Adhesives, adhesives for bonding dissimilar materials, adhesive sheets, and adhesive sheets for bonding dissimilar materials

Abstract

The present invention provides an epoxy adhesive which is capable of undergoing cohesive failure without the occurrence of interfacial debonding even in cases where dissimilar materials are bonded by the epoxy adhesive, while maintaining good bonding strength.　An epoxy adhesive which contains an epoxy resin (A) and a curing agent (B), and which is characterized in that: a bisphenol A epoxy resin (A1), a bisphenol F epoxy resin (A2) and a rubber-modified epoxy resin (A3) are contained as the epoxy resin (A); and the content ratio of the bisphenol A epoxy resin (A1) to the bisphenol F epoxy resin (A2), namely (A1) / (A2) is less than 2.7.

Description

Technical Field

[0001] The present invention relates to an adhesive. More specifically, it relates to an adhesive capable of firmly bonding different materials (especially bonding of different metals) 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, water resistance, chemical resistance, etc., and is used as a structural adhesive for structural panels of vehicles and the like. Currently, in the automotive field, the use of adhesives in combination with riveting and spot welding is increasing. The adhesives used are generally structural adhesives with high adhesive strength, and those with high shear adhesive strength are selected.

[0003] As such epoxy-based adhesives used for such applications, by adding rubber, reinforcing agents, polymer fine particles, etc. to the epoxy resin, the adhesive strength of the adhesive is improved and impact characteristics are imparted. For example, in Patent Document 1, it is described that the impact resistance and peel strength of a cured product obtained by adding a rubber-modified epoxy resin and a reactive reinforcing agent are improved. Also, in Patent Document 2, it is described that by adding an epoxy resin and polymer fine particles, high adhesive force can be achieved while maintaining a high elastic modulus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in order to reduce the environmental impact, efforts are currently underway to lighten vehicle bodies, and in addition to the conventionally used iron, a wide range of materials such as aluminum and carbon fiber reinforced plastic (CFRP) are being used in automobiles and other vehicles. It is known that when bonding dissimilar materials, problems such as adhesion defects, i.e., interfacial delamination, which did not occur when bonding identical materials, are likely to occur. In this situation, when the adhesives described in Patent Documents 1 and 2 were used to bond dissimilar materials, it was found that in areas where the amount of rubber, reinforcing agent, and polymer fine particles used was small, adhesion to the materials was poor and interfacial delamination was likely to occur. On the other hand, although it was possible to cause cohesive failure by using a large amount of rubber, a decrease in elastic modulus occurred, resulting in a decrease in adhesive strength. This presented a fatal problem for use as a structural adhesive.

[0006] Therefore, against this background, the present invention provides an epoxy adhesive that can maintain adhesive strength while preventing interfacial delamination and causing cohesive failure even when bonding dissimilar materials. [Means for solving the problem]

[0007] However, in light of these circumstances, the present inventors conducted extensive research and found that the problem can be solved by providing an adhesive containing an epoxy resin (A) including bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3), and a curing agent (B) in a specific composition ratio. That is, conventionally, when using both bisphenol A type epoxy resin (A1) and bisphenol F type epoxy resin (A2), it was common to use considerably more bisphenol A type epoxy resin (A1) than bisphenol F type epoxy resin (A2) in order to improve the elastic modulus of the cured product and raise the glass transition temperature. However, by setting the content ratio of bisphenol A type epoxy resin (A1) to bisphenol F type epoxy resin (A2) to a specific amount or less, it was unexpectedly found that adhesion could be improved while maintaining adhesive strength in bonding dissimilar materials, preventing interfacial delamination and enabling cohesive failure.

