MXPA99005950A - Adhesive for secure topical attachment to the skin and comfortable removal - Google Patents

Abstract

The present invention relates to a combination of a substrate with topical adhesives for attachment to the skin. In particular the present invention relates to a combination of a substrate with a topical adhesive which can be employed for attachment to the skin in the area were absorption of bodily liquids is desired. The combination provides secure attachment and is pleasing to the skin upon application, yet causes no discomfort upon removal. This is achieved by selecting the chemical composition and rheological characteristics of the topical adhesives and the physical characteristics of the substrate on which the topical adhesive is applied.

Description

ADHESIVE FOR TOPIC FIXATION SAFE TO THE SKIN AND PROPER REMOVAL FIELD OF THE INVENTION The present invention relates to a combination of a substrate with a topical adhesive for attachment to the skin. In particular, the present invention relates to a combination of a substrate with a topical adhesive, which can be used for fixing to the skin in the area where the absorption of body fluids is desired, particularly for the adhesion of sanitary napkins, pantiprotectors, adult incontinence products or exudation pads. The combination provides secure fixation and is suitable for application on the skin, yet does not cause discomfort when removed. This is achieved by selecting the chemical composition and rheological characteristics of the topical adhesives and with the physical characteristics of the substrate on which the topical adhesive is applied, particularly the viscous modulus "G" of the topical adhesive and the stiffness S of the combination of substrate with the topical adhesive.

BACKGROUND OF THE INVENTION The general prior art in the field of topical adhesives for fixing to the skin was developed particularly in the field of relief bandages, plasters and bandages. However, these articles are typically applied in an emergency situation, where, for example, a wound has occurred on the wearer's skin and absorption of body fluids emanating from the wound is desired. In this context, aspects of the performance of the absorbent article such as the use and easy application and easy removal without pain, discretion is subordinated to criteria such as sterility, healing protection, mechanical protection of the wound. Also the absorbent articles that protect the wound are mainly adhered to the areas of the skin where the body hair can be removed before the application of the article or where little or no hair grows. The present invention relates to the combination of a substrate with a topical adhesive, which is particularly useful for absorbent articles for the absorption of body fluids, which naturally emanate from the body without a wound. For example, to fix sanitary pads or pantiliners in the genitourinary region. Also, devices that are used, for example, in the genital region or the sweat pads that are used within the region of a person's armpit, can suitably employ the adhesive of the present invention. Topical adhesives that are used for absorbent articles have been generally disclosed in the invention registry established by the law of the States.

United H1602 or WO 96/33683. Some additional details of the adhesive have been disclosed in PCT publication WO 95/16424. In this document sanitary napkins having a topical adhesive that is applied on the side facing the user of a sanitary napkin along the entire periphery is disclosed. The problem underlying this document is mainly the secure attachment to the skin but it also mentions the problems of disunion of these items after being used without causing undue pain to a user. The disclosure of the international publication WO 95/16424 includes a detailed analysis of the criteria for the topical adhesive with respect to the rheological criteria. However, this document has little respect for the problem of painless removal of these articles since the rheological criteria taught include depilatory compositions, that is, for the removal of the hair, which are commercially available as STREP MIELE ™ sold in Italy by Laboratori Vaj SpA The adhesives for topical fixation mentioned in WO 95/16424 also include the current pressure sensitive adhesives which are used to attach sanitary napkins to undergarments. further, this document only identifies the static rheological characteristics but is reserved as regards the dynamic rheological behavior of a topical adhesive. In WO 96/13238 a frequency model of the topical dependent adhesive is disclosed. However, all measurements reported, for example, on page 9 were made at temperatures between less than 60 ° C and 120 ° C and the actual frequency is 0.1 to 100 rad / s. In order to obtain the necessary data at the application temperature (at approximately 20 ° C, typical bath, ie storage temperature) the Williams-Landel-Ferry equation (hereinafter WLF) was used. This WLF equation is empirical and only valid within certain limits, for example, it can not be used to extrapolate temperatures below the glass transition temperature of a polymeric adhesive, also the WLF can not be used on the basis of values obtained below the glass transition temperature. Details about the WLF equation and its applicability in "Principles of Polymer Processing" can be found by Z. Tadmor and C.G.

Gogos, published by John Wiley & Sons or in "Viscoelastic Properties of Polymers", by J.D. Ferry also published by John Wiley & They are. Since this is missing from WO 96/13238 the applicability of the disclosed data can not be achieved. European patent application EP-638 303 discloses the use of a topical adhesive on the side folds of sanitary napkins, in order to keep the folds in an upright position. The Swiss publication discloses the use of a very long sanitary napkin having beveled outer edges with a topical adhesive on the four corners of the extreme edges in order to provide an area of external topical adhesive of the pubic hair growth region. Both requests are reserved as regards the adhesive composition. Based on the prior art, it is an object of the present invention to provide a combination of a substrate with a topical adhesive for secure attachment and painless removal of the skin of a disposable absorbent article. It is another object of the present invention to ensure that when removing, no residual adhesive will remain on the skin or on the hair. It is still a further object of the present invention that the combination adhesive for topical fixation does not cause a cold or otherwise unacceptable temperature sensation upon application occurrence despite a temperature difference of the adhesive with respect to the temperature of the adhesive. the skin. In addition to the above objects of the present invention, it is also desirable that the topical adhesives of the combination provide adhesives additional benefits such as supplies / dispersion of a compound or composition that is beneficial to the skin or to the general body. In addition, topical adhesives that do not affect the natural condition of the skin, for example, which are respirable or water vapor transmitters or water vapor / sweat absorbers, are preferred.

