JPH0120196B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive sheet with excellent water resistance, moisture resistance, and adhesive properties, which is obtained by applying an aqueous synthetic resin dispersion to plastic films, fibers, and papers. Conventionally, pressure-sensitive adhesive sheets have been widely produced industrially using synthetic resin aqueous dispersions obtained by emulsion polymerization of various ethylenically unsaturated monomers in water for plastic films, fibers, and papers. ing. However, these synthetic resin aqueous dispersions are usually made by emulsifying various ethylenically unsaturated monomers in the presence of a surfactant called an emulsifier or a synthetic or natural water-soluble polymer called a protective colloid. Since these synthetic resin aqueous dispersions are manufactured by polymerization, pressure-sensitive adhesive sheets made by applying these synthetic resin aqueous dispersions to plastic films, fibers, and papers have poor water resistance and moisture resistance due to the adverse effects of emulsifiers or protective colloids. , and had poor adhesive properties. As a result of intensive studies, the inventors of the present invention have invented a pressure-sensitive adhesive sheet that does not have the above-mentioned drawbacks. That is, according to the present invention, 20 to 99.8 mol% of a water-soluble ethylenically unsaturated monomer (A ₁ ) and 0 to 79.8 mol% of a generally water-insoluble ethylenically unsaturated monomer (A ₂ ); Organic thiol compound (A ₃ ) 0.2 to 40 mol% (A ₁ ), (A ₂ ) and (A ₃ ) are 100 mol%)
is reacted in water in the presence of a radical-forming catalyst, and the total amount of (A ₁ ), (A ₂ ), and (A ₃ ) is 0.5 to 20 parts by weight, and an alkyl group having an alkyl group having 4 to 15 carbon atoms is added. Emulsion polymerization of 100 parts by weight of a monomer mixture consisting of 50 to 100 parts by weight of (meth)acrylate (B ₁ ) and 0 to 50 parts by weight of other copolymerizable ethylenically unsaturated monomers (B ₂ ) A pressure-sensitive material with excellent water resistance, moisture resistance, and adhesive properties is obtained by applying an aqueous polymer dispersion having a Tg value of -60°C to -10°C onto a base sheet and drying it. An adhesive sheet is provided. Here, the water-soluble ethylenically unsaturated monomer (A ₁ ) used to produce the aqueous polymer dispersion used in the present invention means that the monomer itself is water-soluble and , is a monomer whose homopolymer is water-soluble. For example, unsaturated monobasic acids such as acrylic acid, methacrylic acid, crotonic acid, vinyltoluenesulfonic acid, vinylsulfonic acid, acrylic acid or methacrylic acid, sulfoalkyl and/or these salt, itaconic acid,
Examples include ethylenically unsaturated monomers having carboxylic acid and/or sulfonic acid groups such as unsaturated dibasic acids such as maleic acid and fumaric acid and/or salts thereof or monoesters thereof. In addition, vinylpyridine, which imparts cationic properties,
Monovinylpyridines such as 2-methyl-5-vinylpyridine, 2-dimethylaminoethyl acrylate or methacrylate, β-(t-butylamino)ethyl acrylate or methacrylate, 2-hydroxy-3-acryloxypropyltrimethylammonium or esters containing an amino group capable of forming a cationic salt of acrylic acid or methacrylic acid, such as a salt of methacryloxypropyltrimethylammonium, and vinyl ethers containing an alkylamino group, such as 2-dimethylaminoethyl vinyl ether. ,N-(2
