Adhesive composition

Abstract

The present invention addresses the problem of providing an adhesive composition which ensures low-temperature curability and has excellent adhesiveness to greasy surfaces. The adhesive composition comprises (A) a ligninsulfonic acid salt, (B) a toughness improver, (C) an epoxy resin, and (D) an epoxy resin hardener.

Description

adhesive composition

[0001] The present invention relates to an adhesive composition useful for producing articles by structurally bonding various members, parts, etc. In particular, the present invention relates to an adhesive composition that has excellent fast curing properties at low temperatures, excellent adhesion to oily surfaces, and excellent adhesive strength properties, and is useful as a structural adhesive.

[0002] When manufacturing an article by structurally bonding various members, parts, etc. made of different materials, a method using an adhesive composition is known, and such adhesive compositions are widely known as structural adhesives. Structural adhesives are widely used in a wide range of fields, including automobiles, ships, aviation, space, civil engineering, and construction. In particular, in recent years, structural adhesives have been used in the automobile field during vehicle assembly as an alternative to conventional joining techniques such as welding, bolt-nut and rivet, or as a reinforcement technique for conventional joining techniques.

[0003] Patent Document 1 discloses a structural adhesive containing an epoxy resin, an imidazole compound, and an anti-rust pigment, which has excellent handling properties, adhesion, and rust prevention. Patent Document 2 discloses a one-component epoxy resin adhesive comprising a two-component mixed epoxy resin of bisphenol A epoxy resin and bisphenol F epoxy resin, a latent curing agent, crosslinked rubber microparticles with an average particle size of 0.05 to 0.5 μm, 1 to 5 parts by mass of a curing accelerator, and a thixotropic agent with an average particle size of 0.5 to 5 μm. This one-component epoxy resin adhesive is considered to be excellent as a highly reliable structural adhesive, exhibiting a high level of well-balanced tensile shear bond strength and peel bond strength, as well as high heat resistance. Patent Document 3 discloses a one-component epoxy resin composition containing a latent epoxy curing agent obtained by addition polycondensation of an alicyclic diamine amine and a (meth)acrylic acid alkyl ester, an epoxy resin, an inorganic filler, rubber particles, and a silane coupling agent. This one-component epoxy resin composition combines low-temperature curing properties and storage stability, exhibits excellent adhesion to metal materials, glass materials, ceramic materials, engineering plastic materials, etc., and is considered useful as a structural adhesive. Patent Document 4 discloses an epoxy resin composition comprising an epoxy resin, core-shell rubber particles, and a hollow polymer. This epoxy resin composition is capable of achieving good adhesive strength over a wide temperature range and is reliable in adhesion, making it useful as a structural adhesive composition for joining dissimilar materials. Patent Document 5 describes a thermosetting resin composition containing an epoxy resin, rubber particles having a core-shell structure, an epoxy silane coupling agent, and polybutadiene having epoxy groups at both ends. This thermosetting resin composition exhibits little decrease in adhesive strength even when placed under high-temperature and high-humidity conditions after application, making it useful as a structural adhesive.

[0004] JP 62-79282 A JP 2011-148867 A JP 2000-281759 A JP 2010-270198 A JP 2019-199606 A

[0005] Conventional adhesive compositions can ensure adhesion to oily surfaces when cured at high temperatures of 160°C or higher, but at low temperatures it is difficult to absorb oil from the surface of the adherend, and adhesion to oily surfaces cannot be fully ensured. Therefore, the problem that the present invention aims to solve is to provide an adhesive composition that ensures curing at low temperatures and has excellent adhesion to oily surfaces.

[0006] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following adhesive composition, and have thus completed the present invention. Specifically, the invention is as follows: [Item 1] An adhesive composition comprising (A) a lignin sulfonate, (B) a toughness imparting agent, (C) an epoxy resin, and (D) an epoxy resin curing agent. [Item 2] The adhesive composition according to Item 1, wherein the content of the (A) lignin sulfonate is 0.1% by mass or more and 25.0% by mass or less, based on 100% by mass of the total amount of the adhesive composition. [Item 3] The adhesive composition according to Item 1 or 2, wherein the content of the (A) lignin sulfonate is 0.1% by mass or more and 15.0% by mass or less, based on 100% by mass of the total amount of the adhesive composition. [Item 4] The adhesive composition according to any one of Items 1 to 3, wherein the (B) toughening agent comprises one or more selected from the group consisting of (b1) rubber particles, (b2) rubber-modified epoxy resin, (b3) block urethane resin, and (b4) urethane-modified epoxy resin. [Item 5] The adhesive composition according to any one of Items 1 to 4, wherein the (B) toughening agent is a urethane-based toughening agent comprising (b3) block urethane resin and / or (b4) urethane-modified epoxy resin. [Item 6] The adhesive composition according to any one of Items 1 to 5, wherein the (B) toughening agent comprises: (i) a rubber-based toughening agent comprising (b1) rubber particles and / or (b2) rubber-modified epoxy resin, and (ii) a urethane-based toughening agent comprising (b3) block urethane resin and / or (b4) urethane-modified epoxy resin. [Item 7] The adhesive composition according to item 6, wherein the content of the rubber-based toughening agent is 20.0% by mass or more and 50.0% by mass or less, and the content of the urethane-based toughening agent is 5.0% by mass or more and 20.0% by mass or less, relative to 100% by mass of the total amount of the adhesive composition. [Item 8] The adhesive composition according to any one of items 1 to 7, which is a structural adhesive. [Item 9] The adhesive composition according to any one of items 1 to 7, which is a one-component thermosetting adhesive.

[0007] The present invention can provide an adhesive composition that ensures low-temperature curing properties and has excellent adhesion to oily surfaces.

[0008] The adhesive composition of the present invention is an adhesive composition containing (A) a lignin sulfonate, (B) a toughening agent, (C) an epoxy resin, and (D) an epoxy resin curing agent. The adhesive composition of the present invention will be described in detail below.

[0009] [(A) Lignosulfonate] Examples of lignosulfonate include one or more salts selected from the group consisting of sodium, magnesium, calcium, ammonium, and the like of lignosulfonic acid. Lignosulfonate can be obtained, for example, by treating softwood or hardwood with a sulfite. Furthermore, lignosulfonate may be partially modified by desulfonation, oxidation, hydrolysis, demethylation, or the like. Furthermore, lignosulfonate may be one whose pH, etc., has been adjusted. The weight-average molecular weight of the lignosulfonate is not particularly limited. For example, it is 1,000 or more, preferably 1,200 or more, more preferably 1,500 or more, and for example, 30,000 or less, preferably 20,000 or less, more preferably 10,000 or less.

[0010] The content of each functional group in the lignin sulfonate is not particularly limited. The content of sulfonic acid groups in the lignin sulfonate is, for example, 0.05 mol or more, preferably 0.1 mol or more, and for example, 0.8 mol or less, preferably 0.7 mol or less, per mol of phenylpropane, which is the basic structure of lignin. The content of carboxyl groups in the lignin sulfonate is, for example, 0.005 mol or more, preferably 0.01 mol or more, and for example, 0.45 mol or less, preferably 0.4 mol or less, per mol of phenylpropane, which is the basic structure of lignin. The content of alcoholic OH groups in the lignin sulfonate is, for example, 0.1 mol or more, preferably 0.2 mol or more, and for example, 0.6 mol or less, preferably 0.5 mol or less, per mol of phenylpropane, which is the basic structure of lignin. The content of phenolic OH groups in the lignin sulfonate is, for example, 0.2 mol or more, preferably 0.3 mol or more, and for example, 0.7 mol or less, preferably 0.6 mol or less, per mol of phenylpropane, which is the basic structure of lignin.

[0011] Commercially available lignin sulfonates can be used. Examples of commercially available lignin sulfonates include "Sunex P321" (magnesium lignin sulfonate), "Sunex P252" (sodium lignin sulfonate), "Sunex P202" (calcium lignin sulfonate), "Sunex SCP" (modified magnesium-calcium lignin sulfonate), "Vaniol ODP" (modified sodium lignin sulfonate), "Vanilex HW" (high-purity partially desulfonated sodium lignin sulfonate), and "Vanilex" manufactured by Nippon Paper Industries Co., Ltd. N" (high-purity partially desulfonated sodium lignosulfonate), "Vanilex RN" (high-purity partially desulfonated sodium lignosulfonate), "Pearlex NP" (high-purity high-molecular-weight sodium lignosulfonate), and "Pearlex DP" (high-purity high-molecular-weight sodium lignosulfonate), etc.; "Sodium Lignin Sulfonate [L0098]," "Lignin (dealkalized) [L0045]," and "Lignin (alkalized) [L0082]," etc., manufactured by Tokyo Chemical Industry Co., Ltd.;Boreegaard's "V-Tec 30" (ammonium lignosulfonate), "Pionera DX1400" (sodium lignosulfonate), "Pionera DX2000" (sodium lignosulfonate), "Pionera DX3200" (sodium lignosulfonate), "Pionera DX4200" (sodium lignosulfonate), "Pionera DX5500" (sodium lignosulfonate), "Greensperse CA" (high-purity calcium lignosulfonate), "Greensperse S7" (high-purity modified sodium lignosulfonate), "Greensperse S9" (high-purity modified sodium lignosulfonate), "Borresperse CA" (high-purity calcium lignosulfonate), "Greensperse NA" (high-purity sodium lignosulfonate), "Borresperse NA" (sodium lignosulfonate), "Borresperse AM 320" (high-purity ammonium lignosulfonate), "Borresperse 3A" (high-purity modified sodium lignosulfonate), "Ultrazine NA" (high-purity modified sodium lignosulfonate), "Ufoxane 3A" (high-purity modified sodium lignosulfonate), "Marasperse AG" (high-purity modified sodium lignosulfonate), and "Vanisperse CB" (high-purity modified sodium lignosulfonate) can be used.

