JP5607337B2 - Water-dispersed acrylic pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet and method for producing the same - Google Patents

Description

  The present invention relates to a water-dispersed acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and methods for producing them. More specifically, even a transfer coating method can be applied to a film such as a synthetic resin which is one of hard-to-adhere substrates, and is excellent in adhesive force and curved surface sticking property without being lifted off. Water with excellent removability that can be applied to an adherend for a long period of time and can be easily removed without causing adhesive residue on the adherend even if it is peeled off after a long period of time since application. The present invention relates to a dispersion-type acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and methods for producing them.

In recent years, from the viewpoint of environmental issues, efforts have been actively made to replace solvent-based adhesives that have been used in the past with solvent-free adhesives, and the development of eco-friendly so-called eco-products is strongly desired. ing.
Of these, many studies have been made on emulsion-type pressure-sensitive adhesives that use water as a dispersion medium because of their high safety and easy cost advantages. In order to obtain polymerization stability and coating suitability, it is necessary to add a lot of low molecular weight non-adhesive additives such as emulsifiers and wetting agents to such an emulsion type adhesive. Since these low molecular weight components remain in the adhesive even after drying and migrate to the interface with the substrate and adherend, emulsion-type adhesives are only adherends compared to solvent-type adhesives. In addition, it is difficult to obtain adhesion to the substrate. In addition, these additives may adversely affect water resistance, film-forming properties, etc., and may reduce the cohesive strength of the pressure-sensitive adhesive. For this reason, when designing a pressure-sensitive adhesive sheet made of an emulsion-type pressure-sensitive adhesive, a high level and precise balance is required.
In addition, the emulsion-type pressure-sensitive adhesive is difficult to be applied particularly to the removability application to the curved adherend because the removability to the adherend tends to deteriorate.

The following prior art is disclosed about such an emulsion type adhesive (for example, refer patent documents 1-4).
In Patent Document 1, a water-dispersed acrylic pressure-sensitive adhesive having a solvent insoluble content of solid content of 20% by weight or less is applied on a substrate to form a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer at the end of the water evaporation step Water-dispersed pressure-sensitive adhesive in which a pressure-sensitive adhesive layer is formed with a water-dispersed acrylic pressure-sensitive adhesive obtained by performing water evaporation so that the solvent-insoluble content in the solvent is 20% by weight or less and then crosslinking the pressure-sensitive adhesive layer A sheet has been proposed.
In Patent Document 2, a monomer mixture containing (meth) acrylic acid alkyl ester (a1) and carboxyl group-containing unsaturated monomer (a2) is emulsion-polymerized in the presence of an anionic reactive emulsifier. A re-peelable water-based pressure-sensitive adhesive composition comprising an emulsion [A] having a gel fraction of less than 70% by weight and a crosslinking agent [B] has been proposed.
Patent Document 3 discloses a water-dispersed acrylic system for re-peeling in which the initial elastic modulus, maximum strength, and elongation at break in a tensile test of the pressure-sensitive adhesive layer are in a specific range, and the gel fraction of the pressure-sensitive adhesive layer is 90% or more. Adhesive sheets have been proposed.
In Patent Document 4, (a) loss tangent at 120 ° C. in the dynamic viscoelastic spectrum of the pressure-sensitive adhesive layer, (b) Fa is the initial adhesive force on the smooth surface of the adherend, and the uneven surface of the adherend. When the initial adhesive force is Fb, the relationship between Fa and Fb (Fb / Fa), and (c) the pressure-sensitive adhesive sheet for re-peeling in which the value of Fa is in a specific range is described. At this time, the pressure-sensitive adhesive layer It is described that the gel fraction is preferably 45 to 80% by weight.
However, nothing is disclosed that is excellent in the balance of anchor effect, tackiness, curved surface sticking property, and removability to various substrates such as a synthetic resin which is one of paper substrates and hard-to-adhere substrates.

JP 2000-119611 A JP 2006-45410 A JP 2006-169596 A JP 2006-265537 A

  The present invention has been made under such circumstances, and has an excellent balance of adhesion and cohesive strength to substrates and adherends, excellent anchoring effects on various substrates, and adhesive strength and curved surface application. Water-dispersed acrylic that has excellent removability and can be easily peeled off without causing adhesive residue on the adherend after a long time has passed since the adhesive sheet produced by the transfer coating method was applied. It aims at providing an adhesive composition, an adhesive sheet, and these manufacturing methods.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has made use of a redox reaction by an oxidizing agent and a reducing agent, to a water-dispersed acrylic polymer that has undergone radical emulsion polymerization under specific polymerization conditions. A water-dispersed acrylic pressure-sensitive adhesive composition containing a cross-linking agent as an essential component. The gel fraction before and after the cross-linking reaction of the pressure-sensitive adhesive composition and the weight-average molecular weight of the solvent-soluble component of the film immediately after drying are specified. It has been found that the above object can be achieved by a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a water-dispersed acrylic pressure-sensitive adhesive composition on the base sheet, and the present invention has been completed.

That is, the present invention provides the following (1) to (6).
(1) (a1) 50 to 99.5 mass% of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, (a2) 0.5 to 10 mass% of carboxyl group-containing unsaturated monomer Acrylic polymer obtained by emulsion polymerization of an unsaturated monomer mixture containing the mixture in the presence of a polymerization initiator comprising a redox polymerization initiator in which a persulfate and / or a peroxide polymerization initiator and a reducing agent are combined. A water-dispersed acrylic pressure-sensitive adhesive composition containing a water-based emulsion (A) and a crosslinking agent (B), wherein the water-dispersed acrylic pressure-sensitive adhesive composition is coated on a release sheet and dried, The weight-average molecular weight of the solvent-soluble component in the dry film immediately after bonding is 150,000 or more, the gel fraction (i) in the dry film is 0% or more and less than 60%, and aging at 40 ° C. for 7 days Gel content in dried film (Ii) is less than 50% or more 99%, gel fraction (i) and water-dispersible acrylic pressure-sensitive adhesive composition characterized by the difference is at least 20% of the gel fraction (ii).
(2) The water-dispersed acrylic pressure-sensitive adhesive composition according to (1), wherein the carboxyl group-containing unsaturated monomer of component (a2) is at least one selected from acrylic acid and methacrylic acid.
(3) The crosslinking agent (B) is at least one selected from an epoxy compound, a carbodiimide compound, and an oxazoline compound, and the crosslinking functional group of the crosslinking agent is based on 1 equivalent of the carboxyl group of the component (a2). The water-dispersed acrylic pressure-sensitive adhesive composition according to (1) or (2), which is contained in an amount of 0.01 to 5 equivalents.
(4) A method for producing a water-dispersed acrylic pressure-sensitive adhesive composition according to any one of the above (1) to (3), which comprises an acrylic emulsion (A) and a crosslinking agent (B), wherein (a1) Unsaturated monomer containing 50 to 99.5% by mass of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of alkyl group and (a2) 0.5 to 10% by mass of carboxyl group-containing unsaturated monomer A reaction field in which the reaction temperature is controlled to 40 to 100 ° C. in the presence of a polymerization initiator comprising a redox polymerization initiator in which a mixture of a persulfate and / or a peroxide polymerization initiator and a reducing agent is combined. A method for producing a water-dispersed acrylic pressure-sensitive adhesive composition, which is obtained by emulsion polymerization to obtain an acrylic emulsion (A).
(5) A pressure-sensitive adhesive sheet comprising the water-dispersed acrylic pressure-sensitive adhesive composition according to any one of (1) to (3) above on a substrate.
(6) A method for producing a pressure-sensitive adhesive sheet obtained by a transfer coating method in which the water-dispersed acrylic pressure-sensitive adhesive composition according to any one of the above (1) to (3) is applied on a release sheet and dried, and then bonded to a substrate.

  According to the present invention, even if it is a transfer coating method, an anchor effect can be obtained even on a hardly-adhesive substrate such as a synthetic resin film, and it is excellent in adhesiveness and curved surface sticking property, and has passed for a long time since sticking. There are provided a water-dispersed acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a method for producing them, which can be easily peeled without causing adhesive residue on the adherend, and has excellent removability.

The present invention is described in detail below.
The water-dispersed acrylic pressure-sensitive adhesive composition of the present invention contains an acrylic emulsion (A).
The acrylic emulsion (A) used in the present invention has (a1) 50 to 99.5 mass% of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, (a2) carboxyl group-containing unsaturated monomer. It is obtained by subjecting an unsaturated monomer mixture containing 0.5 to 10% by mass to emulsion polymerization in the presence of a redox polymerization initiator.

First, the component (a1) in the acrylic emulsion (A) will be described.
Component (a1) used in the present invention is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms.
As component (a1), methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic Isobutyl acid, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate , Isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, isoundecyl (meth) acrylate, dodecyl (meth) acrylate, isododecyl (meth) acrylate ( Examples include tridecyl (meth) acrylate, isotridecyl (meth) acrylate, and tetradecyl (meth) acrylate.
Of these, methyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are more preferable from the viewpoint of balance of performance.
The component (a1) may be used alone or in combination of two or more.

