene foam carrier whose fracture pattern in the Droptowertest in a splitting of the polyethylene foam (the same is here at a mass order of 35 g / m ² the case, see example 37).

Incidentally, the tests also show that in the droplet test, the fracture pattern depends not only on the degree of foaming of the self-adhesive layers, but also on the nature of the carrier used. Examples 29, 36 and 39 show that with the same degree of foaming (and same chemical composition) of the self-adhesive layers, it is conceivable to split the partially foamed self-adhesive layer or the foamed carrier, or else an adhesion break, depending on the carrier used. The desired fracture pattern can thus be adjusted both on the degree of foaming, as well as on the carrier used. Test Methods

All measurements were, unless otherwise stated, at 23 ° C and 50% rel. Humidity carried out. The mechanical and adhesive data were determined as follows:

Tensile strength, tear strength (tensile strength) and elongation at break (measurement method R1)

The elongation at break, the tear strength and the tensile strength, for example of a film carrier, were determined in accordance with DIN EN ISO 527-3 using a Sample strip, specimen Type 2, measured with a width of 20 mm at a separation rate of 100 mm per minute. The initial distance of the clamps was 100 mm. The test climate was 23 ° C and 50% rel. Humidity.

peel force

The peel force (stripping force or stripping tension) was determined using a pressure-sensitive adhesive strip measuring 50 mm in length * 20 mm in width with a grip area which was not adhesive at the upper end. The pressure-sensitive adhesive strip was glued between two congruent steel plates with a dimension of 50 mm 30 mm with a contact pressure of 50 Newtons each. The steel plates each have at their lower end a bore for receiving an S-shaped steel hook. The lower end of the steel hook carries another steel plate over which the test arrangement can be fixed for measurement in the lower jaw of a tensile testing machine. The bonds were stored for 24 hours at + 40 ° C. After reconditioning to room temperature (20 ° C.), the pressure-sensitive adhesive strip was removed at a drawing speed of 1000 mm per minute parallel to the bond plane and without contact with the edge regions of the two steel plates. The required peel force was measured in Newton (N). The average value of the stripping stress values (in N per mm ² ), measured in the range in which the pressure-sensitive adhesive strip has peeled off on a bond length between 10 mm and 40 mm from the steel substrates, is indicated. adhesive power

The determination of the bond strength (according to AFERA 5001) was carried out as follows. As a defined primer, galvanized steel sheet with a thickness of 2 mm (supplied by Rocholl GmbH) was used. The pressure-sensitive adhesive strip to be examined was cut to a width of 20 mm and a length of about 25 cm, provided with a handling section and immediately thereafter pressed on the selected primer five times with a steel roller of 4 kg at a feed rate of 10 m / min. Immediately thereafter, the pressure-sensitive adhesive strip was at an angle of 180 ° from the primer with a Zugprüfungsgerät (Zwick) at a speed v = 300 mm / min deducted and measured at room temperature (20 ° C) required force. The measured value (in N / cm) is the average of three individual measurements.

thickness

The thickness e.g. A pressure-sensitive adhesive strip, an adhesive layer or a carrier layer can be determined using commercially available thickness measuring devices (probe test devices) with accuracies of less than 1 μηη deviation. The thickness of an adhesive layer is typically determined by determining the thickness of a section of such a layer applied to a carrier or liner, with respect to its length and width, minus the (known or separately determinable) thickness of a section of equal dimensions of the carrier or liner used , If variations in thickness are detected, the mean value of measurements is given at at least three representative points, that is to say in particular not measured by nicks, folds, specks and the like. In the present application, the thickness measurement is made using the precision thickness gauge Mod. 2000 F, which has a circular probe with a diameter of 10 mm (plane). The measuring force is 4 N. The value is read off 1 s after loading. density

The density of a layer, e.g. An adhesive layer is determined by quotient formation from the application of the composition and the thickness of the layer applied to a carrier or liner.

The application of a layer such as e.g. An adhesive layer can be determined by determining the mass of a section, defined with respect to its length and width, of such a layer applied to a carrier or liner minus the (known or separately determinable) mass of a section of equal dimensions of the carrier or liner used.