- dimethylaminoethyl) acrylamide or methacrylamide containing an alkylamino group such as acrylamide or methacrylamide, preferably a hydrophilic ethylenically unsaturated compound having a residue capable of forming a cationic salt in the molecule. Monomers are used. When non-ionic properties are desired, α,β unsaturated acids such as acrylamide and methacrylamide, or derivatives thereof such as N-methylolacrylamide and methoxymethylacrylamide, and α,β unsaturated acids such as hydroxyalkyl acrylate or methacrylate are used. Water-soluble unsaturated monomers such as hydroxyalkyl esters of acids, hydroxyalkyl vinyl ethers, vinyl pyrrolidone, and allyl alcohol are used. Two or more of these can be used in combination, except that those that provide anionic properties and those that provide cationic properties cannot be used together. Furthermore, in the present invention, a water-insoluble ethylenically unsaturated monomer (A ₂ ) can generally be used in combination with the above-mentioned water-soluble ethylenically unsaturated monomer (A ₁ ). Such a monomer (A ₂ ) is a monomer which is either water-insoluble itself or whose homopolymer is water-insoluble, and the following monomers are used, for example. Vinyl esters such as vinyl acetate, vinyl propionate, and vinyl versatate (tertiary carboxylic acid); alkyl acrylates, alkyl methacrylates, dialkyl maleates, dialkyl fumarates, and dialkyl itaconates; Saturated carboxylic acid esters, α-olefins such as ethylene and propylene, aromatic vinyls such as styrene and α-methylstyrene, vinyl halides or vinylidenes such as vinyl chloride, vinylidene chloride, and vinylidene fluoride, acrylonitrile, butadiene , alkyl vinyl ethers, etc. Further, as the organic thiol compound (A ₃ ) represented by the general formula R-(SH)n, lauryl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n
- Alkyl mercaptans such as tetradecyl mercaptan n-octadecyl mercaptan, benzyl mercaptan, dodecyl benzimercaptan,
Aromatic mercaptans such as P-chlorobenzyl mercaptan, thiocarboxylic acids such as thioglycolic acid, mercaptopropionic acid, thiomalic acid, thiosuccinic acid, thiobenzoic acid, or salts thereof;
Or n-butyl-3-mercaptopropionate, n-butylthioglycolate, ethylthioglycolate, isooctylthioglycolate,
Thiocarboxylic acid alkyl esters such as dodecyl thioglycolate, dodecyl-3-mercaptopropionate, octadecyl-3-mercaptopropionate, tridecylthioglycolate, monoethanolamine thioglycolate, 2-dimethylaminoethanethiol hydro chloride,
diaminopropanethol hydrochloride,
Nitrogen-containing thiols such as 2-mercaptoamine hydrochloride, 2,2'-dimercapto diethyl ether, dithiol terephthalic acid, glycol dimercaptoacetate, pentaerythritol tetrathioglycolate, trimethylolethane trithioglycolate, trimethylolpropane Examples include polythiols such as trithioglycolate. Further, two or more of these organic thiol compounds may be used in combination. The usage ratio of these compounds is 20 to 99.8 mol% of water-soluble ethylenically unsaturated monomer (A ₁ ), generally 0 to 79.8 mol% of water-insoluble unsaturated monomer (A ₂ ), and general formula R- It is appropriate to use 0.2 to 40 mol% of the organic thiol compound (A ₃ ) represented by (SH)n (the total of A ₁ A ₂ A ₃ is 100 mol %), but in order to smoothly proceed with the subsequent emulsion polymerization, When applied to the base sheet, in order to sufficiently impart the various properties of water resistance, moisture resistance, and adhesiveness described above, (A ₁ ); 20 to 99.5 mol%; (A ₂ ); 0 to 50 mol%; (A ₃ ); 0.5 to 30 mol% is preferable. The water-soluble ethylenically unsaturated monomer (A ₁ ), generally water-insoluble ethylenically unsaturated monomer (A ₂ ), and organic thiol compound (A ₂ ) described above are hydrophilic in water or in contact with water. The reaction is carried out by a conventional radical polymerization method using a radical-generating catalyst such as hydrogen peroxide, potassium persulfate, benzoyl peroxide, or azobisisobutyronitrile in a mixed solvent with an organic solvent. In general, radical generation catalysts are based on the sum of monomers (A ₁ ) to (A ₃ ).
Use 0.05-5% by weight. Here, (A ₁ ), (A ₂ ), and (A ₃ ) do not necessarily need to be completely reacted, and are generally heated at 20 to 90°C.
