JPS5991181A - Preparation of pressure sensitive-adhesive tape - Google Patents

Abstract

PURPOSE:To prepare a pressure-sensitive adhesive tape with high adhesive power and anchoring property, by applying a mixed solution of an acryloyl group- containing polymerizable compd. and a photosensitizer and then a pressure-sensitive adhesive to a surface-oxidized polyolefin sheet, followed by irradiation with light. CONSTITUTION:The surface of a polyolefin sheet (e.g. polyethylene sheet) is oxidized by treatment with corona, flame, etc. and a mixed solution of a liquid polymerizable compd. having at least one (meth) acryloyl group in the molecule (e.g. 2-ethylhexyl acrylate) and a photosensitizer (e.g. benzoin) and applied to the treated surface to a dry film thickness of about 0.5-5mum, followed by application of an overcoat of a pressure-sensitive adhesive (e.g. synthetic rubber or acrylic polymer-based pressure-sensitive adhesives) and drying. The sheet is then irradiated with light emitted from a high-pressure mercury lamp, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes specific reagents and light energy to bond a polyolefin sheet and a pressure-sensitive adhesive layer in the production of a pressure-sensitive adhesive tape or sheet having a polyolefin sheet as a support. This article relates to a method for producing pressure-sensitive adhesive tapes that can significantly improve anchoring properties and provide stable adhesive and cohesive strength. Conventionally, paper, plastic sheets, and metal have been used as supports for pressure-sensitive adhesive tapes. Various self-supporting sheets such as foils are used, but polyolefin sheets such as polyethylene and polypropylene have excellent moisture resistance, chemical resistance, and electrical insulation properties, so they are used for packaging, surface protection, electrical insulation, etc. It can be said that it is a significant support for a variety of uses.

However, the pressure-sensitive adhesive layer coated and dried on a polyolefin sheet has an essential drawback of poor anchoring properties, and as a means to improve this, a polyolefin sheet with surface oxidation treatment is used and a pressure-sensitive adhesive layer is used. Attempts have been made to improve anchoring properties by introducing functional groups such as carboxyl groups, and attempts have been made to use catalysts from crosslinking agents used in pressure-sensitive adhesives as primers, but none of them have been sufficient. The reality is that satisfactory results have not been obtained.

The present inventors (c) As a result of intensive research on improving the anchoring properties of a polyolefin sheet and a pressure-sensitive adhesive layer, a surface oxidized polyolefin sheet was used as a support,
It was discovered that the anchoring property is significantly improved by irradiating light with a specific polymerizable compound and a photosensitizer present at the interface between the... and the pressure-sensitive adhesive layer. That is, the present invention provides a mixed solution of a photosensitizer and a polymerizable compound having at least one (meth)acryloyl group in the molecule on the treated surface of a polyolefin sheet subjected to surface oxidation treatment. The present invention relates to a method for producing pressure-sensitive adhesive tapes, which comprises applying a pressure-sensitive adhesive thereon, drying it, and then irradiating it with light.

The polyolefin sheet used in the present invention may be polyethylene, polypropylene, poly(1-butene), or a combination thereof with a polymerizable monomer such as vinyl acetate, (meth)acrylic acid, or alkyl (meth)acrylate. A sheet of a polymer that has been polymerized or graft polymerized can be used, and the surface oxidation treatment of the sheet is one in which one or both sides of the sheet are oxidized by corona treatment, flame treatment, sputtering treatment, chemical oxidation treatment, etc. used.

In addition, as the polymerizable compound having at least one (meth)acryloyl group in the molecule, various derivatives of (meth)acrylic acid that are liquid to semi-solid at room temperature are used, such as 2-ethylhexyl (meth)acrylate, 1・4
-butylene glycol di(meth)acrylate, 1.6
-Hexagelic di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethyl-
Examples include (meth)acrylic acid ester monomers such as I remethane tetra(meth)acrylate, or oligomers such as epoxy (meth)acrylate, urethane (meth)acrylate, and oligoester (meth)acrylate, and these may be used as necessary. Two or more types may be used in combination.

The photosensitizer is not particularly limited as long as it promotes the photopolymerization reaction, but examples include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benozoi/inglovir ether, and α-methylbenzoin; Examples include anthraquinones such as chloroanthraquinone and 2-chloroanthraquinone, benzophenones such as benzophenone, P-chloroy/siphenon, and P-dimethylaminobenzophenone, and sulfur-containing compounds such as diphenyl disulfide and tetramethylthiuram disulfide. The photosensitizer is added in an amount of 0.1 to 20% by weight, preferably 0.5 to 10% by weight, based on the polymerizable compound. The above-mentioned photosensitizer is made into a solution in a usual solvent (for example, toluene, ethyl acetate, etc.), and a predetermined amount of the above-mentioned polymerizable compound is added thereto, and used as a mixture solution.

Further, as the pressure-sensitive adhesive used in the present invention, various kinds of pressure-sensitive adhesives such as commonly used solvent-based or water-based natural rubber or synthetic rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, etc. can be used. According to the present invention, it is particularly useful for water-dispersed types such as emulsions and dispergenes, which are difficult to add cross-linking agents and have difficulty in anchoring, but it is also possible to improve anchoring for solvent-type. I can do it.