[0012] The content of the lignin sulfonate in the adhesive composition of the present invention is not particularly limited. The content of the lignin sulfonate, based on 100% by mass of the total amount of the adhesive composition, is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. For example, the content can be 25.0% by mass or less, preferably 20.0% by mass or less, more preferably 17.0% by mass or less, even more preferably 15.0% by mass or less, and even more preferably 10.0% by mass or less. If the content of the lignin sulfonate, based on 100% by mass of the total amount of the adhesive composition, is less than 0.1% by mass, problems with adhesion to oily surfaces may occur. If the content of the lignin sulfonate is more than 25.0% by mass, the effect of improving adhesion to oily surfaces may be reduced, resulting in cost problems.

[0013] [(B) Toughness-Promoting Agent] The toughness-promoting agent is not particularly limited as long as it can impart toughness and impact peel adhesion to the cured product of the adhesive composition. Examples include one or more selected from the group consisting of rubber, elastomer, compositions containing rubber and / or elastomer, and components modified with rubber and / or elastomer. In the present invention, the toughness-promoting agent preferably contains one or more selected from the group consisting of (b1) rubber particles, (b2) rubber-modified epoxy resin, (b3) block urethane resin, and (b4) urethane-modified epoxy resin. In the present invention, the toughness-promoting agent is preferably a urethane-based toughness-promoting agent containing (b3) block urethane resin and / or (b4) urethane-modified epoxy resin. In the present invention, the toughness imparting agent may contain both (i) a rubber-based toughness imparting agent containing (b1) rubber particles and / or (b2) a rubber-modified epoxy resin, and (ii) a urethane-based toughness imparting agent containing (b3) a block urethane-based resin and / or (b4) a urethane-modified epoxy resin.

[0014] <(b1) Rubber Particles> The rubber particles are not particularly limited as long as they have a number average particle diameter of, for example, 10 nm or more, and, for example, 1,000 nm or less, preferably 500 nm or less, and more preferably 400 nm or less. The number average particle diameter of the rubber particles can be determined, for example, by dynamic light scattering, electron microscopy, etc.

[0015] The rubber constituting the rubber particles is not particularly limited. For example, it may be one or more selected from the group consisting of butadiene acrylonitrile rubber (NBR), styrene butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), butyl rubber (IIR), butadiene rubber, block rubber, core-shell rubber (CSR), etc. In the present invention, it is preferable to use core-shell rubber (CSR) as the rubber.

[0016] The core-shell rubber (CSR) preferably comprises a core present inside the core-shell rubber, which accounts for, for example, 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, and for example, 99% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, based on 100% by mass of the total amount of the core-shell rubber, and a shell present outside the core, which accounts for, for example, 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and for example, 60% by mass or less, preferably 50% by mass or less, and more preferably 40% by mass or less, based on 100% by mass of the total amount of the core-shell rubber. Core-shell rubbers (CSR) in which the core is composed of crosslinked rubber and the shell is composed of a hard polymer shell are preferred, and core-shell rubbers (CSR) in which a polymer constituting the hard polymer shell is grafted onto a core composed of crosslinked rubber are more preferred.

[0017] The crosslinked rubber constituting the core has a solvent-insoluble content due to being crosslinked. The solvent-insoluble content (gel fraction) of the crosslinked rubber is not particularly limited. For example, the mass ratio of the MEK-insoluble matter remaining after immersion in methyl ethyl ketone at room temperature (25°C ± 15°C) for 24 hours and then centrifuging at 12,000 rpm for 1 hour to remove the soluble content and solvent is 100% by mass or less, 80% by mass or more, and preferably 90% by mass or more, based on the mass of the input sample.

[0018] The core-shell rubber (CSR) particles preferably have a core-shell structure comprising a crosslinked rubber particle core and a hard polymer shell. From the viewpoint of improving toughness, the core-shell rubber (CSR) is preferably a graft copolymer comprising a hard polymer shell obtained by graft polymerizing one or more vinyl monomers constituting the hard polymer shell in the presence of crosslinked rubber particles constituting the core, the core comprising one or more crosslinked rubber particles selected from the group consisting of butadiene rubber, butadiene-styrene rubber, butadiene butyl acrylate rubber, butyl acrylate rubber, organosiloxane rubber, acrylic rubber, etc. From the viewpoint of improving toughness, the graft polymerization is preferably carried out by emulsion polymerization.

[0019] When the crosslinked rubber particle core is composed of a vinyl-based monomer, the crosslinked rubber particle core may contain, for example, 50% by mass or more, preferably 70% by mass or more, of a vinyl-based monomer selected from the group consisting of at least a conjugated diene (such as butadiene), n-butyl acrylate, ethyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, etc., and may be copolymerized with 50% by mass or less of a copolymerizable vinyl-based monomer. Examples of the copolymerized vinyl monomer include at least one selected from the group consisting of aromatic vinyl monomers such as styrene, α-methylstyrene, p-methylstyrene, and divinylbenzene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; methacrylic acid monomers such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butylene glycol dimethacrylate; and acrylic acid monomers such as acrylic acid, methyl acrylate, butyl acrylate, glycidyl acrylate, hydroxybutyl acrylate, and phenoxyethyl acrylate.

[0020] The hard polymer shell can be formed from a monomer component containing 60% by mass or more of a monomer selected from the group consisting of at least one lower alkyl methacrylate, for example, methyl methacrylate, ethyl methacrylate, t-butyl methacrylate, etc., and including, for example, one or more copolymerizable monomers selected from the group consisting of styrene, vinyl acetate, vinyl chloride, methyl acrylate, ethyl acrylate, butyl acrylate, etc. The number average molecular weight of the hard polymer constituting the hard polymer shell can be, for example, 20,000 or more and 500,000 or less.

[0021] From the viewpoint of improving toughness, the rubber particles may have a glass transition temperature of 0° C. or lower, preferably less than −20° C., and more preferably less than −50° C. When the rubber particles are core-shell polymers (CSR), the glass transition temperature of the core may be 0° C. or lower, preferably less than −20° C., and more preferably less than −50° C., and the glass transition temperature of the shell may be 50° C. or higher, preferably 70° C. or higher.

[0022] The rubber particles preferably contain one or more groups selected from the group consisting of epoxy groups and / or functional groups capable of reacting with epoxy groups.

[0023] The rubber particles may be commercially available products, for example, one or more selected from the Kane Ace series manufactured by Kaneka Corporation and the Zefiac series manufactured by Aica Kogyo Co., Ltd.

[0024] The rubber particles can be used in the form of a rubber particle-dispersed epoxy resin in which the rubber particles are dispersed in an epoxy resin. The rubber particle-dispersed epoxy resin is an epoxy resin in which the rubber particles are dispersed in a particulate state, preferably in a primary particle state. Because the rubber particles are dispersed in a particulate state, the resulting cured product has superior toughness and impact peel adhesion resistance. Note that "rubber particles dispersed in a particulate state" refers to a state in which the rubber particles are not aggregated with each other in the epoxy resin, are not miscible with each other in the epoxy resin, and are independently dispersed. This dispersion state can be confirmed, for example, by dissolving the rubber particle-dispersed epoxy resin in a solvent and measuring the particle size by laser light scattering, or by observing the rubber particle-dispersed epoxy resin under an electron microscope.

[0025] The epoxy resin constituting the rubber particle-dispersed epoxy resin is not particularly limited as long as it has an epoxy equivalent of, for example, 80 or more, preferably 300 or more, and for example, 10,000 or less, preferably 1,000 or less, more preferably 300 or less. Examples of the epoxy resin include biphenyl-type epoxy resins such as biphenyl-type epoxy resins and tetramethylbiphenyl-type epoxy resins; bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, tetramethylbisphenol F-type epoxy resins, bisphenol E-type epoxy resins, bisphenol S-type epoxy resins, bisphenol AD-type epoxy resins, bisphenol M-type epoxy resins, bisphenol P-type epoxy resins, and bisphenol Z-type epoxy resins, bisphenol-type epoxy resins obtained by hydrogenating these resins, and bisphenol-type epoxy resins obtained by halogenating (brominating, chlorinating) these resins; stilbene-type epoxy resins; phenol novolac-type epoxy resins, brominated phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, and novolac-type epoxy resins having a condensed ring aromatic hydrocarbon structure. resins, novolac type epoxy resins such as phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, biphenyl novolac type epoxy resins, naphthol novolac type epoxy resins, naphthol-phenol co-condensed novolac type epoxy resins, and naphthol-cresol co-condensed novolac type epoxy resins; resol type epoxy resins such as bisphenol A resol type epoxy resins; polyfunctional epoxy resins such as triphenylmethane type epoxy resins, tetraphenylethane type epoxy resins, trihydroxyphenylmethane type epoxy resins, alkyl-modified trihydroxyphenylmethane type epoxy resins, and tetraphenylolethane type epoxy resins; phenol aralkyl type epoxy resins such as phenylene skeleton-containing phenol aralkyl type epoxy resins and biphenylene skeleton-containing phenol aralkyl type epoxy resins;Naphthalene-type epoxy resins such as naphthalene-type epoxy resins, dihydroxynaphthalene-type epoxy resins, naphthalene diol-type epoxy resins, bifunctional to tetrafunctional naphthalene dimer-type epoxy resins obtained by glycidyl etherifying a dimer of hydroxynaphthalene and / or dihydroxynaphthalene, naphthylene ether-type epoxy resins, binaphthyl-type epoxy resins, and naphthol aralkyl-type epoxy resins; anthracene-type epoxy resins; phenoxy-type epoxy resins; bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resins; norbornene-type epoxy resins; adamantane-type epoxy resins; fluorene-type epoxy resins; phosphorus-containing epoxy resins; alicyclic epoxy resins; aliphatic chain epoxy resins Epoxy resins; heterocyclic epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; glycidylamine-type epoxy resins such as N,N,N',N'-tetraglycidyl meta-xylenediamine, N,N,N',N'-tetraglycidyl bisaminomethylcyclohexane and N,N-diglycidylaniline; copolymers of glycidyl (meth)acrylate and a compound having an ethylenically unsaturated double bond; phenol aralkyl-type epoxy resins; naphthol aralkyl-type epoxy resins; salicylaldehyde-type epoxy resins; chelate-modified epoxy resins; and siloxane-modified epoxy resins obtained by modifying these epoxy resins with alkoxysilane, silsesquioxane, or the like; and the like.

