One-component thermosetting adhesive composition

Abstract

To provide an adhesive composition which enhances water resistance and moisture resistance while retaining various conventionally demanded properties (for example, impact resistance and superior adhesion strength to metallic substrates).SOLUTION: A one-component thermosetting adhesive composition comprises an epoxy resin (A), an epoxy resin toughening agent (B), a reactive diluent (C), a latent amine curing agent (D), and a filler (E), the epoxy resin (A) including (A1) an unmodified bisphenol-type epoxy resin, and the epoxy resin toughening agent (B) including (B1) a low-polarity elastomer.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 weld bond techniques, which combine spot welding with 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 various durability properties, such as impact resistance, high adhesive strength to metal substrates, and good coatability.

[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, conventional adhesives do not have sufficient resistance to moisture and humidity (water resistance and moisture resistance), and therefore are limited in their use in locations that are frequently exposed to water, such as the underside of a vehicle. Therefore, there is a demand for structural adhesives that have improved water resistance and moisture resistance compared to conventional adhesives while maintaining the various properties that have traditionally been desired (e.g., impact resistance, high adhesive strength to metal substrates, etc.). [Means for solving the problem]

[0007] Conventional structural adhesives often contain epoxy resins with polyoxyalkylene skeletons to compensate for the hard and brittle properties of the main component, bisphenol-type epoxy resin, and to reduce viscosity. However, because these resins can be hydrophilic, they are thought to be prone to reducing water resistance and moisture resistance.

[0008] As a result of extensive research, the present inventors have found that the above problems can be solved by using a low-polarity elastomer and adding a reactive diluent that can reduce viscosity.

[0009] This specification includes the following forms. 1. A one-component thermosetting adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), a reactive diluent (C), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains (A1) an unmodified bisphenol-type epoxy resin, The epoxy resin toughening agent (B) contains (B1) a low-polarity elastomer. A one-component thermosetting adhesive composition. 2. The one-component thermosetting adhesive composition according to 1 above, wherein the content of the unmodified bisphenol-type epoxy resin (A1) is 30 parts by mass or more and 87 parts by mass or less, 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). 3. The one-component thermosetting adhesive composition according to 1 or 2 above, wherein the low-polarity elastomer (B1) comprises at least one selected from the group consisting of butadiene polymers, isoprene polymers, and acrylonitrile-butadiene copolymers having an acrylonitrile content of less than 8%. 4. The one-component thermosetting adhesive composition according to any one of 1 to 3 above, wherein the low-polarity elastomer (B1) is in the form of particles having a core-shell structure comprising a core and a shell, the shell comprising an acrylic polymer, and the core comprising the low-polarity elastomer (B1). 5. The one-component thermosetting adhesive composition according to any one of 1 to 4 above, wherein the low-polarity elastomer (B1) may contain at least one group selected from an acid anhydride group, a carboxy group, an amino group, an imino group, and an epoxy group. 6. The one-component thermosetting adhesive composition according to 5 above, wherein the low-polarity elastomer (B1) may be a part contained in a modified epoxy resin that has been pre-reacted with an excess of the epoxy resin (A). 7. The one-component thermosetting adhesive composition according to any one of 1 to 6, comprising 40 to 85 parts by mass of the unmodified bisphenol-type epoxy resin (A1) and 2 to 25 parts by mass of the low-polarity elastomer (B1), per 100 parts by mass of the epoxy resin (A), the epoxy resin toughener (B), the reactive diluent (C), and the amine-based latent curing agent (D) combined. 8. The one-component thermosetting adhesive composition according to any one of 1 to 7 above, wherein the reactive diluent (C) comprises a reactive diluent having less than 15 carbon atoms excluding the glycidyl group. 9. The one-component thermosetting adhesive composition according to any one of 1 to 8 above, wherein the reactive diluent (C) includes a reactive diluent having an aromatic ring. 10. The one-component thermosetting adhesive composition according to any one of 1 to 9 above, wherein the latent curing agent (D) comprises a latent curing agent containing at least an imidazole having a hydroxyl group. 11. The one-component thermosetting adhesive composition according to any one of 1 to 10 above, wherein none of the epoxy resin (A), the epoxy resin toughener (B), and the reactive diluent (C) contains a polyoxyalkylene structure having four or more consecutive oxyalkylene repeating units, or wherein the content of compounds corresponding to (A) to (D) containing a polyoxyalkylene structure having four or more consecutive oxyalkylene groups is 5 parts by mass or less, 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). 12. The one-component thermosetting adhesive composition according to any one of 1 to 11 above, further comprising an additive (F), wherein the additive (F) comprises a silane coupling agent (F1) having an epoxy group. [Effects of the Invention]

[0010] The one-component thermosetting adhesive composition according to an embodiment of the present invention can provide an epoxy resin composition that has improved water resistance and moisture resistance compared to conventional compositions while maintaining various properties that have traditionally been desired (e.g., impact resistance, high adhesive strength to metal substrates, etc.). Therefore, the one-component thermosetting adhesive composition according to 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 one-component thermosetting adhesive composition according to an embodiment of the present invention comprises: A one-component thermosetting adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), a reactive diluent (C), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains (A1) an unmodified bisphenol-type epoxy resin, The epoxy resin toughening agent (B) includes (B1) a low-polarity elastomer.

