Adhesive and adhesive sheet

Abstract

To provide an epoxy-based adhesive which has excellent adhesion strength while maintaining adhesiveness, does not cause interfacial peeling in the bonding of a material and can cause cohesive failure.SOLUTION: There is provided an epoxy-based adhesive containing an epoxy resin and a curing agent, wherein the epoxy resin includes a bisphenol A-type epoxy resin (A1), a bisphenol F-type epoxy resin (A2) and a rubber-modified epoxy resin (A3), the bisphenol A-type epoxy resin includes at least a liquid bisphenol-A type epoxy resin (A1-1), the bisphenol F-type epoxy resin includes a liquid bisphenol F-type epoxy resin (A2-1) and a solid bisphenol F-type epoxy resin (A2-2), the content ratio of the liquid bisphenol A-type epoxy resin to the liquid bisphenol F-type epoxy resin is 1.0 or more and the content ratio of the solid bisphenol F-type epoxy resin to the liquid bisphenol F-type epoxy resin is less than 1.0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive and an adhesive sheet. More specifically, it relates to an adhesive and an adhesive sheet capable of firmly adhering materials when bonding them together.

Background Art

[0002] The cured product of a resin composition mainly composed of an epoxy resin is excellent in many aspects such as dimensional stability, mechanical strength, electrical insulation, heat resistance, heat resistance, water resistance, chemical resistance, etc., and is used as a structural adhesive for structural panels of vehicles and the like.

[0003] Currently, in the automotive field, the use of adhesives in combination with rivet joining and spot joining is increasing, and generally, structural adhesives with high adhesive strength having high shear adhesive strength are used as the adhesives.

[0004] As such an epoxy-based adhesive used for such applications, by adding rubber, a reinforcing agent, and polymer fine particles to the epoxy resin, the adhesive strength of the adhesive is improved and impact characteristics are imparted.

[0005] For example, Patent Document 1 describes improving the impact resistance and peel strength of a cured product obtained by adding a rubber-modified epoxy resin and a reactive reinforcing agent. Also, Patent Document 2 describes that high adhesive strength can be achieved while maintaining a high elastic modulus by adding an epoxy resin and polymer fine particles. Furthermore, Patent Document 3 describes that both adhesion and adhesiveness can be achieved by adjusting the content of bisphenol A type epoxy resin and bisphenol F type epoxy resin.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, currently, with the increasing functionality of automobiles, the physical properties required of adhesives have been improved, and the places where adhesives are used are diverse. Therefore, a high-strength and good-adhesion adhesive is required.

[0008] Under such circumstances, when the adhesives of Patent Documents 1 and 2 were used for bonding materials, there was a problem that the adhesion to the materials was low and interfacial peeling was likely to occur in areas where the usage amounts of rubber, reinforcing agents, and polymer fine particles were small. Also, when a large amount of rubber was used, although cohesive failure was possible, it was found that there was a fatal problem for use as a structural adhesive in that the adhesive strength decreased due to a large decrease in the elastic modulus. And when the adhesive of Patent Document 3 was used for bonding materials, it was found that although the adhesion was sufficient, the adhesive force was not sufficiently high.

[0009] Therefore, under such a background, the present invention provides an epoxy-based adhesive that maintains adhesion, has excellent adhesive force, does not cause interfacial peeling in bonding materials, and can cause cohesive failure.

Means for Solving the Problems

[0010] However, as a result of intensive research in view of such circumstances, the present inventors focused on bisphenol A type epoxy resin and bisphenol F type epoxy resin, and found that the above problems can be solved by adjusting their properties and ratios, thereby completing the present invention.

[0011] That is, the present invention has the following aspects. [1] An epoxy adhesive containing an epoxy resin (A) and a curing agent (B), wherein the epoxy resin (A) contains a bisphenol A type epoxy resin (A1), a bisphenol F type epoxy resin (A2), and a rubber-modified epoxy resin (A3), the bisphenol A type epoxy resin (A1) contains at least a liquid bisphenol A type epoxy resin (A1-1), the bisphenol F type epoxy resin (A2) contains a liquid bisphenol F type epoxy resin (A2-1) and a solid bisphenol F type epoxy resin (A2-2), the content ratio [(A1-1) / (A2-1)] of the liquid bisphenol A type epoxy resin (A1-1) to the liquid bisphenol F type epoxy resin (A2-1) is 1.0 or more, and the content ratio [(A2-2) / (A2-1)] of the solid bisphenol F type epoxy resin (A2-2) to the liquid bisphenol F type epoxy resin (A2-1) is less than 1.0. An epoxy adhesive. [2] The epoxy adhesive according to [1], wherein the content ratio [(A1) / (A2)] of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) is less than 2.0. [3] The epoxy adhesive according to [1] or [2], wherein the rubber-modified epoxy resin (A3) contains a carboxyl group-terminated butadiene-nitrile rubber-modified epoxy resin and / or a nitrile-butadiene rubber-modified epoxy resin. [4] The epoxy resin (A) further contains an aromatic ring-containing epoxy resin (A4) excluding the above (A1) to (A3), and the aromatic ring-containing epoxy resin (A4) contains at least a solid aromatic ring-containing epoxy resin (A4-1). The epoxy adhesive according to any one of [1] to [3]. [5] The epoxy adhesive according to any one of [1] to [4], wherein the content of the solid epoxy resin is 40% by mass or more based on the total amount of the epoxy resin (A). [6] The epoxy adhesive according to any one of claims [1] to [5], containing dicyandiamide and its derivatives as the hardener (B). [7] The epoxy adhesive according to any one of [1] to [6], further containing polymer fine particles (C) having a core-shell structure. [8] The epoxy adhesive according to any one of [1] to [7], further containing a silane coupling agent (D). [9] The epoxy adhesive according to [8], wherein the silane coupling agent (D) contains an epoxy group.

[10] The epoxy adhesive according to any one of [1] to [9], which is solid at 25°C.

[11] An adhesive sheet containing the epoxy adhesive according to any one of [1] to

[10] .

[12] The adhesive sheet according to

[11] , having an adhesive layer with a thickness of 0.1 to 2 mm.

[13] The adhesive sheet according to

[12] , wherein the adhesive layer is an adhesive layer made of a non-woven fabric impregnated with the epoxy adhesive.

[14] The adhesive sheet according to

[13] , having a release film on at least one surface of the adhesive layer.

Advantages of the Invention

[0012] The epoxy adhesive of the present invention can maintain adhesion while having excellent adhesive strength, causing cohesive failure rather than interfacial peeling in the adhesion of materials.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described based on examples of embodiments for carrying out the present invention. However, the present invention is not limited to the embodiments described below.

[0014] In the present invention, "x and / or y (x and y are arbitrary configurations)" means at least one of x and y, and means three cases: only x, only y, and x and y. When expressed as "X to Y" (where X and Y are arbitrary numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as the meaning of "preferably greater than X" or "preferably less than Y". When expressed as "X or more" (where X is an arbitrary number) or "Y or less" (where Y is an arbitrary number), it also includes the meaning of "preferably greater than X" or "preferably less than Y". In the present invention, "liquid" or "solid" means presenting a "liquid" or "solid" state at room temperature (25 °C).