It is sufficient to react for about 15 minutes to 15 hours. (A ₁ ), (A ₂ ), (A ₃ ) reacted as above
The pH of the reaction product is adjusted as desired. Next, in the presence of the reaction products of (A ₁ ), (A ₂ ), and (A ₃ ), alkyl (meth)acrylate (B ₁ ) having an alkyl group having 4 to 12 carbon atoms and other copolymerizable Ethylenically unsaturated monomer (B ₂ ) is polymerized. Here, the monomers (B ₁ ) and (B ₂ ) are
Total weight of (A ₁ ) to (A ₃ ) Monomer (A ₁ ) to (A ₃ )
It is added in such a proportion that the total weight is 100 parts by weight, preferably 1 to 10 parts by weight. The usage ratio of monomers (B ₁ ) and (B ₂ ) is (B ₁ )=
For 50-100 parts by weight, (B ₂ )=50-0 parts by weight. Examples of the alkyl (meth)acrylate (B ₁ ) having an alkyl group having 4 to 12 carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and the like. Other copolymerizable ethylenically unsaturated monomers (B ₂ ) include vinyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, vinyl acetate, and vinyl propionate. , (meth)acrylic acid, itaconic acid, fumaric acid and other unsaturated carboxylic acids and/or their salts, half esters, styrene, acrylonitrile, ethylene, propylene, butadiene, other acrylamides, N-methylolacrylamide, glycidyl (meth) ) acrylate, β-hydroxy (meth)acrylate, etc. These monomers have _a Tg value of -60°C to _-10 °C, particularly preferably _- One or more types are used, selected so that the temperature ranges from 60°C to -20°C. Monomers B ₁ and B ₂ are polymerized using a method similar to known emulsion polymerization. That is, the above (A ₁ ),
In the presence of the reaction products of (A ₂ ) and (A ₃ ), alkyl (meth)acrylate (B ₁ ) and other monomers (B ₂ ) are added dropwise at once, in portions, or continuously. Then, polymerization is carried out at a temperature range of 0°C to 100°C using a radical-generating catalyst similar to the above-mentioned initial reaction or a redox-based catalyst using these in combination with metal ions and a reducing agent. In general, radical-generating catalysts contain monomers (B ₁ ), including those contained in the reaction products of (A ₁ ) to (A ₃ ).
and 0.05 to 5% by weight based on (B ₂ ). The aqueous polymer dispersion thus obtained is practically used in the base sheet at a solids concentration of 20 to 60% by weight, more preferably 40 to 60% by weight. The method for obtaining a pressure-sensitive adhesive sheet by applying the obtained aqueous polymer dispersion to a base sheet such as plastic films, fibers, and paper is to directly apply the aqueous polymer dispersion to the plastic film that is the base material. and fibers or paper, and after drying, a release paper is placed on the polymer film surface to form a pressure-sensitive adhesive sheet, or as is commonly done in industry, the above-mentioned material is coated on a release paper and dried. The pressure sensitive adhesive sheet of the present invention can be obtained by pressure transfer onto a base sheet. In this case, fillers, pigments, organic solvents, plasticizers, tackifiers, etc. may be mixed with the aqueous polymer dispersion as required. Further, when the aqueous polymer dispersion is uniformly applied to a plastic film or release paper having a low surface tension, a surfactant and/or a thickener called a wetting agent may be added. Naturally, they are limited to those that can exhibit their effects without deteriorating the various physical properties such as water resistance, moisture resistance, and adhesiveness described above. When using a known wetting agent or thickener, for 100 parts by weight of the aqueous polymer dispersion,
It is preferable that the effect is exhibited when the amount of each solid content is 0.5 parts by weight or less, preferably 0.3 parts by weight or less. However, this does not apply when the wetting agent and thickening agent are water-insoluble or volatile. Examples of wetting agents that can exhibit their effects within the above range of addition amounts include fluorine-based surfactants (trade name "Megafuck"; manufactured by Dainippon Ink & Chemicals Co., Ltd.), and polyacrylic acid as thickeners. salt,