[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, and is generally called an epoxy resin. There are no particular limitations on the epoxy resin (A) as long as it can provide the one-component thermosetting adhesive composition that is the objective of the present invention. 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] The (A) epoxy resin preferably contains (A1) an unmodified bisphenol-type epoxy resin. (A1) Unmodified bisphenol epoxy resin is an epoxy resin having a bisphenol structure, and the epoxy resin having a bisphenol structure is not particularly limited as long as it is not modified and can provide the one-component thermosetting adhesive composition of the present invention. (A1) Examples of unmodified bisphenol-type epoxy resins include diglycidyl ethers of bisphenol A, bisphenol F, brominated bisphenol A, and bisphenol AD.

[0014] The viscosity of the unmodified bisphenol epoxy resin (A1) at 25°C is preferably 1500 mPa·s or more, more preferably 2000 to 25000 mPa·s, even more preferably 2500 to 20000 mPa·s, and even more preferably 3000 to 15000 mPa·s. The (A1) unmodified bisphenol epoxy resin preferably has an epoxy equivalent of 150 to 800 g / eq., more preferably 160 to 500 g / eq., even more preferably 165 to 250 g / eq., and even more preferably 170 to 200 g / eq. When the (A1) unmodified bisphenol epoxy resin has an epoxy equivalent of 150 to 800 g / eq., it has better workability. As the (A1) unmodified bisphenol epoxy resin, commercially available products can be used, such as "jER828 (trade name)," "jER1001 (trade name)," and "jER807 (trade name)" manufactured by Mitsubishi Chemical Corporation. In this specification, the viscosity of the (A1) unmodified bisphenol epoxy resin refers to a value measured using a B-type viscometer in accordance with JIS K7117-1.

[0015] The unmodified bisphenol epoxy resin (A1) is preferably contained in an amount of 30 to 87 parts by mass, more preferably 40 to 85 parts by mass, more preferably 45 to 80 parts by mass, even more preferably 50 to 75 parts by mass, and particularly preferably 55 to 70 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 curable adhesive composition according to an embodiment of the present invention contains 30 to 87 parts by mass of the unmodified bisphenol epoxy resin (A1) 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), the curable adhesive composition according to an embodiment of the present invention can further improve its water resistance and moisture resistance while better maintaining various properties that have traditionally been desired (e.g., impact resistance, high adhesive strength to metal substrates, etc.).

[0016] The epoxy resin (A) may contain an epoxy resin (A2) other than the unmodified bisphenol-type epoxy resin (A1). Examples of such epoxy resins (A2) other than (A1) include naphthalene-type epoxy resins, glycidylamine-type epoxy resins, biphenyl-type epoxy resins, epoxy resins having a polyoxyalkylene structure, epoxy resins having a polyoxyalkylene structure and a bisphenol structure, and dimer acid- or phthalic acid-based epoxy resins. Further examples include epoxy resin moieties such as elastomer-modified epoxy resins that can function as epoxy resin tougheners, as described below. The epoxy resin (A2) other than (A1) can include an epoxy resin having a polyoxyalkylene structure with less than four consecutive oxyalkylene repeating units. The content of the epoxy resin (A2) having a polyoxyalkylene structure with four or more consecutive oxyalkylene repeating units is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the total of components (A) to (D).

[0017] The epoxy resin (A) is preferably contained in an amount of 40 to 92 parts by mass, more preferably 50 to 90 parts by mass, even more preferably 60 to 88 parts by mass, and even more preferably 70 to 85 parts by mass, based on 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 (A) is contained in an amount of 40 to 92 parts by mass per 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), the composition has better curability, strength, and heat resistance. The epoxy resin (A) is preferably contained in an amount of 30 to 85 parts by mass, more preferably 35 to 75 parts by mass, even more preferably 40 to 65 parts by mass, and even more preferably 45 to 60 parts by mass per 100 parts by mass of the curable adhesive composition. When the epoxy resin (A) is contained in an amount of 30 to 85 parts by mass per 100 parts by mass of the curable adhesive composition, the curability, strength, and heat resistance are more excellent.

[0018] In this specification, the epoxy resin toughening agent (B) is a polymeric material having elastomeric properties (rubber elasticity), and is not particularly limited as long as it can toughen the cured epoxy resin (further improving peel strength and impact resistance) and improve toughness, and can obtain the composition intended by the present invention. As the epoxy resin toughening agent (B), an elastomer that can be used for the purpose of toughening epoxy resins can be used, and examples thereof include polyurethane prepolymers having active isocyanates, butadiene-based polymers having functional groups (including copolymers with acrylonitrile, styrene, etc.), and blocked isocyanates, and it is preferable that the elastomer has the form of core-shell rubber particles. The epoxy resin toughening agent may be contained in the composition alone or in combination of two or more kinds, may be mixed and / or dispersed in the composition, or may be pre-reacted with the epoxy resin to become part of the epoxy resin.

