Adhesive composition

Abstract

To provide an adhesive composition which is improved in cold (low temperature) impact resistance, hot (thermal) adhesion, and toughness, while maintaining various properties so far required (for example, workability, durability, storage stability, etc.).SOLUTION: An adhesive composition comprises an epoxy resin (A), an epoxy resin toughener (B), an amine-based latent curing agent (D), and a filler (E), wherein (A) comprises at least an unmodified epoxy resin (A1) having a cyclic structure, (B) comprises at least two types of epoxy resin tougheners, and (B) comprises rubber particles (B1) with a core-shell structure having a diene polymer core.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a one-component thermosetting adhesive composition, and more particularly to an epoxy-based one-component thermosetting adhesive composition. [Background technology]

[0002] In order to reduce the weight of automobiles and improve ride comfort, the application of the weld bond method, which combines spot welding and structural adhesives to join steel sheets in automobile bodies, has expanded in recent years. Because automobiles are used in a wide variety of environments, adhesives used in automobiles are required to have a variety of properties, such as toughness, impact resistance, cold resistance, heat resistance, high adhesive strength to metal substrates, good coatability, and economical efficiency.

[0003] Patent Document 1 discloses a composition comprising (A) an epoxy resin containing a polyglycidyl ether, (B) rubber particles having a core-shell structure, (C) a supplemental impact modifier / toughener containing a prepolymer derived from the reaction of an amine-terminated polyether with an epoxy resin, (D) a heat-activated latent curing agent containing a substituted guanidine heat-activated latent curing agent, and (E) at least one chelate-modified epoxy resin having a group selected from the group consisting of a phosphorus-containing acid group, a carboxylic acid group, and a sulfur-containing acid group (see claims). Patent Document 1 also discloses that such a composition has improved impact resistance and / or good adhesion to oily metal substrates, and further discloses that a preferred application of the composition is the formation of structural bonds in vehicle assembly (see

[0001] to

[0003] ,

[0094] to

[0095] , examples, etc.).

[0004] Patent Document 2 discloses a curable resin composition containing, per 100 parts by mass of epoxy resin (A), 1 to 100 parts by mass of polymer fine particles (B) comprising a rubber-containing graft copolymer having an elastomer and a graft portion grafted to the elastomer, and 10 to 150 parts by mass of colloidal calcium carbonate (C) surface-treated with a silane coupling agent (see claims). Patent Document 2 discloses that the curable resin composition provides a cured product with excellent shear rate dependency of viscosity and excellent impact peel adhesion, and further that the composition can be used as an adhesive for structural components of automobiles and rolling stock (such as bullet trains and electric trains) (see

[0009] ,

[0012] ,

[0215] ,

[0217] , examples, etc.). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5307544 [Patent Document 2] Japanese Patent Application Publication No. 2020-164601 Summary of the Invention [Problem to be solved by the invention]

[0006] However, while these problems have been solved by adding a toughening agent to the epoxy resin to satisfy each required performance, it has not been possible to satisfy all of them due to the characteristics of each toughening agent. That is, in order to improve cold impact resistance, peel adhesion at room temperature and heat resistance have been sacrificed. There is a demand for adhesive compositions, preferably structural adhesives, that have improved cold impact resistance, hot adhesion, and peel adhesion at room temperature. [Means for solving the problem]

[0007] Conventional structural adhesives often contain epoxy resins modified with soft elastomers to compensate for the hard and brittle properties of the main component, bisphenol-type epoxy resin. However, while the selected elastomer can improve some performance, it can also fail to fully demonstrate the required cold and hot impact resistance and toughness.

[0008] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by adding an elastomer other than the rubber particles dispersed in the epoxy resin.

[0009] This specification includes the following forms. 1. An adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains at least (A1) an unmodified epoxy resin having a cyclic structure, the epoxy resin toughener (B) comprises at least two types of epoxy resin tougheners, The epoxy resin toughening agent (B) contains (B1) rubber particles having a core-shell structure having a core of a diene polymer (including a copolymer), Adhesive composition. 2. The composition according to the above item 1, wherein the shell of the rubber particles (B1) having a core-shell structure is a vinyl polymer. 3. The composition according to item 2 above, wherein the vinyl polymer of the shell of the core-shell rubber particles (B1) is a copolymer of monomers containing at least two or more selected from methyl methacrylate, glycidyl methacrylate, styrene, acrylonitrile, methacrylic acid, and glycidyl acrylate. 4. The composition according to any one of 1 to 3 above, wherein the mass ratio of the core to the shell (shell / core) of the core-shell structured rubber particles (B1) is 5 parts by mass or more and less than 60 parts by mass of the shell per 100 parts by mass of the core. 5. The composition according to any one of 1 to 4 above, wherein the vinyl polymer of the shell of the core-shell rubber particles (B1) contains at least a portion based on glycidyl methacrylate or glycidyl acrylate, and the epoxy groups contained in the core-shell rubber particles (B1) are contained in an amount of 0.2 parts by mass or more and less than 8 parts by mass per 100 parts by mass of the core-shell rubber particles (B1). 6. It may further contain a reactive diluent (C), 6. The composition according to any one of 1 to 5 above, which may contain 0 parts by mass (or no parts by mass) of the reactive diluent (C), or less than 15 parts by mass, relative to 100 parts by mass of the total of (A), (B), (C), and (D). 7. The content of the core-shell rubber particles (B1) is 7. The composition according to 6 above, wherein the total amount of (A), (B), (C) and (D) is 1 part by mass or more and less than 40 parts by mass, assuming that the total amount of (A), (B), (C) and (D) is 100 parts by mass. 8. The composition according to any one of 1 to 7 above, wherein the epoxy resin (A) further comprises a flexible epoxy resin in which polyalkylene oxide is added to both sides of a bisphenol skeleton and epichlorohydrin is further added. 9. The composition according to 8 above, wherein the total number of repeating polyoxyalkylene units in the flexible epoxy resin is 1 or more and 8 or less. 10. The composition according to any one of the above 1 to 9, wherein the amine-based latent curing agent (D) comprises at least one selected from the group consisting of dihydrazide compounds, imidazole compounds, and aliphatic polyamine compounds. 11. The composition according to any one of 1 to 10 above, wherein the epoxy resin toughening agent (B) comprises a blocked urethane prepolymer (B5) which is a reaction product of a polyalkylene polyol, a polyisocyanate, and a blocking agent. 12. The composition according to the above item 11, wherein the content of the block urethane prepolymer (B5) is within any of the following ranges. (i) 1 part by mass or more and less than 35 parts by mass per 100 parts by mass of (B1), (ii) The amount is 0.1 parts by mass or more and less than 6 parts by mass, with the total of (A), (B), (C), and (D) being 100 parts by mass. 13. The composition according to any one of 1 to 12 above, wherein the epoxy resin (A) further contains an NBR-modified epoxy resin (AB3) modified with an acrylonitrile-butadiene rubber (B3) having a functional group capable of reacting with an epoxy group, which is the epoxy resin toughening agent (B). 14. The composition according to the above item 13, wherein the content of the acrylonitrile-butadiene rubber (B3) having a functional group reactive with an epoxy group is within any of the following ranges. (iii) 1 part by mass or more and less than 30 parts by mass per 100 parts by mass of (B1), (iv) 0.1 parts by mass or more and less than 5 parts by mass, where the total of (A), (B), (C), and (D) is 100 parts by mass. 15. The composition according to 13 or 14 above, wherein the acrylonitrile content of the copolymer (B3) containing acrylonitrile and butadiene and having a functional group reactive with an epoxy group is 1% by mass or more and less than 25% by mass. 16. The composition described in any one of 1 to 15 above, wherein the epoxy resin (A) further contains a urethane-modified epoxy resin (AB4) modified with a urethane prepolymer (B4) having an active isocyanate group, which is the epoxy resin toughening agent (B). 17. The composition according to claim 16, wherein the content of the urethane prepolymer (B4) having an active isocyanate group is within any of the following ranges. (v) 1 part by mass or more and less than 35 parts by mass per 100 parts by mass of (B1); (vi) The total amount of (A), (B), (C), and (D) is 0.1 parts by mass or more and less than 5 parts by mass, where the total amount of (A), (B), (C), and (D) is 100 parts by mass. [Effects of the Invention]

[0010] The adhesive composition of an embodiment of the present invention provides an adhesive composition that has improved cold (low temperature) impact resistance, hot (hot) adhesion, and toughness while maintaining various properties that have traditionally been desired (e.g., workability, durability, storage stability, etc.). Thus, the adhesive composition of an embodiment of the present invention can be suitably used in manufacturing automobiles, and can be suitably used as a structural adhesive. DETAILED DESCRIPTION OF THE INVENTION

[0011] The adhesive composition of the present invention comprises: An adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains at least (A1) an unmodified epoxy resin having a cyclic structure, the epoxy resin toughener (B) comprises at least two types of epoxy resin tougheners, The epoxy resin toughening agent (B) contains (B1) rubber particles with a core-shell structure having a core of a diene polymer (including a copolymer).