[0026] The epoxy resin constituting the rubber particle-dispersed epoxy resin is preferably one or more selected from the group consisting of bisphenol-type epoxy resins, hydrogenated bisphenol-type epoxy resins, novolac-type epoxy resins, brominated epoxy resins, alicyclic epoxy (e.g., cyclohexene oxide group) resins, glycidyl ester resins, glycidyl amine-type epoxy resins, and glycidyl (meth)acrylate (co)polymers. Among these, bisphenol A-type epoxy resins and / or novolac-type epoxy resins are preferred. The weight-average molecular weight of the epoxy resin constituting the rubber particle-dispersed epoxy resin is not particularly limited. For example, it is 5,000 or more, preferably 7,000 or more, and for example, 20,000 or less, preferably 18,000 or less.

[0027] The content of the rubber particles in the rubber particle-dispersed epoxy resin is not particularly limited, and is, relative to the total amount of the rubber particle-dispersed epoxy resin (100 mass%), for example, 1 mass% or more, preferably 5 mass% or more, and more preferably 10 mass% or more, and for example, 60 mass% or less, preferably 50 mass% or less, and more preferably 40 mass% or less.

[0028] The rubber particle-dispersed epoxy resin may be a commercially available product. For example, the Kane Ace series manufactured by Kaneka Corporation is preferred, and in particular, one or more selected from "Kane Ace MX154" containing approximately 40% by mass of core-shell rubber (CSR) particles, which have a polybutadiene core and a vinyl resin shell, and approximately 60% by mass of bisphenol A-type epoxy resin, "Kane Ace MX960" containing approximately 25% by mass of core-shell rubber (CSR) particles and approximately 75% by mass of epoxy resin, and others such as "Kane Ace MX156," "Kane Ace MX153," and "Kane Ace MX120."

[0029] <(b2) Rubber-Modified Epoxy Resin> The rubber-modified epoxy resin is obtained by reacting an epoxy resin with a rubber having a functional group reactive with an epoxy group, and is not particularly limited as long as it has two or more epoxy groups in the molecule and a rubber skeleton. The method for reacting the epoxy resin with the rubber having a functional group reactive with an epoxy group is not particularly limited. For example, there is a method in which a large amount of epoxy resin is mixed with a rubber having a functional group reactive with an epoxy group, and the mixture is reacted in the large amount of epoxy resin.

[0030] The epoxy resin constituting the rubber-modified epoxy resin may be the same as the epoxy resins listed as epoxy resins that can constitute the rubber particle-dispersed epoxy resin in the above section <(b1) Rubber Particles>. The epoxy resin constituting the rubber particle-dispersed epoxy resin and the epoxy resin constituting the rubber-modified epoxy resin may be the same or different.

[0031] The epoxy resin constituting the rubber-modified epoxy resin is preferably one or more selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol B epoxy resins, novolac epoxy resins, brominated epoxy resins, alicyclic epoxy (cyclohexene oxide group, etc.) resins, glycidyl ester resins, glycidyl amine epoxy resins, and glycidyl (meth)acrylate (co)polymers. Among these, bisphenol A epoxy resins and / or novolac epoxy resins are particularly preferred due to their excellent corrosion resistance and adhesion. The weight-average molecular weight of the epoxy resin constituting the rubber-modified epoxy resin is not particularly limited. For example, it is 5,000 or more, preferably 7,000 or more, and for example, 20,000 or less, preferably 18,000 or less.

[0032] Examples of the rubber having a functional group reactive with the epoxy group constituting the rubber-modified epoxy resin include one or more selected from the group consisting of conjugated diene rubber (polybutadiene, isoprene rubber, etc.), conjugated diene-nitrile copolymer rubber (acrylonitrile butadiene rubber (NBR)), urethane rubber, olefin rubber, styrene butadiene rubber (SBR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), butyl rubber (IIR), etc.

[0033] These rubbers preferably have an average of about 1.5 or more, more preferably about 1.8 or more, and about 2.5 or less, and more preferably about 2.2 or less, functional groups reactive with epoxy groups per molecule. Examples of functional groups reactive with epoxy groups include one or more selected from the group consisting of carboxyl groups, amino groups, hydroxyl groups, etc. The functional groups reactive with epoxy groups are preferably located at the terminals of the rubber. The number-average molecular weight of the rubber is not particularly limited. For example, it is 2,000 or more, preferably 3,000 or more, and for example, 10,000 or less, preferably 7,000 or less. The glass transition temperature (Tg) of the rubber is not particularly limited. For example, it is 0°C or less, preferably -25°C or less, more preferably -40°C or less, and for example, -120°C or more, preferably -100°C or more.

[0034] In the present invention, epoxy resins, preferably those obtained from one or more types of bisphenol-type epoxy resins, and one or more types selected from the group consisting of butadiene-acrylonitrile rubber having carboxyl groups at both ends (carboxyl-terminated butadiene-nitrile rubber (CTBN)), butadiene-acrylonitrile rubber having amino groups at both ends (amino-terminated butadiene nitrile rubber (ATBN)), butadiene-acrylonitrile rubber having carboxyl groups and amino groups at both ends (carboxyl-terminated and amino-terminated butadiene-acrylonitrile rubber), and butadiene rubber having carboxyl groups at both ends (carboxyl-terminated polybutadiene rubber (CTB)). In particular, CTBN-modified epoxy resins modified with CTBN are preferred.

[0035] In the rubber-modified epoxy resin, the amount of rubber modification is not particularly limited. With the total amount of the rubber-modified epoxy resin taken as 100% by mass, it is, for example, 1% by mass or more, preferably 2% by mass or more, and for example, 40% by mass or less, preferably 20% by mass or less. The epoxy equivalent of the rubber-modified epoxy resin is also not particularly limited. It is, for example, 100 g / eq or more, preferably 150 g / eq or more, and for example, 1,000 g / eq or less, preferably 500 g / eq or less. Commercially available rubber-modified epoxy resins can be used. For example, one or more selected from the ADEKA Resin EPR series manufactured by ADEKA Corporation and the Hypox series manufactured by Huntsman can be used.

[0036] <(b3) Blocked Urethane Resin> The blocked urethane resin is not particularly limited as long as it contains a urethane group or a urethane group and a urea group, exhibits elastomeric properties, and has all or a portion of its terminal isocyanate groups blocked with a blocking agent. The blocked urethane resin can be obtained, for example, by reacting an excess equivalent of polyisocyanate with a compound having two or more active hydrogen-containing groups to obtain a urethane prepolymer containing a urethane group or a urethane group and a urea group in the main chain and having terminal isocyanate groups, and then reacting all or a portion of the terminal isocyanate groups with a blocking agent having an active hydrogen group to block them. Blocking of the terminal isocyanate groups with a blocking agent can be carried out simultaneously with the production of the urethane prepolymer.

[0037] In the present invention, as the compound having two or more active hydrogen-containing groups constituting the block urethane resin, it is preferable to use a polyol having two or more hydroxyl groups. Examples of polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol. aliphatic polyols such as hexanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-1,8-octanediol, 1-methyl-1,8-octanediol, glycerin, trimethylolpropane, and pentaerythritol; Alicyclic polyols such as Sandiol, 1,4-cyclohexanediol, 1,3,5-cyclohexanetriol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-cyclooctanediol, 1,5-cyclooctanediol, 5-norbornene-2,2-dimethanol, 5-norbornene-2,3-dimethanol, norbornane-2,3-dimethanol, norbornane-2,5-dimethanol, 2,6-decahydronaphthalenedimethanol, 1,3-adamantanediol, 1,4-adamantanediol, 2,4-adamantanediol, tricyclodecane dimethanol, and hydrogenated bisphenol A; polyalkylene glycols such as diethylene glycol, dipropylene glycol, tripropylene glycol, and triethylene glycol;Examples of the polymer polyol include polymer polyols such as polycarbonate polyols, polyether polyols, polyester polyols, polyurethane polyols, polyolefin polyols, and polyconjugated diene polyols, which have a weight average molecular weight of, for example, 300 or more, preferably 500 or more, and for example, 10,000 or less, preferably 5,000 or less;

[0038] The polyol is preferably at least one selected from the group consisting of polymer polyols such as ethylene glycol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, 1,4-cyclohexanediol, 5-norbornene-2,2-dimethanol, 1,4-adamantanediol, tricyclodecane dimethanol, hydrogenated bisphenol A, diethylene glycol, polycarbonate polyol, polyether polyol, polyester polyol, polyurethane polyol, polyolefin polyol, and polyconjugated diene polyol, and having a weight average molecular weight of, for example, 300 or more, preferably 500 or more, and for example, 10,000 or less, preferably 5,000 or less. In the present invention, one or more selected from the group consisting of polymer polyols such as propylene oxide adducts of glycerin, propylene oxide adducts of castor oil, polyether polyols such as polytetramethylene glycol, polycarbonate polyols, polyester polyols, polyurethane polyols, polyolefin polyols, and polyconjugated diene polyols, and the like, having a weight-average molecular weight of, for example, 300 or more, preferably 500 or more, and for example, 10,000 or less, preferably 5,000 or less, are preferred, as they exhibit good properties as an elastomer.

