JPS61101585A - Preparation of pressure-sensitive adhesive tape - Google Patents

Abstract

PURPOSE:To obtain a pressure-sensitive adhesive tape with improved anchoring properties by providing a pressure-sensitive adhesive layer after priming a polyolefin sheet having an oxidation-treated surface with a specified crosslinkage copolymer and a photosensitizer, followed by irradiation with light. CONSTITUTION:The surface of a polyolefin sheet is subjected to oxidation treatment such as corona discharge treatment. The treated surface is coated as a primer with an aq. dispersion contg. an alkyl (meth)acrylate-base photo- crosslinkage copolymer such as a reaction product between butyl acrylate/acrylic acid copolymer and N-methylolacrylamide having at least one (meth)acryloyl group in the molecule and having film-forming ability, and a photosensitizer such as benzoin, and dried. The purpose pressure-sensitive adhesive tape is obtd. by placing an emulsion-type pressure-sensitive adhesive layer such as a layer of a butyl acrylate/2-hydroxyethyl acrylate copolymer on the coated surface followed by irradiation with light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing pressure-sensitive adhesive tapes such as pressure-sensitive adhesive tapes, sheets, and labels using a polyolefin sheet as a support.

[Conventional technology]

Conventionally, various self-supporting sheets such as paper, plastic sheets, and metal foils have been used as supports for pressure-sensitive adhesive tapes. Among these, polyolefin sheets such as polyethylene and polypropylene have excellent moisture resistance, chemical resistance, and electrical insulation properties, making them effective supports for a wide range of applications such as packaging, surface protection, and electrical insulation. I can say that.

On the other hand, the pressure-sensitive adhesive provided on this support is
Conventionally, organic solvent solution types have been widely used, but from the standpoint of pollution, hygiene, and cost, they have recently been replaced by emulsion types that do not use organic solvents.

However, an emulsion-type pressure-sensitive adhesive coated and dried on a polyolefin sheet has an essential drawback of poor anchoring properties. Therefore, as a means to improve this, attempts have been made to improve the anchoring property by using a polyolefin sheet that has undergone surface oxidation treatment and introducing functional groups such as carboxyl groups into the polymer of the pressure-sensitive adhesive. Efforts have been made, such as using the catalyst of the crosslinking agent used in the process as an undercoat, but none of these methods have yielded fully satisfactory results.

[Problem that the invention seeks to solve]

From the above viewpoint, this invention solves the problem of poor anchoring properties when an emulsion-type pressure-sensitive adhesive is provided on a polyolefin sheet, and achieves the above-mentioned anchoring properties as well as the good adhesive strength originally required for adhesive tapes. It is an object of the present invention to provide improved methods of manufacturing pressure sensitive adhesive tapes.

[Means for solving problems]

As a result of extensive research in order to solve the above problems, the inventors used a polyolefin sheet with surface oxidation treatment as a support, and found that the interface between this sheet and the emulsion-type pressure-sensitive adhesive layer was The inventors have discovered that by irradiating light in the presence of an undercoat layer, good adhesion and significantly improved anchoring properties can be obtained, leading to the present invention.

That is, the present invention applies a (meth)acrylic acid alkyl ester having at least one (meth)acryloyl group in the molecule and capable of forming a film as an undercoat to the treated surface of a polyolefin sheet subjected to surface oxidation treatment. An aqueous dispersion containing an acrylic photocrosslinkable copolymer (hereinafter referred to as an acrylic photocrosslinkable copolymer) and a photosensitizer is coated and dried, and an emulsion type pressure sensitive adhesive layer is provided thereon, The present invention relates to a method for producing pressure-sensitive adhesive tapes, which is characterized in that the tapes are then irradiated with light.

[Structure and operation of the invention]

°・Materials for the polyolefin sheet used in this invention include polyethylene, polypropylene, poly(1
-butene), etc., and one or both sides of the sheet are oxidized by corona discharge treatment, flame treatment, chemical oxidation treatment, etc. as the surface oxidation treatment of this sheet.

As for the aqueous dispersion containing the acrylic photocrosslinkable copolymer and photosensitizer constituting the lower Q, for example, first, an aqueous dispersion containing the acrylic photocrosslinkable copolymer is prepared, and then it is exposed to light. Obtained by adding and mixing a sensitizer.

