Adhesive composition, adhesive sheet, and article

Abstract

An adhesive composition containing a block copolymer (A) comprising a polymer block (C) that has a glass transition temperature of 10-90°C and a (meth) acrylic polymer block (D) that has a glass transition temperature lower than 10°C but not lower than -80°C, wherein the polymer block (C) includes a structural unit (U1) derived from an imide group-containing vinyl monomer and a structural unit (U2) derived from a (meth) acrylic monomer, the content ratio of the total amount of the structural unit (U1) and the structural unit (U2) being at least 80 mass% with respect to all of the structural units of the polymer block (C), and the storage elastic modulus of the adhesive layer is 1.0 MPa or less at 23°C.

Description

Adhesive composition, adhesive sheet and product

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-103709, filed on June 23, 2023, the entirety of which is incorporated herein by reference. The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a product, and more particularly to a technology for improving the hot water washability of a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition and a product including the pressure-sensitive adhesive layer.

[0002] In the field of clothing and other products, a seamless manufacturing method in which fabrics are bonded together with adhesive instead of being sewn together is attracting attention. In addition to improving design, seamless products have other advantages, such as reduced skin irritation in underwear and improved wind resistance and heat retention in winter clothing.

[0003] A method using a urethane-based hot melt adhesive is widely known as a technique for bonding fabrics together by adhesive processing (see, for example, Patent Document 1 and Patent Document 2). However, urethane-based hot melt adhesives have drawbacks, such as hardening the bonded area, resulting in poor texture and discomfort, and insufficient kickback, which makes the fabric prone to rippling when stretched after bonding.

[0004] In response to these disadvantages of urethane-based hot melt adhesives, a pressure-sensitive adhesive composition has been proposed as a pressure-sensitive adhesive composition for bonding textile fabrics for clothing, which contains a (meth)acrylic polymer having a number-average molecular weight of 30,000 or more, and in which the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition has a storage modulus at 23°C of 1.0 MPa or less, and the content of a vinyl polymer having a number-average molecular weight of 10,000 or less is 5 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (see Patent Document 3).

[0005] JP 2016-074996 A JP 2017-078232 A JP 2021-075585 A

[0006] In recent years, an increasing number of household washing machines are capable of washing with hot water at 40°C or 60°C, as these are expected to provide improved cleaning effects, sterilization effects, and effects such as reducing residual detergent. However, urethane-based hot melt adhesives and the conventional adhesive composition described in Patent Document 3 are prone to peeling at the adhesive points on fabrics after repeated hot water washing, and have poor hot water washability. Furthermore, urethane-based hot melt adhesives have poor adhesion to high-density fabrics and water-repellent fabrics, leaving room for further improvement.

[0007] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has excellent resistance to hot water washing while maintaining good adhesion and kickback properties in addition to flexibility and texture at the bonded area.

[0008] The present inventors have conducted extensive research to solve the above problems, and have found that the above problems can be solved by using a specific block copolymer as a polymer component of a pressure-sensitive adhesive layer, thereby completing the present disclosure. Specifically, the present disclosure provides the following aspects.

[0009] [1] A pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition comprising: a block copolymer (A) having a polymer block (C) having a glass transition temperature of 10°C or more and 90°C or less; and a (meth)acrylic polymer block (D) having a glass transition temperature of -80°C or more and less than 10°C; the polymer block (C) comprises a structural unit (U1) derived from an imide group-containing vinyl monomer and a structural unit (U2) derived from a (meth)acrylic monomer; the total content of the structural unit (U1) and the structural unit (U2) is 80 mass% or more based on all structural units of the polymer block (C); and the pressure-sensitive adhesive layer has a storage modulus at 23°C of 1.0 MPa or less.

[0010] [2] The pressure-sensitive adhesive composition according to the above [1], wherein the (meth)acrylic polymer block (D) contains structural units derived from a (meth)acrylic acid ester having a hydrocarbon group having 3 or more carbon atoms in an amount of 20 mass% or more relative to all structural units of the (meth)acrylic polymer block (D). [3] The pressure-sensitive adhesive composition according to the above [1] or [2], wherein the structural unit (U2) is a structural unit derived from a compound represented by the following formula (1): CH ２ =CR １ -C(=O)O(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. n represents an integer of 0 to 100. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the content of structural units derived from an aromatic vinyl compound in the polymer block (C) is 10 mass% or less based on the total structural units of the polymer block (C). [5] The pressure-sensitive adhesive composition according to any one of [1] to [4] above, wherein the block copolymer (A) comprises a triblock copolymer of polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C). [6] The pressure-sensitive adhesive composition according to any one of [1] to [5] above, wherein the block copolymer (A) has a weight-average molecular weight of 100,000 or more. [7] The pressure-sensitive adhesive composition according to any one of [1] to [6] above, further comprising a silane coupling agent. [8] The pressure-sensitive adhesive composition according to [7] above, wherein the silane coupling agent has at least one selected from the group consisting of an epoxy group, a (meth)acryloyl group, an isocyanate group, and a blocked isocyanate group. [9] The pressure-sensitive adhesive composition according to any one of [1] to [8] above, further comprising a modified olefin-based polymer or a diene-based polymer.

[10] The pressure-sensitive adhesive composition according to [9] above, wherein the modified polymer is at least one selected from the group consisting of a chlorinated polymer, a maleic anhydride-modified polymer, and a maleic anhydride-modified chlorinated polymer.

[11] The pressure-sensitive adhesive composition according to any one of [1] to

[10] above, further comprising a vinyl polymer (B) having a glass transition temperature of 30°C or higher and 200°C or lower and a number average molecular weight of 500 or higher and 10,000 or lower (excluding modified olefin-based polymers or diene-based polymers).

[12] The pressure-sensitive adhesive composition according to

[11] above, wherein the vinyl polymer (B) contains a structural unit derived from an aliphatic cyclic vinyl monomer.

[13] The pressure-sensitive adhesive composition according to

[11] or

[12] above, wherein the content of the vinyl polymer (B) is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the block copolymer (A).

[14] The pressure-sensitive adhesive composition according to any one of [1] to

[13] above, further comprising an isocyanate-based crosslinking agent.

[15] The pressure-sensitive adhesive composition according to any one of [1] to

[14] above, further comprising fine particles.

[16] A pressure-sensitive adhesive sheet comprising a support and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to

[15] above.

[17] A product comprising a first adherend, a second adherend, and a pressure-sensitive adhesive layer, wherein the first adherend and the second adherend are bonded via the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition according to any one of [1] to

[15] above.

[0011] The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer that is excellent in hot water washability while maintaining good adhesion and kickback properties in addition to flexibility and texture at the bonded area. Furthermore, by bonding adherends together via a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of the present disclosure, it is possible to obtain a product that is excellent in hot water washability while maintaining flexibility and texture at the bonded area, high adhesive strength, and good kickback properties.

[0012] The present disclosure will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. "(meth)acrylate" means acrylate and / or methacrylate. "(meth)acrylo" means acrylo and / or methacrylo.

[0013] <<Adhesive Composition>> The adhesive composition of the present disclosure (hereinafter also referred to as "the composition") is a polymer composition used to form a pressure-sensitive adhesive layer, and is preferably used to bond flexible adherends such as fiber fabrics, resin films, natural leather, etc. When the composition is used to bond adherends, the adherends to be bonded may be of the same type or different types. The composition contains a block copolymer (A) having a polymer block (C) having a glass transition temperature of 10°C or higher and 90°C or lower, and a (meth)acrylic polymer block (D) having a glass transition temperature of -80°C or higher and lower than 10°C. The block copolymer (A) and the components to be blended as needed in the composition are described in detail below.

[0014] <Block Copolymer (A)> The polymer block (C) and the (meth)acrylic polymer block (D) contained in the block copolymer (A) are segments having different monomer compositions. The polymer block (C) is a segment having a relatively high glass transition temperature, and the (meth)acrylic polymer block (D) is a segment having a relatively low glass transition temperature. By having the polymer block (C) and the (meth)acrylic polymer block (D), the block copolymer (A) forms pseudo-crosslinks between or within molecules due to a microphase separation structure or the like, which is thought to result in improved cohesive strength.

[0015] In this specification, the glass transition temperature (Tg) of a polymer is a value measured by differential scanning calorimetry (DSC). Details of the measurement method follow the method described in the Examples below. In this specification, the Tg of each polymer block is a value determined by synthesizing a polymer from monomers constituting the polymer block to be measured and measuring the Tg of the polymer by DSC. The Tg of the polymer can be selected arbitrarily by changing the type and composition of the constituent monomers, etc.

[0016] Polymer Block (C) The polymer block (C) has a Tg of 10°C or higher and 90°C or lower. If the Tg of the polymer block (C) is lower than 10°C, the cohesive strength cannot be sufficiently improved by pseudo-crosslinking formed by the microphase-separated structure of the block copolymer (A), and the hot-water washability and adhesiveness of the pressure-sensitive adhesive layer cannot be sufficiently ensured. Furthermore, if the Tg of the polymer block (C) exceeds 90°C, the adhesion to the adherend surface decreases, resulting in insufficient adhesive strength when bonding flexible adherends such as fibrous fabrics, or insufficient hot-water washability. Furthermore, if the ratio of the polymer block (C) in the block copolymer (A) is increased or the molecular weight of the block copolymer (A) is increased in order to ensure good adhesive strength, there is a concern that flexibility may not be ensured. From the viewpoint of improving the hot-water washability and adhesiveness of the pressure-sensitive adhesive layer, the Tg of the polymer block (C) is preferably 15°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and even more preferably 30°C or higher. The upper limit of the Tg of the polymer block (C) is preferably 85°C or lower, more preferably 80°C or lower, even more preferably 75°C or lower, and even more preferably 70°C or lower, from the viewpoint of sufficiently improving the hot water washability and the adhesive strength when flexible adherends are bonded together.

[0017] The polymer block (C) can be obtained by polymerizing a vinyl monomer. The polymer block (C) contains a structural unit (U1) derived from an imide group-containing vinyl monomer and a structural unit (U2) derived from a (meth)acrylic monomer (excluding imide group-containing vinyl monomers), and the total content of the structural units (U1) and (U2) in the polymer block (C) is 80 mass% or more based on the total structural units of the polymer block (C). When the polymer block (C) contains the structural unit derived from the imide group-containing vinyl monomer and the structural unit derived from the (meth)acrylic monomer in the above ranges, a PSA layer exhibiting excellent hot water washability can be formed.

[0018] Examples of the imide group-containing vinyl monomer include maleimide compounds such as maleimide and N-substituted maleimide compounds; itaconimide compounds such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; and citraconic compounds such as N-methylcitraconimide, N-ethylcitraconimide, N-butylcitraconimide, N-octylcitraconimide, N-2-ethylhexylcitraconimide, N-cyclohexylcitraconimide, and N-laurylcitraconimide. Of these, maleimide compounds are preferably used as the imide group-containing vinyl compound.

[0019] As the maleimide compound, at least one selected from the group consisting of maleimide and N-substituted maleimide compounds can be preferably used. Examples of the N-substituted maleimide compound include N-alkyl-substituted maleimide compounds such as N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearylmaleimide; N-cyclopentylmaleimide and N-cyclopentylmaleimide; Examples of such compounds include N-cycloalkyl-substituted maleimide compounds such as cyclohexylmaleimide; N-aralkyl-substituted maleimide compounds such as N-benzylmaleimide; and N-aryl-substituted maleimide compounds such as N-phenylmaleimide, N-(4-hydroxyphenyl)maleimide, N-(4-acetylphenyl)maleimide, N-(4-methoxyphenyl)maleimide, N-(4-ethoxyphenyl)maleimide, N-(4-chlorophenyl)maleimide, and N-(4-bromophenyl)maleimide. One or more of these compounds can be used as the imide group-containing vinyl monomer.

[0020] As the imide group-containing vinyl monomer used in producing the block copolymer (A), a compound represented by the following general formula can be preferably used, in that it can provide the block copolymer (A) with better resistance to hot water washing and better adhesion when bonding soft adherends together: (In the formula, R ４ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, a cyclohexyl group, a phenyl group, or a group in which a hydroxy group, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an acetyl group, or a halogen atom is bonded to any position of a cyclohexyl group or a phenyl group.

[0021] The (meth)acrylic monomer is not particularly limited as long as it is a monomer having a (meth)acryloyl group as a group involved in polymerization. Examples of the (meth)acrylic monomer include unsaturated carboxylic acids, unsaturated acid anhydrides, (meth)acrylic acid alkyl esters, (meth)acrylic acid aliphatic cyclic esters, (meth)acrylic acid aromatic esters, (meth)acrylic acid alkoxyalkyl esters, (meth)acrylic acid hydroxyalkyl esters, polyalkylene glycol mono(meth)acrylates, epoxy group-containing (meth)acrylic acid esters, silyl group-containing (meth)acrylic acid esters, amino group-containing (meth)acrylic acid esters, (meth)acrylamide or its derivatives, nitrile group-containing (meth)acrylic acid esters, and (meth)acrylimide compounds. As the (meth)acrylic monomer, compounds having a (meth)acryloyloxy group are preferably used because of the high degree of freedom in the selection of the monomer. The imide group-containing monomer and the (meth)acrylic monomer are different in that the monomer constituting the structural unit (U2) has a (meth)acryloyl group, while the monomer constituting the structural unit (U1) does not have a (meth)acryloyl group.

[0022] Specific examples of these include unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and monoalkyl esters of unsaturated dicarboxylic acids (monoalkyl esters of maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.), etc. Specific examples of unsaturated acid anhydrides include maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0023] Specific examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid alkyl esters having an alkyl group having 1 to 12 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate.

[0024] Specific examples of aliphatic cyclic esters of (meth)acrylic acid include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, etc. Specific examples of aromatic esters of (meth)acrylic acid include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 3-phenoxypropyl (meth)acrylate, etc.

[0025] Specific examples of the (meth)acrylic acid alkoxyalkyl ester include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-propoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, ethoxypropyl (meth)acrylate, n-propoxypropyl (meth)acrylate, n-butoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, n-propoxybutyl (meth)acrylate, and n-butoxybutyl (meth)acrylate.