[0008] In other words, the present invention provides the following [1] to

[15] . [1] An epoxy adhesive comprising an epoxy resin (A) and a hardening agent (B), The epoxy resin (A) includes bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3). An epoxy adhesive characterized in that the content ratio of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) [(A1) / (A2)] is less than 2.7. [2] The epoxy adhesive according to [1], characterized in that the rubber-modified epoxy resin (A3) contains at least one of a carboxy-terminated butadiene nitrile rubber-modified epoxy resin or a nitrile butadiene rubber-modified epoxy resin. [3] The epoxy adhesive according to [1] or [2], characterized in that the content of the rubber-modified epoxy resin (A3) is 5 to 45% by mass relative to the total epoxy resin (A). [4] The epoxy adhesive according to any one of [1] to [3], characterized in that the epoxy resin (A) contains an aromatic ring-containing epoxy resin (A4) that is solid at 25°C, excluding (A1) to (A3). [5] An epoxy adhesive according to any one of [1] to [4], characterized in that the content of epoxy resin that is solid at 25°C is 50% by mass or more relative to the total epoxy resin (A). [6] The epoxy adhesive according to any one of [1] to [5], characterized in that the curing agent (B) contains dicyandiamide. [7] Furthermore, the epoxy adhesive according to any one of [1] to [6] is characterized by containing polymer microparticles (C) having a core-shell structure. [8] An epoxy adhesive according to any one of [1] to [7], characterized in that it is solid at 25°C. [9] An epoxy adhesive according to any one of [1] to [8], characterized in that its viscosity at 60°C is 0.01 to 5000 Pa·s.

[10] An epoxy adhesive according to any one of [1] to [9], characterized in that it is used for bonding dissimilar materials.

[11] An adhesive sheet characterized by containing an epoxy adhesive as described in any of [1] to [9].

[12] An adhesive sheet for bonding dissimilar materials, characterized by containing the epoxy adhesive described in

[10] .

[13] An adhesive sheet having an adhesive layer containing an epoxy adhesive comprising an epoxy resin (A) and a curing agent (B), wherein the epoxy resin (A) comprises a bisphenol A type epoxy resin (A1), a bisphenol F type epoxy resin (A2), and a rubber-modified epoxy resin (A3), characterized in that the thickness of the adhesive layer is 0.1 to 2 mm.

[14] The adhesive sheet according to

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

[15] The adhesive sheet according to

[13] or

[14] , wherein a release film is provided on at least one surface of the adhesive layer. [Advantages of the Invention]

[0009] The epoxy-based adhesive of the present invention can cause cohesive failure without causing interfacial peeling in the adhesion of dissimilar materials while maintaining the adhesive strength. Therefore, an adhesive having good adhesiveness can be provided. [Modes for Carrying Out the Invention]

[0010] Hereinafter, the present invention will be described in detail. In the present specification, the term "epoxy resin" is generally used as a name for a category of thermosetting resins or a name for a category of chemical substances of compounds having one or more epoxy groups in the molecule, but in the present invention, it is used in the latter meaning. Further, in the present invention, any compound having one or more epoxy groups in the molecule is included in the definition of epoxy resin, not only polymers having a specific degree of polymerization but also monomers. In the present specification, the "molecular weight" means the number average molecular weight unless otherwise specified. Further, "room temperature" means 25°C, and "solid at 25°C" means that the softening point is 25°C or higher, or the viscosity at 25°C is 1000 Pa·s or higher. Also, when expressed as "X to Y" (X and Y are arbitrary numbers) in the present specification, unless otherwise specified, it includes the meaning of "X or more and Y or less" and also the meaning of "preferably larger than X" or "preferably smaller than Y". Also, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it also includes the intention of "preferably larger than X" or "preferably less than Y".

[0011] <Epoxy Resin (A)> The epoxy adhesive of the present invention uses epoxy resin (A) as a curing component, and contains bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3) as essential components of epoxy resin (A).

[0012] In the epoxy adhesive of the present invention, the content ratio of bisphenol A type epoxy resin (A1) to bisphenol F type epoxy resin (A2) [(A1) / (A2)] must be less than 2.7, preferably less than 2.5, particularly preferably less than 1.5, even more preferably less than 1.0, especially preferably less than 0.9, and more preferably less than 0.8. If the content ratio [(A1) / (A2)] is 2.7 or higher, the fracture mode becomes interfacial delamination, and the effects of the present invention are not fully realized, which is undesirable. The lower limit of this content ratio is not particularly limited, but for example, it is 0.01 or higher.

[0013] Examples of bisphenol A type epoxy resins (A1) used in the present invention include commercially available products such as EPON825, jER826, jER827, jER828, jER834, jER1001 (all manufactured by Mitsubishi Chemical Corporation), Epiclon 850 (manufactured by DIC Corporation), Epotote YD-128 (manufactured by Nippon Steel & Sumitomo Metal Chemical Corporation), DER-331, DER-332 (both manufactured by Dow Chemical Japan), Bakelite EPR154, Bakelite EPR162, Bakelite EPR172, Bakelite EPR173, Bakelite EPR174 (all manufactured by Bakelite AG Corporation). Among these, jER828 and jER1001 are preferred in terms of the elastic modulus of the cured epoxy adhesive and the glass transition temperature.

