Adhesive composition, copolymer dispersion, set, adhesive tape, and bonding method

Abstract

This adhesive composition comprises a copolymer (A), a crosslinking agent (B), and an aqueous medium, wherein: the copolymer (A) has a structural unit derived from a monomer (a1), a structural unit derived from a monomer (a2) having a carboxy group, and a structural unit derived from a monomer (a3) having an epoxy group; the monomer (a1) is composed of one or both of alkyl (meth)acrylate having only one ethylenically unsaturated bond and hydrocarbon having only one ethylenically unsaturated bond; the content of the structural unit derived from the monomer (a2) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) in the copolymer (A) is 1.0-12 parts by mass; the content of the structural unit derived from the monomer (a3) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) in the copolymer (A) is 0.10-10 parts by mass; the crosslinking agent (B) contains at least one selected from the group consisting of a polycarbodiimide compound, a polyepoxy compound, and a polyisocyanate compound; and the content of the crosslinking agent (B) with respect to 100 parts by mass of the copolymer (A) is 0.010-10 parts by mass.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, a copolymer dispersion, a set, an adhesive tape, and an adhesion method.

Background Art

[0002] An adhesive tape is a typical application of an adhesive. An adhesive tape has a layer containing an adhesive, that is, an adhesive layer, formed on a substrate, and the adhesive tape is attached to an article, for example, to repair various articles or to fix articles to each other. Further, a double-sided adhesive tape having adhesive layers formed on both sides of a substrate is used in a wide range of applications such as transportation equipment such as automobiles, household appliances, and stationery.

[0003] As a typical manufacturing method of an adhesive tape, a coating liquid in which an adhesive is dissolved or dispersed in a liquid medium is applied onto a substrate and dried, whereby an adhesive layer is formed on the surface of the substrate. Natural rubber-based, synthetic rubber-based, acrylic-based adhesives, etc. are widely used, and in particular, acrylic-based adhesives have a great feature in that they can impart various functionalities. In recent years, much consideration has been given to using water as the liquid medium.

[0004] For example, Patent Document 1 describes a wafer processing tape characterized in that an acrylic resin emulsion adhesive composition obtained by adding a volatile surfactant to an acrylic resin emulsion adhesive polymerized using a reactive surfactant is applied to a substrate film. It is described that the acrylic resin emulsion adhesive is obtained by polymerizing a monomer containing a carboxylic acid-containing vinyl compound. Further, there is an example in which tetramethylol-tri-β-aziridinylpropionate is added to the adhesive composition.

[0005] Patent Document 2 describes a re-peelable adhesive sheet in which an adhesive layer contains adhesive fine particles, a binder, a tackifier, and a crosslinking agent having a carbodiimide group. Further, in Examples and the like, acrylic acid is used as a monomer in the synthesis of the adhesive fine particles.

[0006] Patent Document 3 describes, in Example 1, an aqueous dispersion of an acrylic adhesive containing a copolymer obtained by copolymerizing monomers containing acrylic acid and an epoxy crosslinking agent. Furthermore, in Example 3 and other documents, an aqueous dispersion of an acrylic adhesive containing a copolymer obtained by copolymerizing acrylic acid and a silane coupling agent and an oxazoline crosslinking agent is described.

[0007] Patent Document 4 describes a removable aqueous adhesive composition containing an emulsion obtained by emulsion polymerization of a monomer mixture including an alkyl (meth)acrylate, a carboxyl group-containing unsaturated monomer, a polyfunctional unsaturated monomer, and other unsaturated monomers, and a crosslinking agent. Examples of other unsaturated monomers include monomers having alkoxysilyl groups. Furthermore, it is stated that the crosslinking agent is at least one selected from oxazoline compounds, carbodiimide compounds, epoxy compounds, and aziridine compounds. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 5-171117 [Patent Document 2] Japanese Patent Publication No. 2005-126479 [Patent Document 3] Japanese Patent Publication No. 2013-189645 [Patent Document 4] Japanese Patent Publication No. 2004-256789 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The configurations in Patent Documents 1 and 2 have room for improvement in terms of adhesive strength and holding power under high-temperature conditions.

[0010] The configuration of Example 1 in Patent Document 3, when applied to adhesive tape, has room for improvement in terms of holding power under high-temperature conditions. Furthermore, the configurations of Example 2 and others in Patent Document 3, when applied to adhesive tape, also have room for improvement in terms of adhesive strength and holding power under high-temperature conditions.

[0011] The structure described in Patent Document 4 also has room for improvement in terms of adhesion and retention under high-temperature conditions. Furthermore, while the range of alkoxysilyl groups that can exert a sufficient effect is narrow, the document does not specify how much is needed to achieve that effect. Moreover, in this document, alkoxysilyl groups are merely one of many monomers, one of the various types of monomers exemplified, and their effects are not mentioned at all.

[0012] Therefore, the object of the present invention is to provide an adhesive composition that can form an adhesive layer that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and further possesses high holding power at high temperatures. Another object of the present invention is to provide an adhesive tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and further possesses high holding power at high temperatures. [Means for solving the problem]

[0013] In other words, the present invention provides the following means. [1] An adhesive composition comprising a copolymer (A), a crosslinking agent (B), and an aqueous medium, The copolymer (A) has structural units derived from monomer (a1), structural units derived from monomer (a2) having a carboxyl group, and structural units derived from monomer (a3) ​​having an epoxy group. The monomer (a1) consists of either an alkyl (meth)acrylate having only one ethylenically unsaturated bond, or a hydrocarbon having only one ethylenically unsaturated bond, or both. The content of structural units derived from monomer (a2) in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less. The content of structural units derived from monomer (a3) ​​in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 0.10 parts by mass or more and 10 parts by mass or less. The crosslinking agent (B) comprises one or more selected from the group consisting of polycarbodiimide compounds, polyepoxy compounds, and polyisocyanate compounds. An adhesive composition in which the amount of the crosslinking agent (B) per 100 parts by mass of the copolymer (A) is 0.010 parts by mass or more and 10 parts by mass or less. [2] The adhesive composition according to [1], wherein the copolymer (A) has structural units derived from a monomer (a4) having a hydroxyl group, and the content of structural units derived from monomer (a4) in the copolymer (A) is 0.10 parts by mass or more and 10 parts by mass or less per 100 parts by mass of structural units derived from monomer (a1). [3] The adhesive composition according to [1] or [2], wherein the copolymer (A) has no structural units derived from a compound having a plurality of independent ethylenically unsaturated bonds. [4] The adhesive composition according to any one of [1] to [3], wherein the copolymer (A) contains a total of 90% by mass or more of structural units derived from monomer (a1), structural units derived from monomer (a2), and structural units derived from monomer (a3). [5] The adhesive composition according to any one of [1] to [4], wherein the glass transition temperature of the copolymer (A) is -80°C or higher and 30°C or lower. [6] The adhesive composition according to any one of [1] to [5], wherein the monomer (a1) is an alkyl (meth)acrylate. [7] The adhesive composition according to any one of [1] to [6], wherein the crosslinking agent (B) is a polycarbodiimide compound. [8] The adhesive composition according to [7], wherein the carbodiimide equivalent of the crosslinking agent (B) is 150 or more and 1000 or less. [9] The adhesive composition according to any one of [1] to [6], wherein the crosslinking agent (B) is a polyepoxy compound.

