JPH04117475A - Re-releasable pressure sensitive adhesive composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to adhesive removable adhesive sheets used for label stickers, tapes, building materials, packaging materials, electronics, etc. More specifically, the present invention relates to a pressure-sensitive adhesive composition used in a removable pressure-sensitive adhesive sheet that has the function of preventing scratches and dust adhesion on the surface of an adhered article.

(Prior art) Conventionally, removable adhesives have been made by adding and blending plasticizers, tackifying resins, or silicone resins to natural rubber or acrylic copolymers to suppress the increase in adhesive strength over time and to prevent removable adhesives from increasing over time. Products with easy removability are known. However, the method of blending the above additives tends to cause variations in release properties, and the compatibility of the compounding agent with the acrylic copolymer, which is the base polymer of the adhesive, is not necessarily good. If a pressure-sensitive adhesive sheet is attached to an article and then peeled off after being stored under high temperature and high humidity conditions, a portion of the adhesive is transferred to the surface of the article and contaminates the article.

In order to improve the above-mentioned drawbacks, JP-A-2-123182 describes a removable adhesive containing a copolymer containing a silicone macromer as a compounding agent.
The compatibility between the acrylic copolymer base polymer and the copolymer containing a silicone macromer as a component is still not good, and it does not have sufficient performance as a removable adhesive.

(Problems to be Solved by the Invention) The present invention can be applied to adhered articles such as To provide a removable adhesive that can be easily peeled off without remaining on the surface.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides 100 parts by weight of an acrylic copolymer containing (meth)acrylic acid alkyl ester as a main component and a functional group-containing monomer as a copolymerization component, and the above-mentioned functional group-containing monomer. Contains a reactive functional group and has a viscosity of 5 to 10,000 at room temperature
0 centistokes of reactive silicone oil.
This is a removable pressure-sensitive adhesive composition containing 05 to 50 parts by weight.

In the present invention, the acrylic copolymer contains (meth)acrylic acid alkyl ester as the main component, that is, 50 to 99.9% by weight of the acrylic copolymer, and contains functional group-containing monomers as other copolymer components, as necessary. Other copolymer components may be included depending on the situation.

The (meth)acrylic acid alkyl ester is an alkyl ester having 1 to 14 carbon atoms in the alkyl group, and more specifically, the following compounds can be exemplified. Acrylic acid esters of linear or branched aliphatic alcohols such as methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, etc. and corresponding methacrylic acid esters, etc. The (meth)acrylic acid alkyl ester preferably used is an alkyl ester having an alkyl group having 4 to 12 carbon atoms.

The functional group-containing monomer used as an essential component in the acrylic copolymer of the present invention includes a carboxyl group, a hydroxyl group, a methylol group, an amino group, an amide group, a glycidyl group, a phosphoric acid group, a sulfonic acid group, and an ethyleneimine group. Specific examples include the following compounds. Acrylic acid, methacrylic acid, maleic anhydride, maleic acid, maleic acid monoester, itaconic acid, crotonic acid, 2-
Hydroxylpropyl acrylate, polyethylene glycol acrylate, N-methylol acrylamide,
N-methylolmethacrylamide, N-methylaminoethyl acrylate, N-tributylaminoethyl acrylate, N,N-dimethylaminoethyl acrylate,
N,N-dimethylaminoethyl methacrylate, acrylamide, vinylpyrrolidone, glycidyl acrylate, glycidyl methacrylate, mono-(2-hydroxyethyl-α-chloroacrylate) acid phosphate, and the like.

The above functional group-containing monomer is an acrylic copolymer of 0.1 to
Contains 25% by weight.

The acrylic copolymer of the present invention may contain the following monomers in addition to the above monomer components. vinyl ester,
Vinylpyridine, vinyl acetate, vinyl propionate, styrene, acrylonitrile, methacrylonitrile, butadiene, chlorobrene, etc.

The acrylic copolymer of the present invention can be produced by solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization, etc. Polymerization initiators used during polymerization include peroxides such as bezoyl peroxide, lauryl peroxide, and cumene peroxide, azo compounds such as abbisisobutyronitrile, and persulfate compounds such as ammonium persulfate and potassium persulfate. There is.