The aqueous dispersion containing the above acrylic photocrosslinkable copolymer is
(Meth)acrylic acid alkyl ester copolymer produced by the following method [hereinafter referred to as acrylic copolymer (1)
The functional group-containing unsaturated monomer (n) described later is added to the aqueous dispersion of the above copolymer (the above monomer (n)).
It can be obtained by reacting with.

The aqueous dispersion of the acrylic copolymer (I) above refers to at least one type of (meth)acrylic acid alkyl ester having an alkyl group of 1 to 12 carbon atoms, or these (meth)
Acrylic acid alkyl ester and at least one unsaturated monomer such as vinyl acetate, vinyl propionate, vinylpyridine, (meth)acrylonitrile, (meth)acrylamide, diacetone (meth)acrylamide, and styrene.
99 to 70% by weight of a mixture with seeds and carboxyl group-containing unsaturated monomers such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, allyl acetic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth) ) acrylate, allyl alcohol, monoester of polyethylene glycol and (meth)acrylic acid, pentaerythritol mono(,meth)acrylate, triglycerol mono(meth)acrylate, monovinyl ether of ethylene glycol or polyethylene glycol,
Hydroxyl group-containing unsaturated monomers such as propylene glycol or monovinyl ether of polypropylene glycol,
Unsaturated monomers containing epoxy groups such as glycidyl (meth)acrylate, unsaturated monomers containing N-methylol groups or N-alkoxymethyl groups such as N-methylol(meth)acrylamide, N-(n-butoxymethyl)(meth)acrylamide, etc. It is obtained by copolymerizing 1 to 30% by weight of at least one type of functional group-containing unsaturated monomer such as a saturated monomer by ordinary emulsion polymerization.

The functional group-containing unsaturated monomer (n) added to the aqueous dispersion of the acrylic copolymer (1) includes functional groups contained in the copolymer (1), that is, carboxyl groups and hydroxyl groups. , an epoxy group, an N-methylol group, etc., and an unsaturated monomer having a (meth)acryloyl group in the molecule. As a specific example, among the functional group-containing unsaturated monomers used to obtain the aqueous dispersion of the acrylic copolymer (I), (
Examples include those having a meth)acryloyl group.

The reaction between the acrylic copolymer (1) and the functional group-containing unsaturated monomer (II) is carried out by first adding the unsaturated monomer to an aqueous dispersion of the acrylic copolymer (1) at a low temperature. (n) is sufficiently dispersed, then the temperature is raised, and if necessary, in the presence of dimethylalinine, triethylamine, tripropylamine, tributylamine, imidazole, etc., the acrylic copolymer is produced by heating and stirring at high temperature. The functional group of the union (I) and the functional group of the functional group-containing unsaturated monomer (II) may be reacted.

Through this reaction, the acrylic copolymer (1) (meth)
An aqueous dispersion containing an acrylic photocrosslinkable copolymer having a film-forming ability and having at least one (meth)acryloyl group, preferably 2 to 20 (meth)acryloyl groups in the molecule, is obtained by introducing an acryloyl group.

The primer used in this invention is obtained by adding and mixing a photosensitizer into an aqueous dispersion containing the above-mentioned acrylic photocrosslinkable copolymer, and the photosensitizer used here is , is not particularly limited as long as it promotes the photopolymerization reaction of the photocrosslinkable copolymer.

For example, benzoins such as hengeine, benzoin methyl ether, benzoin ethyl ether, hengeine isopropyl ether, α-methylbenzoin, l
- Anthraquinones such as chloroanthraquinone and 2-chloroanthraquinone, benzophenones such as benzophenone, p-chlorobenzophenone and p-dimethylaminobenzophenone, sulfur-containing compounds such as diphenyl disulfide 1' and tetramethylthiuram disulfide, dimethylbenzyl ketal etc. can be mentioned.

The photosensitizer is added in an amount of 0.05 to 20.1 parts by weight, preferably 0.05 to 10 parts by weight, per 100 parts by weight of the photocrosslinkable copolymer. In addition, the method for adding this photosensitizer is to dissolve it in a small amount of a solvent or other liquid compound that can be blended as an optional component, add it to the aqueous dispersion of the photocrosslinkable copolymer, and stir thoroughly. It is better to disperse it.

The thus obtained undercoat is applied to the treated surface of the polyolefin sheet that has undergone surface oxidation treatment.

It is dried, but it is desirable that the coating thickness after drying be in the range of 0.2 to 5 μm from the viewpoint of improving anchoring performance.

