Adhesive composition, adhesive tape, adhesive method, and kit

Abstract

A pressure-sensitive adhesive composition containing: a copolymer (A) having a structural unit derived from a monomer (a1), a structural unit derived from a monomer (a2), a structural unit derived from a monomer (a3), and a structural unit derived from a monomer (a4); the monomer a1 is an alkyl (meth) acrylate having a homopolymer glass transition temperature of-40 DEG C or less and having only one ethylenically unsaturated bond; the monomer (a2) is at least one selected from the group consisting of alkyl (meth) acrylates having only one ethylenically unsaturated bond and hydrocarbons having only one ethylenically unsaturated bond and the homopolymer has a glass transition temperature of 80 DEG C or higher, and the monomer (a3) is (meth) acrylonitrile; the content of a structural unit derived from the monomer (a3) is 0.1-5.0 mass%, and at least one of the crosslinking agents (B) is a polyepoxy compound.

Description

Technical Field

[0001] The present invention relates to an adhesive composition and related technologies thereof. Background Art

[0002] As a representative use of an adhesive, there is an adhesive tape. The adhesive tape has a layer containing an adhesive, i.e., an adhesive layer, formed on a substrate, and the adhesive tape is adhered to an article, for example, to repair various articles or fix articles to each other. In addition, a double-sided adhesive tape having adhesive layers formed on both sides of a substrate is used for a wide range of applications such as transportation equipment such as automobiles, household electrical appliances, and stationery. In these industrial applications, more stringent performance requirements are required, such as adhesion to very difficult-to-bond adherends, adhesion reliability under severe environmental conditions, and adhesion in a small area.

[0003] As a representative production method of an adhesive tape, a coating liquid obtained by dissolving or dispersing an adhesive in a liquid medium is coated on a substrate and dried, thereby forming an adhesive layer on the surface of the substrate. Natural rubber-based, synthetic rubber-based, acrylic-based, etc. are widely used as adhesives, and in particular, the acrylic-based has a great feature of being able to impart various functions. In recent years, a large amount of research has been conducted on using water as the liquid medium.

[0004] For example, Patent Document 1 describes an adhesive tape having an adhesive layer formed of a water-dispersed acrylic-based adhesive composition containing acrylic copolymer emulsion particles and a crosslinking agent in an aqueous medium, wherein the acrylic copolymer forming the acrylic copolymer emulsion particles contains (meth)acrylate having an alkyl group having 2 to 14 carbon atoms, a vinyl monomer containing a carboxyl group, and a vinyl monomer containing nitrogen as monomer components.

[0005] Patent Document 2 describes a polyethylene terephthalate bottle-attaching label formed of a water-dispersed adhesive composition, wherein the water-dispersed adhesive composition contains an aqueous emulsion containing an acrylic copolymer and a tackifier and a crosslinking agent, and the monomer components constituting the acrylic copolymer include 2-ethylhexyl acrylate, acrylonitrile, and an ethylenically unsaturated monomer having a carboxyl group.

[0006] Patent Document 3 describes an acrylic emulsion type pressure-sensitive adhesive, characterized by containing an acrylic emulsion and a phosphate-based emulsifier, and the acrylic emulsion is obtained by emulsion polymerization of an acrylate having an alkyl group having 4 to 12 carbon atoms, acrylonitrile and / or methacrylonitrile, and an α,β-unsaturated carboxylic acid in the presence of an anionic reactive emulsifier.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-209170

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2012-062416

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2001-040313 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] The adhesive tape of Patent Document 1, the bottle-attaching label of Patent Document 2, and the acrylic emulsion pressure-sensitive adhesive of Patent Document 3 all exhibit good adhesive strength under normal temperature conditions, but there is room for improvement in adhesive strength under high-temperature and low-temperature conditions. In addition, there is also room for improvement in the holding strength under high-temperature conditions.

[0014] In this specification, the adhesive strength is defined as "the force generated by the contact between the adhesive surface such as the adhesive tape and the adherend", and refers to the force required to peel the adhesive surface from the adherend. In addition, in this specification, the holding strength is defined as "the force that the adhesive layer constituting the adhesive surface withstands the offset when a static load is applied in the longitudinal direction after pasting the adhesive surface such as the adhesive tape to the adherend", and represents the strength of the cohesive force of the adhesive layer constituting the above-mentioned adhesive surface.

[0015] The subject of the present invention is to provide an adhesive composition and related technologies capable of forming an adhesive layer that exhibits strong adhesive strength not only under normal temperature conditions but also under high-temperature and low-temperature conditions, and further has high holding strength under high-temperature conditions.

[0016] Means for Solving the Problems

[0017] The present inventors conducted in-depth research and found that the above problems can be solved by an adhesive composition having a specific composition. The present invention has been completed based on this finding.

[0018] In order to achieve the above object, the present invention provides the following [1] to

[10] .

[0019] [1] An adhesive composition comprising a copolymer (A), a crosslinking agent (B), and an aqueous medium, wherein,

[0020] the copolymer (A) has a structural unit derived from a monomer (a1), a structural unit derived from a monomer (a2), a structural unit derived from a monomer (a3), and a structural unit derived from a monomer (a4),

[0021] the monomer (a1) is an (alkyl) acrylate having a glass transition temperature of -40°C or lower for the homopolymer and having only one ethylenically unsaturated bond,

[0022] The glass transition temperature of the homopolymer of the monomer (a2) is 80°C or higher, and it is at least one selected from the group consisting of (meth)acrylic acid alkyl esters having only one ethylenically unsaturated bond and hydrocarbons having only one ethylenically unsaturated bond.

[0023] The monomer (a3) is (meth)acrylonitrile.

[0024] The monomer (a4) is a monomer having only one ethylenically unsaturated bond and a functional group that reacts with the epoxy group of the crosslinking agent (B).

[0025] The content ratio of the structural unit derived from the monomer (a3) is 0.1% by mass or more and 5.0% by mass or less.

[0026] At least one of the crosslinking agents (B) is a polyepoxy compound.

[0027] 〔2〕The adhesive composition according to 〔1〕, wherein the monomer (a4) has at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group.

[0028] 〔3〕The adhesive composition according to 〔1〕, wherein the monomer (a4) has a carboxyl group.

[0029] 〔4〕The adhesive composition according to 〔1〕, wherein the monomer (a4) contains a monomer having a carboxyl group and a monomer having a hydroxyl group.

[0030] 〔5〕The adhesive composition according to any one of 〔1〕 to 〔4〕, wherein the epoxy equivalent of the crosslinking agent (B) is 70 or more and 700 or less.

[0031] 〔6〕The adhesive composition according to any one of 〔1〕 to 〔5〕, wherein the total content ratio of the copolymer (A) and the crosslinking agent (B) is 50% by mass or more in 100% by mass of the non-volatile components of the adhesive composition.

[0032] 〔7〕An adhesive tape, which comprises a substrate and an adhesive layer formed on the substrate, and the adhesive layer contains a cured product of the adhesive composition according to any one of 〔1〕 to 〔6〕.

[0033] 〔8〕A method for manufacturing an adhesive tape, which includes: a step of coating the adhesive composition according to any one of 〔1〕 to 〔6〕 on a substrate; and a step of removing the aqueous medium from the adhesive composition coated on the substrate and curing it to form an adhesive layer.

[0034] 〔9〕A bonding method, which uses the adhesive tape described in [7].