BRIEF DESCRIPTION OF THE INVENTION The present invention will be explained in its use in disposable absorbent articles for topical adhesive attachment to a user of these articles. The article typically has a surface that faces towards the body or the user and an external surface. The article comprises an absorbent core structure between the surface facing the user and the external surface to absorb the fluids emanating from a user, such as urine, feces, menstruation, sweat and vaginal discharge. The article further comprises a combination of a substrate with a topical adhesive applied thereon, the combination having a stiffness or flexibility S measured in grams (g) according to the method of the Flexibility Test described hereinafter. The topical adhesive of the combination allows to fix an article to the user's skin, which is typically applied on at least part of the surface facing the user of the article. The detailed analysis of the sequence of common situations that occur from the application of these disposable absorbent articles until the moment of removal of this article, has shown the specific characteristics of the adhesive needed to be preferably met in order to achieve the objectives desired performance, in particular, the initial secure fixation, the secure fixation during use and the final removal without pain. The characteristics that have been considered in this context are the elastic modulus that describes the elastic behavior of the material, and the viscous modulus that describes the viscous behavior of the adhesive material. The viscous behavior of the adhesive can be interpreted to represent an indication of the adhesive's ability to quickly bond and adhere safely. The elastic behavior can be interpreted as a sign or signal of the "firmness" behavior of the adhesive. Its value is also critical for good initial fixation It is believed that their combination is an indicator of the force required when the removal occurs. The relationship between the elastic modulus and the viscous modulus is considered to be an indication over which the fraction of the removal energy within the adhesive will be dissipated and over which the fraction is available to cause actual removal. In order to provide the combination of the present invention of a substrate with a topical adhesive for initial and prolonged secure fixation and easy / painless removal, the relationship between the elastic modulus and the viscous module as well as its dynamic behavior is of key importance. The topical adhesive has an elastic modulus at a temperature of 37 ° C (100 ° Fahrenheit), G'37 abbreviated a viscous modulus at a temperature of 37 ° C (100 ° Fahrenheit) of G "37 and a viscous modulus at a temperature 25 ° C (77 'Fahrenheit) The adhesive also has an elastic dynamic behavior defined as? G'37 which is the difference of G'37 at a frequency of 100 fad7sec and G'37 at a frequency of 1 rad / sec and a viscous dynamic behavior? g "37 that the difference of G'37 at a frequency of 100 rad / sec and 6" 37 at a frequency of 1 rad / sec.The topical adhesive according to the present invention satisfies the following conditions. • G'37 (1 rad / sec) is on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa. • G "37 (1 rad / sec) is in the scale of 100 Pa to 15000 Pa preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa. • the proportion of G'37 (1 rad7seg) / G "37 (1 rad7sec) is on the scale from 3 to 30. • the ratio G \ 7 (100 rad / seq) -G ", 7 (100 rad / seq) G'37 (1 rad / sec) - G" 37 (1 rad / sec) is not less than 0.5, preferably on a scale of 0.7 to 3, most preferably on a scale of 1 to 1.8 • any of the ratio of? G'37 / G37 (1 rad / sec) is not greater than 1.5 , preferably not greater than unity and most preferably not greater than 0.8, or "G'37 is not greater than 10000 Pa, preferably less than 5000 Pa, more preferably less than 2000 Pa, or both. • the value of the ratio G'37 / G "37 at least for the frequency scale of about 1 rad / sec to 100 rad / sec, should preferably be 3.3 or higher, more preferably 5 higher, more preferably 10 or higher , as long as it does not exceed about 30, preferably 20, anywhere in the frequency range • the rheological behavior may also be related to the vitreous transition temperature values Tg. For the topical adhesives according to the present invention , it should preferably be less than 15 ° C, more preferably less than 20 ° C, and most preferably less than -25 ° C. • The behavior and rheological acceptance of a topical adhesive may also be related to the specific heat capacity. Preferably, the specific heat capacity of the topical adhesive is less than 4 J / gK, more preferably less than 3 J / gK and most preferably less than 2 J / gK. The rheological acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive. Preferably, the specific heat conductivity is as low as possible, preferably between 1 and 0.1 W / m / K, more preferably between 0.6 and 0.1 W / m / K. Provided that the above rheological conditions are satisfied, the adhesives will also satisfy conditions such as sufficient adhesion (to avoid adhesive residue on the skin), which are critical to the commercial use of these adhesives and apparent to those skilled in the art. Adhesive compositions that meet the above criteria can be used as topical adhesives for disposable absorbent articles as long as they also meet the common requirements of being safe to use on human skin or animals during use and generally after disposal. Article. Often the criteria of hygienic appearance and comfortable feeling when in contact are important, such that adhesive compositions that will be transparent or white are preferred, and which avoid an uncomfortable, cold feeling when applied.

The above rheological criteria and other considerations can be satisfied by the adhesive compositions, wherein the composition comprises 45%, preferably 51% to 99.5% of a plasticizing compound or composition, which is liquid at 20 ° C, of 0.5 to 20%, preferably from 5% to 15% of a polymeric compound or composition that is soluble or capable of swelling in the plasticizer composition or composition and with a tackifying resin in an amount in the range of 0% to 50% by weight of the composition, preferably from 0% to 600% by weight of the polymeric compound. The plasticizing compound or composition is preferably selected from the group consisting of water, alcohols (preferably glycerol), glycols, polyglycols, liquid polybutenes, oil or combinations thereof. The polymeric compound or composition is preferably selected from the group consisting of block copolymer thermoplastic elastomers, styrene block copolymers and hydrogenated styrene block copolymers, polyacrylics, polyvinyl alcohol, natural gum or gelatins, polyethylene oxide, polyvinylpyrrolidone (PVP ), polyvinyl ethers, cellulose derivatives, or combinations thereof.

In accordance with the present invention, it has been found that the relationship between the stiffness or flexibility S of the combination of the substrate with the topical adhesive applied thereon, on at least part of the body-facing surface of the disposable absorbent articles. , and the viscous modulus G "25 about 100 rad / sec of the topical adhesive is relevant to the scope of providing an easy and painless removal of the skin of the user of such substrate combination with topical adhesive used for fixing an absorbent article. disposable to the user's skin.