[0019] The form of the epoxy resin toughener (B) is not particularly limited as long as the composition aimed at by the present invention can be obtained. One form of the epoxy resin toughening agent (B) may be, for example, particulate. The epoxy resin toughening agent (B) may be contained in particles having a core-shell structure having a core and a shell, or may be contained in the core of such particles. The particle shape may be spherical, and its diameter may be, for example, 50 to 3000 nm, 150 to 1000 nm, 200 to 700 nm, or 250 to 550 nm. The core of the core-shell structure is composed of an epoxy resin toughening agent, which may be an elastomer such as butadiene polymer, isoprene polymer, acrylonitrile butadiene copolymer, styrene-butadiene copolymer, butyl acrylate, polydimethylsiloxane, or the like. The shell of the core-shell structure can be appropriately selected in consideration of compatibility with the epoxy resin, and may be, for example, an acrylic polymer, a vinyl polymer, or a copolymer thereof. The epoxy resin toughening agent (B) contained in the particles can be dispersed in the epoxy resin (A) to prepare a masterbatch. Commercially available masterbatches are available, such as Kane Ace MX-150 (trade name) and Kane Ace MX-257 (trade name) manufactured by Kaneka Corporation.

[0020] The epoxy resin toughening agent (B) may contain at least one polar group selected from, for example, an acid anhydride group, a carboxy group, an amino group, an imino group, and an epoxy group.

[0021] Another form of the epoxy resin toughener (B) may be a urethane prepolymer in which an active isocyanate is blocked with a thermal-release blocking agent. The urethane prepolymer may be a blocked isocyanate in which a reaction product of a polyol having elastomeric properties and a polyisocyanate is blocked with a blocking agent. Examples of polyols having elastomeric properties include polyether polyols, polyester polyols, polybutadiene polyols, and polymerized products thereof. Examples of polyisocyanates include tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

[0022] The epoxy resin toughener (B) may be present, for example, as a part of the epoxy resin (A). Such an elastomer may be, for example, a part contained in an elastomer-modified epoxy resin obtained by preliminarily reacting an excess of the epoxy resin with a reactive group contained in the elastomer. Such an elastomer-modified epoxy resin contains a part corresponding to the epoxy resin (A) and a part corresponding to the epoxy resin toughener (B). Examples of the elastomer-modified epoxy resin (AB) having an elastomer portion and an epoxy resin portion include a butadiene-modified epoxy resin obtained by pre-reacting a carboxyl group with an epoxy group, an acrylonitrile-butadiene-modified epoxy resin, and a urethane-modified epoxy resin obtained by pre-reacting a urethane prepolymer obtained by pre-reacting a polyol with a polyisocyanate with a hydroxyl group of an epoxy resin.

[0023] The epoxy resin toughening agent (B) includes a low polarity elastomer (B1). The low-polarity elastomer (B1) is a polymeric material having low polarity and elastomeric properties, and is capable of toughening a cured epoxy resin material and improving its toughness, and is not particularly limited as long as the composition intended by the present invention can be obtained. Examples of the low-polarity elastomer (B1) include butadiene polymers, polyisoprene polymers, and elastomeric resins with a low content of polar groups (specifically, acrylonitrile-butadiene copolymers with an acrylonitrile content of less than 8% by mass, and styrene-butadiene copolymers with a styrene content of less than 10% by mass).

[0024] The epoxy resin toughening agent (B) preferably has the form of particles having a core-shell structure containing a core and a shell, the shell containing an acrylic polymer, and the core containing the low-polarity elastomer (B1).

[0025] The low-polarity elastomer (B1) may have at least one polar group selected from, for example, an acid anhydride group, a carboxy group, an amino group, an imino group, and an epoxy group.

[0026] The epoxy resin toughening agent (B) may contain an elastomer (B2) other than the low-polarity elastomer (B1). The elastomer (B2) is a polymeric material, other than (B1), having elastomeric properties (rubber elasticity), capable of toughening the cured product of the epoxy resin and improving its toughness, and is not particularly limited as long as the composition intended by the present invention can be obtained.

[0027] Examples of the elastomer (B2) include urethane elastomer, nitrile butadiene rubber, and acrylic elastomer. The elastomer (B2) may be present as part of the epoxy resin (A), which can be described as an elastomer-modified epoxy resin (AB2). As the elastomer-modified epoxy resin (AB2), a commercially available product can be used. For example, an example of a urethane-modified epoxy resin using a urethane elastomer is EPU-6 (trade name) manufactured by ADEKA Corporation; an example of an NBR (including CTBN-modified) modified epoxy resin obtained by modifying an epoxy resin with a nitrile butadiene acrylic acid copolymer or a carboxy-terminated nitrile butadiene copolymer is EPON58005 (trade name) manufactured by HEXION Corporation; and an example of an acrylic rubber is ZEFIAC F-351 (trade name) manufactured by AICA Kogyo Co., Ltd.