[0039] In the present invention, the polyisocyanate constituting the blocked urethane resin is a compound having two or more isocyanate groups. Examples of the polyisocyanate include 1,6-hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-pentamethylene diisocyanate, 2-methyl-1,5-pentyl diisocyanate, 3-methyl-1,5-pentyl diisocyanate, methylene diisocyanate, 1,2-dimethylene diisocyanate, and 1,3-trimethylhexamethylene diisocyanate. aliphatic polyisocyanate compounds such as diisocyanate, 1,18-octadecylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,10-decamethylene diisocyanate, bis(2-isocyanatoethyl) fumarate, lysine diisocyanate (hexanoic acid-2,6-diisocyanate), 1,6,11-undecane triisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane, and 1,3,6-hexamethylene triisocyanate;2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, 4,4'-diphenyl ether diisocyanate, 2,4'-diphenyl ether diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 2,6-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, dianisidine diisocyanate, o-phenyl diisocyanate, m-phenyl diisocyanate, p-phenyl diisocyanate, halogenated phenyl diisocyanates, cumene-2, Aromatic polyisocyanate compounds such as 4-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-ethoxy-1,3-phenylene diisocyanate, 5,6-dimethyl-1,3-phenylene diisocyanate, benzidine diisocyanate, 1,4-anthracene diisocyanate, 9,10-anthracene diisocyanate, and 4,4'-diisocyanate benzyl; methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, and 1,4-(isocyanate methyl) Alicyclic polyisocyanate compounds such as cyclohexane, 1,3-(isocyanatemethyl)cyclohexane, 1,2-(isocyanatemethyl)cyclohexane, isophorone diisocyanate, dimer acid diisocyanate, bicycloheptane triisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornyl diisocyanate, norbornenemethane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, and hydrogenated products of the above-mentioned diisocyanates having an aromatic ring;The polyisocyanate compound may be one or more selected from the group consisting of biuret, nurate, adduct, allophanate, carbodiimide, and polymeric polyisocyanate derivatives of these polyisocyanate compounds.

[0040] Examples of polyisocyanates that constitute block urethane resins include 1,6-hexamethylene diisocyanate, 1,5-pentamethylene diisocyanate, lysine diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, polymethylene polyphenylene polyisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, p- One or more selected from the group consisting of xylylene diisocyanate, isophorone diisocyanate, bicycloheptane triisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornyl diisocyanate, norbornenemethane diisocyanate, biuret, nurate, adduct, allophanate, carbodiimide and polymeric polyisocyanate derivatives of these polyisocyanate compounds are preferred.

[0041] When a compound (such as a polyol) having two or more active hydrogen-containing groups is reacted with an excess equivalent of a polyisocyanate to obtain a urethane prepolymer containing urethane groups or urethane groups and urea groups in the main chain and having isocyanate groups at the terminals, the reaction ratio of the two is not particularly limited. The isocyanate group of the polyisocyanate is set to be equal to or greater than the active hydrogen equivalent of the compound (such as a polyol) having two or more active hydrogen-containing groups, for example, 1.1 equivalents or more, preferably 2 equivalents or more, and for example, 5 equivalents or less, preferably 3 equivalents or less. The reaction of the polyisocyanate with the compound (such as a polyol) having two or more active hydrogen-containing groups can be carried out, for example, in an inert atmosphere, using a urethane polymerization catalyst as needed, at a temperature of 40°C to 150°C, for example, for a reaction time of 15 minutes to 6 hours. Examples of the urethane polymerization catalyst used as needed include one or more selected from the group consisting of organometallic compounds such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, zinc naphthenate, and zinc octoate, and tertiary amine compounds such as triethylenediamine and triethylamine.

[0042] In the present invention, the blocking agent constituting the blocked urethane resin is not particularly limited as long as it is a compound capable of blocking the isocyanate group of a urethane prepolymer having an isocyanate group at its terminal. Examples of the blocking agent include active methylene compounds such as malonic acid diesters (diethyl malonate, etc.), acetylacetone, and acetoacetic acid esters (ethyl acetoacetate, etc.); oxime compounds such as acetoxime, methyl ethyl ketoxime (MEK oxime), and methyl isobutyl ketoxime (MIBK oxime); monohydric alcohols or isomers thereof such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, heptyl alcohol, hexyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol, and stearyl alcohol; glycol derivatives such as methyl glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol, and butyl diglycol; amine compounds such as dicyclohexylamine; phenol, cresol, 2- , 3- or 4-ethylphenol, 2-, 3- or 4-n-propylphenol, 2-, 3- or 4-isopropylphenol, 2-, 3- or 4-n-butylphenol, 2-, 3- or 4-i-butylphenol, 2-, 3- or 4-t-butylphenol, 4-t-butylphenol, 2-, 3- or 4-n-octylphenol, 2-, 3- or 4-n-nonylphenol, 2-, 3- or 4-n-dodecylphenol, 2-, 3- or 4-cyclohexylphenol, 2-, 3- or 4-chlorophenol, 2-, 3- or 4-bromophenol, resorcinol, catechol, hydroquinone, bisphenol A, bisphenol S, bisphenol F, naphthol and other phenols; ε-caprolactone, ε-caprolactam and other cyclic ester compounds; and the like. Among these blocking agents, it is preferable to use one or more selected from the group consisting of dicyclohexylamine, diphenols, ε-caprolactone and ε-caprolactam from the viewpoint of adhesiveness and the like.

[0043] The reaction molar ratio of the urethane prepolymer having an isocyanate group at its terminal and the blocking agent is not particularly limited. The blocking reaction can be carried out by adding and mixing the blocking agent in an amount that is, for example, 1.0 equivalent or more, preferably 1.5 equivalent or more, and for example, 3.0 equivalents or less, preferably 2.0 equivalents or less, relative to the free isocyanate groups of the urethane prepolymer having an isocyanate group at its terminal. The reaction conditions for the blocking reaction with the blocking agent are not particularly limited. For example, the reaction temperature can be 50°C or more and 150°C or less, and the reaction time can be 15 minutes to 7 hours or less. Furthermore, when reacting the urethane prepolymer having an isocyanate group at its terminal with the blocking agent, the reaction can be accelerated by adding the urethane polymerization catalyst.

[0044] The blocking reaction using a blocking agent can be carried out by adding the blocking agent after obtaining a urethane prepolymer having an isocyanate group at its terminal. Alternatively, the blocking agent can be added at any stage of polymerization of the urethane prepolymer having an isocyanate group at its terminal to carry out the reaction. The blocking agent may be added at the end of polymerization of the urethane prepolymer, at the beginning of polymerization, or in two stages, at the beginning and end of polymerization. For example, during polymerization of the urethane prepolymer, the amount of free isocyanate groups can be confirmed and the blocking agent can be added at any stage.

[0045] The blocked urethane resin (b3) used in the present invention may be a blocked urethane resin obtained by reacting a prepolymer obtained by reacting a compound having two or more active hydrogen-containing groups with a polyisocyanate such that the amount of isocyanate groups is in excess relative to the active hydrogen groups, with a blocking agent having an active hydrogen group. In addition, it is also possible to use a blocked urethane resin obtained by reacting a blocked isocyanate obtained by modifying the polyisocyanate compound (particularly an isocyanuric compound) with the blocking agent with the compound having two or more active hydrogen-containing groups.

[0046] The block urethane resin may be a commercially available product, for example, one or more types selected from the ADEKA RESIN QR series manufactured by ADEKA Corporation.

[0047] <(b4) Urethane-Modified Epoxy Resin> The urethane-modified epoxy resin is not particularly limited as long as it is an epoxy resin having a urethane bond in the molecular chain and an average of 1.1 or more, preferably 2 or more, epoxy groups per molecule.

[0048] The number average molecular weight of the urethane-modified epoxy resin is not particularly limited. As a polystyrene-equivalent molecular weight measured by GPC, it is, for example, 1,500 or more, preferably 3,000 or more, more preferably 4,000 or more, and for example, 40,000 or less, preferably 30,000 or less, more preferably 20,000 or less. The molecular weight distribution (weight average molecular weight / number average molecular weight) is not particularly limited. It is 1 or more, preferably 1.1 or more, more preferably 1.2 or more, and for example, 4 or less, preferably 3 or less, more preferably 2.5 or less.

[0049] The urethane-modified epoxy resin can be obtained, for example, by reacting an epoxy resin containing a group reactive with an isocyanate group with a urethane prepolymer and / or polyisocyanate containing an isocyanate group, and then, if necessary, eliminating excess free isocyanate groups with an alkanol, etc. Examples of the alkanol include one or more selected from the group consisting of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, etc.

[0050] Examples of epoxy resins containing a group reactive with an isocyanate group include epoxy resins having an active hydrogen-containing group such as a hydroxyl group, an amino group, or a carboxyl group, and preferably epoxy resins having a hydroxyl group and an epoxy group.

[0051] The epoxy resin containing a group reactive with an isocyanate group is not particularly limited, as long as it has an epoxy equivalent of 100 or more, preferably 150 or more, and for example, 500 or less, preferably 400 or less, and a hydroxyl value of, for example, 10 or more, preferably 15 or more, and for example, 50 or less, preferably 40 or less. The epoxy resin containing a group reactive with an isocyanate group that constitutes the urethane-modified epoxy resin is the same as the epoxy resins listed as epoxy resins that can constitute the rubber particle-dispersed epoxy resin in the above section <(b1) Rubber Particles>, and includes those that have a group reactive with an isocyanate group. The epoxy resin that constitutes the rubber particle-dispersed epoxy resin and the epoxy resin that constitutes the urethane-modified epoxy resin (b4) may be the same or different.