The emulsion-type pressure-sensitive adhesive used in this invention may be natural rubber-based or synthetic rubber-based, but is preferably an acrylic-based emulsion-type pressure-sensitive adhesive of the same type as the primer. Generally, the main monomer is a (meth)acrylic acid alkyl ester (alkyl group having 4 to 10 carbon atoms), which is imparted with functions such as adhesive strength and cohesive strength.

An emulsion obtained by adding a modifying monomer for improvement and emulsion polymerization in an aqueous medium is used.

The above-mentioned modifying monomers include (meth)acrylic acid, itaconic acid, 1. 2-hydroxyethyl (meth)acrylate, (
2-Hydroxypropyl meth)acrylate, N-N-dimethylaminoethyl (meth)acrylate, (meth)acrylamide, N-methylol (meth)acrylamide, glycidyl (meth)acrylate, (meth)acrylonitrile, vinyl acetate, styrene, etc. is used. Examples of these acrylic emulsion type pressure sensitive adhesives include JP-A-57-1) 1368, JP-A-57-143373, and JP-A-58-152078.
Those described in Japanese Patent Application Laid-open No. 57-208256 and the like can also be used.

In this invention, after coating the oxidized surface of the polyolefin sheet with an undercoat consisting of an aqueous dispersion containing an acrylic photocrosslinkable copolymer and a photosensitizer as described above and drying,
Furthermore, the above-mentioned emulsion-type pressure-sensitive adhesive is applied thereon and dried to a dry thickness of 5 to 50 μm to form a pressure-sensitive adhesive layer. After that, the polyolefin sheet and the pressure-sensitive adhesive layer are anchored by irradiating light for 0.3 seconds or more, preferably 3 seconds or more using a light source such as a high-pressure mercury lamp, metal halide lamp, carbon arc lamp, or xenon lamp. Pressure-sensitive adhesive sheets with very good properties and satisfactory adhesive strength and cohesive strength can be obtained.

It should be noted that the reason why the pressure-sensitive adhesive tapes obtained by the present invention have extremely good anchoring properties is not clear. It is speculated that the treated surface of the surface-oxidized polyolefin sheet is further activated by the light irradiation treatment, and the acrylic photocrosslinkable copolymer contained in the undercoat layer undergoes a crosslinking reaction due to the treatment, resulting in the sheet being damaged. While some chemical bonding occurs to the surface, it is thought that the undercoat layer and the pressure-sensitive adhesive layer have relatively good affinity, and that a bonding reaction of the photocrosslinkable copolymer to this adhesive layer also occurs. It is presumed that these factors result in good anchoring performance.

〔Effect of the invention〕

As described above, in this invention, an emulsion-type pressure-sensitive adhesive layer is provided on the oxidized surface of a polyolefin sheet via an undercoat layer containing an acrylic photocrosslinkable copolymer and a photosensitizer, and By employing the light irradiation method, it is possible to obtain pressure-sensitive adhesive tapes that have good adhesive strength and greatly improved anchoring properties.

〔Example〕

Examples of this invention will be described below. In addition, in the following, parts mean parts by weight.

Example 1 2-ethylhexyl acrylate 40 parts Butyl acrylate 40 parts Butyl methacrylate
10 parts acrylic acid
10 parts Sodium dodecyl sulfate 3
154.5 parts ion-exchanged water The above blended composition was charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, heated and stirred at 70°C for 1 hour under a nitrogen stream, and then 0.1 of ammonium persulfate was added, and the mixture was reacted at 70° C. for 5 hours to obtain an aqueous dispersion of an acrylic copolymer.

Next, the aqueous dispersion was cooled to 25°C, 5 parts of glycidyl methacrylate was added, stirring was continued for 12 hours, and then the temperature was raised to 70°C, and 0.2 part of dimethylaniline was added.
Heating and stirring was continued for 5 hours. Next, 3 parts of benzophenone dissolved in toluene was added to this aqueous dispersion and mixed with stirring to obtain an aqueous dispersion containing an acrylic photocrosslinkable copolymer and a photosensitizer.

This material was diluted to 10% by weight with ion-exchanged water, stirred and mixed uniformly, and then applied to the treated surface of a 60 μm thick polyethylene sheet that had been corona treated to a thickness of 0.5% after drying.
It was coated to a thickness of .mu.m and dried by heating at 90.degree. C. for 1 minute. An acrylic emulsion-type pressure-sensitive adhesive prepared by the method described below was applied thereon to a dry thickness of 20 μm, and dried by heating at 90° C. for 3 minutes. Then, using a high-pressure mercury lamp (80 W/(J)), ultraviolet rays were irradiated from the adhesive side for about 5 seconds to prepare a pressure-sensitive adhesive tape original fabric.