[0014] Bisphenol A type epoxy resin (A1) may be used alone or in combination of two or more types.

[0015] The number-average molecular weight of the bisphenol A type epoxy resin (A1) is preferably 200 to 100,000, particularly preferably 200 to 80,000, and even more preferably 200 to 60,000. If the number-average molecular weight is too low, the viscosity tends to decrease too much, reducing the workability of the adhesive. Conversely, if it is too high, the solubility in other monomers decreases, and the viscosity also tends to increase too much, reducing the workability. In this specification, "number-average molecular weight" is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0016] The epoxy equivalent of the bisphenol A type epoxy resin (A1) is preferably 20,000 or less, particularly preferably 10,000 or less, and even more preferably 6,000 or less. If the epoxy equivalent is too high, the solubility in other monomers decreases, which tends to reduce workability during compounding. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or higher. In this specification, "epoxy equivalent" refers to a value measured in accordance with JIS-K7236:2001.

[0017] The softening point of the bisphenol A type epoxy resin (A1) is preferably 160°C or lower, particularly preferably 140°C or lower, and even more preferably 120°C or lower. If the softening point is too high, the viscosity at room temperature after compounding increases, which tends to reduce the workability of the adhesive. The lower limit of the softening point is not particularly limited, but for example, it is -50°C or higher. In this specification, the "softening point" is a value measured in accordance with JIS-K7234:2008 (ring-sphere method).

[0018] Examples of bisphenol F type epoxy resins (A2) used in the present invention include commercially available jER806, jER807, jER4005P, jER4007P, jER4010P, jER1750 (all manufactured by Mitsubishi Chemical Corporation), Epiclon 830 (manufactured by DIC Corporation), Epotote YD-170, Epotote YD-175 (both manufactured by Nippon Steel & Sumitomo Metal Chemical Corporation), Bakelite EPR169 (manufactured by Bakelite AG), GY281, GY282, GY285 (all manufactured by Huntsman Advanced Materials Corporation). Among these, jER806, jER807, and jER4005P are preferred in terms of their excellent adhesion after curing of epoxy adhesives.

[0019] Bisphenol F type epoxy resin (A2) may be used alone or in combination of two or more types.

[0020] The number-average molecular weight of the bisphenol F type epoxy resin (A2) is preferably 200 to 100,000, particularly preferably 200 to 80,000, and even more preferably 200 to 60,000. If the number-average molecular weight is too low, the viscosity tends to decrease too much, reducing the workability of the adhesive. Conversely, if it is too high, the solubility in other monomers decreases, and the viscosity also tends to increase too much, reducing the workability.

[0021] The epoxy equivalent of the bisphenol F type epoxy resin (A2) is preferably 20,000 or less, particularly preferably 10,000 or less, and even more preferably 6,000 or less. If the epoxy equivalent is too high, the solubility in other monomers decreases, which tends to reduce workability during compounding. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or higher.

[0022] The softening point of the bisphenol F type epoxy resin (A2) is preferably 160°C or lower, particularly preferably 140°C or lower, and even more preferably 120°C or lower. If the softening point is too high, the viscosity at room temperature after compounding increases, which tends to reduce the workability of the adhesive. The lower limit of the softening point is not particularly limited, but for example, it is -50°C or higher.

[0023] In addition to the above, commercially available products containing a mixture of both bisphenol A type epoxy resin (A1) and bisphenol F type epoxy resin (A2) can also be used. Examples include jER4250 and jER4275 (both manufactured by Mitsubishi Chemical Corporation).

[0024] The rubber-modified epoxy resin (A3) used in the present invention 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).

[0025] Rubber-modified epoxy resin (A3) may be used alone or in combination of two or more types.

[0026] The epoxy resin used as a raw material for rubber-modified epoxy resin (A3) is not particularly limited, but 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, and orthocresol novolac-type epoxy resin.

[0027] The non-crosslinked liquid rubber used as a raw material for rubber-modified epoxy resin (A3) is preferably a conjugated diene homopolymer or a conjugated diene copolymer, particularly a diene / nitrile copolymer. The conjugated diene rubber is preferably butadiene or isoprene, with butadiene being particularly preferred. The preferred nitrile monomer is acrylonitrile. The preferred copolymer is butadiene-acrylonitrile copolymer.