The combination according to the present invention of the substrate with the topical adhesive applied thereon, is such that the viscous modulus G "25 (100 rad / sec), the topical adhesive and the stiffness or flexibility S of the combination satisfy the equation empirical following: G "25 < [(163.8 + S) - 50.9] Pa and preferably the following empirical equation: G "25 < [(82.2 + S) - 51.4] Pa DETAILED DESCRIPTION OF THE INVENTION Adhesive for Topical Fixation The topical adhesive of the combination of the present invention is applied directly to the skin. In a particular application, the adhesive can be used in sanitary napkins which are applied to the genital region of a typically female user around the discharge area of the liquid. The word "skin" according to the present invention is not only related to the specific dermis of the user but includes the mucosal tissue also as the hair that is typically found in the genital region of the users of the sanitary napkins. In order to provide fixation of an article to the skin, it is necessary to provide a certain area on the side of the article that is facing the skin with the topical adhesive. Typically the topical adhesive of the combination of the present invention is provided on at least part of the user-facing surface of the disposable absorbent article being applied to a substrate whose combination has a stiffness S measured in grams (g) of according to the flexibility test described hereinafter. The combination may be joined or fixed with any known means for the disposable absorbent article as an additional layer, constituting at least part of the body surface of the article, or, preferably the combination may comprise all or part of the absorbent article itself. For example, the substrate may be the top sheet of the absorbent article, or, alternatively, the substrate may be the total absorbent article. While referring the evaluation to the rigidity S of the combination as will be explained in more detail hereinafter, it can be assumed that in most cases the rigidity of the combination actually corresponds to the stiffness of the total absorbent article, including the topical adhesive, in the preferred embodiment when the substrate actually corresponds to the total absorbent article. Therefore, it can be said that preferably the substrate actually comprises the total absorbent article, typically constituted by at least one liquid-permeable top sheet, a liquid-impermeable back sheet bonded to the top sheet, and an absorbent core placed between the sheet upper and the back sheet. For the various designs of sanitary napkins it is contemplated, but preferably the topical adhesive is provided adjacent to the peripheral edge of the topsheet such that a central area of the article is left without adhesive. This will more appropriately facilitate the placement of the towel in such a way that the region of the liquid-permeable upper sheet without adhesive is placed adjacent to the orifice where the body fluid emanates, such that the liquid emanating is transported immediately towards the absorbent structure of the absorbent article without the possibility of leakage or spillage. The topical adhesive is provided with the preferred pattern on the substrate on the surface facing the user of the article in a layer which may preferably be continuous or alternately discontinuous, for example, in the form of dots, spirals or strips, and having a thickness or gauge that is preferably constant.

Physical, Rheological and Adhesive Characteristics of a Topical Adhesive Even when topical adhesives similar to pressure sensitive adhesives are used in human skin hair and mucosal tissues, it is understood that topical adhesive compositions can only with difficulty be considered typical pressure sensitive adhesives (referred to as PSA hereafter) on the basis of the rheological behaviors, more characteristic that identify these materials. In fact, as the person skilled in the art of adhesives knows, the most characteristic aspect that distinguishes a PSA from other substances that can temporarily stick things (as can, for example, water between two glass plates), is the fact that its rheological parameters and especially the elastic modulus G 'vary greatly with the frequency of the applied stresses. More particularly, the G 'of the PSA may increase over some types of magnitude while the frequency of the applied voltages varies from the typical joining frequency to the typical disconnection frequency, i.e. from 1 rad / sec to 100 rad / sec as is indicated below. As a first consequence, it is inadmissible to define materials destined to be used as "topical adhesives", giving values of the rheological parameters and especially of G 'at a fixed frequency value. This can be misleading because in the absence of other features it will include materials that do not have practical values. It is consequently necessary that the rheological characterization should be based on dynamic considerations. This not only applies to the elastic modulus G 'but also to the viscous modulus G "and consequently also to (d) = G'VG' It is well known that the typical PSA does not have only a high variation of G 'through the frequencies considered, but there is also a variation of G "even higher that may be close to or even higher than the value of G ', ie (d) becomes approximately or even higher than 1, particularly in the frequencies that are typical of disunity. Without wishing to be bound by theory, this can be interpreted as meaning that a high fraction of the energy applied for disunion dissipates within the adhesive (so that it is not effective at causing disunion), while this fact causes macroscopically the registration of a very high level of adhesive force. As indicated above, the materials useful as topical adhesives according to the present invention, have rheological characteristics that are measured at a reference temperature of 37 ° C (as the normal body temperature of humans), and within a scale of frequencies. It has been found that upon application of an article such as a sanitary napkin, such as a topical adhesive, adhesive contact is formed at a low frequency, while disbonding occurs at the rate of removal of the article. This speed is expressed as a frequency of 100 rad / sec whereas it has been found that the low frequency of forming the adhesive bond is in the order of 1 rad / sec. Therefore, the range of frequencies to be used in agreement is between 1 and 100 rad / sec. It is believed that the characteristics of the adhesive bond are selected most appropriately at the temperature of the human body. Since the topical adhesive according to the present invention is used directly on the skin and the person skilled in the art is directed to select the composition of the adhesive to have a small specific heat capacity (eg, preferably less than 4 J / g / K), the actual temperature of the topical adhesive will reach 37 ° C very quickly or will still be heated by a human before application. In order to provide good bonding conditions, that is, at a frequency of about 1 rad / sec, the absolute values of the elastic modulus should not be too high, otherwise the adhesive is too hard and is not able to intimately bond or mold to the surface to which it is expected to adhere. It is also important to have an absolute value of G "low in order to have a good cohesion that is particularly valuable to be used in the field of sanitary napkins, and to generate when articles are used that are frequently removed and adhered again or replaced, While the material remains soft, and is able to adhere gently to the skin, the ratio of G'37 (1 rad / sec) to G "37 (1 rad / sec) is important to ensure that these two values are balanced when occurring adhesion to the skin. At the same time, the absolute changes of G'37 need to be limited within the range of frequencies considered. Consequently, a low value must be maintained for the ratio of? G'37 (ie, G'37 (100 rad / sec) -G'37 (1 rad / sec)), above G'37 ( 1 rad7sec) in order to maintain the secure fixation of the topical adhesive without causing discomfort during the time or in the removal / lamination. This can also be expressed in absolute terms by keeping the? G'37 below certain values.