[0052] The epoxy resin containing a group reactive with an isocyanate group constituting the urethane-modified epoxy resin is, for example, at least one selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol B epoxy resins, novolac epoxy resins, brominated epoxy resins, alicyclic epoxy (e.g., cyclohexene oxide group) resins, glycidyl ester resins, glycidyl amine epoxy resins, and glycidyl (meth)acrylate (co)polymers, preferably containing a hydroxyl group. Among these, bisphenol A epoxy resins and / or novolac epoxy resins containing a hydroxyl group are particularly preferred due to their excellent corrosion resistance and adhesion. The weight-average molecular weight of the epoxy resin containing a group reactive with an isocyanate group constituting the urethane-modified epoxy resin is not particularly limited. It is, for example, 5,000 or more, preferably 7,000 or more, and for example, 20,000 or less, preferably 18,000 or less.

[0053] The urethane prepolymer containing isocyanate groups is obtained by reacting at least a polyol and a polyisocyanate, optionally using a urethane polymerization catalyst, under conditions resulting in a molar excess of isocyanate groups. The reaction ratio of the polyol and polyisocyanate is not particularly limited. The ratio of the isocyanate groups of the polyisocyanate to the hydroxyl groups of the polyol is set to, for example, 1.1 equivalents or more, preferably 1.2 equivalents or more, and for example, 3 equivalents or less, preferably 2.5 equivalents or less. The reaction of the polyol and polyisocyanate can be carried out, for example, in an inert atmosphere, at a temperature of 60°C to 150°C, for example, for a reaction time of 15 minutes to 6 hours. Examples of the urethane polymerization catalyst that may be used as needed include at least one selected from the group consisting of organometallic compounds such as dioctyltin dilaurate, dibutyltin dilaurate, stannous octoate, stannous octoate, zinc naphthenate, and zinc octoate, and tertiary amine compounds such as triethylenediamine and triethylamine.

[0054] The polyol constituting the urethane prepolymer containing an isocyanate group is not particularly limited as long as it is a compound having two or more hydroxyl groups. Examples of such polyols include the same polyols as those listed as polyols that can constitute the block urethane resin in the above section <(b3) Block urethane resin>. The polyol constituting the block urethane resin and the polyol constituting the urethane-modified epoxy resin may be the same or different.

[0055] Examples of polyols constituting the urethane prepolymer containing isocyanate groups include polymer polyols such as ethylene glycol, 1,6-hexanediol, glycerin, trimethylolpropane, pentaerythritol, 1,4-cyclohexanediol, 5-norbornene-2,2-dimethanol, 1,4-adamantanediol, tricyclodecane dimethanol, hydrogenated bisphenol A, diethylene glycol, polycarbonate polyol, polyether polyol, polyester polyol, polyurethane polyol, polyolefin polyol, and polyconjugated diene polyol, and are preferably one or more selected from the group consisting of polymer polyols having a weight average molecular weight of, for example, 300 or more, preferably 500 or more, and for example, 10,000 or less, preferably 5,000 or less.

[0056] The polyisocyanate that constitutes the urethane prepolymer containing an isocyanate group, or the polyisocyanate that is reacted with the epoxy resin containing a group reactive with an isocyanate group, is not particularly limited as long as it is a compound having two or more isocyanate groups. Examples of such polyisocyanates include the same polyisocyanates as those listed as polyisocyanates that can constitute the block urethane resin in the above section <(b3) Block Urethane Resin>. Note that the polyisocyanate that constitutes the block urethane resin and the polyisocyanate that constitutes the urethane prepolymer containing an isocyanate group or the polyisocyanate that constitutes the urethane-modified epoxy resin may be the same or different.

[0057] Examples of polyisocyanates that constitute urethane prepolymers containing isocyanate groups, or polyisocyanates that are reacted with epoxy resins containing groups reactive with isocyanate groups, include 1,6-hexamethylene diisocyanate, 1,5-pentamethylene diisocyanate, lysine diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, polymethylene polyphenylene polyisocyanate, o-oxy Preferred is one or more selected from the group consisting of rylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, isophorone diisocyanate, bicycloheptane triisocyanate, 4,4'-dicyclohexylmethane diisocyanate, norbornyl diisocyanate, norbornenemethane diisocyanate, and polyisocyanate derivatives which are biuret, nurate, adduct, allophanate, carbodiimide, or polymer of these polyisocyanate compounds.

[0058] When reacting an isocyanate group-containing urethane prepolymer and / or polyisocyanate with an epoxy resin containing a group reactive with an isocyanate group, the reaction ratio of the two is not particularly limited. The ratio of the isocyanate group-reactive groups of the epoxy resin containing a group reactive with an isocyanate group to the isocyanate groups of the isocyanate group-containing urethane prepolymer and / or polyisocyanate is set to be at least equivalent, for example, 1.1 equivalents or more, preferably 2 equivalents or more, and for example, 5 equivalents or less, preferably 3 equivalents or less. Here, the group reactive with an isocyanate group is preferably a hydroxyl group. The reaction of an isocyanate group-containing urethane prepolymer and / or polyisocyanate with an epoxy resin containing a group reactive with an isocyanate group can be carried out, for example, in an inert atmosphere, at a temperature of 60°C to 150°C, for example, for a reaction time of 15 minutes to 6 hours.

[0059] In the present invention, the urethane-modified epoxy resin is preferably one obtained by thermally reacting a urethane prepolymer obtained by reacting a polyether polyol or a polyester polyol with a polyisocyanate with an epoxy resin having a hydroxyl group in the molecule in the presence of a urethane-forming catalyst. Commercially available urethane-modified epoxy resins can be used. For example, one or more types selected from the ADEKA Resin EPU series manufactured by ADEKA Corporation can be used.

[0060] <Toughness-imparting agent content> In the adhesive composition of the present invention, the content of the toughness-imparting agent is not particularly limited. The content of the toughness-imparting agent, relative to 100 mass% of the total amount of the adhesive composition, is, for example, 5.5 mass% or more, preferably 10.0 mass% or more, more preferably 15.0 mass% or more, and even more preferably 20.0 mass% or more, and can be, for example, 75.0 mass% or less, preferably 70.0 mass% or less, and more preferably 65.0 mass% or less. If the content of the toughness-imparting agent, relative to 100 mass% of the total amount of the adhesive composition, is less than 5.5 mass%, problems with adhesion may occur, and the cured product may become brittle, resulting in problems with impact resistance. If the content exceeds 75.0 mass%, the amount of toughness-imparting agent may be excessive, resulting in problems with adhesion and costs.

[0061] In the adhesive composition of the present invention, when the rubber particles (b1) serving as a toughening agent are a rubber particle-dispersed epoxy resin, the content of the rubber particle-dispersed epoxy resin can be, for example, 0% by mass or more, preferably 15.0% by mass or more, and for example, 60.0% by mass or less, preferably 50.0% by mass or less, based on 100% by mass of the total adhesive composition. In the adhesive composition of the present invention, the content of the rubber-modified epoxy resin (b2) serving as a toughening agent can be, for example, 0% by mass or more, and for example, 20.0% by mass or less, preferably 15.0% by mass or less, based on 100% by mass of the total adhesive composition. In the adhesive composition of the present invention, the content of the block urethane resin (b3) serving as a toughening agent can be, for example, 0% by mass or more, preferably 15.0% by mass or more, and for example, 60.0% by mass or less, preferably 50.0% by mass or less, based on 100% by mass of the total adhesive composition. In the adhesive composition of the present invention, the content of the urethane-modified epoxy resin (b4) as a toughness imparting agent can be, for example, 0% by mass or more and, for example, 15.0% by mass or less, preferably 10.0% by mass or less, where the total amount of the adhesive composition is 100% by mass.

[0062] In the present invention, when a rubber-based toughening agent containing (i) (b1) a rubber particle-dispersed epoxy resin as rubber particles and / or (b2) a rubber-modified epoxy resin is used as the toughening agent, the content of the rubber-based toughening agent can be, for example, 0% by mass or more, preferably 15.0% by mass or more, more preferably 20.0% by mass or more, and for example, 75.0% by mass or less, preferably 60.0% by mass or less, more preferably 55.0% by mass or less, and even more preferably 50.0% by mass or less, based on 100% by mass of the total adhesive composition. In the present invention, when a urethane-based toughening agent containing (ii) (b3) a block urethane-based resin and / or (b4) a urethane-modified epoxy resin is used as the toughening agent, the content of the urethane-based toughening agent can be, for example, 0% by mass or more, preferably 5.0% by mass or more, and for example, 75.0% by mass or less, preferably 30.0% by mass or less, and more preferably 20.0% by mass or less, based on 100% by mass of the total adhesive composition. In the present invention, when both (i) and (ii) of (b1) rubber particle-dispersed epoxy resin and / or (b2) rubber-modified epoxy resin as rubber particles and (ii) (b3) block urethane resin and / or (b4) urethane-modified epoxy resin are used as toughening agents, the content ratio (mass ratio) of (i) to (ii) is not particularly limited. The content of (i) is, for example, 0% by mass or more, or 50% by mass or more, and for example, 100% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, where the total amount of (i) and (ii) is 100% by mass. If the content ratio (mass ratio) of (i) is less than 50% by mass, problems with adhesion may occur.

[0063] [(C) Epoxy Resin] The (C) epoxy resin may be the same as the epoxy resins listed as epoxy resins that can constitute the rubber particle-dispersed epoxy resin in the above <(b1) Rubber Particles>. When a rubber particle-dispersed epoxy resin is used as the (b1) rubber particles, the epoxy resin constituting the rubber particle-dispersed epoxy resin and the (C) epoxy resin may be the same or different. The (C) epoxy resin is different from the (B) toughness imparting agent.

[0064] As the epoxy resin (C), from the viewpoints of curability, adhesiveness, water resistance, durability, workability, availability, versatility, etc., it is preferable to use one or more types selected from the group consisting of biphenyl-type epoxy resins, bisphenol-type epoxy resins, novolac-type epoxy resins, resol-type epoxy resins, epoxy resins having a naphthalene skeleton, etc. In the present invention, it is more preferable to use a bisphenol-type epoxy resin.