The reason why the anchoring effect is exhibited in the present invention is not clear, but the surface of the polyolefin sheet subjected to surface oxidation treatment is more activated by light irradiation, and some chemical bond is formed between it and the polymerizable compound. It is presumed that good anchoring properties appear due to the reaction of the polymerizable compound with the pressure-sensitive adhesive.

To show a specific method for implementing the present invention, first, a polyolefin sheet whose surface has been oxidized is prepared, and a mixed solution of the polymerizable compound and a photosensitizer is applied to the treated surface so that the thickness after drying is After applying a pressure-sensitive adhesive on top of it and drying it, it is coated to a thickness of 0.5 to 5 μm. By irradiating with light for 3 seconds or more, preferably 3 seconds or more, a pressure-sensitive adhesive sheet having very good anchoring properties between the polyolefin sheet and the pressure-sensitive adhesive layer and having stable adhesive force and cohesive force can be obtained.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to these examples.

Note that in the following, parts mean parts by weight, and the adhesive strength and anchoring strength tests were measured by the following methods.

[Adhesive strength]

The prepared pressure-sensitive adhesive tape sample was cut to a width of 20 mm and attached to a degreased 5US304 stainless steel plate.
After standing for 0 minutes, 180 degree peeling adhesive strength (peel speed 3001 minutes, 20° C. x 65% R, H) is measured.

[Anchoring power]

The adhesive surfaces of the produced pressure-sensitive adhesive tape samples were rapidly attached and separated, and a case where the adhesive layer did not peel off from the support sheet was evaluated as good.

Production Example 1 "Production 9 of Pressure Sensitive Adhesive (I)" 80 parts of 2-ethylhexyl acrylate, 20 parts of methyl methacrylate, and acrylic acid were placed in a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser. 5 parts of polyoxyethylene alkylphenol ether, and 160 parts of ion-exchanged water were heated under a nitrogen stream with stirring. When the reaction system reached about 60°C, 0.0 parts of ammonium persulfate was added as a polymerization initiator. Add 3 parts to start polymerization and carry out the polymerization reaction for about 3 hours.After the polymerization is completed, the temperature is about 75°C.
The temperature of the reaction system was raised to 100.degree. C., and the reaction system was aged for about 1 hour to obtain an emulsion composition containing a copolymer. About 3% ammonia aqueous solution was added dropwise to this emulzidine composition while stirring.
An emulsion-type pressure-sensitive adhesive having a viscosity of 20°C (20°C) was produced.

Production Example 2 "Production 7 of Pressure Sensitive Adhesive (U)" 75 parts of butyl acrylate, 25 parts of vinyl acetate, 3 parts of methacrylic acid, 0.2 part of benzoyl peroxide and ethyl acetate were placed in the same reaction vessel as in Production Example 1. 100 parts of the copolymer was charged, and a polymerization reaction was carried out at about 65° C. for 4 hours to produce a solvent-type pressure-sensitive adhesive containing a copolymer.

Example 1 A mixture of 100 parts of trimethylolpronotrimethacrylate and 5 parts of benzophenone was applied to the treated surface of a corona-treated polyethylene sheet having a thickness of 60 μ2n to a thickness of 1 μm. The pressure-sensitive adhesive (I) was applied to a dry thickness of 20 μm, and dried by heating at 90°C for 3 minutes to obtain an original tape.Next, this sample was coated with high pressure Mercury lamp (80W/ce
) for about 5 seconds from a distance of 10 mm to prepare pressure sensitive adhesive tape samples.

Example 2 A 30% solution of ethyl acetate containing 100 parts of tetramethylolmethanetetraacrylate and 5 parts of benzophenone was applied to the treated surface of a corona-treated polypropylene sheet with a thickness of 60 μm V to a thickness of 4 μm, and Production Example 2 was applied thereon. The thickness of the pressure sensitive adhesive (II) obtained after drying is 20 μm.
The original tape was obtained by drying at 100°C for 3 minutes.Next, a pressure-sensitive thin tape sample was prepared by irradiating ultraviolet rays under the same conditions as in Example 1.Comparison Example 1 The pressure sensitive adhesive CI) of Production Example 1 was applied to the corona-treated surface of the same polyethylene sheet as in Example 1 to a thickness of 20 mm after drying.
The tape sample was prepared by applying ultraviolet rays under the same conditions as in Example 1.

Comparative Example 2 A solution of 100 parts of trimethylolpropane triacrylate and 5 parts of topenzo-7enone in ethyl acetate was applied to a thickness of 4 μm on the corona-treated surface of the same polyethylene sheet as in Example 1. Ultraviolet rays were irradiated under the same conditions. Next, the pressure-sensitive adhesive CI) of Production Example 1 was applied to the coated and irradiated surface so that the thickness after drying was 20 μm, and the tape sample was prepared by heating and drying at 90° C. for 3 minutes.

The results of testing the adhesive strength and anchoring strength of the pressure-sensitive adhesive tape samples of Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in Table 1.

Chapter 1 Table Patent application/person Nitto Electric Industry Co., Ltd. Representative Kamigata Sanbe 540-

Claims (1)

[Claims] Applying a mixed solution of a polymerizable compound having at least one (meth)acryloyl group in the molecule and a photosensitizer to the treated surface of the surface-oxidized polyolefin sheet,
A method for producing pressure-sensitive adhesive tapes, which comprises applying a pressure-sensitive adhesive thereon, drying it, and then irradiating it with light.