Examples of organic solvents used when producing the acrylic copolymer of the present invention by solution polymerization include n-pentane, toluene, benzene, n-hexane, dioxane, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, etc. Alcohols such as alcohol, ethyl alcohol, and isopropyl alcohol may be mixed.

In the present invention, the reactive silicone oil is used at room temperature (25
°C) is 5 to 100,000 centistokes, preferably 5 to 10,000 centistokes, has a diorganosiloxane skeleton such as polydimethylsiloxane, and has a hydroxyl group, an amino group, an epoxy group,
Contains functional groups such as carboxylic acid groups and thiol groups. If the viscosity of the silicone oil is greater than 100,000, the compatibility with the acrylic copolymer will be poor, which is not preferable.

Specific examples of reactive silicone oils include the following.

Compound example 1 Side chain modified compound example 2 Single end modified compound example 3 Both end modified type (R is a methyl group, ethyl group, phenyl group, methoxy group, ethoxy group, R゛ is an alkylene group, -(CH2 )
, −〇−(CH) , −(However, k, I! are 1
Indicates an integer of ~8. ), X is a functional group such as a hydroxyl group, an amino group, an epoxy group, a carboxylic acid group, a thiol group, n, m
represents an integer from 1 to 300. ) The reactive silicone oil is selected to have a functional group that reacts with the functional group contained in the acrylic copolymer. The amount of reactive silicone oil blended is 0.05 to 50 parts by weight, preferably 0.1 to 20 parts by weight, based on 100 parts by weight of the acrylic copolymer. The lower limit of the amount to be blended is limited by the removability function, and the upper limit to the amount to be blended is limited by the poor adhesion to the supporting substrate, the adhesion to the adhered article, or the transparency of the adhesive layer.

The pressure-sensitive adhesive composition of the present invention may contain compounds having a crosslinking function such as isocyanate compounds, chelate compounds, melamine compounds, epoxy compounds, and aziridine compounds.

The removable pressure-sensitive adhesive composition of the present invention is applied to a film-like substrate such as polyethylene or polypropylene to a thickness of 5 to 30 μm. The obtained pressure-sensitive adhesive sheet is used as a surface protection material, a masking material, etc. to prevent scratches during processing or transportation of articles.

It can also be used as an adhesive for labels, stickers, building materials, packaging materials, and electronics.

(Example) The present invention will be explained below with reference to Examples. In the examples, "part" means part by weight, and "%" means % by weight.

Example 1 314 equipped with stirrer, thermometer, cooler, and dropping funnel
The following monomers were prepared in a 0 flask and solution polymerization was carried out to obtain an acrylic copolymer.

n-Butyl acrylate 76 parts Methyl methacrylate 20 parts Acrylic acid
3 parts benzoyl peroxide 1 part ethyl acetate
A pressure-sensitive adhesive composition was obtained by blending 7 parts of amino group-containing reactive silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: XF859: viscosity: about 60 centistokes) into a solution containing 100 parts of the obtained acrylic copolymer. Ta.

Example 2 Solution polymerization was carried out in the same manner as in Example 1 except that the monomer formulation was changed to the following.

2-ethylhexyl acrylate 28 parts n-butyl acrylate 40 parts Vinyl acetate
20 parts acrylic acid
7 parts 2-hydroxyethyl methacrylate 3 parts azobisbutyronitrile 0
．． 2 parts 180 parts ethyl acetate 100 parts of the obtained acrylic copolymer was added with a diisocyanate compound (Japan Polyurethane Industries Co., Ltd., trade name: Coronate)
3 parts of were added. Next, epoxy group-containing reactive silicone oil (manufactured by Chisso Corporation, trade name B2405, viscosity approximately 2
0,000 centistokes) to obtain an adhesive composition. complete.