Polyacrylamide (product name "Rheozyk"; manufactured by Nippon Pure Chemical Industries, Ltd., product name "Ryufrozk";
(manufactured by Dainippon Ink and Chemicals Co., Ltd.), a polyoxyalkylene compound (trade name "UNIYAF"; manufactured by NOF Corporation), and the like. Furthermore, examples of volatile wetting agents include acetylene derivative surfactants (trade name "Surfinol"; manufactured by Air Products) and the like. In addition, thermosetting resins such as phenol resins, urea resins, melamine resins, epoxy resins, and urethane resins are added and mixed to the aqueous polymer dispersion in order to improve the cohesive force, water resistance, and moisture resistance of the aqueous polymer dispersion. However, it may then be applied to plastic films, fibers, and papers to obtain pressure-sensitive adhesive sheets. Next, the present invention will be explained in detail with reference to Examples. The following parts and percentages are by weight unless otherwise specified. Example 1 (1) A condenser, a thermometer, and a dropping funnel were attached to a stainless steel reaction vessel equipped with a stirrer. In a vessel purged with nitrogen, 15 parts of methacrylic acid, 5 parts of t-dodecyl mercaptan, 3 parts of potassium persulfate, and deionized were added. Add 540 parts of water, adjust the temperature inside the container to 80℃,
The reaction mixture was stirred for 30 minutes. Thereafter, the pH of the system was adjusted to 9 using 28% ammonia water. (2) Next, add the premixed monomer mixture (2-ethylhexyl acrylate 700
(280 parts of vinyl acetate, 20 parts of acrylic acid) and a polymerization catalyst solution (3 parts of potassium persulfate dissolved in 80 parts of deionized water) were added dropwise over 180 minutes to effect polymerization. During this time, the temperature inside the container was 80±2
It was kept at ℃. Then, after cooling the contents to 30℃ 28
The pH was adjusted to 6-7 with % ammonia water. Further, the solid content was adjusted to 60% with deionized water and passed through 100 mesh. The obtained aqueous polymer dispersion had a solid content concentration of 60%, a pH of 6.4, and a viscosity of
It was 270 cps (measured at 25°C with a BM type rotational viscometer). The Tg value of the polymer was approximately -35°C.
This is referred to as dispersion liquid A-1. For comparison, methacrylic acid and t-
Without using the reaction product obtained by reacting dodecyl mercaptan, sodium lauryl sulfate and HLB17 as emulsifiers
A monomer mixture having the same composition as in Example 1 (2) was emulsion polymerized using polyoxyethylene nonyl phenol ether, and the solid content concentration was then adjusted to 55%. This was designated as dispersion B-1. The above dispersions A-1 and B-1 were applied to each base sheet of high quality paper (65 g/m ² ), 25μ thick polyvinyl chloride, polyester, and oxidized polypropylene, in an amount (dry) of 30 g/m ^{2 .} It was coated using a rod bar coater and dried for 3 minutes in a hot air dryer at 100°C. After cooling at room temperature, a release paper was placed on the polymer film surface to obtain a pressure-sensitive adhesive sheet. Table 1 shows the physical properties of the pressure-sensitive adhesive sheet.

[Table] Example 2 To 100 parts each of the dispersion A-1 obtained in Example 1 and the dispersion B-1 as a comparative example, 0.05 part of wetting agent Megafuck F-142D was added, and the amount was further increased. Adhesive Unisafe VI-1300 (solid content concentration 25%)
Add 0.6 parts each and stir to make dispersion A-1 13,000 cps.
(BM type viscometer at 25°C), the dispersion B-1 was thickened to 11000 cps to obtain a pressure sensitive adhesive. This pressure-sensitive adhesive was applied to a release paper using a rod bar coater to a coating weight (dry) of 30 g/m ² and dried for 3 minutes in a hot air dryer at 100°C. After cooling at room temperature, high-quality paper (65 g/m ² ) or polyester with a thickness of 25 μm was layered and pressure-transferred to obtain a pressure-sensitive adhesive sheet. Table 2 shows the physical properties of the pressure-sensitive adhesive sheet.