[0026] Specific examples of hydroxyalkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, etc. Specific examples of polyalkylene glycol mono(meth)acrylates include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polyethylene glycol-polypropylene glycol mono(meth)acrylate, etc.

[0027] Specific examples of epoxy group-containing (meth)acrylic acid esters include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate, etc. Specific examples of silyl group-containing (meth)acrylic acid esters include trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, methyldimethoxysilylpropyl (meth)acrylate, and dimethylmethoxysilylpropyl (meth)acrylate.

[0028] Specific examples of the amino group-containing (meth)acrylic acid ester include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl (meth)acrylate, 3-dimethylaminopropyl (meth)acrylate, 3-diethylaminopropyl (meth)acrylate, and 3-(di-n-propylamino)propyl (meth)acrylate.

[0029] Specific examples of (meth)acrylamide or a derivative thereof include (meth)acrylamide, tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and (meth)acryloylmorpholine.

[0030] Specific examples of the nitrile group-containing (meth)acrylic acid ester include cyanomethyl (meth)acrylate, 1-cyanoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 1-cyanopropyl (meth)acrylate, 2-cyanopropyl (meth)acrylate, 3-cyanopropyl (meth)acrylate, 4-cyanobutyl (meth)acrylate, 6-cyanohexyl (meth)acrylate, 2-ethyl-6-cyanohexyl (meth)acrylate, and 8-cyanooctyl (meth)acrylate.

[0031] Specific examples of the (meth)acrylimide compound include N-(2-(meth)acryloyloxyethyl)succinimide, N-(2-(meth)acryloyloxyethyl)maleimide, N-(2-(meth)acryloyloxyethyl)phthalimide, N-(4-(meth)acryloyloxybutyl)succinimide, N-(4-(meth)acryloyloxybutyl)maleimide, and N-(4-(meth)acryloyloxybutyl)phthalimide. In producing the polymer block (C), one type of (meth)acrylic monomer may be used alone, or two or more types may be used in combination.

[0032] In producing the polymer block (C), a monomer having a crosslinkable functional group (hereinafter also referred to as a "crosslinkable group-containing monomer") is used, thereby making it possible to give the polymer block (C) a structure having a crosslinkable structural unit. The polymer block (C) having a crosslinkable structural unit can further improve the kickback property while providing excellent hot water washability to the PSA layer. This allows for the production of a product with reduced waviness even when the adherend is stretched after lamination.

[0033] The crosslinkable group-containing monomer used in producing the polymer block (C) is not particularly limited. The crosslinkable group-containing monomer is preferably at least one selected from the group consisting of (meth)acrylic acid, hydroxyalkyl (meth)acrylate, epoxy group-containing (meth)acrylic acid ester, and silyl group-containing (meth)acrylic acid ester. Among these, structural units derived from hydroxyalkyl (meth)acrylate are particularly preferred because they make it easier to control the Tg of the polymer block (C) within the above range. The hydroxyalkyl (meth)acrylate is preferably a compound having a hydroxyalkyl group having 2 to 8 carbon atoms, more preferably a compound having a hydroxyalkyl group having 2 to 4 carbon atoms, from the viewpoint of further improving the adhesive performance of the (meth)acrylic polymer (A).

[0034] From the viewpoint of improving hot water washability and ensuring flexibility and texture at the bonded portion when bonding flexible adherends together, the structural unit (U2) is preferably a structural unit derived from a compound represented by the following formula (1): CH ２ =CR １ -C(=O)O(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and n represents an integer of 0 to 100.

[0035] In the above formula (1), R １ is preferably a hydrogen atom in that it is easy to adjust the Tg of the polymer block (C) to the above range. n is preferably 0 to 50, more preferably 0 to 20, from the viewpoints of easy availability of raw materials and adhesiveness.

[0036] In the polymer block (C), the total content of the structural unit (U1) and the structural unit (U2) is 80% by mass or more, based on all structural units in the polymer block (C). If the total content of the structural unit (U1) and the structural unit (U2) is less than 80% by mass, based on all structural units in the polymer block (C), the hot water washability of the PSA layer is poor, and sufficient adhesive strength cannot be ensured when bonding flexible adherends together. From the viewpoint of achieving excellent hot water washability of the PSA layer and excellent adhesive strength when bonding flexible adherends together, the total content of the structural unit (U1) and the structural unit (U2) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more, based on all structural units in the polymer block (C).

[0037] The ratio of the structural unit (U1) to the structural unit (U2) in the polymer block (C) can be appropriately selected depending on the desired Tg. From the viewpoints of preventing the Tg of the polymer block (C) from becoming too high and further improving the hot water washability and adhesiveness of the PSA layer, the ratio of the structural unit (U2) to the total amount of the structural unit (U1) and the structural unit (U2) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more, per 100 parts by mass of the total amount of the structural unit (U1) and the structural unit (U2).

[0038] Furthermore, when a crosslinkable structural unit is introduced into the polymer block (C), the content of the crosslinkable structural unit in the polymer block (C) is preferably 1% by mass or more, more preferably 2% by mass or more, based on the total structural units of the polymer block (C). By setting the content of the crosslinkable structural unit in the polymer block (C) to 1% by mass or more, a block copolymer (A) having improved kickback properties can be obtained. From the viewpoint of ensuring flexibility at the bonded portion, the upper limit of the content of the crosslinkable structural unit in the polymer block (C) is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total structural units of the polymer block (C).

[0039] The polymer block (C) may further contain a structural unit derived from a monomer (other monomer) that is copolymerizable with at least one of the imide group-containing vinyl monomer and the (meth)acrylic monomer and is different from the imide group-containing vinyl monomer and the (meth)acrylic monomer, within a range that does not impair the function of the block copolymer (A). Examples of the other monomer constituting the polymer block (C) include aromatic vinyl compounds.

[0040] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, p-n-butylstyrene, p-isobutylstyrene, p-tert-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, and styrene-based compounds such as divinylbenzene, as well as vinylnaphthalene. Of these, styrene-based compounds are preferred as aromatic vinyl compounds. One or more of these can be used as the aromatic vinyl compound.

[0041] However, from the viewpoint of improving the hot water washability of the PSA layer and the adhesiveness when bonding flexible adherends together, it is preferable to make the amount of structural units derived from aromatic vinyl compounds in the polymer block (C) as small as possible. Specifically, the content of structural units derived from aromatic vinyl compounds in the polymer block (C) is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total structural units of the polymer block (C).

[0042] In addition to the above, other monomers constituting the polymer block (C) include, for example, aliphatic vinyl compounds such as ethylene and propylene; amide group-containing vinyl compounds such as N-vinylacetamide; polyfunctional alkenyl compounds such as trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, and pentaerythritol diallyl ether; etc. As other monomers constituting the polymer block (C), only one type may be used, or two or more types may be used.

[0043] The number average molecular weight (Mn) of the polymer block (C) is preferably in the range of 1,000 to 70,000. When the Mn of the polymer block (C) is 1,000 or more, the cohesive strength of the block copolymer (A) can be sufficiently ensured, and when it is 70,000 or less, the peel strength from the adherend can be sufficiently increased while maintaining the flexibility of the pressure-sensitive adhesive layer. The Mn of the polymer block (C) is preferably 2,000 or more, more preferably 3,000 or more, even more preferably 5,000 or more, and still more preferably 7,000 or more. The upper limit of the Mn of the polymer block (C) is preferably 65,000 or less, more preferably 60,000 or less, and even more preferably 55,000 or less.

[0044] Furthermore, from the viewpoint of ensuring sufficient cohesive strength of the block copolymer (A), maintaining the flexibility of the pressure-sensitive adhesive layer, and sufficiently increasing the peel strength from the adherend, the weight average molecular weight (Mw) of the polymer block (C) is preferably in the range of 1,000 to 100,000. From the above viewpoints, the Mw of the polymer block (C) is preferably 2,000 or more, more preferably 3,000 or more, even more preferably 6,000 or more, and still more preferably 9,000 or more. The upper limit of the Mw of the polymer block (C) is preferably 90,000 or less, more preferably 85,000 or less, even more preferably 80,000 or less, and still more preferably 75,000 or less. In this specification, the Mw and Mn of the polymer are values ​​calculated in terms of standard polystyrene obtained using gel permeation chromatography (GPC).

[0045] When block copolymer (A) has a plurality of polymer blocks (C) in one molecule, the terms "Mn of polymer block (C)" and "Mw of polymer block (C)" refer to the Mn and Mw, respectively, of all of the polymer blocks (C) in one molecule of block copolymer (A). For example, when block copolymer (A) is a (CDC) type triblock copolymer consisting of polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C), the Mn of polymer block (C) in the triblock copolymer is the sum of the Mn of the two polymer blocks (C).

[0046] (Meth)acrylic polymer block (D) The (meth)acrylic polymer block (D) has a Tg of −80°C or higher and lower than 10°C. If the Tg of the (meth)acrylic polymer block (D) is lower than −80°C, the cohesive strength of the pressure-sensitive adhesive layer obtained from the composition tends to be insufficient, resulting in poor adhesive properties. If the Tg of the (meth)acrylic polymer block (D) is −10°C or higher, the resulting block copolymer tends to be poor in adhesive properties, and in particular, poor adhesive properties cannot be ensured when bonding flexible adherends together. From these viewpoints, the Tg of the (meth)acrylic polymer block (D) is preferably −70°C or higher, more preferably −60°C or higher. The upper limit of the Tg of the (meth)acrylic polymer block (D) is preferably 0°C or lower, more preferably −5°C or lower, even more preferably −10°C or lower, even more preferably −15°C or lower, and even more preferably −20°C or lower, from the viewpoint of enhancing the adhesive properties of the block copolymer (A). The Tg range of the (meth)acrylic polymer block (D) is preferably in the range of -70°C or more and 0°C or less, and more preferably in the range of -60°C or more and -5°C or less.

[0047] The (meth)acrylic polymer block (D) is a polymer containing a (meth)acrylic monomer as a main monomer unit. Examples of the (meth)acrylic monomer constituting the (meth)acrylic polymer block (D) include the same compounds as those exemplified as the (meth)acrylic monomer constituting the polymer block (C).

[0048] From the viewpoint of obtaining a PSA layer having excellent resistance to hot water washing, the (meth)acrylic polymer block (D) preferably contains a structural unit derived from a (meth)acrylic acid ester having a hydrocarbon group having 3 or more carbon atoms. As the (meth)acrylic acid ester having a hydrocarbon group having 3 or more carbon atoms, a (meth)acrylic acid alkyl ester, an aliphatic cyclic ester of (meth)acrylic acid, an aromatic ester of (meth)acrylic acid, an (meth)acrylic acid alkoxyalkyl ester, or a mixture of two or more of these can be preferably used. Specific examples of the (meth)acrylic acid alkyl ester, aliphatic cyclic ester of (meth)acrylic acid, an aromatic ester of (meth)acrylic acid, and an alkoxyalkyl (meth)acrylic acid ester include compounds having a hydrocarbon group having 3 or more carbon atoms among the compounds exemplified in the description of the (meth)acrylic monomer constituting the polymer block (C).

[0049] A compound represented by the following formula (2) can be preferably used as the (meth)acrylic acid ester having a hydrocarbon group having 3 or more carbon atoms, in that it can improve the resistance to hot water washing while ensuring the adhesive properties of the (meth)acrylic polymer block (D). CH ２ =CR ５ -C(=O)O-R ６ ...(2) (In formula (2), R ５ represents a hydrogen atom or a methyl group, R ６ represents an alkyl group having 3 to 20 carbon atoms, an alkoxyalkyl group having 4 to 20 carbon atoms and an alkoxy group having 3 or more carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 6 to 20 carbon atoms.

[0050] In the above formula (2), R ５ is preferably a hydrogen atom, since it is easy to adjust the Tg of the (meth)acrylic polymer block (D) to fall within the above range. ６ is preferably an alkyl group having 3 to 20 carbon atoms, more preferably an alkyl group having 4 to 12 carbon atoms, in that the adhesiveness of the (meth)acrylic polymer block (D) can be further increased.

[0051] In the (meth)acrylic polymer block (D), the content of structural units derived from a (meth)acrylic acid ester having a hydrocarbon group with 3 or more carbon atoms is preferably 20% by mass or more relative to all structural units in the (meth)acrylic polymer block (D). By setting the content of structural units derived from a (meth)acrylic acid ester having a hydrocarbon group with 3 or more carbon atoms to 20% by mass or more, a PSA layer with even better hot water washability can be obtained. From this perspective, the content of structural units derived from a (meth)acrylic acid ester having a hydrocarbon group with 3 or more carbon atoms in the (meth)acrylic polymer block (D) is more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more.

[0052] In order to obtain a polymer block having a relatively low Tg and sufficient adhesiveness, it is preferable that the monomer constituting the (meth)acrylic polymer block (D) contains at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters. Specific examples of the (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters include the same compounds as those exemplified in the description of the polymer block (C).

[0053] In the (meth)acrylic polymer block (D), the content of structural units derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters is preferably 30 mass% or more, more preferably 50 mass% or more, even more preferably 70 mass% or more, even more preferably 80 mass% or more, and still more preferably 90 mass% or more, based on all structural units possessed by the (meth)acrylic polymer block (D). By setting the content of structural units derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid alkoxyalkyl esters within the above range, the adhesive strength and initial adhesive strength (tack) of the resulting pressure-sensitive adhesive composition can be sufficiently increased.

[0054] In particular, from the viewpoint of obtaining a pressure-sensitive adhesive layer having high cohesive strength while maintaining flexibility, the (meth)acrylic polymer block (D) preferably contains structural units derived from a (meth)acrylic acid alkoxyalkyl ester. Specifically, the content of structural units derived from a (meth)acrylic acid alkoxyalkyl ester is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on all structural units contained in the (meth)acrylic polymer block (D). There are no particular limitations on the upper limit of the content of structural units derived from a (meth)acrylic acid alkoxyalkyl ester in the (meth)acrylic polymer block (D), but from the viewpoint of ensuring hot-water washability of the pressure-sensitive adhesive layer, it is preferably 80% by mass or less, more preferably 75% by mass or less, based on all structural units contained in the (meth)acrylic polymer block (D).