[0012] In this specification, the epoxy resin (A) refers to a thermosetting resin that can be cured by forming a crosslinked network through the epoxy groups present therein, and is generally called an epoxy resin. There are no particular limitations on the epoxy resin as long as the adhesive composition targeted by the present invention can be obtained. The (A) epoxy resin may be, for example, a glycidyl ether type epoxy resin, a glycidyl amine type epoxy resin, or a glycidyl ester type epoxy resin.

[0013] (A) The epoxy resin preferably contains (A1) an unmodified epoxy resin having a cyclic structure. (A1) The unmodified epoxy resin having a cyclic structure is an epoxy resin having a cyclic structure (for example, a bisphenol structure), and the epoxy resin having a cyclic structure is not particularly limited as long as it is not modified and the adhesive composition intended by the present invention can be obtained. (A1) Examples of unmodified epoxy resins having a cyclic structure include bisphenol-type epoxy resins, naphthalene-type epoxy resins, and biphenyl-type epoxy resins, with biphenyl-type epoxy resins being preferred. More specific examples of bisphenol-type epoxy resins include diglycidyl ethers of bisphenol A, bisphenol F, brominated bisphenol A, bisphenol S, and bisphenol AD.

[0014] The viscosity of the (A1) unmodified epoxy resin having a cyclic structure at 25°C is preferably 1500 mPa·s or more, more preferably 2000 mPa·s or more and 25000 mPa·s or less, even more preferably 2500 mPa·s or more and 20000 mPa·s or less, and even more preferably 3000 mPa·s or more and 15000 mPa·s or less. The (A1) unmodified epoxy resin having a cyclic structure preferably has an epoxy equivalent weight of 150 g / eq to 800 g / eq, more preferably 160 g / eq to 500 g / eq, even more preferably 165 g / eq to 250 g / eq, and even more preferably 170 g / eq to 200 g / eq. When the (A1) unmodified epoxy resin having a cyclic structure has an epoxy equivalent weight of 150 g / eq to 800 g / eq, it has better workability. (A1) As the unmodified epoxy resin having a cyclic structure, commercially available products can be used, such as "jER (registered trademark) 828," "jER (registered trademark) 1001," and "jER (registered trademark) 807" manufactured by Mitsubishi Chemical Corporation.

[0015] The epoxy resin (A) may contain an epoxy resin ((A2) other epoxy resin) other than the unmodified epoxy resin (A1) having a cyclic structure. Examples include epoxy resins having a polyoxyalkylene skeleton, epoxy resins having a polyoxyalkylene skeleton and a bisphenol skeleton, and epoxy resins based on dimer acid or phthalic acid. Further examples include the epoxy resin portion of elastomer-modified epoxy resins contained in the epoxy resin toughener described below.

[0016] The (A) epoxy resin may contain a flexible epoxy resin in which polyalkylene oxide is attached to both sides of a bisphenol skeleton and epichlorohydrin is further attached. In this case, the adhesive composition according to an embodiment of the present invention may have a lower viscosity and have improved adhesion to oily surfaces.

[0017] The total number of oxyalkylene repeating units in the polyoxyalkylene structure of the flexible epoxy resin (A2) is preferably from 1 to 8, more preferably from 2 to 7, and even more preferably from 3 to 7. When the total number of oxyalkylene repeating units in the polyoxyalkylene structure of the flexible epoxy resin (A2) is from 1 to 8, the adhesive composition of the present invention can further suppress a decrease in water resistance.

[0018] In this specification, the epoxy resin toughener (B) is a polymeric material having elastomeric properties (rubber elasticity), and is not particularly limited as long as it can toughen a cured epoxy resin (enhance peel strength and / or impact resistance) and improve toughness, and can provide a composition that is the object of the present invention. The epoxy resin toughening agent (B) can be an elastomer that can be used for the purpose of toughening epoxy resins, and preferred examples thereof include polyurethane prepolymers having active isocyanates, butadiene-based polymers having functional groups (including copolymers with acrylonitrile, styrene, etc.), rubber particles having a core-shell structure, and block urethane prepolymers. The epoxy resin toughening agent can be used alone, mixed and / or dispersed in the composition, and further, one that is pre-reacted with the epoxy resin and becomes part of the epoxy resin can be used.

[0019] The adhesive composition of the present invention comprises rubber particles having a core-shell structure. Such particles generally have a core comprising a polymeric material with elastomeric or rubber-like properties (e.g., a glass transition temperature of less than about -40°C, preferably less than -50°C) surrounded by a shell comprising a non-elastomeric polymeric material (e.g., a thermoplastic or thermosetting / crosslinked polymer with a glass transition temperature above ambient temperature (e.g., a glass transition temperature above about 50°C)). The glass transition temperature can be measured by "dynamic mechanical analysis (DMA)." For example, the core preferably contains a diene-based homopolymer or copolymer (e.g., a homopolymer of butadiene or isoprene; a copolymer of at least one ethylenically unsaturated monomer selected from vinyl aromatic monomers, (meth)acrylonitrile, (meth)acrylates, etc., with butadiene and / or isoprene).

[0020] On the other hand, the shell may be a polymer of a vinyl-based monomer, and may include, for example, a polymer or copolymer formed from one or more vinyl-based monomers capable of forming a polymer having a sufficiently high glass transition temperature ((meth)acrylates (e.g., methyl methacrylate (MMA) and methyl acrylate (MA)), vinyl aromatic monomers (e.g., styrene (ST)), vinyl cyanides (e.g., acrylonitrile (AN)), unsaturated acids and anhydrides (e.g., acrylic acid (AA), epoxy group-containing monomers (e.g., glycidyl acrylate (GA) and glycidyl methacrylate (GMA)), (meth)acrylamides (e.g., methacrylamide (AMA)), etc.). The shell is

[0021] The epoxy resin toughener (B) preferably contains rubber particles (B1) having a core-shell structure with a core made of a diene polymer (including copolymer). The rubber particles (B1) having a core-shell structure with a core made of a diene polymer (including copolymer) are not particularly limited as long as the rubber particles have a core-shell structure and the core is made of a diene polymer (including copolymer), and the adhesive composition of the present invention is obtained.

[0022] The shell of the core-shell rubber particles (B1) is preferably a polymer of a vinyl monomer, and the core is preferably a diene polymer, in which case the adhesive composition according to an embodiment of the present invention has better low-temperature impact resistance.

[0023] The shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer preferably contains at least two selected from methyl methacrylate (MMA), glycidyl methacrylate (GMA), styrene (ST), acrylonitrile (AN), methacrylic acid (MA), and glycidyl acrylate (GA). In this case, the adhesive composition according to an embodiment of the present invention has excellent toughness (impact resistance, peel strength, etc.) due to the interaction between the core and the epoxy resin.

[0024] The shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer preferably contains at least MMA, and the amount of MMA contained per 100 parts by mass of the shell is preferably 10 parts by mass or more but less than 80 parts by mass, more preferably 20 parts by mass or more but less than 65 parts by mass, and even more preferably 30 parts by mass or more but less than 50 parts by mass. When the shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer contains at least MMA, and the amount of MMA contained per 100 parts by mass of the shell is 10 parts by mass or more but less than 80 parts by mass, the adhesive composition of the present invention has better toughness (impact resistance, peel strength, etc.).

[0025] The shell of the rubber particles (B1) having a core-shell structure is a polymer of a vinyl monomer, and the vinyl monomer preferably contains at least GMA or GA. The shell of the rubber particles (B1) having a core-shell structure preferably contains 1 part by mass or more but less than 20 parts by mass of epoxy groups per 100 parts by mass of the shell, more preferably 3 parts by mass or more but less than 17 parts by mass, and even more preferably 5 parts by mass or more but less than 15 parts by mass. The shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer contains at least GMA or GA. When the epoxy groups contained in the core-shell rubber particles (B1) are contained in an amount of 1 part by mass or more and less than 20 parts by mass per 100 parts by mass of the shell of the core-shell rubber particles (B1), the adhesive composition of an embodiment of the present invention has superior toughness (impact resistance, peel strength, etc.).

[0026] The epoxy groups contained in the core-shell rubber particles (B1) are preferably contained in an amount of 0.2 parts by mass or more and less than 8 parts by mass, more preferably 0.5 parts by mass or more and less than 5 parts by mass, and even more preferably 0.9 parts by mass or more and less than 3 parts by mass, per 100 parts by mass of the core-shell rubber particles (B1). When the shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, the vinyl monomer contains at least GMA or GA, and the epoxy groups contained in the core-shell rubber particles (B1) are contained in an amount of 0.2 parts by mass or more and less than 8 parts by mass per 100 parts by mass of the core-shell rubber particles (B1), the adhesive composition of an embodiment of the present invention has superior toughness (impact resistance, peel strength, etc.).