Content of the structural unit derived from the component (a1) in the acrylic copolymer in the acrylic emulsion (A) is 50 to 99.5% by mass and 70 to 99.0% by mass in the monomer structural unit. It is preferably 80 to 98.0% by mass.
By containing 50% by mass or more of component (a1), sufficient adhesive strength and tack can be obtained, and by containing 99.5% by mass or less of component (a2) and other unsaturated monomers as necessary. By containing, sufficient cohesive force can be obtained.

Next, the component (a2) in the acrylic emulsion (A) will be described.
Component (a2) is a carboxyl group-containing unsaturated monomer, and the carboxyl group acts as a crosslinking base point with the crosslinking agent (B).
The component (a2) is not particularly limited as long as it is an unsaturated monomer containing a carboxyl group that is a reactive functional group that acts as a crosslinking base point in the reaction with the crosslinking agent (B) described later. Acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid and the like.
Among these, acrylic acid and methacrylic acid are preferable, and methacrylic acid is more preferable.
The component (a2) may be used alone or in combination of two or more.

Content of the structural unit derived from the component (a2) in the acrylic copolymer in the acrylic emulsion (A) is 0.5 to 10% by mass and 0.8 to 8% by mass in the monomer structural unit. It is preferably 1 to 5% by mass.
By containing the component (a2) in an amount of 0.5 to 10% by mass, the stability in an aqueous dispersion coating liquid state such as polymerization stability, dispersion stability, and mechanical stability, and the pressure-sensitive adhesive composition in the pressure-sensitive adhesive sheet described later Both physical properties of the dried film can be achieved. If it is 0.5% by mass or more, the stability in the coating liquid state and the cohesive force of the dry film are improved, and if it is 10% by mass or less, the water resistance of the dry film and a good anchoring effect on the adherend are obtained. can get. By setting the content of the component (a2) in the above range, the amount of the crosslinking base point formed by the reaction with the crosslinking agent as the component (B) is appropriately maintained, and the gel fraction is in the appropriate range. Can be adjusted.

In the acrylic emulsion (A), other unsaturated monomers (a3) can be used as necessary as monomer components other than the components (a1) and (a2).
Examples of the component (a3) include γ- (meth) acryloxypropyltrimethoxysilane, (meth) acryloxybutyltrimethoxysilane, alkoxysilyl group-containing unsaturated monomers such as vinyltrimethoxysilane, ethylene glycol di ( (Meth) acrylate, propylene glycol di (meth) acrylate, 1,6 hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Hydroxyl group-containing unsaturated monomers such as (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, etc. Monomers, acetoacetoxy group-containing unsaturated monomers such as acetoacetoxymethyl acrylate, acetoacetoxymethyl methacrylate, amide group-containing unsaturated monomers such as acrylamide, methacrylamide, diacetone acrylamide, (meth) acrylic Glycidyl group-containing unsaturated monomers such as glycidyl acid and allyl glycidyl ether, alkoxy group-containing unsaturated monomers such as 2-methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and methoxytriethylene glycol (meth) acrylate , Fluorine-containing unsaturation such as 2,2,2-trifluoroethyl (meth) acrylate, 2,2,3,3-tetrafluoropropyl (meth) acrylate, β- (perfluorooctyl) ethyl (meth) acrylate Monomer, N-vinylpyrrolidone Nitrogen-containing unsaturated monomers such as N-vinyl-ε-caprolactam and cyclohexylmaleimide, vinyl ethers such as methyl vinyl ether, butyl vinyl ether and hexyl vinyl ether, vinyl esters such as vinyl acetate and vinyl propionate, ethylene, propylene and isobutylene Olefins such as vinyl chloride and chloroprene, styrenes such as styrene and tert-butylstyrene, nitrile unsaturated monomers such as (meth) acrylonitrile and chloroacrylonitrile, dimethyl (meth) acrylate Amino group-containing unsaturated monomers such as aminoethyl and tert-butylaminoethyl (meth) acrylate, and methylol group-containing unsaturated monomers such as methylolacrylamide and butoxy N-methylolacrylamide , Sulfonic acid group-containing unsaturated monomers such as sodium vinyl sulfonate, sodium styrene sulfonate, sodium 2-acrylamido-2-methylpropane sulfonate, and salts thereof (for example, sodium salt, potassium salt, amine salt, etc.) , Acid phosphooxyethyl (meth) acrylate, acid phosphooxypropyl (meth) acrylate, acid phosphooxypolyethylene glycol (meth) acrylate and other monomers having a phosphate group and salts thereof (for example, sodium salt, potassium salt, amine) Salt, etc.).

The content of the structural unit derived from the component (a3) in the acrylic copolymer in the acrylic emulsion (A) is preferably 0 to 45.5% by mass, and 0 to 30% by mass in the monomer structural unit. It is more preferable that it is 0-20 mass%.
The composition is appropriately adjusted with these unsaturated monomers (a3) so that the glass transition point (Tg) of the acrylic copolymer in the acrylic emulsion (A) is −80 ° C. to −20 ° C. Of these, -75 to -25 ° C is more preferred, and -70 to -30 ° C is more preferred.

Next, the manufacturing method of an acrylic emulsion (A) is demonstrated.
The acrylic emulsion (A) is an emulsion polymerization of an unsaturated monomer mixture containing the component (a1), the component (a2) and other unsaturated monomers (a3) used as necessary using an emulsifier. Is obtained.
As the emulsifier, for example, an anionic or nonionic reactive emulsifier having a radical polymerizable functional group such as a vinyl group, a propenyl group, an isopropenyl group, a vinyl ether group, an allyl ether group, or a non-reactive emulsifier is used.

  Examples of the anionic reactive emulsifier include “Adekalia Soap SE-10N”, “Adekalia Soap SE-20N”, “Adekalia Soap SE-1025A”, “Adekalia Soap PP-70”, “Adekalia Soap PP-”. "710", "Adekaria soap SR-10", "Adekaria soap SR-20", "Adekaria soap SR-1025" (manufactured by ADEKA Corporation), "Eleminol JS-2", "Eleminol RS-30" [Sanyo Kasei Kogyo Co., Ltd.], “Latemul S-180A”, “Latemul S-180”, “Latemul PD-104” (Kao Corporation), “Aqualon BC-05”, “Aquaron” BC-10, Aqualon BC-20, Aqualon HS-05, Aqualon HS-10, Aqualon HS "20", "New Frontier S-510", "New Frontier A-229E", "Aquaron KH-05", "Aquaron KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Phosfinol TX" Commercial products such as “Toho Chemical Co., Ltd.”, “Antox MS-60”, “Antox SAD”, “Antox MS-2N” [manufactured by Nippon Emulsifier Co., Ltd.] are listed, but they have reactivity. However, the present invention is not particularly limited thereto.

  Nonionic reactive emulsifiers include “ADEKA rear soap NE-10”, “ADEKA rear soap NE-20”, “ADEKA rear soap NE-30”, “ADEKA rear soap NE-40”, and “ADEKA rear soap ER-”. 10 ”,“ Adekaria soap ER-20 ”,“ Adekaria soap ER-30 ”,“ Adekaria soap ER-40 ”(manufactured by ADEKA Corporation),“ Latemul PD-420 ”,“ Latemuru PD-430 ” "Latemul PD-450" [above, manufactured by Kao Corporation] "AQUALON RN-10", "AQUALON RN-20", "AQUALON RN-30", "AQUALON RN-50" [above, Daiichi Kogyo Seiyaku Co., Ltd.], “Antox LMA-10” (manufactured by Nippon Emulsifier Co., Ltd.), and the like. But it is not limited to.

  In consideration of emulsion polymerization stability and mechanical stability of the emulsion, a non-reactive emulsifier may be used, or it may be used in combination with the aforementioned reactive emulsifier. Such a non-reactive emulsifier is not particularly limited, and a known emulsifier usually used for emulsion polymerization is used. For example, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium dialkylsulfosuccinate, sodium alkyldiphenyl ether disulfonate, sodium polyoxyethylene lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene aryl ether sulfate, polyoxyethylene alkyl Anionic emulsifiers such as sodium phenyl ether sulfate, sodium polyoxyethylene alkyl sulfosuccinate, sodium polyoxyethylene polycyclic phenyl ether sulfonate, sodium polyoxyalkylene alkyl ether phosphate, and ammonium salts and potassium salts of these anionic emulsifiers, for example, , Polyoxyethylene alkyl ether, polyoxyethylene al Such as ruphenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyethylene fatty acid ester, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan acid ester, glycerol higher fatty acid ester, polyoxyethylene polyoxypropylene block polymer, etc. Nonionic emulsifiers and the like can be mentioned.

  The amount of these emulsifiers used is preferably 0.5 to 10.0 parts by mass, more preferably 0.8 to 8.0 parts by mass, and 1.0 to 6.0 parts per 100 parts by mass of the unsaturated monomer mixture. Part by mass is more preferable. By making the used amount of the emulsifier 0.5 parts by mass or more, emulsion polymerization stability, storage stability of the resulting emulsion, and mechanical stability can be ensured, and by making it 10.0 parts by mass or less, hydrophilicity is obtained. It is possible to prevent a decrease in water resistance, a decrease in the cohesive strength of the pressure-sensitive adhesive, and a contamination of the adherend due to the excessive increase in the thickness.

  As the polymerization conditions for the acrylic emulsion (A), the conditions applied in normal emulsion polymerization can be applied as they are. In general, after replacing the inside of the reactor with an inert gas, polymerization is carried out for about 1 to 8 hours after the start of temperature increase with stirring under heating and reflux.