[0035] 〔10〕A kit for preparing an adhesive composition,

[0036] The kit includes:

[0037] A copolymer-containing liquid containing a copolymer (A) and an aqueous medium, and

[0038] A crosslinking agent (B),

[0039] wherein,

[0040] The copolymer (A) has a structural unit derived from a monomer (a1), a structural unit derived from a monomer (a2), a structural unit derived from a monomer (a3), and a structural unit derived from a monomer (a4),

[0041] The monomer (a1) is an (alkyl) acrylate having a glass transition temperature of -40 °C or lower for the homopolymer and having only one ethylenically unsaturated bond,

[0042] The monomer (a2) is a homopolymer having a glass transition temperature of 80 °C or higher and is at least one selected from the group consisting of an (alkyl) acrylate having only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond,

[0043] The monomer (a3) is (meth)acrylonitrile,

[0044] The content ratio of the structural unit derived from the monomer (a3) is 0.1% by mass or more and 5.0% by mass or less,

[0045] At least one of the crosslinking agents (B) is a polyepoxide.

[0046] Advantages of the Invention

[0047] According to the present invention, it is possible to provide an adhesive composition and related technologies thereof, and the adhesive composition can form an adhesive layer that exhibits strong adhesion not only in a normal temperature environment but also in a high temperature environment and a low temperature environment, and further has a high holding force in a high temperature environment. Detailed Embodiments

[0048] In the following description, unless otherwise specified, "surface" refers to the "surface".

[0049] "High temperature environment" is a temperature environment higher than normal temperature (20 - 25 °C), for example, a temperature environment of 60 - 90 °C.

[0050] "Low temperature environment" is a temperature environment lower than normal temperature (20 - 25 °C), for example, a temperature environment of -25 - 5 °C.

[0051] “(Meth)acryloyl” refers to the general term for acryloyl and methacryloyl, and “(meth)acrylate” refers to the general term for acrylate and methacrylate. Similarly, “(meth)acrylonitrile” refers to the general term for acrylonitrile and methacrylonitrile.

[0052] Unless otherwise specified, “ethylenically unsaturated bond” refers to an ethylenically unsaturated bond having free radical polymerizability.

[0053] In a polymer of a monomer having an ethylenically unsaturated bond, the structural unit derived from a certain monomer having an ethylenically unsaturated bond has the following corresponding relationship: the chemical structure of the part other than the ethylenically unsaturated bond of the monomer is the same as the chemical structure of the part other than the part corresponding to the ethylenically unsaturated bond of the structural unit in the polymer. For example, the structural unit derived from acrylic acid has a structure represented by -CH2CH(COOH)- in the polymer.

[0054] In the following description, the monomer that is the source of a certain structural unit refers to a compound in the above relationship with the structural unit, and does not need to be the same as the monomer used in the actual manufacturing process.

[0055] It should be noted that for a structural unit having an ionic functional group such as a carboxyl group, unless otherwise specified, whether a part of the functional group is ion-exchanged or not ion-exchanged, it is regarded as a structural unit derived from the same ionic compound. For example, the structural unit represented by -CH2C(CH3)(COONa)- is also regarded as a structural unit derived from methacrylic acid.

[0056] In addition, for a compound having a plurality of independent ethylenically unsaturated bonds, as a structural unit of a polymer, the ethylenically unsaturated bond may remain. The plurality of independent ethylenically unsaturated bonds refer to a plurality of ethylenically unsaturated bonds that do not form a conjugated diene with each other. For example, the structural unit derived from divinylbenzene may be a structure without an ethylenically unsaturated bond (a form in which the part corresponding to any ethylenically unsaturated bond is introduced into the polymer chain), or a structure having one ethylenically unsaturated bond (a form in which only the part corresponding to one ethylenically unsaturated bond is introduced into the polymer chain).

[0057] Furthermore, after polymerization, when a functional group such as a carboxyl group other than the chain structure corresponding to the ethylenically unsaturated bond in the polymer becomes chemically non-corresponding to the chemical structure of the monomer, the structural unit of the polymer is regarded as a structural unit derived from a compound having an ethylenically unsaturated bond in the polymer. For example, in the case of polymerizing vinyl acetate and then saponifying it, based on the chemical structure of the polymer, the structural unit of the polymer is set as a structural unit derived from vinyl alcohol instead of a structural unit derived from vinyl acetate.

[0058] "Non-volatile component" is the component remaining after weighing 1 g of the adhesive composition in an aluminum dish with a diameter of 5 cm and drying it at 105°C for 1 hour while circulating air in a dryer under 1 atmospheric pressure (1013 hPa). The form of the adhesive composition may be a solution, a dispersion (emulsion), a slurry, but is not limited to these. Here, the dispersion means that fine particles are uniformly and stably present in the dispersion medium without dissolving in the solvent, and the slurry means a fluid in which solid particles such as clay and pigments are suspended in a liquid.

[0059] "Non-volatile component concentration" refers to the mass ratio (mass %) of the non-volatile component after drying under the above conditions to the mass (1 g) of the adhesive composition before drying.

[0060] In this specification, "the adhesive formed from the adhesive composition" refers to the cured product of the above adhesive composition, that is, the adhesive obtained by removing moisture from the adhesive composition and then curing it (hereinafter, sometimes simply referred to as "adhesive").

[0061] In one embodiment, the above adhesive is obtained by drying the above adhesive composition at 100°C for 3 minutes and then allowing it to stand at 40°C for 3 days to cure. It is considered that the curing of the adhesive composition is completed during the 3 days of standing at 40°C.

[0062] In addition, in this specification, "the adhesive composition coating layer" refers to the layer formed on the substrate, release paper (hereinafter referred to as the substrate, etc.) by removing the aqueous medium from the adhesive composition coated on the substrate, release paper (hereinafter referred to as the substrate, etc.).

[0063] The above-mentioned adhesive composition coating layer can be cured to obtain an adhesive layer.

[0064] In one embodiment, the above adhesive layer is obtained by curing the above adhesive composition coating layer by allowing it to stand at 40°C for 3 days.

[0065] The above-mentioned adhesive layer can be a layer formed by transferring the adhesive composition coating layer formed on the release paper to a substrate such as a non-woven fabric and then curing it by curing at 40°C for 3 days.

[0066] <1. Adhesive composition>

[0067] The adhesive composition of this embodiment contains a copolymer (A), a crosslinking agent (B), and an aqueous medium. Other additives, etc. may be contained in the adhesive composition.

[0068] In the adhesive composition, the copolymer (A) may exist in the form of emulsion particles (dispersed particles) in the aqueous medium. The copolymer (A) can be obtained by emulsion polymerization described later.

[0069] 〔1-1. Copolymer (A)〕

[0070] The copolymer (A) has a structural unit derived from the following monomer (a1), a structural unit derived from the following monomer (a2), a structural unit derived from the following monomer (a3), and a structural unit derived from the following monomer (a4). The content of the structural unit derived from the monomer (a3) is 0.1% by mass or more and 5.0% by mass or less.

[0071] Furthermore, the copolymer (A) may include a structural unit derived from another monomer (a5) that does not belong to any of the structural units derived from the monomers (a1) to (a4).

[0072] In addition, the copolymer (A) may include a structure derived from other compounds (a6) such as a chain transfer agent.

[0073] The glass transition temperature of each homopolymer can be the value described in publicly known materials. Each of the following glass transition temperatures (hereinafter, also referred to as Tg) in the present disclosure is the value described in the literature "Polymer Handbook (Third Edition, John Wiley & Sons, Inc., 1989)".

[0074] [1-1-1. Monomer (a1)]

[0075] The monomer (a1) is an (alkyl) acrylate whose homopolymer has a glass transition temperature of -40°C or lower. The monomer (a1) has only one ethylenically unsaturated bond.

[0076] As the monomer (a1), one compound may be used, or two or more compounds may be used.