[0027] The shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer may contain at least a small amount of acrylonitrile (AN), preferably containing no AN or less than 10 parts by mass of AN per 100 parts by mass of the shell, more preferably less than 7 parts by mass, and even more preferably less than 5 parts by mass. When the shell of the core-shell rubber particles (B1) is a polymer of a vinyl monomer, and the vinyl monomer does not contain AN or contains less than 10 parts by mass of AN per 100 parts by mass of the shell, the adhesive composition of the present invention can better ensure storage stability.

[0028] The mass ratio of the core to the shell (shell / core) of the rubber particles (B1) having a core-shell structure is preferably 5 parts by mass or more but less than 60 parts by mass, more preferably 10 parts by mass or more but less than 40 parts by mass, and even more preferably 15 parts by mass or more but less than 30 parts by mass, per 100 parts by mass of the core. When the mass ratio of the core to the shell (shell / core) of the rubber particles (B1) having a core-shell structure is 5 parts by mass or more but less than 60 parts by mass of the shell per 100 parts by mass of the core, the adhesive composition of an embodiment of the present invention is superior in toughness (impact resistance, peel strength, etc.).

[0029] The polymers or copolymers used in the shell may have acid groups that are ionically crosslinked by metal carboxylate structures (e.g., by forming salts of divalent metal cations). The shell polymers or copolymers may also be covalently crosslinked by using monomers with two or more double bonds per molecule. Additionally, other rubbery polymers, including polybutyl acrylate or polysiloxane elastomers (e.g., polydimethylsiloxane, particularly crosslinked polydimethylsiloxane), may also be used as appropriate for the core. The rubber particles may be composed of two or more layers (e.g., a central core of one rubbery material surrounded by a second core of a different rubbery material, or a rubbery core surrounded by two shells of different compositions, or the rubber particles may have a soft-core, hard-shell, soft-shell, hard-shell structure).

[0030] Furthermore, the shell of the core-shell structure can be appropriately selected taking into consideration compatibility with the epoxy resin, etc., and it does not necessarily have to be a two-layer structure, but may be a multi-layer structure such as a three-layer structure, or a gradient structure in which the concentrations of the core and shell change stepwise.

[0031] The polymer or copolymer used in the core and the polymer or copolymer used in the shell may contain at least one functional group selected from, for example, an acid anhydride group, a carboxy group, an amino group, an imino group, and an epoxy group. Furthermore, the core and the shell may be obtained by a graft reaction.

[0032] Furthermore, rubber particles having a core-shell structure can be used by preparing a masterbatch in which the rubber particles are dispersed in the epoxy resin (A). Commercially available masterbatch (A+B) in which the rubber particles are dispersed in the epoxy resin (A) can be used. Examples of masterbatches in which rubber particles (B1) having a core-shell structure with a diene polymer (including copolymer) core are dispersed in an epoxy resin (A) include Kaneka Ace MX-153 (trade name), MX-154 (trade name), and MX-257 (trade name) manufactured by Kaneka.

[0033] The adhesive composition according to an embodiment of the present invention may contain a reactive diluent (C) described below (it may or may not contain (C)), and the content of the core-shell rubber particles (B1) is preferably 1 part by mass or more but less than 40 parts by mass, more preferably 5 parts by mass or more but less than 30 parts by mass, and even more preferably 7 parts by mass or more but less than 25 parts by mass, relative to 100 parts by mass of the total of (A), (B), (C), and (D). When the content of the core-shell rubber particles (B1) is 1 part by mass or more and less than 40 parts by mass, where the total of (A), (B), (C), and (D) is 100 parts by mass, the adhesive composition according to an embodiment of the present invention has better impact resistance.

[0034] The epoxy resin toughening agent (B) may contain acrylic elastomer particles (B2). The acrylic elastomer particles (B2) contain a core composed of an acrylic resin elastomer for toughening and a shell for improving compatibility with the epoxy resin. The acrylic elastomer particles (B2) are not particularly limited as long as they can provide the adhesive composition of the present invention. Commercially available acrylic elastomer particles (B2) may be used, such as ZEFIAC F-351 (trade name) manufactured by Aica Kogyo Co., Ltd.

[0035] The epoxy resin toughening agent (B) may contain a blocked urethane prepolymer (B5) in which an active isocyanate is blocked with a thermal-release blocking agent. The blocked urethane prepolymer (B3) may be a blocked urethane prepolymer in which a reaction product of a polyol having elastomeric properties and a polyisocyanate is blocked with a blocking agent. The blocked urethane prepolymer (B5) is not particularly limited as long as the adhesive composition intended by the present invention can be obtained.

[0036] When the epoxy resin toughening agent (B) contains a block urethane prepolymer (B5), the adhesive composition according to an embodiment of the present invention has superior impact resistance.

[0037] Examples of polyols include commercially available polyether polyols, polyester polyols, castor oil polyols, polybutadiene polyols, polyacrylic polyols, polyolefin polyols, etc. The number average molecular weight is not particularly limited, but is preferably from 1,000 to 20,000, more preferably from 1,500 to 15,000, and particularly preferably from 2,000 to 10,000. Elastomers having a linear or branched structure can also be used.

[0038] Examples of polyether polyols include polymers containing polypropylene glycol or polytetramethylene glycol as the main component. Examples of polyester polyols include polymers obtained by polycondensation of (i) one or more selected from the group consisting of polybasic acids such as maleic acid, fumaric acid, adipic acid, and phthalic acid, and their acid anhydrides, with (ii) one or more selected from the group consisting of polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, and neopentyl glycol, in the presence of an esterification catalyst. Other examples include (a) ring-opening polymers such as ε-caprolactone and valerolactone, and (b) active hydrogen compounds having two or more active hydrogen atoms, such as polycarbonate diol and castor oil.

[0039] Examples of polyacrylic polyols include polyols having a (meth)acrylic acid alkyl ester (co)polymer skeleton and having hydroxyl groups in the molecule. As the polyacrylic polyol, particularly preferred is a polyacrylic polyol obtained by copolymerizing a hydroxyl group-containing (meth)acrylic acid alkyl ester monomer such as 2-hydroxyethyl methacrylate. Examples of polydiene polyols include polybutadiene polyols, polyisoprene polyols, polychloroprene polyols, etc. Polybutadiene polyols are particularly preferred.

[0040] Examples of polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, bis(isocyanatomethyl)norbornane, 1,4-bis(isocyanatomethyl)benzene, bis(4-isocyanatocyclohexyl)methane, and polymers of these diisocyanates.

[0041] Examples of the blocking agent include amine-based blocking agents, oxime-based blocking agents, lactam-based blocking agents, active methylene-based blocking agents, alcohol-based blocking agents, mercaptan-based blocking agents, amide-based blocking agents, imide-based blocking agents, heterocyclic aromatic compound-based blocking agents, hydroxy-functional (meth)acrylate-based blocking agents, and phenol-based blocking agents. Among these, amine-based blocking agents, lactam-based blocking agents, and phenol-based blocking agents are preferred, and phenol-based blocking agents are more preferred.

[0042] Examples of the amine-based blocking agent include butylamine, isopropylamine, dodecylamine, cyclohexylamine, aniline, benzylamine, dibutylamine, diisopropylamine, dicyclohexylamine, diphenylamine, dibenzylamine, morpholine, and piperidine. Examples of the oxime-based blocking agent include formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, and cyclohexane oxime. Examples of the lactam-based blocking agent include ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-butyrolactam.

[0043] Examples of the active methylene-based blocking agent include ethyl acetoacetate, acetylacetone, etc. Examples of the alcohol-based blocking agent include methanol, ethanol, propanol, isopropanol, butanol, amyl alcohol, cyclohexanol, 1-methoxy-2-propanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methyl glycolate, butyl glycolate, diacetone alcohol, methyl lactate, and ethyl lactate.

[0044] Examples of the mercaptan-based blocking agent include butyl mercaptan, hexyl mercaptan, decyl mercaptan, t-butyl mercaptan, thiophenol, methylthiophenol, and ethylthiophenol. Examples of the amide-based blocking agent include acetic acid amide and benzamide. Examples of the imide-based blocking agent include succinimide and maleimide.

[0045] Examples of the heterocyclic aromatic compound-based blocking agent include imidazoles such as imidazole and 2-ethylimidazole; pyrroles such as pyrrole, 2-methylpyrrole, and 3-methylpyrrole; pyridines such as pyridine, 2-methylpyridine, and 4-methylpyridine; and diazabicycloalkenes such as diazabicycloundecene and diazabicyclononene. Examples of the hydroxy-functional (meth)acrylate-based blocking agent include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0046] Examples of the phenol-based blocking agent include phenol, cresol, xylenol, chlorophenol, ethylphenol, allylphenol (particularly, o-allylphenol), resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AD, bisphenol F, tetramethylbiphenol, and 2,2'-diallyl-bisphenol A.