[0015] <Epoxy resin (A)> The epoxy adhesive which is an embodiment of the present invention (hereinafter sometimes referred to as "this epoxy adhesive") uses epoxy resin (A) as a curing component, and as epoxy resin (A), bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3) are contained as essential constituent components. Hereinafter, various constituent components will be described.

[0016] 〔Bisphenol A type epoxy resin (A1)〕 As the bisphenol A type epoxy resin (A1) used in this embodiment, for example, commercially available products such as jER825, jER826, jER827, jER828, jER834, jER1001 (manufactured by Mitsubishi Chemical Corporation), Epiklon 850 (manufactured by DIC Corporation), Epotote YD-128 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), DER-331, DER-332 (manufactured by Dow Chemical Japan Co., Ltd.), Bakelite EPR154, Bakelite EPR162, Bakelite EPR172, Bakelite EPR173, Bakelite EPR174 (manufactured by Bakelite AG) etc. can be mentioned. Among these, in terms of the elastic modulus and glass transition temperature of the cured product of the epoxy adhesive, jER828 and jER1001 are preferable. These can be used alone or in combination of two or more.

[0017] And the bisphenol A type epoxy resin (A1) used in this embodiment contains at least a liquid bisphenol A type epoxy resin (A1-1). Examples of the liquid bisphenol A type epoxy resin (A1-1) among the bisphenol A type epoxy resins (A1) listed above include jER825, jER828, jER827, Epiklon 850, Epototo YD-128, DER-331, and DER-332. Among these, jER828 is preferable in terms of the elastic modulus and glass transition temperature of the cured product of the epoxy adhesive. These can be used alone or in combination of two or more.

[0018] The number average molecular weight of the bisphenol A type epoxy resin (A1) is usually from 200 to 100,000, preferably from 200 to 80,000, more preferably from 200 to 60,000. If such a number average molecular weight is too low, the viscosity drops too much, and the workability as an adhesive tends to decrease. If it is too high, the solubility in other monomers decreases, and the viscosity rises too much, resulting in a tendency for the workability to decrease. In this specification, the "number average molecular weight" is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

[0019] The epoxy equivalent of the bisphenol A type epoxy resin (A1) is usually 20,000 or less, preferably 10,000 or less, more preferably 6,000 or less. If such an epoxy equivalent is too high, the solubility in other monomers decreases, and the workability during compounding tends to decrease. The lower limit value of the epoxy equivalent is not particularly limited, but is, for example, 50 or more. In this specification, the "epoxy equivalent" is a value measured in accordance with JIS-K7236:2001.

[0020] The softening point of the bisphenol A type epoxy resin (A1) is usually 160°C or lower, preferably 140°C or lower, more preferably 120°C or lower. If such softening point is too high, the viscosity at normal temperature after compounding increases, so the workability as an adhesive tends to deteriorate. The lower limit value of such softening point is not particularly limited, but for example, it is -50°C or higher. In addition, in this specification, the "softening point" is a value measured in accordance with JIS-K7234:2008 (ring and ball method).

[0021] 〔Bisphenol F type epoxy resin (A2)〕 The bisphenol F type epoxy resin (A2) used in this embodiment includes a liquid bisphenol F type epoxy resin (A2-1) and a solid bisphenol F type epoxy resin (A2-2).

[0022] Examples of the liquid bisphenol F type epoxy resin (A2-1) used in this embodiment include commercially available products such as jER806, jER807, jER1750 (manufactured by Mitsubishi Chemical Corporation), Epiclon 830 (manufactured by DIC Corporation), YDF-170, and YDF-170N (manufactured by Nippon Steel Chemical & Material Co., Ltd.). Among these, jER806 and jER807 are preferable in terms of excellent adhesion after curing of the epoxy-based adhesive. These can be used alone or in combination of two or more.

[0023] Examples of the solid bisphenol F type epoxy resin (A2-2) used in this embodiment include commercially available products such as jER4005P, jER4007P, and jER4010P (manufactured by Mitsubishi Chemical Corporation), YEF-2001, and YDF-2004 (manufactured by Nippon Steel Chemical & Material Co., Ltd.). Among these, jER4005P and jER4007P are preferable in terms of excellent adhesion after curing of the epoxy-based adhesive. These can be used alone or in combination of two or more.

[0024] The number average molecular weight of the bisphenol F type epoxy resin (A2) is usually 200 to 100,000, preferably 200 to 80,000, more preferably 200 to 60,000. If the number average molecular weight is too low, the viscosity will drop too much, and the workability as an adhesive will tend to decrease. If it is too high, the solubility in other monomers will decrease, and the viscosity will increase too much, resulting in a tendency for workability to decrease.

[0025] The epoxy equivalent of the bisphenol F type epoxy resin (A2) is usually 20,000 or less, preferably 10,000 or less, more preferably 6,000 or less. If such an epoxy equivalent is too high, the solubility in other monomers will decrease, and the workability during compounding will tend to decrease. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or more.

[0026] The softening point of the bisphenol F type epoxy resin (A2) is usually 160°C or less, preferably 140°C or less, more preferably 120°C or less. If such a softening point is too high, the viscosity at room temperature after compounding will increase, and the workability as an adhesive will tend to decrease. The lower limit of such a softening point is not particularly limited, but for example, it is -50°C or more.

[0027] 〔Rubber-modified epoxy resin (A3)〕 The rubber-modified epoxy resin (A3) used in this embodiment is, for example, an epoxy-terminated adduct of an epoxy resin and at least one non-crosslinked liquid rubber having an epoxide-reactive group (e.g., an amino group or a carboxyl group). These can be used alone or in combination of two or more.

[0028] The epoxy resin used as a raw material for the rubber-modified epoxy resin (A3) is not particularly limited, and examples include bisphenol type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin, glycidylamine type epoxy resin, cyclic epoxy resin, dicyclopentadiene type epoxy resin, phenol novolac type epoxy resin, orthocresol novolac type epoxy resin, and the like.

[0029] The non-crosslinked liquid rubber used as a raw material for the rubber-modified epoxy resin (A3) is preferably a homopolymer of a conjugated diene or a copolymer of a conjugated diene, particularly a diene / nitrile copolymer. The conjugated diene rubber is preferably butadiene or isoprene, and butadiene is particularly preferred. The preferred nitrile monomer is acrylonitrile. The preferred copolymer is a butadiene-acrylonitrile copolymer.

[0030] The glass transition temperature (Tg) of such a non-crosslinked liquid rubber is usually 20°C or lower, preferably 10°C or lower, more preferably 0°C or lower. The lower limit value of such a glass transition temperature is not particularly limited, but is, for example, -100°C or higher. In addition, in this specification, the "glass transition temperature" is represented by the temperature of the inflection point of the DSC curve obtained by measuring the DSC curve of the sample using a differential scanning calorimeter.

[0031] Such a non-crosslinked liquid rubber preferably has an average of 1.5 to 2.5, more preferably an average of 1.8 to 2.2, epoxy-reactive end groups per molecule.

[0032] The number average molecular weight of such a crosslinked liquid rubber is usually 500 to 58000, preferably 1000 to 10000.