[0077] Examples of the compound corresponding to the monomer (a1) include n-butyl acrylate (Tg: -52°C), 2-ethylhexyl acrylate (Tg: -70°C), octyl acrylate (Tg: -65°C), nonyl acrylate (Tg: -58°C), lauryl methacrylate (Tg: -65°C), etc. Among them, from the viewpoint of easy control of physical properties, n-butyl acrylate and 2-ethylhexyl acrylate are preferred. It should be noted that the Tg value in parentheses is the glass transition temperature of the homopolymer of the monomer. The same applies hereinafter.

[0078] [1-1-2. Monomer (a2)]

[0079] The monomer (a2) is at least one selected from the group consisting of an (alkyl) acrylate having a glass transition temperature of 80°C or higher and only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond. The monomer (a2) has only one ethylenically unsaturated bond.

[0080] The monomer (a2) preferably contains an alkyl (meth)acrylate, and more preferably consists of an alkyl (meth)acrylate.

[0081] As the monomer (a2), one compound can be used, or two or more compounds can be used.

[0082] Examples of the compound corresponding to the monomer (a2) include isopropyl methacrylate (Tg: 81 °C), methyl methacrylate (Tg: 105 °C), tert-butyl methacrylate (Tg: 118 °C), cyclohexyl methacrylate (Tg: 83 °C), isobornyl acrylate (Tg: 94 °C), isobornyl methacrylate (Tg: 170 °C), phenyl methacrylate (Tg: 110 °C), styrene (Tg: 100 °C), α-methylstyrene (Tg: 185 °C), etc. Among them, from the aspect of easy control of physical properties, methyl methacrylate is preferred. In addition, a compound that corresponds to (a2) and also corresponds to (a4) described later is regarded as corresponding to (a2).

[0083] [1-1-3. Monomer (a3)]

[0084] The monomer (a3) is (meth)acrylonitrile, that is, acrylonitrile or methacrylonitrile.

[0085] From the viewpoint of improving the adhesion at low temperature, acrylonitrile is preferably used.

[0086] The mechanism by which (meth)acrylonitrile (a3) improves the adhesion of the adhesive layer at low temperature is not yet determined, but the present inventors presume the following mechanism. That is, it is presumed that (meth)acrylonitrile can evenly arrange the reactive functional groups that are easily oriented throughout the copolymer by interacting with the functional groups derived from the monomer (a4) described later in the copolymer (A). From this, it is presumed that the obtained adhesive layer moderately maintains the cohesive force, and the adhesion is improved not only at normal temperature but also at high temperature and low temperature.

[0087] [1-1-4. Monomer (a4)]

[0088] The monomer (a4) has only one ethylenically unsaturated bond and has a functional group that reacts with the epoxy group of the crosslinking agent (B). It preferably has at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group as the functional group. The functional group is more preferably a carboxyl group and a hydroxyl group, and further preferably a carboxyl group.

[0089] As the monomer (a4), one compound can be used, or two or more compounds can be used.

[0090] As the monomer (a4), 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, 2-acryloyloxyethyl succinic acid, etc.; vinyl compounds containing a carboxyl group such as mono-hydroxyethyl (meth)acrylate phthalate, mono-hydroxypropyl (meth)acrylate oxalate, etc.; ethylenically unsaturated compounds having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, etc.; ethylenically unsaturated compounds having a sulfo group such as vinylsulfonic acid, styrenesulfonic acid, allyl sulfonate, 2-sulfoethyl (meth)acrylate, etc.; ethylenically unsaturated compounds having a phosphoric acid group such as 2-acid phosphatooxyethyl (meth)acrylate, 2-acid phosphatooxypropyl (meth)acrylate, acid phosphatooxy polyethylene glycol (meth)acrylate, etc.; alkylamino (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate, etc.

[0091] From the viewpoint of improving the retention at high temperature, the monomer (a4) preferably has a carboxyl group, and more preferably is (meth)acrylic acid.

[0092] The mechanism by which the monomer (a4) having a carboxyl group improves the retention of the adhesive layer at high temperature is not yet certain, but the present inventors presume the following mechanism. That is, it is presumed that the carboxyl group of the monomer (a4) reacts with the functional group of the crosslinking agent (B) described later to form intermolecular crosslinking (external crosslinking), and the internal cohesion is imparted to the adhesive layer through this crosslinking, and the retention of the adhesive layer at high temperature is improved.

[0093] Part or all of the carboxyl groups of the monomer (a4) may form a salt. As the monomer (a4) forming a salt, for example, metal salts, ammonium salts, etc. of the monomer (a4) can be cited. As the metal of the metal salt, for example, alkali metals such as lithium, sodium, potassium, etc. can be cited. The formation ratio of the salt is preferably 10% or less based on the number (mol number).

[0094] From the viewpoint of improving the retention of the adhesive layer at high temperature, the monomer (a4) preferably has a hydroxyl group, and more preferably is a (meth)acrylate having a hydroxyl group, that is, a hydroxyalkyl (meth)acrylate, and further preferably is 2-hydroxyethyl (meth)acrylate.

[0095] The mechanism by which the monomer (a4) having a hydroxyl group improves the retention of the adhesive layer at high temperature is not yet certain, but the present inventors presume based on the following mechanism. That is, it is presumed that it reacts with the functional group of the crosslinking agent (B) described later to form intermolecular crosslinking (external crosslinking), whereby the retention of the adhesive layer at high temperature is improved.

[0096] [1-1-5. Monomer (a5)]

[0097] The monomer (a5) is a compound that does not belong to any of the structural units derived from the monomers (a1) to (a4) and has an ethylenically unsaturated bond.

[0098] Examples of the monomer (a5) include (meth)acrylic acid alkyl esters such as methyl acrylate (Tg: 8 °C), ethyl acrylate (Tg: -22 °C), ethyl methacrylate (Tg: 65 °C), n-butyl methacrylate (Tg: 20 °C), isobutyl acrylate (Tg: -24 °C), isobutyl methacrylate (Tg: 48 °C), cyclohexyl acrylate (Tg: 16 °C), 2-ethylhexyl methacrylate (Tg: -10 °C), lauryl acrylate (Tg: 10 °C), stearyl acrylate (Tg: 35 °C), stearyl methacrylate (Tg: 38 °C), etc.; vinyl ester compounds such as vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, etc.; conjugated diene compounds such as butadiene, isoprene, chloroprene, etc.; vinyl compounds containing an amidoimide group such as 1,1,1-trimethylaminomethylacrylimide, etc.; (meth)acrylamide compounds such as (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, etc.; vinyl compounds containing an alkoxysilyl group such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, etc.; vinyl compounds containing an epoxy group such as (meth)acrylic acid glycidyl ester, glycidyl vinyl ether, glycidyl (meth)allyl ether, etc.; ethylenically unsaturated compounds having a carbonyl group such as diacetone acrylamide, methyl vinyl ketone, phenyl vinyl ketone, ethyl vinyl ketone, n-propyl vinyl ketone, isopropyl vinyl ketone, n-butyl vinyl ketone, tert-butyl vinyl ketone, etc., and light stabilizers having free radical polymerizability such as 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate; etc.

[0099] [1-1-6. Other compound (a6)]

[0100] Examples of the other compound (a6) include a polymerization initiator, a chain transfer agent, and a reactive emulsifier used in the synthesis process of the copolymer (A).

[0101] Regarding the structure derived from the other compound (a6) in the copolymer (A), it is different from the structural units derived from the monomers (a1) to (a5), and there may be no such corresponding relationship between the structures of other compounds such as the polymerization initiator and the chain transfer agent and the structure derived from the other compound (a6) in the copolymer (A). These compounds will be described in the manufacturing method of the copolymer (A) described later.

[0102] [1-1-7. Content of structural units derived from each monomer]

[0103] In this embodiment, the content ratio of each structural unit in the copolymer (A) is regarded as the same as the content ratio of each monomer in the total amount of monomer components used in the production of the copolymer (A).