[Table] <Test method> Same as Example 1.
Example 3 (1) In the same manner as in Example 1, 30 parts of acrylic acid, 30 parts of butyl acrylate, 5 parts of thioglycolic acid, 4 parts of potassium persulfate, and 600 parts of deionized water were added to a stainless steel reaction container, and the inside of the container was The temperature was adjusted to 80°C. The mixture was stirred at the same temperature for 30 minutes to react. Thereafter, the pH was adjusted to 9 using 28% ammonia water. (2) Then 3 parts of a 0.5% aqueous solution of FeCl ₃ .6H ₂ O were added, followed by 4 parts of sodium formaldehyde sulfoxylate. While adjusting the reaction temperature to 60°C, a monomer mixture (800 parts of 2-ethylhexyl acrylate, 190 parts of methyl acrylate, 10 parts of methacrylic acid) and a polymerization catalyst solution (4 parts of ammonium persulfate) were mixed in a separate container. (dissolved in 50 parts of deionized water) was added dropwise over 180 minutes to polymerize. During this time, the temperature inside the reaction vessel was maintained at 60±2°C. Further at the same temperature 30
Stir for a minute. Thereafter, the contents were cooled to 30°C and adjusted to pH 7-8 with 28% ammonia water. In addition, the solid content concentration
The concentration was adjusted to 60% with deionized water. The obtained polymer dispersion had a solid content concentration of 60%, a pH of 7.5, and a viscosity of
480 cps, and the Tg value of the polymer was about -36°C. This was designated as dispersion A-2. For comparison, sodium lauryl sulfate and polyoxyethylene nonyl phenol ether of HLB15 were used instead of using the reaction product obtained by reacting acrylic acid, butyl acrylate, and thioglycolic acid in (1). After emulsion polymerization of a monomer mixture having the same composition as in Example 3 (2), a dispersion liquid adjusted to have a solid content concentration of 55% was designated as Dispersion B-2. For 100 parts each of the above Fuchisanzu A-2 and B-2,
Add 0.05 part of wetting agent Megafuck F-142D,
Furthermore, as a thickener, 5% aqueous solution of Rheozyk 2522
(manufactured by Nippon Pure Chemical Industries, Ltd.) in 4 parts for dispersion A-2,
Six parts of dispersion B-2 were added, and then the pH was adjusted to 8 with 28% aqueous ammonia, and the viscosity was thickened using a high-speed stirrer.
Dispersion A-2 has a viscosity of 8500 cps, and Dispersion B-2 has a viscosity of 8500 cps.
The viscosity was increased to 9,000 cps, and this was coated on release paper in the same manner as in Example 2, and after drying, it was pressure-transferred to high-quality paper and polyester film to obtain a pressure-sensitive adhesive sheet. Table 3 shows the physical properties of the pressure-sensitive adhesive sheet.

[Table] <Test method> Same as Example 1.
Example 4 (1) In the same manner as in Example 1, 90 parts of a 50% aqueous solution of formate of dimethylaminoethyl methacrylate (PH4.2), 20 parts of 2-ethylhexyl acrylate, and 2-dimethylaminoethanethiol were placed in a stainless steel reaction vessel. 4 parts of hydrochloride, 2,
4 parts of 2'-azobis(2-amidinopropane) hydrochloride, 280 parts of deionized water and 140 parts of isopropyl alcohol were added, the temperature inside the container was adjusted to 75°C, and the mixture was stirred for 30 minutes to react. (2) Then add 420 parts of deionized water and
Three parts of a 0.5% aqueous solution of FeCl ₃ .6H ₂ O were added. Next, adjust the temperature inside the container to 70℃, and mix the monomer mixture (butyl acrylate) in another container.