Importantly, the ratio of G (100 rad / eg) - G "(100 rad / sec) G'37 (1 rad / sec) - G" 37 (1 rad / sec) needs to be sufficiently large to ensure that the dynamic behavior of both the elastic modulus and the viscous modulus are maintained in a relationship that provides safe adhesion and painless and easy removal. Finally, the person skilled in the art will also recognize that the vitreous transition temperature Tg of the adhesive composition, the specific heat capacity, and the specific heat conductivity are parameters that are useful to more fully define the group of topical adhesives tools. The following set of characteristics must be satisfied: • G'37 (1 rad / sec) is on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa. • G "37 ( 1 rad / sec) is on the scale from 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa. "The ratio of G'37 (1 rad7sec) / G" 37 (1 rad7sec) is on the scale from 3 to 30. • the proportion G '^ (100 rad / secVG' '. (100 rad / sec) G'37 (1 rad / sec) - G "37 (1 rad / sec) is not less of 0.5, preferably on the scale of 0.7 to 3, most preferably on the scale of 1 to 1.8 • any of the proportion of? G'37? 337 (1 rad / sec) is not greater than 1.5, preferably not greater than unit and most preferably not greater than 0.8, or "G'37 is not greater than 10000 Pa, preferably less than 5000 Pa, more preferably less than 2000 Pa, or both • the value of the G'37 / G ratio" 37 at least for the frequency scale of aproxima preferably 1 rad / sec to 100 rad / sec, should preferably be 3.3 or higher, more preferably 5 higher, more preferably 10 or higher, while not exceeding about 30, preferably 20, anywhere in the frequency range. • the rheological behavior can also be related to the values of the vitreous transition temperature Tg. For topical adhesives according to the present invention, it should preferably be less than -15 ° C, more preferably less than 20 ° C, and most preferably less than -25 ° C. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat capacity. Preferably, the specific heat capacity of the topical adhesive is less than 4 J / gK, more preferably less than 3 J / gK and most preferably less than 2 J / gK. • The behavior and rheological acceptance of a topical adhesive can also be related to the specific heat conductivity of the adhesive. Preferably, the conductivity of the specific heat is as low as possible, preferably between 1 and 0.1 W / m / K, more preferably between 0.6 and 0.1 W / m / K.

Chemical Characteristics and Composition of a Topical Adhesive In order to provide topical adhesive compositions that meet the requirements of the rheological and physical characteristics of a topical adhesive above, the following formulation criteria should be used. It should be noted that most of the compositions useful as the topical adhesive have a substantially gel-like structure and are preferably gels. This derives from the fact that: the predominant component is the plasticizer, which is a liquid material at room temperature. A macromolecular or polymer component is present in minor amounts against the plasticizer. This form, in the preferred modalities, a three-dimensional network made by the physical and chemical bonds between the molecules. Particularly useful physical links are the bonds present in systems containing block thermoplastic elastomers.

More specifically, the compositions typically comprise: from 0.5 to 20%, preferably from 5% to 15%, by weight of a macromolecular polymer substance or a mixture of these substances soluble or capable of swelling in the aforementioned plasticizer (s). As non-limiting examples, these polymeric or macromolecular substances can be natural and / or synthetic, such as natural gums or derivatives such as natural gums and gelatins, their derivatives and alginates; polyacrylics; polyvinyl alcohol; polyethylene oxide; polyvinylpyrrolidone (PVP) or polyvinyl ethers, their copolymers and derivatives; cellulose derivatives; Thermoplastic Elastomers of Block Copolymer and preferably Styrenic Block Copolymers and more preferably the hydrogenated grades Styrene / Ethylene-Butylene / Styrene (SEBS), / Styrene / lsoprene / Styrene (SIS), and Styrene / Ethylene-Propylene / Styrene (SEPS). from 45 to 99.5% by weight, preferably from 51 to 99.5% by weight of a piastifying substance or a mixture of plasticizing substances, which are liquid at room temperature. As non-limiting examples, the plasticizer may be water, various alcohols (such as in particular glycerol), glycols, polyglycols, liquid polybutenes, natural or synthetic oils such as vegetable oils, mineral oils, or combinations thereof. from 0% to 50% by weight of the composition, preferably from 0 to 600% by weight of a macromolecular polymer substance of a tackifier resin whose main scope is to form the Tg especially in systems based on synthetic polymers. from 0 to 10% and more preferably from 0 to 5% by weight of a substance to facilitate and stabilize the gelation of both the hydrophobic and hydrophilic liquid plasticizers. These can be for oil systems, for example, C8 to C22 fatty acids, their metal salts and their polyoxyl derivatives; lanolin derivatives, silica; bentonite, montmorillonite and its derivatives; polyamides, waxes or mixtures thereof. Common additives known in the art as preservatives, antioxidants, anti-ultraviolet agents, pigments, mineral fillers, rheology modifiers, etc., may also be comprised in amounts of up to 10% each. When chemical lattices are formed in the system, a crosslinking agent may be present in amounts of up to 5% by weight. Chemical crosslinking can also be formed by the mutual neutralization of polymers having different functionalities as in the reaction between polyacrylic acids and polysaccharides. The compositions for the topical adhesives can be divided into three families according to the nature of their main component, i.e., normally the plasticizer or liquid plasticizers (s): 1) The hydrophobic compositions in which the plasticizer is typically an oil or mixtures of vegetable and mineral oils and the polymer is usually a synthetic polymer, preferably an elastomer, soluble, or capable of swelling the oil or oils. 2) Mixed phase compositions in which both hydrophobic and hydrophilic components, possibly both plasticizers and polymers, form two or more separate phases. In these cases, an emulsifier / surfactant is preferably present at an adequate level to form stable emulsions between incompatible phases. For topical adhesives according to the present invention, it is preferable that the hydrophobic components are predominant against the hydrophilic components. 3) The hydrophilic compositions in which typically the plasticizer is water / glycerol / glycols and the like and / or mixtures thereof and the polymer phase is of synthetic (for example polyacrylics), or natural (for example natural gums) or mixtures thereof. It is important that, unlike the medical field and prior art cited, hydrophilic compositions are not preferred, although hydrophobic and mixed phase compositions 1) and 2) are preferred in the applications of the present invention. This partly depends on technical reasons in the sense that many of the hydrophilic compositions used in the medical field show elasticity and cohesion too low to be useful in the present application. The other reason for preferring the hydrophobic or easily mixed compositions is that the application of the present invention, particularly in the field of sanitary napkins, will include a likelihood of contacting the topical adhesive with the liquid being absorbed. Since the liquids are, all of a general aqueous type, in contact with a topical hydrophilic adhesive, would result in a certain absorption of body fluids in topical adhesives This would then have the result of changing the rheological characteristics and therefore the functionality of the topical adhesive and causing an unhygienic appearance. In addition, the hydrophilic topical adhesive also tends to be perceived as cold and wet which upon application to a human skin is not in line with the typical expectation. Additional problems result from the fact that particular topical adhesives comprising water as the plasticizer have a tendency to dry unless sealed in a waterproof package.