[0104] The copolymer (A) preferably contains structural units derived from monomers (a1) to (a4) in a total amount of 90% by mass or more, more preferably 95% by mass or more, and still more preferably 97% by mass or more.

[0105] By containing structural units derived from monomers (a1) to (a4) in a total amount of 90% by mass or more, the copolymer (A) can suppress the increase in the glass transition temperature of the copolymer (A) and improve the adhesiveness, wettability, and adhesion strength of the adhesive layer.

[0106] The content of the structural unit derived from monomer (a1) relative to the copolymer (A) is preferably 82% by mass or more, more preferably 84% by mass or more, and still more preferably 86% by mass or more.

[0107] By making the content of the structural unit derived from monomer (a1) relative to the copolymer (A) 82% by mass or more, the increase in the glass transition temperature of the copolymer (A) can be suppressed, and the adhesiveness, wettability, and adhesion strength of the adhesive layer can be improved.

[0108] The content of the structural unit derived from monomer (a1) relative to the copolymer (A) is preferably 98% by mass or less, more preferably 96% by mass or less, and still more preferably 94% by mass or less.

[0109] By making the content of the structural unit derived from monomer (a1) relative to the copolymer (A) 98% by mass or less, an adhesive layer can be obtained that moderately maintains the polarity of the copolymer (A) and the cohesive force of the adhesive layer and has high adhesiveness not only at room temperature but also at high and low temperatures.

[0110] The content of the structural unit derived from monomer (a2) relative to the copolymer (A) is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and still more preferably 3.0% by mass or more.

[0111] By making the content of the structural unit derived from monomer (a2) relative to the copolymer (A) 1.0% by mass or more, the cohesive force of the adhesive layer can be improved and the holding force at high temperatures can be improved.

[0112] The content of the structural unit derived from monomer (a2) relative to the copolymer (A) is preferably 12% by mass or less, more preferably 10% by mass or less, and still more preferably 8.0% by mass or less.

[0113] By making the content of the structural unit derived from the monomer (a2) 12% by mass or less relative to the copolymer (A), an increase in the glass transition temperature of the copolymer (A) can be suppressed, and the adhesiveness, wettability, and adhesion strength of the adhesive layer can be improved.

[0114] The content of the structural unit derived from the monomer (a3) is 0.1% by mass or more, preferably 0.15% by mass or more, more preferably 0.20% by mass or more relative to the copolymer (A). The content of the structural unit derived from the monomer (a3) can be 0.5% or more, or can be 1.0% or more.

[0115] By making the content of the structural unit derived from the monomer (a3) 0.1% by mass or more, an adhesive layer that moderately maintains the cohesion of the adhesive layer and has high adhesiveness not only at normal temperature but also at high and low temperatures can be obtained.

[0116] The content of the structural unit derived from the monomer (a3) is 5.0% by mass or less, preferably 3.0% by mass or less, more preferably 2.0% by mass or less relative to the copolymer (A). The content of the structural unit derived from the monomer (a3) can be 1.5% by mass or less.

[0117] By making the content of the structural unit derived from the monomer (a3) 5.0% by mass or less, a decrease in the reactivity with the crosslinking agent (B) described later can be suppressed, thereby improving the cohesion of the adhesive layer and the holding power at high temperatures.

[0118] The content of the structural unit derived from the monomer (a4) is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and further preferably 3.0% by mass or more relative to the copolymer (A).

[0119] By making the content of the structural unit derived from the monomer (a4) 1.0% by mass or more, the cohesion of the adhesive layer can be improved, and the holding power at high temperatures can be improved.

[0120] The content of the structural unit derived from the monomer (a4) is preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, and particularly preferably 5.0% by mass or less relative to the copolymer (A).

[0121] By making the content of the structural unit derived from the monomer (a4) 20% by mass or less, an adhesive layer that moderately maintains the polarity of the copolymer (A) and the cohesion of the adhesive layer and has high adhesiveness not only at normal temperature but also at high and low temperatures can be obtained.

[0122] [1-1-8. Glass transition temperature of copolymer (A)]

[0123] The glass transition temperature (Tg) of the copolymer (A) is preferably -80 °C or higher, more preferably -65 °C or higher, and still more preferably -55 °C or higher.

[0124] By setting the glass transition temperature (Tg) of the copolymer (A) to -80 °C or higher, the cohesive force of the adhesive can be increased, and more excellent retention at high temperatures can be imparted to the adhesive layer.

[0125] The glass transition temperature (Tg) of the copolymer (A) is preferably 30 °C or lower, more preferably 0 °C or lower, still more preferably -20 °C or lower, and particularly preferably -35 °C or lower.

[0126] By setting the glass transition temperature (Tg) of the copolymer (A) to 30 °C or lower, the wettability of the adhesive composition described later can be improved, and the adhesion of the adhesive layer to the substrate can be improved. In addition, the flexibility of the adhesive layer can be increased, and the adhesiveness of the adhesive layer during dry use can be increased.

[0127] Tg is a theoretical value calculated from the structural units derived from each monomer constituting the polymer and their ratios by the FOX formula shown below.

[0128] 1 / T = W1 / T1 + W2 / T2 + W3 / T3 + … + Wn / Tn

[0129] T (K) = Tg (°C) + 273 °C, where T is the value representing the glass transition temperature of the copolymer (A) in absolute temperature.

[0130] Wn is the mass fraction (≤1) of each structural unit, and Tn is the glass transition temperature (absolute temperature) of the homopolymer of the monomer that is the source of each structural unit.

[0131] [1-1-9. Method for Producing Copolymer (A)]

[0132] The method for producing the copolymer (A) is not particularly limited. Monomers that are the sources of the respective structural units constituting the copolymer (A) can be polymerized as monomers. For some or all of the structural units, functional groups can also be introduced after polymerizing other monomers to obtain the target structural units.

[0133] As a method for producing the copolymer (A), for example, a method of emulsion-polymerizing monomers in an aqueous medium using a polymerization initiator can be mentioned. In the case of using emulsion polymerization, a liquid containing the copolymer (copolymer dispersion), that is, an emulsion, containing the copolymer (A) and the aqueous medium can be obtained. The copolymer (A) is dispersed in the aqueous medium as emulsion particles.

[0134] In polymerization, a chain transfer agent can be used to control the molecular weight and its distribution of the copolymer within an appropriate range. An emulsifier can be used to emulsify the monomers. The monomers can be charged into the reactor in their total amounts in advance. In order to obtain uniform particles, a mixture containing all types of monomers for forming the structural units of the copolymer (A) can be continuously or intermittently supplied while polymerization is carried out. The polymerization temperature is not particularly limited, preferably 5 to 100 °C, more preferably 50 to 90 °C.

[0135] The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of the hydrophilic solvent include methanol, ethanol, isopropyl alcohol, and N-methylpyrrolidone. From the viewpoint of polymerization stability, the aqueous medium is preferably water. It should be noted that as long as the polymerization stability is not impaired, an aqueous medium in which a hydrophilic solvent is added to water can also be used as the aqueous medium.

[0136] Examples of the polymerization initiator 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 tert-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide. These polymerization initiators can be used alone or in combination. The usage amount of the polymerization initiator is preferably 0.1 to 2% by mass based on the total amount of the monomers.

[0137] In addition, if necessary, a reducing agent can be used together with these polymerization initiators. Examples of such a reducing agent include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and metal formaldehyde sulfoxylate, and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulphite, and sodium pyrosulfite.

[0138] Examples of the chain transfer agent include, but are not limited to, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl mercaptoacetate, 2-mercaptoethanol, β-mercaptopropionic acid, methanol, n-propanol, isopropyl alcohol, tert-butanol, and benzyl alcohol. The chain transfer agent can be used alone or in combination of two or more.