[10] The epoxy equivalent of the crosslinking agent (B) is 70 or more and 700 or less, and the adhesive composition according to [9].

[11] The total content of the copolymer (A) and the crosslinking agent (B) in the non-volatile matter is 50% by mass or more, and the adhesive composition according to any one of [1] to

[10] .

[12] A copolymer dispersion used for preparing the adhesive composition according to any one of [1] to

[11] , comprising a copolymer (A) and an aqueous medium, The copolymer (A) has a structural unit derived from the monomer (a1), a structural unit derived from the monomer (a2) having a carboxy group, and a structural unit derived from the monomer (a3) having an epoxy group, The monomer (a1) consists of either or both of an alkyl (meth)acrylate having only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond, The content of the structural unit derived from the monomer (a2) in the copolymer (A) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less, The content of the structural unit derived from the monomer (a3) in the copolymer (A) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) is 0.10 part by mass or more and 10 parts by mass or less, the copolymer dispersion.

[13] A set used for adjusting the adhesive composition, comprising a copolymer dispersion and a crosslinking agent (B), The copolymer dispersion comprises a copolymer (A) and an aqueous medium, The copolymer (A) has a structural unit derived from the monomer (a1), a structural unit derived from the monomer (a2) having a carboxy group, and a structural unit derived from the monomer (a3) having an epoxy group, The monomer (a1) consists of either or both of an alkyl (meth)acrylate having only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond, In the copolymer (A), the content of the structural unit derived from the monomer (a2) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less. In the copolymer (A), the content of the structural unit derived from the monomer (a3) with respect to 100 parts by mass of the structural unit derived from the monomer (a1) is 0.10 part by mass or more and 10 parts by mass or less. The crosslinking agent (B) contains one or more selected from the group consisting of polycarbodiimide compounds, polyepoxy compounds, and polyisocyanate compounds. A set in which the content of the crosslinking agent (B) with respect to 100 parts by mass of the copolymer (A) is 0.010 part by mass or more and 10 parts by mass or less.

[14] An adhesive tape comprising a base material and an adhesive layer formed on the surface of the base material, The adhesive layer is an adhesive tape containing a cured product of the adhesive composition according to any one of [1] to

[11] .

[15] An adhesion method using the adhesive tape according to

[14] .

[16] A step of applying the adhesive composition according to any one of [1] to

[11] to a base material, A method for producing an adhesive tape, comprising a step of removing an aqueous medium from the adhesive composition applied to the base material to form an adhesive layer. [Advantages of the Invention]

[0014] According to the present invention, it is possible to provide an adhesive composition capable of forming an adhesive layer that exhibits strong adhesive force not only at normal temperature but also at high temperature and further has high holding power at high temperature. In this specification, the adhesive force is defined as "the force generated by the contact between the adhesive surface of the adhesive sheet or adhesive tape and the adherend", and means the force required to peel off the adhered object. In this specification, the holding power is defined as "the force that the adhesive resists displacement when the adhesive sheet or adhesive tape is adhered to the adherend and a static load is applied in the length direction", and represents the strength of the cohesive force of the adhesive layer. Furthermore, according to the present invention, it is possible to provide an adhesive tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that also has high holding power at high temperatures. [Modes for carrying out the invention]

[0015] In the following explanation, unless otherwise specified, "surface" refers to the surface.

[0016] "(Meth)acrylic" is a general term for acrylic and methacrylic, while "(Meth)acrylate" is a general term for acrylate and methacrylate.

[0017] The epoxy group also includes structures that form part of the glycidyl group. For example, glycidyl methacrylate is also considered to have an epoxy group.

[0018] Unless otherwise specified, "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond that exhibits radical polymerization properties.

[0019] In polymers of compounds having ethylenically unsaturated bonds, a structural unit derived from a compound having an ethylenically unsaturated bond is defined as having the same chemical structure in the polymer as the chemical structure of the part of that compound other than the ethylenically unsaturated bond, except for the part corresponding to the ethylenically unsaturated bond. For example, a structural unit derived from acrylic acid has a structure represented as -CH2CH(COOH)- in the polymer.

[0020] In the following explanation, the compound from which a structural unit originates refers to a compound that has the above-described relationship with that structural unit, and does not need to be the same as the monomer used in the actual manufacturing process.

[0021] Furthermore, for structural units having ionic functional groups such as carboxyl groups, unless otherwise specified, they shall be considered structural units derived from the same ionic compound, regardless of whether or not a portion of the functional group is ion-exchanged. For example, the structural unit represented by -CH2-C(CH3)(COONa)- shall also be considered a structural unit derived from methacrylic acid.

[0022] Furthermore, for compounds having multiple independent ethylenically unsaturated bonds, the ethylenically unsaturated bonds may remain as structural units of the polymer. Multiple independent ethylenically unsaturated bonds refer to multiple ethylenically unsaturated bonds that do not form conjugated dienes with each other. For example, a structural unit derived from divinylbenzene may be a structure without ethylenically unsaturated bonds (a form in which the parts corresponding to each ethylenically unsaturated bond are incorporated into the polymer chain), or a structure with one ethylenically unsaturated bond (a form in which only the part corresponding to one of the ethylenically unsaturated bonds is incorporated into the polymer chain).

[0023] Furthermore, in cases where the chemical structure of the monomer and the chemical structure of the polymer do not correspond, such as when a functional group other than the chain corresponding to the ethylenically unsaturated bond is chemically reacted after polymerization to introduce an ester structure or other functional groups, the chemical structure after the reaction shall be used as the basis. For example, when vinyl acetate is polymerized and then saponified, the saponified structural units shall be considered to be derived from vinyl alcohol, not vinyl acetate, based on the chemical structure of the polymer. However, the chemical structure obtained by the chemical reaction of the epoxy group in a structural unit derived from monomer (a3) ​​having an epoxy group after polymerization shall be considered to be derived from monomer (a3) ​​having an epoxy group.

[0024] "Non-volatile content" refers to the components remaining after weighing 1 g of the composition onto a 5 cm diameter aluminum dish and drying it at 1 atmosphere (1013 hPa) in a drying oven at 105°C for 1 hour while circulating air. The composition may be in the form of a solution, dispersion, or slurry, but is not limited to these. "Non-volatile content concentration" is the mass ratio (mass%) of the non-volatile content after drying under the above conditions to the mass (1 g) of the composition before drying.

[0025] In this specification, "adhesive" means a cured product of the adhesive composition, that is, an article obtained by removing water from the adhesive composition and curing it. In one embodiment, the adhesive is obtained by drying the adhesive composition at 100°C for 3 minutes and then curing it by letting it stand at 40°C for 3 days. It is believed that the crosslinking reaction of the adhesive composition is completed during the 3 days of standing at 40°C.

[0026] Furthermore, in this specification, "adhesive composition coated layer" means a layer formed on a substrate or release paper (hereinafter referred to as "substrate, etc.") by removing the aqueous medium from the adhesive composition applied to the substrate, etc. The adhesive layer can be cured to obtain an adhesive layer. In one embodiment, the adhesive layer is obtained by curing the adhesive composition coating layer by leaving it to stand at 40°C for 3 days. The adhesive layer may be formed by curing an adhesive composition coating layer, which has been applied to a release paper, after transferring it to a substrate such as a nonwoven fabric, by leaving it to stand at 40°C for 3 days.