In the present invention, a polymerization initiator composed of a redox polymerization initiator is used for emulsion polymerization of the acrylic emulsion (A). Ordinary polymerization initiator used for radical polymerization, specifically, a redox polymerization initiator in which a persulfate and / or peroxide initiator is used as an oxidizing agent, and a reducing agent exhibiting reducing properties coexists therewith. Is used.
In the redox polymerization initiator, radicals can be generated not only by a thermal decomposition reaction of the polymerization initiator but also by an oxidation-reduction reaction. Therefore, since the amount of the initiator used can be reduced as compared with the case where no reducing agent is allowed to coexist, it is advantageous in terms of cost, and the water resistance can be improved when a water-soluble initiator is used.
In redox polymerization, the rate of formation of polymerization initiating radicals is increased, so that excessive increase in molecular weight can be suppressed. By suppressing excessive molecular weight increase, it becomes a more flexible molecule, and an adhesive having a high anchoring effect on the substrate can be obtained. Here, the anchor effect means that the pressure-sensitive adhesive penetrates into the irregularities or voids on the surface of the adherend and then hardens and functions like a nail or a wedge, and is also called an anchoring effect or a fastener effect. Furthermore, since radicals can be generated easily even at low temperatures by oxidation-reduction reactions, it is possible to lower the polymerization temperature compared to general emulsion polymerization, and suppress excessive grafting and side reactions of the produced polymer. Can do.
From these facts, by using the redox polymerization initiator in the present invention, the pressure-sensitive adhesive is flexible, fluidity is high, wettability to the base material, good adhesion, and transfer coating method. A re-peelable pressure-sensitive adhesive that is difficult to peel off from the substrate is obtained.

Examples of the oxidizing agent for the redox initiator include an aqueous oxidizing substance and a non-aqueous oxidizing substance.
Examples of aqueous oxidizing substances include peroxides such as hydrogen peroxide, persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, tert-butyl hydroperoxide, cumene hydroperoxide, and diisopropylbenzene hydroperoxide. In addition to hydroperoxides such as oxide and p-menthane hydroperoxide, examples thereof include water-soluble organic peroxides such as succinic acid peroxide and 2,2′-azobis [2-N-benzylamidino] propane hydrochloride. .

  Examples of non-aqueous oxidizing substances include diacyl peroxides such as isobutyryl peroxide, bis (3,5,5-trimethylhexanoyl) peroxide, lauroyl peroxide, benzoyl peroxide, decanoyl peroxide, and di- Dialkyl peroxides such as t-butyl peroxide, tert-butyl-α-cumyl peroxide, di-α-cumyl peroxide, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane Peroxyketals such as tert-butyl peroxyacetate, tert-butyl peroxylaurate, alkyl peresters such as tertbutyl peroxybenzoate, and pers such as bis- (2-ethylhexyl) peroxydicarbonate An oxycarbonate etc. are mentioned.

Examples of the reducing agent of the redox initiator include an aqueous reducing substance and a non-aqueous reducing substance.
Examples of aqueous reducing substances include iron (II) salts (such as iron (II) chloride and iron (II) sulfate), copper (I) salts (such as copper (I) chloride), and chromium (III) salts (chlorinated). Reducing metal salts such as chromium (III)), sodium thiosulfate, sodium sulfite, sodium hydrogen sulfite, sodium hyposulfite, sodium dithionite, reductive sulfur compounds such as Rongalite, etc. 6 lower alcohols, lower amines having 1 to 6 carbon atoms such as methylamine and ethylamine, (poly) alkylamines such as trimethylamine and triethylamine, water-soluble organic acids such as ascorbic acid, erythorbic acid, tartaric acid and citric acid, and The salt, sugars, such as glucose, etc. are mentioned.
Examples of non-aqueous reducing substances include organometallic compounds such as triethylaluminum and triethylzinc.

  Each of these oxidizing agents and reducing agents may be a single combination, or one or both may be a combination of two or more. Preferably, a combination of an aqueous oxidizing substance and an aqueous reducing substance is used. More specifically, a combination of hydroperoxide and ascorbic acid or a salt thereof, hydroperoxide and iron (II) chloride, a combination of hydroperoxide, hydrogen peroxide and ascorbic acid or a salt thereof, hydroperoxide and Examples thereof include a combination of ascorbic acid or a salt thereof and iron (II) chloride, a combination of persulfate and sodium hydrogen sulfite, a combination of hydrogen peroxide and iron (II) chloride, and the like.

Although the usage-amount of a redox type | system | group polymerization initiator is selected suitably, it is preferable that it is 0.02-1.0 mass part with respect to 100 mass parts of unsaturated monomer mixtures, 0.08-0.8 It is more preferable that it is a mass part, and it is still more preferable that it is 0.1-0.5 mass part. When 0.02 part by mass or more, a substantial effect as a polymerization initiator is obtained, and when it is 1.0 part by mass or less, the molecular weight of the produced polymer is moderately improved, and the adhesive composition has adhesiveness. Can be improved.
Moreover, it is preferable that the compounding ratio of an oxidizing agent and a reducing agent in a redox-type initiator is 0.01-100 mass parts with respect to 1 mass part of oxidizing agents, and 0.02-50 mass parts. More preferably, it is 0.1-10 mass parts.

  In the present invention, the reaction temperature of the emulsion polymerization of the acrylic emulsion (A) is preferably controlled to 40 to 100 ° C, more preferably 50 to 90 ° C, and particularly preferably 60 to 80 ° C. The reaction temperature described here is the reaction temperature in the flask. By controlling the reaction temperature in this temperature range, the resulting polymer can suppress excessive polymer weight, grafting and side reactions, and is more flexible and has a sufficient anchor effect on the substrate. And a releasable adhesive sheet is obtained.

In these emulsion polymerizations, a chain transfer agent can be used in order to adjust the degree of polymerization and enhance the anchor effect on the base material or to increase the flexibility as an adhesive.
Examples of such chain transfer agents include thiol group-containing compounds such as lauryl mercaptan, 2-mercaptoethanol, dodecyl mercaptan, mercaptosuccinic acid, n-butyl mercaptopropionate, octyl mercaptopropionate, methoxybutyl mercaptopropionate, and methanol. , Terpene compounds such as α-pinene, β-pinene, limonene, terpinolene, and the like. The chain transfer agent may be used alone or in combination of two or more.
It is preferable that the usage-amount of a chain transfer agent is 0-3 mass parts with respect to a total of 100 mass parts of an unsaturated monomer mixture. These chain transfer agents are appropriately used alone or in combination.

  Furthermore, a pH buffering agent may be used in combination as necessary in order to adjust the pH during the emulsion polymerization. The pH buffering agent is not particularly limited as long as it has a pH buffering action. For example, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, Examples thereof include sodium acetate, ammonium acetate, sodium formate, and ammonium formate. The blending amount of the pH buffering agent is not particularly limited, and can be added before or during the polymerization.

The average particle diameter of the particles in the acrylic emulsion (A) is about 50 to 1000 nm, preferably 80 to 800 nm, and more preferably 100 to 500 nm. When the average particle size is within the above range, emulsion polymerization stability, storage stability of the resulting emulsion, mechanical stability, and physical property balance of the adhesive composition film after drying, that is, anchor effect on the substrate, water resistance A pressure-sensitive adhesive having a good balance of properties, cohesive strength, transparency, and mechanical strength can be obtained.
When the average particle diameter is 50 nm or more, stable emulsion particles can be obtained, and an increase in the amount of emulsifier used can be prevented. When the average particle size is 1000 nm or less, adhesion to the substrate, transparency of the resulting pressure-sensitive adhesive layer, and water resistance are ensured.
The average particle size of the emulsion particles can be controlled by the type, concentration, addition timing, and the like of the emulsifier added during the polymerization. Here, the average particle diameter of the emulsion particles is based on a volume-based median diameter value obtained by measurement with a laser diffraction / scattering particle size distribution measuring apparatus.

  The crosslinking agent (B) to be blended in order to adjust various physical properties of the water-dispersed acrylic pressure-sensitive adhesive composition is particularly suitable as long as it is cross-linked by a crosslinking base point in the copolymer in the acrylic emulsion (A). Although not limited, epoxy compounds, carbodiimide compounds, oxazoline compounds, hydrazides from the viewpoint of excellent adhesion, adhesion, cohesion, dispersibility in water, reactivity, pot life, and availability. Preferably, at least one selected from a base compound, an isocyanate compound, an aziridine compound, an alkoxysilane compound, an amine compound, and a metal chelate compound is preferably used. Among these, epoxy compounds, carbodiimide compounds, oxazoline compounds, hydrazide compounds, and isocyanate compounds are preferable, and epoxy compounds, carbodiimide compounds, and oxazoline compounds are particularly preferable.