The thickness of a layer, such as an adhesive layer, can be determined by determining the thickness of a section of such a layer applied to a carrier or liner, with respect to its length and width, minus the (known or separately determinable) thickness of a section of equal dimensions of the carrier used or Liners are determined. The thickness of the layer can be determined using commercially available thickness measuring devices (probe testing devices) with accuracies of less than 1 μm deviation. If variations in thickness are detected, the mean value of measurements is given at at least three representative points, that is to say in particular not measured by nicks, folds, specks and the like. In the present application, the thickness measurement is made using the precision thickness gauge Mod. 2000 F, which has a circular probe with a diameter of 10 mm (plane). The measuring force is 4 N. The value is read off 1 s after loading. DuPont test in the z-direction (breakdown strength)

From the adhesive tape to be examined, a square, frame-shaped sample was cut out (external dimensions 33 mm × 33 mm, web width 2.0 mm, internal dimensions (window cutout) 29 mm × 29 mm). This sample was glued to a PC frame (external dimensions 45 mm x 45 mm, web width 10 mm, internal dimensions (window cut-out) 25 mm x 25 mm, thickness 3 mm). On the other side of the tape, a PC window of 35 mm x 35 mm was glued. The gluing of PC frames, adhesive tape frames and PC windows took place in such a way that the geometric centers and the diagonals overlap each other (corner-to-corner). The bond area was 248 mm ² . The bond was pressed at 248 N for 5 s and conditioned for 24 hours at 23 ° C / 50% relative humidity.

Immediately after storage, the adhesive composite of PC frame, adhesive tape and PC window with the protruding edges of the PC frame was clamped in a sample holder such that the composite was level and the PC window was below the frame. The sample holder was then inserted centrically into the intended receptacle of the "DuPont Impact Tester." The 190 g impact head was inserted so that the circular impact geometry with a diameter of 20 mm was centered and flush on the window side of the PC window.

On the thus arranged assembly of sample holder, sample and impact head, a weight guided on two guide rods with a mass of 150 g was vertically dropped from a height of 5 cm (measuring conditions 23 ° C., 50% relative humidity). The height of the fall weight was increased in 5 cm increments until the introduced Impact energy destroyed the sample by the impact load and the PC window broke away from the PC frame.

To compare experiments with different samples, the energy was calculated as follows:

E [J] = height [m] ^* weight [kg] ^* 9,81 m / s ²

Five samples per product were tested and the energy average was reported as a breakdown index.

Droptower test method (breakdown strength)

The Droptower test method as an instrumented drop test also serves to measure the breakdown strength.

From the tape to be examined, a square, frame-shaped sample was cut out (outer dimensions 33 mm x 33 mm, web width 2.0 mm, internal dimensions (window cut-out) 29 mm x 29 mm). This specimen was bonded to an acetone-cleaned steel frame (external dimensions 45mm x 45mm, web width 10mm, internal dimensions (window cutout) 25mm x 25mm). On the other side of the tape, an acetone-cleaned steel window (external dimensions 35mm x 35mm) was bonded. The gluing of steel frames, adhesive tape frames and steel windows took place in such a way that the geometric centers and the diagonals overlap each other (corner-to-corner). The bond area was 248 mm ² . The bond was pressed at 248 N for 5 s and conditioned for 24 hours at 23 ° C / 50% relative humidity.

Immediately after storage, the test specimen was inserted into the specimen holder of the instrumented box in such a way that the composite was horizontal, with the steel window directed downwards. The measurement was instrumental and automatic using a load weight of 5 kg and a drop height of 10 cm. Due to the introduced kinetic energy of the load weight, the bond was destroyed by breakage of the adhesive tape between the window and the frame, the force being recorded by a piezoelectric sensor in the s cycle. The corresponding software accordingly gave the graph for the force-time curve after the measurement, from which itself determine the maximum force F _ma x. Shortly before the collision of the rectangular impact geometry with the window, the speed of the drop weight was determined with two light barriers. Assuming that the introduced energy is large compared to the impact strength of the bond, the work of the bond was determined from the force curve, the required time to detachment and the speed of the drop weight until complete detachment, ie the work of detachment. Five specimens of each specimen were tested, the final impact value being the average of the work done or the maximum force of these five specimens.

Cross impact strength (x, y plane)

From the tape to be tested, a square, frame-shaped sample was cut out (outer dimensions 33 mm × 33 mm, web width 2.0 mm, inner dimensions (window cutout) 29 mm × 29 mm). This sample was glued to a PC frame (external dimensions 45 mm x 45 mm, web width 10 mm, internal dimensions (window cut-out) 25 mm x 25 mm, thickness 3 mm). On the other side of the double-sided adhesive tape, a PC window of 35 mm x 35 mm was glued. The gluing of PC frames, adhesive tape frames and PC windows took place in such a way that the geometric centers and the diagonals overlap each other (corner-to-corner). The bond area was 48 mm ² . The bond was pressed at 248 N for 5 s and conditioned for 24 hours at 23 ° C / 50% relative humidity.