[0027] <1. Adhesive composition> The adhesive composition according to this embodiment comprises a copolymer (A), a crosslinking agent (B), and an aqueous medium. The adhesive composition may also contain other additives.

[0028] [1-1. Copolymer (A)] Copolymer (A) is a polymer of a compound having an ethylenically unsaturated bond. Copolymer (A) includes structural units derived from monomer (a1), structural units derived from monomer (a2) having a carboxyl group, and structural units derived from monomer (a3) ​​having an epoxy group. Furthermore, copolymer (A) preferably contains at least one of the structures derived from monomer (a4) having a hydroxyl group and other compounds such as chain transfer agents (a6), and more preferably both. Copolymer (A) may also contain structural units derived from a compound (a5) that does not fall under any of monomers (a1) to (a4) but has an ethylenically unsaturated bond.

[0029] Furthermore, it is preferable that copolymer (A) does not have structural units derived from compounds having multiple independent ethylenically unsaturated bonds. Examples of compounds having multiple independent ethylenically unsaturated bonds include divinylbenzene and ethylene glycol dimethacrylate.

[0030] [1-1-1. Monomer (a1)] Monomer (a1) consists of either or both structural units derived from alkyl (meth)acrylate and / or structural units derived from hydrocarbons having ethylenically unsaturated bonds. Monomer (a1) has only one ethylenically unsaturated bond. Monomer (a1) preferably contains alkyl (meth)acrylate, and more preferably consists of alkyl (meth)acrylate. Monomer (a1) may contain only one compound or may contain two or more compounds.

[0031] Examples of alkyl (meth)acrylate esters in monomer (a1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobolonyl (meth)acrylate. Among these, methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred because their physical properties are easy to control.

[0032] Examples of hydrocarbons having ethylenically unsaturated bonds include styrene, α-methylstyrene, p-methylstyrene, ethylene, and propylene. Considering the manufacturing cost of copolymer (A), styrene is preferred as the hydrocarbon having ethylenically unsaturated bonds because it readily generates radicals.

[0033] In copolymer (A), the glass transition temperature of copolymer (A) can be adjusted by the type and proportion of structural units derived from monomer (a1). Structural units that lower the glass transition temperature of copolymer (A) include, but are not limited to, structural units derived from 2-ethylhexyl acrylate and structural units derived from butyl acrylate. Structural units that raise the glass transition temperature of copolymer (A) include, but are not limited to, structural units derived from methyl methacrylate and structural units derived from styrene.

[0034] [1-1-2. Monomer (a2)] A monomer (a2) having a carboxyl group has a carboxyl group. In the present invention, a monomer having an epoxy group (i.e., a monomer that falls under the definition of monomer (a3)) and also having a carboxyl group is considered monomer (a3) ​​and not monomer (a2). Some or all of the carboxyl groups may form a salt, but the proportion of salt formation is preferably 10% or less on a mole basis. It is preferable that the compound that becomes monomer (a2) does not have multiple independent ethylenically unsaturated bonds. It is preferable that monomer (a2) is a compound having ethylenically unsaturated bonds and a carboxyl group.

[0035] Preferred compounds having an ethylenically unsaturated bond and a carboxyl group include, for example, α,β-unsaturated mono or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl acrylate oligomer, and 2-acryloyloxyethyl succinic acid; and carboxyl group-containing vinyl compounds such as monohydroxyethyl (meth)acrylate phthalate and monohydroxypropyl (meth)acrylate oxalate; and one or more of these can be used.

[0036] The monomer (a2) may be one compound or two or more compounds. The monomer (a2) preferably contains (meth)acrylic acid, and more preferably consists of (meth)acrylic acid.

[0037] The mechanism by which the use of monomer (a2) having a carboxyl group improves heat resistance is not clear, but the inventors speculate that it is due to the following mechanism. That is, the carboxyl group of the structural unit derived from monomer (a2) reacts with the epoxy group of the structural unit derived from monomer (a3) ​​to form intramolecular crosslinking (internal crosslinking), and / or the carboxyl group of the structural unit derived from monomer (a2) reacts with the functional group of the crosslinking agent (B) described later to help form intermolecular crosslinking (external crosslinking). These crosslinks impart cohesive force to the adhesive layer, thereby improving the heat resistance of the adhesive layer.

[0038] [1-1-3. Monomer (a3)] The monomer (a3) ​​has an epoxy group. Preferably, the monomer (a3) ​​does not have multiple independent ethylenically unsaturated bonds.

[0039] The monomer (a3) ​​is a compound having an epoxy group, and is preferably a compound having an ethylenically unsaturated bond and an epoxy group. The monomer (a3) ​​is preferably a (meth)acrylate having an epoxy group. Examples of compounds having an ethylenically unsaturated bond and an epoxy group include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, glycidyl (meth)allyl ether, 3,4-epoxycyclohexyl (meth)acrylate, and other epoxy group-containing (meth)acrylates. Among these, glycidyl (meth)acrylate is more preferred as the monomer (a3), and glycidyl methacrylate is even more preferred.

[0040] [1-1-4. Monomers (a4)] Monomer (a4) has a hydroxyl group. In the present invention, a monomer having an epoxy group (i.e., a monomer that falls under the definition of monomer (a3)) and also having a hydroxyl group is considered monomer (a3) ​​and not monomer (a4).

[0041] The high-temperature retention force of the adhesive layer is further improved by the copolymer (A) having structural units derived from monomer (a4). Although the mechanism is not clear, the inventors speculate that it is due to the following mechanism: The hydroxyl group of the structural unit derived from monomer (a4) reacts with the epoxy group of the structural unit derived from monomer (a3) ​​to form an intramolecular crosslink (internal crosslink), and / or the hydroxyl group of the structural unit derived from monomer (a4) reacts with the functional group of the crosslinking agent (B) described later to help form an intermolecular crosslink (external crosslink), and these crosslinks are presumed to further improve the high-temperature retention force of the adhesive layer. It is preferable that monomer (a4) does not have multiple independent ethylenically unsaturated bonds. It is preferable that monomer (a4) is a compound having an ethylenically unsaturated bond and a hydroxyl group.

[0042] The monomer (a4) is preferably a (meth)acrylate having a hydroxyl group, and more preferably an alkyl (meth)acrylate having a hydroxyl group, i.e., a hydroxyalkyl (meth)acrylate. Examples of compounds from which monomer (a4) is derived include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate is more preferred, and 2-hydroxyethyl methacrylate is even more preferred. Monomer (a4) may contain only one compound or two or more compounds.

[0043] [1-1-5. Monomer (a5)] Monomer (a5) is a compound having an ethylenically unsaturated bond and is not a compound that falls under any of monomers (a1) to (a4).

[0044] Examples of monomers (a5) include alkylamino(meth)acrylates such as N,N-dimethylaminoethyl(meth)acrylate and N,N-dimethylaminopropyl(meth)acrylate; vinyl ester compounds such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; conjugated diolefin compounds such as butadiene, isoprene, and chloroprene; amineimide group-containing vinyl compounds such as 1,1,1-trimethylaminemethacrylimide; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N-methyl Examples include (meth)acrylamide compounds such as methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide; sulfo group-containing α,β-ethylenically unsaturated compounds such as allyl sulfonate and sodium p-styrenesulfonate; radical polymerizable ultraviolet absorbers such as 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole; and radical polymerizable light stabilizers such as 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate.