[0033] As the rubber-modified epoxy resin (A3), a carboxyl group-terminated butadiene nitrile rubber (CTBN)-modified epoxy resin and a nitrile butadiene rubber (NBR)-modified epoxy resin are preferred, and a carboxyl group-terminated butadiene nitrile rubber (CTBN)-modified epoxy resin is more preferred. Examples of commercially available products include ADEKA Resin EPR series (EPR-1415-1, EPR-2000, EPR-2007, EPR-1630) manufactured by ADEKA Corporation, EPON Resin 58005 and EPON Resin 58006 manufactured by Momentive, Hypox series (Hypox RA 840, Hypox RA 1340, Hypox RF 1341) manufactured by CVC, and the like. Among these, the ADEKA Resin EPR series manufactured by ADEKA Corporation is preferred in terms of excellent adhesion and elastic modulus after curing, and EPR-1630 is more preferred.

[0034] The number average molecular weight of the rubber-modified epoxy resin (A3) is usually from 200 to 200,000, preferably from 200 to 100,000, and more preferably from 200 to 80,000. If such a number average molecular weight is too low, the viscosity drops too much, and the workability as an adhesive tends to decrease. If it is too high, the solubility in other monomers decreases, and the viscosity rises too much, resulting in a tendency for the workability to decrease.

[0035] The epoxy equivalent of the rubber-modified epoxy resin (A3) is usually 10,000 or less, preferably 7,000 or less, and more preferably 5,000 or less. If such an epoxy equivalent is too high, the soft component does not disperse in the cured product, so when stress occurs, stress concentrates on that part, and the adhesive strength tends to decrease. The lower limit value of the epoxy equivalent is not particularly limited, but is, for example, 50 or more.

[0036] The softening point of the rubber-modified epoxy resin (A3) is usually 200°C or lower, preferably 180°C or lower, and more preferably 160°C or lower. If such a softening point is too high, the viscosity at room temperature after compounding increases, and the workability as an adhesive tends to decrease. The lower limit value of such a softening point is not particularly limited, but is, for example, -50°C or higher.

[0037] 〔Aromatic ring-containing epoxy resin (A4)〕 In this embodiment, an aromatic ring-containing epoxy resin (A4) may be further contained. The use of at least a solid aromatic ring-containing epoxy resin (A4-1) (however, excluding bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3)) is preferable in terms of the elastic modulus and glass transition temperature of the cured product. For example, phenol aralkyl type epoxy resin (commercially available product: "YX7700" manufactured by Mitsubishi Chemical Corporation), biphenyl type epoxy resin (commercially available product: "YX4000" manufactured by Mitsubishi Chemical Corporation), naphthalene type epoxy resin, cresol novolak type epoxy resin, triphenylmethane type epoxy resin, polyfunctional phenol type epoxy resin, etc. can be mentioned. Among them, phenol aralkyl type epoxy resin and biphenyl type epoxy resin are preferable in terms of low water absorption, and phenol aralkyl type epoxy resin is more preferable. These can be used alone or in combination of two or more.

[0038] In addition, the aromatic ring-containing epoxy resin (A4) may contain a liquid aromatic ring-containing epoxy resin (A4-2). Examples of the liquid aromatic ring-containing epoxy resin (A4-2) include phenol novolak type epoxy resin (commercially available product: "jER154" manufactured by Mitsubishi Chemical Corporation). These can be used alone or in combination of two or more.

[0039] The number average molecular weight of the aromatic ring-containing epoxy resin (A4) is usually 200 to 100,000, preferably 200 to 80,000, more preferably 200 to 60,000. If such a number average molecular weight is too low, the viscosity drops too much, and the workability as an adhesive tends to decrease. If it is too high, the solubility in other monomers decreases, and the viscosity rises too much, resulting in a tendency for the workability to decrease.

[0040] The epoxy equivalent of the aromatic ring-containing epoxy resin (A4) is usually 10,000 or less, preferably 7,000 or less, more preferably 5,000 or less. If the epoxy equivalent is too high, the solubility in other monomers decreases, and the workability tends to decrease during compounding. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or more.

[0041] The softening point of the aromatic ring-containing epoxy resin (A4) is usually 160°C or lower, preferably 140°C or lower, more preferably 120°C or lower. If such a softening point is too high, the viscosity at room temperature after compounding increases, and the workability as an adhesive tends to decrease. The lower limit of such a softening point is not particularly limited, but for example, it is -50°C or higher.

[0042] This embodiment may further contain other epoxy resins other than (A1) to (A4). Specific examples thereof include various epoxy resins such as alcohol-type epoxy resins, triphenylmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidyl ester-type epoxy resins, glycidyl amine-type epoxy resins, and aliphatic epoxy resins.

[0043] The content of the epoxy resin (A) used in this embodiment is usually 30 to 100% by mass, preferably 40 to 98% by mass, more preferably 50 to 96% by mass, based on the total epoxy-based adhesive.

[0044] The content of the bisphenol A-type epoxy resin (A1) is usually 0.01 to 70% by mass, preferably 0.1 to 60% by mass, more preferably 1 to 50% by mass, based on the total amount of the epoxy resin (A) (the total content of all the epoxy resins (A) contained in the epoxy-based adhesive).

[0045] The content of the liquid bisphenol A-type epoxy resin (A1-1) is usually 50 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, based on the bisphenol A-type epoxy resin (A1).

[0046] The content of the bisphenol F type epoxy resin (A2) is usually 1 to 70% by mass, preferably 5 to 60% by mass, more preferably 10 to 50% by mass, based on the total amount of the epoxy resin (A) (the total content of all the epoxy resins (A) contained in the epoxy adhesive).

[0047] The content ratio [(A1) / (A2)] of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) is usually less than 2.0, preferably less than 1.5, more preferably less than 1.0, and even more preferably less than 0.9. When such a content ratio [(A1) / (A2)] is 2.0 or more, the failure mode becomes interfacial peeling, and the effects of the present invention tend not to be fully exhibited. By making the content ratio of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) less than a specific amount, the adhesion is improved by the bisphenol F type epoxy, and the failure mode becomes cohesive failure, and there is a tendency that highly reliable adhesion becomes possible. The lower limit is usually 0.01 or more.

[0048] The content ratio [(A2-2) / (A2-1)] of the solid bisphenol F type epoxy resin (A2-2) to the liquid bisphenol F type epoxy resin (A2-1) is less than 1.0, preferably less than 0.8, and more preferably less than 0.6. When such a content ratio [(A2-2) / (A2-1)] is 1.0 or more, the crosslinking point spacing becomes long, so the shear adhesive strength decreases, and there is a tendency that sufficient adhesive strength is not exhibited. By making the content ratio [(A2-2) / (A2-1)] of the solid bisphenol F type epoxy resin (A2-2) to the liquid bisphenol F type epoxy resin (A2-1) less than a specific amount, dense crosslinking is performed, so the crosslinking point spacing becomes short, the shear adhesive strength increases, and sufficient adhesive strength is exhibited. The lower limit is usually 0.01 or more.