Immediately after storage, the adhesive composite of PC frame, adhesive tape and PC disk with the protruding edges of the PC frame was clamped in a sample holder in such a way that the composite was oriented vertically. The sample holder was then inserted centrically into the intended receptacle of the "DuPont Impact Tester." The 300 g impact head was inserted in such a way that the rectangular impact geometry measuring 20 mm x 3 mm was centered on the upward facing end of the PC window and flush.

On the thus arranged assembly of sample holder, sample and impact head, a weight guided on two guide rods with a mass of 150 g was vertically dropped from a height of 5 cm (measuring conditions 23 ° C., 50% relative humidity). The height of the drop weight was increased in 5 cm increments until the introduced Impact energy destroyed the sample by the cross impact load and the PC window broke away from the PC frame.

E [J] = height [m] ^* weight [kg] ^* 9,81 kg / m ^* s ²

Five samples per product were tested and the energy average was reported as the index of transverse impact strength.

diameter

The determination of the average diameter of the cavities formed by the microballoons in a self-adhesive composition layer takes place on the basis of cryobreak edges of the pressure-sensitive adhesive strip in the scanning electron microscope (SEM) at 500 × magnification. The diameter of the microballoons of the self-adhesive layer to be examined is graphically determined from the micrographs of the adhesive strips to be examined, the arithmetic average of all diameters determined in the 5 SEM images being the mean diameter of the cavities of the microballoons formed by the microballoons Self-adhesive layer in the context of the present application represents. The diameters of the microballoons to be seen on the recordings are determined graphically in such a way that from the SEM images for each individual microballoon of the self-adhesive composition layer to be examined its maximum extent is taken in any (two-dimensional) direction and is regarded as its diameter.

Static glass transition temperature T _g

Glass transition points - referred to interchangeably as glass transition temperatures - are reported as a result of Dynamic Scanning Calorimetry (DSC) measurements according to DIN 53 765, in particular Sections 7.1 and 8.1, but with uniform heating and cooling rates of 10 K / min in all Heating and cooling steps (compare DIN 53 765, section 7.1, note 1). The sample weight is 20 mg.

DACP

5.0 g of test substance (the adhesive resin sample to be investigated) are weighed into a dry sample glass and mixed with 5.0 g of xylene (mixture of isomers, CAS [1330-20-7],> 98.5%, Sigma-Aldrich # 320579 or similar). added. At 130 ° C, the test substance is dissolved and then cooled to 80 ° C. Any escaped xylene is filled in with additional xylene, so that again 5.0 g of xylene are present. Subsequently, 5.0 g of diacetone alcohol (4-hydroxy-4-methyl-2-pentanone, CAS [123-42-2], 99%, Aldrich # 1-141544 or equivalent) are added. The sample glass is shaken until the test substance has completely dissolved. For this purpose, the solution is heated to 100 ° C. The sample glass with the resin solution is then introduced into a cloud point measuring device Chemotronic Cool from Novomatics and tempered there to 1 10 ° C. With a cooling rate of 1, 0 K / min is cooled. The cloud point is optically detected. For this purpose, the temperature is recorded at which the turbidity of the solution is 70%. The result is given in ° C. The lower the DACP value, the higher the polarity of the test substance.

MMAP

In a dry sample glass, 5.0 g of test substance (the adhesive resin sample to be examined) are weighed and mixed with 10 mL of dry aniline (CAS [62-53-3],> 99.5%, Sigma-Aldrich # 51788 or equivalent) and 5 mL dry methylcyclohexane (CAS [108-87-2],> 99%, Sigma-Aldrich # 300306 or equivalent). The sample glass is shaken until the test substance has completely dissolved. For this purpose, the solution is heated to 100 ° C. The sample glass with the resin solution is then introduced into a cloud point measuring device Chemotronic Cool from Novomatics and tempered there to 1 10 ° C. With a cooling rate of 1, 0 K / min is cooled. The cloud point is optically detected. For this purpose, the temperature is recorded at which the turbidity of the solution is 70%. The result is given in ° C. The lower the MMAP value, the higher the aromaticity of the test substance. Softening temperature

The softening temperature, e.g. of tackifier resins, polymers or polymer blocks is carried out according to the relevant methodology known as Ring & Ball and standardized according to ASTM E28.