Emulsion-type pressure-sensitive adhesive> In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 70 parts of 2-ethylhexyl acrylate, 10 parts of butyl acrylate, 20 parts of methyl methacrylate, and acrylic acid were added. 5 parts of polyoxyethylene alkylphenol ether and 160 parts of ion-exchanged water were heated under a nitrogen stream while stirring. When the contents reached about 60°C, 0% ammonium persulfate was added as a polymerization initiator.
3 parts of the solution was added to initiate polymerization, and the emulsion polymerization reaction was carried out for about 3 hours. After the polymerization was completed, the contents were heated to about 75°C and aged for about 1 hour, and then an aqueous ammonia solution of about 1% by weight was added dropwise with stirring to form an acrylic resin having a viscosity of about 5 voids (at 20°C). An emulsion type pressure sensitive adhesive was manufactured.

Example 2 Butyl acrylate 65 parts Acrylonitrile 15 parts Glycidyl methacrylate 20 parts Sodium dodecyl sulfate
3 parts ion exchange water 154.5
After obtaining an aqueous dispersion of an acrylic copolymer using the above-mentioned composition in the same manner as in Example 1, the aqueous dispersion was cooled to 25°C, and 15 parts of acrylic acid was added. 1
Stirring was continued for 2 hours. Thereafter, the temperature was raised to 70°C, 0.2 part of dimethylaniline was added, and heating and stirring were continued for 5 hours.

Next, 3 parts of benzophenone dissolved in toluene was added to this aqueous dispersion, and the mixture was thoroughly stirred and mixed to obtain an aqueous dispersion containing an acrylic photocrosslinkable copolymer and a photosensitizer. Using this aqueous dispersion, a pressure-sensitive adhesive tape material was produced in the same manner as in Example 1.

Example 3 2-ethylhexyl acrylate 70 parts Ethyl acrylate 15 parts Methyl methacrylate
5. Sodium dodecyl sulfate
3 parts ion exchange water 154.5
After obtaining an aqueous dispersion of an acrylic copolymer using the above-mentioned composition in the same manner as in Example 1, the aqueous dispersion was cooled to 25°C, and 9 parts of glycidyl methacrylate was added. and continued stirring for 12 hours. After that, the temperature was raised to 70°C and heating and stirring was continued for 5 hours, and then 3 parts of benzophenone dissolved in toluene was added, and the mixture was thoroughly stirred and mixed to form an aqueous dispersion containing an acrylic photocrosslinkable copolymer and a photosensitizer. I got a body.

Using this aqueous dispersion, a pressure-sensitive adhesive tape material was produced in the same manner as in Example 1.

The adhesive force and anchoring force of each pressure-sensitive adhesive tape original fabric of Examples 1 to 3 were measured by the following method, and the results were as shown in the table below. For reference, the same table also lists the results of measurements similar to those described above for the original tapes in each example before being irradiated with ultraviolet rays.

Adhesive strength〉 Cut the original pressure sensitive adhesive tape to a width of 20fi, paste it on a degreased 5US304 stainless steel plate (BA finish), leave it for 30 minutes, and then peel it off 180 degrees.Adhesive strength (peeling speed 300m/min) , 20° C., 65% RH).

Anchoring force〉 Rapidly attaches the adhesive layer surfaces of the original pressure-sensitive adhesive tape to each other,
The detachment operation was repeated, and the anchoring force was evaluated by the number of adhesion and detachment operations until the adhesive layer was peeled off from the support sheet.

As is clear from the above table, according to the manufacturing method of the present invention, a pressure-sensitive adhesive tape with good adhesive strength and improved anchoring force can be obtained by applying a specific primer and irradiating with ultraviolet rays. I understand.

Claims (1)

[Claims] (1) Photo-crosslinking of a (meth)acrylic acid alkyl ester having at least one (meth)acryloyl group in the molecule and capable of forming a film as an undercoat on the treated surface of the surface-oxidized polyolefin sheet. Production of pressure-sensitive adhesive tapes, characterized in that an aqueous dispersion containing a sex copolymer and a photosensitizer is coated and dried, an emulsion-type pressure-sensitive adhesive layer is provided thereon, and then light is irradiated. Method.