[0049] The content ratio [(A1-1) / (A2-1)] of the liquid bisphenol A type epoxy resin (A1-1) to the liquid bisphenol F type epoxy resin (A2-1) is 1.0 or more, preferably 1.1 or more, more preferably 1.2 or more. When such a content ratio [(A1-1) / (A2-1)] is less than 1.0, bisphenol F type epoxy with a low molecular weight spreads throughout the adhesive, and due to the softness of the bisphenol F type epoxy, there is a tendency that sufficient adhesive strength is not exhibited because the hardness decreases. By setting the content ratio [(A1-1) / (A2-1)] of the liquid bisphenol A type epoxy resin (A1-1) to a specific amount or more, bisphenol A type epoxy with a low molecular weight can be spread throughout the adhesive, the hardness of the bisphenol A type epoxy can be utilized, and there is a tendency that the shear adhesive strength increases and sufficient adhesive strength is exhibited. The upper limit value is usually 2.0 or less.

[0050] The content of the rubber-modified epoxy resin (A3) is preferably 0.01 to 60% by mass, more preferably 1 to 50% by mass, particularly preferably 5 to 40% by mass, based on the total amount of the epoxy resin (A) (the total content of all epoxy resins (A) contained in the epoxy-based adhesive).

[0051] The content ratio [(A1) / (A3)] of the bisphenol A type epoxy resin (A1) to the rubber-modified epoxy resin (A3) is usually less than 2.5, preferably less than 2.0, more preferably less than 1.8 The lower limit value of such a content ratio is not particularly limited, but is, for example, 0.01 or more.

[0052] The content of the aromatic ring-containing epoxy resin (A4) is usually 0 to 80% by mass, preferably 1 to 70% by mass, more preferably 5 to 60% by mass, based on the total amount of the epoxy resin (A) (the total content of all epoxy resins (A) contained in the epoxy-based adhesive).

[0053] The content of the solid aromatic ring-containing epoxy resin (A4-1) is usually 20 to 100% by mass, more preferably 30 to 100% by mass, and still more preferably 40 to 100% by mass, based on the aromatic ring-containing epoxy resin (A4).

[0054] The content ratio [(A1) / (A4)] of the bisphenol A type epoxy resin (A1) to the aromatic ring-containing epoxy resin (A4) is usually less than 2.0, preferably less than 1.8, and more preferably less than 1.5. The lower limit value of such a content ratio is not particularly limited, but is, for example, 0.01 or more.

[0055] In addition, the content of the solid epoxy resin in the total epoxy resin (A) is usually 30% by mass or more, preferably 35% by mass or more, and more preferably 40% by mass or more. The upper limit value of the content of such an epoxy resin that is solid at normal temperature is not particularly limited, but is, for example, 100% by mass or less.

[0056] <Hardener (B)> Examples of the hardener (B) used in this embodiment include amines, acid anhydrides (carboxylic acid anhydrides), phenols (novolak resins, etc.), mercaptans, Lewis acid amine complexes, onium salts, imidazoles, and the like. Specific examples thereof include the hardeners described in Chapter 3 of "General Review of Epoxy Resins, Volume 1 (edited by the Epoxy Resin Technology Association, first edition, published in November 2003)" and Chapter 2 of "General Review of Epoxy Resins, Recent Progress I (edited by the Epoxy Resin Technology Association, first edition, published in March 2009)". Among these, it is preferable to use amines from the viewpoint of adhesiveness. These can be used alone or in combination of two or more.

[0057] Examples of the amine include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, imidazole derivatives, dicyandiamide, dicyandiamide derivatives, tetramethylguanidine, thiourea-added amines, and isomers and modified products thereof. Among these, dicyandiamide and its derivatives are particularly preferable in terms of excellent pot life of the matrix resin composition.

[0058] The content of the curing agent (B) used in the present embodiment is usually 0.01 to 30% by mass, preferably 0.1 to 25% by mass, more preferably 1 to 20% by mass, based on the total amount of the epoxy resin (A).

[0059] <Polymer fine particles (C) having a core-shell structure> The present embodiment may contain polymer fine particles (C) having a core-shell structure. The polymer fine particles (C) having a core-shell structure mean a known general core-shell type polymer, that is, polymer particles having different molecular structures in the central part (core part) and the outer peripheral part (shell part).

[0060] Examples of the component constituting the core part of the polymer fine particles (C) having a core-shell structure include butadiene rubber (BR), acrylic rubber (ACM), silicone rubber (Si), butyl rubber (IIR), nitrile rubber (NBR), styrene-butadiene rubber (SBR), isoprene rubber (IR), ethylene-propylene rubber (EPR), etc. Among them, butadiene rubber is preferable.

[0061] The component constituting the shell part of the polymer fine particles (C) having a core-shell structure is preferably graft-polymerized to the above-mentioned core part and covalently bonded to the polymer constituting the core component.

[0062] Examples of the component constituting such a shell part include acrylate-based monomers, methacrylate-based monomers, and aromatic vinyl monomers.

[0063] The polymer fine particles (C) having a core-shell structure include, for example, commercially available products such as the KANE-ACE series (B-11A, B-22, B-561, FM-21, M-701, M-711, M-300, FM-40, M-210, Pa-20, Pa-101, MR-01, MX-153, MX-257, MX-154, MX-960, MX-136, MX-965, MX-217, MX-227M75, MX-334M75, MX-416, MX-451, etc.) manufactured by Kaneka Corporation, and Metablen (Metablen C, Metablen E, Metablen W, Metablen S, etc.) manufactured by Mitsubishi Chemical Corporation.

[0064] Among these, those with a rubber-type core part are preferable from the viewpoints of flexibility and adhesion. Further, the polymer fine particles (C) having a core-shell structure may be used as they are in the form of particles, or may be used after being dispersed in other solutions or resins. From the viewpoint of uniform dispersion in other resins, those dispersed in an epoxy resin are more preferable, and specifically, MX-153, MX-154, and MX-136 are preferable.

[0065] The polymer fine particles (C) having a core-shell structure may be used alone or in combination of two or more.

[0066] The primary particle diameter of the polymer fine particles (C) having a core-shell structure used in this embodiment is usually 10 to 100,000 nm, preferably 15 to 50,000 nm, and more preferably 20 to 10,000 nm, based on the elastic modulus, elongation physical properties, and shear strength of the cured product obtained from the epoxy resin. The primary particle diameter represents the volume average particle diameter of the primary particles and can be measured, for example, using a NanoTrack particle size distribution measuring device (manufactured by Nikkiso Co., Ltd.).

[0067] Regarding the polymer fine particles (C) having a core-shell structure, when a dispersion of bisphenol A type epoxy resin (A1) or bisphenol F type epoxy resin (A2) is used, when calculating the content ratios of (A1) / (A2) and (A1) / (A3), the (A1) and (A2) used for dispersion shall be added and the content ratios shall be calculated.

[0068] The content of the polymer fine particles (C) having a core-shell structure is usually 0 to 50% by mass, preferably 1 to 40% by mass, more preferably 2 to 30% by mass, based on the entire epoxy-based adhesive excluding the curing agent (B).

[0069] <Silane coupling agent (D)> In addition, in this embodiment, it is preferable to further contain a silane coupling agent (D) within a range that does not impair the effects of the present invention.