Application of the Topical Adhesive Absorbent articles in which the combination according to the present invention can be used, comprising the topical adhesive, can be made by any of the usual manners in the art. The application of the adhesive to a substrate to form the combination of the present invention should not cause greater problems to those skilled in the art, since it can be provided by any of the well-known techniques commonly used for other adhesives. As already mentioned, the combination of the substrate with the topical adhesive can be applied to the absorbent article as an additional layer. Alternatively, and preferably, the substrate may be partially or totally the absorbent article itself.

For example, the substrate of the combination may be the top sheet of the absorbent article. Preferably, the substrate of the combination of the present invention is the total disposable absorbent article. The substrate can comprise any suitable material, provided that the conditions set forth below are met. In the embodiment where the substrate is actually the top sheet of the absorbent article, any material commonly used as a top sheet is suitable as the substrate for the composition of the topical adhesive in order to form the combination according to the present invention, in most of the cases, the substrate of the combination according to the present invention is the entire absorbent article, for example, comprising at least one topsheet, a backsheet and an absorbent core therebetween. First of all, the total area of the skin or the surface facing the user of an article comprising the combination of the present invention, which is covered by the topical adhesive, should not be greater than 20%, preferably not greater than 10%. %. Preferably, the adhesive is close to the periphery of the absorbent article and when the substrate of the combination is constituted by, or comprises an upper sheet of film, the adhesive may preferably be on a part of the film that is not liquid permeable. The topical adhesive is applied on the substrate to form the combination on at least part of the user-facing surface of the disposable absorbent article in a layer having a thickness or caliper that is preferably constant, or which alternatively can vary over the surface of interest by the application of the topical adhesive. If possible, the article also provides breathability by being at least permeable to water vapor, preferably permeable to air to prevent it from being poorly ventilated. The breathability, if not supported or maintained by the topical adhesive as such, may be limited to the area of the article where no adhesive is applied. The topical adhesive in an article is preferably protected before use. This protection can be provided by a release liner such as a paper treated with silicone or surfactant, providing easy detachment of the selected topical adhesive. This invention can be beneficially used in disposable absorbent articles that are applied directly to a user's skin. The article normally exhibits absorbency of bodily fluids, the protection of the user's garments against staining is convenient to use, and is easy to produce and pack. The disposable absorbent article is described below with reference to a sanitary napkin or catamenial product, however, pantiprotectors, adult incontinence articles or sweat pads are also included under the term "disposable absorbent articles". The term "sanitary napkin" as used herein, refers to an article that is worn by women adjacent to the pudendal region and which is intended to absorb and contain the various body fluids that are discharged from the body (e.g., vaginal discharges, menses and / or urine), and which are intended to be discarded after a single use. A disposable absorbent article is preferably thin, more preferably between 1 and 5mm thick and, either, substantially planar before use or in a preconfigured form. The terms "attached" or "fixed", as used herein, encompass configurations by which a first member is directly connected to a second member and configurations by which a first member is indirectly connected to a second member by connecting the first member to intermediate members who in turn are connected to the second member. In a preferred embodiment, a sanitary napkin of the present invention comprises a liquid permeable upper sheet, a liquid impermeable back sheet attached to the upper sheet, and an intermediate absorbent core to the upper sheet and the back sheet. The sanitary napkin has two main surfaces, a surface that is in contact with the body or that faces the user on which the topical adhesive is applied and a surface that faces the garment or that is in contact with the garment. The upper sheet is docile, soft feeling, and non-irritating to the user's skin, the upper sheet may also have elastic characteristics that allow it to be stretched in one or two directions, in parts of the upper sheet, or in all its extension. In addition, the topsheet is permeable to fluid, allowing fluids (eg, menses and / or urine) to easily penetrate through its thickness. The preferred top sheets for use in the present invention are typically selected from the upper nonwoven sheets with raised upper region and upper sheets of film formed with openings. Films formed with openings are especially preferred for the upper sheets because they are permeable to body exudates and not yet absorbent, and have a reduced tendency to allow the fluids to pass back through and rewet the user's skin . In this way, the surface of the formed film that is in contact with the user remains dry, thus reducing the staining of the body and creating a more comfortable feeling for the wearer. Suitable formed films are described in U.S. Patent No. 3,929,135, U.S. Patent No. 4,324,246; U.S. Patent No. 4,342,314; U.S. Patent No. 4,463,045; and United States Patent No. 5,006,394. Top sheets of film formed with particularly preferred micro apertures are disclosed in U.S. Patent No. 4,609,518 and U.S. Patent No. 4,629,643. A preferred top sheet for the present invention comprises the formed film described in one or more of the above patents and sanitary napkins are marketed by The Procter & Gamble Company of Cincinnati, Ohio as "DRI-WEAVE". In order to form a preferred combination of a substrate with the topical adhesive, the topical adhesives are most suitably used on top sheets which do not have a homogenous liquid passages distribution but only a part of the top sheet comprising the liquid passages oriented in such a way as to result in an upper sheet that is centrally permeable and peripherally permeable to liquids. Another alternative is the so-called hybrid top sheets, which incorporate structures in fibrous and film form, particularly useful embodiments of these hybrid top sheets are disclosed in PCT Publication Nos. WO 93/09744; WO 93/11725 or WO 93/11726. When we refer to the top sheet, a multi-layered structure or a single layer structure is contemplated. The hybrid top sheet mentioned above, is this multi-layered design, but other multi-layered top sheets such as the primary and secondary top sheet designs are also considered. The absorbent core can also comprise multiple layers and provides the function of fluid storage and distribution. Placed in fluid communication with, and typically underlying, the top sheet, is the absorbent core. The core may comprise any normal absorbent material or combinations thereof. This preferably comprises gelling absorbent materials, generally referred to as "hydrogel", "superabsorbent", "hydrocolloid" materials in combination with suitable carriers. The gelling absorbent materials suitable for use herein will often comprise a partially neutralized, lightly crosslinked polymeric gelling material, substantially insoluble in water. This material forms a hydrogel upon contact with water. These polymer materials can be prepared from acid-containing, unsaturated, polymerizable monomers, such as acrylic acid, which are well known in the art. Suitable carriers include materials that are conventionally used in absorbent structures such as natural, modified or synthetic fibers, particularly modified or unmodified cellulose fibers in the form of fluff and / or tissue. Suitable carriers can be used together with the gelling absorbent material, however, they can also be used alone or in combinations. Tissue and tissue laminates are very preferred, in the context of sanitary napkins / linings. One embodiment of the core, particularly useful in the application of the present invention, comprises a laminate of double-layer tissue formed by folding the tissue over itself. These layers can be joined together. The gelling absorbent material or other optional material can be comprised between the layers. The absorbent core may include optional components normally present in the absorbent webs such as odor control agents, in particular suitable zeolites. The backsheet primarily prevents the exudates absorbed and contained within the absorbent core from wetting articles that come into contact with the absorbent product such as underpants, briefs, pajamas, and undergarments. The backsheet is preferably impervious to liquids (eg, menses and / or urine and is normally manufactured from a thin plastic film.) The backsheet typically extends throughout the entire absorbent core and can extend over and form a part. of the top sheet, bending around the absorbent core.Thus a preferred configuration of the top sheet as disclosed in U.S. Patent No. 4,342,314, column 16, lines 47 to 62, can be achieved without the requirement of selectively drilling the top sheet. Preferably, the backsheet also provides breathability to the absorbent article by being at least permeable to water vapor, preferably permeable to air. The backsheet may be a laminate, for example, of a combination of microporous film, and / or a non-woven material, and / or film formed with openings. The breathability, if desired, may be limited to the periphery or the center of the backsheet, or this may be throughout the entire back sheet. When the removal phase of a combination of a substrate with a topical adhesive composition for attachment to the skin of a wearer of a disposable absorbent article is particularly considered, it is commonly recognized that good conditions of removal, ie at a frequency of about 100 rad / sec, of the topical adhesive applied to at least part of the surface facing the wearer of a disposable absorbent article for securing said article to the user's skin, are achieved when the adhesive can be easily removed from the skin, and particularly the hairs that typically grow on it, where the disposable absorbent article is in contact with the body, without causing pain to the user, therefore without sticking too strong when removing from the skin and the hairs of the user. Moreover, a good removal means that the topical adhesive does not leave residues that remain on the skin or on the hairs. According to the present invention, the relationship between the stiffness or flexibility S of the combination of the substrate with the topical adhesive applied thereon, as measured in grams according to the Stiffness Test described below, and the viscous modulus G " 25 to 25 ° C and approximately 100 rad / sec of the topical adhesive gives a signal about the painless and easy removal of topical adhesive from the user's skin.It has been found that for values higher than G "25 to 100 rad / sec, which generally corresponds to a superior adhesiveness of the composition, a higher stiffness S of the combination of substrate with the topical adhesive is needed, in order to reduce the sensation of pain to the user when the absorbent article comprising the skin is removed from the skin. combination. In other words, combinations of less rigid substrates and topical adhesives require an adhesive with a G "25 at 100 rad / sec lower to achieve a reduced painful sensation upon removal of the absorbent article comprising the combination. invention, the combination of the substrate with the topical adhesive applied thereon, said combination having a stiffness S, is such that the viscous modulus G "25 (100 rad / sec) and the stiffness or flexibility S satisfy the following empirical equation: G "25 < [(163.8 + S) - 50.9] Pa and preferably the following empirical equation: G "25 < [(82.2 + S) • 51.4] Pa The stiffness or flexibility S of the substrate combination with the topical adhesive is measured in grams (g) according to the Stiffness Test. This depends on the nature of the substrate and the adhesive. According to the present invention, the substrate comprises all the layers that are joined together to unify them at least in the region corresponding to the region occupied by the topical adhesive. The rigidity of the substrate combination plus the topical adhesive depends strongly on which materials and how many layers actually correspond to the substrate. As already mentioned, the substrate combination with the topical adhesive may be attached or attached to the disposable absorbent article, or alternatively, the substrate may partially or fully comprise the absorbent article.