Example 3 An acrylic copolymer was obtained by emulsion polymerization using the following monomer formulation.

n-Butyl acrylate 68 parts Ethyl acrylate 10 parts Methyl methacrylate 10 parts Acrylic acid
5 parts glycidyl methacrylate
3 parts ammonium persulfate 0
．． 1 part polyvinyl alcohol 60 parts ion-exchanged water 160 parts Hydroxyl-modified silicone oil (manufactured by Toshi Silicone Co., Ltd., trade name 5) was added to the emulsion containing 100 parts of the obtained acrylic copolymer.
10 parts of F8427 (viscosity: approximately 320 centistokes) were blended to obtain a pressure-sensitive adhesive composition.

Comparative Example 1 Polyether silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KF) that does not have functional groups in the acrylic copolymer of Example 1
618) to obtain an adhesive composition.

Comparative Example 2 An adhesive was obtained by blending 7 parts of silicone macromer (manufactured by Toagosei Kagaku Kogyo Co., Ltd., trade name HK-20) with the acrylic copolymer of Example 2.

Comparative Example 3 10 parts of an anionic silicone oil aqueous dispersion (manufactured by Shin-Etsu Chemical Co., Ltd., KF700) was blended with the acrylic copolymer of Example 3 to obtain an adhesive.

The adhesive solution obtained on each side was applied to a 25 μm thick polyethylene film whose surface had been corona-treated, and then heated and dried to obtain a surface protection adhesive sheet having a 10 μm thick adhesive layer.

This pressure-sensitive adhesive sheet was subjected to the following tests, and the results are shown in Table 1. The test items are as follows.

Initial adhesion strength The adhesive sheet was attached to a stainless steel plate (S) with a thickness of 0.4 Iu1
US304 No. 1200 polished) at 23℃, JI
Roll pressure according to S, and immediately test the peel strength with a Schopper type peel tester (180° beer, tensile speed 300 m +
n/min) was measured.

Adhesive strength over time In accordance with the initial adhesive strength test, the adhesive sheet was attached to a stainless steel plate, left at 70°C for 7 days, and peel strength after cooling to 23°C was measured.

After pasting the actual removable adhesive sheet on a stainless steel plate, it was heated at 23°C and 60°C.
After being left under the conditions of °C - 95% RH and 70 °C for 7 days and cooled to 23 °C, the removability (adherent contamination, floating phenomenon) was sensory evaluated. Wrinkle,
○ If there is no tearing, and after peeling, there is no problem with adhesive transfer, substrate breakage, or adherend contamination, check if there are any wrinkles, lifting, etc. Evaluation was made as △ if there was no body staining or adhesive transfer, and × if there was significant wrinkles or lifting or poor contamination of the adherend.

Adhesion to the surface substrate The adhesive layer applied to the adhesive sheet was scratched with a spatula, and the scratched area was rubbed to perform a thumb sensory evaluation. ○ is when the adhesive does not peel off from the surface substrate, △ is when the adhesive is slightly peeled off but remains on the surface substrate, and × is when the adhesive is completely peeled off from the surface substrate. evaluated.

Transparency was determined visually. ○ If the transparency is not lost at all
A case where some turbidity occurred was evaluated as △, and a case where there was no transparency at all was evaluated as ×.

〔Effect of the invention〕

The removable pressure-sensitive adhesive composition of the present invention grafts or crosslinks polyorganosiloxane onto the acrylic copolymer by reacting the reactive silicone oil with the acrylic copolymer. Therefore, it has an excellent balance between adhesion to the support, adhesion to the adhered article, and removability.

Moreover, the protective sheet using the adhesive composition of the present invention is
Even if the adhesive is peeled off after being attached to an article and stored under high temperature and high humidity for a long period of time, the adhesive will not migrate onto the surface of the article and cause contamination.

Claims (1)

[Claims] 1 100 parts by weight of an acrylic copolymer containing (meth)acrylic acid alkyl ester as a main component and a functional group-containing monomer as a copolymerization component, which has a functional group that can react with the above-mentioned functional group-containing monomer, and has a viscosity at room temperature. 0.05 to 100,000 centistokes of reactive silicone oil
A removable adhesive composition containing 50 parts by weight.