[0045] [1-1-6. Other Compounds (a6)] In this specification, "other compounds (a6)" refers to compounds that are the origin of structures or structural units constituting copolymer (A), excluding structural units derived from monomers (a1) to (a5). Examples of such compounds (a6) include polymerization initiators and chain transfer agents used in the synthesis process of copolymer (A). Unlike monomers (a1) to (a5), the above-mentioned correspondence relationship between the structure of the polymerization initiator, chain transfer agent, etc., and the other compounds (a6) in copolymer (A) does not necessarily apply to other compounds (a6).

[0046] In this embodiment, the content of structural units derived from each monomer, chain transfer agent, and other compounds can be calculated using the blending amounts of each compound added for the production of copolymer (A). [1-1-7. Content of each structural unit] The copolymer (A) preferably contains 90% by mass or more of structural units derived from monomer (a1), monomer (a2), and monomer (a3) ​​in total, more preferably 95% by mass or more, and even more preferably 97% by mass or more. This is to suppress the rise in the glass transition temperature of copolymer (A) and improve the tackiness, wettability, and adhesion of the adhesive layer.

[0047] The content of structural units derived from monomer (a2) relative to 100 parts by mass of structural units derived from monomer (a1) is 1.0 part by mass or more, preferably 2.0 parts by mass or more, and more preferably 3.0 parts by mass or more. This is to improve the cohesive strength of the adhesive layer and enhance its heat resistance.

[0048] The content of structural units derived from monomer (a2) relative to 100 parts by mass of structural units derived from monomer (a1) is 12 parts by mass or less, preferably 8.0 parts by mass or less, and more preferably 6.0 parts by mass or less. This is because it appropriately maintains the polarity of copolymer (A) and the cohesive force of the adhesive layer, resulting in an adhesive layer with high tackiness.

[0049] The content of structural units derived from monomer (a3) ​​relative to 100 parts by mass of structural units derived from monomer (a1) is 0.10 parts by mass or more, more preferably 0.25 parts by mass or more, and even more preferably 0.35 parts by mass or more. This is to improve the cohesive strength of the adhesive layer and enhance its heat resistance.

[0050] The content of structural units derived from monomer (a3) ​​relative to 100 parts by mass of structural units derived from monomer (a1) is 10 parts by mass or less, preferably 7.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 1.5 parts by mass or less, and particularly preferably 0.75 parts by mass or less. This is because it maintains an appropriate cohesive force in the adhesive layer and yields an adhesive layer with high tackiness.

[0051] The content of structural units derived from monomer (a4) relative to 100 parts by mass of structural units derived from monomer (a1) is preferably 0.10 parts by mass or more, more preferably 0.20 parts by mass or more, and even more preferably 0.30 parts by mass or more. This is because it improves the retention strength of the adhesive layer in high-temperature environments.

[0052] The content of structural units derived from monomer (a4) relative to 100 parts by mass of structural units derived from monomer (a1) is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 1.5 parts by mass or less, and particularly preferably 0.60 parts by mass or less. This is to maintain the polarity of copolymer (A) and the cohesive force of the adhesive layer appropriately and to obtain an adhesive layer with sufficient tackiness.

[0053] [1-1-8. Glass transition temperature of copolymer (A)] The glass transition temperature (Tg) of copolymer (A) is preferably -80°C or higher, more preferably -65°C or higher, and even more preferably -55°C or higher. This is to improve the cohesive strength of the adhesive and impart superior heat resistance to the adhesive layer.

[0054] The glass transition temperature of copolymer (A) is preferably 30°C or lower, more preferably 0°C or lower, even more preferably -20°C or lower, and particularly preferably -35°C or lower. This is to improve the wettability of the adhesive composition described later and to improve the adhesion of the adhesive layer to the substrate. It is also to increase the flexibility of the adhesive layer and improve the tackiness of the adhesive layer when used dry.

[0055] Tg is a theoretical value obtained by calculating from the monomer units that make up the polymer and their proportions using the FOX formula shown below. (Math 1) 1 / T=W1 / T1+W2 / T2+W3 / T3+...+Wn / Tn T(K) = Tg(°C) + 273°C, where T is the glass transition temperature of copolymer (A) expressed in absolute temperature. Wn is the mass fraction (≤1) of each structural unit, and Tn is the glass transition temperature (absolute temperature) of the homopolymer of the compound from which each structural unit originates. In this specification, the glass transition temperatures of each homopolymer are those listed in publicly available sources. Specifically, the values ​​listed in the literature "Polymer Handbook (3rd edition, John Wiley & Sons, Inc., 1989)" are used.

[0056] [1-1-9. Method for producing copolymer (A)] The method for producing copolymer (A) is not particularly limited, but the compounds from which each structural unit constituting copolymer (A) is derived may be polymerized as monomers, or some or all of the structural units may be polymerized using other compounds first, and then functional groups may be introduced to form the desired structural units. Examples of methods for producing copolymer (A) include emulsifying monomers in an aqueous medium and carrying out emulsion polymerization using a polymerization initiator. In polymerization, a chain transfer agent may be used to control the molecular weight and distribution of the copolymer within an appropriate range. An emulsifier may be used to emulsify the monomers. The monomers may be charged into the reactor in their entirety beforehand, or, in order to obtain uniform particles, a mixture containing all types of monomers necessary to form the structural units of copolymer (A) may be supplied and charged continuously or intermittently while polymerization is performed. The polymerization temperature is not particularly limited, but is preferably 5 to 100°C, and more preferably 50 to 90°C.

[0057] The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of hydrophilic solvents include methanol, ethanol, isopropyl alcohol, and N-methylpyrrolidone. From the viewpoint of polymerization stability, the aqueous medium is preferably water. However, as long as polymerization stability is not impaired, a solution of water with a hydrophilic solvent added may also be used as the aqueous medium.

[0058] Polymerization initiators used in emulsion polymerization include persulfate initiators such as potassium persulfate and ammonium persulfate, water-soluble azo initiators such as 2,2'-azobis(2-methylpropionamidine) dihydrochloride, organic peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide. These polymerization initiators may be used individually or in combination. The amount of polymerization initiator used is preferably 0.1 to 2% by mass relative to the total amount of monomers.

[0059] Furthermore, reducing agents can be used together with these polymerization initiators as needed. Examples of such reducing agents include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate metal salts, and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite.

[0060] Examples of chain transfer agents include, but are not limited to, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, β-mercaptopropionic acid, methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, and benzyl alcohol. One or more chain transfer agents may be used.

[0061] When the amount of chain transfer agent used is reduced, the cohesive force of the adhesive improves, thereby improving heat resistance. When the amount is increased, the cohesive force of the adhesive decreases, but the adhesive strength of the adhesive layer improves. The amount of chain transfer agent used is preferably 0.0010 parts by mass or more, more preferably 0.050 parts by mass or more, and even more preferably 0.080 parts by mass or more, per 100 parts by mass of monomer for copolymer (A). This is to form an adhesive layer with strong adhesive strength.