[0065] The content of the (C) epoxy resin is not particularly limited and can be, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the total amount of the adhesive composition.

[0066] [(D) Epoxy Resin Curing Agent] The epoxy resin curing agent is not particularly limited as long as it can cure the epoxy resin and adhesive composition. Curing agents that can cure the rubber particle-dispersed epoxy resin (b1) as the rubber particles in the (B) toughness imparting agent, the (b2) rubber-modified epoxy resin, and the (b4) urethane-modified epoxy resin, and curing agents that can cure the (C) epoxy resin are used.

[0067] As the epoxy resin curing agent, conventionally known components can be appropriately selected and used depending on the type of adhesive composition (one-component type, two-component type, heat-curing type, photo-curing type, etc.) and the intended use. For example, as an epoxy resin curing agent used in a one-component adhesive composition, an epoxy resin curing agent is selected that can rapidly cure the adhesive composition when the adhesive composition is heated to a temperature of 60°C or higher, preferably 100°C or higher, or when irradiated with light, and that cannot cure the adhesive composition or cures it very slowly at temperatures of 50°C or lower. For example, as an epoxy resin curing agent used in a two-component adhesive composition, an epoxy resin curing agent is selected that can rapidly cure the adhesive composition when the two components are mixed.

[0068] The epoxy resin curing agent used in the one-component adhesive composition may be, for example, a latent epoxy resin curing agent, such as at least one selected from the group consisting of dicyandiamide-based curing agents, imidazole-based curing agents, amine-based curing agents, hydrazide-based curing agents, urea-based curing agents, guanamine-based curing agents, amine complex salt-based curing agents, organometallic complex-based curing agents, and microcapsule-based curing agents.

[0069] An example of the dicyandiamide-based curing agent is dicyandiamide.

[0070] Examples of imidazole-based curing agents include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-ethyl-4-methylimidazole, 2-dodecylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 4-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2-methylimidazolium isocyanurate, 2-phenylimidazolium isocyanurate, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole Dimethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 1-cyanoethyl-2-phenyl-4,5-di(cyanoethoxymethyl)imidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1,3-dibenzyl-2-methylimidazolium chloride, 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-S-triazine, 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-S-triazine

[0039] 2,4-diamino-6-[2-ethyl-4-methylimidazolyl-(1)]-ethyl-S-triazine isocyanurate, 2,4-diamino-6-[2-ethyl-4-methylimidazolyl-(1)]-ethyl-S-triazine, 2,4-diamino-6-[2-undecylimidazolyl-(1)]-ethyl-S-triazine, N,N'-[2-methylimidazolyl-(1)-ethyl]-aziboyldiamide, and an adduct obtained by reacting an imidazole compound with an epoxy resin.

[0071] Examples of amine-based curing agents that can be used as the latent curing agent include one or more tertiary amine compounds selected from the group consisting of benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 2-(dimethylaminomethyl)phenol, dimethylcyclohexylamine, dimethylbenzylamine, dimethylhexylamine, dimethylaminomethylphenol, dimethylamino-p-cresol, pyridine, piperidine, triethylenediamine, and N,N-dimethylpiperidine; and modified polyamines selected from the group consisting of reaction products of polyamine compounds and epoxy compounds (amine-epoxy adducts), amidation reaction products of polyamine compounds, and Mannich-modified products of polyamine compounds.

[0072] Examples of polyamine compounds constituting the modified polyamine include those having, in the molecule, one or more active hydrogen atoms capable of addition reacting with an epoxy group and at least one or more functional groups selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group. For example, aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,2-diaminopropane, n-propylamine, 2-hydroxyethylaminopropylamine, polyoxypropylenediamine, polyoxypropylenetriamine, dimethylaminopropylamine, diethylaminopropylamine, di-n-propylaminopropylamine, dibutylaminopropylamine, dimethylaminoethylamine, and diethylaminoethylamine; isophoronediamine, menthenediamine, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5 alicyclic polyamines such as 4,4'-diamino-dicyclohexylmethane, m-phenylenediamine, p-phenylenediamine, 2-methylaniline, tolylene-2,4-diamine, tolylene-2,6-diamine, mesitylene-2,4-diamine, mesitylene-2,6-diamine, 3,5-diethyltolylene-2,4-diamine, 3,5-diethyltolylene-2,6-diamine, biphenylenediamine, 4,4'-diaminodiphenylmethane, 2,5-naphthylenediamine, 2,6-naphthylenediamine; nitrogen-containing heterocyclic compounds such as 2-ethyl-4-methylimidazole, 2-ethyl-4-methylimidazoline, 2,4-dimethylimidazoline, piperidine, piperazine, and N-methylpiperazine.

[0073] Among the modified polyamines, examples of the reaction product (amine-epoxy adduct) of a polyamine compound and an epoxy compound include those obtained by reacting one or more of the above-mentioned polyamine compounds with one or more of the epoxy compounds selected from the group consisting of the same epoxy resins as those exemplified as the epoxy resins that can constitute the (b1) rubber particle-dispersed epoxy resin in the above <(b1) rubber particle-dispersed epoxy resin>>.

[0074] Among modified polyamines, the epoxy compound constituting the reaction product (amine-epoxy adduct) of a polyamine compound and an epoxy compound is preferably, for example, one or more selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol B epoxy resins, novolac epoxy resins, brominated epoxy resins, alicyclic epoxy (cyclohexene oxide group, etc.) resins, glycidyl ester resins, glycidyl amine epoxy resins, glycidyl (meth)acrylate (co)polymers, etc. Among these, bisphenol A epoxy resins and / or novolac epoxy resins are particularly preferred due to their excellent corrosion resistance and adhesion. The weight-average molecular weight of the epoxy compound is not particularly limited. For example, it is 5,000 or more, preferably 7,000 or more, and for example, 20,000 or less, preferably 18,000 or less.

[0075] Among the modified polyamines, examples of the amidation reaction products of polyamine compounds include one or more amidation reaction products obtained by reacting one or more of the above-mentioned polyamine compounds with one or more carboxylic acid compounds such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, and dimer acid.

[0076] Among the modified polyamines, examples of the Mannich-modified polyamine compounds include one or more Mannich-modified products obtained by reacting one or more of the above-mentioned polyamine compounds with an aldehyde compound such as formaldehyde, or a phenol compound having one or more aldehyde-reactive sites such as phenol, cresol, xylenol, tertiary butylphenol, or resorcinol.

[0077] As the amine-based curing agent, for example, one or more commercially available products such as the Amicure series (manufactured by Ajinomoto Fine-Techno Co., Ltd.) and the Novacure series (manufactured by Asahi Kasei Corporation) can be used.

[0078] Examples of hydrazide curing agents include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, phthalic acid dihydrazide, stearic acid dihydrazide, isophthalic acid dihydrazide, semicarbazide, carbohydrazide, iminodiacetic acid dihydrazide, pimelic acid dihydrazide, dodecane dihydrazide, hexafluorooctyl ether ... Examples thereof include one or more selected from the group consisting of sadecane dihydrazide, maleic dihydrazide, fumaric dihydrazide, diglycolic dihydrazide, tartaric dihydrazide, malic dihydrazide, terephthalic dihydrazide, 2,6-naphthoic dihydrazide, 4,4'-bisbenzenedihydrazide, 1,4-naphthoic dihydrazide, Amicure VDH (trade name of Ajinomoto Co., Inc.), Amicure UDH (trade name of Ajinomoto Co., Inc.), citric trihydrazide, and the like.

[0079] Examples of the urea-based curing agent include 3-(3,4-dichlorophenyl)-1,1-dimethylurea, isophorone diisocyanate-dimethylurea, tolylene diisocyanate-dimethylurea, N-(2-methylimidazolyl-1-ethyl)-urea, p-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea, 3,4-dichlorophenyl-N,N-dimethylurea, N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea, 1,1-dimethylphenylurea, and adducts obtained by reacting an amine compound with an isocyanate compound or a urea compound, and the like.

[0080] The guanamine-based curing agent may be, for example, one or more selected from the group consisting of acetoguanamine, benzoguanamine, and the like.

[0081] The amine complex salt curing agent may be, for example, one or more selected from the group consisting of boron trichloride-amine complex, boron trifluoride-amine complex, and the like.

[0082] Examples of the organometallic complex curing agent include one or more selected from the group consisting of acetylacetonatoaluminum salt, acetylacetonatocobalt salt, acetylacetonatochromium salt, acetylacetonatomanganese salt, zinc octoate, tin octoate, zinc naphthenate, and the like.

[0083] Examples of microcapsule-based curing agents include those obtained by microencapsulating one or more latent epoxy resin curing agents with one or more selected from the group consisting of resins such as polyurethane resins, acrylic resins, polyester resins, epoxy resins, polyolefin resins, polyamide resins, polystyrene resins, and phenolic resins, thin metal films such as nickel and copper, and inorganic substances such as boron oxide, boric acid esters, silica, calcium oxide, and calcium silicate. As the latent epoxy resin curing agent constituting the microcapsule-based curing agent, it is preferable to use one or more amine-based curing agents.

[0084] The epoxy resin curing agent used in the two-component adhesive composition may be, for example, a room-temperature-curing epoxy resin curing agent that is active even at relatively low temperatures around room temperature (20° C.±15° C.). Examples of the room-temperature-curing epoxy resin curing agent include one or more selected from the group consisting of acid anhydride-based curing agents, room-temperature-curing amine-based curing agents, phenolic resin-based curing agents, and mercaptan-based curing agents.

[0085] Examples of acid anhydride curing agents include one or more selected from the group consisting of phthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, methylhimic anhydride, methylcyclohexene dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bistrimellitate, glycerol tristrimellitate, dodecenyl succinic anhydride, polyazelaic anhydride, and poly(ethyloctadecanedioic) anhydride.