[0139] If the usage amount of the chain transfer agent is small, the cohesion of the adhesive increases and the holding force at high temperature increases. If the usage amount is large, the cohesion of the adhesive decreases and the adhesive force of the adhesive layer increases.

[0140] The usage amount of the chain transfer agent is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, further preferably 0.50% by mass or less, and particularly preferably 0.30% by mass or less based on the copolymer (A).

[0141] By setting the amount of the chain transfer agent to 5.0% by mass or less, the retention force of the adhesive layer at high temperatures can be improved.

[0142] In addition, by not using a chain transfer agent, that is, by setting the content of the structural unit derived from the chain transfer agent in the copolymer (A) to 0% by mass, the odor of the adhesive composition and the adhesive tape produced by coating the adhesive composition on a substrate can be reduced.

[0143] The emulsifier is not particularly limited. Specifically, examples include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene nonylphenyl ether, cationic surfactants such as cetyltrimethylammonium bromide and laurylpyridinium chloride, amphoteric surfactants such as lauryl betaine, and other reactive surfactants. These surfactants can be used alone or in combination of two or more.

[0144] 〔1-2. Crosslinking agent (B)〕

[0145] At least one of the crosslinking agent (B) is a polyepoxide (a compound having two or more epoxy groups). It should be noted that the epoxy group can be a part of the glycidyl group. The polyepoxide can impart high adhesive force and cohesion by the adhesive at normal temperature and high temperature. The crosslinking agent (B) is preferably a water-soluble or water-dispersible compound.

[0146] Compounds other than the polyepoxide can also be used in combination with the crosslinking agent (B).

[0147] As polyepoxides, examples include bisphenol A - epichlorohydrin type epoxy resins, sorbitol polyglycidyl ethers (for example, "DENACOL (registered trademark, the same hereinafter) EX-611", "DENACOL EX-612", "DENACOL EX-614", "DENACOL EX-614B", "DENACOL EX-622", etc. manufactured by Nagase ChemteX Corporation), polyglycerol polyglycidyl ethers (for example, "DENACOL EX-512", "DENACOL EX-521", etc. manufactured by Nagase ChemteX Corporation), pentaerythritol polyglycidyl ethers (for example, "DENACOL EX-411", etc. manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ethers (for example, "DENACOL EX-421", etc. manufactured by Nagase ChemteX Corporation), glycerol polyglycidyl ethers (for example, "DENACOL EX-313", "DENACOL EX-314", etc. manufactured by Nagase ChemteX Corporation), trimethylolpropane polyglycidyl ethers (for example, "DENACOL EX-321", etc. manufactured by Nagase ChemteX Corporation), resorcinol diglycidyl ether (for example, "DENACOL EX-201", etc. manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (for example, "DENACOL EX-211", etc. manufactured by Nagase ChemteX Corporation), 1,6-Hexanediol diglycidyl ether (such as "DENACOL EX-212" manufactured by Nagase ChemteX Corporation, etc.), hydrogenated bisphenol A diglycidyl ether (such as "DENACOL EX-252" manufactured by Nagase ChemteX Corporation, etc.), ethylene glycol diglycidyl ether (such as "DENACOL EX-810", "DENACOL EX-811" manufactured by Nagase ChemteX Corporation, etc.), diethylene glycol diglycidyl ether (such as "DENACOL EX-850", "DENACOL EX-851" manufactured by Nagase ChemteX Corporation, etc.), polyethylene glycol diglycidyl ether (such as "DENACOL EX-821", "DENACOL EX-830", "DENACOL EX-832", "DENACOL EX-841", "DENACOL EX-861" manufactured by Nagase ChemteX Corporation, etc.), propylene glycol diglycidyl ether (such as "DENACOL EX-911" manufactured by Nagase ChemteX Corporation, etc.), polypropylene glycol diglycidyl ether (such as "DENACOL EX-941", "DENACOL EX-920", "DENACOL EX-931" manufactured by Nagase ChemteX Corporation, etc.), diglycidylaniline, diglycidylamine, N,N,N′,N′-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N′-diglycidylaminomethyl)cyclohexane, etc. Among them, a water-soluble type is preferred.,

[0148] The epoxy equivalent weight (molecular weight per 1 epoxy group) of the polyepoxide is preferably 70 or more, more preferably 100 or more, and still more preferably 120 or more. This is to suppress steric hindrance in the crosslinking reaction with the copolymer (A) and increase the crosslinking reaction rate and crosslinking density.

[0149] The epoxy equivalent weight (molecular weight per 1 epoxy group) of the polyepoxide is preferably 700 or less, more preferably 400 or less, still more preferably 300 or less, and particularly preferably 200 or less. This is to increase the crosslinking density in the crosslinking reaction with the copolymer (A).

[0150] [1-3. Quantitative relationship between the copolymer (A) and the crosslinking agent (B)]

[0151] In the adhesive composition, with respect to 100 parts by mass of the copolymer (A), the content of the crosslinking agent (B) is preferably 0.010 part by mass or more, more preferably 0.020 part by mass or more, and still more preferably 0.050 part by mass or more. This is because the crosslinking density between particles increases, the cohesion of the adhesive obtained from the adhesive composition improves, and the strength of the adhesive layer improves.

[0152] In the adhesive composition, with respect to 100 parts by mass of the copolymer (A), the content of the crosslinking agent (B) is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 3.0 parts by mass or less, and particularly preferably 1.0 part by mass or less. This is because the flexibility of the adhesive layer improves, and stronger adhesive force can be obtained at normal temperature and high temperature.

[0153] 〔1-4. Aqueous medium〕

[0154] The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of the hydrophilic solvent 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 the copolymer (A) or a different composition.

[0155] 〔1-5. Other additives〕

[0156] Additives can be appropriately included in the adhesive composition as needed. The timing of adding the additives is not particularly limited. The additives can be added simultaneously with or after the mixing of the copolymer (A) and the crosslinking agent (B). In addition, the additives can be pre-added to the solution or dispersion of either one or both of them before the mixing of the copolymer (A) and the crosslinking agent (B). Examples of the additives include pH adjusters and tackifiers. In addition, plasticizers, antioxidants, fillers, pigments, colorants, wetting agents, defoamers, thickeners, etc. can be appropriately used as additives.

[0157] As the pH adjuster, general inorganic acids, organic acids and other acidic substances or their salts, zwitterionic salts such as amino acids can be used. As the pH adjuster of organic acids, for example, 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, abietic acid, etc. can be cited. As the pH adjuster of inorganic acids, boric acid, phosphoric acid, hydrochloric acid, nitric acid, nitrous acid, sulfuric acid, sulfurous acid, etc. can be cited. Further, as the salts of acidic substances, salts of the above organic acids or inorganic acids with sodium, potassium, ammonia, aminoethanol, diethanolamine, triethanolamine, etc. can be cited. In addition, as the pH adjuster of amino acids, glycine, glycylglycine, asparagine, aspartic acid, alanine, phenylalanine, arginine, glutamine, glutamic acid, etc. can be cited. These pH adjusters can be used alone or in combination of two or more.

[0158] As the tackifier, for example, rosin resin, rosin ester resin, hydrogenated rosin resin, polymerized rosin resin, α-pinene resin, β-pinene resin, terpene phenol resin, C5 fraction-based petroleum resin, C9 fraction-based petroleum resin, C5 fraction / C9 fraction-based petroleum resin, dicyclopentadiene-based petroleum resin, alkylphenol formaldehyde resin, xylene resin, coumarone resin, coumarone indene resin, etc. can be cited. The tackifier can be used alone or in combination of two or more.

[0159] [1-6. Content of each component of the adhesive composition]

[0160] The non-volatile component concentration of the adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 40% by mass or more.