[0055] As the (meth)acrylic acid alkoxyalkyl ester constituting the (meth)acrylic polymer block (D), from the viewpoint of obtaining a pressure-sensitive adhesive layer that is flexible and has high cohesive strength, a (meth)acrylic acid alkoxyalkyl ester having an alkoxy group having 1 or 2 carbon atoms can be preferably used.

[0056] In producing the (meth)acrylic polymer block (D), a crosslinkable group-containing monomer may be used to introduce a crosslinkable structural unit into the (meth)acrylic polymer block (D). When the (meth)acrylic polymer block (D) has a crosslinkable structural unit, the kickback property can be improved while ensuring the hot water washability of the PSA layer.

[0057] The crosslinkable group-containing monomer used in the production of the (meth)acrylic polymer block (D) is not particularly limited. From the viewpoint of enhancing the adhesiveness of the (meth)acrylic polymer block (D), the crosslinkable group-containing monomer used in the production of the (meth)acrylic polymer block (D) is preferably at least one selected from the group consisting of (meth)acrylic acid, a hydroxyalkyl (meth)acrylate, an epoxy group-containing (meth)acrylic acid ester, and a silyl group-containing (meth)acrylic acid ester. Among these, at least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate is particularly preferred because it tends to be more effective in enhancing the adhesive strength of the (meth)acrylic polymer block (D).

[0058] When the (meth)acrylic polymer block (D) has a crosslinkable structural unit, the content of the crosslinkable structural unit is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total structural units of the (meth)acrylic polymer block (D). By setting the content of the crosslinkable structural unit in the (meth)acrylic polymer block (D) to 0.1% by mass or more, a good crosslinked structure can be formed, thereby enhancing the effect of improving kickback properties. The upper limit of the content of the crosslinkable structural unit is not particularly limited, but from the viewpoint of increasing the flexibility of the resulting pressure-sensitive adhesive layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to the total structural units of the (meth)acrylic polymer block (D). In addition, when producing the (meth)acrylic polymer block (D), one type of crosslinkable-containing monomer may be used alone, or two or more types may be used in combination.

[0059] In producing the (meth)acrylic polymer block (D), in addition to the above-mentioned monomers, monomers copolymerizable with the above-mentioned monomers (other monomers) may be used as long as the adhesive performance is not impaired. Examples of other monomers constituting the (meth)acrylic polymer block (D) include aliphatic vinyl compounds, amino group-containing vinyl compounds, amide group-containing vinyl compounds, polyfunctional alkenyl compounds, and nitrile group-containing unsaturated compounds. Specific examples of these include the same compounds as those exemplified as the monomers constituting the polymer block (C).

[0060] The polymer block (C) may have the property of phase separation from the (meth)acrylic polymer block (D). Such a property is advantageous in that it facilitates the formation of a microphase-separated structure in the block copolymer (A). Based on the common technical knowledge at the time of filing, a person skilled in the art can easily design a polymer block (C) that phase separates from the (meth)acrylic polymer block (D). For example, the difference ΔSP (absolute value) between the SP value of the polymer block (C) calculated by a known method for calculating the SP value, which is a solubility parameter (e.g., the Fedors method), and the SP value of the (meth)acrylic polymer block (D) may be 0.01 or more. The difference ΔSP is, for example, 0.05 or more, or may be 0.1 or more, or may be 0.5 or more. When using the Fedors method, the SP value is calculated by the R.F. The phase separation property between the blocks can be easily estimated by observing the structure of the intended block copolymer (A) using an electron microscope, a scanning probe microscope, small-angle X-ray scattering, or the like.

[0061] The number and arrangement of blocks of the block copolymer (A) are not particularly limited, as long as the block copolymer (A) has the polymer block (C) and the (meth)acrylic polymer block (D). Specific examples of the block copolymer (A) include a (CD) type diblock copolymer consisting of the polymer block (C) and the (meth)acrylic polymer block (D); a (CDC) type triblock copolymer consisting of the polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C); and a (DCD) type triblock copolymer consisting of the (meth)acrylic polymer block (D)-polymer block (C)-(meth)acrylic polymer block (D). The block copolymer (A) may further have a polymer block other than the polymer block (C) and the (meth)acrylic polymer block (D). Of these, the block copolymer (A) preferably contains a triblock copolymer of the polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C). With such a structure, the block copolymer (A) is likely to form a pseudo-crosslinked structure via the polymer block (C), and the effect of improving both adhesive performance and hot water washability can be sufficiently obtained. The content of the triblock copolymer in the block copolymer (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0062] The ratio of the polymer block (C) to the (meth)acrylic polymer block (D) in the block copolymer (A) (hereinafter also referred to as the "block ratio"), expressed as polymer block (C) / (meth)acrylic polymer block (D), is preferably 3 / 97 to 30 / 70 by mass. When the block ratio is within this range, the block copolymer (A) has the polymer block (C) that constitutes a hard segment and can serve as a pseudo-crosslinking point, and the (meth)acrylic polymer block (D) that can serve as a soft segment, making it possible to obtain a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has excellent hot-water washability and adhesiveness while maintaining a low viscosity. Furthermore, because the Tg of the polymer block (C) is as low as 90°C or less, the block copolymer (A) is less likely to harden even when the ratio of the polymer block (C) is relatively high. This allows for increased adhesive strength while ensuring flexibility and texture at the bonded portion. From these viewpoints, the block ratio is more preferably 6 / 94 to 30 / 70, even more preferably 7 / 93 to 30 / 70, and still more preferably 8 / 92 to 30 / 70. The block ratio can be calculated from the monomers and / or polymer blocks used in the polymerization and the amount of monomer consumed measured by gas chromatography (GC). Details of the calculation method follow the method described in the Examples below.

[0063] From the viewpoint of achieving a sufficient improvement in hot water washability while exhibiting sufficient cohesive strength and good adhesiveness, the Mw of the block copolymer (A) is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and still more preferably 250,000 or more.

[0064] On the other hand, if the Mw of the block copolymer (A) is too large, the flexibility may decrease or the viscosity of the pressure-sensitive adhesive composition may become too high, resulting in deterioration of coatability and handleability. Therefore, the Mw of the block copolymer (A) is preferably 800,000 or less, more preferably 700,000 or less, even more preferably 650,000 or less, and even more preferably 550,000 or less. The Mw of the block copolymer (A) is preferably in the range of 100,000 to 800,000, more preferably 150,000 to 700,000, and even more preferably 200,000 to 650,000.

[0065] From the viewpoint of exhibiting good adhesiveness and sufficient cohesive strength, the Mn of the block copolymer (A) is preferably 80,000 or more, more preferably 100,000 or more, and even more preferably 120,000 or more. From the viewpoint of ease of production, the upper limit of the Mn of the block copolymer (A) is preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. The Mn of the block copolymer (A) is preferably in the range of 80,000 or more and 500,000 or less, more preferably 100,000 or more and 400,000 or less.

[0066] The molecular weight distribution (Mw / Mn) of the block copolymer (A), expressed as the ratio of Mw to Mn, is preferably 5.0 or less, more preferably 4.5 or less, even more preferably 4.0 or less, even more preferably 3.5 or less, and even more preferably 3.3 or less, from the viewpoint of easily obtaining good adhesive strength and suppressing an increase in viscosity of the pressure-sensitive adhesive composition. The lower limit of Mw / Mn of the block copolymer (A) is not particularly limited, and can be 1.0 or more.

[0067] The Tg of the block copolymer (A) is preferably −80° C. or higher and 0° C. or lower. From the viewpoint of ensuring sufficient cohesive strength of the pressure-sensitive adhesive layer obtained from the present composition and obtaining a pressure-sensitive adhesive layer exhibiting good adhesive properties, the Tg of the block copolymer (A) is preferably −70° C. or higher, and more preferably −60° C. or higher. From the viewpoint of improving the adhesive properties of the block copolymer (A), the upper limit of the Tg of the block copolymer (A) is more preferably −10° C. or lower, even more preferably −15° C. or lower, and even more preferably −20° C. or lower. The range of the Tg of the block copolymer (A) is more preferably −80° C. or higher and −10° C. or lower, and even more preferably −70° C. or higher and −15° C. or lower.

[0068] <Method for Producing Block Copolymer (A)> The block copolymer (A) is not particularly limited in terms of the production method, as long as a polymer having the polymer block (C) and the (meth)acrylic polymer block (D) can be obtained, and can be obtained by a known production method. Examples of methods for producing the block copolymer (A) include methods that utilize various controlled polymerization methods such as living radical polymerization and living anionic polymerization, and methods of coupling polymers having functional groups together. Among these, living radical polymerization is preferred because it is easy to operate and can be applied to a wide range of monomers.

[0069] The living radical polymerization may be any of a batch process, a semi-batch process, a dry continuous polymerization process, a continuous stirred tank process (CSTR), etc. The polymerization method may be applied to various modes such as bulk polymerization without using a solvent, solvent-based solution polymerization, aqueous emulsion polymerization, mini-emulsion polymerization, or suspension polymerization.

[0070] There are no particular limitations on the type of living radical polymerization method, and various polymerization methods can be used, such as reversible addition-fragmentation chain transfer polymerization (RAFT method), nitroxy radical method (NMP method), atom transfer radical polymerization (ATRP method), polymerization method using an organotellurium compound (TERP method), polymerization method using an organoantimony compound (SBRP method), polymerization method using an organobismuth compound (BIRP method), and iodine transfer polymerization. Among these, the RAFT method, the NMP method, and the ATRP method are preferred from the viewpoints of controllability of polymerization and ease of implementation.

[0071] In the RAFT method, controlled polymerization proceeds via a reversible chain transfer reaction in the presence of a specific polymerization control agent (RAFT agent) and a general free radical polymerization initiator. Various known RAFT agents can be used as the RAFT agent, such as dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds. As the RAFT agent, a monofunctional compound having only one active site may be used, or a bifunctional or higher functional compound may be used. In terms of efficiently obtaining a block copolymer having three or more blocks, it is preferable to use a bifunctional RAFT agent. The amount of the RAFT agent used is appropriately adjusted depending on the type of monomer and RAFT agent, etc.

[0072] As the polymerization initiator used in polymerization by the RAFT method, known radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used. Of these, azo compounds are preferred because they are safe and easy to handle and are less likely to cause side reactions during radical polymerization. Specific examples of azo compounds include 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], and 2,2'-azobis(N-butyl-2-methylpropionamide). Only one type of polymerization initiator may be used, or two or more types may be used in combination. The proportion of the polymerization initiator used is not particularly limited, but from the viewpoint of stably carrying out the polymerization reaction and obtaining a polymer with a narrower molecular weight distribution, the amount of the polymerization initiator used is preferably 0.01 mol or more and 0.5 mol or less, and more preferably 0.01 mol or more and 0.2 mol or less, relative to 1 mol of the RAFT agent.

[0073] In the polymerization reaction by the RAFT method, the reaction temperature is preferably 40° C. or higher and 100° C. or lower, more preferably 45° C. or higher and 90° C. or lower, and even more preferably 50° C. or higher and 80° C. or lower. A reaction temperature of 40° C. or higher is preferred in that the polymerization reaction can proceed smoothly. A reaction temperature of 100° C. or lower is preferred in that side reactions can be suppressed and restrictions on the polymerization initiators and solvents that can be used are relaxed.

[0074] In the NMP method, a specific alkoxyamine compound having a nitroxide is used as a living radical polymerization initiator, and polymerization proceeds via the nitroxide radical derived from the living radical polymerization initiator. In producing the block copolymer (A), the type of nitroxide radical is not particularly limited, and commercially available nitroxide polymerization initiators can be used. From the viewpoint of polymerization controllability when polymerizing a monomer containing an acrylate, it is preferable to use a compound represented by the following formula (3) as the nitroxide compound: (In formula (3), R ８ represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and R ９ represents an alkyl group having 1 to 2 carbon atoms or a nitrile group, and R １０ Ha-(CH ２ ) r-, r represents an integer of 0 to 2, R １１ and R １２ Each of R independently represents an alkyl group having 1 to 4 carbon atoms. １１ may be the same or different, and multiple R １２ may be the same or different.)

[0075] The nitroxide compound represented by formula (3) undergoes primary dissociation upon heating at approximately 70 to 80°C and undergoes an addition reaction with a vinyl monomer. In this case, a polyfunctional polymerization precursor can be obtained by adding the nitroxide compound to a vinyl monomer having two or more vinyl groups. The polymerization precursor is then subjected to secondary dissociation under heating, resulting in living polymerization of the vinyl monomer. In this case, the polymerization precursor has two or more active sites in its molecule, allowing for the production of a polymer with a narrower molecular weight distribution. In terms of the ease of efficiently obtaining block copolymer (A), it is preferable to use a bifunctional polymerization precursor having two active sites in its molecule. The amount of the nitroxide compound used is adjusted appropriately depending on the type of monomer and nitroxide compound, among other factors.

[0076] When the block copolymer (A) is produced by the NMP method, polymerization may be carried out by adding 0.001 to 0.2 moles of a nitroxide radical represented by the following formula (4) relative to 1 mole of the nitroxide compound represented by the above formula (3). (In formula (4), R １３ and R １４ Each of R independently represents an alkyl group having 1 to 4 carbon atoms. １３ may be the same or different, and multiple R １４ may be the same or different.)

[0077] Adding 0.001 moles or more of the nitroxide radical represented by formula (4) above can shorten the time it takes for the nitroxide radical concentration to reach a steady state. This allows for more precise control of the polymerization, which is advantageous in that it allows for the production of a polymer with a narrower molecular weight distribution. On the other hand, if the amount of nitroxide radical added is too large, the polymerization may not proceed. The amount of nitroxide radical added per mole of nitroxide compound is more preferably in the range of 0.01 to 0.5 moles, and even more preferably in the range of 0.05 to 0.2 moles.

[0078] The reaction temperature in the NMP method is preferably 50° C. or higher and 140° C. or lower, more preferably 60° C. or higher and 130° C. or lower, and even more preferably 70° C. or higher and 120° C. or lower. By setting the reaction temperature to 50° C. or higher, the polymerization reaction can proceed smoothly. Furthermore, by setting the reaction temperature to 140° C. or lower, side reactions such as radical chain transfer tend to be suppressed.