The substrate of the combination can be attached or attached to the absorbent article by any known means, for example, by bonding with adhesive, thermal bonding, mechanical bonding, or any combination thereof, but outside the region corresponding to the region where the topical adhesive is applied. In such embodiment of the present invention, the substrate of the combination may comprise one or more separate layers joined together or attached to the absorbent article, for example, along its respective contour edge, the remaining portions of the substrate not being bonded to the substrate. absorbent article. In this case, the rigidity of the combination that is relevant in the removal of the absorbent article is that of the layer or layers that constitute the substrate. If the substrate partially comprises the absorbent article, for example, typically corresponding to the top sheet, it can only be attached or fixed to the remaining part of the absorbent article substantially outside the region corresponding to the region occupied by the topical adhesive. Outside this region, the substrate is joined by any known means. In most cases, the flexibility or rigidity of the substrate combination with the topical adhesive generally corresponds to the flexibility or stiffness of the total absorbent article including the topical adhesive, when the total particle layers are bonded together to unify them at least in the region that corresponds to the region occupied by the topical adhesive. In order to evaluate the effect of the stiffness S of the combination of the substrate with the topical adhesive in its relation to the viscous modulus G "25 (100 rad / sec) of the topical adhesive of the present invention in the removal of the topical adhesive used for the fixation of a disposable absorbent article to the skin of a user, a Removal Pain Degree Test has been developed, where the adhesion of the combinations having different stiffness due to the different substrates covered with a layer of the same adhesive was achieved. Topical, on the forearm skin of the members of a sensitive panel, and upon successive removal, the pain was evaluated in terms of the degree of pain.The rigidity of the combinations is in turn evaluated according to the Rigidity Test described later.

METHODS OF TEST Testing the degree of pain during removal The test of the degree of pain during removal is used to assess pain during the removal of a user's skin from a sample provided with a topical adhesive layer and which was previously fixed to the wearer's skin. The test specifically evaluates the pain by removing each sample as compared to the pain obtained by removing a reference sample constituted by a firm, commercial medical poultice.