[0161] By setting the non-volatile component concentration of the adhesive composition to 20% by mass or more, more adhesive layers can be formed with a smaller coating amount of the adhesive composition. In addition, the drying time of the coated adhesive composition becomes shorter and the productivity is improved.

[0162] The non-volatile component concentration of the adhesive composition is preferably 75% by mass or less, more preferably 65% by mass or less.

[0163] By setting the non-volatile component concentration of the adhesive composition to 75% by mass or less, the gelation of the copolymer (A) in the adhesive composition can be suppressed.

[0164] In 100% by mass of the non-volatile components of the adhesive composition, the total content ratio of the copolymer (A) and the crosslinking agent (B) is preferably 50% by mass or more, more preferably 60% by mass or more, and further preferably 70% by mass or more.

[0165] By making the total content rate of the copolymer (A) and the crosslinking agent (B) 50% by mass or more in 100% by mass of the nonvolatile components of the adhesive composition, the adhesive force and the holding force of the adhesive layer, particularly the holding force at high temperatures, are improved.

[0166] Relative to 100% by mass of the nonvolatile components of the adhesive composition, the total content rate of the copolymer (A) and the crosslinking agent (B) is preferably 95% by mass or less, more preferably 90% by mass or less.

[0167] By making the total content rate of the copolymer (A) and the crosslinking agent (B) 95% by mass or less in 100% by mass of the nonvolatile components of the adhesive composition, the adhesive force and the holding force of the adhesive layer, particularly the adhesive force at normal temperature and high temperatures, are improved.

[0168] 〔1-7. Kit for preparing the adhesive composition〕

[0169] The adhesive composition of the present embodiment can be stored as a multi-dose kit in which the components of the adhesive composition are divided into a plurality of additives so that the above-mentioned adhesive composition is obtained by mixing the plurality of additives.

[0170] For example, a kit containing a copolymer-containing liquid containing the above-mentioned copolymer (A) and an aqueous medium and the above-mentioned crosslinking agent (B) can be prepared in advance, and when using the adhesive composition, the copolymer dispersion liquid is mixed with the crosslinking agent (B) to prepare the adhesive composition.

[0171] The copolymer-containing liquid may be a copolymer dispersion liquid in which the copolymer (A) is dispersed in an aqueous medium.

[0172] 〔1-8. Copolymer-containing liquid〕

[0173] The copolymer-containing liquid containing the above-mentioned copolymer (A) and an aqueous medium can also be stored and circulated in the state of the copolymer-containing liquid.

[0174] By mixing the above-mentioned copolymer-containing liquid with the above-mentioned crosslinking agent (B), the adhesive composition of the present invention can be prepared.

[0175] <2. Adhesive tape>

[0176] 〔2-1. Structure of the adhesive tape〕

[0177] As a representative use of the adhesive composition of the present invention, there is an adhesive tape. The adhesive tape of the present embodiment includes a base material and an adhesive layer formed on the surface of the base material. The adhesive layer may be formed only on one surface of the base material or on both surfaces. In addition, the adhesive layer of the adhesive tape of the present invention can be protected by a known release liner such as release paper or release PET.

[0178] The material of the base material is not particularly limited, and examples thereof include paper, plastic, cloth, metal, etc. In addition, the base material may be a film, a woven fabric, or a non-woven fabric, and there is no particular limitation, but a non-woven fabric is preferred. This is because the adhesive composition penetrates into the base material, and the bonding strength between the adhesive layer and the base material is improved. It should be noted that the "base material" in the present invention refers to the part that is attached to the adherend together with the adhesive layer when the adhesive tape of the present invention is used for the adherend, and does not include a release liner such as a release paper that is peeled off when the adhesive tape is used.

[0179] The thickness of the base material can be, for example, 10 to 200 μm or less, or 20 to 100 μm or less.

[0180] The adhesive layer contains an adhesive that is a cured product of the aforementioned adhesive composition. In addition to this adhesive, the adhesive layer may also contain additives and the like. As described later, in the adhesive tape produced by coating the adhesive composition on the base material, the non-volatile components of the adhesive composition are contained in the adhesive layer.

[0181] The thickness of the adhesive layer is preferably 10 μm or more, more preferably 30 μm or more, and still more preferably 50 μm or more.

[0182] By setting the thickness of the adhesive layer to 10 μm or more, the adhesive layer can be sufficiently deformed to follow the surface of the adherend.

[0183] The thickness of the adhesive layer is preferably 200 μm or less, more preferably 100 μm or less.

[0184] By setting the thickness of the adhesive layer to 200 μm or less, cohesive failure of the adhesive layer can be suppressed.

[0185] Hereinafter, the preferred thickness in the case of an adhesive tape, that is, a double-sided tape, in which adhesive layers are formed on both surfaces of the base material will be described.

[0186] In this adhesive tape, the total thickness of the base material and the adhesive layer formed on the surface of the base material is preferably 50 μm or more, more preferably 80 μm or more, and still more preferably 100 μm or more.

[0187] By setting the total thickness of the base material and the adhesive layer formed on the surface of the base material to 50 μm or more, the adhesive layer can be sufficiently deformed to follow the surface of the adherend.

[0188] In this adhesive tape, the total thickness of the base material and the adhesive layer formed on the surface of the base material is preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less.

[0189] By making the total thickness of the base material and the adhesive layer formed on the surface of the base material 300 μm or less, cohesive failure of the adhesive layer can be suppressed.

[0190] The adhesive layer may include two or more adhesive layers.

[0191] In addition, besides the base material and the adhesive layer, the adhesive tape of the present invention may also have other layers (such as an intermediate layer, a primer layer, etc.) within the scope not impairing the effects of the invention.

[0192] [2-2. Method for manufacturing the adhesive tape]

[0193] The method for manufacturing the adhesive tape includes: a step of coating the adhesive composition on one side or both sides of the base material; after removing the aqueous medium from the adhesive composition coated on the base material to form an adhesive composition coated layer, curing the adhesive composition coated layer to form an adhesive layer. During coating, in order to adjust the viscosity of the adhesive composition, an aqueous medium or a thickener, etc. may be appropriately added to the adhesive composition. In the case of coating the adhesive composition on both sides, it may be coated side by side or coated on both sides at once. The adhesive composition may be continuously coated on the base material or intermittently coated.

[0194] The coating amount of the adhesive composition is not particularly limited, and is preferably 10 - 500 g / m 2 . The drying temperature of the adhesive composition coated on the base material is not particularly limited, and is preferably 20 - 160 °C. This is because an adhesive layer with sufficient adhesive force and cohesive force can be obtained.

[0195] In the step of forming the adhesive layer, for example, it is preferred to dry the adhesive composition coated on the base material at 100 °C for 3 minutes to form an adhesive composition coated layer, and then leave it standing at 40 °C for 3 days to cure the adhesive composition coated layer.

[0196] <3. Uses of the adhesive composition and the adhesive tape>

[0197] Here, as one of the preferred uses of the adhesive composition of the present invention, the adhesive tape has been described, but the uses of the adhesive composition of the present invention are not limited thereto. For example, the adhesive composition of the present invention can be directly coated on a member and adhered to other members without using an adhesive tape. In addition, as the use of the bonding method using the adhesive tape of the present invention, for example, there are uses in electrical products, automobiles, building components, toys, etc. The adherend of the adhesive tape is not particularly limited, and it is particularly useful in the case of plastic components such as polypropylene, and metal components such as SUS and aluminum.

[0198] Examples

[0199] Hereinafter, examples and comparative examples of the present invention will be described. However, the present invention is not limited to these examples.