[0028] The glass transition temperature (Tg) of such non-crosslinked liquid rubber is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 0°C or lower. The lower limit of this glass transition temperature is not particularly limited, but for example, it is -100°C or higher. In this specification, "glass transition temperature" is defined as the temperature at the inflection point of the DSC curve obtained by measuring the DSC curve of the sample using a differential scanning calorimeter.

[0029] Such non-crosslinked liquid rubbers preferably have an average of 1.5 to 2.5 epoxide-reactive end groups per molecule, more preferably an average of 1.8 to 2.2.

[0030] The number average molecular weight of such crosslinked liquid rubber is preferably 500 to 10,000, and more preferably 1,000 to 58,000.

[0031] As the rubber-modified epoxy resin (A3), carboxylate-terminated butadiene nitrile rubber (CTBN)-modified epoxy resin and nitrile butadiene rubber (NBR)-modified epoxy resin are preferred, with carboxylate-terminated butadiene nitrile rubber (CTBN)-modified epoxy resin being more preferred. Examples of commercially available products include ADEKA's Adeka Resin EPR series (EPR-1415-1, EPR-2000, EPR-2007, EPR-1630), Momentive's EPON Resin 58005 and EPON Resin 58006, and CVC's Hypox series (Hypox RA 840, Hypox RA 1340, Hypox RF 1341). Among these, ADEKA's Adeka Resin EPR series is preferred due to its superior adhesion and elastic modulus after curing, with EPR-1630 being more preferred.

[0032] The number-average molecular weight of the rubber-modified epoxy resin (A3) is preferably 200 to 200,000, particularly preferably 200 to 100,000, and even more preferably 200 to 80,000. If the number-average molecular weight is too low, the viscosity tends to decrease too much, reducing the workability of the adhesive. Conversely, if it is too high, the solubility in other monomers decreases, and the viscosity also tends to increase too much, reducing the workability.

[0033] The epoxy equivalent of the rubber-modified epoxy resin (A3) is preferably 10,000 or less, particularly preferably 7,000 or less, and even more preferably 5,000 or less. If the epoxy equivalent is too high, the flexible component will not disperse in the cured product, causing stress to concentrate in that area when stress occurs, which tends to reduce the adhesive strength. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or higher.

[0034] The softening point of the rubber-modified epoxy resin (A3) is preferably 200°C or lower, particularly preferably 180°C or lower, and even more preferably 160°C or lower. If the softening point is too high, the viscosity at room temperature after compounding increases, which tends to reduce the workability of the adhesive. The lower limit of the softening point is not particularly limited, but for example, it is -50°C or higher.

[0035] In the present invention, it is preferable to use an aromatic ring-containing epoxy resin (A4) that is solid at room temperature (excluding bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3)) in terms of low water absorption, the elastic modulus of the cured product, and the glass transition temperature. Examples include phenol aralkyl type epoxy resin (commercially available product: "YX7700" manufactured by Mitsubishi Chemical Corporation) and biphenyl type epoxy resin (commercially available product: "YX4000" manufactured by Mitsubishi Chemical Corporation).

[0036] Aromatic ring-containing epoxy resin (A4), which is solid at room temperature, may be used alone or in combination of two or more types.

[0037] The number-average molecular weight of the aromatic ring-containing epoxy resin (A4), which is solid at room temperature, is preferably 200 to 100,000, particularly preferably 200 to 80,000, and even more preferably 200 to 60,000. If the number-average molecular weight is too low, the viscosity tends to decrease too much, reducing the workability of the adhesive. Conversely, if it is too high, the solubility in other monomers decreases, and the viscosity also tends to increase too much, reducing the workability.

[0038] The epoxy equivalent of the aromatic ring-containing epoxy resin (A4), which is solid at room temperature, is preferably 10,000 or less, particularly preferably 7,000 or less, and even more preferably 5,000 or less. If the epoxy equivalent is too high, the solubility in other monomers decreases, which tends to reduce workability during compounding. The lower limit of the epoxy equivalent is not particularly limited, but for example, it is 50 or higher.

[0039] The softening point of the aromatic ring-containing epoxy resin (A4), which is solid at room temperature, is preferably 160°C or lower, particularly preferably 140°C or lower, and even more preferably 120°C or lower. If the softening point is too high, the viscosity at room temperature after compounding tends to increase, and the workability of the adhesive tends to decrease. The lower limit of the softening point is not particularly limited, but for example, it is -50°C or higher.