Preparation of the sample The test is performed on 60 by 20 mm rectangular samples of the selected substrate provided on one side with a continuous layer of the topical adhesive having a selected thickness applied with an Acumeter Model LH-1 extruder. Samples represent combinations of different substrates with the topical adhesive. The reference sample is a 60 x 20 mm sample of a double-sided medical adhesive tape produced by Minnesota Mining and Manufacturing Company under the trade name Medical Tape No. 1524; only one of the two layers of the adhesive is exposed in the reference sample and is used to fix it to the skin during the test.

Testing method A panel of 6 graders was selected for the test. The test is carried out in a climatically controlled laboratory where a temperature of 23 ° C, and a relative humidity of 50 is maintained. No special treatment of the user's skin is required beyond the normal cleaning / washing with soap and water and dry for at least 2 hours before the test to allow equilibrium to be achieved with the skin's environmental conditions. Three different samples A, B and C are evaluated in the test compared to the reference sample R. Each sample is applied by hand by an operator on the inner part of the forearm of the grader, being centered between the elbow and the wrist, with the short side of the sample aligned with the length of the arm. The operator exerts the same pressure on each sample with his palm, which is typically applied so that he adheres the medical plaster to the skin. Each sample is used for the prescribed time, and then removed from the grader skin by the operator with a slow and slow shot. Four series of a reference sample R and the three samples A, B and C each, used and then removed from the user's skin are applied; each sample is used between two subsequent samples of the same series and a wait of 15 minutes between two later series. The reference sample R is always applied, used and withdrawn as the first sample of its respective series. The sequence of application / use / removal of samples A, B, C in each of the first 3 series is random, provided that repetition is not allowed in each series, and the sequence is not repeated in the first three series . In the four series of the four samples one of the samples of A, B, or C, the reference R is always tested twice, always being the first. In general, each sample (A, B, C and R), has to be tested an equal number of times (24 times according to the scheme below). In the tests carried out, the sequences of the four series are in accordance with the following scheme: The graders were asked to evaluate each sample A, B and C using a pain scale ranging from 0 to 10, where 0 corresponds to no pain and 10 corresponds to pain when removing the reference sample R. Pain values for each sample A, B and C were obtained as an average of 24 observations. The results collected from the test were analyzed by means of a statistical analysis program "comparison of samples in pairs of the popular average", which showed that the differences between the pain values of samples A, B and C are statistically significant. .

Flexibility test The flexibility test is used to quantify the flexibility or rigidity in the machine direction of the combination comprising the substrate and the topical adhesive applied thereon. The flexibility test used here is a dynamic measurement of stiffness (force to deform vs. deformed distance), which determines the average force (in grams) required to compress a substrate in the machine direction.

Preparation of the sample The test is performed on rectangular samples of 60 x 20 mm of the selected material cut with the longer side oriented in the machine direction, and provided on a surface with a continuous layer of the topical adhesive having a basis weight of 1350 grams per square meter, applied with an extruder acumeter model LH-1. Remove any protective release paper, if present, before the test is carried out.

Apparatus 1) Climate controlled laboratory. Maintained at 23 ° C and 50% relative humidity 2) Dynamometer model 6021, Instron Limited, GB. Interconnected to a standard IBM computer with RS-232 interface for data logging. The data is sent to the computer in the form of distance and force values, and is read in a standard Microsoft Excel spreadsheet for analysis. He Instron is established for a series of compression tests. Load Cell = 10 N Initial fastener spacing = at 50 mm Final fastener clearance = at 15 mm Deforming sample distance = 35 mm Compression speed = 100 mm / minute 3) Scissors Measurement of Flexibility The sample is placed vertically and symmetrically between the fixed and mobile fastener, with each fastener retaining a 5 mm wide part of the sample along its respective short edge, with the exposed adhesive surface facing towards the operator. Contact between the fasteners and the topical adhesive in the sample is prevented by applying a small rectangular piece of release paper of approximately 20 x 5 mm onto the top portion of the sample, tried to be held by the respective fastener, over the topical adhesive. The sample is slightly inclined so as to bend during compression with convexity on the adhesive surface. The fasteners are placed in such a way that compression begins (in the direction of the product machine), from a distance of 50 mm.

The sample is compressed in a distance of 35 mm to a final separation of the fastener of 15 mm. The details of the instrument are given above. The Instron records the separation of the fastener (in mm), and the force exerted to achieve this separation and sends this data through an RS 232 interface to an IBM computer equipped with the Microsoft Excel spreadsheet. The force and distance data is loaded into the Excel Software and the measurements of the average force over the total compression cycle of 35 mm are determined. Measurements are made and averaged over 5 samples of the same type to ensure that a value of the representative stiffness is determined for each sample under investigation.