[0200] <1. Preparation of the adhesive composition>

[0201] In a polymerization apparatus equipped with a stirrer, a thermometer, and a reflux condenser, 23 parts by mass of mixed ion-exchanged water and 0.10 part by mass of an ammonium polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate, which is a reactive anionic emulsifier (product name: Aqualon KH-10 (アクアロンKH-10), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), were mixed, and the temperature was raised to 80°C under a nitrogen atmosphere. While stirring the mixture in the polymerization apparatus, the temperature was maintained at 80°C, and 2.0 parts by mass of a 5.0% by mass aqueous potassium persulfate solution as a polymerization initiator was added. A monomer emulsion containing 50 parts by mass of ion-exchanged water, 1.0 part by mass of an ammonium polyoxyethylene alkyl ether sulfate, which is a non-reactive nonionic emulsifier (product name: HITENOL LA-16 (ハイテノールLA-16), manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), as an emulsifier, and a total of 100 parts by mass of a monomer and a chain transfer agent was added dropwise to the above mixture to which the polymerization initiator had been added over 4 hours. The types of the monomer and the chain transfer agent added dropwise here are shown in Table 1-1 (Examples 1 to 5), Table 1-2 (Examples 6 to 10), and Table 2 (Comparative Examples 1 to 5). Here, the content ratio of each component in the total of 100 parts by mass of the monomer and the chain transfer agent added dropwise is shown in the left column of each example and comparative example in Table 1-1 (Examples 1 to 5), Table 1-2 (Examples 6 to 10), and Table 2 (Comparative Examples 1 to 5). At the same time as starting the addition of the monomer emulsion, 20 parts by mass of a 2.5% by mass aqueous potassium persulfate solution was added dropwise over 4 hours.

[0202] After completion of the addition dropwise, the reaction was carried out at 80°C for 2 hours. Then, the mixture in the polymerization apparatus was cooled to 25°C. Ammonia water was added as a neutralizing agent to adjust the pH to 8.5, and an emulsion containing emulsion particles containing copolymer (A) and water was obtained.

[0203] Furthermore, 25 parts by mass of a polymerized rosin ester resin (product name: SUPER ESTERE-865NT (スーパーエステルE--865NT), manufactured by Arakawa Chemical Industries, Ltd.) as a thickener and 2.0 parts by mass of Primal ASE-60 (プライマルASE-60) (manufactured by Dow Chemical Company) as a thickening agent were added to the obtained emulsion.

[0204] Then, a crosslinking agent (B) in the types and amounts shown in the left column of Table 1-1 (Examples 1 to 5), Table 1-2 (Examples 6 to 10), and Table 2 (Comparative Examples 1 to 5) was added in each example and comparative example to obtain an adhesive composition.

[0205] In Table 1-1 (Examples 1 to 5), Table 1-2 (Examples 6 to 10), and Table 2 (Comparative Examples 1 to 5), the content (parts by mass) of the crosslinking agent (B) in the adhesive composition means "the content (parts by mass) of the crosslinking agent (B) in the adhesive composition relative to 100 parts by mass of the copolymer (A)".

[0206] <2. Production of the adhesive tape>

[0207] The adhesive composition obtained in each example and comparative example was coated on the release surface of the release paper. A doctor blade with a coating width of 15 cm was used as the coater. The coated adhesive composition was dried at 100 °C for 3 minutes to remove the aqueous medium from the adhesive composition, and an adhesive composition coating layer with a film thickness of 60 μm was formed on the release surface. The adhesive composition coating layer on the release surface was transferred to both sides of a nonwoven fabric cut into A4 size with a thickness of 40 μm and a basis weight of 14 g / m 2 (substrate: made of rayon). The adhesive composition coating layer transferred to the nonwoven fabric was allowed to stand at 40 °C for 3 days to form an adhesive layer. The total thickness of the nonwoven fabric as the substrate and the adhesive layers provided on both sides thereof was 130 μm. In this way, an adhesive tape having a substrate and an adhesive layer formed on the surface of the substrate was obtained. It should be noted that in order to avoid foreign matter from adhering to the adhesive layer, the release paper was not peeled off after transfer.

[0208] <3. Evaluation of the adhesive tape>

[0209] The adhesive tapes produced in each example and comparative example were evaluated as follows in Evaluations 1 to 5.

[0210] The evaluation results of Evaluations 1 to 4 are shown in Table 1-1 (Examples 1 to 5), Table 1-2 (Examples 6 to 10), and Table 2 (Comparative Examples 1 to 5).

[0211] It should be noted that in the following description, the operations in each example and comparative example are common unless otherwise specified.

[0212] 〔3-1. Evaluation 1: Measurement of initial adhesiveness〕

[0213] The release paper on one side of the adhesive tape was peeled off, and a 25-μm-thick polyethylene terephthalate (PET) film was pasted. The PET film with the adhesive tape pasted thereon was cut into 25 mm × 250 mm. Further, the release paper on the opposite side of the adhesive tape was peeled off halfway along the length direction and cut out, and then adhered to a polypropylene (PP) plate to produce an evaluation sample.

[0214] The adhesion was carried out by making a 2-kg roller reciprocate once in an atmosphere at 23 °C. Hereinafter, the atmosphere temperature at the time of adhesion when producing the evaluation sample is referred to as the pasting temperature. (Pasting temperature in Evaluation 1: 23 °C)

[0215] The portion of the adhesive tape in contact with the polypropylene plate in the sample for evaluation is a rectangle of 25 mm × 125 mm. Neither end of the contact portion overlaps with the end of the polypropylene plate. That is, in this state, half of one end side in the length direction of the adhesive tape is in contact with the polypropylene plate, and the other half is in contact with the release paper.

[0216] After preparing the sample for evaluation, it is left standing for 30 minutes in an atmosphere at a temperature of 23°C. Hereinafter, the atmospheric temperature during standing after preparing the sample for evaluation is referred to as the standing temperature.

[0217] (Standing temperature in Evaluation 1: 23°C)

[0218] Then, the following steps are measured in an atmosphere at a temperature of 23°C. Hereinafter, the measurement temperature of the sample for evaluation is referred to as the measurement temperature. (Measurement temperature in Evaluation 1: 23°C)

[0219] The test is a so-called 180° peel test. The boundary between the portion of the adhesive tape of the sample for evaluation attached to the polypropylene plate and the non-attached portion is folded 180° as the fold line. One end of the non-pasted side (the folded side) of the adhesive tape is grasped by the upper chuck of the testing machine. One end of the polypropylene plate opposite to the upper chuck across the fold line is clamped by the lower chuck.

[0220] In this state, the adhesive tape is peeled off from the polypropylene plate at a speed of 200 mm / min to obtain a graph of peel length (mm) - peel force (N). In the obtained graph, the average value of the peel force (N) in the range of peel length from 25 to 100 mm (the value obtained by dividing the area of the graph in the range of peel length from 25 to 100 mm by the peel length) is calculated, and this value is used as the initial adhesion force (N / 25 mm).

[0221] [3-2. Evaluation 2: Measurement of adhesion force in a high-temperature environment]

[0222] Except that the standing temperature is 70°C and the measurement temperature is 70°C, the adhesion force (N / 25 mm) in a high-temperature environment is measured according to the same steps as in the above "Evaluation 1".

[0223] [3-3. Evaluation 3: Measurement of adhesion force in a low-temperature environment]

[0224] The polypropylene (PP) plate in "Evaluation 1" is changed to a SUS plate (SUS#304), the pasting temperature is set to -20°C, the standing temperature is set to -20°C, the measurement temperature is set to -20°C, and the sample for evaluation is left standing using a constant-temperature bath at -20°C. Except for this, the adhesion force (N / 25 mm) in a high-temperature environment is measured according to the same steps as in the above "Evaluation 1".