[0070] The silane coupling agent (D) is an organosilicon compound containing at least one alkoxy group bonded to a reactive functional group and a silicon atom in its structure, and it is preferably contained in this epoxy-based adhesive in terms of improving durability.

[0071] Examples of the reactive functional group in the above silane coupling agent (D) include an epoxy group, a (meth)acryloyl group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, an isocyanate group, etc. Among these, an epoxy group and a mercapto group are preferable in terms of excellent durability.

[0072] The content ratio of the reactive functional group in the above silane coupling agent (D) is usually 3000 g / mol or less, preferably 1500 g / mol or less, more preferably 800 g / mol or less. Within the above range, there is a tendency to have an excellent balance of durability.

[0073] As the alkoxy group in the above silane coupling agent (D), it is preferably a C1-C8 alkoxy group from the viewpoints of durability and storage stability, and particularly preferably contains a methoxy group or an ethoxy group.

[0074] In addition, the above silane coupling agent (D) may have an organic functional group other than the reactive functional group and the alkoxy group bonded to the silicon atom, such as an alkyl group, a phenyl group, etc.

[0075] From the viewpoint of durability, the weight average molecular weight of the above silane coupling agent (D) is usually 1000 or more, preferably 2300-30000, more preferably 3000-20000. When such a weight average molecular weight is within the above range, it tends to have an excellent balance of durability.

[0076] In addition, the above weight average molecular weight is the weight average molecular weight in terms of standard polystyrene molecular weight and can be measured by the following method. · Apparatus: Gel permeation chromatograph · Detector: Differential refractive index detector RI (manufactured by Tosoh Corporation, RI-8020 type, sensitivity 32) · Column: TSKgel guardcolumn HHR-H (1 piece) (manufactured by Tosoh Corporation, φ6mm×4cm), TSKgel GMHHR-N (2 pieces) (manufactured by Tosoh Corporation, φ7.8mm×30cm) · Solvent: Tetrahydrofuran (THF) · Column temperature: 23°C · Flow rate: 1.0 mL / min

[0077] The above silane coupling agent (D) is preferably an oligomeric organosilicon compound (organosiloxane compound) such as a dimer or trimer formed by hydrolysis and polycondensation of a part of the organosilicon compound, from the viewpoint of durability. For example, a mercapto group-containing oligomeric silane coupling agent formed by hydrolysis and polycondensation of a part of a mercapto group-containing silane compound such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyl dimethoxymethylsilane; a mercapto group-containing oligomeric silane coupling agent which is a co-condensate of the above mercapto group-containing silane compound and an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane; an epoxy group-containing oligomeric silane coupling agent formed by hydrolysis and polycondensation of a part of an epoxy group-containing silane compound such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, methyltri(glycidyl)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane; an epoxy group-containing oligomeric silane coupling agent which is a co-condensate of the above epoxy group-containing silane compound and an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane; an epoxy group-containing oligomeric silane coupling agent obtained by ether-modifying a part of these epoxy group-containing oligomeric silane coupling agents, and the like can be mentioned. These may be used alone or in combination of two or more.

[0078] As the oligomeric silane coupling agent, the alkoxy group content is usually 1 to 60% by mass, preferably 3 to 50% by mass, more preferably 5 to 25% by mass, which is preferable in terms of excellent durability balance.

[0079] As the oligomeric silane coupling agent, specifically, commercially available epoxy group-containing silane coupling agents such as "KBM-402", "KBM-403", "KBE-402", "KBE-403", "X-41-1053", "X-41-1059A", "X-24-9590" manufactured by Shin-Etsu Chemical Co., Ltd. can be mentioned. Among these, KBM-403 and KBE-403 are preferable, and KBM-403 is more preferable in terms of excellent adhesion.

[0080] <Hardening accelerator (E)> In this embodiment, from the viewpoint of enhancing the hardening activity of the hardening agent (B), a hardening accelerator (E) may be contained. For example, among the hardening agents (B), dicyandiamide etc. have a high hardening temperature alone, so in order to enhance the hardening activity of dicyandiamide etc., a hardening accelerator (E) can be used. As the hardening accelerator for dicyandiamide, for example, 3-phenyl-1,1-dimethylurea, U-CAT3513N, U-CAT3512T (manufactured by San-Apro Ltd.), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,4-diamino-6-(2-methylimidazolyl-(1))-ethyl-s-triazine, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 4,4-methylenebis(1,1-dimethyl-3-phenylurea), urea derivatives such as 2,4-bis(3,3-dimethylureido)toluene, aliphatic dimethylurea, aromatic dimethylurea, imidazole derivatives etc. can be mentioned. Among these, urea derivatives and aliphatic dimethylurea are preferable, and DCMU and U-CAT3513N are more preferable.

[0081] The content of the hardening accelerator (E) used in this embodiment is preferably 0.01 to 60% by mass, more preferably 0.05 to 50% by mass, and particularly preferably 0.1 to 30% by mass with respect to the whole hardening agent (B).

[0082] <Epoxy adhesive> This epoxy adhesive contains, as the epoxy resin (A), three components: bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3), and further contains a curing agent (B) as an essential constituent. More preferably, it contains an aromatic ring-containing epoxy resin (A4), polymer fine particles (C) having a core-shell structure, a silane coupling agent (D), and a curing accelerator (E).

[0083] In addition, in the present invention, within a range that does not inhibit the effects of the present invention (for example, with a content of 30% by mass or less based on the total epoxy adhesive), other compounding components can be used as necessary. Examples of other compounding components include dehydrating agents such as calcium oxide, colorants such as pigments and dyes, extender pigments, ultraviolet absorbers, antioxidants, stabilizers (anti-gelling agents), plasticizers, leveling agents, defoaming agents, antistatic agents, flame retardants, lubricants, viscosity reducers, low shrinkage agents, organic fillers, inorganic fillers, thermoplastic resins, desiccants, dispersants, and the like.

[0084] This epoxy adhesive is preferably solid at room temperature (25°C) from the viewpoint of preventing dripping when considering adhesion in the adhesion of dissimilar materials. On the other hand, from the viewpoint of smoothly adhering to the adherend, the softening point of the epoxy adhesive is preferably 160°C or lower, more preferably 140°C or lower, and particularly preferably 120°C or lower. The lower limit value of such a softening point is not particularly limited, but is, for example, 30°C or higher.

[0085] The viscosity of this epoxy adhesive at 60°C and 1 atm is preferably 0.01 to 20000 Pa·s, particularly preferably 0.01 to 10000 Pa·s, more preferably 0.01 to 8000 Pa·s, and even more preferably 0.01 to 5000 Pa·s. Also, the viscosity may preferably be 0.05 to 4000 Pa·s, 0.1 to 3000 Pa·s, 1 to 1000 Pa·s, or 10 to 800 Pa·s. If such a viscosity is too high or too low, the coatability on the base material when used as an adhesive tends to decrease. Note that such viscosity is measured at 60 °C using a B-type rotational viscometer (Brookfield viscometer) in accordance with JIS Z 8803.