[0028] The elastomer-modified epoxy resin (AB2) can also be produced using known methods. For example, a urethane-modified epoxy resin can be obtained by reacting 20 parts by mass of a triol having a molecular weight of 3,000 with 3.5 parts by mass of TDI (Sumidur T-80 / 20 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.) to obtain a prepolymer, and then reacting 30 parts by mass of this prepolymer with 70 parts by mass of a bisphenol A-type epoxy resin having a hydroxyl value of 30. For example, a 15% by mass CTBN (AN (acrylonitrile) > 8% by mass) modified epoxy resin can be obtained by reacting 15 parts by mass of CTBN (carboxyl-terminated butadiene nitrile rubber, manufactured by Huntsman under the trade name Hypro1300x8) with 85 parts by mass of a bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation under the trade name jER828).

[0029] The epoxy resin toughener (B) is preferably contained in an amount of 3 to 40 parts by mass, more preferably 5 to 35 parts by mass, even more preferably 7 to 30 parts by mass, and even more preferably 10 to 20 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 3 to 40 parts by mass per 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), the toughening and workability (ensuring low viscosity / dischargeability) are superior. The epoxy resin toughener (B) is preferably contained in an amount of 2 to 30 parts by mass, more preferably 4 to 25 parts by mass, even more preferably 5 to 20 parts by mass, and even more preferably 7 to 15 parts by mass per 100 parts by mass of the curable adhesive composition. When the curable adhesive composition contains 2 to 30 parts by mass of the epoxy resin toughener (B) per 100 parts by mass of the curable adhesive composition, the toughening and workability (ensuring low viscosity / dischargeability) are superior.

[0030] The one-component thermosetting adhesive composition according to an embodiment of the present invention comprises, based on 100 parts by mass of the total of (A) epoxy resin, (B) epoxy resin toughener, (C) reactive diluent, and (D) amine-based latent curing agent, It is preferable that the composition contains (A1) an unmodified bisphenol-type epoxy resin in an amount of 40 parts by mass or more and 85 parts by mass or less, and (B1) a low-polarity elastomer in an amount of 2 parts by mass or more and 25 parts by mass or less, It is more preferable that the composition contains (A1) an unmodified bisphenol-type epoxy resin in an amount of 45 parts by mass or more and 80 parts by mass or less, and (B1) a low-polarity elastomer in an amount of 3 parts by mass or more and 20 parts by mass or less, It is even more preferable that the composition contains (A1) 50 parts by mass or more and 75 parts by mass or less of an unmodified bisphenol-type epoxy resin and (B1) 5 parts by mass or more and 14 parts by mass or less of a low-polarity elastomer.

[0031] A one-component thermosetting adhesive composition according to an embodiment of the present invention comprises an epoxy resin (A), an epoxy resin toughening agent (B), a reactive diluent (C), an amine-based latent curing agent (D), and a filler (E), and the epoxy resin toughening agent (B) comprises a low-polarity elastomer (B1). In order to improve the water resistance of the adhesive strength of the one-component thermosetting adhesive composition targeted by the present invention, it is preferable to limit the content of components containing a polyoxyalkylene structure, since these components are hydrophilic. For example, the epoxy resin having a polyoxyalkylene structure with less than four consecutive oxyalkylene repeating units can be contained in an amount of 15 parts by mass or less per 100 parts by mass of the total of components (A) to (D). On the other hand, in the case of an epoxy resin having a polyoxyalkylene structure with four or more consecutive oxyalkylene repeating units, the amount is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of the total of components (A) to (D).

[0032] It is preferable that none of the epoxy resin (A), the epoxy resin toughener (B), and the reactive diluent (C) contains a polyoxyalkylene structure having four or more consecutive oxyalkylene groups, or that the content of the compounds corresponding to (A) to (D) containing a polyoxyalkylene structure having four or more consecutive oxyalkylene groups is 5 parts by mass or less, 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).

[0033] In this specification, the reactive diluent (C) refers to a diluent that has one epoxy group and reacts with the epoxy resin (A) via that epoxy group, but is also capable of reducing the viscosity. There are no particular limitations on the reactive diluent (C) as long as it is possible to obtain the one-component thermosetting adhesive composition that is the objective of the present invention. The viscosity (25°C) of the reactive diluent (C) may be 1 to 100 mPa·s, 5 to 80 mPa·s, 10 to 60 mPa·s, 15 to 50 mPa·s, or 20 to 40 mPa·s. The reactive diluent (C) is a low molecular weight compound, and its molecular weight may be 120-550, 150-450, 200-400, 220-350, or 250-320. In this specification, the viscosity of the reactive diluent (C) refers to a value measured using a B-type viscometer in accordance with JIS K7117-1.

[0034] Examples of the reactive diluent (C) include a compound having one glycidyloxy group, a compound having one glycidylamino group, and a compound having one glycidyloxycarbonyl (glycidyl ester) group. The reactive diluent (C) preferably comprises a compound having one glycidyl group.

[0035] In a compound having one glycidyl group, the number of carbon atoms excluding the glycidyl group may be 4 or more, 5 or more, 6 or more, or 7 or more. In a compound having one glycidyl group, the number of carbon atoms excluding the glycidyl group may be 26 or less, 22 or less, 18 or less, 15 or less, less than 15, 14 or less, or 10 or less.