[0079] In the ATRP method, a polymerization reaction is generally carried out using an organic halide as a polymerization initiator and a transition metal complex as a catalyst. The organic halide used as the polymerization initiator may be a monofunctional compound or a bifunctional or higher functional compound. In terms of efficiently obtaining the block copolymer (A), it is preferable to use a bifunctional compound. As the type of halogen, bromides and chlorides are preferred. The reaction temperature in the ATRP method is preferably 20°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower. A reaction temperature of 20°C or higher is preferred in that the polymerization reaction can proceed smoothly.

[0080] For example, when a (CDC) triblock copolymer consisting of polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C) is obtained by living radical polymerization, the target block copolymer may be obtained by sequentially polymerizing each block. In this case, first, in the first polymerization step, the constituent monomers of polymer block (C) are polymerized to obtain polymer block (C), and then, in the second polymerization step, the constituent monomers of (meth)acrylic polymer block (D) are polymerized to obtain (meth)acrylic polymer block (D). Furthermore, in the third polymerization step, the constituent monomers of polymer block (C) are polymerized. This allows the (CDC) triblock copolymer to be obtained. As the polymerization initiator, it is preferable to use the above-mentioned monofunctional polymerization initiator or polymerization precursor.

[0081] Furthermore, when a (CDC) triblock copolymer is produced using a bifunctional polymerization initiator or polymerization precursor and the two-stage polymerization process shown below, the target product can be obtained more efficiently. First, in the first polymerization process, the constituent monomers of the polymer block (C) are polymerized to obtain the polymer block (C), and then in the second polymerization process, the constituent monomers of the (meth)acrylic polymer block (D) are polymerized. This allows the production of a (CDC) triblock copolymer. This method simplifies the process compared to when each block is produced by sequentially polymerizing it.

[0082] The polymerization of the block copolymer (A) may be carried out in the presence of a chain transfer agent, if necessary. Known chain transfer agents can be used. Specific examples include alkylthiol compounds having an alkyl group having 2 to 20 carbon atoms, such as ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-hexanethiol, 2-hexanethiol, 2-butylbutane-1-thiol, 1,1-dimethyl-1-pentanethiol, 1-dodecanethiol, tert-tetradecanethiol, 1-hexadecanethiol, and 1-octadecanethiol, as well as mercaptoacetic acid, mercaptopropionic acid, and 2-mercaptoethanol. One or more of these can be used as the chain transfer agent.

[0083] When producing the block copolymer (A), a polymerization solvent known in living radical polymerization can be used.Specific examples include aromatic compounds such as benzene, toluene, xylene, and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone compounds such as acetone and methyl ethyl ketone; dimethylformamide, acetonitrile, dimethyl sulfoxide, alcohol, and water.In addition, bulk polymerization or the like may be used without using a polymerization solvent.

[0084] From the viewpoint of ensuring sufficient adhesiveness of the pressure-sensitive adhesive layer obtained using the composition, the content of block copolymer (A) in the composition is preferably 70% by mass or more, based on the total amount of polymers contained in the composition, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the total amount of polymers contained in the composition.

[0085] <Other Components> The present composition may contain only the block copolymer (A), or may further contain, as necessary, various components (hereinafter also referred to as "other components") such as polymers other than the block copolymer (A), additives, solvents, etc. The other components that may be blended in the present composition are described below.

[0086] Vinyl Polymer (B) The present composition may further contain, together with the block copolymer (A), a vinyl polymer (hereinafter also referred to as "vinyl polymer (B)") having a glass transition temperature (Tg) of 30°C or higher and 200°C or lower and a number average molecular weight (Mn) of 500 or higher and 10,000 or lower. By forming a pressure-sensitive adhesive layer using a pressure-sensitive adhesive composition containing such a vinyl polymer (B) together with the block copolymer (A), it is possible to cause partial segregation of the vinyl polymer (B) in the surface portion of the pressure-sensitive adhesive layer. This allows the Tg of the surface portion of the pressure-sensitive adhesive layer to be sufficiently high, further improving the hot water washability of the pressure-sensitive adhesive layer and enhancing the adhesion when bonding flexible adherends together.

[0087] When the Tg of the vinyl polymer (B) is 30°C or higher, when a pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition, the Tg of the surface layer of the pressure-sensitive adhesive layer can be increased, thereby ensuring sufficient hot water washability and adhesiveness. On the other hand, due to restrictions on raw material monomers, the Tg of the vinyl polymer (B) is generally 200°C or lower. The Tg of the vinyl polymer (B) is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, still more preferably 70°C or higher, and even more preferably 75°C or higher. From the viewpoint of ensuring the flexibility of the pressure-sensitive adhesive layer, the upper limit of the Tg of the vinyl polymer (B) is preferably 150°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower.

[0088] The preferred range of Tg of the vinyl polymer (B) can be determined by appropriately combining the above-mentioned upper and lower limits of Tg. The range of Tg of the vinyl polymer (B) is preferably 40°C or higher and 150°C or lower, more preferably 40°C or higher and 130°C or lower, even more preferably 50°C or higher and 120°C or lower, and still more preferably 60°C or higher and 110°C or lower.

[0089] Various radically polymerizable vinyl monomers can be used as the monomer constituting the vinyl polymer (B). Examples of such vinyl monomers include the same compounds as those exemplified as the constituent monomers of the block copolymer (A). Among these, it is preferable that the vinyl polymer (B) contains a structural unit derived from a hydrocarbon-based vinyl monomer, in terms of having suitable compatibility with the block copolymer (A). Specific examples of hydrocarbon-based vinyl monomers include (meth)acrylic acid alkyl esters, aliphatic cyclic esters of (meth)acrylic acid, aromatic esters of (meth)acrylic acid, and aromatic vinyl compounds. These compounds may be used alone or in combination of two or more.

[0090] In the vinyl polymer (B), the content of structural units derived from hydrocarbon vinyl monomers is preferably in the range of 30% by mass or more and 100% by mass or less, based on all structural units contained in the vinyl polymer (B), more preferably 50% by mass or more, even more preferably 70% by mass or more, and still more preferably 80% by mass or more, based on all structural units contained in the vinyl polymer (B).

[0091] In producing the vinyl polymer (B), an aliphatic cyclic vinyl monomer can be preferably used, since it can relatively increase Tg and enhance the effect of improving hot water washability. The aliphatic cyclic vinyl monomer is preferably an aliphatic cyclic ester of (meth)acrylic acid, and specific examples thereof include the same compounds as the aliphatic cyclic ester of (meth)acrylic acid exemplified in the description of the block copolymer (A).

[0092] In the vinyl polymer (B), the content of structural units derived from alicyclic vinyl monomers is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, based on the total structural units contained in the vinyl polymer (B). The upper limit of the content of structural units derived from alicyclic vinyl monomers is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, based on the total structural units contained in the vinyl polymer (B). The content range of structural units derived from alicyclic vinyl monomers is preferably 1% by mass or more to 90% by mass or less, more preferably 10% by mass or more to 80% by mass or less, and even more preferably 15% by mass or more to 70% by mass or less.

[0093] Among the above, at least one selected from the group consisting of tert-butyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclohexyl (meth)acrylate and adamantyl (meth)acrylate is preferably used as the monomer constituting the vinyl polymer (B), since this allows the Tg of the vinyl polymer (B) to be set high, the vinyl polymer (B) is likely to segregate at the surface when a pressure-sensitive adhesive layer is formed, and good heat resistance tends to be obtained.

[0094] The Mn of the vinyl polymer (B) is preferably 500 or more and 10,000 or less. By setting the Mn of the vinyl polymer (B) to 10,000 or less, sufficient segregation of the vinyl polymer (B) occurs in the pressure-sensitive adhesive layer, and the effects of improving washing resistance and adhesiveness can be sufficiently obtained. In addition, compatibility with the (meth)acrylic polymer (A) can be sufficiently ensured. By setting the Mn of the vinyl polymer (B) to 500 or more, the amounts of polymerization initiator and chain transfer agent used during polymer production can be appropriate, and a decrease in productivity can be avoided.

[0095] The Mn of the vinyl polymer (B) is more preferably 1,000 or more, even more preferably 1,500 or more, still more preferably 2,000 or more, and even more preferably 3,000 or more. The upper limit of the Mn of the vinyl polymer (B) is more preferably 9,500 or less, even more preferably 9,000 or less, still more preferably 7,000 or less, and even more preferably 5,000 or less. The Mn of the vinyl polymer (B) is more preferably in the range of 1,000 or more to 9,500 or less, even more preferably 1,000 or more to 9,000 or less, still more preferably 1,500 or more to 7,000 or less, and even more preferably 2,000 or more to 5,000 or less.

[0096] In the vinyl polymer (B), the molecular weight distribution (Mw / Mn), which is the ratio of Mw to Mn, is preferably 3.0 or less, since good adhesive strength is easily obtained. Mw / Mn is more preferably 2.5 or less, and even more preferably 2.0 or less. The lower limit of Mw / Mn of the vinyl polymer (B) is not particularly limited, and is 1.0 or more.

[0097] The vinyl polymer (B) is not particularly limited in its production method and can be obtained by a known production method, such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization, by polymerizing the above-mentioned monomers.

[0098] When a vinyl polymer (B) is blended into the pressure-sensitive adhesive composition, the content of the vinyl polymer (B) is preferably in the range of 0.5 to 15 parts by mass, calculated as solids, per 100 parts by mass of the block copolymer (A). When the content of the vinyl polymer (B) is 0.5 parts by mass or more, a sufficient amount of the vinyl polymer (B) is present in the surface layer portion of the pressure-sensitive adhesive layer, thereby enabling the effects of improving hot water washability and adhesiveness to be fully achieved. Furthermore, when the content of the vinyl polymer (B) is 15 parts by mass or less, the flexibility of the pressure-sensitive adhesive layer can be maintained at a high level, and the adhesiveness and transparency can be maintained at a high level. From this perspective, the lower limit of the content of the vinyl polymer (B) is more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the block copolymer (A). The upper limit of the content of the vinyl polymer (B) is more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the block copolymer (A).

[0099] When the composition contains a vinyl polymer (B), a preferred range of the content of the vinyl polymer (B) can be determined by appropriately combining the above-mentioned upper and lower limits of the content of the vinyl polymer (B). Specifically, the content of the vinyl polymer (B) is more preferably 0.5 to 10 parts by mass, even more preferably 0.5 to 5 parts by mass, and still more preferably 1 to 5 parts by mass, per 100 parts by mass of the block copolymer (A).

[0100] Crosslinking Agent When the block copolymer (A) has a crosslinkable functional group, a crosslinking agent capable of reacting with the crosslinkable functional group may be blended into the PSA composition, thereby further improving the hot water washability of the PSA layer and further improving the kickback resistance and adhesion when flexible adherends are bonded together.

[0101] Examples of the crosslinking agent (curing agent) include an epoxy-based crosslinking agent having two or more glycidyl groups, an isocyanate-based crosslinking agent having two or more isocyanate groups, an aziridine-based crosslinking agent having two or more aziridinyl groups, an oxazoline-based crosslinking agent having an oxazoline group, a metal chelate compound, a butylated melamine compound, etc. Among these, at least one selected from the group consisting of an epoxy-based crosslinking agent, an isocyanate-based crosslinking agent, and an aziridine-based crosslinking agent is preferred in terms of ease of adjusting the cohesive strength and adhesiveness of the pressure-sensitive adhesive layer, and an isocyanate-based crosslinking agent is preferred in terms of being able to form a pressure-sensitive adhesive layer that is excellent in hot water washability and cohesive strength.

[0102] Specific examples of the crosslinking agent include epoxy-based crosslinking agents, such as polyfunctional glycidyl compounds as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and trimethylolpropane polyglycidyl ether.

[0103] Examples of isocyanate crosslinking agents include aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and tolidine diisocyanate (TODI); hexamethylene diisocyanate (HDI), and lysine diisocyanate; alicyclic isocyanate compounds such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H12MDI); and modified isocyanate compounds such as urethane-modified compounds, dimers, trimers, carbodiimide-modified compounds, urea-modified compounds, isocyanurate-modified compounds, oxazolidone-modified compounds, and isocyanate-terminated prepolymers.

[0104] Examples of the aziridine crosslinking agent include 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridyl urea, ethylene bis-(2-aziridinyl propionate), 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris(2-aziridinyl propionate).

[0105] When a crosslinking agent is blended into the composition, the content of the crosslinking agent in the composition is not particularly limited. The content of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 2 parts by mass, per 100 parts by mass of the content of block copolymer (A). By setting the content of the crosslinking agent within the above range, it is possible to sufficiently obtain the effects of improving hot water washability, kickback resistance, and adhesiveness due to the formation of a crosslinked structure, while ensuring the flexibility of the pressure-sensitive adhesive layer.

[0106] Silane Coupling Agent The present composition may further contain a silane coupling agent. A pressure-sensitive adhesive composition containing a silane coupling agent in addition to the block copolymer (A) can provide a pressure-sensitive adhesive layer with even better resistance to hot water washing. Examples of the silane coupling agent include silane coupling agents having one or more functional groups such as an epoxy group, a (meth)acryloyl group, an amino group, a vinyl group, a thiol group, an isocyanate group, or a blocked isocyanate group.

[0107] Specific examples of the silane coupling agent include silane coupling agents having an epoxy group, such as oxiranyl group-containing silane coupling agents, such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 8-glycidoxyoctyltriethoxysilane; and oxetanyl group-containing silane coupling agents, such as 2-(3,4-oxetanylcyclohexyl)ethyltrimethoxysilane, 3-oxetanylpropyltrimethoxysilane, 3-oxetanylpropylmethyldiethoxysilane, 3-oxetanylpropyltriethoxysilane, and 8-oxetanyloctyltriethoxysilane.

[0108] Specific examples of silane coupling agents having a (meth)acryloyl group include 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 6-(meth)acryloyloxyhexyltrimethoxysilane, and 8-(meth)acryloyloxyoctyltrimethoxysilane.

[0109] Specific examples of silane coupling agents having an amino group include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-(3-cyclohexylamino)propyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane.

[0110] Specific examples of the silane coupling agent having a thiol group include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

[0111] Specific examples of silane coupling agents having a vinyl group include vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, vinyl(trimethoxysilyl) ether, vinyl(methyldiethoxysilyl) ether, and vinyl(triethoxysilyl) ether.