[0086] Examples of amine-based curing agents include 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane, isophoronediamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, diethylaminopropylamine, bis(4-amino-3-methyldicyclohexyl)methane, 4,4'-diaminodicyclohexylmethane, and 1,1-bis(4-aminophenyl) Cyclohexane, bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane, bis(4-aminocyclohexyl)methane, 4,4'-diaminodiethyldiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, diethyltoluenediamine, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenyl ether, bis(4-aminophenyl)phenylmethane, bisaniline, dimethylaniline, triethylenediamine amine, dimethylbenzylamine, 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylaniline, 3,3'-dichloro-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,4-diaminophenol, 2,5-diaminophenol, o-phenylenediamine, m-phenylenediamine Amines, p-phenylenediamine, m-xylylenediamine, 2,3-tolylenediamine, 2,4-tolylenediamine, 2,5-tolylenediamine, 2,6-tolylenediamine, 3,4-tolylenediamine, methylthiotoluenediamine, diethyltoluenediamine, 1,5-diaminonaphthalene, norbornanediamine, bis(4-amino-3-methylcyclohexyl)methane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, tricyclodecanediamine, 1,Examples of the compound include one or more selected from the group consisting of 3-bisaminomethylcyclohexane, polyamine epoxy resin adducts which are reaction products of epoxy resins and excess polyamines, ketimines which are dehydration reaction products of polyamines and ketones such as methyl ethyl ketone and isobutyl methyl ketone, polyamidoamines produced by condensation of dimers (dimer acids) of tall oil fatty acids with polyamines, and amidoamines produced by condensation of tall oil fatty acids with polyamines.

[0087] Examples of the phenol resin-based curing agent include one or more selected from the group consisting of phenol novolac resin, cresol novolac resin, aniline-modified resole resin, dimethyl ether resole resin, tert-butylphenol novolac resin, nonylphenol novolac resin, and phenol aralkyl resin.

[0088] Examples of the mercaptan curing agent include one or more selected from the group consisting of esters of trimethylolpropane and mercapto fatty acids, esters of pentaerythritol and mercapto fatty acids, aromatic ring-containing ether-type mercapto ether compounds, mercapto ether compounds of trimethylolpropane, mercapto ether compounds of glycerin, and derivatives thereof.

[0089] In the adhesive composition of the present invention, it is preferable to use a latent epoxy resin curing agent capable of forming a one-component heat-curable adhesive as the epoxy resin curing agent. Among these, it is preferable to use a latent epoxy resin curing agent containing dicyandiamide and a urea-based curing agent.

[0090] In the adhesive composition of the present invention, the content of the epoxy resin curing agent is not particularly limited. It is appropriately set depending on the content of the epoxy resin curing component in the adhesive composition. The content of the epoxy resin curing agent, based on 100% by mass of the total amount of the adhesive composition, is, for example, 1.0% by mass or more, preferably 3.0% by mass or more, and more preferably 5.0% by mass or more, and can be, for example, 25.0% by mass or less, preferably 20.0% by mass or less, and more preferably 17.0% by mass or less. If the content of the epoxy resin curing agent, based on 100% by mass of the total amount of the adhesive composition, is less than 1.0% by mass, problems may arise in curability and adhesion. If it exceeds 25.0% by mass, the curing agent may be excessive, causing problems in terms of adhesion and cost.

[0091] [(E) Other Components] The adhesive composition of the present invention may contain "(E) other components" other than the above (A) to (D), to the extent that the properties, etc. of the adhesive composition are not impaired. Examples of other components include one or more selected from the group consisting of resins, curing agents, fillers, curing accelerators, viscosity modifiers, moisture absorbers, silane coupling agents, tackifiers, plasticizers, anti-sagging agents, antioxidants, colorants, diluents, antioxidants, UV absorbers, stabilizers, fragrances, polymerization initiators, antistatic agents, reinforcing agents, flame retardants, lubricants, etc.

[0092] (Resin) Among the other components, the resin is a resin other than (B) the toughening agent and (C) the epoxy resin. For example, it may be one or more resins selected from the group consisting of thermoplastic resins, thermosetting resins, photocurable resins, etc. In the present invention, it is preferably one or more resins selected from the group consisting of thermosetting resins and / or photocurable resins, and more preferably one or more thermosetting resin compositions.

[0093] (Curing Agent) Among the other components, the curing agent is a curing agent other than the (D) epoxy resin curing agent. Examples thereof include a curing agent for the block urethane resin in the (B) toughness imparting agent, and a curing agent for the thermosetting resin and / or photocurable resin as the resin among the other components.

[0094] (Filler) Among other components, the filler may be selected from the group consisting of inorganic fillers such as calcium carbonate, calcium oxide, magnesium carbonate, titanium oxide, fused silica, precipitated silica, fumed silica, alumina, zinc oxide, diatomaceous earth, white clay, kaolin, clay, bentonite, dolomite, talc, wood flour, walnut shell powder, rice husk powder, silicic anhydride, aluminum silicate, magnesium silicate, calcium silicate, wollastonite, quartz powder, aluminum powder, zinc powder, iron powder, glass fiber, carbon fiber, glass beads, aluminum hydroxide, glass balloons, shirasu balloons, silica balloons, magnesium oxide, and carbon black; wood fillers such as pulp and cotton chips; and organic fillers such as powdered rubber, recycled rubber, thermoplastic resin particles, thermosetting resin powder, and hollow resin particles. The filler may be surface-treated with resin, silane coupling agent, titanium chelating agent, aluminum coupling agent, fatty acid, fatty acid ester, rosin, etc.

[0095] The content of the filler is not particularly limited. It can be, for example, 80% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 35% by mass or less, based on 100% by mass of the total solid content of the adhesive composition. The adhesive composition of the present invention may not contain a filler. When the content of the filler is 80% by mass or less, an increase in the viscosity of the adhesive composition can be suppressed, and the coatability and workability can be improved.

[0096] [Form of Adhesive Composition] The form of the adhesive composition of the present invention is not particularly limited. For example, it can be a one-component adhesive composition in which all of the constituent components are mixed in advance, sealed, stored, applied to an adherend, and cured by heating or light irradiation as necessary. Alternatively, for example, it can be a two-component / multi-component adhesive composition in which a liquid A containing a curable component and a liquid B containing a curing agent component are prepared, and the liquids A and B are mixed before use. From the viewpoint of handleability, etc., the adhesive composition of the present invention is preferably a one-component adhesive composition.

[0097] [Method for Producing Adhesive Composition] The method for producing the adhesive composition of the present invention is not particularly limited, and examples thereof include a method in which adhesive constituent components including (A) lignin sulfonate, (B) toughness imparting agent, (C) epoxy resin, and (D) epoxy resin curing agent are mixed by a conventionally known method using a mixer, stirrer, or the like.

[0098] [Bonding Method] The bonding method using the adhesive composition is not particularly limited. In the case of a one-component adhesive composition, for example, an adhesive method can be used in which the adhesive composition is applied to one or both of the adherends, the adherends are brought into contact with each other so that the adhesive composition is disposed between the adherends to be joined, and heated or the like as necessary to cure. In the case of a two-component adhesive composition, for example, an adhesive method can be used in which (i) liquid A and liquid B are mixed immediately before use, the mixture is applied to one or both of the adherends, the adherends are brought into contact with each other so that the adhesive composition is disposed between the adherends to be joined, and heated or the like as necessary to cure; or (ii) liquid A is applied to one adherend, and liquid B is applied to the other adherend, the coated surfaces of liquid A and liquid B are brought into contact with each other, and heated or the like as necessary to cure.

[0099] The method for applying (spraying) the adhesive composition to the adherend is not particularly limited. For example, the adhesive composition can be applied by extruding it onto the adherend in the form of a bead, monofilament, or swirl using a coating robot, or it can be applied using a coating device such as a caulking gun or spray gun, or it can be applied by dipping, brushing, roller, or other means.

[0100] The curing temperature of the adhesive composition is not particularly limited. In the case of a one-component adhesive composition, the curing temperature is, for example, 50°C or higher, preferably 80°C or higher, more preferably 100°C or higher, and for example, 250°C or lower, preferably 200°C or lower, more preferably 180°C or lower. In the case of a two-component adhesive composition, the curing temperature is, for example, 0°C or higher, preferably 10°C or higher, more preferably 15°C or higher, and for example, 200°C or lower, preferably 180°C or lower, more preferably 150°C or lower.

[0101] [Uses of Adhesive Composition] The adhesive composition of the present invention can be cured at low temperatures below 160°C, for example, 150°C or lower, and in some cases 130°C or lower, and further has excellent adhesion not only to non-oily surfaces but also to various oily surfaces. Therefore, it can be suitably used as a structural adhesive used to bond metal members and the like in a wide range of fields, including automobiles, ships, railway vehicles, aircraft, the aerospace industry, civil engineering, architecture, and electronics. The structural adhesive exhibits little deterioration in adhesion even under heavy loads for long periods of time, making it a highly reliable adhesive (JIS K 6800). The adhesive composition of the present invention can be suitably used as an automotive structural adhesive used to structurally bond various members and parts during automobile manufacturing.

[0102] The adhesive composition of the present invention can also be used as an adhesive for electronic materials, such as an interlayer adhesive for multilayer substrates such as build-up substrates, an adhesive for bonding optical components, an adhesive for laminating optical disks, an adhesive for mounting printed wiring boards, a die bonding adhesive, an adhesive for semiconductors such as underfills, an underfill for reinforcing BGAs, and a mounting adhesive for anisotropic conductive films (ACFs), anisotropic conductive pastes (ACPs), etc. Furthermore, the adhesive composition of the present invention can also be used for office use, medical use, textile use, etc.

[0103] The following examples are provided for more detailed explanation. It should be noted that these examples are merely illustrative and should not be construed as limiting. Unless otherwise specified, "parts" in each example refer to parts by mass, and "%" refers to % by mass.