Gel permeation chromatography (GPC)

(i) Mp: GPC is suitable as a metrological method for determining the molar mass of individual polymer modes in mixtures of different polymers. For the purposes of this invention usable by living anionic polymerization block copolymers, the molecular weight distributions are typically sufficiently narrow, so that polymer modes that can be assigned triblock copolymers, diblock copolymers or multiblock copolymers, sufficiently dissolved from each other in the Elugramm occur. It is then possible to read the peak molecular weight for the individual polymer modes from the elugrammen. Peak molecular weight MP are using

Gel permeation chromatography (GPC) determined. The eluent used is THF. The measurement takes place at 23 ° C. The precolumn used is PSS-SDV, 5 μ, 10 ³ A, ID 8.0 mm × 50 mm. For separation, the columns PSS-SDV, 5 μ, 10 ³ Ä and 10 ⁴ Ä and 10 ⁶ Ä are used each with ID 8.0 mm x 300 mm. The sample concentration is 4 g / l, the flow rate is 1, 0 ml per minute. It is measured against PS standards (μ = μηη, 1 λ = 10 ^"10 m).

(ii) M _n , M _w , PD: the data on the number average molecular weight M _n , the weight average molecular weight Mw and the polydispersity PD refer to the determination per

Gel permeation chromatography. The determination is carried out on 100 μΙ_ clear filtered sample (sample concentration 1 g / L). The eluent used is tetrahydrofuran with 0.1% by volume of trifluoroacetic acid. The measurement takes place at 25 ° C. As precolumn a column type PSS-SDV, 5 μ, 10 ³ A, ID 8.0 mm x 50 mm is used. For separation, the columns of the type PSS-SDV, 5 μ, 10 ³ A and 10 ⁵ A and 10 ⁶ A are used each with ID 8.0 mm x 300 mm (columns from Polymer Standards Service, detection by means of differential refractometer Shodex RI71) , The flow rate is 1, 0 ml_ per minute. The calibration is carried out against PMMA standards (polymethyl methacrylate calibration) or (synthetic) rubbers against polystyrene. Resilience or elasticity

To measure the resilience, the film carriers were stretched by 100%, held in this stretch for 30 s and then relaxed. After a waiting time of 1 min, the length was measured again.

The recovery is calculated as follows:

RV = ((L100 - country) / Lo) ^* 100 with RV = recovery in%

L.100: Length of the film carrier after stretching by 100%

Lo: Length of the film carrier before stretching

Lend: length of the film carrier after the relaxation of 1 min.

The resilience corresponds to the elasticity.

Modulus of elasticity The modulus of elasticity indicates the mechanical resistance which a material opposes to elastic deformation. It is determined as the ratio of the required stress σ to the strain ε achieved, where ε is the quotient of the change in length AL and the length Lo in the Hooke deformation regime of the test specimen. The definition of the modulus of elasticity is, for example, in the paperback of physics explained (H. Stoecker (ed.), Paperback of physics, 2nd ed., 1994, Harri German publisher, Frankfurt, pp 102 - 1 10).

To determine the modulus of elasticity of a film, the tensile elongation behavior on a type 2 test piece (rectangular 150 mm long and 15 mm wide film test strip) according to DIN EN ISO 527-3 / 2/300 with a test speed of 300 mm / min, a clamping length of 100 mm and a pre-load of 0.3 N / cm, wherein the test strip was cut to determine the data with sharp blades. A tensile testing machine from Zwick (model Z010) was used. The tensile elongation behavior was measured in the machine direction (MD). A 1000 N (Zwick Roell type Kap-Z 066080.03.00) or 100 N (Zwick Roell type Kap-Z 0661 10.03.00) Load cell. The modulus of elasticity was determined graphically from the measurement curves by determining the slope of the characteristic curve of the Hoverian behavior in the beginning of the curve and expressed in GPa. Surface roughness R _a

The surface roughness R _a was determined by means of laser triangulation.

The PRIMOS system used consists of a lighting unit and a recording unit. The lighting unit projects lines onto the surface using a digital micro-mirror projector. These projected, parallel lines are deflected or modulated by the surface structure. For the registration of the modulated lines, a, arranged at a certain angle, the so-called triangulation angle, CCD camera is used.

Measurement field size: 14.5 x 23.4 mm ²

Profile length: 20.0 mm

Surface roughness: 1, 0 mm from the edge (Xm = 21, 4 mm, Ym = 12.5 mm)

Filtering: polynomial filter 3rd order

The surface roughness R _a represents the average height of the roughness, in particular the average absolute distance from the center line (regression line) of the roughness profile within the evaluation range. In other words, R _a is the arithmetic mean roughness, ie the arithmetic mean of all profile values of the roughness profile.