The pain at the time of removal was assessed according to the test of the degree of pain during removal for three different combinations represented by samples A, B and C that have different values of stiffness determined with the flexibility test, each combination having one layer of the same topical adhesive applied on it. A topical adhesive is an oil-based composition containing 10% by weight of Krato G-1651, a styrene / ethylene / butylene / styrene / styrene block copolymer available from Shell Co., 49% by weight of Kaydol, a paraffinic mineral oil available from Witco Co., 40% by weight of Escorez 5300, a hydrogenated tackifier resin available from Exxon Co., 0.7% by weight of magnesium stearate, a co-gelling agent available from Cerlo Erba, SpA, and 0.3% by weight of Irganox 1010, an antioxidant available from Ciba Geigy. Finally, the formulation had the following percentage composition: Kraton G-1651 10.0% by weight Kaydol 49.0% by weight Escorez 5300 40.0% by weight Magnesium stearate 0.7% by weight Irganox 1010 0.3% by weight The composition shown has the following properties Rheological at 37 ° C. a) Elastic modulus at 1 rad / sec G'37 = 7038 Pa b) Viscous module at 1 rad / sec G "37 = 487 Pa c) Proportion of Elastic and Viscous Modules at 1 rad / sec, G'37 / G "37 = 14.45 d) Proportion of G ', 7 (100 rad / sec) - G% 7 (100 rad / sec) G'37 (1 rad / sec) - G "37 (1 rad / eg) = 1.11 e) The proportion of G'37 on G'37 (1 rad / sec) was 0.291, with? G'37 = 20501 Pa. The composition also has a viscous modulus G "25 at 25 ° C and at approximately 100 rad / sec at 4431 Pa. The three substrates of combinations A, B and C are as follows: The substrate of combination A is a nonwoven material sold by Suominen under the trade name Fibrella, code F2200 / 50, with a basis weight of 50 g / m2 . The substrate of the combination B is a 23 μm thick polyester film, such as that sold by Effegidi S.p. A., from Colorno (Parma, Italy). The substrate of the combination C is prepared by applying to a polyester film of the same type already described for the substrate of the combination B, a double-sided medical tape produced by Minnesota Mining and Manufacturing Company under the trade name Medical Tape No. 1524. Only one of the two adhesive layers of the medical tape is exposed and used for fixing the double tape to the polyester to form a composite substrate in layers. The release paper of the second adhesive layer of the medical tape is retained in its position. The topical adhesive is applied on the polyester surface of the composite substrate to form the combination C. The rigidity of the three combinations and the respective degrees of pain are shown in the following table: The results show that for a given topical adhesive composition, represented by the value of G "25 (100 rad / sec) of 4431 Pa, the incremental stiffness values for the combinations of the substrates with the topical adhesive layer correspond to Reduced degrees of pain by removing topical adhesive from the skin Of course, the rigidity values for substrate combinations with a topical adhesive for skin fixation of disposable absorbent articles can be varied according to the empirical equations of the present invention to achieve acceptable degrees of pain upon removal with the different topical adhesive compositions, and therefore with different values of G "25 (100 rad / sec), within the limits that can be easily determined by the person expert in the technique. In general, in the field of disposable absorbent articles, this limit should not exceed 300 g. The same is true for the possible selection of preferred topical adhesive compositions having G "25 (100 rad / sec) values that are applied to a substrate having a certain fixed rigidity in order to reduce the degree of pain upon removal. The skin absorbent article The preferred limits for G "25 (100 rad / sec) of a topical adhesive composition are implicitly defined for example, by the preferred rheological characteristics of the topical adhesive compositions. The pain upon removal may be further reduced when in the combination of the present invention the topical adhesive is provided on the substrate in a layer having a thickness C measured in millimeters (mm), such that the viscous modulus G "25 ( 100 rad / sec) and the thickness C of the adhesive layer satisfy the following empirical equation: G "25 < [(4.26 + C) - 1605] Pa and preferably the following empirical equation: G "25 <[(1.53 + C) - 1724] Pa as described in the European patent application entitled" Adhesive for secure topical fixation skin and adequate removal with low level of pain, particularly absorbent articles ", presented together with the present application, inventors Fabio Cinelli, Peter Coles, and Italo Corzani, corresponding to Attorney Document No. CM1770FQ.

Claims (10)

1. A combination of a substrate with a topical adhesive applied on the substrate, said combination intended to fix a disposable absorbent article to the skin, said combination having a stiffness S measured in grams (g) in accordance with the Flexibility Test herein, said adhesive having an elastic modulus at a temperature of 37 ° C (100 ° F), G'37, and having a viscous modulus at a temperature of 37 ° C (100 ° F), G "37, and a viscous modulus at a temperature of 25 ° C (77 ° F), G "25, said combination of said substrate with said topical adhesive is characterized in that said viscous modulus G" 25 (100 rad / sec) of the topical adhesive and said stiffness S of the substrates satisfy the following equation: G "25 < [(163.8 + S) - 50.9] Pa

2. A combination according to claim 1, characterized in that said viscous modulus G "25 (100 rad / sec) of the topical adhesive and said stiffness satisfy the following equation: G" 25 < [(82.2 + C) - 51.4] Pa

3. A combination according to claim 1, characterized in that said adhesive is selected to have: - »G'37 (1 rad / sec) on the scale from 1500 Pa to 20000 Pa, preferably 1500 Pa to 15000 Pa, more preferably 3000 Pa to 10000 Pa; • G "37 (1 rad / sec) is on the scale from 100 Pa to 15000 Pa, preferably 100 Pa to 10000 Pa, more preferably 3000 Pa to 5000 Pa • the proportion of G'37 (1 rad7sec) / G" 37 (1 rad7sec) is on the scale of 3 to 30; • the ratio GX (100 rad / sec) -G "7 (100 rad / sec) G'37 (1 rad / sec) - G" 37 (1 rad / sec) is not less than 0.5, preferably in the scale of 0.7 to 3, most preferably on the scale of 1 to 1.8 alternately, either, G'37 (100 rad / sec) - G'37 (1 rad / sec) is not greater than 10000 Pa, preferably less than 5000 Pa, preferably less than 2000 Pa; or the ratio G'37 (100 rad / sec) - G'37 (1 rad / sec) / G'37 (1 rad / sec) is not greater than 1.5, preferably not greater than 1, most preferably not greater than 0.8 , or a combination thereof. A combination according to any preceding claim, characterized in that the substrate is a disposable absorbent article, said disposable absorbent article comprising a liquid-permeable topsheet, a liquid-impermeable backsheet attached to the topsheet, and an absorbent core. placed between the top sheet and the back sheet. 5. A combination according to any preceding claim, characterized in that said adhesive is provided as a continuous layer. 6. A combination according to any preceding claim, comprising: from 45% to 99.5%, preferably from 51% to 99.5%, by weight a plasticizer compound or composition which is liquid at 20% C; 0.5% to 20% by weight of a compound or polymer composition that is soluble or swellable in the plasticizer composition or composition; a tackifying resin in an amount of 0% to 50% by weight, preferably 0% to 600% by weight of the compound or polymer composition. 7. A combination according to claim 6, wherein said plasticizer compound or composition is selected from the following group: water, alcohols, glycols, oil or combinations thereof; and said polymeric compound or composition is selected from the following group: block copolymer thermoplastic elastomers, styrene block copolymers, and hydrogenated styrene block copolymers, polyacrylics, polyvinyl alcohol, natural gum or gelatins, polyethylene oxide, polyvinylpyrrolidone , polyvinyl ethers, cellulose derivatives, or combinations thereof. 8. A combination according to any one of the preceding claims, wherein 80% by weight of the adhesive consists of hydrophobic components and most preferably all of the adhesive components are hydrophobic. 9. A disposable absorbent article such as a sanitary napkin or a panty protector for topical adhesive attachment to a user's skin, said article comprising a combination of a substrate with a topical adhesive according to claim 1 for attachment to the skin. 10. The use of a combination according to claim 1 in a disposable absorbent article such as a sanitary napkin or a pantiprotector.