[0047] In addition, commercially available products can be used as the block urethane prepolymer (B5), such as QR-9466 (trade name) manufactured by ADEKA Corporation, DY965 (trade name) manufactured by HUNTSMAN Corporation, and Takenate B-7005 manufactured by Mitsui Chemicals, Inc.

[0048] The adhesive composition according to an embodiment of the present invention may contain a reactive diluent (C) described below (it may or may not contain (C)), and the content of the block urethane prepolymer (B5) preferably satisfies either the range (i) or (ii) below. (i) (B1) is 1 part by mass or more and less than 35 parts by mass per 100 parts by mass, (ii) 0.1 parts by mass or more and less than 6 parts by mass per 100 parts by mass of the total of (A), (B), (C), and (D). In this case, the adhesive composition according to the embodiment of the present invention has superior impact resistance.

[0049] The content of the block urethane prepolymer (B5) more preferably satisfies either the range (i) or (ii) below. (i) (B1) is 1.5 parts by mass or more and less than 30 parts by mass per 100 parts by mass, (ii) 0.2 parts by mass or more and less than 5 parts by mass per 100 parts by mass of the total of (A), (B), (C), and (D). It is even more preferable that the content of the block urethane prepolymer (B5) satisfies either the range (i) or (ii) below. (i) (B1) is 2 parts by mass or more and less than 20 parts by mass per 100 parts by mass, (ii) 0.3 parts by mass or more and less than 4 parts by mass per 100 parts by mass of the total of (A), (B), (C), and (D).

[0050] The epoxy resin toughener (B) may be a part of the epoxy resin (A), for example, the elastomer portion of a modified epoxy resin (AB) modified with an elastomer. An example of such an elastomer-modified epoxy resin is an elastomer-modified epoxy resin (AB) obtained by preliminarily reacting an excess of the epoxy resin (A) with a reactive group contained in the elastomer. Such an elastomer-modified epoxy resin (AB) contains a portion corresponding to the epoxy resin (A) and a portion corresponding to the elastomer (B), and is not particularly limited as long as it can produce the adhesive composition desired by the present invention.

[0051] An example of the elastomer-modified epoxy resin (AB) having an elastomer portion and an epoxy resin portion is acrylonitrile-butadiene rubber (NBR)-modified epoxy resin (AB3).

[0052] Incidentally, for example, carboxyl-terminated acrylonitrile-butadiene copolymer (CTBN) products with various acrylonitrile contents are commercially available as carboxyl-containing acrylonitrile-butadiene rubbers. Specific examples include Hypox 1300x13 (trade name), Hypox 1300x8 (trade name), and Hypox 1300x31 (trade name) manufactured by Huntsman. Furthermore, examples of carboxyl group-containing NBR obtained by copolymerizing acrylonitrile, butadiene, and acrylic acid include DN601 manufactured by Zeon Corporation.

[0053] Butadiene rubber-modified epoxy resins can be obtained by reacting carboxy-terminated butadiene rubber with an excess of epoxy resin. Specific examples of butadiene rubber-modified epoxy resins include Hypox RA1340 (trade name), Hypox RA840 (trade name), and Hypox RA16213 (trade name), manufactured by Huntsman. Acrylonitrile-butadiene rubber modified epoxy resin (AB3) can be obtained by reacting a carboxy-terminated acrylonitrile-butadiene rubber with an excess of epoxy resin.

[0054] The epoxy resin (A) preferably further contains an acrylonitrile-butadiene rubber (NBR)-modified epoxy resin (AB3), in which case the adhesive composition according to an embodiment of the present invention has better adhesion to oily surfaces.

[0055] The adhesive composition according to an embodiment of the present invention may contain a reactive diluent (C) described below (it may or may not contain (C)), and it is preferable that the content of the acrylonitrile-butadiene rubber portion (B3) (corresponding to an acrylonitrile-butadiene rubber having an epoxy resin reactive group) satisfies either (iii) or (iv) below. (iii) 1 part by mass or more and less than 30 parts by mass per 100 parts by mass of (B1), (iv) The amount of (A), (B), (C), and (D) is 0.1 parts by mass or more and less than 5 parts by mass, relative to 100 parts by mass of the total of (A), (B), (C), and (D). In this case, the adhesive composition according to an embodiment of the present invention has superior adhesion to oily surfaces.

[0056] It is more preferable that the content of the acrylonitrile-butadiene rubber portion (corresponding to an acrylonitrile-butadiene rubber having an epoxy resin reactive group) (B3) satisfies either the following (iii) or (iv). (iii) 2 parts by mass or more and less than 20 parts by mass per 100 parts by mass of (B1); (iv) The content is 0.3 parts by mass or more and less than 4 parts by mass per 100 parts by mass of the total of (A), (B), (C), and (D). It is even more preferable that the content of the acrylonitrile-butadiene rubber portion (corresponding to an acrylonitrile-butadiene rubber having an epoxy resin reactive group) (B3) satisfies either the following (iii) or (iv). (iii) 3 parts by mass or more and less than 15 parts by mass per 100 parts by mass of (B1); (iv) The content is 0.5 parts by mass or more and less than 3 parts by mass per 100 parts by mass of the total of (A), (B), (C), and (D).

[0057] The content of the acrylonitrile-butadiene rubber portion (B3) is (ii) The content of the acrylonitrile-butadiene rubber portion (B3) is preferably 0.1 parts by mass or more and less than 5 parts by mass, more preferably 0.3 parts by mass or more and less than 4 parts by mass, and even more preferably 0.5 parts by mass or more and less than 3 parts by mass, relative to 100 parts by mass of the total of (A), (B), (C), and (D). When the content of the acrylonitrile-butadiene rubber portion (B3) is 0.1 parts by mass or more and less than 5 parts by mass, relative to 100 parts by mass of the total of (A), (B), (C), and (D), the adhesive composition according to an embodiment of the present invention has superior adhesion to oily surfaces.

[0058] The acrylonitrile content of the acrylonitrile-butadiene rubber (acrylonitrile-butadiene rubber portion) (B3) having a functional group reactive with an epoxy group is preferably 1% by mass or more and less than 30% by mass, more preferably 5% by mass or more and less than 25% by mass, and even more preferably 10% by mass or more and less than 20% by mass. When the acrylonitrile content of the acrylonitrile-butadiene rubber (B3) having a functional group reactive with an epoxy group is 1% by mass or more and less than 30% by mass, the adhesive composition of the present embodiment has better adhesion to oily surfaces.

[0059] Another example of the elastomer-modified epoxy resin (AB) is a urethane-modified epoxy resin (AB4) obtained by pre-reacting a urethane prepolymer obtained by pre-reacting a polyol and a polyisocyanate with the hydroxyl groups of an epoxy resin. Specifically, the polyols described above (in the section on block urethane prepolymers) can be used as the polyol, and the polyisocyanates described above (in the section on block urethane prepolymers) can be used as the polyisocyanate. Specific examples include EPU-6 and EPU-73B manufactured by ADEKA Corporation.

[0060] Preferably, the epoxy resin (A) further comprises a urethane-modified epoxy resin (AB4) modified with a urethane prepolymer (B4) having an active isocyanate group, which corresponds to the epoxy resin toughener (B). In this case, the adhesive composition according to an embodiment of the present invention has superior peel strength at room temperature.

[0061] The adhesive composition according to an embodiment of the present invention may contain a reactive diluent (C) described below (it may or may not contain (C)), and the content of the urethane prepolymer (B4) having an active isocyanate group is preferably within the range of either (v) or (vi) below. (v) 1 part by mass or more and less than 35 parts by mass per 100 parts by mass of (B1); (vi) The total amount of (A), (B), (C), and (D) is 0.1 parts by mass or more and less than 5 parts by mass, where the total amount of (A), (B), (C), and (D) is 100 parts by mass. In this case, the adhesive composition according to an embodiment of the present invention has superior peel strength at room temperature.

[0062] The content of the urethane prepolymer (B4) having an active isocyanate group is more preferably within the range of either (v) or (vi) below. (v) 2 parts by mass or more and less than 30 parts by mass per 100 parts by mass of (B1); (vi) The total amount of (A), (B), (C), and (D) is 0.3 parts by mass or more and less than 4 parts by mass, where the total amount of (A), (B), (C), and (D) is 100 parts by mass.

[0063] It is even more preferable that the content of the urethane prepolymer (B4) having an active isocyanate group is within either the range of (v) or (vi) below. (v) 3 parts by mass or more and less than 20 parts by mass per 100 parts by mass of (B1); (vi) The amount is 0.5 parts by mass or more and less than 3 parts by mass, with the total of (A), (B), (C), and (D) being 100 parts by mass.