[0062] The amount of chain transfer agent used is preferably 5.0 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 0.50 parts by mass or less, and particularly preferably 0.20 parts by mass or less, per 100 parts by mass of monomer for copolymer (A). This is to improve the heat resistance of the adhesive layer.

[0063] The emulsifier is not particularly limited, but specifically, examples include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene nonylphenyl ethers, cationic surfactants such as ceciltrimethylammonium bromide and laurylpyridinium chloride, amphoteric surfactants such as lauryl bedaine, and other reactive surfactants. These surfactants may be used individually or in combination of two or more types.

[0064] [1-2. Crosslinking agent (B)] The crosslinking agent (B) comprises one or more compounds selected from the group consisting of polycarbodiimide compounds (compounds having multiple carbodiimide groups (structures represented by -N=C=N-)), polyepoxy compounds (compounds having multiple epoxy groups), and polyisocyanate compounds (compounds having multiple isocyanate groups). The crosslinking agent (B) may also be a carbodiimide compound having epoxy groups. Among these, polycarbodiimide compounds and polyepoxy compounds are particularly preferred because they can impart high tackiness and cohesiveness to the adhesive. The crosslinking agent (B) is preferably a water-soluble or water-dispersible compound.

[0065] Examples of polycarbodiimide compounds include p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), cyclohexane-1,4-bis(methylene-t-butylcarbodiimide), and Nisshinbo Chemical's "Carbodilite (registered trademark, hereinafter the same) V-02", "Carbodilite SV-02", "Carbodilite V-04", "Carbodilite V-10", "Carbodilite E-02", "Carbodilite E-03A", and "Carbodilite E-05".

[0066] The carbodiimide equivalent (molecular weight per carbodiimide group) of the polycarbodiimide compound is preferably 150 or more, more preferably 250 or more, even more preferably 300 or more, and particularly preferably 350 or more. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and to improve the rate and density of the crosslinking reaction.

[0067] The carbodiimide equivalent (molecular weight per carbodiimide group) of the polycarbodiimide compound is preferably 1000 or less, more preferably 750 or less, and even more preferably 600 or less. This is to improve the crosslinking density in the crosslinking reaction with copolymer (A).

[0068] Examples of polyepoxy compounds include bisphenol A-epichlorohydrin type epoxy resins, sorbitol polyglycidyl ethers (e.g., "Denacol (registered trademark, hereinafter the same) EX-611", "Denacol EX-612", "Denacol EX-614", "Denacol EX-614B", "Denacol EX-622", etc. manufactured by Nagase ChemteX Corporation), polyglycerol polyglycidyl ethers (e.g., "Denacol EX-512", "Denacol EX-521", etc. manufactured by Nagase ChemteX Corporation), and pentaerythritol polyglycidyl ethers (e.g., "Denacol EX-411", etc. manufactured by Nagase ChemteX Corporation). ), diglycerol polyglycidyl ether (e.g., "Denacol EX-421" manufactured by Nagase ChemteX), glycerol polyglycidyl ether (e.g., "Denacol EX-313", "Denacol EX-314" manufactured by Nagase ChemteX), trimethylolpropane polyglycidyl ether (e.g., "Denacol EX-321" manufactured by Nagase ChemteX), resorcinol diglycidyl ether (e.g., "Denacol EX-201" manufactured by Nagase ChemteX), neopentyl glycol diglycidyl ether (e.g., "Denacol EX-211" manufactured by Nagase ChemteX), 1,6-Hexanediol diglycidyl ether (e.g., Denacol EX-212 manufactured by Nagase ChemteX), hydrogenerated bisphenol A diglycidyl ether (e.g., Denacol EX-252 manufactured by Nagase ChemteX), ethylene glycol diglycidyl ether (e.g., Denacol EX-810, Denacol EX-811 manufactured by Nagase ChemteX), diethylene glycol diglycidyl ether (e.g., Denacol EX-850, Denacol EX-851 manufactured by Nagase ChemteX), polyethylene glycol diglycidyl ether (e.g., Denacol manufactured by Nagase ChemteX) Examples include "EX-821", "Denacol EX-830", "Denacol EX-832", "Denacol EX-841", "Denacol EX-861", etc., propylene glycol diglycidyl ether (e.g., "Denacol EX-911" manufactured by Nagase ChemteX), polypropylene glycol diglycidyl ether (e.g., "Denacol EX-941", "Denacol EX-920", "Denacol EX-931" manufactured by Nagase ChemteX), diglycidylaniline, diglycidylamine, N,N,N′,N′-tetraglycidyl m-xylenediamine, 1,3-bis(N,N′-diglycidylaminomethyl)cyclohexane, etc. Among these, water-soluble types are preferred.

[0069] The epoxy equivalent (molecular weight per epoxy group) of the polyepoxy compound is preferably 70 or higher, and more preferably 100 or higher. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and to improve the rate and density of the crosslinking reaction.

[0070] The epoxy equivalent (molecular weight per epoxy group) of the polyepoxy compound is preferably 700 or less, more preferably 400 or less, even more preferably 300 or less, and particularly preferably 200 or less. This is to improve the crosslinking density in the crosslinking reaction with copolymer (A).

[0071] Examples of polyisocyanate compounds include toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and tetramethylxylylene diisocyanate. Specific examples of products include: bullet polyisocyanate compounds such as "Sumijoule N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.); polyisocyanate compounds having an isocyanurate ring such as "Desmodule IL" and "Desmodule HL" (manufactured by Bayer AG) and "Coronate EH" (manufactured by Nippon Urethane Co., Ltd.); adduct polyisocyanate compounds such as "Sumijoule L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and "Coronate HL" (manufactured by Nippon Polyurethane Co., Ltd.); and self-emulsifying water-dispersible polyisocyanate compounds such as "Aquanate 100", "Aquanate 110", "Aquanate 200", and "Aquanate 210" (manufactured by Nippon Polyurethane Co., Ltd.). Among these, water-dispersible polyisocyanate compounds are preferred. Blocked isocyanate compounds may also be used as polyisocyanate compounds.

[0072] The isocyanate equivalent (molecular weight per isocyanate group) of the polyisocyanate compound is preferably 60 or higher, and more preferably 75 or higher. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and to improve the rate and density of the crosslinking reaction.

[0073] The isocyanate equivalent (molecular weight per isocyanate group) of the polyisocyanate compound is preferably 500 or less, more preferably 200 or less, and even more preferably 100 or less. This is to improve the crosslinking density in the crosslinking reaction with copolymer (A).

[0074] [1-3. Quantitative relationship between copolymer (A) and crosslinking agent (B)] In the adhesive, the content of the crosslinking agent (B) per 100 parts by mass of copolymer (A) is preferably 0.010 parts by mass or more, more preferably 0.020 parts by mass or more, more preferably 0.050 parts by mass or more, even more preferably 0.15 parts by mass or more, and particularly preferably 0.40 parts by mass or more. This is because the crosslinking density between particles increases, the cohesive force of the adhesive improves, and the strength of the adhesive layer improves.

[0075] In the adhesive, the content of the crosslinking agent (B) per 100 parts by mass of copolymer (A) is 10 parts by mass or less, preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 1.0 part by mass or less. This is because the flexibility of the adhesive layer is improved, and stronger adhesive force can be obtained.