[0036] The portion of the compound having one glycidyl group other than the glycidyl group contains at least one selected from alkyl, cycloalkyl, and aryl, and it may have at least one substituent selected from alkyl, cycloalkyl, and aryl. Examples of compounds having one glycidyl group include methylphenyl glycidyl ether (having 7 carbon atoms excluding the glycidyl group), aliphatic phenyl glycidyl ether (having approximately 21 carbon atoms excluding the glycidyl group), and aliphatic monoglycidyl ether (having 12 to 13 carbon atoms excluding the glycidyl group). As the compound having one glycidyl group, a commercially available product can be used. For example, ADEKA ED-529 (trade name), Cardolite LITE2513HP (trade name), ADEKA ED-502 (trade name), etc. can be mentioned.

[0037] The reactive diluent (C) preferably includes a reactive diluent in which the number of carbon atoms, excluding the glycidyl group, may be 26 or less, 22 or less, 18 or less, 15 or less, less than 15, 14 or less, or 10 or less. The reactive diluent (C) preferably contains a reactive diluent having an aromatic ring.

[0038] The reactive diluent (C) is preferably contained in an amount of 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, even more preferably 3 to 8 parts by mass, and even more preferably 4 to 6 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 total amount of the epoxy resin (A), the epoxy resin toughener (B), the reactive diluent (C), and the amine-based latent curing agent (D) is 100 parts by mass, and the reactive diluent (C) is 1 to 15 parts by mass, the viscosity is lowered and the heat resistance is superior. The reactive diluent (C) is preferably contained in an amount of 0.5 to 10 parts by mass, more preferably 1 to 8 parts by mass, even more preferably 2 to 6 parts by mass, and even more preferably 3 to 5 parts by mass per 100 parts by mass of the curable adhesive composition. When the curable adhesive composition contains 0.5 to 10 parts by mass of the reactive diluent (C) per 100 parts by mass of the curable adhesive composition, the viscosity is lowered and heat resistance is superior.

[0039] The one-component thermosetting 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, which does not have a curing action at room temperature but functions as a curing agent when heated to a certain temperature (for example, 165°C, preferably 150°C), and is not particularly limited as long as the composition targeted by the present invention can be obtained.

[0040] 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'-methylimidazolium(1'))-ethyl-o-triazine; Benzoguanamine; N,N-dialkylureas such as N,N-dimethyl-N'-(3,4-dichlorophenyl)urea, Dialkyl urea compounds such as N,N'-dialkyl urea compounds; N,N'-dialkylthiourea compounds; Polyamines such as diaminodiphenylmethane, diaminobiphenyl, diaminophenol, phenylenediamine, tolylenediamine, dodecanediamine, decanediamine, octanediamine, tetradecanediamine, hexadecanediamine, polyoxypropylenediamine, and hydrazide-based polyamines; Examples include guanidine derivatives such as cyanoguanidine.

[0041] Commercially available products can be used as the amine-based latent curing agent (D), such as CG-NA (trade name) manufactured by Air Products, EH-4070s (trade name) manufactured by ADEKA, ADH (adipic acid dihydrazide, trade name) manufactured by Otsuka Chemical, EH-3731s (trade name) manufactured by ADEKA, and Dyhard UR200 (a urea compound, trade name) manufactured by AlzChem.

[0042] The amine-based latent curing agent (D) preferably contains a latent curing agent containing at least an imidazole having a hydroxyl group. Examples of latent curing agents containing at least an imidazole having a hydroxyl group include 2-phenyl-methyl-5-hydroxymethylimidazole and 2-phenyl-4,5-dihydroxymethylimidazole. As the latent curing agent containing at least an imidazole having a hydroxyl group, commercially available products can be used, such as 2P4MHZ-PW (trade name) and 2PHZ-PW (trade name) manufactured by Shikoku Chemicals Corporation.

[0043] The amine-based latent curing agent (D) is preferably contained in an amount of 1 to 25 parts by mass, more preferably 2 to 20 parts by mass, even more preferably 3 to 15 parts by mass, and even more preferably 5 to 12 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 total amount of the epoxy resin (A), the epoxy resin toughener (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 1 to 25 parts by mass, the curability and storage stability are more excellent. The amine-based latent curing agent (D) is preferably contained in an amount of 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, even more preferably 3 to 12 parts by mass, and even more preferably 4 to 10 parts by mass per 100 parts by mass of the curable adhesive composition. When the amine-based latent curing agent (D) is contained in an amount of 1 to 20 parts by mass per 100 parts by mass of the curable adhesive composition, the curability and storage stability are more excellent.

[0044] The one-component thermosetting adhesive composition according to an embodiment of the present invention may further contain a filler (E). In this specification, a filler is a compound that increases the amount of the one-component thermosetting adhesive composition of an embodiment of the present invention and can impart a certain degree of strength to the film formed from the one-component thermosetting adhesive composition, and in some cases can contribute to viscosity adjustment or weight reduction. There are no particular limitations on the filler as long as the one-component thermosetting adhesive composition intended by the present invention can be obtained.