[0104] [Components] The components used in Examples 1 to 27 and / or Comparative Examples 1 to 5 are as follows. <(A) Ligninsulfonates> Ligninsulfonate 1: High-purity, high-molecular-weight sodium ligninsulfonate ("Pearlex NP" manufactured by Nippon Paper Industries Co., Ltd.) Ligninsulfonate 2: High-purity, partially desulfonated sodium ligninsulfonate ("Vanilex N" manufactured by Nippon Paper Industries Co., Ltd.) Ligninsulfonate 3: Sodium ligninsulfonate ("Sunex P252" manufactured by Nippon Paper Industries Co., Ltd.) Ligninsulfonate 4: Magnesium ligninsulfonate ("Sunex P321" manufactured by Nippon Paper Industries Co., Ltd.) Ligninsulfonate 5: Ammonium ligninsulfonate ("V-tec 30" manufactured by Boreegaard) Ligninsulfonate 6: Modified sodium ligninsulfonate ("Lignin (dealkalized) [L0045]" manufactured by Tokyo Chemical Industry Co., Ltd.) Ligninsulfonate 7: Modified sodium ligninsulfonate ("Reagent" manufactured by Tokyo Chemical Industry Co., Ltd.) Lignin (alkali) [L0082]) Lignin sulfonate 8: Sodium lignin sulfonate (manufactured by Tokyo Chemical Industry Co., Ltd., "Reagent Sodium lignin sulfonate [L0098]")

[0105] <(B) Toughening Agents> Toughening agent 1 (rubber-based toughening agent): CSR-dispersed epoxy resin composition ("Kane Ace MX154" manufactured by Kaneka Corporation) Toughening agent 2 (rubber-based toughening agent): CTBN-modified epoxy resin ("Hypox RA840" manufactured by Huntsman) Toughening agent 3 (urethane-based toughening agent): block urethane-based resin ("ADEKA Resin QR9466" manufactured by ADEKA Corporation) Toughening agent 4 (urethane-based toughening agent): urethane-modified epoxy resin ("ADEKA Resin EPU-73B" manufactured by ADEKA Corporation)

[0106] <(C) Epoxy Resin> Epoxy resin 1: bisphenol A type epoxy resin having an epoxy equivalent of 190±10 (g / eq)

[0107] <(D) Epoxy Resin Curing Agents> Epoxy resin curing agent 1: dicyandiamide Epoxy resin curing agent 2: 3-(3,4-dichlorophenyl)-1,1-dimethylurea Epoxy resin curing agent 3: microencapsulated amine-based curing agent (Asahi Kasei Corporation, "AER Hardener D1301") Epoxy resin curing agent 4: 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-s-triazine Epoxy resin curing agent 5: urea adduct-based curing agent (T&K Toka Corporation, "Fujicure FXR-1030")

[0108] <(E) Other Components> Filler 1: Polydimethylsiloxane surface-treated fumed silica Filler 2: Calcium carbonate ("Whiten SB" manufactured by Shiraishi Calcium Co., Ltd.)

[0109] [Evaluation] The adhesive compositions obtained in Examples 1 to 27 and Comparative Examples 1 to 5 were evaluated as follows.

[0110] <Adhesion to Oil-Free Surfaces> Adhesion to oil-free surfaces was evaluated by the shear bond strength test and observation of the state of failure shown below.

[0111] (Shear Bond Strength Test) Two cold-rolled steel plates measuring 100 mm long x 25 mm wide x 2.0 mm thick were prepared and their surfaces were degreased. Each adhesive composition was applied to the degreased surface of the cold-rolled steel plate. The degreased surfaces of the two cold-rolled steel plates were then overlapped so that the overlap was 12.5 mm. Any excess adhesive composition was removed to prepare a shear bond strength test piece. The shear bond strength test piece was placed in a 120°C dryer and heated so that the adhesive composition-coated area was maintained at 120°C for 20 minutes. After heating, the shear bond strength test piece was allowed to cool for 24 hours. The shear bond strength test piece after cooling was then tested using a universal tensile tester at a tensile speed of 50 mm / min to measure the shear bond strength (tensile shear bond strength). The results are shown in Tables 1 to 4.

[0112] (Failure state) The failure state at the time of failure during the shear adhesive strength test was visually observed. The results are shown in Tables 1 to 4. The symbols have the following meanings: CF: cohesive failure CF-TCF: cohesive failure (partial thin layer cohesive failure) TCF: thin layer cohesive failure AF-TCF: interfacial failure (partial thin layer cohesive failure) AF: interfacial failure

[0113] Based on the obtained shear bond strength, the adhesiveness was evaluated according to the following criteria. In the present invention, C is a failure. The results are shown in Tables 1 to 4. A: The shear bond strength was 20 MPa or more, and the failure state was CF or CF-TCF. B: The shear bond strength was 10 MPa or more and less than 20 MPa, and the failure state was CF, CF-TCF, or TCF. C: The shear bond strength was less than 10 MPa, or the failure state was AF or AF-TCF.

[0114] <Adhesion to Oily Surface> Adhesion to oily surfaces was evaluated by the peel adhesion strength test and observation of the state of fracture shown below.

[0115] (Peel Adhesion Strength Test) Two cold-rolled steel plates measuring 200 mm long x 25 mm wide x 0.6 mm thick were prepared and bent 90° at a point 50 mm from each end. The cold-rolled steel plates were oiled with anti-rust oil ("Noxrust 550" manufactured by Nippon Parkerizing Co., Ltd.), and then placed upright and left at room temperature (25°C ± 15°C) for 24 hours. Each adhesive composition was applied to the oiled surface of the cold-rolled steel plate, and the oiled surfaces of the two cold-rolled steel plates were overlapped so that the overlapping area was 150 mm. Any excess adhesive composition was removed to prepare peel adhesion strength test specimens. The peel adhesive strength test piece was placed in a dryer at 120°C and heated so that the adhesive composition-coated area was maintained at 120°C for 20 minutes, and then allowed to cool for 24 hours. The peel adhesive strength test piece after cooling was then tested using a universal tensile tester at a tensile speed of 200 mm / min to measure the peel adhesive strength. The results are shown in Tables 1 to 4.

[0116] (Failure state) The failure state at the time of failure during the peel adhesive strength test was visually observed. The results are shown in Tables 1 to 4. The symbols have the following meanings: CF: cohesive failure CF-TCF: cohesive failure (partial thin layer cohesive failure) TCF: thin layer cohesive failure AF-TCF: interfacial failure (partial thin layer cohesive failure) AF: interfacial failure

[0117] Based on the obtained peel bond strength and state of failure, the adhesion was evaluated according to the following criteria. In the present invention, C is a failure. The results are shown in Tables 1 to 4. A: Peel bond strength is 100 N / 25 mm or more, and the state of failure is CF or CF-TCF. B: Peel bond strength is 60 N / 25 mm or more, and the state of failure is CF, CF-TCF, or TCF. C: Peel bond strength is less than 60 N / 25 mm, or the state of failure is AF or AF-TCF.

[0118] [Examples 1 to 27, Comparative Examples 1 to 5] Each adhesive composition was prepared by mixing the components shown in Tables 1 to 4 in the amounts (parts by mass) shown in Tables 1 to 4 into a 5L universal mixer (manufactured by Dalton), stirring for 30 minutes, and then degassing under reduced pressure for 10 minutes. Each of the resulting adhesive compositions was evaluated for adhesion to non-oily surfaces and adhesion to oily surfaces. The results are also shown in Tables 1 to 4.

[0119]

[0120]

[0121]

[0122]

[0123] Tables 1 to 4 show that the adhesive compositions of the present invention have excellent adhesion to non-oily surfaces and oily surfaces. Tables 1 to 4 show that the adhesive compositions of the present invention ensure curing properties at low temperatures below 160°C, for example at low temperatures of 120°C, and also have excellent adhesion to oily surfaces. Furthermore, the adhesive compositions of Examples 1 to 27 according to the adhesive composition of the present invention are all one-component adhesive compositions, and are therefore excellent in workability and handling.

Claims

1. An adhesive composition comprising: (A) a lignin sulfonate; (B) a toughening agent; (C) an epoxy resin; and (D) an epoxy resin curing agent.

2. The adhesive composition according to claim 1, wherein the content of the lignin sulfonate (A) is from 0.1% by mass to 25.0% by mass, with the total amount of the adhesive composition being 100% by mass.

3. The adhesive composition according to claim 1 or 2, wherein the content of the lignin sulfonate (A) is from 0.1% by mass to 15.0% by mass, with the total amount of the adhesive composition being 100% by mass.

4. The adhesive composition according to claim 1 or 2, wherein the (B) toughness imparting agent comprises at least one member selected from the group consisting of (b1) rubber particles, (b2) rubber-modified epoxy resin, (b3) block urethane resin, and (b4) urethane-modified epoxy resin.

5. The adhesive composition according to claim 4, wherein the (B) toughness imparting agent is a urethane-based toughness imparting agent containing (b3) a block urethane-based resin and / or (b4) a urethane-modified epoxy resin.

6. The adhesive composition according to claim 1, wherein the (B) toughness imparting agent comprises: (i) (b1) a rubber-based toughness imparting agent comprising rubber particles and / or (b2) a rubber-modified epoxy resin; and (ii) (b3) a urethane-based toughness imparting agent comprising a block urethane-based resin and / or (b4) a urethane-modified epoxy resin.

7. The adhesive composition according to claim 6, wherein the content of the rubber-based toughness imparting agent is from 20.0% by mass to 50.0% by mass, and the content of the urethane-based toughness imparting agent is from 5.0% by mass to 20.0% by mass, with the total amount of the adhesive composition being 100% by mass.

8. The adhesive composition according to claim 1 or 2, which is a structural adhesive.

9. The adhesive composition according to claim 1 or 2, which is a one-component heat-curing adhesive.

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