  The epoxy compound may be any compound having two or more epoxy groups or glycidyl groups in the molecule, such as “Denacol” series (for example, sorbitol polyglycidyl ether (“Denacol EX-611”) manufactured by Nagase ChemteX Corporation. ”,“ Denacol EX-612 ”,“ Denacol EX-614 ”,“ Denacol EX-614B ”,“ Denacol EX-622 ”), polyglycerol polyglycidyl ether (“ Denacol EX-512 ”,“ Denacol EX-521 ”) ), Pentaerythritol polyglycidyl ether (“Denacol EX-411”), diglycerol polyglycidyl ether (“Denacol EX-421”), glycerol polyglycidyl ether (“Denacol EX-313”, “Denacol EX-314”) ), Trimethylolpropane polyglycidyl ether ("Denacol EX-321"), resorcinol diglycidyl ether ("Denacol EX-201"), neopentyl glycol diglycidyl ether ("Denacol EX-211"), 1,6-hexane Diol diglycidyl ether (“Denacol EX-212”), ethylene glycol diglycidyl ether (“Denacol EX-810”, “Denacol EX-811”), diethylene glycol diglycidyl ether (“Denacol EX-850”, “Denacol EX-”) 851 "), polyethylene glycol diglycidyl ether (" Denacol EX-821 "," Denacol EX-830 "," Denacol EX-832 "," Denacol EX-841 "," Denacol E " -861 "), propylene glycol diglycidyl ether (" Denacol EX-911 "), polypropylene glycol diglycidyl ether (" Denacol EX-941 "," Denacol EX-920 "," Denacol EX-931 "), Sakamoto Pharmaceutical Co., Ltd. Polyepoxy product "SR" series, diglycidylaniline, N, N, N ', N'-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N'-diglycidylaminomethyl) Examples include cyclohexane, bisphenol A / epichlorohydrin type epoxy resin, etc. Among them, the aqueous type is preferable.

  The carbodiimide-based compound may be any compound containing at least two carbodiimide groups in the molecule. For example, “Carbodilite SV-02”, “Carbodilite V-02”, “Carbodilite V-02” manufactured by Nisshinbo Chemical Co., Ltd. L2 ”,“ Carbodilite V-04 ”,“ Carbodilite V-06 ”,“ Carbodilite E-01 ”,“ Carbodilite E-02 ”,“ Carbodilite E-04 ”and the like.

  The oxazoline-based compound may be any compound containing at least two oxazoline groups in the molecule. For example, “Epocross WS-300”, “Epocross WS-500”, “Epocross WS-700” manufactured by Nippon Shokubai Co., Ltd. , "Epocross K-2010E", "Epocross K-2020E", "Epocross K-2030E" and the like.

  The hydrazide compound may be any compound having at least two or more hydrazide groups in the molecule, such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, Examples thereof include maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide and the like.

  The isocyanate compound may be any compound containing at least two isocyanate groups in the molecule. For example, toluylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate. , 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, etc., "Sumijour N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) Bullet polyisocyanate compounds such as “Desmodur IL”, “Desmodur HL” (Bayer AG). ), "Coronate EH" (manufactured by Nippon Polyurethane Industry Co., Ltd.), polyisocyanate compounds having an isocyanurate ring, "Sumijoule L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.), "Coronate HL" (Nihon Polyurethane Industry Co., Ltd.) Manufactured by Co., Ltd.), adduct-type polyisocyanate compounds such as “Takenate WD-725”, “Takenate WD-720”, “Takenate WD-730”, and “Takenate WB-700” (manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) Examples thereof include self-emulsifying water-dispersed polyisocyanate compounds such as “Aquanate 100”, “Aquanate 110”, “Aquanate 200”, and “Aquanate 210” (manufactured by Nippon Polyurethane Industry Co., Ltd.). Among these, the aqueous type is preferable. Moreover, you may use block isocyanate.

  Any aziridine compound may be used as long as it contains at least two aziridinyl groups in the molecule. Examples thereof include “Chemite PZ-33” and “Chemite DZ-22E” manufactured by Nippon Shokubai Co., Ltd.

  Any alkoxysilane compound may be used as long as it contains at least two alkoxysilyl groups in the molecule, such as γ- (meth) acryloxypropyltrimethoxysilane, (meth) acryloxybutyltrimethoxysilane, vinyltrimethylsilane. Methoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, phenylmethyldimethoxy Silane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) a Roh trimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, and the like.

  As the amine compound, any compound containing at least two amino groups in the molecule may be used. For example, “Epomin SP-003”, “Epomin SP-006”, “Epomin SP-012” manufactured by Nippon Shokubai Co., Ltd. , Polyethyleneimine such as “Epomin SP-018”, “Epomin SP-200”, “Epomin P-1000”, aminoethyl such as “Polyment SK-1000”, “Polyment NK-100PM”, “Polyment NK-200PM” And acrylic polymer.

  Examples of the metal chelate compound include titanium, such as “Orga TCs TC-400”, “Orga TCs TC-300”, “Orga TCs TC-310” and “Orga TCs TC-315” manufactured by Matsumoto Co., Ltd. Chelate type, zirconium acylate type aluminum chelate type such as “Orgachix ZB-126”, zinc chelate type and the like.

The crosslinking agent (B) has 0.01 to 5 equivalents of the crosslinking functional group of the crosslinking agent with respect to 1 equivalent of the carboxyl group of the component (a2) that acts as a crosslinking base point in the acrylic emulsion (A). It is preferable to mix | blend so that it may become the range of this, the range of 0.05-4 equivalent is more preferable, and the range of 0.1-3 equivalent is further more preferable.
By blending the cross-linking agent (B) so as to fall within the above range, it is preferable from the viewpoint of productivity and handling properties such as storage stability of the coating liquid, coating property, etc. A re-peelable pressure-sensitive adhesive sheet that is excellent and has low adherence contamination even with high adhesion to the adherend is obtained. These crosslinking agents are suitably used alone or in combination.

Next, the gel fraction and the weight average molecular weight of the solvent-soluble component in the water-dispersed acrylic pressure-sensitive adhesive composition in which the crosslinking agent (B) is blended with the acrylic emulsion (A) will be described.
The gel fraction is the ratio of tetrahydrofuran (THF) insoluble matter in the dry film of the water-dispersed acrylic pressure-sensitive adhesive composition. The weight average molecular weight of the solvent-soluble component is a value obtained by measuring the molecular weight of the tetrahydrofuran (THF) -soluble component at the time of measuring the gel fraction by gel permeation chromatography (GPC). The weight average molecular weight of the gel fraction and the solvent-soluble component was determined by applying a water-dispersed acrylic pressure-sensitive adhesive composition in which a crosslinking agent (B) was blended with an acrylic emulsion (A) on a release sheet, drying it, and A base material-less pressure-sensitive adhesive sheet having a pressure-sensitive adhesive surface protected by a single release sheet was prepared, and a pressure-sensitive adhesive layer made of this water-dispersed acrylic pressure-sensitive adhesive composition was used for the test. The pressure-sensitive adhesive layer in this base material-less pressure-sensitive adhesive sheet represents a dry film immediately after the water-dispersed acrylic pressure-sensitive adhesive composition is applied on a release sheet, dried, and bonded to the base material. Is the same.

Samples used for measuring the weight average molecular weight of the gel fraction and the solvent-soluble content were collected under the following conditions.
(I) Immediately after creating the substrate-less adhesive sheet. Hereinafter, the obtained sample is referred to as sample (i).
(Ii) After creating a substrate-less pressure-sensitive adhesive sheet, after aging in a 40 ° C. environment for 7 days. Hereinafter, the obtained sample is referred to as sample (ii).
The water-dispersed acrylic pressure-sensitive adhesive composition was applied onto a release sheet, dried, and the gel fraction (i) and the weight-average molecular weight of the solvent-soluble component in the dried film immediately after the substrates were bonded together were the sample (i ) To measure.
On the other hand, the gel fraction (ii) in the dried film after aging at 40 ° C. for 7 days immediately after applying the water-dispersed acrylic pressure-sensitive adhesive composition on the release sheet, drying, and bonding to the base material is as follows: It can be determined by measuring using (ii).

  The gel fraction (i) ranges from 0% to less than 60%, preferably from 3% to less than 55%, more preferably from 5% to less than 50%. On the other hand, the gel fraction (ii) is preferably in the range of 50% or more and less than 99%, more preferably 55% or more and less than 95%, and further preferably 60% or more and less than 90%.

  When the gel fraction (i) is within the above range, when the water-dispersed acrylic pressure-sensitive adhesive composition is applied onto the release sheet, dried and bonded to the base material in the process of manufacturing the pressure-sensitive adhesive sheet, the degree of crosslinking of the pressure-sensitive adhesive Because it is low and flexible, it has a good anchoring effect not only on paper substrates such as high-quality paper but also on difficult-to-adhere substrates such as synthetic resin films, even with transfer coating methods. can get. Furthermore, when the gel fraction (i) is in the above range, the emulsion particles are entangled by mutual diffusion, and a continuous film closer to the solvent-based pressure-sensitive adhesive can be formed. Mechanical film strength can be improved. On the other hand, when the gel fraction (i) is 60% or more, the crosslinking effect of the pressure-sensitive adhesive in the bonding step is too high, so that the anchor effect for the substrate cannot be sufficiently obtained. In addition, the emulsion particles are difficult to diffuse each other and a continuous film is difficult to be formed.