[0064] The epoxy resin toughener (B) is preferably contained in an amount of 5 parts by mass or more but less than 60 parts by mass, more preferably 8 parts by mass or more but less than 40 parts by mass, even more preferably 10 parts by mass or more but less than 30 parts by mass, and even more preferably 15 parts by mass or more but less than 25 parts by mass, relative to 100 parts by mass of the total of the epoxy resin (A), the epoxy resin toughener (B), the reactive diluent (C), and the amine-based latent curing agent (D). When the epoxy resin toughener (B) is contained in an amount of 5 parts by mass or more but less than 60 parts by mass, relative to 100 parts by mass of the total of the epoxy resin (A), the epoxy resin toughener (B), the reactive diluent (C), and the amine-based latent curing agent (D), cold impact resistance, hot adhesion, and toughness can be further improved.

[0065] The epoxy resin toughening agent (B) is preferably contained in an amount of 5 parts by mass or more but less than 40 parts by mass, more preferably 6 parts by mass or more but less than 30 parts by mass, even more preferably 7 parts by mass or more but less than 25 parts by mass, and even more preferably 10 parts by mass or more but less than 20 parts by mass per 100 parts by mass of the curable composition. When the epoxy resin toughener (B) is contained in an amount of 5 parts by mass or more and less than 40 parts by mass per 100 parts by mass of the curable composition, cold impact resistance, hot adhesion, and toughness can be further improved.

[0066] The adhesive composition of the present embodiment may contain a reactive diluent (C). In this specification, the reactive diluent (C) refers to a diluent that has one epoxy group, reacts with the epoxy resin (A) via that epoxy group, and is capable of reducing the viscosity, and is not particularly limited as long as the adhesive composition intended by the present invention can be obtained. The viscosity (25°C) of the reactive diluent (C) may be 1 mPa·s or more and 100 mPa·s or less, 5 mPa·s or more and 80 mPa·s or less, 10 mPa·s or more and 60 mPa·s or less, 15 mPa·s or more and 50 mPa·s or less, or 20 mPa·s or more and 40 mPa·s or less. The reactive diluent (C) is a low molecular weight compound, and its molecular weight may be 120 or more and 550 or less, 150 or more and 450 or less, 200 or more and 400 or less, 220 or more and 350 or less, or 250 or more and 320 or less.

[0067] Examples of the reactive diluent (C) include a compound having one glycidoxy group, a compound having one glycidylamino group, and a compound having one glycidoxycarbonyl (glycidyl ester) group. The reactive diluent (C) preferably contains a compound having one glycidoxy group.

[0068] The total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D) is taken as 100 parts by mass, and the reactive diluent (C) may be 0 part (not included) or less than 15 parts by mass, preferably 1 part by mass or more but less than 15 parts by mass, more preferably 2 parts by mass or more but less than 10 parts by mass, even more preferably 3 parts by mass or more but less than 8 parts by mass, and even more preferably 4 parts by mass or more but less than 6 parts by mass. When the total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D) is 100 parts by mass, and the reactive diluent (C) is contained in an amount of 1 part by mass or more but less than 15 parts by mass, the viscosity is lowered and the heat resistance is excellent.

[0069] The amount of reactive diluent (C) per 100 parts by mass of the adhesive composition is preferably 0.5 parts by mass or more but less than 10 parts by mass, more preferably 1 part by mass or more but less than 8 parts by mass, even more preferably 2 parts by mass or more but less than 6 parts by mass, and even more preferably 3 parts by mass or more but less than 5 parts by mass. When the reactive diluent (C) is contained in an amount of 0.5 parts by mass or more and less than 10 parts by mass per 100 parts by mass of the adhesive composition, the adhesive composition has lower viscosity and better heat resistance.

[0070] The adhesive composition according to an embodiment of the present invention may contain an amine-based latent curing agent (D). In this specification, the term "amine-based latent curing agent (D)" refers to an amine-based curing agent for epoxy resins that does not have a curing action at room temperature but functions as a curing agent when heated to a certain temperature (for example, 170°C, preferably 150°C), and is not particularly limited as long as the adhesive composition intended by the present invention can be obtained.

[0071] Specific examples of the amine-based latent curing agent (D) include dicyandiamide; Dihydrazide compounds such as adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, dodecanediohydrazide, 1,3-bis(hydrazinocarboethyl)-5-isopropylhydantoin, eicosanedioic acid dihydrazide, hydroquinone diglycolic acid dihydrazide, resorcinol diglycolic acid dihydrazide, and 4,4'-ethylidenebisphenol diglycolic acid dihydrazide; 4,4'-Diaminodiphenyl sulfone; imidazole compounds such as imidazole, 2-n-heptadecylimidazole, and 2-undecylimidazole; melamine; triazine compounds such as 2,4-diamino-6-(2'-methylimidazolyl(1'))-ethyl-o-triazine; Benzoguanamine; Dialkyl urea compounds such as N,N-dialkyl urea compounds such as N,N-dimethyl-N'-(3,4-dichlorophenyl)urea; N,N'-dialkylthiourea compounds; Aromatic polyamine compounds such as diaminodiphenylmethane and diaminobiphenyl; Aliphatic polyamine compounds having two or more primary or secondary amino groups in the molecular chain, such as dodecanediamine, decanediamine, octanediamine, tetradecanediamine, hexadecanediamine, epoxy resin-modified aliphatic amines, polyisocyanate-modified aliphatic amines, and aliphatic amines modified by Michael addition reaction; Examples include guanidine derivatives such as cyanoguanidine. Furthermore, these amine-based latent curing agents may be used after being neutralized with powder coating or phenol, etc., in order to improve storage stability.

[0072] The amine-based latent curing agent (D) preferably contains at least one selected from a dialkyl urea compound, a dihydrazide compound, an imidazole compound, and an aliphatic polyamine compound, and more preferably contains at least an aliphatic polyamine compound as an essential component.

[0073] When the amine-based latent curing agent (D) contains at least one selected from the group consisting of dialkyl urea compounds, dihydrazide compounds, imidazole compounds, and aliphatic polyamine compounds, the adhesive composition according to an embodiment of the present invention exhibits an excellent balance between low-temperature impact resistance, curability, and storage stability.

[0074] Commercially available products can be used as the amine-based latent curing agent (D). Examples include CG-NA (trade name) manufactured by Air Products Co., Ltd., EH-4030s (trade name) manufactured by ADEKA Corporation, ADH (adipic acid dihydrazide, trade name) manufactured by Otsuka Chemical Co., Ltd., EH-3731s (trade name) manufactured by ADEKA Corporation, Dyhard UR200 (a urea compound, trade name) manufactured by AlzChem Corporation, DDH (dodecanedioic acid dihydrazide, trade name) manufactured by Otsuka Chemical Co., Ltd., N-12 (dodecanedioic acid dihydrazide, trade name) manufactured by Japan Finechem Co., Ltd., isophthalic acid dihydrazide (trade name) manufactured by Tokyo Chemical Industry Co., Ltd., and Ancamine 2014FG (a modified aliphatic polyamine compound, trade name) manufactured by ADEKA Corporation.

[0075] The adhesive composition according to an embodiment of the present invention may contain the reactive diluent (C) (it may or may not contain (C)), and preferably contains 1 part by mass or more but less than 25 parts by mass of the amine-based latent curing agent (D) relative to 100 parts by mass of the total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D), more preferably 2 parts by mass or more but less than 20 parts by mass, even more preferably 3 parts by mass or more but less than 15 parts by mass, and even more preferably 5 parts by mass or more but less than 12 parts by mass. When the total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D) is 100 parts by mass, and the amine-based latent curing agent (D) is contained in an amount of 1 part by mass or more and less than 25 parts by mass, the curability and storage stability are superior.

[0076] The adhesive composition preferably contains 1 part by mass or more and less than 20 parts by mass of the amine-based latent curing agent (D) per 100 parts by mass of the adhesive composition, more preferably 2 parts by mass or more and less than 15 parts by mass, even more preferably 3 parts by mass or more and less than 12 parts by mass, and even more preferably 4 parts by mass or more and less than 10 parts by mass. When the amine-based latent curing agent (D) is contained in an amount of 1 part by mass or more and less than 20 parts by mass per 100 parts by mass of the curable composition, the curability and storage stability are more excellent.

[0077] The adhesive composition of the present embodiment may further contain a filler (E). In this specification, a filler is a compound that increases the weight of the adhesive composition of an embodiment of the present invention and can impart a certain degree of strength to a film formed from the adhesive composition, and in some cases can contribute to viscosity adjustment or weight reduction, and is not particularly limited as long as the adhesive composition intended by the present invention can be obtained.