[0045] 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, water 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, various whiskers, and other fibrous fillers; 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.

[0046] The filler (E) is preferably contained in an amount of 10 to 250 parts by mass, more preferably 20 to 180 parts by mass, even more preferably 40 to 120 parts by mass, and even more preferably 60 to 100 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 filler (E) is contained in an amount of 10 to 250 parts by mass per 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), the workability (dripping and dischargeability after application) is superior. The content of the filler (E) per 100 parts by mass of the cured adhesive composition is preferably 5 to 80 parts by mass, more preferably 10 to 70 parts by mass, even more preferably 15 to 60 parts by mass, and even more preferably 20 to 50 parts by mass. When the curable adhesive composition contains 5 to 80 parts by mass of filler (E) per 100 parts by mass of the curable adhesive composition, the workability (dripping and dischargeability after application) is superior.

[0047] The one-component thermosetting 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.

[0048] 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.

[0049] In an embodiment of the present invention, the diluent is not particularly limited as long as it can impart fluidity to the one-component thermosetting adhesive composition of an embodiment of the present invention and, with the exception of the reactive diluent (C) described above, can provide the one-component thermosetting adhesive composition intended by the present invention. Examples of diluents include hydrocarbon solvents such as paraffinic solvents, isoparaffinic solvents, naphthenic solvents, and aromatic solvents.

[0050] 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, bismuth 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 one-component thermosetting adhesive composition intended by the present invention can be obtained. The additive (F) preferably contains a silane or titanium coupling agent, and more preferably contains a silane coupling agent (F1) having an epoxy group.

[0051] The one-component thermosetting adhesive composition according to an embodiment 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 epoxy resin 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.

[0052] The one-component thermosetting adhesive composition of the present invention is preferably cured at 130°C for 15 minutes to provide a cured product that exhibits excellent initial adhesive strength, water-resistant adhesive strength (at 70°C for 18 days), humidity-resistant adhesive strength (at 70°C for 18 days at 95% RH), water-resistant adhesion (after immersion at 40°C), and a cross-cut peel test. Detailed evaluation methods are described in the Examples.

[0053] The initial adhesive strength (peel strength) of the cured product of the one-component thermosetting adhesive composition according to an embodiment of the present invention is preferably 65 to 300 N / 25 mm, more preferably 80 to 300 N / 25 mm, even more preferably 100 to 300 N / 25 mm, and particularly preferably 110 to 300 N / 25 mm.

[0054] The water-resistant adhesive strength (70°C for 18 days) of a cured product of the one-component thermosetting adhesive composition according to an embodiment of the present invention is preferably 65 to 300 N / 25 mm, more preferably 80 to 300 N / 25 mm, even more preferably 100 to 300 N / 25 mm, and particularly preferably 110 to 300 N / 25 mm.

[0055] The moisture-resistant (70°C, 95% RH, 18 days) adhesive strength of a cured product of the one-component thermosetting adhesive composition according to an embodiment of the present invention is preferably 65 to 300 N / 25 mm, more preferably 80 to 300 N / 25 mm, even more preferably 100 to 300 N / 25 mm, and particularly preferably 110 to 300 N / 25 mm.

[0056] In a cross-cut peel test for water-resistant adhesion (after immersion at 40°C) of a cured product of a one-component thermosetting adhesive composition according to an embodiment of the present invention, it is preferable that no peeling occurs at least on day 1. Furthermore, it is preferable that there is little peeling even on day 10, and it is most preferable that no peeling occurs at all.

[0057] The one-component thermosetting 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 circulating drying oven.

[0058] The one-component thermosetting 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 component obtained by bonding metal components or the like is also called a structure, and in an embodiment of the present invention, a one-component thermosetting adhesive composition for producing a structure can be provided. In an embodiment of the present invention, a structure can be provided that includes a cured product of the one-component thermosetting adhesive composition. 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 one-component thermosetting adhesive composition can be provided, including at least one structure selected from automobiles, ships, and aircraft. [Example]

[0059] 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.

[0060] The components used in this example are listed below. (A) Epoxy resin (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) (a2-1) Epoxy resin having a bisphenol A structure and a polyoxyalkylene structure (EP-4000 (trade name) manufactured by ADEKA Corporation, in the following chemical formula, m+n=5.2 (the number of oxyalkylene groups (repeating units) is 5.2), it contains 47% by mass of polyalkylene structures (value calculated from the chemical structure and epoxy equivalent), has an epoxy equivalent of 320 g / eq., and a viscosity of 45,000 mPa·s / 25°C) (a2-2) Epoxy resin having a bisphenol A structure and a polyoxyalkylene structure (EP-1307 (trade name) manufactured by ADEKA Corporation; in the chemical formula shown in (a2), m+n=15.8 (the number of oxyalkylene groups (repeating units) is 15.8), the resin contains 86% by mass of polyalkylene structures (calculated from the chemical structure and epoxy equivalent), the epoxy equivalent is 320 g / eq., and the viscosity is 25,000 mPa s / 25°C) (a2-3) Polyoxyalkylene diglycidyl ether (ED-506 (trade name) manufactured by ADEKA Corporation) (The number of carbon atoms excluding the two glycidoxy groups is 25.2, and the number of oxyalkylene groups (repeating units) is 8.4.)