600 parts, 375 parts of 2-ethylhexyl acrylate,
15 parts of methacrylic acid, 12.9 parts of formate of dimethylaminoethyl methacrylate) and polymerization catalyst solution (5 parts
% hydrogen peroxide solution) was added dropwise over 180 minutes to polymerize. During this time, the temperature inside the container was maintained at 70±2°C. After the dropwise addition was completed, the mixture was stirred for 1 hour. After cooling to 30°C, the solid content concentration was adjusted to 50% with deionized water. The obtained dispersion has a solid content concentration of 50% and a viscosity of
The Tg value of the polymer was approximately -45°C at 260cps and PH4.0. To 100 parts of this dispersion, 1.2 parts of a toluene solution (solid content 30%) of polyepoxide (Epicron 850; manufactured by Dainippon Ink and Chemicals Co., Ltd.) was added and mixed. This was designated as dispersion A-3. The above dispersion A-3 was applied to a polyvinyl chloride or polyester base material with a thickness of 25 μm using a rod bar coater at a coating amount (dry) of 30 g/m ² , and placed in a hot air dryer at 100°C. Dry for 3 minutes. After cooling at room temperature, a release paper was placed on the polymer film surface to obtain a pressure-sensitive adhesive sheet. Further, dispersions A-2 and B-2 (dispersions before adding a wetting agent and a thickener, respectively) obtained in Example 3 were processed in the same manner as above to obtain a pressure-sensitive adhesive sheet. Table 4 shows the physical properties of the pressure-sensitive adhesive sheet.

[Table] Examples 5 to 10 An aqueous polymer dispersion was prepared in the same manner as in Example 1 using the reaction components A ₁ , A ₂ , A ₃ , B ₁ and B ₂ shown in Table 5 below and the polymerization catalyst. Obtained. Next, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 using the obtained aqueous polymer dispersion and high-quality paper and polyester as the base material. Show its physical properties.
6.

【table】

【table】

[Table] Comparative Example 5 (1) Instead of 15 parts of methacrylic acid, 15 parts of 2-ethylhexyl acrylate and 15 parts of vinyl acetate were used.
The same operation as in Example 1 was repeated, except for using a 100-mesh cloth, and the same operation as in Example 1 was repeated for (2). In many cases, it was not possible to obtain a control aqueous dispersion of the polymer. Therefore, it was not possible to obtain a pressure-sensitive adhesive sheet, and the physical properties were not evaluated. Comparative Example 6 (1) The same procedure as in Example 1 was repeated, except that no t-dodecyl mercaptan was used. (2) Then 800 parts of 2-ethylhexyl acrylate and 200 parts of methyl methacrylate are added as a premixed monomer mixture in a separate container.
When the same procedure as in Example 1 was repeated except for using a 100-mesh cloth, there were too many aggregates and it was impossible to filtrate. It was not possible to obtain an aqueous polymer dispersion. Therefore, in this case as well, it was not possible to obtain a pressure-sensitive adhesive sheet, and the physical properties were not evaluated.

Claims (1)

[Claims] 1 Water-soluble ethylenically unsaturated monomer (A ₁ ) 20~
99.8 mol% and water-insoluble ethylenically unsaturated monomer (A ₂ ) 0 to 79.8 mol% and general formula R-(SH)n
(However, R is a hydrocarbon residue having 2 to 36 carbon atoms, n is an integer of 1 to 8) 0.2 to 40 mol% of an organic thiol compound (A ₃ ) is reacted in water in the presence of a radical-generating catalyst. After drying, the total weight of (A ₁ ), (A ₂ ) and (A ₃ ) is 0.5 to 20 parts by weight, and the carbon number is 4.
50 to 100 parts by weight of an alkyl (meth)acrylate (B ₁ ) having ~12 alkyl groups and 0 to 50 parts by weight of other copolymerizable ethylenically unsaturated monomers (B ₂ )
A polymer aqueous dispersion obtained by emulsion polymerization of 100 parts by weight of a monomer mixture consisting of 100 parts by weight and having a Tg value (glass transition point) of the resulting polymer of -60°C to -10°C is used as a base sheet. A pressure-sensitive adhesive sheet obtained by coating and drying.