[0112] Specific examples of silane coupling agents having an isocyanate group or a blocked isocyanate group include isocyanatoalkyltrialkoxysilane compounds such as isocyanatomethyltrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 6-isocyanatohexyltrimethoxysilane, 8-isocyanatooctyltrimethoxysilane, isocyanatomethyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, 6-isocyanatohexyltriethoxysilane, and 8-isocyanatooctyltriethoxysilane; isocyanatomethylmethyldimethoxysilane, 3-isocyanatopropylmethyldimethoxysilane, 6-isocyanatohexylmethyldimethoxysilane, 8-isocyanatooctylmethyldimethoxysilane, isocyanatomethylmethyldiethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, 6-isocyanatohexylmethyldiethoxysilane, isocyanatoalkyl monoalkyl dialkoxysilane compounds such as isocyanatomethyl dimethyl methoxysilane, 3-isocyanatopropyl dimethyl methoxysilane, 6-isocyanatohexyl dimethyl methoxysilane, 8-isocyanatooctyl dimethyl methoxysilane, isocyanatomethyl dimethyl ethoxysilane, 3-isocyanatopropyl dimethyl ethoxysilane, 6-isocyanatohexyl dimethyl ethoxysilane, and isocyanatooctyl dimethyl ethoxysilane; isocyanatoalkyl trialkoxysilane compounds, blocked isocyanatoalkyl alkoxysilane compounds in which the isocyanate group of an isocyanatoalkyl monoalkyl dialkoxysilane compound or an isocyanatoalkyl dialkyl alkoxysilane compound is protected; and the like.

[0113] Regarding the blocked isocyanatoalkylalkoxysilane compound, the protecting agent for protecting the isocyanate group is not particularly limited, and known compounds can be used as appropriate. Examples of protecting agents include alcohols (ethanol, etc.), caprolactams, dimethylpyrazole, and methyl ethyl ketone oxime. Commercially available blocked isocyanatoalkylalkoxysilane compounds can also be used. Commercially available blocked isocyanatoalkylalkoxysilane compounds include Shin-Etsu Silicone X-12-1195, X-12-1293, and X-12-1308ES (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0114] Of the silane coupling agents blended in the present composition, those having at least one selected from the group consisting of an epoxy group, a (meth)acryloyl group, an isocyanate group, and a blocked isocyanate group are particularly preferred, as they have a high effect of improving the hot water washability of the PSA layer, and those having at least one selected from the group consisting of an isocyanate group and a blocked isocyanate group are more preferred.

[0115] When a silane coupling agent is blended in the composition, the content of the silane coupling agent in the composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the content of block copolymer (A).Furthermore, the content of the silane coupling agent is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the content of block copolymer (A).By making the content of the silane coupling agent within the above range, the addition of the silane coupling agent can sufficiently obtain the effect of improving hot water washability and adhesiveness while ensuring the flexibility of the pressure-sensitive adhesive layer.

[0116] Modified olefin polymer or diene polymer A modified olefin polymer or diene polymer (hereinafter also referred to as "modified (E)") is a substance obtained by chemically modifying an olefin polymer or a diene polymer, and contains a structure or functional group different from the unsaturated hydrocarbon unit in the same molecule. Hereinafter, a modified olefin polymer will also be referred to as a "modified olefin polymer," and a modified diene polymer will also be referred to as a "modified diene polymer."

[0117] It is believed that the pressure-sensitive adhesive layer formed from the present composition containing the (meth)acrylic polymer (A) and the modified polymer (E) is in a phase-separated state in the surface layer portion of the pressure-sensitive adhesive layer due to phase separation between the (meth)acrylic polymer (A) and the modified polymer (E) that occurs during the process of forming the pressure-sensitive adhesive layer. Furthermore, it is believed that the phase separation between the (meth)acrylic polymer (A) and the modified polymer (E) in the surface layer portion of the pressure-sensitive adhesive layer results in a well-balanced adhesive performance between the (meth)acrylic polymer (A) and the modified polymer (E). This is believed to have improved adhesion to adherends and washing resistance.

[0118] Examples of the olefin-based polymer or diene-based polymer include polymers containing structural units derived from at least one monomer selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms. Specific examples include homopolymers of α-olefins, conjugated dienes, or non-conjugated dienes having 2 to 20 carbon atoms, and copolymers of two or more monomers selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms.

[0119] Specific examples of α-olefins having 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 4-methyl-1-hexene, 1-octene, 4,4-dimethyl-1-hexene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, etc. Specific examples of conjugated or non-conjugated dienes having 3 to 20 carbon atoms include 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 1,5-hexadiene, ethylidenenorbornene, dicyclopentadiene, etc.

[0120] The olefin-based polymer is preferably a polymer containing structural units derived from α-olefins having 2 to 20 carbon atoms. In the olefin-based polymer, the proportion of structural units derived from α-olefins having 2 to 20 carbon atoms is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and even more preferably 50% by mass or more, based on all structural units constituting the olefin-based polymer. The α-olefins used in the synthesis of the olefin-based polymer may be one type or two or more types.

[0121] The diene polymer is preferably a polymer containing structural units derived from conjugated dienes having 3 to 10 carbon atoms. In the diene polymer, the proportion of structural units derived from α-olefins having 3 to 10 carbon atoms is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on all structural units constituting the diene polymer. Note that the conjugated dienes used in the synthesis of the diene polymer may be one type only, or two or more types.

[0122] The olefin polymer or diene polymer constituting the modified product (E) may be copolymerized with other unsaturated monomers in addition to the above-mentioned monomers. Examples of such unsaturated monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half esters or half amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-aconitic acid; carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate; oligomers of these unsaturated compounds having an unsaturated bond at a terminal; and styrenes such as styrene and α-methylstyrene.

[0123] Examples of olefin polymers or diene polymers copolymerized with other unsaturated monomers include ethylene / ethyl acrylate copolymers, ethylene / vinyl acetate copolymers, styrene / butadiene copolymers, and styrene / isoprene copolymers. Furthermore, hydrogenated products of styrene / butadiene copolymers, styrene / isoprene copolymers, and the like can also be used as diene polymers. When a copolymer is used, a random copolymer, a block copolymer, or a graft copolymer can be appropriately selected.

[0124] Preferred examples of the olefin polymer include polypropylene, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / ethylene / 1-octene copolymer. Of the above, the olefin polymer is preferably polypropylene or a propylene copolymer.

[0125] Commercially available olefin polymers can also be used. Specific examples thereof include the "L-MODU" series manufactured by Idemitsu Kosan Co., Ltd., the "REXtac" series manufactured by LLC, the "Vestoplast" series manufactured by Evonik, the "Eastoflex" series and the "Aerafin" series manufactured by Eastman, the "Tafmer" series manufactured by Mitsui Chemicals, Inc., the "Prime TPO" series manufactured by Prime Polymer, the "Versify" series manufactured by Dow Chemical Company, the "Vistamaxx" series and the "Linxar" series manufactured by ExxonMobil, the "Licocene" series manufactured by Clariant, and the "Adflex" series manufactured by Basell.

[0126] Preferred examples of the diene polymer include styrene / butadiene diblock copolymers, styrene / isoprene diblock copolymers, styrene / butadiene / styrene triblock copolymers, styrene / isoprene / styrene triblock copolymers, and hydrogenated products thereof. Among the above diene polymers, styrene / butadiene / styrene triblock copolymers or hydrogenated products thereof are preferred. When a hydrogenated modified diene polymer is blended in the composition, the modified diene polymer may be one obtained by modifying a diene polymer after hydrogenation, or one obtained by hydrogenating a modified diene polymer.

[0127] Examples of the type of modification include acid modification, chlorination, (meth)acrylic acid ester modification (hereinafter also referred to as "acrylic modification"), carbodiimide modification, urea modification, and imine modification. Furthermore, the modified product (E) may be one in which two or more types of modifications have been sequentially performed. Specific examples of the modified product (E) to which two or more types of modifications have been performed include acid-modified chlorinated polymers, acrylic-modified chlorinated polymers, and urethane-modified chlorinated polymers. From the viewpoints of a high effect of improving adhesion and ease of availability, the modified product (E) is preferably at least one selected from the group consisting of chlorinated polymers, acid-modified polymers, acid-modified chlorinated polymers, acrylic-modified polymers, and acrylic-modified chlorinated polymers.

[0128] The acid-modified polymer and the acid-modified chlorinated polymer are preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic anhydrides (hereinafter also referred to as "specific acid modifier"). Such modified polymer (E) can be obtained, for example, by graft copolymerizing the specific acid modifier onto an olefin-based polymer, adding the specific acid modifier to an olefin-based polymer or a diene-based polymer, or copolymerizing a monomer as the specific acid modifier. The modification reaction can be carried out using a conventionally known method. When graft copolymerizing the specific acid modifier onto an olefin-based polymer, for example, a method in which the specific acid modifier is added to an olefin-based polymer melted using an extruder and copolymerized; a method in which the specific acid modifier is added to an olefin-based polymer dissolved in a solvent and copolymerized; a method in which the specific acid modifier is added to an olefin-based polymer in an aqueous suspension and copolymerized; etc. The modified site in the modified polymer (E) may be one end of the molecular chain, both ends of the molecular chain, or in the middle of the molecular chain, or multiple of these locations.

[0129] Examples of the specific acid modifier used in the modification reaction include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half esters or half amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-aconitic acid; and carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride. Among these, at least one selected from the group consisting of unsaturated monocarboxylic acids and carboxylic acid anhydrides is preferred, at least one selected from the group consisting of (meth)acrylic acid, maleic acid, and maleic anhydride is more preferred, and maleic anhydride is even more preferred.

[0130] The acid-modified olefin polymer and the acid-modified chlorinated olefin polymer may be further modified with a (meth)acrylic acid ester in addition to the acid modifier. That is, in this specification, the term "acid-modified olefin polymer" is intended to encompass an acid-modified olefin polymer that has been acrylic-modified. Furthermore, the term "acid-modified chlorinated olefin polymer" is intended to encompass an acid-modified chlorinated olefin polymer that has been acrylic-modified. Therefore, acid-modified olefin polymers include ethylene-acrylic acid ester-maleic anhydride 3D copolymers, ethylene-methacrylic acid ester-maleic anhydride 3D copolymers, propylene-acrylic acid ester-maleic anhydride 3D copolymers, and propylene-methacrylic acid ester-maleic anhydride 3D copolymers. Specific examples of (meth)acrylic acid esters for acrylic modification are the same as the compounds exemplified in the description of the acrylic-modified olefin polymers.

[0131] The acrylic-modified olefin polymer and the acrylic-modified chlorinated olefin polymer may be a polymer in which an olefin polymer is modified with a (meth)acrylic acid ester. The (meth)acrylic acid ester may preferably be at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid cycloalkyl esters. Specific examples thereof include the (meth)acrylic acid alkyl esters and aliphatic cyclic esters of (meth)acrylic acid exemplified in the description of the (meth)acrylic polymer (A). Alternatively, a (meth)acrylic acid alkyl ester having an alkyl group having 13 or more carbon atoms, such as tridecyl (meth)acrylate or stearyl (meth)acrylate, may be used.

[0132] The chlorinated polymer, acid-modified polymer, acid-modified chlorinated polymer, acrylic-modified polymer, and acrylic-modified chlorinated polymer may be modified in combination with other modifiers, such as functional group-containing (meth)acrylic acid alkyl esters, aromatic vinyl compounds, and cyclohexyl vinyl ether.

[0133] Among these, the modified product (E) is preferably at least one selected from the group consisting of a chlorinated polymer, an acid-modified polymer, and an acid-modified chlorinated polymer, more preferably at least one selected from the group consisting of a chlorinated polymer, a maleic anhydride-modified polymer, and a maleic anhydride-modified chlorinated polymer, and even more preferably a maleic anhydride-modified polymer, in terms of the fact that the difference in SP value with the (meth)acrylic polymer (A) becomes larger, thereby facilitating phase separation from the (meth)acrylic polymer (A), thereby enhancing the effect of improving adhesion, and in terms of easy availability.

[0134] When the modified substance (E) is blended in the composition, the content of the modified substance (E) in the composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the (meth)acrylic polymer (A). The content of the modified substance (E) is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the (meth)acrylic polymer (A). By setting the content of the modified substance (E) within the above range, the addition of the modified substance (E) can sufficiently improve the washing resistance while ensuring the flexibility of the pressure-sensitive adhesive layer.

[0135] The present composition may further contain fine particles. By blending fine particles together with the block copolymer (A) to form a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer with further improved kickback properties can be obtained. This makes it possible to prevent waviness or peeling at the bonded portions due to expansion and contraction, even when flexible adherends are bonded together.

[0136] The microparticles are not particularly limited as long as the effects of the present disclosure can be obtained. The microparticles incorporated into the composition may be inorganic or organic. Examples of inorganic materials constituting the inorganic microparticles include silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, titanium dioxide, talc, glass (soda glass, float glass, etc.), or a combination of two or more of these. Examples of organic materials constituting the organic microparticles include (meth)acrylic resins, polystyrene resins, polyurethane resins, polyolefin resins (e.g., polyethylene, polypropylene, etc.), silicone resins, epoxy resins, nylon resins, or a combination of two or more of these. Examples of (meth)acrylic resins include homopolymers of methyl methacrylate, copolymers of methyl methacrylate with other monomers (e.g., styrene, vinyl acetate, methyl acrylate, ethyl acrylate, etc.), and crosslinked polymers of these homopolymers or copolymers. The microparticles may be hot-melt powders.

[0137] Among these, organic fine particles are preferred because they have a high effect of improving the kickback property of the pressure-sensitive adhesive layer, and fine particles formed using one or more selected from the group consisting of (meth)acrylic resin, polyurethane resin, and nylon resin are more preferred.In addition, when the fine particles are formed using one or more resins selected from the group consisting of (meth)acrylic resin, polyurethane resin, and nylon resin, the resin may be a hot-melt resin.The shape of the fine particles is not particularly limited, but spherical ones can be preferably used.