[0076] [1-4. Aqueous medium] The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of hydrophilic solvents include methanol, ethanol, isopropyl alcohol, and N-methylpyrrolidone. The aqueous medium is preferably water. The aqueous medium may have the same composition as the aqueous solvent used in the polymerization of copolymer (A), or it may have a different composition.

[0077] [1-5. Other Additives] Additives may be included in the adhesive composition as needed. There are no particular limitations on the timing of adding additives. Additives may be added simultaneously with or after mixing the copolymer (A) and the crosslinking agent (B). Alternatively, additives may be added to either or both of the solutions or dispersions of copolymer (A) and crosslinking agent (B) before mixing. Examples of additives include pH adjusters and tackifiers. In addition, plasticizers, antioxidants, fillers, pigments, colorants, wetting agents, defoamers, thickeners, etc., can be used as appropriate additives.

[0078] As pH adjusters, acidic substances such as common inorganic acids and organic acids, their salts, and amphoteric salts of amino acids can be used. Examples of organic acids used as pH adjusters include acetic acid, formic acid, glycolic acid, malic acid, citric acid, maleic acid, fumaric acid, malonic acid, phthalic acid, isophthalic acid, lactic acid, butyric acid, ascorbic acid, succinic acid, tartaric acid, acrylic acid, methacrylic acid, crotonic acid, adipic acid, oxalic acid, and abietic acid. Examples of inorganic acids used as pH adjusters include boric acid, phosphoric acid, hydrochloric acid, nitric acid, nitrite, sulfuric acid, and sulfite. Furthermore, examples of salts of acidic substances include salts of the above organic or inorganic acids with sodium, potassium, ammonia, aminoethanol, diethanolamine, and triethanolamine. Examples of amino acids used as pH adjusters include glycine, glycylglycine, asparagine, aspartic acid, alanine, phenylalanine, arginine, glutamine, and glutamic acid. These pH adjusters can be used individually or in combination of two or more types.

[0079] Examples of tackifiers include rosin resin, rosin ester resin, hydrogenated rosin resin, polymerized rosin resin, α-pinene resin, β-pinene resin, terpene phenol resin, C5 fraction petroleum resin, C9 fraction petroleum resin, C5 fraction / C9 fraction petroleum resin, dicyclopentadiene petroleum resin, alkylphenol resin, xylene resin, coumarone resin, coumarone indene resin, and the like. Tackifiers can be used alone or in combination of two or more types.

[0080] [1-6. Content of each component in the adhesive composition] The non-volatile content concentration of the adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. This is because a larger adhesive layer can be formed with a smaller amount of adhesive composition applied. Furthermore, the drying time of the applied adhesive composition is shortened, improving productivity.

[0081] The non-volatile content concentration of the adhesive composition is preferably 75% by mass or less, and more preferably 65% ​​by mass or less. This is to suppress the gelation of copolymer (A) in the adhesive composition.

[0082] In the adhesive composition, the total content of copolymer (A) and crosslinking agent (B) in the nonvolatile components is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. This is because it improves the adhesive strength and holding power of the adhesive layer, especially the holding power at high temperatures.

[0083] In the adhesive composition, the total content of copolymer (A) and crosslinking agent (B) in the nonvolatile components is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0084] [1-7. Adhesive Composition Preparation Set] The adhesive composition of this embodiment may be stored as a set of multiple formulations in which its constituent components are divided into multiple additives. For example, a copolymer dispersion containing the copolymer (A) and an aqueous medium, along with a crosslinking agent (B), can be prepared as a set, and the copolymer dispersion and crosslinking agent (B) can be mixed to prepare the adhesive composition when it is time to use it.

[0085] <2. Adhesive Tape> [2-1. Composition of adhesive tape] A typical application of the adhesive composition according to the present invention is adhesive tape. The adhesive tape according to this embodiment comprises a base material and an adhesive layer formed on the surface of the base material. The adhesive layer may be formed on only one side of the base material or on both sides. Furthermore, the adhesive layer of the adhesive tape of the present invention may be protected by a known release liner such as release paper or release PET.

[0086] The material of the base material is not particularly limited, but examples include paper, plastic, cloth, and metal. The base material may also be a film, woven fabric, or nonwoven fabric, and is not particularly limited, but nonwoven fabric is preferred. This is because the adhesive composition permeates the base material, increasing the bonding strength between the adhesive layer and the base material. In this invention, "base material" refers to the portion that is attached to the adherend together with the adhesive layer when the adhesive tape of the present invention is used, i.e., applied to the adherend, and does not include release liners such as release paper that are peeled off when the adhesive tape is used.

[0087] The adhesive layer contains an adhesive which is a cured product of the adhesive composition described above. In addition to this adhesive, the adhesive layer may also contain additives and the like contained in the adhesive composition. As described below, in adhesive tapes made by applying the adhesive composition to a substrate, the adhesive layer contains the non-volatile components of the adhesive composition. The thickness of the adhesive layer is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 50 μm or more. This is because the adhesive layer can be sufficiently deformed to conform to the surface of the adherend. The thickness of the adhesive layer is preferably 200 μm or less, and more preferably 100 μm or less. This is to suppress cohesive failure of the adhesive layer.

[0088] [2-2. Method for manufacturing adhesive tape] A method for manufacturing adhesive tape includes the steps of applying an adhesive composition to one or both sides of a substrate, and removing an aqueous medium from the adhesive composition applied to the substrate to form an adhesive layer. During application, an aqueous medium or a thickener may be added to the adhesive composition as appropriate to adjust its viscosity. When applying the adhesive composition to both sides, it may be applied to one side at a time, or to both sides at once. The adhesive composition may be applied to the substrate continuously or intermittently. The adhesive layer may contain two or more adhesive layers. Furthermore, the adhesive tape of the present invention may also include other layers (for example, an intermediate layer, an undercoat layer, etc.) in addition to the base material and the adhesive layer, as long as they do not impair the effects of the invention.

[0089] The amount of adhesive composition to be applied is not particularly limited, but is 10 to 500 g / m². 2 It is preferable that the adhesive composition applied to the substrate has a drying temperature that is not particularly limited, but is preferably 20 to 160°C. This is because an adhesive layer with sufficient adhesive strength and cohesive strength can be obtained.

[0090] <3. Uses of adhesive compositions and adhesive tapes> Here, adhesive tape has been described as one preferred application of the adhesive composition of the present invention, but the applications of the adhesive composition of the present invention are not limited to this. For example, the adhesive composition of the present invention may be applied directly to a component and bonded to another component without using adhesive tape. Furthermore, applications of adhesive tape and bonding methods characterized by the use of adhesive tape include, for example, electrical products, automobiles, building materials, toys, etc. The adherend of the adhesive tape is not particularly limited, but it is particularly useful when it is a plastic component such as polypropylene or a metal component such as SUS or aluminum. [Examples]

[0091] Examples and comparative examples of the present invention will be described below. However, the present invention is not limited by the examples.