[0040] The epoxy resin (A) content used in the present invention is preferably 30 to 100% by mass, more preferably 40 to 100% by mass, and particularly preferably 50 to 100% by mass, relative to the total epoxy adhesive.

[0041] The content of bisphenol A type epoxy resin (A1) is preferably 0.01 to 70% by mass, more preferably 0.1 to 60% by mass, and particularly preferably 1 to 50% by mass, relative to the total epoxy resin (A) (the total content of all epoxy resins (A) contained in the epoxy adhesive).

[0042] The content of bisphenol F type epoxy resin (A2) is preferably 1 to 70% by mass, more preferably 5 to 60% by mass, and particularly preferably 10 to 50% by mass, relative to the total epoxy resin (A).

[0043] Furthermore, for compositions containing both bisphenol A type epoxy resin (A1) and bisphenol F type epoxy resin (A2), the content is calculated by dividing the composition by mass ratio. For example, if a composition containing bisphenol A type epoxy (A1) and bisphenol F type epoxy (A2) in a 1:1 ratio has a total content of 10% by mass, the calculation is performed by assuming that (A1) is 5% by mass and (A2) is 5% by mass.

[0044] The content of rubber-modified epoxy resin (A3) is preferably 0.01 to 60% by mass, more preferably 1 to 50% by mass, and particularly preferably 5 to 40% by mass, relative to the total epoxy resin (A).

[0045] Furthermore, the content of the rubber-modified epoxy resin (A3) is preferably 0.01 to 55% by mass, more preferably 1 to 45% by mass, and particularly preferably 5 to 40% by mass, relative to the total curing components other than the curing agent (B).

[0046] The content of the aromatic ring-containing epoxy resin (A4), which is solid at room temperature, is preferably 0 to 80% by mass, more preferably 1 to 70% by mass, and particularly preferably 5 to 60% by mass, relative to the total epoxy resin (A).

[0047] The content ratio of bisphenol A type epoxy resin (A1) to rubber-modified epoxy resin (A3) [(A1) / (A3)] is preferably less than 3.0, particularly preferably less than 2.5, even more preferably less than 2.0, and especially preferably less than 1.5. If this content ratio [(A1) / (A3)] is too high, the failure mode tends to be interfacial delamination, which is undesirable. The lower limit of this content ratio is not particularly limited, but for example, it is 0.01 or higher.

[0048] Furthermore, in the present invention, it is also preferable that the content of bisphenol A type epoxy resin (A1) is less than the content of bisphenol F type epoxy resin (A2), and that the content of bisphenol A type epoxy resin (A1) is less than 1.5 times the content of rubber-modified epoxy resin (A3).

[0049] The epoxy adhesive of the present invention may further contain epoxy resins other than (A1) to (A4). Specific examples include various epoxy resins such as alcohol-type epoxy resins, naphthalene-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, phenol aralkyl-type epoxy resins, biphenyl-type epoxy resins, triphenylmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, polyfunctional phenol-type epoxy resins, and aliphatic epoxy resins.

[0050] The epoxy resin (A) used in the present invention preferably contains 50% by mass or more of epoxy resin that is solid at room temperature relative to the total epoxy resin (A), particularly preferably 55% by mass or more, and even more preferably 60% by mass or more. The upper limit of the content of such epoxy resin that is solid at room temperature is not particularly limited, but for example, it is 100% by mass or less.

[0051] <Hardening agent (B)> Examples of curing agents (B) used in the present invention include amines, acid anhydrides (carboxylic acid anhydrides), phenols (novolac resins, etc.), mercaptans, Lewis acid amine complexes, onium salts, and imidazoles. Specific examples include the curing agents described in Chapter 3 of "General Overview of Epoxy Resins, Volume 1 (edited by the Epoxy Resin Technology Association, first edition, published November 2003)" and Chapter 2 of "General Overview of Epoxy Resins, Recent Developments I (edited by the Epoxy Resin Technology Association, first edition, published March 2009)." Of these, amines are preferred from the viewpoint of adhesion.

[0052] The hardening agent (B) may be used alone, or two or more may be used in combination.

[0053] Examples of the above-mentioned amines include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, and their isomers and modified forms. Among these, dicyandiamide is particularly preferred due to its excellent pot life of the matrix resin composition.