When the gel fraction (ii) is in the above range, the pressure-sensitive adhesive is sufficiently wetted and diffused by the anchor effect and then cross-linked, so that the pressure-sensitive adhesive adheres firmly to the substrate and is covered. A pressure-sensitive adhesive sheet that is difficult to transfer to the body is obtained. Thereby, even if the adhesive force between the adhesive sheet and the adherend is high, an adhesive sheet that can be peeled again without causing interlaminar fracture between the base material and the adhesive is obtained. Furthermore, when the gel fraction (ii) is in the above range, a practical cohesive force can be imparted to the pressure-sensitive adhesive by cross-linking, and the adherend contamination can be reduced when peeling from the adherend. it can. Furthermore, a pressure-sensitive adhesive sheet excellent in processing suitability can be obtained with little deterioration of physical properties over time or in the passage of time and with no sticking-out of the pressure-sensitive adhesive at the end of the cutting roll. On the other hand, when the gel fraction (ii) is less than 50%, since the crosslinking reaction is not sufficient, the adhesive force of the pressure-sensitive adhesive and the cohesive strength of the pressure-sensitive adhesive cannot be sufficiently obtained, and the pressure-sensitive adhesive sheet is peeled off again. At this time, the pressure-sensitive adhesive may be transferred to the adherend, and the pressure-sensitive adhesive may be coherently broken.
The gel fraction (ii) increases from the gel fraction (i) as the crosslinking reaction proceeds, but the difference between the gel fraction (i) and the gel fraction (ii) [gel fraction (ii)-gel fraction (I)] is 20% or more, and more preferably 30% or more.

In order to lower the gel fraction (i) and the gel fraction (ii), the crosslinkable functional group in the acrylic emulsion (A) and the crosslinking point by the crosslinking agent (B) and the polyfunctional unsaturated monomer Reduce the blending ratio of the body, lower the polymerization temperature, select methacrylic acid as the carboxyl group-containing unsaturated monomer (a2) component in the acrylic emulsion (A), blend of chain transfer agent and polymerization initiator It can be adjusted by increasing the amount, or changing the type and timing of addition.
On the other hand, in order to increase the gel fraction (i) and the gel fraction (ii), the crosslinking point and polyfunctional unsaturation by the crosslinkable functional group in the acrylic emulsion (A) and the crosslinker (B). Select the acrylic acid as the carboxyl group-containing unsaturated monomer (a2) component in the acrylic emulsion (A) to increase the monomer mixing ratio or increase the polymerization temperature, chain transfer agent or polymerization initiation It can be adjusted by reducing the blending amount of the agent or changing the type and timing of addition.

The dried film of the water-dispersed acrylic pressure-sensitive adhesive composition immediately after adding the crosslinking agent (B) to the acrylic emulsion (A), that is, the weight average molecular weight of the solvent-soluble component in the sample (i) is 150,000 or more. Yes, it is preferably 150,000 to 10,000,000, more preferably 150,000 to 6,000,000.
If the solvent-soluble component has a weight average molecular weight of 150,000 or more, a flexible and high-strength adhesive is obtained, and the adhesive composition of the present invention is soluble in a solvent even if it has a relatively high molecular weight. It represents having a polymer. That is, although it has a high molecular weight, it has a high molecular weight, but it has a high molecular weight, so that a polymer having both contradictory performances such as high mechanical strength of the film can be obtained. Although a detailed reason is not certain, it is assumed that the adhesive sheet of the present invention has a good curved surface sticking property for the above reason. In addition, the fact that the weight average molecular weight is high means that there are relatively few low molecular weight components, so that a pressure-sensitive adhesive sheet with high cohesive force of the pressure-sensitive adhesive and less adherend contamination can be obtained. Further, in order to increase the weight average molecular weight of the solvent-soluble component, it can be adjusted by appropriately selecting the type and blending amount of the chain transfer agent and polymerization initiator, the addition timing, etc., which lower the polymerization temperature.
On the other hand, when the weight average molecular weight of the solvent-soluble component is 10 million or less, the molecular weight does not become too high, and a sufficient anchoring effect for the substrate can be obtained while maintaining flexibility.
Thus, by controlling the range of the gel fraction (i) and the gel fraction (ii) and the weight average molecular weight of the solvent-soluble component, a pressure-sensitive adhesive sheet having an excellent anchor effect on the substrate and the adherend can be obtained. Furthermore, it is possible to design a strong-viscosity releasable pressure-sensitive adhesive sheet excellent in both adhesive strength and removability.

  In the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention, if necessary, in addition to the acrylic emulsion (A) and the crosslinking agent (B), a tackifier, a plasticizer, a thickener, and a wetting agent. (Succinic acid type, acetylene diol type, silicone type, fluorine type, acrylic type), antifoaming agent (mineral oil type, silicone type, polyether type, acrylic type, fluorine type, surfactant type, emulsion type), medium Additives, surfactants (anionic and nonionic), film-forming aids, preservatives, rust inhibitors, freeze-thaw stabilizers, pigments, colorants, fillers (zinc white, titanium white, calcium carbonate, clay, etc.) ), Metal powders, antioxidants, light stabilizers, ultraviolet absorbers and the like can be added as appropriate. The additive is often added to the water-dispersed pressure-sensitive adhesive composition after polymerization, but can also be added before emulsion polymerization or during emulsion polymerization.

Examples of the tackifier include synthetic resin systems such as rosin-based, terpene-based natural resin-based, and petroleum resin-based. Specifically, “Harry Star SK-508”, “Harry Star SK-508H”, “Harry Star SK-532D”, “Harry Star SK-816E”, “Harry Star SK-” manufactured by Harima Chemical Co., Ltd. are commercially available. 822E "," Harry Star SK-218NS "," Harry Star SK-70D "," Harry Star SK-501 "," Harry Star SK-501NS "," Harry Star SK-385NS "," Harry Star SK-370N ", For example, “Super Ester E-720”, “Super Ester E-730-55”, “Super Ester E-650”, “Super Ester E-865”, “Tamanol E-100”, “ “Tamanol E-200”, “Emulsion AM-1002”, “Superester NS-10” “H”, “Superester NS-125A”, “Superester NS-100A”, “Superester NS-120B”, “Superester E-625-NT”, “Superester E-865-NT”, “Tamanol E” -200-NT ", for example," YS Resin TO125 "," YS Resin TO115 "," YS Resin TO105 "," YS Resin TO85 "," YS Resin TR105 "," YS Polystar U115 "," YS "manufactured by Yashara Chemical Co., Ltd. "Polystar 2130", "YS Polyster 2115", "YS Polyster 2100", "YS Polyster T145", "YS Polystar T130", "YS Polyster T115", "YS Polystar T100", "YS Polyster T80", "YS Polystar T50""," YS Lister T30 "," YS Polystar S145 "," YS Polystar TH130 "," Mighty Ace G150 "," Mighty Ace G125 "," Nanoretto R-1050 ", and" Nanoretto G-1250 "and the like.
These tackifiers can be added to the unsaturated monomer mixture at the time of polymerization, or the tackifier itself can be emulsified by a known method and added to the acrylic emulsion (A). About what is already marketed as an aqueous dispersion, it can add to an aqueous dispersion-type acrylic adhesive composition as it is.

  The compounding quantity of a tackifier can add 0-40 mass parts with respect to 100 mass parts of acrylic emulsion (A), It is more preferable that it is 0-30 mass parts, It is 0-20 mass parts. More preferably it is. When a tackifier is blended, it is excellent in tack, adhesive strength, and substrate adhesion, and can improve cohesion. If added in an amount of 40 parts by mass or more, the physical property balance of the pressure-sensitive adhesive may be lost. These tackifiers may be used in combination of two or more as required.

  Examples of the plasticizer include liquid polybutene, mineral oil, lanolin, wax, liquid polyisoprene, liquid polyacrylate, dioctyl phthalate, triethanolamine, alkylamine, amine alkylene oxide adduct, glycerin, diglycerin, and silicone oil. Can be mentioned.

  The compounding amount of the plasticizer is preferably 0 to 20 parts by mass, more preferably 0 to 15 parts by mass, and 0 to 10 parts by mass with respect to 100 parts by mass of the acrylic emulsion (A). Is more preferable. When a plasticizer is blended, effects such as improvement of tack, adhesive strength, substrate adhesion, and film strength may be obtained. If the compounding quantity of a plasticizer is 20 mass parts or less, the physical property balance of an adhesive will be favorable. These plasticizers may be used in combination of two or more as required.

  Examples of thickeners include, for example, hydroxypropylcellulose, hydroxypropylmethylcellulose acetate succinate, cellulose such as hydroxypropylmethylcellulose, protein such as casein, natural products such as starch and polysaccharides, polyacrylic acid, Polyether-based, water-soluble polymer thickeners such as polyvinylpyrrolidone and polyvinyl alcohol, alkali-soluble or alkali-swelling emulsion thickeners, associative thickeners such as hydrophobic group-modified polyoxyethylene urethane Can be mentioned. Of these, alkali-soluble or alkali-swelling emulsion thickeners and associative thickeners such as hydrophobic group-modified polyoxyethylene urethane are preferred.

  Examples of commercially available alkali-soluble emulsion thickeners include “Primal ASE-60”, “Primal ASE-75”, “Primal ASE-95”, and “Primal ASE-108” manufactured by Rohm & Haas. "Primal RM-5", for example, "SN thickener A-850" manufactured by San Nopco Corporation.