[0078] Examples of fillers include calcium carbonate (heavy calcium carbonate, precipitated calcium carbonate, surface-treated calcium carbonate, etc.), magnesium carbonate, alkaline earth metal carbonates and sulfates such as barium sulfate, mica, graphite, talc, clay, glass flakes (glass beads), vermiculite, kaolinite, wollastonite (acicular calcium metasilicate), silica, diatomaceous earth, gypsum, cement, converter slag, shirasu, zeolite, cellulose powder, powdered rubber, zonolite, potassium titanate, bentonite, aluminum nitride, silicon nitride, zinc oxide, titanium oxide, alumina, zinc oxide, iron oxide, magnesium oxide, titanium oxide, magnesium hydroxide, hydroxide Examples of fillers include aluminum oxide, calcium silicate, calcium carbonate whiskers (needle-shaped calcium carbonate), ceramic short fibers or whiskers thereof, rock wool short fibers, glass fiber short fibers, potassium titanate short fibers, calcium silicate short fibers, aluminum silicate, carbon fiber short fibers, aramid fiber short fibers, mineral fibers such as sepiolite, fibrous fillers such as various whiskers, hollow fillers such as glass balloons, silica balloons, resin balloons, and inorganic carbon hollow spheres, organic hollow fillers such as plastic balloons made of organic synthetic resins such as vinylidene chloride and acrylonitrile, and metallic fillers such as aluminum filler.

[0079] The adhesive composition according to an embodiment of the present invention may contain a reactive diluent (C) described below (it may or may not contain (C)), and preferably contains 10 parts by mass or more but less than 250 parts by mass of the filler (E) relative to 100 parts by mass of the total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D). It is more preferable that the adhesive composition contains 20 parts by mass or more but less than 180 parts by mass, even more preferably that the adhesive composition contains 40 parts by mass or more but less than 120 parts by mass, and even more preferably that the adhesive composition contains 60 parts by mass or more but less than 100 parts by mass. When the filler (E) is contained in an amount of 10 parts by mass or more but less than 250 parts by mass per 100 parts by mass of the total of the epoxy resin (A), the epoxy resin toughening agent (B), the reactive diluent (C), and the amine-based latent curing agent (D), the workability (dripping and dischargeability after application) is superior.

[0080] The adhesive composition preferably contains 5 parts by mass or more and less than 80 parts by mass of filler (E) per 100 parts by mass of the adhesive composition, more preferably 10 parts by mass or more and less than 70 parts by mass, even more preferably 15 parts by mass or more and less than 60 parts by mass, and even more preferably 20 parts by mass or more and less than 50 parts by mass. When the adhesive composition contains 5 parts by mass or more and less than 80 parts by mass of filler (E) per 100 parts by mass of the adhesive composition, the adhesive composition has better workability (dripping and dischargeability after application).

[0081] The adhesive composition according to an embodiment of the present invention may contain an additive (F), such as a plasticizer, a diluent, a surfactant, or other additives.

[0082] In the embodiment of the present invention, the plasticizer is not particularly limited as long as it can increase the plasticity and soften the epoxy resin composition, which is the object of the present invention. Examples of the plasticizer include alkylbenzyl phthalate, dimethylcyclohexyl phthalate, phthalic polyester, benzoic acid ester, dialkyl phthalate, dialkyl cyclohexane dicarboxylate, and trimellitic acid triester.

[0083] In an embodiment of the present invention, the diluent is not particularly limited as long as it can impart fluidity to the adhesive composition of an embodiment of the present invention and, excluding the reactive diluent (C) described above, can provide the adhesive composition intended by the present invention. Examples of diluents include hydrocarbon solvents such as paraffinic solvents, isoparaffinic solvents, naphthenic solvents, and aromatic solvents.

[0084] In an embodiment of the present invention, examples of other additives include moisture absorbents (calcium oxide, molecular sieves, etc.), thixotropic agents (organic bentonite, fumed silica, aluminum stearate, metallic soaps, castor oil derivatives, etc.), stabilizers (2,6-di-t-butyl-4-methylphenol, 2,2-methylene-bis(4-methyl-6-t-butylphenol), nickel dibutyldithiocarbamate, etc.), curing accelerators (dibutyltin dilaurate, lead octoate, bisnath octoate, etc.), coupling agents such as silane or titanium, foaming agents, etc. The other additives can be used appropriately without any particular limitations, as long as the adhesive composition intended by the present invention can be obtained.

[0085] The adhesive composition of the present invention can be produced by appropriately heating and mixing the above-mentioned components. The apparatus and method for mixing the above-mentioned components are not particularly limited as long as they can produce the adhesive composition of the present invention. Specific examples of such mixing devices that can be used include a twin-screw mixer, a planetary mixer, a sigma mixer, a kneader, an attritor, a grain mill, a roll, and a dissolver. It is more preferable to use a twin-screw mixer, a planetary mixer or a sigma mixer for mixing, since the use of a twin-screw mixer, a planetary mixer or a sigma mixer makes it possible to more efficiently disperse high-viscosity materials. Furthermore, the mixing can be carried out using a container capable of mixing, for example, in a tank, a vessel, or the like.

[0086] The adhesive composition of the present invention is preferably cured at 170°C for 20 minutes to have excellent shear adhesive strength, T-peel strength, and low-temperature impact resistance. Detailed evaluation methods are described in the Examples.

[0087] The hot shear strength of the cured product of the adhesive composition according to an embodiment of the present invention is preferably 10 MPa or more in a 100°C atmosphere, more preferably 20 MPa or more in a 100°C atmosphere, even more preferably 10 MPa or more in a 120°C atmosphere, and particularly preferably 20 MPa or more in a 120°C atmosphere. When the hot shear adhesive strength of the cured product of the adhesive composition of an embodiment of the present invention is 10 MPa or more in an atmosphere of 100°C, the adhesive composition of an embodiment of the present invention has the advantageous effect of being excellent as an adhesive with high toughness.

[0088] The T-peel strength (23°C) of the cured product of the adhesive composition according to an embodiment of the present invention is preferably 100 N / 25 mm or more, more preferably 150 N / 25 mm or more, even more preferably 200 N / 25 mm or more, and particularly preferably 250 N / 25 mm or more. When the T-peel adhesion strength (23°C) of the cured product of the adhesive composition of an embodiment of the present invention is 100 N / 25 mm or more, the adhesive composition of an embodiment of the present invention has the advantageous effect of being excellent in toughness.

[0089] The impact strength of a cured product of the adhesive composition according to an embodiment of the present invention is preferably 20 N or more in an atmosphere of 23°C, more preferably 35 N or more in an atmosphere of 23°C, even more preferably 20 N or more in an atmosphere of -30°C, and particularly preferably 35 N or more in an atmosphere of -30°C. When the impact resistance strength of the cured product of the adhesive composition of an embodiment of the present invention is 20 N or more in an atmosphere of 23°C, the adhesive composition of an embodiment of the present invention has the advantageous effect of being excellent in impact resistance (automobile collision safety). When the impact resistance strength of the cured product of the adhesive composition of an embodiment of the present invention is 35 N or more in an atmosphere of -30°C, the adhesive composition of an embodiment of the present invention has the advantageous effect of being excellent in impact resistance (automobile collision safety).

[0090] The adhesive composition of the present embodiment can be applied to a desired location in any thickness and in any coating form using a known coating method, such as bead coating, slit coating, spray coating, swirl coating, or shot coating, and can be cured by heating to a predetermined temperature using, for example, a hot air circulation drying oven.

[0091] The adhesive composition of the present invention can be used as a binder (or adhesive, also called a "structural adhesive") for metal components and the like in a wide range of fields, including automobiles, ships, aviation, civil engineering, and construction. A member obtained by bonding metal members or the like is also called a structure, and in an embodiment of the present invention, an adhesive composition for producing a structure can be provided. In an embodiment of the present invention, a structure including a cured product of the adhesive composition can be provided. Examples of structures include structural parts in the automotive field, such as pillars, cross members, side members, side sills, roof rails, suspension members, various reinforcements, hoods, doors, and rear gates, as well as structural parts in the marine, aviation, civil engineering, and architectural fields. In an embodiment of the present invention, a structure comprising a cured product of the adhesive composition can be provided, including at least one structure selected from automobiles, ships, and aircraft. [Example]

[0092] EXAMPLES Hereinafter, the present invention will be specifically and in detail explained using examples and comparative examples, but these examples are merely one embodiment of the present invention, and the present invention is not limited to these examples in any way. In the examples, unless otherwise specified, parts by weight and percentages by weight are based on the parts not taking into account the solvent.