[0092] <1. Preparation of adhesive composition> In a polymerization apparatus equipped with a stirrer, thermometer, and reflux condenser, 23 parts by mass of deionized water and 0.10 parts by mass of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier were mixed and heated to 80°C under a nitrogen atmosphere. The mixture in the polymerization apparatus was kept at 80°C while being stirred, and 2 parts by mass of a 5.0% by mass potassium persulfate aqueous solution was added as a polymerization initiator. A monomer emulsion containing 50 parts by mass of deionized water, 1 part by mass of emulsifier, and a total of 100 parts by mass of monomer and chain transfer agent was added dropwise to the mixture to which the polymerization initiator had been added over 4 hours. The types of monomer and chain transfer agent added dropwise here are as shown in Tables 1, 2-1, and 2-2 for each example and comparative example. The content of each component in the total 100 parts by mass of monomer and chain transfer agent added dropwise here is as shown in the left column of each example and comparative example in Tables 1 and 2. The amounts of monomer and chain transfer agent used per 100 parts by mass of monomer (a1) are as shown in the right-hand column of each example and comparative example in Tables 1, 2-1, and 2-2. Simultaneously with the start of the monomer emulsion addition, 20 parts by mass of a 2.5% by mass potassium persulfate aqueous solution was added dropwise over 4 hours.

[0093] After the dropwise addition was complete, the mixture was reacted at 80°C for 2 hours. The mixture in the polymerization apparatus was then cooled to 25°C. Ammonia water was added as a neutralizing agent to adjust the pH to 8.5. Furthermore, 25 parts by mass of Super Ester E-865NT (manufactured by Arakawa Chemical Industries, Ltd.) was added as a tackifier, and 2.0 parts by mass of Primal ASE-60 (manufactured by Dow Chemical Corporation) was added as a thickening agent. Subsequently, in each example and comparative example, the type and amount of crosslinking agent (crosslinking agent (B) or other crosslinking agent) shown in the left column of Tables 1, 2-1, and 2-2 was added to obtain the adhesive composition. Note that the amount of crosslinking agent added in the following tables means "amount of crosslinking agent added (parts by mass) per 100 parts by mass of copolymer (A)".

[0094] [Table 1]

[0095] [Table 2-1]

[0096] [Table 2-2]

[0097] <2. Making adhesive tape> The adhesive compositions obtained in each example and comparative example were applied to the release surface of release paper (KP-8D, manufactured by Hayashi Convertec Co., Ltd.). A doctor blade applicator with a coating width of 15 cm was used. The applied adhesive composition was dried at 100°C for 3 minutes to remove the aqueous medium from the adhesive composition, forming an adhesive composition coating layer with a thickness of 60 μm on the release surface. The adhesive composition coating layer on the release surface was cut into A4 size pieces with a thickness of 40 μm and a basis weight of 14 g / m². 2 The adhesive composition was transferred to both sides of a nonwoven fabric (base material: rayon). The adhesive composition coating layer transferred onto the nonwoven fabric was cured at 40°C for 3 days to form an adhesive layer. In this way, an adhesive tape comprising a base material and an adhesive layer formed on the surface of the base material was obtained. In order to avoid foreign matter adhering to the adhesive layer, the release paper was not removed after transfer.

[0098] <3. Evaluation of adhesive tape> The adhesive tapes prepared in each example and comparative example were evaluated as follows. The evaluation results are shown in Tables 1, 2-1, and 2-2. In the following description, the procedures in each example and comparative example are common unless otherwise specified.

[0099] [3-1. Evaluation 1: Measurement of initial adhesion] The release paper on one side of the adhesive tape was peeled off, and a 25 μm thick polyethylene terephthalate (PET) film was attached. This film was cut to 25 mm x 250 mm. Furthermore, half of the release paper on the opposite side of the adhesive tape was peeled off in the longitudinal direction and cut out, and this was bonded to a polypropylene (PP) board to create an evaluation sample. The bonding was performed by running a 2 kg roller back and forth once in an atmosphere of 23°C. In the evaluation sample, the bonded portion between the adhesive tape and the polypropylene board is a rectangle of 25 mm x 125 mm. The edges of the bonded portion were not to overlap with the edges of the polypropylene board. That is, in this state, one half of the adhesive tape in the longitudinal direction is bonded to the polypropylene board, and the other half is bonded to the release paper.

[0100] After preparing the evaluation samples, they were left in an atmosphere at 23°C for 30 minutes. Subsequently, the following measurements were performed in an atmosphere at 23°C.

[0101] The test is a so-called 180° peel test. The adhesive tape of the evaluation sample was folded 180° along the boundary between the portion attached to the polypropylene board and the portion not attached. One end of the adhesive tape that was not attached to the polypropylene board (the folded end) was grasped by the upper chuck of the testing machine (Tensilon RTG-1210 (manufactured by A&D Co., Ltd.)). The other end of the polypropylene board, opposite the upper chuck across the fold line, was grasped by the lower chuck.

[0102] In that state, the adhesive tape was peeled off the polypropylene board at a speed of 200 mm / min, and a graph of peel length (mm) - peel force (N) was obtained. From the obtained graph, the average value of the peel force (N) for peel lengths of 25 to 100 mm (the value obtained by dividing the area of ​​the graph for peel lengths of 25 to 100 mm by the peel length) was calculated, and this value was taken as the initial adhesive force (N / 25 mm). In all examples and comparative examples, peeling between the adhesive layer and the substrate, and cohesive failure of the adhesive layer did not occur during the test.

[0103] [3-2. Evaluation 2: Measurement of adhesive strength under high-temperature conditions] After preparing evaluation samples using the same procedure as described above, they were placed in a constant temperature bath at 70°C for 30 minutes. Subsequently, a 180° peel test was performed using the same procedure as described above under a 70°C atmosphere, and the average value (mN) of the peel force at peel lengths of 25 to 100 mm was defined as the adhesive strength (N / 25 mm) after high-temperature storage. For measurements in the high-temperature environment, an Autograph AG-X (manufactured by Shimadzu Corporation) was used as the testing machine.

[0104] [3-3. Evaluation 3: Measurement of high-temperature retention capacity] A release liner was peeled off one side of a double-sided adhesive tape, and a 25 μm thick polyethylene terephthalate (PET) film was attached. On the other side of the adhesive tape, the release liner was peeled off 25 mm from one end in the longitudinal direction, and a SUS plate (SUS#304) was bonded to cover the entire area where the release liner had been peeled off, thereby creating an evaluation sample. In other words, in the evaluation sample, the area where the adhesive tape and the SUS plate were bonded together was a 25 mm x 25 mm square. The bonding was performed by running a 2 kg roller back and forth once in an atmosphere of 23 °C. At this time, the portion of the SUS plate that was not bonded to the adhesive tape, extending from the end of the adhesive tape that was bonded to the SUS plate, was designated as the SUS plate side chuck portion.

[0105] The evaluation sample was placed in an 80°C constant temperature bath for 30 minutes. Then, while still in the 80°C constant temperature bath, a testing machine (holding force tester (manufactured by Tester Industry Co., Ltd.)) was used to grip the chuck portion on the SUS plate side of the evaluation sample with the chuck, and a 500g weight was suspended from one end of the adhesive tape in the longitudinal direction on the side not attached to the SUS plate, and left for 24 hours. After that, the distance (mm) that the adhesive tape shifted vertically relative to the SUS plate was measured.

[0106] <4. Evaluation Results> As shown in Table 1, the adhesive tapes produced using the adhesive compositions according to the examples exhibit strong adhesive strength not only at room temperature but also at high temperatures, and it can be seen that an adhesive layer with high holding power at high temperatures is formed.