[0086] This epoxy adhesive is suitably used not only for bonding of the same kind of materials but also for bonding of different kinds of materials. The combination of different kinds of materials is not particularly limited. For example, combinations of two kinds selected from various materials such as hot-rolled steel sheets, cold-rolled steel sheets, high-tensile steel sheets, stainless steel sheets, plated steel sheets (zinc-plated steel sheets, zinc-nickel steel sheets, etc.), aluminum plates, aluminum alloy plates (aluminum-manganese alloy plates, aluminum-magnesium alloy plates, etc.), fiber-reinforced plastics (FRP) plates such as carbon fibers and glass fibers, and carbon fiber-reinforced plastics (CFRP) can be mentioned. Among them, the epoxy adhesive of the present invention is suitably used for bonding of dissimilar metals and CFRP. Among dissimilar metals, it is particularly preferable to use it for bonding of metals mainly composed of iron and aluminum.

[0087] <Method for manufacturing epoxy adhesive> This epoxy adhesive can be manufactured by mixing each component.

[0088] As for the mixing method of the above-mentioned each component, it is preferable to heat and liquefy some epoxy resins and liquefiable components and then mix them. The mixing temperature is preferably 30 °C or higher, more preferably 40 °C or higher, and particularly preferably 50 °C or higher. On the other hand, it is preferably 150 °C or lower, more preferably 140 °C or lower, and particularly preferably 120 °C or lower. When the mixing temperature is below the lower limit value, there is a tendency for poor mixing due to solidification of each component, and when it is above the upper limit value, there is a tendency for the mixture to polymerize and gel during mixing.

[0089] The mixing time is usually 1 minute or longer, preferably 10 minutes or longer, particularly preferably 20 minutes or longer, and usually 24 hours or shorter, preferably 18 hours or shorter, particularly preferably 12 hours or shorter. When the mixing time is less than the lower limit value, there is a tendency that uniform mixing cannot be achieved, and when it exceeds the upper limit value, there is a tendency for the mixture to polymerize and gel during mixing.

[0090] For the mixing method of the above-mentioned respective components, methods that apply various shearing forces generally used for mixing epoxy adhesives, such as stirring, shaking, kneading, etc., can be used. This mixing method is variously selected according to the physical properties of the adhesive, production volume, etc. The state of the obtained epoxy adhesive may be a uniform state or a non-uniform state in which particles are dispersed. This state is variously selected according to the use as an adhesive.

[0091] From the viewpoint of handleability, this epoxy adhesive is preferably a one-component adhesive.

[0092] After applying the present invention to one or both of a plurality of members having different linear expansion coefficients, sandwiching the adhesive between the dissimilar members and bonding them, and then curing the adhesive, a laminate in which the dissimilar members are joined can be obtained.

[0093] Such curing conditions are not particularly limited. For example, when using a one-component adhesive, by heating to a temperature of 80°C or higher, preferably 130°C or higher, more preferably 150°C or higher, it can be cured preferably within 60 minutes, more preferably within 30 minutes, and a laminate in which dissimilar members are joined can be obtained.

[0094] <Adhesive sheet> This epoxy adhesive can be suitably used as an adhesive sheet containing the epoxy adhesive, and among them, an adhesive sheet for bonding dissimilar materials used for bonding dissimilar materials is particularly preferred. The adhesive sheet containing this epoxy adhesive may, for example, have an adhesive layer obtained by using the above-mentioned epoxy adhesive on a base film, or may have an adhesive layer obtained by impregnating a support with the above-mentioned epoxy adhesive.

[0095] When providing an adhesive layer containing the epoxy-based adhesive on a base film, it is preferable to use a release-treated release film such as silicone or melamine as the base film. Specifically, a release-treated PET film, a polyethylene-based film, a polypropylene-based film, a fluorine-based film, a polyimide film, etc. can be used.

[0096] Also, when impregnating the support with the epoxy-based adhesive, as the support, for example, a non-woven fabric, a porous material, etc. can be used, and among them, a non-woven fabric is preferable. From the viewpoints of suppressing resin flow during pressurization when bonding a plurality of members, retaining the resin in the sheet-like adhesive, and improving adhesiveness due to the rigidity of the adhesive layer, the density of the support is preferably 0.05 g / cm 3 or more, more preferably 0.08 g / cm 3 or more, and even more preferably 0.1 g / cm 3 or more. Also, from the viewpoints of improving the impregnation property of the resin into the support in the adhesive sheet, improving lightness, and improving interfacial adhesion, it is preferably 1.0 g / cm 3 or less, more preferably 0.9 g / cm 3 or less, and even more preferably 0.8 g / cm 3 or less.

[0097] The thickness of the adhesive layer in the adhesive sheet is preferably 0.1 to 2.0 mm. When the thickness of the adhesive layer is within the above numerical range, the adhesiveness when bonding a plurality of members with different linear expansion coefficients can be improved while reducing warping. Among them, the thickness of the adhesive layer is preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. Also, since the tensile shear adhesive strength after bonding improves as the thickness of the adhesive layer becomes thinner, the thickness of the adhesive layer is preferably 1.8 mm or less, more preferably 1.6 mm or less, and even more preferably 1.4 mm or less.

[0098] The adhesive sheet can be obtained by forming an epoxy-based adhesive into a sheet shape. Examples of the method of forming into a sheet shape include a method of laminating or applying the epoxy-based adhesive on a base film to obtain a laminate of base film / epoxy-based adhesive / base film. Specifically, methods using an extrusion laminator such as a T-die, a calendar roll, a sheet forming apparatus such as a double belt press, a comma coating method, a gravure coating method, a reverse coating method, a knife coating method, a dip coating method, a spray coating method, an air knife coating method, a spin coating method, a roll coating method, a printing method, a dip method, a slide coating method, a curtain coating method, a die coating method, a casting method, a bar coating method, an extrusion coating method, etc. can be mentioned.

[0099] At the time of the above sheet forming, an impregnation step of impregnating the support with the epoxy-based adhesive may be performed. As the impregnation method of the epoxy-based adhesive in the impregnation step, a known method may be used. Examples of the impregnation method include, for example, laminating the one provided with the epoxy-based adhesive on the base film in the above sheet forming step and the support so as to be base film / epoxy-based adhesive / support / epoxy-based adhesive / base film, and impregnating using a vacuum laminator, a calendar roll, a double belt press, etc., a dip & nip method of directly impregnating the support with the epoxy-based adhesive, a kiss coating method, a spray method, a curtain coating method, etc. The thickness of the support and the amount of the epoxy-based adhesive impregnated into the support are preferably adjusted so that the thickness of the adhesive layer becomes 0.1 to 2.0 mm.

[0100] The laminate obtained by using the epoxy-based adhesive of the present invention can be used as a structural member (panel parts, frame parts, undercarriage parts, etc.) of transportation equipment such as vehicles, aircraft, and ships. In particular, it is preferably used as a structural panel, and in particular, it is useful as a vehicle structural panel.

Example

[0101] Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as it does not exceed the gist thereof. In the examples, "parts" and "%" mean mass basis.

[0102] First, each component of the epoxy-based adhesive used in the examples and comparative examples was prepared.