[0093] The components used in this example are listed below. (A) Epoxy resin (A1) Unmodified epoxy resin having a cyclic structure (a1-1) Bisphenol A epoxy resin (JER828 (trade name) manufactured by Mitsubishi Chemical Corporation, epoxy equivalent 189 g / eq., viscosity 13,000 mPa·s / 25°C) (A2) Other epoxy resins (a2-1) Epoxy resin having a bisphenol A structure and a polyoxyalkylene structure (ADEKA Corporation EP-4000 (trade name), epoxy equivalent 320 g / eq., viscosity 45,000 mPa·s / 25°C) (a2-2) Hexamethylene diglycidyl ether (ADEKA ED-503 (trade name)) (a2-3) Polyoxyalkylene diglycidyl ether (ADEKA ED-506 (trade name))

[0094] (AB3) Nitrile rubber (acrylonitrile-butadiene rubber: NBR) modified epoxy resin with functional groups that can react with epoxy groups (ab3-1) Epoxy resin modified with 40% by mass of carboxyl-terminated butadiene nitrile rubber (CTBN with an acrylonitrile content of 18% by mass) (Hypox 840 (trade name) manufactured by Huntsman) containing 40% by mass of carboxyl-terminated butadiene nitrile rubber. (ab3-2) Epoxy resin modified with 40% by mass of carboxyl-terminated butadiene nitrile rubber (CTBN with an acrylonitrile content of 26% by mass) (Hypox 1340 (trade name) manufactured by Huntsman), containing 40% by mass of carboxyl-terminated butadiene nitrile rubber.

[0095] (AB4) Urethane-modified epoxy resin modified with a urethane prepolymer having an active isocyanate group (ab4-1) Urethane-modified epoxy resin 1 A prepolymer was obtained by reacting 100 parts by mass of polypropylene triol having a molecular weight of 3,000 with 17.5 parts by mass of TDI (Sumidur T-80 / 20 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.). 30 parts by mass of this prepolymer was reacted with 70 parts by mass of bisphenol A-type epoxy resin having a hydroxyl value of 30 to obtain (ab4-1) urethane-modified epoxy resin 1. The resin contained 30% by mass of urethane resin.

[0096] (ab4-2) Urethane-modified epoxy resin 2 A prepolymer was obtained by reacting 100 parts by mass of polytetramethylenetriol having a molecular weight of 3,000 with 17.5 parts by mass of TDI (Sumidur T-80 / 20 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.). 30 parts by mass of this prepolymer was reacted with 70 parts by mass of bisphenol A-type epoxy resin having a hydroxyl value of 30 to obtain (ab4-2) urethane-modified epoxy resin 2. The resin contained 30% by mass of urethane resin.

[0097] (A+B1) Rubber particle dispersed epoxy resin (a1+b1-1) Rubber particle dispersed epoxy resin 1. Preparation of polybutadiene (core) rubber particles of (a1+b1-1) A pressure-resistant polymerization reactor was charged with 200 parts by weight of deionized water, 0.03 parts by weight of tripotassium phosphate, 0.25 parts by weight of potassium dihydrogen phosphate, 0.002 parts by weight of disodium ethylenediaminetetraacetate (EDTA), 0.001 parts by weight of ferrous sulfate heptahydrate (FE), and 1.55 parts by weight of sodium dodecylbenzenesulfonate (SDS). The mixture was stirred and thoroughly purged with nitrogen to remove oxygen. Then, 99.6 parts by weight of butadiene (BD) and 0.4 parts by weight of t-dodecyl mercaptan were added to the system, and the temperature was raised to 45°C. 0.03 parts by weight of paramenthane hydroperoxide (PHP) was added, followed by 0.10 parts by weight of sodium formaldehyde sulfoxylate (SFS). Polymerization was initiated by adding 0.025 parts by weight of PHP at 3, 5, and 7 hours after the start of polymerization. In addition, 0.0006 parts by mass of EDTA and 0.003 parts by mass of FE were added at 4, 6, and 8 hours after the start of polymerization. After 15 hours of polymerization, the remaining monomers were removed by degassing under reduced pressure to terminate the polymerization, yielding a polybutadiene rubber latex (R-1) composed primarily of polybutadiene rubber. The volume average particle diameter of the polybutadiene rubber particles contained in the obtained latex was 0.10 μm.

[0098] 2. Production of (a1+b1-1) rubber particles (core shell particles) A glass reactor equipped with a thermometer, stirrer, reflux condenser, nitrogen inlet, and monomer addition device was charged with 61 parts by weight of deionized water and 257 parts by weight of the above-mentioned latex (R-1) (85 parts by weight of solids). The mixture was stirred at 50°C for 30 minutes while purging with nitrogen. After adding 0.004 parts by weight of EDTA, 0.001 parts by weight of FE, and 0.2 parts by weight of SDS, 2 parts by weight of triallyl isocyanurate (TAIC) were added all at once. Subsequently, 0.07 parts by weight of cumene hydroperoxide (CHP) was added to initiate polymerization. After stirring for 1 hour, a mixture of 4 parts by weight of styrene (ST), 4 parts by weight of methyl methacrylate (MMA), 2.5 parts by weight of acrylonitrile (AN), 2.5 parts by weight of glycidyl methacrylate (GMA), and 0.08 parts by weight of cumene hydroperoxide (CHP) was continuously added over 2 hours to carry out graft polymerization. After the addition was completed, the mixture was stirred for another 2 hours to complete the reaction, yielding a latex (L-1) of core-shell particles (b1-1). The volume average particle diameter of the core-shell particles contained in the obtained latex was 0.15 μm.

[0099] 3. Preparation of epoxy resin (a1+b1-1) with dispersed rubber particles 132 g of methyl ethyl ketone (MEK) was introduced into a 1 L mixing tank at 25 °C, and 132 g of the aqueous latex (L-1) of core-shell particles (equivalent to 40 g of polymer particles) was added while stirring. After uniform mixing, 200 g of water was added at a feed rate of 80 g / min. After the feed was completed, stirring was promptly stopped, yielding a slurry liquid consisting of floating aggregates and an aqueous phase containing a portion of the organic solvent. Next, 360 g of the aqueous phase was discharged from the outlet at the bottom of the tank, leaving behind a portion of the aqueous phase. 90 g of MEK was added to the resulting aggregates and mixed uniformly to obtain a dispersion in which the core-shell particles (b1-1) were uniformly dispersed. 60 g of epoxy resin (a1-1: manufactured by Mitsubishi Chemical Corporation, JER828: unmodified bisphenol A epoxy resin with a cyclic structure), component (A), was mixed with this dispersion. MEK was removed from this mixture using a rotary evaporator. In this way, an epoxy resin (a1+b1-1) containing dispersed rubber particles was obtained. (a1+b1-1) contained 40 mass % of rubber particles. Table 1 shows the preparation of the above-mentioned rubber particle dispersed epoxy resin (a1+b1-1).

[0100] Preparation of epoxy resins (a1+b1-2) to (a1+b1-10) with dispersed rubber particles Epoxy resins (a+b1-2) to (a+b1-10) having dispersed rubber particles were produced using the same method as the above-mentioned epoxy resin (b1-1) having dispersed rubber particles, except for using the amounts of monomers listed in Table 1. The production of these resins is shown in Table 1. (a+b1-2) to (a1+b1-10) contain 40 mass% of rubber particles (b1-2) to (b1-10).

[0101] When producing rubber particles (core-shell particles) (b1-3) and (b1-6) to (b1-10) without an intermediate layer, the following steps were omitted: "2 parts by mass of triallyl isocyanurate (TAIC) was added all at once. Subsequently, 0.07 parts by mass of cumene hydroperoxide (CHP) was added to initiate polymerization. Stirring was continued for 1 hour, and then" to produce rubber particles (core-shell particles) (b1-3) and (b1-6) to (b1-10).

[0102] [Table 1]

[0103] (a+b1-11) Epoxy resin with dispersed rubber particles (Kane Ace MX-150 (trade name) manufactured by Kaneka Corporation), (a+b1-11) contains 40 mass % of rubber particles. (a+b1-12) Epoxy resin with dispersed rubber particles (Kane Ace MX-154 (trade name) manufactured by Kaneka Corporation), (a+b1-12) contains 40 mass % of rubber particles.