  Examples of commercially available products of hydrophobic group-modified polyoxyethylene urethane thickener include “ADEKA NOL UH-140S”, “ADEKA NOL UH-420”, “ADEKA NOL UH-438”, and “ADEKA NOL UH-472” manufactured by ADEKA Corporation. "Adecanol UH-450", "Adecanol UH-540", "Adecanol UH-550", "Adecanol UH-541", "Adecanol UH-526", "Adecanol UH-530", for example, "RHEOLATE244 from Leox" ”,“ RHEOLATE255 ”,“ RHEOLATE278 ”, for example“ SN thickener A-803 ”,“ SN thickener A-804 ”,“ SN thickener A-807 ”,“ SN thickener A-812 ”,“ SN ”manufactured by San Nopco Corporation Thickener A- 14 ", for example, Dai-ichi Kogyo Seiyaku Co., Ltd. of" DK thickener SCT-200 ", and the like can be given" DK thickener SCT-270 ".

  The blending amount of the thickener is appropriately adjusted according to the desired viscosity, but is preferably 0 to 10 parts by mass with respect to 100 parts by mass of the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention. It is more preferable to set it as -8 mass parts, and it is still more preferable to set it as 0-5 mass parts.

The water-dispersed acrylic pressure-sensitive adhesive composition of the present invention has a solid content (nonvolatile content) of usually about 30 to 70% by mass, preferably 35 to 65% by mass, and 40 to 60% by mass. The viscosity is usually about 30 to 30,000 mPa · s (BM type viscometer, 25 ° C.), preferably 50 to 25,000 mPa · s, more preferably 80 to 20,000 mPa · s.
Furthermore, pH is adjusted to the range of 6-9 normally by adding neutralizing agents (Ammonia water, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution etc.) as needed.
It is preferable that the solid content, viscosity and pH are within the above ranges from the viewpoints of cost, polymerization stability, storage stability of the coating liquid, productivity such as drying property and coating property, and handling property.

  In the method for producing a water-dispersed acrylic pressure-sensitive adhesive composition of the present invention, an unsaturated monomer mixture containing the component (a1) and the component (a2) is converted into persulfate and / or peroxide-based polymerization. An acrylic emulsion (A) is obtained by emulsion polymerization in a reaction field controlled at a reaction temperature of 40 to 100 ° C. in the presence of a polymerization initiator comprising a redox polymerization initiator in which an agent and a reducing agent are combined. Features. When the reaction temperature of emulsion polymerization is less than 40 ° C., polymerization initiation radicals are not easily generated, so a large amount of unreacted unsaturated monomer remains, the odor is strong, and adherend contamination under practical conditions is remarkable. It becomes an adhesive. On the other hand, if the reaction temperature of emulsion polymerization is higher than 100 ° C., grafting and side reactions are likely to occur, and too many polymerization initiation radicals are generated, so that the degree of polymerization and molecular weight of the resulting acrylic emulsion (A) are sufficiently high. It cannot be improved, and the cohesive force required for practical use cannot be achieved.

  The pressure-sensitive adhesive sheet of the present invention can be obtained by a transfer coating method in which the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention having the above characteristics is applied onto a release sheet, dried, and then bonded to a substrate. The pressure-sensitive adhesive sheet of the present invention comprises the water-dispersed acrylic pressure-sensitive adhesive composition of the present invention on a substrate, and the water-dispersed acrylic pressure-sensitive adhesive of the present invention is formed on at least one surface of the substrate. What has an adhesive layer which consists of a composition and provides a peeling sheet in this adhesive layer is preferable. When a release sheet is not used, a base material that has been subjected to a release treatment on one surface may be used to form a so-called single-layer adhesive tape. The water-dispersed acrylic pressure-sensitive adhesive composition of the present invention having the above characteristics can be processed into the pressure-sensitive adhesive sheet of the present invention by applying to a substrate and drying.

The substrate is not particularly limited as long as it is a support for the pressure-sensitive adhesive layer, and is a known synthetic resin film, high-quality paper, coated paper, impregnated paper, or other synthetic paper having a cavity inside, A synthetic resin film, a nonwoven fabric, or the like that has been surface-treated by a primer, corona, plasma discharge treatment, metal deposition, or the like can be used. Among them, a synthetic resin film is preferable in applications where water resistance is expected.
The material of the synthetic resin film is not particularly limited, and is a polyolefin resin such as a polyethylene resin or a polypropylene resin, a polyester resin such as a polybutylene terephthalate resin or a polyethylene terephthalate resin, an acetate resin, an acrylonitrile / butadiene / styrene (ABS) resin, Examples thereof include synthetic resin films such as polystyrene resin, vinyl chloride resin, polyimide resin, polyamide resin, and polylactic acid, and those films subjected to metal vapor deposition such as aluminum.
The synthetic resin film used as the substrate may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.

Although the thickness of a base material does not have a restriction | limiting in particular, Usually, it is the range of 10-200 micrometers, Preferably it is 25-150 micrometers from the surface of the ease of handling. The substrate may be colored or colorless and transparent. Further, printing, printing, or the like may be performed on one surface of the base material. Therefore, the surface for printing, printing, etc. of the substrate is provided with a heat-sensitive recording layer, a thermal transfer layer, a printing image receiving layer capable of ink jetting, laser printing, etc., and an easy adhesion treatment layer such as a printability improving layer. Also good.
In addition, the surface for forming the pressure-sensitive adhesive layer of the base material may be provided with an easy adhesion treatment layer such as primer treatment, corona, plasma discharge treatment or the like for the purpose of further improving the anchor effect with the pressure-sensitive adhesive layer. Good.

The release sheet is not particularly limited, and it is desirable that the release sheet layer is formed on the release sheet base material. Examples of the release sheet substrate include paper, synthetic paper, and synthetic resin film.
As the paper, for example, a paper base such as fine paper, glassine paper, coated paper, a paper base such as a laminated paper obtained by laminating a thermoplastic resin such as polyethylene or polypropylene to these paper bases, and high-quality paper, Glassine paper, coated paper, etc. include paper bases treated with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, etc., and synthetic resin films include, for example, polyethylene resins, polyolefin resins such as polypropylene resins, Examples thereof include films made of a polyester resin such as polybutylene terephthalate resin and polyethylene terephthalate resin, and films obtained by providing an easy adhesion treatment layer on these synthetic resin films.
The release agent layer can be formed using a known release agent. Examples of the release agent include silicone resins, fluorine resins, long chain alkyl-containing resins, alkyd resins, polyolefin resins, and isoprene. Preferably, at least one selected from rubber-based elastomers such as a base resin and a butadiene-based resin is used.
The thickness of the release agent layer is preferably 0.01 to 2.0 μm, more preferably 0.03 to 1.8 μm, and still more preferably 0.05 to 1.5 μm. There is no restriction | limiting in particular in the thickness of the base material for release sheets, Usually, it is 30-200 micrometers.

As a method for producing the pressure-sensitive adhesive sheet of the present invention, a transfer coating method in which the water-dispersed acrylic pressure-sensitive adhesive composition is applied to a release sheet and dried to form a pressure-sensitive adhesive layer, and then bonded to a substrate. Can be adopted. Or the direct coating method which forms an adhesive layer directly on the base-material surface may be sufficient. Furthermore, the adhesiveness of a base material and an adhesive can also be improved by what is called a heat lamination method which heats the base material before bonding with an adhesive, or the base material after bonding.
The coating method of the pressure-sensitive adhesive composition is not particularly limited, and conventionally known coating methods can be used. For example, a comma coater, a knife coater, a roll coater, a roll knife coater, a dip coater, a gravure coater, and a vario gravure coater. And a method using a coating apparatus such as an air knife coater, a bar coater, a die coater, or a curtain coater.

  Although there is no restriction | limiting in particular in the thickness of an adhesive layer, Usually, 5-100 micrometers, Preferably it is 10-80 micrometers, More preferably, it is 15-50 micrometers. The thickness of the pressure-sensitive adhesive sheet obtained by laminating the substrate, the pressure-sensitive adhesive layer and the release sheet is preferably such that it can be introduced into a printer or the like, and is usually 20 to 300 μm, preferably 30 to 250 μm.

  The pressure-sensitive adhesive sheet of the present invention may be a flat sheet or may be rolled up. The adherend to which the pressure-sensitive adhesive sheet of the present invention is affixed may be a flat plate, a cylindrical one, or a three-dimensional curved surface.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.
Measurement and evaluation of the physical or mechanical properties of the dried film of the water-dispersed acrylic pressure-sensitive adhesive composition obtained in the examples and comparative examples were performed as follows.

(Preparation method of substrate-less adhesive sheet)
Using a roll knife coater on the release-treated surface of a light release film obtained by applying a polydimethylsiloxane release agent to a 38 μm-thick polyethylene terephthalate (PET) film, the coating thickness after drying is 25 μm. The water-dispersed acrylic pressure-sensitive adhesive compositions obtained in Examples and Comparative Examples were applied and dried at 90 ° C. for 1 minute to form a dry film of the pressure-sensitive adhesive composition. Next, a baseless pressure-sensitive adhesive sheet formed by adding a heavy release additive made of a silicone resin to the same polydimethylsiloxane release agent as the light release film and pasting it together with a difference in release force. Created. The obtained substrate-less pressure-sensitive adhesive sheet was collected under the conditions (i) and (ii) below, and was used as sample (i) and sample (ii), respectively, and the gel fraction and weight average molecular weight were measured.
(I) Immediately after creating the substrate-less adhesive sheet.
(Ii) After creating a substrate-less pressure-sensitive adhesive sheet, after aging in a 40 ° C. environment for 7 days.