Relevant measuring devices can be purchased from GFMesstechnik GmbH in Teltow, among others.

Claims

claims

Pressure-sensitive adhesive strip which comprises at least one layer SK1, preferably exactly one layer SK1, of a self-adhesive mass partially foamed with microballoons, the degree of foaming of the layer SK1 being at least 20% and less than 100%.

Pressure-sensitive adhesive strip according to Claim 1,

characterized in that

the pressure-sensitive adhesive strip can be detached again by stretching stretching substantially in the bonding plane residue-free and non-destructive.

Pressure-sensitive adhesive strip according to Claim 1 or 2,

characterized in that

the pressure-sensitive adhesive strip consists of the layer SK1.

Pressure-sensitive adhesive strip according to Claim 1 or 2,

characterized in that

the pressure-sensitive adhesive strip comprises a layer SK1 and furthermore a layer T comprising a carrier, in particular a film carrier, wherein the layer SK1 is arranged on one of the surfaces of the carrier layer T.

Pressure-sensitive adhesive strip according to Claim 4,

characterized in that

the pressure-sensitive adhesive strip furthermore comprises a layer SK2 of a self-adhesive mass which is arranged on the surface of the carrier layer T facing the layer SK1, wherein the layer SK2 is preferably based on a mass partially foamed with microballoons, the degree of foaming of the layer SK2 being at least 20% and less than 100%.

Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the degree of foaming of the self-adhesive layers SK1 and / or SK2, preferably of the two layers SK1 and SK2, each independently of one another, 25 to 98%, more preferably 35 to 95%, even more preferably 50 to 90% and especially 65 to 90%, such as 70 to 80%.

7. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the mean diameter of the voids formed by the microballoons in the self-adhesive layers SK1 and / or SK2, preferably in each of the two layers SK1 and SK2 is independently of one another less than 20 μm, more preferably not more than 15 μm.

8. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2 each independently have a thickness of less than 20 μm, more preferably of at most 15 μm.

9. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2 each independently, have a mass application (in g / m ² ), which is less than the average diameter of the voids formed by the microballoons (in μηη) in the corresponding Self-adhesive composition layer, wherein the ratio of the order of application (in g / m ² ) to the mean diameter of the cavities (in μηη) of the self-adhesive composition layers formed by the microballoons is preferably 0.6-0.9, and in particular 0.7-0.8.

10. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2, have a monolayer of microballoons.

1 1. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the self-adhesive layers SK1 and / or SK2, preferably the two layers SK1 and SK2, each independently of one another, have a surface roughness R _a of less than 15 μηι, preferably of less than 10 μηη, more preferably less than 5 μηη, more preferably less than 3 μηη, in particular less than 2 μηη, such as less than 1 μηη.

12. Pressure-sensitive adhesive strip according to one of claims 4 to 10,

characterized in that

the film support layer T is inextensible, wherein the film support layer T preferably has a thickness of 5 to 125 μηη, more preferably from 5 to 40 μηη and in particular from 5 to less than 10 μηη, such as 6 μηη having.

13. Pressure-sensitive adhesive strip according to one of claims 4 to 10,

characterized in that

the film support layer T is stretchable, wherein the film support layer T preferably has a thickness of 50 to 150 μηη, more preferably from 60 to 100 μηη and in particular from 70 μηη to 75 μηη, such as of 70 μηη having.

14. Pressure-sensitive adhesive strip according to claim 13,

characterized in that

the stretchable film backing layer T is a vinyl aromatic block copolymer based film, preferably styrene block copolymer, which film is preferably unfoamed.

15. Pressure-sensitive adhesive strip according to one of the preceding claims,

characterized in that

the self-adhesive layers SK1 and / or SK2, preferably both layers SK1 and SK2, are based on a vinyl aromatic block copolymer composition or acrylate composition, and in particular on a vinyl aromatic block copolymer composition.

16. A process for the preparation of a pressure-sensitive adhesive strip according to one of the preceding claims, wherein the partially foamed with microballoon self-adhesive layers

SK1 and optionally SK2 are prepared by heat-treating the respective self-adhesive layers containing unexpanded microballoons at a temperature suitable for foaming for a time such that the desired degree of partial foaming is achieved after the subsequent cooling of the layers.

17. Use of a pressure-sensitive adhesive strip according to one of claims 1 to 15 for the bonding of components such as in particular batteries and electronic devices such as in particular mobile devices, such as mobile phones.