[0061] (AB) Epoxy resin + epoxy resin toughener The following (ab1-1) to (ab2-2) fall under both (A) and (B). (ab1-1) Polybutadiene elastomer-dispersed epoxy resin (Kane Ace MX-150 (trade name) manufactured by Kaneka Corporation, approximately 40% by mass of core-shell rubber particles (core: polybutadiene rubber, shell: acrylic resin) (corresponding to (B)) dispersed in approximately 60% by mass of epoxy resin (corresponding to (A)), epoxy equivalent: 310 g / eq., viscosity: 16,000 mPa·s / 50°C). (ab1-1) contains approximately 60% by mass of epoxy resin and approximately 40% by mass of epoxy resin toughener (core-shell rubber particles correspond to polybutadiene elastomer). (ab2-1) Urethane-modified epoxy resin (a urethane-modified epoxy resin having 20 or more consecutive repeating polyoxyalkylene structures, obtained by reacting 20 parts by mass of polypropylene triol having a molecular weight of 3,000 with 3.5 parts by mass of TDI (Sumidur T-80 / 20 (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.) to obtain a prepolymer, and then reacting 30 parts by mass of this prepolymer with 70 parts by mass of bisphenol A-type epoxy resin having a hydroxyl value of 30) (ab2-1) contains approximately 70% by mass of epoxy resin moieties (corresponding to bisphenol A-type epoxy resin) and approximately 30% by mass of epoxy resin toughener moieties (the urethane-modified moiety corresponds to polyurethane elastomer). (ab2-2) 15% by mass CTBN (AN (acrylonitrile) > 8% by mass) modified epoxy resin (a CTBN-modified epoxy resin obtained by reacting 15 parts by mass of CTBN (carboxyl-terminated butadiene nitrile rubber, Hypro1300x8 (product name) manufactured by Huntsman) with 85 parts by mass of bisphenol A epoxy resin (jER828 (product name) manufactured by Mitsubishi Chemical Corporation)) (ab2-2) contains approximately 85% by mass of an epoxy resin portion (corresponding to bisphenol A epoxy resin) and approximately 15% by mass of an epoxy resin toughener portion (the CTBN-modified portion corresponds to a CTBN elastomer). (B) Epoxy resin toughener The following (b2-3) applies only to (B). (b2-3) Polymethacrylate resin, average particle size approximately 80 μm (ZEFIAC F-351 (product name) manufactured by AICA Corporation)

[0062] (C) Diluent (c1) Methylphenyl glycidyl ether (ED-529 (trade name) manufactured by ADEKA Corporation) (the number of carbon atoms excluding the glycidyl group is 7.) (c2) Aliphatic phenyl glycidyl ether (LITE2513HP (trade name) manufactured by Cardolite) (the number of carbon atoms excluding the glycidyl group is approximately 21.) (c3) Aliphatic monoglycidyl ether (ED-502 (trade name) manufactured by ADEKA Corporation) (the number of carbon atoms excluding the glycidyl group is 12 to 13)

[0063] (D) Curing agents and curing accelerators (d1) Dicyandiamide (d2) Dimethylurea (Dyhard UR200 (trade name) manufactured by AlzChem) (d3) Imidazole (2PHZ-PW (trade name) manufactured by Shikoku Chemicals Corporation) (d4) Polyamine (ADEKA EH-5030S (trade name))

[0064] (E) Filler (e1) Calcium carbonate (e2) Carbon black (F) Other additives (f1) Epoxy group-containing silane coupling agent (KBM403 (trade name) manufactured by Shin-Etsu Chemical Co., Ltd.) (f2) Calcium oxide

[0065] These components were blended in the parts by mass shown in Tables 1 and 2 to produce one-component thermosetting adhesive compositions of Examples 1 to 10 and Comparative Examples 1 and 2. For each of the one-component thermosetting adhesive compositions described above, the initial adhesive strength, water-resistant adhesive strength (at 70°C for 18 days), humidity-resistant adhesive strength (at 70°C for 18 days at 95% RH), and water-resistant adhesion (after immersion at 40°C) were measured and evaluated using the following methods. The results are shown in Tables 1 and 2.

[0066] Initial adhesive strength A 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 0.8 mm thick SPCC steel plate was used as the adherend, and Pleton R-303PM3 manufactured by Sugimura Chemical Industry Co., Ltd. was used as the rust preventative oil. The curing conditions were 130°C x 15 minutes. The test was conducted in a 23°C environment. The test speed was 50 mm / min. 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 Preton R-303PM3 manufactured by Sugimura Chemical Industry Co., Ltd. was used as the rust preventive oil. The curing conditions were 130°C x 15 minutes. The test environment was 23°C. The test speed was 200 mm / min.

[0067] Water resistance (70℃ 18 days) Adhesive strength For each of the one-component thermosetting adhesive compositions described above, test pieces were prepared using the same method as for the initial adhesive strength test. After storing the test pieces in a 70°C environment for 18 days, shear adhesion tests and T-peel adhesion tests were performed using the same methods as those described for the initial adhesive strength test.