[0138] The volume average particle diameter of the microparticles can be appropriately selected depending on the thickness of the pressure-sensitive adhesive layer, etc. Specifically, the volume average particle diameter of the microparticles is preferably 5 to 200 μm, more preferably 5 to 100 μm, and even more preferably 10 to 70 μm. When the volume average particle diameter of the microparticles is within the above range, the kickback properties of the pressure-sensitive adhesive layer can be sufficiently improved. The volume average particle diameter of the microparticles is a value measured using a laser diffraction / scattering particle size distribution analyzer.

[0139] When microparticles are blended in the composition, the content of the microparticles in the composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the content of block copolymer (A).Furthermore, the content of the microparticles is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less, relative to 100 parts by mass of the content of block copolymer (A).By making the content of the microparticles within the above range, the effect of improving kickback properties by adding the microparticles can be sufficiently obtained, while ensuring the flexibility and adhesiveness of the pressure-sensitive adhesive layer.

[0140] Tackifier The composition may contain a tackifier. Examples of tackifiers include rosin derivatives such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene-based resins based on terpene phenol resins, α-pinene, β-pinene, or limonene; coumarone-indene resins, hydrogenated aromatic copolymers, and phenolic resins. One type of tackifier may be used alone, or two or more types may be used in combination. The content of the tackifier is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to the content of the block copolymer (A).

[0141] The composition may contain a plasticizer. Examples of the plasticizer include phthalates such as di-n-butyl phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-decyl phthalate; adipates such as bis(2-ethylhexyl) adipate and di-n-octyl adipate; sebacates; azelaates; paraffins such as chlorinated paraffin; glycols such as polypropylene glycol; epoxy-modified vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; phosphates such as trioctyl phosphate and triphenyl phosphate; phosphites such as triphenyl phosphite; ester oligomers such as esters of adipic acid and 1,3-butylene glycol; low-molecular-weight polymers such as low-molecular-weight polybutene, low-molecular-weight polyisobutylene, and low-molecular-weight polyisoprene; and oils such as process oil and naphthenic oil. The content of the plasticizer is preferably 0 to 20% by mass, more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, based on the content of the block copolymer (A).

[0142] Examples of additives that may be blended into the composition include the above-mentioned vinyl polymer (B), crosslinking agent, silane coupling agent, modified olefin polymer, modified diene polymer, fine particles, tackifier, and plasticizer, as well as, for example, antioxidant, ultraviolet absorber, antiaging agent, flame retardant, mildew inhibitor, filler, colorant, and antistatic agent. The content of the additives can be appropriately set depending on the various additives within a range that does not impair the effects of the present disclosure.

[0143] Solvent: The present composition may be a solution-type PSA composition in which the block copolymer (A) and optional components are dissolved in a solvent. When the present composition is a solution-type PSA composition, the solvent used to prepare the PSA composition may be an organic solvent capable of dissolving the block copolymer (A). Specific examples of organic solvents include aprotic polar solvents, phenolic solvents, alcoholic solvents, ester solvents, ketone solvents, ether solvents, and hydrocarbon solvents. The organic solvent may be one of these solvents or a mixture of two or more of these solvents. For example, a solvent-type PSA composition can be obtained by dissolving the block copolymer (A) in one or more organic solvents selected from the group consisting of ethyl acetate, butyl acetate, ethyl methyl ketone, and toluene. Furthermore, when preparing the present composition, an aqueous medium capable of dispersing the block copolymer (A) may be used as the solvent, and the block copolymer (A) may be dispersed in the aqueous medium, thereby forming the present composition into an emulsion-type PSA composition.

[0144] The present composition may contain a block copolymer (A), and there are no particular limitations on the form of the composition. For example, in addition to the block copolymer (A), the composition may contain a monofunctional and / or polyfunctional (meth)acrylic monomer, a photopolymerization initiator, and the like, thereby constituting a so-called syrup-type photocurable pressure-sensitive adhesive composition that is cured by active energy rays such as ultraviolet rays. In the case of a photocurable pressure-sensitive adhesive composition, the composition may contain a solvent such as an organic solvent, but is usually prepared and used as a solventless type that does not contain a solvent. Alternatively, the present composition may be a solid or semi-solid pressure-sensitive adhesive composition containing the block copolymer (A) and components blended as necessary.

[0145] In the case of a solution-type PSA composition, the solids concentration in the composition (i.e., the ratio of the mass of components other than the solvent in the PSA composition to the total mass of the PSA composition) is not particularly limited, but is preferably 1 to 70 mass%. When the solids concentration is 1 mass% or more, a PSA layer with sufficient thickness can be formed. When the solids concentration is 70 mass% or less, good coatability can be ensured and a PSA layer with uniform thickness can be easily formed. The solids concentration in the PSA composition is more preferably 5 to 60 mass%, and even more preferably 10 to 50 mass%.

[0146] <Production of Pressure-Sensitive Adhesive Layer> The pressure-sensitive adhesive layer can be formed by applying the composition to a separator or the like and drying as necessary. Resin films made of various resin materials can be used as the separator. Examples of such resin materials include polyester resins such as polyethylene terephthalate, polyethersulfone resins, acetate resins, polycarbonate resins, and polyolefin resins. For example, to form a pressure-sensitive adhesive layer using a liquid pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition is applied to a separator by a known coating method, and the solvent is removed by a drying treatment such as heating. The heating temperature and heating time for forming the pressure-sensitive adhesive layer may be any temperature and duration that can remove the solvent, and can be appropriately set depending on the type of solvent, solids concentration, and the like.

[0147] <Characteristics of the Pressure-Sensitive Adhesive Layer> Storage Modulus The pressure-sensitive adhesive layer formed using the present composition has a storage modulus (G') at 23°C of 1.0 MPa or less. If the storage modulus at 23°C exceeds 1.0 MPa, it will be difficult to ensure sufficient flexibility and texture at the bonded portions when bonding flexible adherends such as fiber fabrics together. From the viewpoint of ensuring sufficient flexibility and texture at the bonded portions, the storage modulus of the pressure-sensitive adhesive layer at 23°C is preferably 0.8 MPa or less, more preferably 0.6 MPa or less, even more preferably 0.5 MPa or less, and even more preferably 0.4 MPa or less.

[0148] In this specification, the storage modulus of the pressure-sensitive adhesive layer at 23°C is a value obtained by measuring the shear viscoelasticity of an 800 µm thick pressure-sensitive adhesive layer under conditions of a heating rate of 2°C / min, a strain of 0.1%, and a measurement frequency of 1 Hz. Details of the method for measuring the storage modulus are as described in the Examples below. The storage modulus of the pressure-sensitive adhesive layer can be adjusted as desired by adjusting the composition and degree of crosslinking of the (meth)acrylic polymer block (D), the Tg of the vinyl polymer (B), the Tg and amount of additives (such as a tackifier), etc. For example, the storage modulus of the pressure-sensitive adhesive layer can be adjusted by using one or more of alkyl (meth)acrylates having an alkyl group with 1 to 4 carbon atoms and alkoxyalkyl (meth)acrylates having an alkoxy group with 1 to 4 carbon atoms as constituent monomers of the (meth)acrylic polymer block (D), and adjusting the type and amount of these monomers used.

[0149] Gel Fraction The gel fraction of the pressure-sensitive adhesive layer made of the composition is preferably 90% or less. By setting the gel fraction to 90% or less, both adhesion and flexibility can be achieved when bonding flexible adherends together. From this perspective, the gel fraction of the pressure-sensitive adhesive layer is more preferably 80% or less, even more preferably 70% or less, and particularly preferably 60% or less. In this specification, the gel fraction of the pressure-sensitive adhesive layer is the ratio of the mass (W2) of the pressure-sensitive adhesive layer remaining after solvent immersion to the initial mass (W1) of the pressure-sensitive adhesive layer (= (W2 / W1) × 100 [%]). Details will be described in accordance with the measurement method described in the Examples below.

[0150] <<Adhesive Sheet>> The adhesive sheet of the present disclosure can be produced by forming an adhesive layer on a support such as a separator using the composition of the present disclosure. The method for forming the adhesive layer can be selected appropriately depending on the type of adhesive composition. For example, in the case of a solution-type adhesive composition, the adhesive composition can be applied to a support by a known coating method, and the solvent can be removed preferably by a drying treatment such as heating. The heating temperature and heating time for forming the adhesive layer may be any temperature and time that can remove the solvent, and can be appropriately set depending on the type of solvent contained in the adhesive composition, the solids concentration of the adhesive composition, etc.

[0151] The pressure-sensitive adhesive sheet may be a so-called substrateless type in which a pressure-sensitive adhesive layer is sandwiched between two separators with different peel strengths. Alternatively, one of the adherends may serve as a support when bonding two adherends together. The shape of the pressure-sensitive adhesive sheet is not particularly limited and may be selected appropriately depending on the intended use. For example, the pressure-sensitive adhesive sheet may be in the form of a sheet, a roll, or a tape, or may be cut into strips. The pressure-sensitive adhesive sheet may also have any shape depending on the intended use. The thickness of the pressure-sensitive adhesive layer may be selected appropriately depending on the object to be bonded, the area and shape of the bonded portion, etc. For example, when used to bond flexible adherends together, the thickness of the pressure-sensitive adhesive layer is typically 2 to 200 μm. In addition, to achieve the desired thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, multiple pressure-sensitive adhesive layers may be laminated together.

[0152] <Products> The product of the present disclosure comprises two adherends bonded together via a pressure-sensitive adhesive layer formed from the composition described above. Specifically, the product of the present disclosure comprises a first adherend, a second adherend, and a pressure-sensitive adhesive layer, with the first and second adherends bonded together via the pressure-sensitive adhesive layer formed from the composition described above. The pressure-sensitive adhesive layer formed from the composition has high resistance to hot water washing. Furthermore, even when flexible adherends are bonded together, the pressure-sensitive adhesive layer exhibits excellent adhesion and kickback properties, while maintaining the flexibility and texture of the adherends at the bonded area. Therefore, the composition is particularly suitable as a pressure-sensitive adhesive composition for bonding flexible adherends such as fiber fabrics, resin films, and natural leather. Furthermore, the pressure-sensitive adhesive layer formed from the composition is resistant to yellowing due to nitrogen oxides and is resistant to loss of adhesive strength due to moist heat. Therefore, even when applied to adherends that come into contact with the body, such as clothing and fashion accessories, it is possible to obtain highly durable products that are resistant to deterioration.

[0153] The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer that can maintain the flexibility and texture of fabrics even when attached to fibers, and that has high adhesiveness. Therefore, in bonding flexible adherends together (i.e., bonding a flexible first adherend to a flexible second adherend), the composition is particularly useful when one or both of the first and second adherends are textile fabrics for clothing, including clothing accessories (e.g., woven fabrics, knitted fabrics, nonwoven fabrics, lace, synthetic leather, artificial leather, fur, etc.). When one of the adherends to be bonded is a textile fabric, the other adherend may be either a textile fabric or a flexible adherend other than a textile fabric (e.g., a resin film, natural leather, etc.).

[0154] The fiber fabric used is not particularly limited, and fiber fabrics used for clothing, such as synthetic fibers such as polyester, polyamide, polyurethane, and acrylic fibers; regenerated fibers such as rayon and cupra; semi-synthetic fibers such as acetate; and natural fibers such as cotton, linen, and wool, can be used as appropriate. The surface of the fiber fabric may be subjected to a water-repellent treatment or the like. The products manufactured using the composition are also not particularly limited. For example, the composition can be used as an adhesive in the manufacture of a wide range of clothing, such as everyday Western and Japanese clothing, ethnic clothing, underwear (e.g., seamless lingerie products and innerwear), outerwear, tops, bottoms, outdoor gear, workwear, uniforms, formal wear, swimwear, sportswear, socks, hats, shoes, and the like, as well as for handicrafts.

[0155] To obtain the product of the present disclosure, first, adherends are bonded together so that they contact each other via the pressure-sensitive adhesive layer formed from the present composition. Subsequently, temporary pressure-bonding is performed as necessary to obtain a laminate of adherend / pressure-sensitive adhesive layer / adherend. The laminate is then heated (preferably by thermocompression bonding) to obtain a product in which the adherends are bonded together via the pressure-sensitive adhesive layer formed from the present composition.

[0156] When adhering adherends by thermocompression bonding, the pressure during bonding may be appropriately set so as to obtain the desired adhesive strength. The heating temperature is preferably equal to or lower than the heat resistance temperature of the adherends used. According to the present composition, when at least one of the adherends is a fibrous fabric, even if the polymer in the pressure-sensitive adhesive composition penetrates into the mesh of the fibrous fabric during thermocompression bonding, the adhesive portion remains flexible and the adherends can be bonded with high strength.

[0157] The present disclosure will be specifically described below using examples. However, the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified. The polymers used in each example were analyzed using the following methods.