(1) Gel fraction In the present invention, the gel fraction (i) and the gel fraction (ii) are obtained by measuring the gel fraction of the sample (i) and the sample (ii) obtained as described above, respectively. I got it.
First, only the pressure-sensitive adhesive layer in each of the above-mentioned substrate-less pressure-sensitive adhesive sheet sample (i) and sample (ii) cut to 100 mm × 100 mm was taken from the release sheet, and the weight was measured in advance 150 mm × 150 mm, # 300 mesh ( SUS420) was used as a test sample. The test sample was taken out after being immersed in 100 mL of THF for 3 days in an environment of 23 ° C. and 50% RH. The test sample taken out was dried at 110 ° C. for 1 hour, and then the weight was measured. The gel fraction was calculated from the weight ratio of the pressure-sensitive adhesive before and after immersion according to the following formula.
Gel fraction (%)
= [(Residual adhesive layer weight after immersion) / (Adhesive layer weight before immersion)] × 100
Moreover, the difference of the gel fraction (i) and the gel fraction (ii) was calculated | required by the formula: Gel fraction (ii)-gel fraction (i).

(2) Weight average molecular weight of solvent-soluble content Using the following apparatus, the sample (i) obtained as described above was used for calculation in terms of polystyrene.
Apparatus: HLC-8020 manufactured by Tosoh Corporation, column: TSK guard column HXL-H + TSKgel GMHXL × 2 + TSKgel G2000HXL manufactured by Tosoh Corporation, flow rate: 1.0 ml / min, injection amount: 80 μl, column temperature: 42 ° C., eluent : THF, injection sample concentration: 1% by mass, detector: differential refractometer (RI)

(Production method of adhesive sheet)
A roll of the water-dispersed acrylic pressure-sensitive adhesive composition obtained in Examples and Comparative Examples on a release-treated surface of a release sheet [“SP-8K Ao, manufactured by Lintec Co., Ltd., glassine paper peel-treated with silicone resin]” Using a knife coater, coating was performed so that the coating thickness after drying was 25 μm, and drying was performed at 90 ° C. for 1 minute to form a dry film of the pressure-sensitive adhesive composition. The dry film and polypropylene synthetic paper [“YUPO SGS80”, manufactured by YUPO Corporation] were bonded together to obtain an adhesive sheet. The pressure-sensitive adhesive sheet thus obtained was evaluated for adhesive strength, curved surface sticking property, and removability.
(3) Adhesive strength After preparing an adhesive sheet and aging for 7 days in an environment of 23 ° C. and 50% RH, the adhesive was cut to 25 mm × 300 mm in an environment of 23 ° C. and 50% RH based on JIS Z 0237. A sheet test piece was attached to an adherend (SUS304 having a surface polished with # 360 water-resistant abrasive paper) to obtain a test sample. The adhesive strength 24 hours after application was measured by a 180 ° peeling method at a pulling speed of 300 mm / min.

(4) After preparing a substrate adhesive pressure-sensitive adhesive sheet and aging in a 23 ° C., 50% RH environment for 7 days, after peeling the release sheet, rubbing the pressure-sensitive adhesive layer with a finger until the pressure-sensitive adhesive layer falls off Evaluated the number of times.
○: The pressure-sensitive adhesive layer does not fall off even when rubbed 5 times or more.
X: The pressure-sensitive adhesive layer falls off within 5 times.

(5) Removability A pressure-sensitive adhesive sheet was prepared and aged for 7 days in an environment of 23 ° C. and 50% RH, and then a pressure-sensitive adhesive sheet test piece cut to 30 mm × 50 mm was covered in an environment of 23 ° C. and 50% RH. It was affixed to an adherend (SUS304 whose surface was polished with # 600 water-resistant abrasive paper). After standing at 23 ° C. and 50% RH for 1 day, after standing at 70 ° C. (condition A) and 40 ° C. and 80% RH (condition B) for 7 days, 23 ° C. and 50% RH It returned to the environment and it was set as the test sample after leaving still for one day. It peeled by hand at the speed | rate of about 300 mm / min, and the peeling state was observed.
○: No adhesive remains on the adherend.
Xa: The interface between the base material and the pressure-sensitive adhesive layer is destroyed.
Xb: The adherend is contaminated or cloudy.
Xc: There is cohesive failure of the pressure-sensitive adhesive layer.

(6) Curved surface adhesiveness After preparing an adhesive sheet and aging for 7 days in an environment of 23 ° C. and 50% RH, an adhesive sheet test piece cut to 25 mm × 25 mm in an environment of 23 ° C. and 50% RH, It affixed so that the base-material flow (MD: Machine direction) direction might wind on the outer periphery with respect to the round-rod adherend made from polypropylene of diameter 10mmphi. Seven days after pasting, the degree of peeling in the direction of flow of the substrate was measured.
○: Peeling length is less than 5 mm ×: Peeling length is 5 mm or more

Example 1
In a container equipped with a stirrer, a thermometer, and a dropping funnel, 93 parts by mass of 2-ethylhexyl acrylate (2EHA) and 5 parts by mass of methyl methacrylate (MMA) as the component (a1), and methacrylic acid (MAA) as the component (a2) ) 1.0 part by mass and 1.0 part by mass of acrylic acid (AA), 0.1 part by mass of lauryl mercaptan as a chain transfer agent, and sodium polyoxyethylene alkyl ether sulfate [anionic non-reactive emulsifier as an emulsifier "La Temu Le E-118B", manufactured by Kao Corporation], 2 parts by mass, arylalkyl sodium sulfosuccinate [anionic reactive emulsifier "Eleminol JS-2", manufactured by Sanyo Chemical Co., Ltd.] 3 parts by mass of ion-exchanged water 56 An emulsion of an unsaturated monomer mixture was prepared in advance by adding part by mass and stirring at room temperature.
Separately, 28 parts by mass of ion-exchanged water was charged into a reactor equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet tube, and dropping funnel, and nitrogen was sealed, and the reaction temperature was raised to 60 ° C. While maintaining, 2 parts by mass of a 5% by mass potassium persulfate aqueous solution and 0.8 part by mass of a 5% by mass sodium hydrogen sulfite aqueous solution were charged as a redox polymerization initiator to obtain a redox polymerization initiator solution.
Next, the previously prepared emulsion of the unsaturated monomer mixture was transferred to a dropping funnel and dropped over 4 hours. In parallel with this, 2 parts by mass of a 5% by mass aqueous potassium persulfate solution and 0.8 part by mass of a 5% by mass aqueous sodium hydrogen sulfite solution were added dropwise as a redox polymerization initiator solution to carry out emulsion polymerization at a reaction temperature of 60 ° C. .
After completion of dropping, the mixture was aged at 60 ° C. for 2 hours to obtain an emulsion polymerization composition. Thereafter, the mixture was cooled to room temperature and neutralized with 25% aqueous ammonia, and then purified water was added to adjust the solid content to 50% by mass and pH to 8.5.
Furthermore, a thickener [“ASE-60”, manufactured by Rohm and Haas Japan Co., Ltd.] is added to the emulsion polymerization composition, and the viscosity is 10,000 mPa · s [using a BM viscometer, # 4 rotor, 12 revolutions / minute, measured at 25 ° C.]. To 100 parts by mass of the emulsion polymerization composition, 0.8 parts by mass of an epoxy crosslinking agent [“Denacol EX-313”, manufactured by Nagase ChemteX Corporation, glycerol polyglycidyl ether] is added immediately before coating, A dispersed acrylic pressure-sensitive adhesive composition was obtained. As described above, a substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared, and the gel fraction and the weight average molecular weight were measured, and the adhesive strength, curved surface sticking property and removability were evaluated.

Example 2
The amount of 2EHA used was 83 parts by mass, the amount of lauryl mercaptan used was 0.15 parts by mass, and as component (a1), methyl acrylate (MA) was added in an amount of 10 parts by mass. A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared, and the same measurement and evaluation were performed.

Example 3
The composition of the unsaturated monomer mixture is 97.5 parts by mass of n-butyl acrylate (BA) as component (a1), and 1.0 part by mass of 2-hydroxyethyl methacrylate (2-HEMA) as component (a3). , MAA 1.5 parts by weight, and the same procedure as in Example 1 was conducted except that the amount of the epoxy crosslinking agent used was 0.6 parts by weight with respect to 100 parts by weight of the emulsion polymerization composition. Sheets were prepared and subjected to similar measurements and evaluations.

Example 4
After obtaining an emulsion polymerization composition, a substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that 3.5 parts by mass of 1M KOH aqueous solution was added, and the same measurement and evaluation were performed. .

Example 5
The amount of BA used is 98 parts by weight, 1.0A part by weight of AA is used instead of 1.5 parts by weight of MAA, and the amount of epoxy crosslinking agent used is 0.5 parts by weight with respect to 100 parts by weight of the emulsion polymerization composition. A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that the same measurement and evaluation were performed.

Example 6
A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that the polymerization reaction was performed at a reaction temperature of 80 ° C., and the same measurement and evaluation were performed.

Example 7
A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that the amount of lauryl mercaptan was changed to 0.05 part by mass, and the same measurement and evaluation were performed.