[0103] <Epoxy resin (A)> · Epoxy resin 1: Bisphenol A type epoxy resin (A1-1-1) ("jER828" manufactured by Mitsubishi Chemical Corporation, liquid at room temperature) · Epoxy resin 2: Bisphenol F type epoxy resin (A2-1-1) ("jER807" manufactured by Mitsubishi Chemical Corporation, liquid at room temperature) · Epoxy resin 3: Bisphenol F type epoxy resin (A2-2-1) ("jER4005P" manufactured by Mitsubishi Chemical Corporation, solid at room temperature) · Epoxy resin 4: Rubber-modified (CTBN-modified) epoxy resin (A3-1) (solid at room temperature), 15% dispersion of bisphenol A type epoxy resin (A1-1-2) (liquid at room temperature) ("EPR-1630" manufactured by ADEKA Corporation) [Rubber-modified epoxy resin (A3): Bisphenol A type epoxy resin (A1-1-2) = 85:15] · Epoxy resin 5: Phenol aralkyl type epoxy resin (A4-1-1) ("YX7700" manufactured by Mitsubishi Chemical Corporation, solid at room temperature) · Epoxy resin 6: Phenol novolac type epoxy resin (A4-2-1) ("jER154" manufactured by Mitsubishi Chemical Corporation, liquid at room temperature)

[0104] <Hardener (B)> · Hardener (B-1): Dicyandiamide ("DICY7" manufactured by Mitsubishi Chemical Corporation)

[0105] <Polymer fine particles (C) having a core-shell structure> · Core-shell particles 1: A 60% dispersion of bisphenol A type epoxy resin (A1-1-3) (liquid at room temperature) in core-shell rubber (C-1) (manufactured by Kaneka Corporation, "Kane Ace MX-154") [Polymer particles (C-1) having a core-shell structure: bisphenol A type epoxy resin (A1-1-3) = 40:60]

[0106] <Silane coupling agent (D)> · Silane coupling agent (D-1): 3-Glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., "KBM-403")

[0107] <Curing accelerator (E)> · Curing accelerator (E-1): 3-(3,4-Dichlorophenyl)-1,1-dimethylurea (manufactured by Tokyo Chemical Industry Co., Ltd., "DCMU") · Curing accelerator (E-2): Aliphatic dimethylurea (manufactured by San-Apro Co., Ltd., (U-CAT3513N))

[0108] <Preparation of epoxy adhesive> [Example 1] 10 parts of epoxy resin 1, 20 parts of epoxy resin 2, 10 parts of epoxy resin 3, 20 parts of epoxy resin 4, 20 parts of epoxy resin 5, and 20 parts of core-shell particles 1 were mixed and then stirred at 100 °C until homogeneous. After placing it in a constant temperature bath at 70 °C to make the resin temperature 70 °C, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (E-1) were further added and stirred until homogeneous to obtain an adhesive. The adhesive of Example 1 was solid at 25 °C.

[0109] [Example 2] An adhesive was obtained in the same manner as in Example 1, except that the curing accelerator (E-1) was changed to 4 parts. The adhesive of Example 2 was solid at 25 °C.

[0110] [Example 3] An adhesive was obtained in the same manner as in Example 1, except that the curing accelerator (E-1) was changed to the curing accelerator (E-2). The adhesive of Example 3 was solid at 25 °C.

[0111] [Example 4] An adhesive was obtained in the same manner as in Example 1, except that the curing agent (B-1) was changed to 4 parts. The adhesive of Example 4 was solid at 25°C.

[0112] [Example 5] 10 parts of epoxy resin 1, 20 parts of epoxy resin 2, 10 parts of epoxy resin 3, 20 parts of epoxy resin 4, 20 parts of epoxy resin 5, 20 parts of core-shell fine particles 1, and 0.5 part of silane coupling agent (D-1) were mixed, and then stirred at 100°C until uniform. After placing it in a constant temperature bath at 70°C to make the resin temperature 70°C, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (E-1) were further added and stirred until uniform to obtain an adhesive. The adhesive of Example 5 was solid at 25°C.

[0113] [Example 6] 10 parts of epoxy resin 1, 20 parts of epoxy resin 2, 10 parts of epoxy resin 3, 20 parts of epoxy resin 4, 10 parts of epoxy resin 5, 10 parts of epoxy resin 6, and 20 parts of core-shell fine particles 1 were mixed, and then stirred at 100°C until uniform. After placing it in a constant temperature bath at 70°C to make the resin temperature 70°C, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (E-1) were further added and stirred until uniform to obtain an adhesive. The adhesive of Example 6 was solid at 25°C.

[0114] [Example 7] An adhesive was obtained in the same manner as in Example 6, except that epoxy resin 5 was changed to 20 parts and core-shell fine particles 1 was changed to 10 parts. The adhesive of Example 7 was solid at 25°C.

[0115] [Example 8] An adhesive was obtained in the same manner as in Example 6, except that epoxy resin 5 was changed to 20 parts, epoxy resin 6 was changed to 5 parts, and core-shell fine particles 1 was changed to 15 parts. The adhesive of Example 8 was solid at 25°C.

[0116] [Examples 9, 10] The adhesives obtained in Examples 1 and 5 were respectively applied onto a PET film (manufactured by Mitsui Chemicals Toagosei Co., Ltd., "SPPET100 - O1BU", 100 μm) that had been subjected to silicone release treatment as the base film, and impregnated into a glass fiber non - woven fabric (manufactured by Olivest Co., Ltd., "RAP - 110", density 0.16 g / cm 3 , thickness 0.77 mm). From the other side, another base film was inserted, and using a laminator, the adhesive sheets of Examples 9 and 10 (adhesive sheet thickness 0.8 mm) were produced.

[0117] [Comparative Example 1] In Example 1, an adhesive was obtained in the same manner as in Example 1, except that epoxy resin 1 was not used and epoxy resin 3 was changed to 20 parts. The adhesive of Comparative Example 1 was solid at 25°C.

[0118] [Comparative Example 2] In Example 1, an adhesive was obtained in the same manner as in Example 1, except that epoxy resin 2 was changed to 10 parts and epoxy resin 3 was changed to 20 parts. The adhesive of Comparative Example 2 was solid at 25°C.

[0119] [Comparative Example 3] In Example 6, an adhesive was obtained in the same manner as in Example 6, except that epoxy resin 1 was not used and epoxy resin 5 was changed to 20 parts. The adhesive of Comparative Example 3 was solid at 25°C.

[0120] The compositions of the adhesives obtained in the above Examples 1 - 10 and Comparative Examples 1 - 3 are shown in Tables 1 and 2 below. Note that the contents shown in Tables 1 and 2 are values rounded to the first decimal place.