[0104] (B) Epoxy resin toughening agent (B2) Acrylic elastomer particles (b2-1) Polymethacrylate resin, average particle size approximately 80 μm (ZEFIAC F-351 (product name) manufactured by AICA Corporation) (B5) Block urethane prepolymer (b5-1) Block urethane prepolymer 1 A prepolymer was obtained by reacting 100 parts by mass of polytetramethylene polyol having a molecular weight of 3000 with 17.5 parts by mass of TDI (Sumidur T-80 / 20 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), and the active isocyanate was blocked by adding diallyl bisphenol in an amount equivalent to the isocyanate groups of the prepolymer. (b5-2) Block urethane prepolymer 2 ADEKA QR-9466 (product name)

[0105] (C) Diluent (c1) Aliphatic monoglycidyl ether (ADEKA ED-502 (trade name)) (c2) t-Butylphenol monoglycidyl ether (ADEKA ED-509 (trade name))

[0106] (D) Curing agent and curing accelerator (d1) Dicyandiamide (d2) Dimethylurea (Dyhard UR200 (trade name) manufactured by AlzChem) (d3) Modified aliphatic polyamine (EVONIC Ancamine 2014FG (trade name)) (d4) 2,4-Diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine isocyanuric acid adduct (2MAOK-PW (trade name) manufactured by Shikoku Chemical Industries, Ltd.) (d5) Dodecanediohydrazide (DDH (trade name) manufactured by Otsuka Chemical Co., Ltd.)

[0107] (E) Filler (e1) Calcium carbonate (e2) Carbon black / fumed silica (F) Other additives (f2) Calcium oxide

[0108] These components were blended in the parts by mass shown in Tables 2 to 5 to produce adhesive compositions of Examples 1 to 31 and Comparative Examples 1 to 4. Each of the above adhesive compositions was subjected to a hot shear adhesion test (120°C, 100°C), a peel adhesion test (23°C), and a low-temperature impact test (-30°C) using the following methods and evaluated. The results are shown in Tables 2 to 5.

[0109] Hot shear adhesion test (120℃, 100℃) A hot shear adhesion test was conducted in accordance with the test preparation method in JASO M353 (1998) Section 16. For each of the one-component thermosetting adhesive compositions described above, a 1.6 mm thick SPCC steel plate was used as the adherend, and NOX-RUST320 manufactured by Parkerizing Japan Co., Ltd. was used as the rust preventative oil. The curing conditions were 170°C and 20 minutes. The test was conducted in environments of 100°C and 120°C. The test speed was 50 mm / min. The evaluation criteria are as follows: 〇: 22MPa or more 〇-: 18MPa or more, less than 22MPa △+: 15 MPa or more, less than 18 MPa △: 10 MPa or more, less than 15 MPa ×: Less than 10 MPa

[0110] T-type peel adhesion test (23°C) A T-type peel adhesion test was conducted in accordance with the test preparation method in JASO M353 (1998) Section 16. For each of the one-component thermosetting adhesive compositions described above, a 0.8 mm thick SPCC steel plate was used as the adherend, and NOX-RUST320 manufactured by Parkerizing Japan Co., Ltd. was used as the rust preventative oil. The curing conditions were 170°C and 20 minutes. The test environment was 23°C. The test speed was 200 mm / min. The evaluation criteria are as follows: ◎:220N / 25mm or more 〇: 180N / 25mm or more, less than 220N / 25mm 〇-: 140N / 25mm or more, less than 180N / 25mm △: 100N / 25mm or more, less than 140N / 25mm ×: Less than 100N / 25mm

[0111] Low temperature impact resistance (-30℃) Using SPCC steel plates, test specimens are prepared in accordance with the wedge impact test of JIS K6865. Measurements are carried out using a high-speed tensile testing machine. The impact strength is calculated by dividing the average strength within the range of 25-90% of the total displacement during the test by the width of the test specimen. The curing conditions are 170°C, 20 minutes, and the test speed is 2 m / s. The evaluation criteria are as follows: ◎:30N or more 〇+: 26N or more, less than 30N 〇: 22N or more, less than 26N 〇-: 20N or more, less than 22N △: 15N or more, less than 20N ×: Less than 15N

[0112] [Table 2]

[0113] [Table 3]

[0114] [Table 4]

[0115] [Table 5]

[0116] The adhesive compositions of Examples 1 to 31 exhibit a certain level of performance in the hot shear adhesion test (120°C, 100°C), peel adhesion test (23°C), and low-temperature impact test (-30°C), and overall exhibit sufficient performance. On the other hand, the adhesive compositions of Comparative Examples 1 to 4 did not exhibit a certain level of performance in any one of the hot shear adhesion test (120°C, 100°C), peel adhesion test (23°C), and low-temperature impact test (-30°C), and were generally insufficient. [Industrial Applicability]

[0117] The adhesive composition of an embodiment of the present invention provides an adhesive composition that has improved hot (hot) adhesion, cold (low temperature) impact resistance, and toughness while maintaining various properties that have traditionally been desired (e.g., workability, durability, storage stability, etc.). Thus, the adhesive composition of an embodiment of the present invention can be suitably used in manufacturing automobiles, and can be suitably used as a structural adhesive.

Claims

1. An adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains at least (A1) an unmodified epoxy resin having a cyclic structure, the epoxy resin toughener (B) contains at least two types of epoxy resin tougheners, The epoxy resin toughener (B) contains (B1) rubber particles having a core-shell structure having a core of a diene polymer (including a copolymer), Adhesive composition.

2. The composition according to claim 1, wherein the shell of the rubber particles (B1) having a core-shell structure is a vinyl polymer.

3. The composition according to claim 2, wherein the vinyl polymer of the shell of the core-shell rubber particles (B1) is a copolymer of monomers containing at least two or more selected from methyl methacrylate, glycidyl methacrylate, styrene, acrylonitrile, methacrylic acid, and glycidyl acrylate.

4. The composition according to claim 1, wherein the mass ratio of the core to the shell (shell / core) of the core-shell structured rubber particles (B1) is 5 parts by mass or more and less than 60 parts by mass of the shell per 100 parts by mass of the core.

5. 2. The composition according to claim 1, wherein the vinyl polymer of the shell of the core-shell rubber particles (B1) contains at least a portion based on glycidyl methacrylate or glycidyl acrylate, and the epoxy groups contained in the core-shell rubber particles (B1) are contained in an amount of 0.2 parts by mass or more and less than 8 parts by mass per 100 parts by mass of the core-shell rubber particles (B1).

6. It is possible to further include a reactive diluent (C), The composition according to claim 1, wherein the reactive diluent (C) is contained in an amount of 0 parts by mass (not contained), or less than 15 parts by mass, based on 100 parts by mass of the total of (A), (B), (C), and (D).

7. The content of the core-shell rubber particles (B1) is The composition according to claim 6, wherein the total amount of (A), (B), (C), and (D) is 1 part by mass or more and less than 40 parts by mass, relative to 100 parts by mass of the total amount of (A), (B), (C), and (D).

8. 2. The composition according to claim 1, wherein the epoxy resin (A) comprises a flexible epoxy resin having a bisphenol skeleton to which polyalkylene oxide is added and further to which epichlorohydrin is added.

9. 7. The composition according to claim 6, wherein the total number of repeating polyoxyalkylene units in said flexible epoxy resin is 1 or more and 8 or less.

10. The composition according to claim 1, wherein the amine-based latent curing agent (D) comprises at least one selected from the group consisting of a dihydrazide compound, an imidazole compound, and an aliphatic polyamine compound.

11. The composition according to claim 6, wherein the epoxy resin toughening agent (B) comprises a blocked urethane prepolymer (B5) which is a reaction product of a polyalkylene polyol, a polyisocyanate, and a blocking agent.

12. The composition according to claim 11, wherein the content of the block urethane prepolymer (B5) is in any of the following ranges: (i) 1 part by mass or more and less than 35 parts by mass per 100 parts by mass of (B1); (ii) The amount is 0.1 parts by mass or more and less than 6 parts by mass, with the total of (A), (B), and (D) being 100 parts by mass.

13. The composition according to claim 6, wherein the epoxy resin (A) further contains an NBR-modified epoxy resin (AB3) modified with an acrylonitrile-butadiene rubber (B3) having a functional group reactive with an epoxy group, which is the epoxy resin toughening agent (B).

14. The composition according to claim 13, wherein the content of the acrylonitrile-butadiene rubber (B3) having a functional group reactive with an epoxy group is in any of the following ranges: (iii) 1 part by mass or more and less than 30 parts by mass relative to 100 parts by mass of (B1); (iv) The amount is 0.1 parts by mass or more and less than 5 parts by mass, with the total of (A), (B), (C), and (D) being 100 parts by mass.

15. The composition according to claim 13, wherein the acrylonitrile content of the acrylonitrile-butadiene rubber (B3) having a functional group reactive with an epoxy group is 1% by mass or more and less than 25% by mass.

16. The composition according to claim 6, wherein the epoxy resin (A) further contains a urethane-modified epoxy resin (AB4) modified with a urethane prepolymer (B4) having an active isocyanate group, which is the epoxy resin toughener (B).

17. The composition according to claim 16, wherein the content of the urethane prepolymer (B4) having an active isocyanate group is in any of the following ranges: (v) 1 part by mass or more and less than 35 parts by mass per 100 parts by mass of (B1); (vi) The amount is 0.1 parts by mass or more and less than 5 parts by mass, with the total of (A), (B), (C), and (D) being 100 parts by mass.

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