[0107] On the other hand, in the adhesive tapes according to Comparative Examples 1 to 4 and Comparative Examples 6 to 9, which were prepared using an adhesive composition in which the copolymer (A) does not contain structural units derived from monomers (a3) ​​having epoxy groups, at least one of the high-temperature adhesive strength and high-temperature holding strength is insufficient.

[0108] In these studies, Comparative Example 2 increased the amount of crosslinking agent (B) in the adhesive composition, but the high-temperature adhesive strength of the adhesive tape decreased. In Comparative Examples 3 and 4, a polyepoxy compound was used as the crosslinking agent (B), but the high-temperature retention or high-temperature adhesive strength of the adhesive tape was insufficient. From these findings, it can be seen that in a copolymer (A) that does not contain structural units derived from monomers (a3) ​​having epoxy groups, the objective of the present invention cannot be achieved by increasing the amount of crosslinking agent (B) in the adhesive composition or by changing the type of functional group of the crosslinking agent (B).

[0109] Furthermore, among the above comparative examples, the adhesive tapes according to Comparative Example 7, in which copolymer (A) contained a large amount of structural units derived from ethylene glycol dimethacrylate instead of structural units derived from monomer (a3), and Comparative Example 9, in which copolymer (A) contained a large amount of structural units derived from divinylbenzene, exhibited insufficient initial adhesive strength. In addition, the adhesive tapes according to Comparative Example 6, in which copolymer (A) contained a small amount of structural units derived from ethylene glycol dimethacrylate instead of structural units derived from monomer (a3), and Comparative Example 8, in which copolymer (A) contained a small amount of structural units derived from divinylbenzene, exhibited significantly inferior high-temperature retention. From these findings, it can be seen that in a copolymer (A) configuration that does not contain structural units derived from monomer (a3) ​​having an epoxy group, the objective of the present invention cannot be achieved by introducing structural units derived from a compound having multiple independent ethylenically unsaturated bonds instead.

[0110] The adhesive tape according to Comparative Example 5, which was prepared using an adhesive composition that does not contain the crosslinking agent (B), has significantly inferior high-temperature retention.

[0111] In Comparative Example 10, where a crosslinking agent containing an aziridine group was used instead of crosslinking agent (B), the high-temperature adhesion and high-temperature retention were insufficient.

[0112] As described above, the present invention provides a water-dispersible adhesive composition that can form an adhesive layer that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and further possesses high holding power at high temperatures. Furthermore, the present invention provides an adhesive tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and further possesses high holding power at high temperatures.

Claims

1. An adhesive composition comprising a copolymer (A), a crosslinking agent (B), and an aqueous medium, The copolymer (A) has a structural unit derived from monomer (a1), a structural unit derived from monomer (a2) having a carboxyl group, and a structural unit derived from monomer (a3) ​​having an epoxy group. The monomer (a1) is an alkyl (meth)acrylate having only one ethylenically unsaturated bond, The content of structural units derived from monomer (a2) in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less. The content of structural units derived from monomer (a3) ​​in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 0.10 parts by mass or more and 1.5 parts by mass or less. The crosslinking agent (B) comprises one or more selected from the group consisting of polycarbodiimide compounds, polyepoxy compounds, and polyisocyanate compounds. An adhesive composition in which the amount of the crosslinking agent (B) per 100 parts by mass of the copolymer (A) is 0.010 parts by mass or more and 10 parts by mass or less.

2. The adhesive composition according to claim 1, wherein the copolymer (A) has structural units derived from a monomer (a4) having a hydroxyl group, and the content of structural units derived from monomer (a4) in the copolymer (A) is 0.10 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of structural units derived from monomer (a1).

3. The adhesive composition according to claim 1 or 2, wherein the copolymer (A) does not have structural units derived from a compound having a plurality of independent ethylenically unsaturated bonds.

4. The adhesive composition according to any one of claims 1 to 3, wherein the copolymer (A) contains a total of 90% by mass or more of structural units derived from monomer (a1), structural units derived from monomer (a2), and structural units derived from monomer (a3).

5. The adhesive composition according to any one of claims 1 to 4, wherein the glass transition temperature of the copolymer (A) is -80°C or higher and 30°C or lower.

6. The adhesive composition according to any one of claims 1 to 5, wherein the monomer (a1) is an alkyl (meth)acrylate.

7. The adhesive composition according to any one of claims 1 to 6, wherein the crosslinking agent (B) is a polycarbodiimide compound.

8. The adhesive composition according to claim 7, wherein the carbodiimide equivalent of the crosslinking agent (B) is 150 or more and 1000 or less.

9. The adhesive composition according to any one of claims 1 to 6, wherein the crosslinking agent (B) is a polyepoxy compound.

10. The adhesive composition according to claim 9, wherein the epoxy equivalent of the crosslinking agent (B) is 70 or more and 700 or less.

11. The adhesive composition according to any one of claims 1 to 10, wherein the total content of the copolymer (A) and the crosslinking agent (B) in the nonvolatile content is 50% by mass or more.

12. A copolymer dispersion used for preparing the adhesive composition according to any one of claims 1 to 11, The copolymer (A) and the aqueous medium are included. The copolymer (A) has a structural unit derived from monomer (a1), a structural unit derived from monomer (a2) having a carboxyl group, and a structural unit derived from monomer (a3) ​​having an epoxy group. The monomer (a1) is an alkyl (meth)acrylate having only one ethylenically unsaturated bond, The content of structural units derived from monomer (a2) in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less. A copolymer dispersion in which the content of structural units derived from monomer (a3) ​​in the copolymer (A) is 0.10 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of structural units derived from monomer (a1).

13. A set used for preparing adhesive compositions, The copolymer dispersion and crosslinking agent (B) are included. The copolymer dispersion comprises copolymer (A) and an aqueous medium. The copolymer (A) has a structural unit derived from monomer (a1), a structural unit derived from monomer (a2) having a carboxyl group, and a structural unit derived from monomer (a3) ​​having an epoxy group. The monomer (a1) is an alkyl (meth)acrylate having only one ethylenically unsaturated bond, The content of structural units derived from monomer (a2) in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 1.0 part by mass or more and 12 parts by mass or less. The content of structural units derived from monomer (a3) ​​in the copolymer (A) relative to 100 parts by mass of structural units derived from monomer (a1) is 0.10 parts by mass or more and 1.5 parts by mass or less. The crosslinking agent (B) comprises one or more selected from the group consisting of polycarbodiimide compounds, polyepoxy compounds, and polyisocyanate compounds. The set is such that the amount of the crosslinking agent (B) per 100 parts by mass of the copolymer (A) is 0.010 parts by mass or more and 10 parts by mass or less.

14. An adhesive tape comprising a base material and an adhesive layer formed on the surface of the base material, The adhesive layer is an adhesive tape comprising a cured product of the adhesive composition according to any one of claims 1 to 11.

15. A bonding method using the adhesive tape described in claim 14.

16. A step of applying the adhesive composition according to any one of claims 1 to 11 to a substrate, A method for producing an adhesive tape, comprising the step of removing an aqueous medium from the adhesive composition applied to the substrate to form an adhesive layer.

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