[0225] [3-4. Evaluation 4: Measurement of High Temperature Retention Force]

[0226] Peel off the release paper on one side of the adhesive double-sided tape and paste a polyethylene terephthalate (PET) film with a thickness of 25 μm. On the other side of the adhesive tape, peel off the release paper from one end in the longitudinal direction by 25 mm, and attach a SUS plate (SUS #304) in such a way as to completely cover the part where the release paper has been peeled off, to produce a sample for evaluation. That is, in the sample for evaluation, the range where the adhesive tape is attached to the SUS plate is a square of 25 mm × 25 mm. The attachment is carried out by making a 2 kg roller reciprocate once in an atmosphere of 23°C. In addition, at this time, the part of the SUS plate where only the adhesive tape is not attached, on the extension line of one end of the adhesive tape attached to the SUS plate, is set as the SUS plate side chuck part.

[0227] Leave the sample for evaluation in a constant temperature bath at 80°C for 30 minutes. Then, in the constant temperature bath at 80°C, grasp the SUS plate side chuck part of the sample for evaluation with a chuck, hang a 500 g weight at one end in the longitudinal direction of the side of the adhesive tape where the SUS plate is not attached, and leave it for 24 hours. Then, measure the distance (mm) by which the adhesive tape deviates from the SUS plate in the vertical direction.

[0228] [3-5. Evaluation 5: Measurement of Odor]

[0229] To verify the secondary effect of this embodiment, the odor of the adhesive tape is measured. Cut the double-sided tape into 40 mm × 100 mm, peel off the release papers on both sides, and put it into a glass bottle with a volume of 70 cc and seal it. Leave the glass bottle in a constant temperature bath at 80°C for 1 hour. Then, after the temperature is lowered to 60°C, slightly open the lid of the glass bottle, smell the odor of the internal gas, and compare the intensity of the odor using the butanol odor intensity standard odor liquid (The Japan Odor and Fragrance Environment Association, a public interest incorporated association). Evaluate as 〇 if the odor is weaker than the standard sample with an odor intensity of 3, and evaluate as × if the odor is the same as or stronger than the standard sample with an odor intensity of 3.

[0230] <4. Evaluation Results>

[0231] [4-1. Evaluations 1 to 4]

[0232] As shown in Table 1-1 (Examples 1 to 5) and Table 1-2 (Examples 6 to 10), it can be seen that the adhesive tape made of the adhesive composition of the examples forms an adhesive layer that exhibits strong adhesive force not only at normal temperature, but also at high temperature and low temperature, and further has high retention force at high temperature.

[0233] On the other hand, in the adhesive tapes of Comparative Example 1 and Comparative Example 2 produced using an adhesive composition that does not contain the structural unit (a3) derived from (meth)acrylonitrile in the copolymer (A), at least one of the high-temperature adhesiveness and the low-temperature adhesiveness is insufficient. In Comparative Example 2, the blending amount of the chain transfer agent in the adhesive composition was increased, but the improvement of the low-temperature adhesiveness was not achieved. On the other hand, in the adhesive tape of Comparative Example 3 produced using an adhesive composition that excessively contains the structural unit (a3) derived from (meth)acrylonitrile, the high-temperature holding power is significantly poor, and the high-temperature adhesiveness and the low-temperature adhesiveness are also insufficient.

[0234] From this, it can be understood that in the copolymer (A), the object of the present invention cannot be achieved in the constitution that does not contain the structural unit (a3) derived from (meth)acrylonitrile and the constitution that excessively contains it.

[0235] In the adhesive tape of Comparative Example 4 produced using an adhesive composition containing an alkyl (meth)acrylate (a2) having a glass transition temperature of 80°C or higher and not containing a homopolymer, the high-temperature adhesiveness is insufficient.

[0236] In the adhesive tape of Comparative Example 5 produced using an adhesive composition not containing the crosslinking agent (B), the high-temperature holding power is insufficient.

[0237] [4-2. Evaluation 5]

[0238] In Example 9 and Comparative Example 2 using dodecyl mercaptan as the chain transfer agent, the evaluation result of the measurement of the odor of the adhesive tape was "×".

[0239] In other Examples and Comparative Examples without using dodecyl mercaptan as the chain transfer agent, the evaluation results of the measurement of the odor of the adhesive tape were all "〇".

[0240] As shown in Evaluation 2 and 5 of Comparative Example 2, even in the case of not containing the structural unit derived from (meth)acrylonitrile (a3), by using a small amount of the chain transfer agent, the improvement effects of the high-temperature adhesiveness and the high-temperature holding power were confirmed, but the use of the chain transfer agent generated an odor.

[0241]

[0242]

[0243]

[0244] As described above, according to the present invention, it is possible to provide an adhesive composition that can form an adhesive layer that exhibits strong adhesive force not only at normal temperature but also at high temperature and low temperature, and further has high holding power at high temperature. In addition, according to the present invention, it is possible to provide an adhesive tape that exhibits strong adhesive force not only at normal temperature but also at high temperature and low temperature, and further has high holding power at high temperature.

Claims

1. An adhesive composition comprising a copolymer A, a crosslinking agent B, and an aqueous medium, wherein, the copolymer A has structural units derived from monomer a1, structural units derived from monomer a2, structural units derived from monomer a3, and structural units derived from monomer a4, the monomer a1 is an (alkyl) acrylate having a glass transition temperature of the homopolymer of -40°C or lower and having only one ethylenically unsaturated bond, the monomer a2 is an homopolymer having a glass transition temperature of 80°C or higher and being at least one selected from the group consisting of an (alkyl) acrylate having only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond, monomer a3 is (meth)acrylonitrile, the monomer a4 is a monomer having only one ethylenically unsaturated bond and a functional group that reacts with the epoxy group of the crosslinking agent B, the content of the structural units derived from the monomer a3 is 0.1% by mass or more and 5.0% by mass or less, at least one of the crosslinking agent B is a polyepoxide compound.

2. The adhesive composition according to claim 1, wherein, The monomer a4 has at least one selected from the group consisting of a carboxyl group, a hydroxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group.

3. The adhesive composition according to claim 1, wherein, The monomer a4 has a carboxyl group.

4. The adhesive composition according to claim 1, wherein, The monomer a4 includes a monomer having a carboxyl group and a monomer having a hydroxyl group.

5. The adhesive composition according to claim 1, wherein, The epoxy equivalent of the crosslinking agent B is 70 or more and 700 or less.

6. The adhesive composition according to claim 1, wherein, The total content of the copolymer A and the crosslinking agent B is 50% by mass or more based on 100% by mass of the non-volatile components of the adhesive composition.

7. An adhesive tape comprising a substrate and an adhesive layer formed on the substrate, wherein the adhesive layer contains a cured product of the adhesive composition according to any one of claims 1 to 6.

8. A method for manufacturing an adhesive tape, comprising: A step of coating the adhesive composition according to any one of claims 1 to 6 on a substrate; and a step of removing the aqueous medium from the adhesive composition coated on the substrate and curing it to form an adhesive layer.

9. A bonding method using the adhesive tape according to claim 7.

10. A kit for preparing an adhesive composition, the kit comprising: a liquid containing a copolymer containing a copolymer A and an aqueous medium, and a crosslinking agent B, Among them, the copolymer A has structural units derived from monomer a1, structural units derived from monomer a2, structural units derived from monomer a3, and structural units derived from monomer a4, the monomer a1 is an (alkyl) acrylate having a glass transition temperature of the homopolymer of -40°C or lower and having only one ethylenically unsaturated bond, the monomer a2 is an homopolymer having a glass transition temperature of 80°C or higher and being at least one selected from the group consisting of an (alkyl) acrylate having only one ethylenically unsaturated bond and a hydrocarbon having only one ethylenically unsaturated bond, monomer a3 is (meth)acrylonitrile, the content of the structural units derived from the monomer a3 is 0.1% by mass or more and 5.0% by mass or less, at least one of the crosslinking agent B is a polyepoxide compound.

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