Example 8
The amount of BA used was 96 parts by mass, the amount of methacrylic acid used was 3.0 parts by mass, and the amount of the epoxy crosslinking agent used was 1.2 parts by mass with respect to 100 parts by mass of the emulsion polymerization composition. It carried out similarly to Example 3, produced the base material-less adhesive sheet and the adhesive sheet, and performed the same measurement and evaluation.

Example 9
Example 3 except that 3.8 parts by mass of an oxazoline-based crosslinking agent [“Epocross WS-700”, manufactured by Nippon Shokubai Co., Ltd.] was used instead of the epoxy-based crosslinking agent with respect to 100 parts by mass of the emulsion polymerization composition. The substrate-less pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet were prepared, and the same measurement and evaluation were performed.

Example 10
Similar to Example 3 except that carbodiimide-based crosslinking agent [“Carbodilite V-04”, manufactured by Nisshinbo Chemical Co., Ltd.] was used in place of the epoxy-based crosslinking agent in an amount of 3.0 parts by mass with respect to 100 parts by mass of the emulsion polymerization composition. The substrate-less pressure-sensitive adhesive sheet and the pressure-sensitive adhesive sheet were prepared, and the same measurement and evaluation were performed.

Example 11
A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that 2EHA 97.5 parts by mass was used instead of BA 97.5 parts by mass, and the same measurement and evaluation were performed.

Example 12
5 parts by mass of a tackifier resin ["Recatac F105", manufactured by Rika Finetech Co., Ltd.] is added to the unsaturated monomer mixture, and the amount of the epoxy crosslinking agent used is 1 part by mass with respect to 100 parts by mass of the emulsion polymerization composition. Except for changing to 0.0 parts by mass, the same procedure as in Example 11 was performed to prepare a base material-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet, and the same measurement and evaluation were performed.

Example 13
5 parts by mass of a tackifier resin [“YS Resin TO125”, manufactured by Yasuhara Chemical Co., Ltd.] is added to the unsaturated monomer mixture, and the amount of the epoxy crosslinking agent used is 1. A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 11 except that the content was 0 part by mass, and the same measurement and evaluation were performed.

Example 14
Substrate-less, in the same manner as in Example 11, except that 8.0 parts by mass of a tackifier resin ["Superester E-865NT", manufactured by Arakawa Chemical Co., Ltd.] is used with respect to 100 parts by mass of the emulsion polymerization composition. A pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared, and the same measurement and evaluation were performed.

Example 15
Instead of sodium polyoxyethylene alkyl ether sulfate and sodium allyl alkyl sulfosuccinate as an emulsifier, allyl ether-modified polyoxyethylene alkyl ether ammonium sulfate [anionic reactive emulsifier “Aqualon KH-05”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.] .5 parts by mass, 1.0 part by mass of polyoxyethylene lauryl ether (nonionic non-reactive emulsifier “Emulgen 103”, manufactured by Kao Corporation), an aqueous potassium persulfate solution and sodium bisulfite as a redox polymerization initiator Example except that 15 parts by mass of 2% by mass tert-butyl hydroperoxide aqueous solution and 15 parts by mass of 1% by mass L-ascorbic acid aqueous solution were used in place of the aqueous solution, and the amount of lauryl mercaptan used was 0.01 parts by mass. Same as 11 To prepare a substrate-less pressure-sensitive adhesive sheet and the adhesive sheet was subjected to the same measurement and evaluation.

Comparative Example 1
A substrateless pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1 except that 5% by mass of sodium hydrogen sulfite was not used and the polymerization temperature was set to 80 ° C., and the same measurement and evaluation were performed. .

Comparative Example 2
A substrate-less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 3 except that 5% by mass of sodium hydrogen sulfite was not used and the polymerization temperature was set to a reaction temperature of 80 ° C., and the same measurement and evaluation were performed. .

Comparative Example 3
A substrateless pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared in the same manner as in Comparative Example 2 except that the amount of the epoxy-based crosslinking agent used was 1.0 part by weight with respect to 100 parts by weight of the emulsion polymerization composition. And evaluated.

Comparative Example 4
The same procedure as in Comparative Example 2 was conducted except that the amount of lauryl mercaptan was 0.3 parts by mass, and the amount of the epoxy crosslinking agent was 1.5 parts by mass with respect to 100 parts by mass of the emulsion polymerization composition. A less pressure-sensitive adhesive sheet and a pressure-sensitive adhesive sheet were prepared, and the same measurement and evaluation were performed.

  Tables 1 and 2 show the composition of the monomer composition and the crosslinking agent (B) in the acrylic emulsion (A) in Examples 1 to 15 and Comparative Examples 1 to 4 and the obtained results.

From the results of Tables 1 and 2, the following can be understood.
Examples 1 to 15 are excellent in adhesive strength and curved surface sticking property, and are removable (adhesiveness between the base material and the adhesive, the adhesive) despite being an adhesive sheet obtained by the transfer coating method. It can be seen that a pressure-sensitive adhesive layer having high cohesive force and low adherend contamination is obtained.
On the other hand, compared with Examples 1-15, in Comparative Examples 1-3, removability is inadequate and curved sticking property is bad, and in Comparative Example 4, although curved sticking property is excellent, removability is bad. Recognize.

  The water-dispersed acrylic pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet of the present invention are excellent in the balance between adhesion and cohesive strength to a substrate and an adherend, and are made of a paper substrate such as high-quality paper or a hardly adhesive substrate. Excellent anchoring effect to a film of synthetic resin, etc., which is excellent in adhesive strength and curved surface adhesion, can be applied to an adherend for a long time without being lifted off, and transfer coating method The manufactured adhesive sheet is excellent in re-peelability that can be easily peeled off without causing any adhesive residue on the adherend after a long period of time has passed since sticking. For this reason, for packaging and binding, for office and home use, for bonding, for coating masking, for surface protection, for anticorrosion, waterproofing and sealing, for electrical insulation, for electronic equipment and optical parts, for building materials, for vehicles, various industries It can be advantageously used for labels, adhesive films, laminate films, tapes, advertisement / display stickers, surface masks, surface protective films, etc. .

Claims (6)

(A1) Unsaturation containing 50 to 99.5% by mass of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of alkyl group, and (a2) 0.5 to 10% by mass of carboxyl group-containing unsaturated monomer An acrylic emulsion obtained by emulsion polymerization of a monomer mixture in the presence of a polymerization initiator comprising a redox polymerization initiator in which a persulfate and / or peroxide polymerization initiator and a reducing agent are combined ( A water-dispersed acrylic pressure-sensitive adhesive composition comprising A) and a crosslinking agent (B), the water-dispersed acrylic pressure-sensitive adhesive composition applied onto a release sheet, dried, and bonded to a substrate The weight average molecular weight of the solvent-soluble component in the dried film immediately after is 150,000 to 5840,000 , and the gel fraction (i) in the dried film is 0% or more and less than 60%, and aging is performed at 40 ° C. for 7 days. Gel content in dried film (Ii) is less than 50% or more 99%, gel fraction (i) and water-dispersible acrylic pressure-sensitive adhesive composition characterized by the difference is at least 20% of the gel fraction (ii).   The water-dispersed acrylic pressure-sensitive adhesive composition according to claim 1, wherein the carboxyl group-containing unsaturated monomer of component (a2) is at least one selected from acrylic acid and methacrylic acid.   The crosslinking agent (B) is at least one selected from an epoxy compound, a carbodiimide compound, and an oxazoline compound, and the crosslinking functional group of the crosslinking agent is 0. The water-dispersed acrylic pressure-sensitive adhesive composition according to claim 1 or 2, which is contained in an amount of 01 to 5 equivalents. A method for producing a water-dispersed acrylic pressure-sensitive adhesive composition comprising an acrylic emulsion (A) and a crosslinking agent (B),
The water-dispersed acrylic pressure-sensitive adhesive composition is a weight-average solvent-soluble content in a dry film immediately after the water-dispersed acrylic pressure-sensitive adhesive composition is applied onto a release sheet, dried, and bonded to a substrate. The molecular weight is 150,000 or more, the gel fraction (i) in the dry film is 0% or more and less than 60%, and the gel fraction (ii) in the dry film after aging at 40 ° C. for 7 days is 50% or more. Less than 99%, the difference between the gel fraction (i) and the gel fraction (ii) is 20% or more,
(A1) 50 to 99.5% by mass of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, (a2) 0.5 to 10% by mass of a carboxyl group-containing unsaturated monomer, and an emulsifier. In addition, an emulsion of the unsaturated monomer mixture to be added and a polymerization initiator composed of a redox polymerization initiator in which a persulfate and / or peroxide polymerization initiator and a reducing agent are combined are added in parallel. , A step of obtaining an acrylic emulsion (A) by emulsion polymerization in a reaction field controlled at a reaction temperature of 60 to 100 ° C., and
A method for producing a water-dispersed acrylic pressure-sensitive adhesive composition comprising a step of further blending a crosslinking agent (B) with an acrylic emulsion (A). The adhesive sheet which provides the water-dispersed acrylic adhesive composition in any one of Claims 1-3 on a base material. A method for producing a pressure-sensitive adhesive sheet obtained by a transfer coating method in which the water-dispersed acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 3 is applied on a release sheet and dried, and then bonded to a substrate.