[0158] <Molecular weight measurement> Using a gel permeation chromatograph (model "HLC-8320", manufactured by Tosoh Corporation), the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were obtained under the following conditions. The molecular weight distribution (Mw / Mn) was calculated from the obtained values. Measurement conditions Column: 4 columns of TSKgel SuperMultiporeHZ-M manufactured by Tosoh Corporation Column temperature: 40°C Eluent: Tetrahydrofuran Detector: RI Flow rate: 600 μL / min

[0159] <Monomer composition ratio (mass %) of polymer> The monomer composition ratio (mass %) of the polymer was calculated from the charged amount and the amount of monomer consumed measured by gas chromatography (GC). The GC measurement was carried out under the following conditions: GC: Agilent Technologies (7820A GC System), detector: FID, column: 100% dimethylsiloxane (CP-Sil 5CB), column length: 30 m, column inner diameter: 0.32 mm, calculation method: internal standard method

[0160] <Glass transition temperature (Tg) of polymer> The glass transition temperature (Tg) of the polymer was determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter and the tangent at the inflection point. The heat flux curve was obtained under the following conditions: approximately 10 mg of a sample was cooled to -50°C, held for 5 minutes, then heated to 250°C at 10°C / min, subsequently cooled to -50°C, held for 5 minutes, and then heated to 250°C at 10°C / min. Measurement equipment: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0161] 1. Synthesis of Acrylic Polymers [Synthesis Example 1] (Synthesis of Polymer Block C-1 and Polymer A-1) Dibenzyl trithiocarbonate (hereinafter also referred to as "DBTTC") (0.692 parts by mass) as a RAFT agent, 2,2'-azobis(2-methylbutyronitrile) (hereinafter also referred to as "ABN-E") (0.174 parts by mass) as a polymerization initiator, n-butyl acrylate (hereinafter also referred to as "BA") (55.0 parts by mass) and N-phenylmaleimide (hereinafter also referred to as "PhMI") (45.0 parts by mass) as monomers, and acetonitrile (232.5 parts by mass) as a solvent were charged into a four-neck flask equipped with a stirrer and a thermometer, and the mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostatic bath at 70°C. After 6 hours, the mixture was cooled to room temperature to terminate the reaction. The polymerization solution was purified by reprecipitation from methanol and vacuum dried to obtain polymer block C-1. The resulting polymer block C-1 had an Mn of 20,900, an Mw of 27,000, and an Mw / Mn of 1.3. The glass transition temperature Tg of the polymer block C-1 was 55°C. Next, a 1 L flask equipped with a stirrer and a thermometer was charged with the resulting polymer block C-1 (10.0 parts by mass), ABN-E (0.0191 parts by mass) as a polymerization initiator, BA (62.0 parts by mass), 2-methoxyethyl acrylate (hereinafter also referred to as "MEA") (28.5 parts by mass), and 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA") (9.5 parts by mass) as monomers, and acetonitrile (70.8 parts by mass) as a solvent. The mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a constant temperature bath at 70°C. After 6 hours, the mixture was cooled to room temperature, and ethyl acetate was added to adjust the solids concentration to 30% by mass, yielding a pressure-sensitive adhesive solution containing a (CDC) triblock copolymer A-1 having a polymer block (C) and a (meth)acrylic polymer block (D). The resulting polymer A-1 had an Mn of 147,000, an Mw of 465,000, and an Mw / Mn of 3.2. The glass transition temperature Tg of polymer A-1 was −38° C.Polymer A-1 was synthesized using polymer block C-1 and monomers (BA, MEA, HEA), but polymerization was carried out in the same manner as above, except that the same amount of DBTTC as used in the synthesis of polymer block C-1 was used instead of polymer block C-1. The glass transition temperature Tg of the polymer obtained (this is the glass transition temperature of polymer block D-1) was −38° C. The analytical results of polymer A-1 are shown in Table 2.

[0162] In Table 2, "C / D block ratio" represents the ratio (mass ratio) of polymer block (C) to (meth)acrylic polymer block (D) in the acrylic polymer. Using the amount of polymer block (C) charged during the synthesis of the acrylic polymer, the amount of each monomer charged, and the GC reaction rate (=monomer consumption rate determined by GC measurement), the C / D block ratio was expressed as "Q1 / Σ(Q2×γ)." Here, Q1 represents the amount (parts by mass) of polymer block (C) used in the synthesis of the acrylic polymer, Q2 represents the amount (parts by mass) of each monomer charged, and γ represents the GC reaction rate of each monomer.

[0163] Synthesis Examples 2 to 6 (Synthesis of Polymer Blocks C-2 to C-6 and Polymers A-2 to A-6) Polymer blocks C-2 to C-6 were obtained and PSA solutions containing polymers A-2 to A-6 were also obtained by the same procedure as in Synthesis Example 1, except that the types and amounts of raw materials charged into the flask were changed as shown in Table 1. In Synthesis Example 5, the reaction time for polymerization to obtain polymer block C-5 was changed from 6 hours to 3 hours. The glass transition temperatures of polymer blocks D-2 to D-6 were also determined in the same manner as for polymer D-1. The analytical results of each polymer are shown in Table 2.

[0164] Synthesis Example 7 Synthesis of Polymer A-7 A four-neck flask equipped with a stirrer and a thermometer was charged with BA (17.0 parts by mass), MEA (78.0 parts by mass), HEA (5 parts by mass), and ethyl acetate (150.0 parts). The mixture was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixture was raised to 75°C. A polymerization initiator, 2,2'-azobis(2,4-dimethylbutyronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65", hereinafter also referred to as "V-65") (0.0191 parts by mass), was charged thereto, and polymerization was carried out for 5 hours. Ethyl acetate was added so that the solids concentration became 30%, to obtain a pressure-sensitive adhesive solution containing Polymer A-7. Polymer A-7 had an Mn of 92,000, an Mw of 800,000, and an Mw / Mn of 8.7. The Tg was -35°C. The analytical results of Polymer A-7 are shown in Table 2.

[0165]

[0166]

[0167] The abbreviations of the monomers in Tables 1 and 2 are as follows: PhMI: N-phenylmaleimide BA: butyl acrylate EA: ethyl acrylate HA: 2-ethylhexyl acrylate HEA: 2-hydroxyethyl acrylate St: styrene MEA: 2-methoxyethyl acrylate AA: acrylic acid

[0168] 2. Synthesis of Vinyl Polymers [Synthesis Example 8] (Synthesis of Polymer B-1) A four-neck flask equipped with a stirrer and a thermometer was charged with a mixed solution consisting of butyl acetate (200 parts by mass) and dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-601", hereinafter also referred to as "V-601") (6.2 parts by mass), and the mixed solution was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixed solution was raised to 90°C. Separately, a mixed solution consisting of methyl methacrylate (hereinafter also referred to as "MMA") (100 parts by mass), isobornyl methacrylate (hereinafter also referred to as "IBXMA") (109 parts by mass), V-601 (20 parts by mass), and butyl acetate (90 parts by mass) was added dropwise from a dropping funnel into the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixed solution of methanol (4,800 parts by mass) and distilled water (1,200 parts by mass), thereby isolating the vinyl polymer in the polymerization solution to obtain Polymer B-1. The monomer composition of the obtained Polymer B-1 was calculated from the charged amounts and the monomer consumption amounts measured by GC, and was found to be 50% by mass of MMA and 50% by mass of IBXMA, with Mw of 3,080, Mn of 5,340, and Mw / Mn of 1.73. The Tg was 88°C. The composition and analytical results of Polymer B-1 are shown in Table 3.

[0169] Synthesis Example 9 Synthesis of Polymer B-2 A four-necked flask equipped with a stirrer and a thermometer was charged with a mixed solution consisting of butyl acetate (200 parts by mass) and V-601 (0.9 parts by mass). The mixed solution was thoroughly degassed by bubbling nitrogen gas through it, and the internal temperature of the mixed solution was raised to 90 ° C. Separately, a mixed solution consisting of MMA (165 parts by mass), IBXMA (44 parts by mass), V-601 (17 parts by mass), and butyl acetate (90 parts by mass) was added dropwise from a dropping funnel into the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixed solution consisting of methanol (4,800 parts by mass) and distilled water (1,200 parts by mass), and the vinyl polymer in the polymerization solution was isolated to obtain Polymer B-2. The monomer composition of the obtained polymer B-2 was calculated from the charged amounts and the monomer consumption amounts measured by GC, and was found to be 80% by mass of MMA and 20% by mass of IBXMA, with Mw of 6,700, Mn of 4,370, and Mw / Mn of 1.53. The Tg was 108° C. The composition and analytical results of polymer B-2 are shown in Table 3.

[0170]

[0171] The abbreviations of the monomers in Table 3 are as follows: MMA: methyl methacrylate IBXMA: isobornyl methacrylate

[0172] 3. Production of Pressure-Sensitive Adhesive Layer and Pressure-Sensitive Adhesive Film [Example 1] The pressure-sensitive adhesive solution containing Polymer A-1 obtained in Synthesis Example 1 was used as a pressure-sensitive adhesive composition and was applied to a 50 μm thick polyethylene terephthalate (hereinafter referred to as "PET") separator so that the thickness after drying would be 100 μm. The pressure-sensitive adhesive composition was dried at 100°C for 6 minutes to remove volatile components, thereby forming a pressure-sensitive adhesive layer. A 38 μm thick PET separator with a different peel strength from the separator to which the pressure-sensitive adhesive composition was applied was attached to the surface of the pressure-sensitive adhesive layer, thereby obtaining a pressure-sensitive adhesive film sample with a double-sided separator.

[0173] [Examples 2 and 3, Comparative Examples 1 to 3 and 5] For Examples 2 and 3, Comparative Examples 1 to 3 and 5, pressure-sensitive adhesive compositions were prepared based on the compositions shown in Tables 4 and 56, and pressure-sensitive adhesive film samples were obtained in the same manner as in Example 1.

[0174] Example 4 The adhesive solution containing polymer A-1 obtained in Synthesis Example 1 was mixed with a polymer (B-1) solution containing polymer B-1 (2 parts by mass) dissolved in acetonitrile to prepare a solution containing polymer A-1 (100 parts by mass) and polymer B-1 (2 parts by mass) with a solids concentration of 30% by mass, which was used as an adhesive composition. This adhesive composition was applied to a 50 μm thick PET separator so that the thickness after drying would be 100 μm. The adhesive composition was dried at 100°C for 6 minutes to remove volatile components, forming an adhesive layer. A 38 μm thick PET separator with a different peel strength from the separator to which the adhesive composition was applied was attached to the surface of the adhesive layer to obtain an adhesive film sample with a double-sided separator.

[0175] [Examples 5 and 6, Comparative Examples 4 and 6] For Examples 5 and 6, and Comparative Examples 4 and 6, PSA film samples were obtained in the same manner as in Example 4 based on the compositions shown in Tables 4 and 6.

[0176] Example 7 A polymer (B-1) solution with a solids concentration of 30% by mass, prepared by dissolving polymer B-1 (2 parts by mass) in acetonitrile, was mixed with the adhesive solution containing polymer A-1 obtained in Synthesis Example 1 to prepare a solution with a solids concentration of 30% by mass containing polymer A-1 (100 parts by mass) and polymer B-1 (2 parts by mass). An isocyanate group-containing silane coupling agent, "Shin-Etsu Silicone KBE-9007N" (1.0 part by mass), manufactured by Shin-Etsu Chemical Co., Ltd., was added to the solution as an additive to obtain an adhesive composition. This adhesive composition was applied to a 50 μm thick PET separator so that the thickness after drying would be 100 μm. The adhesive composition was dried at 100°C for 6 minutes to remove volatile components from the adhesive composition, thereby forming an adhesive layer. A 38 μm thick PET separator with a different peel strength from the separator to which the adhesive composition was applied was attached to the surface of the adhesive layer to obtain an adhesive film sample with a double-sided separator.

[0177] [Examples 8 to 17, Comparative Example 7] For Examples 8 to 17 and Comparative Example 7, PSA film samples were obtained using the compositions shown in Tables 4, 5, and 6, in the same manner as in Example 7. For Examples 13, 14, 17, and Comparative Example 7, which contained the isocyanate-based crosslinking agent "Takenate D-110N" manufactured by Mitsui Chemicals, Inc., a 38 μm-thick PET separator was attached to the film, and then the film was left to stand at 40° C. for 5 days for aging (aging), thereby obtaining PSA film samples with double-sided separators. In Tables 4, 5, and 6, the amount of isocyanate-based crosslinking agent (Takenate D-110N) represents the solid content.

[0178] Example 18 A solution of polymer (B-1) with a solids concentration of 30% by mass, prepared by dissolving polymer B-1 (2 parts by mass) in acetonitrile, was mixed with the adhesive solution containing polymer A-1 obtained in Synthesis Example 1 to prepare a solution containing polymer A-1 (100 parts by mass) and polymer B-1 (2 parts by mass). A solution with a solids concentration of 10% by mass, prepared by dissolving maleic anhydride-modified polyolefin "TOYOTAC PMA-TE" (2.0 parts by mass) manufactured by Toyobo Co., Ltd. as an additive in toluene, was added to the solution to obtain a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was applied to a 50 μm-thick PET separator to a thickness of 50 μm after drying. The pressure-sensitive adhesive composition was dried at 80°C for 4 minutes to remove volatile components from the pressure-sensitive adhesive composition, forming a pressure-sensitive adhesive layer. A 38 μm thick PET separator having a different peel strength from the separator coated with the adhesive composition was attached to the surface of the adhesive layer to obtain a double-sided separator-attached adhesive film sample.

[0179] Example 19 A 30% solids solution of polymer (B-1) prepared by dissolving polymer B-1 (2 parts by mass) in acetonitrile was mixed with the adhesive solution containing polymer A-1 obtained in Synthesis Example 1 to prepare a 30% solids solution containing polymer A-1 (100 parts by mass) and polymer B-1 (2 parts by mass). A 10% solids solution prepared by dissolving a maleic anhydride-modified hydrogenated styrene-butadiene-styrene block copolymer (Tuftec M1913, manufactured by Asahi Kasei Corporation) (2.0 parts by mass) in toluene was added to the adhesive solution to obtain an adhesive composition. This adhesive composition was applied to a 50 μm-thick PET separator to a dry thickness of 50 μm. The adhesive composition was dried at 80°C for 4 minutes to remove volatile components from the adhesive composition, forming an adhesive layer. A 38 μm thick PET separator having a different peel strength from the separator coated with the adhesive composition was attached to the surface of the adhesive layer to obtain a double-sided separator-attached adhesive film sample.

[0180] Example 20 The adhesive solution containing polymer A-1 obtained in Synthesis Example 1 was mixed with a polymer (B-1) solution having a solids concentration of 30% by mass, prepared by dissolving polymer B-1 (2 parts by mass) in acetonitrile, to prepare a solution having a solids concentration of 30% by mass containing polymer A-1 (100 parts by mass) and polymer B-1 (2 parts by mass). A solution having a solids concentration of 10% by mass, prepared by dissolving additives "Shin-Etsu Silicone KBE-9007N" (1.0 part by mass), DTF Premium Hot Melt Powder "DTF-PWD02-09K" (2.0 parts by mass), "Takenate D-110N" (0.4 parts by mass as solids), and "Tuftec M1913" (2.0 parts by mass) in toluene, was then mixed therewith to obtain an adhesive composition. This adhesive composition was applied to a 50 μm thick PET separator to a thickness of 50 μm after drying. The pressure-sensitive adhesive composition was dried at 80° C. for 4 minutes to remove volatile components in the pressure-sensitive adhesive composition, thereby forming a pressure-sensitive adhesive layer. A 38 μm thick PET separator having a different peel strength from the separator to which the pressure-sensitive adhesive composition was applied was attached to the surface of the pressure-sensitive adhesive layer, and then the resulting film was left to stand at 40° C. for 5 days for aging, thereby obtaining a pressure-sensitive adhesive film sample with a double-sided separator.