[0068] Moisture resistance (70℃ 95% RH 18 days) Adhesive strength For each of the one-component thermosetting adhesive compositions described above, test pieces were prepared using the same method as for the initial adhesive strength test. After storing the test pieces in an environment of 70°C and 95% RH for 18 days, a shear adhesion test and a T-peel adhesion test were performed using the same method as described for the initial adhesive strength test.

[0069] Adhesion after water resistance (immersion at 40°C) Cross-cut peel test The adhesion test was carried out in accordance with JASO M306-88 Section 5.23. For each of the one-component thermosetting adhesive compositions described above, the composition was applied to a thickness of 0.15 mm on SPCC steel plates as the adherend, and test specimens were prepared in accordance with Section 5.23.2. The curing conditions were 130°C x 15 minutes. The adhesion after water resistance was evaluated by immersing the sample in 40°C warm water for 1 or 10 days, removing it, and then 1 hour later, performing the procedure in accordance with the initial adhesion test in Section 5.23.3 (1). The number of adhered squares out of 100 was indicated.

[0070] [Table 1]

[0071] [Table 2]

[0072] The curable resin compositions of Examples 1 to 10 were not rated x in any of the initial adhesive strength, water-resistant adhesive strength, humidity-resistant adhesive strength, and cross-cut peel test, and showed performance above a certain level, and were excellent in water-resistant adhesion and humidity-resistant adhesion.

[0073] In contrast, Comparative Examples 1 and 2 were marked with "x" in any of the items, and did not exhibit properties above a certain level. [Industrial Applicability]

[0074] The one-component thermosetting adhesive composition of an embodiment of the present invention can provide an adhesive composition that has improved water resistance and moisture resistance compared to conventional adhesive compositions while maintaining various properties that have traditionally been desired (e.g., impact resistance, high adhesive strength to metal substrates, etc.). Therefore, the one-component thermosetting 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. A one-component thermosetting adhesive composition comprising an epoxy resin (A), an epoxy resin toughening agent (B), a reactive diluent (C), an amine-based latent curing agent (D), and a filler (E), The epoxy resin (A) contains (A1) an unmodified bisphenol-type epoxy resin, The epoxy resin toughening agent (B) contains (B1) a low-polarity elastomer, A one-component thermosetting adhesive composition.

2. 2. The one-component thermosetting adhesive composition according to claim 1, wherein the content of the unmodified bisphenol-type epoxy resin (A1) is 30 parts by mass or more and 87 parts by mass or less, 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).

3. The one-component thermosetting adhesive composition according to claim 1, wherein the low-polarity elastomer (B1) comprises at least one selected from the group consisting of a butadiene polymer, an isoprene polymer, an acrylonitrile-butadiene copolymer having an acrylonitrile content of less than 8% by mass, and a styrene-butadiene copolymer having a styrene content of less than 10% by mass.

4. 2. The one-component thermosetting adhesive composition according to claim 1, wherein the epoxy resin toughening agent (B) is in the form of particles having a core-shell structure comprising a core and a shell, the shell comprising an acrylic polymer, and the core comprising the low-polarity elastomer (B1).

5. The one-component thermosetting adhesive composition according to claim 1, wherein the low-polarity elastomer (B1) may contain at least one group selected from an acid anhydride group, a carboxy group, an amino group, an imino group, and an epoxy group.

6. 6. The one-component thermosetting adhesive composition according to claim 5, wherein the low-polarity elastomer (B1) may be a part contained in a modified epoxy resin that has been pre-reacted with an excess of the epoxy resin (A).

7. Assuming that the total amount 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, 2. The one-component thermosetting adhesive composition according to claim 1, comprising 40 parts by mass or more and 85 parts by mass or less of the unmodified bisphenol-type epoxy resin (A1) and 2 parts by mass or more and 25 parts by mass or less of the low-polarity elastomer (B1).

8. The one-component thermosetting adhesive composition according to claim 1 , wherein the reactive diluent (C) comprises a reactive diluent having less than 15 carbon atoms excluding the glycidyl group.

9. The one-component thermosetting adhesive composition according to claim 1 , wherein the reactive diluent (C) includes a reactive diluent having an aromatic ring.

10. 2. The one-component thermosetting adhesive composition according to claim 1, wherein the latent curing agent (D) comprises a latent curing agent containing at least an imidazole having a hydroxyl group.

11. 2. The one-component thermosetting adhesive composition according to claim 1, wherein none of the epoxy resin (A), the epoxy resin toughening agent (B), and the reactive diluent (C) contains a polyoxyalkylene structure having four or more consecutive oxyalkylene groups, or the content of the compounds corresponding to (A) to (D) containing a polyoxyalkylene structure having four or more consecutive oxyalkylene groups is 5 parts by mass or less, 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).

12. 2. The one-component thermosetting adhesive composition according to claim 1, further comprising an additive (F), wherein the additive (F) comprises a silane coupling agent (F1) having an epoxy group.

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