[0121]

Table 1

[0122]

Table 2

[0123] [Tensile Shear Adhesion Measurement] Using the adhesives obtained in Examples 1 to 8 and Comparative Examples 1 to 3, and the adhesive sheets obtained in Examples 9 and 10, the following tensile shear adhesive strength measurements were carried out. The results are shown in Table 2 above. Using an Fe (SPCC steel sheet) test piece (Standard Test Piece SPCC-SB manufactured by Nippon Test Panel Co., Ltd.), the tensile shear adhesive strength was measured by the following method. For the Fe (SPCC steel sheet) test piece, degreasing with toluene was carried out before use, and it was immersed in Pretone R-303L (manufactured by Sugimura Chemical Industry Co., Ltd.) as a rust preventive oil for about 3 seconds and hung for 15 minutes to remove excess rust preventive oil before use. The adhesive obtained above was applied to the surface of an Fe test piece (100 mm × 25 mm × thickness 1.6 mm) to a thickness of about 12.5 mm × 25 mm × thickness 0.8 mm, and further covered with a spacer from above to adjust the thickness. Another same Fe test piece was placed on the adhesive, and two binder grips (No. 107 manufactured by Lion Corporation) were used to sandwich both test pieces for crimping to make the Fe / Fe thickness constant. After crimping, it was heated at 160 °C for 10 minutes in a hot air drying oven for curing treatment to obtain a measurement sample. After cooling to room temperature (25 °C), it was left standing at 23 °C and 50% RH for 24 hours or more, and in accordance with JIS K6850, the tensile shear adhesive strength of the measurement sample was measured using a tensile testing machine (Autograph AG-X manufactured by Shimadzu Corporation). The test speed was 2.5 mm / min, and the test environment was 23 °C and 50% RH. In addition, when evaluating with the adhesive sheets of Examples 9 and 10, no spacer for thickness adjustment was added, and the examination was carried out under the same conditions as above.

[0124] (Adhesive Strength Evaluation Criteria) Based on the above tensile shear adhesive strength and the failure mode, the adhesive strength was evaluated. The results are shown in Table 2 above. For the results of the tensile shear test, using the value of the maximum breaking point of the tensile testing machine, when the tensile shear adhesive strength is "25 MPa or more" and the failure mode is "cohesive failure", it is marked as 〇 (Very good), and when the tensile shear adhesive strength is "less than 25 MPa" or the failure mode is "interface peeling", it is marked as × (Poor). In addition, for the failure mode, the adhesion surface of the Fe test piece after peeling was visually and tactilely inspected. If the cured adhesive adhered to an area of 50% or more of both test plates with respect to the bonded area, it was evaluated as cohesive failure. If the adhesive adhered to an area of less than 50% on either one of the test pieces, it was evaluated as interfacial peeling.

[0125] <Sheet formation suitability evaluation> It was evaluated whether the adhesive sheets obtained in Examples 9 and 10 above were suitable for sheet formation. The results are shown in Table 2 above. As the sheet formation suitability evaluation, it was confirmed by the above adhesion evaluation and the peelability evaluation of the following release film. The peelability of the release film was confirmed by whether resin remained on the release film side when the release film was peeled at room temperature. When less than 1% of the resin remained visually on the release film side when the release film was peeled, it was rated as 〇 (Very good). When the above adhesion evaluation was 〇 and the release film evaluation was ○, the sheet formation suitability was evaluated as ○ (Very good).

[0126] As shown in Tables 1 and 2 above, the adhesives obtained in Examples 1 to 8 and the adhesive sheets obtained in Examples 9 and 10 had a tensile shear adhesive strength of 25 MPa or more and a failure mode of cohesive failure. This is because the solid bisphenol F type epoxy resin (A2-2) in the bisphenol F type epoxy resin (A2) was contained less than the liquid bisphenol F type epoxy resin (A2-1), and the liquid bisphenol A type epoxy resin (A1-1) was contained equal to or more than the liquid bisphenol F type epoxy resin (A2-2). As a result, the bisphenol A type epoxy resin spread throughout the system and, when cured, the hardness of the bisphenol A type epoxy resin was exhibited, improving the tensile shear adhesive strength. It is considered that this made the adhesives excellent in adhesive strength and suitable for sheet formation. Therefore, it is considered that the adhesives of Comparative Examples 1 to 3 have poor adhesive strength because the ratios of the liquid bisphenol F-type epoxy resin (A2-1) and the solid bisphenol F-type epoxy resin (A2-2) in the bisphenol F-type epoxy resin (A2), and the ratio of the liquid bisphenol A-type epoxy resin (A1-1) and the liquid bisphenol F-type epoxy resin (A2-2) are not specific amounts.

Industrial Applicability

[0127] The epoxy-based adhesive of the present invention can be used for structural parts (such as skeletons and panel parts) of transportation equipment for vehicles, aircraft, and ships, and members for construction, building materials, etc., and is particularly useful for structural members for vehicles.

Claims

1. An epoxy adhesive comprising an epoxy resin (A) and a curing agent (B), wherein the epoxy resin (A) contains a bisphenol A type epoxy resin (A1), a bisphenol F type epoxy resin (A2), and a rubber-modified epoxy resin (A3), the bisphenol A type epoxy resin (A1) contains at least a liquid bisphenol A type epoxy resin (A1-1), the bisphenol F type epoxy resin (A2) contains a liquid bisphenol F type epoxy resin (A2-1) and a solid bisphenol F type epoxy resin (A2-2), the content ratio [(A1-1) / (A2-1)] of the liquid bisphenol A type epoxy resin (A1-1) to the liquid bisphenol F type epoxy resin (A2-1) is 1.0 or more, and the content ratio [(A2-2) / (A2-1)] of the solid bisphenol F type epoxy resin (A2-2) to the liquid bisphenol F type epoxy resin (A2-1) is less than 1.0, an epoxy adhesive.

2. The epoxy adhesive according to claim 1, wherein the content ratio [(A1) / (A2)] of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) is less than 2.

0.

3. The epoxy adhesive according to claim 1, wherein the rubber-modified epoxy resin (A3) contains a carboxyl group-terminated butadiene-nitrile rubber-modified epoxy resin and / or a nitrile-butadiene rubber-modified epoxy resin.

4. The epoxy resin (A) further contains an aromatic ring-containing epoxy resin (A4) excluding the above (A1) to (A3), and the aromatic ring-containing epoxy resin (A4) contains at least a solid aromatic ring-containing epoxy resin (A4-1), the epoxy adhesive according to claim 1.

5. The epoxy adhesive according to claim 4, wherein the solid epoxy resin content is 40% by mass or more based on the total epoxy resin (A).

6. The epoxy adhesive according to claim 1, wherein the curing agent (B) contains dicyandiamide and its derivatives.

7. Furthermore, the epoxy adhesive according to claim 1, which contains polymer fine particles (C) having a core-shell structure.

8. Furthermore, the epoxy adhesive according to claim 7, which contains a silane coupling agent (D).

9. The epoxy adhesive according to claim 8, wherein the silane coupling agent (D) contains an epoxy group.

10. The epoxy adhesive according to claim 1, which is solid at 25°C.

11. An adhesive sheet comprising the epoxy adhesive according to any one of claims 1 to 10.

12. The adhesive sheet according to claim 11, having an adhesive layer with a thickness of 0.1 to 2 mm.

13. The adhesive sheet according to claim 12, wherein the adhesive layer is an adhesive layer made of a nonwoven fabric impregnated with the epoxy adhesive.

14. The adhesive sheet according to claim 13, having a release film on at least one surface of the adhesive layer.

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