[0181] 4. Evaluation Various measurements and evaluations were carried out using the pressure-sensitive adhesive film samples and a commercially available urethane hot-melt adhesive film (thickness 100 μm) according to the methods described below. The results are shown in Tables 4, 5 and 6.

[0182] <Gel Fraction> 0.2 g of adhesive was collected from the adhesive film sample, and the initial mass of the adhesive was weighed. The collected adhesive was immersed in 50 g of ethyl acetate and allowed to stand at room temperature for 16 hours. Thereafter, it was filtered through a 200-mesh wire netting, and the residue remaining on the mesh was dried at 80°C for 3 hours and then weighed. The gel fraction (%) was calculated from the initial mass and the mass of the residue.

[0183] <Storage modulus G' at room temperature (23°C)> A pressure-sensitive adhesive layer of a 100 μm thick pressure-sensitive adhesive film sample or a urethane hot melt adhesive film was laminated to prepare a test piece with a pressure-sensitive adhesive layer of 800 μm thick. This test piece was punched into a circle with a diameter of 1 cm, and the dynamic viscoelasticity was measured at a strain of 0.1% and a frequency of 1 Hz using a shear viscoelasticity measuring device Physica MCR301 (manufactured by Anton Paar) while raising the temperature from -50°C to 150°C at a rate of 2°C / min, and the storage modulus G' at 23°C was read. Note that a parallel plate with a diameter of 8 mm was used for the measurement.

[0184] <Evaluation of Fabric Peel Strength> The adhesive layer of the adhesive film sample or the urethane hot melt adhesive film was sandwiched between the backsides of two nylon / polyurethane knitted fabrics and pressed with a low-temperature iron for 3 seconds to temporarily bond them. The temporarily pressed fabric laminate was then heat pressed at 150°C and 1 kg / cm. ２ The test pieces were then pressed together for 10 seconds, and then cut into 25 mm widths along the longitudinal direction to prepare test pieces. The T-peel strength of the pressed test pieces was measured using an INSTRON 5566A tensile tester with a thermostatic chamber (manufactured by Instron Japan) at a measurement temperature of 23°C, a test piece width of 25 mm, and a peel rate of 300 mm / min. The T-peel strength was also measured in the same manner using a water-repellent polyester woven fabric instead of the nylon / polyurethane knitted fabric.

[0185] <Touch test: texture> Using the fabric laminate used in the evaluation of the peel strength of the nylon / polyurethane knit fabric, the bending stiffness of the bonded area was evaluated according to the following criteria: ○: Soft ×: Feels stiff

[0186] <Stress Increase During Elongation> A fabric laminate prepared in the same manner as in the evaluation of the peel strength of nylon / polyurethane knit fabric was prepared and elongated using an INSTRON 5566A tensile tester with a thermostatic bath (manufactured by Instron Japan) with a chuck distance of 50 mm at a measurement temperature of 23°C, a test piece width of 25 mm, and a peel rate of 100 mm / min. The stress at 100% elongation was measured and evaluated according to the following criteria: ○: The stress increase rate was less than 50% compared to the stress when only two fabric sheets were elongated to 100%; ×: The stress increase rate was 50% or more compared to the stress when only two fabric sheets were elongated to 100%.

[0187] <Kickback Properties> A fabric laminate was prepared in the same manner as in the evaluation of the peel strength of nylon / polyurethane knit fabric, except that the test piece width was 10 mm. The fabric laminate was set in an INSTRON 5566A tensile tester with a thermostatic chamber (manufactured by Instron Japan) so that the chuck distance was 50 mm. The fabric laminate was stretched at a measurement temperature of 23°C, a test piece width of 10 mm, and a peel rate of 300 mm / min until the chuck distance reached 100 mm, and this stretched state was maintained for 1 minute. The fabric laminate was then returned to its original position at 300 mm / min until the chuck distance reached 50 mm. The fabric laminate was removed from the tester, and 5 minutes after removal, the length of the stretched portion of the fabric laminate was measured and evaluated according to the following criteria: ⊚: The length of the stretched portion was less than 55 mm; ◯: The length of the stretched portion was 55 mm or more but less than 60 mm; Δ: The length of the stretched portion was 60 mm or more but less than 65 mm; ×: The length of the stretched portion was 65 mm or more.

[0188] <Yellowing test due to nitrogen oxides> Two 15 cm x 10 cm pieces of white polyester knit fabric were placed on top of each other with their front surfaces facing outward. A 100 μm thick, 5 cm x 10 cm adhesive film sample or a urethane hot melt adhesive film was placed in the center of the two overlapping fabrics and sandwiched between the two fabrics to form a fabric laminate. This fabric laminate was pressed with a low-temperature iron for 3 seconds to temporarily bond the back surfaces of the fabrics together. The fabric laminate after temporary bonding was then heat pressed at 150°C and 1 kg / cm. ２ Using this test sample, a nitrogen oxide fastness test (3 cycles) was carried out in accordance with JIS L 0855, and discoloration at the bonded area was evaluated using a discoloration gray scale.

[0189] <Artificial Sweat Degradation Test> An artificial sweat degradation test was conducted according to the test method ATTS2102:1992 established by the Textile Technology Research Society (ATTS). A test specimen, in which the back surfaces of two white polyester knit fabrics were bonded together using the adhesive layer of an adhesive film sample or a urethane hot-melt adhesive film, was placed in an artificial sweat atmosphere and subjected to a humid heat load at 70°C and 90% RH for 10 days. The test specimens before and after the load were cut into 25 mm widths, and the peel strength was measured using the same method as the fabric peel strength measurement method described above, and the peel strength retention after the humid heat load was calculated.

[0190] <40°C washing test> The center portions of two 15 cm x 10 cm nylon / polyurethane knit fabrics were sandwiched between the adhesive layer of a 100 μm thick, 5 cm x 10 cm adhesive film sample or a urethane hot melt adhesive film, and the fabrics were pressed together with a low-temperature iron for 3 seconds to temporarily bond the back surfaces together. The temporarily pressed fabric laminate was then heat pressed at 150°C and 1 kg / cm. ２ The test samples were washed 50 times in warm water at 40°C according to the household washing machine method (JIS L 1930 C4N), then laid flat to dry, and peeling from the bonded edge was evaluated according to the following criteria: ◎: Peeling from the bonded edge was less than 1 mm ○: Peeling from the bonded edge was 1 mm or more but less than 3 mm △: Peeling from the bonded edge was 3 mm or more but less than 10 mm ×: Peeling from the bonded edge was 10 mm or more

[0191] <60°C washing test> Test samples were prepared in the same manner as in the 40°C washing test. According to the washer method (JIS L 1096 F-2 method), the test samples were washed 10 times in warm water at 60°C using a cylinder-type washing machine, and then tumble dried. Peeling from the edge of the adhesive portion was evaluated using the same criteria as in the 40°C washing test.

[0192]

[0193]

[0194]

[0195] The abbreviations of the additives in Tables 4, 5 and 6 are as follows: KBE-9007N: Isocyanate group-containing silane coupling agent, "Shin-Etsu Silicone KBE-9007N", manufactured by Shin-Etsu Chemical Co., Ltd. KBM-403: Epoxy group-containing silane coupling agent, "Shin-Etsu Silicone KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd. KBM-503: (meth)acryloyl group-containing silane coupling agent, "Shin-Etsu Silicone KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd. KBM-903: Amino group-containing silane coupling agent, "Shin-Etsu Silicone KBM-903", manufactured by Shin-Etsu Chemical Co., Ltd. PMMA microparticles: Crosslinked polymethyl methacrylate spherical microparticles, "Techpolymer MBX-50", manufactured by Sekisui Plastics Co., Ltd., average particle size 50 μm. Hot melt powder: DTF Premium hot melt powder, "DTF-PWD02-09K", manufactured by Europort, average particle size 50 μm. Takenate D-110N: isocyanate-based crosslinking agent, "Takenate D-110N", manufactured by Mitsui Chemicals, Inc. Toyotack PMA-TE: maleic anhydride-modified polyolefin (modified olefin-based polymer), "Toyotack PMA-TE", manufactured by Toyobo Co., Ltd. Tuftec M1913: maleic anhydride-modified hydrogenated styrene-butadiene-styrene block copolymer (modified diene-based polymer), "Tuftec M1913", manufactured by Asahi Kasei Corporation

[0196] As shown in Tables 4, 5, and 6, the PSA compositions of Examples 1 to 20 exhibited high adhesion even to high-density and water-repellent fabrics, and were able to form PSA layers with well-balanced improvements in flexibility and texture at the bonded area, kickback resistance, durability, and hot water washability. Among these, Examples 7 to 9, 12, 14, 16, and 20, which incorporated an isocyanate group-containing silane coupling agent, an epoxy group-containing silane coupling agent, or a (meth)acryloyl group-containing silane coupling agent, exhibited significantly improved hot water washability and adhesion compared to Examples 1 to 3, which did not incorporate a silane coupling agent. The effect of incorporating a silane coupling agent on improving hot water washability and adhesion was particularly significant when an isocyanate group-containing silane coupling agent was used (Examples 7, 12, 14, 16, and 20). Furthermore, Examples 11 to 17 and 20, which incorporated microparticles or a crosslinking agent, exhibited significantly improved kickback resistance. Furthermore, as shown by comparing Examples 4 to 6 with Examples 1 to 3, the warm water washability was further improved by blending the vinyl polymer (B).

[0197] Furthermore, Examples 18 to 20, which contained a modified olefin polymer or a modified diene polymer, showed significantly improved kickback properties, hot water washability, and adhesion properties compared to Example 4, which did not contain a modified olefin polymer or a modified diene polymer.

[0198] In contrast, Comparative Examples 1 to 4, which used a block copolymer with a hard segment Tg of over 90°C, and Comparative Examples 5 to 7, which used non-block (meth)acrylic polymers (Polymers A-4 to A-6) instead of the block copolymer, showed poor adhesion to high-density fabrics and water-repellent fabrics, and were also rated as poor in hot water washability. Comparative Example 8, which used a urethane hot-melt adhesive film, showed poor adhesion to water-repellent fabrics, insufficient texture and flexibility at the bonded locations, and was also rated as poor in kickback resistance and durability.

[0199] From the above results, it became clear that a PSA composition containing a block copolymer (A) having a polymer block (C) having a Tg of 10°C or more and 90°C or less and a (meth)acrylic polymer block (D) having a Tg of -80°C or more and less than 10°C, wherein the polymer block (C) contains a structural unit (U1) and a structural unit (U2), the total content of the structural units (U1) and (U2) being 80 mass% or more based on all the structural units of the polymer block (C), and wherein the PSA layer has a storage modulus at 23°C of 1.0 MPa or less, can form a PSA layer that has excellent hot water washability while maintaining good adhesion and kickback properties in addition to flexibility and texture at the bonded portion.

[0200] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

Claims

1. A pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer, comprising: a block copolymer (A) having a polymer block (C) having a glass transition temperature of 10°C or more and 90°C or less; and a (meth)acrylic polymer block (D) having a glass transition temperature of -80°C or more and less than 10°C; the polymer block (C) comprises a structural unit (U1) derived from an imide group-containing vinyl monomer and a structural unit (U2) derived from a (meth)acrylic monomer, the total content of the structural units (U1) and (U2) being 80 mass% or more based on all structural units of the polymer block (C); and the pressure-sensitive adhesive layer having a storage modulus at 23°C of 1.0 MPa or less.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer block (D) contains structural units derived from a (meth)acrylic ester having a hydrocarbon group having 3 or more carbon atoms in an amount of 20 mass% or more based on the total structural units of the (meth)acrylic polymer block (D).

3. The pressure-sensitive adhesive composition according to claim 1, wherein the structural unit (U2) is a structural unit derived from a compound represented by the following formula (1): CH ２ =CR １ -C(=O)O(R ２ O) ｎ -R ３ ...(1) (In formula (1), R １ represents a hydrogen atom or a methyl group, R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. n represents an integer of 0 to 100.

4. The pressure-sensitive adhesive composition according to claim 1, wherein the content of structural units derived from an aromatic vinyl compound in the polymer block (C) is 10 mass% or less based on the total structural units of the polymer block (C).

5. The pressure-sensitive adhesive composition according to claim 1, wherein the block copolymer (A) comprises a triblock copolymer of polymer block (C)-(meth)acrylic polymer block (D)-polymer block (C).

6. The pressure-sensitive adhesive composition according to claim 1, wherein the block copolymer (A) has a weight average molecular weight of 100,000 or more.

7. The pressure-sensitive adhesive composition according to claim 1, further comprising a silane coupling agent.

8. The pressure-sensitive adhesive composition according to claim 7, wherein the silane coupling agent has at least one group selected from the group consisting of an epoxy group, a (meth)acryloyl group, an isocyanate group, and a blocked isocyanate group.

9. The pressure-sensitive adhesive composition according to claim 1, further comprising a modified olefin polymer or a modified diene polymer.

10. The pressure-sensitive adhesive composition according to claim 9, wherein the modified polymer is at least one selected from the group consisting of a chlorinated polymer, a maleic anhydride modified polymer, and a maleic anhydride modified chlorinated polymer.

11. The pressure-sensitive adhesive composition according to claim 1, further comprising a vinyl polymer (B) (excluding modified olefin polymers or diene polymers) having a glass transition temperature of 30°C or higher and 200°C or lower and a number average molecular weight of 500 or higher and 10,000 or lower.

12. The pressure-sensitive adhesive composition according to claim 11, wherein the vinyl polymer (B) contains structural units derived from an aliphatic cyclic vinyl monomer.

13. The pressure-sensitive adhesive composition according to claim 11, wherein the content of the vinyl polymer (B) is 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the block copolymer (A).

14. The pressure-sensitive adhesive composition according to claim 1, further comprising an isocyanate-based crosslinking agent.

15. The pressure-sensitive adhesive composition according to claim 1, further comprising fine particles.

16. A pressure-sensitive adhesive sheet comprising a support and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 15.

17. A product comprising: a first adherend; a second adherend; and a pressure-sensitive adhesive layer, said first adherend and said second adherend being bonded via said pressure-sensitive adhesive layer, said pressure-sensitive adhesive layer being formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 15.