[0054] The content of the curing agent (B) used in the present invention is preferably 0.01 to 30% by mass, more preferably 0.1 to 25% by mass, and particularly preferably 1 to 20% by mass, relative to the total epoxy resin (A).

[0055] <Polymer microparticles having a core-shell structure (C)> The epoxy adhesive of the present invention may contain polymer microparticles (C) having a core-shell structure. Polymer microparticles (C) having a core-shell structure refer to known core-shell polymers, that is, polymer particles in which the molecular structure differs between the central part (core) and the outer part (shell).

[0056] Examples of components constituting the core portion of polymer microparticles (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), and ethylene propylene rubber (EPR). Among these, butadiene rubber is preferred.

[0057] Preferably, the components constituting the shell portion of polymer microparticles (C) having a core-shell structure are graft polymerized onto the core portion and covalently bonded to the polymer constituting the core component.

[0058] Examples of components constituting such a shell include acrylic acid ester monomers, methacrylic acid ester monomers, and aromatic vinyl monomers.

[0059] Examples of polymer microparticles (C) having a core-shell structure include commercially available KANE-ACE series products from Kaneka Corporation (B-11A, B-22, B-561, FM-21, M-701, M-711, M-300, FM-40, M-210, Pa-20, PA101, MR-01, MX-153, MX257, MX154, MX-960, MX-136, MX-965, MX-217, MX227M75, MX-334M75, MX-416, MX-451, etc.) and Metabrane products from Mitsubishi Chemical Corporation (Metabren C, Metabrane E, Metabrane W, Metabrane S, etc.).

[0060] Among these, those with a rubber core are preferred from the viewpoint of flexibility and adhesion. Furthermore, polymer fine particles (C) may be used as particulate matter or dispersed in other solutions or resins, but from the viewpoint of uniform dispersion in other resins, those dispersed in epoxy resins are more preferred, specifically MX-153, MX-154, MX-136, and MX-267.

[0061] Polymer microparticles (C) having a core-shell structure may be used alone or in combination of two or more types.

[0062] The primary particle size of the polymer fine particles (C) having a core-shell structure used in the present invention is preferably 10 to 100,000 nm, more preferably 15 to 50,000 nm, and particularly preferably 20 to 10,000 nm, based on the elastic modulus, scalability, and shear strength of the cured product obtained from the epoxy resin. The primary particle size refers to the volume-average particle size of the primary particles, and can be measured using, for example, a NanoTrac particle size distribution analyzer (manufactured by Nikkiso Co., Ltd.).

[0063] Furthermore, with respect to polymer microparticles (C) having a core-shell structure, when using a dispersion of bisphenol A type epoxy (A1) or bisphenol F type epoxy (A2), the content ratios of (A1) / (A2) and (A1) / (A3) shall be calculated by adding the (A1) and (A2) used for dispersion.

[0064] The content of polymer fine particles (C) having a core-shell structure is preferably 0 to 50% by mass, more preferably 1 to 40% by mass, and particularly preferably 2 to 30% by mass, relative to the total epoxy adhesive excluding the curing agent (B).

[0065] The epoxy adhesive of the present invention may contain a curing accelerator (D) from the viewpoint of enhancing the curing activity of the curing agent (B). For example, since dicyandiamide and the like among the curing agents (B) have a high curing temperature when used alone, a curing accelerator (D) can be used to enhance the curing activity of dicyandiamide and the like. Examples of curing accelerators for dicyandiamide include urea derivatives such as 3-phenyl-1,1-dimethylurea, 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), and 2,4-bis(3,3-dimethylureido)toluene, as well as imidazole derivatives. Among these, urea derivatives are preferred, and 2,4-diamino-6-(2-methylimidazolyl-(1))-ethyl-s-triazine is more preferred.

[0066] The content of the curing accelerator (D) used in the present invention is preferably 0.01 to 30% by mass, more preferably 0.05 to 25% by mass, and particularly preferably 0.1 to 20% by mass, relative to the total amount of the curing agent (B).

[0067] <Epoxy adhesive> The epoxy adhesive of the present invention contains three components as epoxy resin (A): 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 component, and more preferably contains polymer fine particles (C) having a core-shell structure and a curing accelerator (D). Furthermore, in the present invention, other compounding components can be used as needed, within a range that does not impair the effects of the present invention (for example, within a content of 5% by mass or less relative to the total epoxy adhesive). Examples of other compounding components include dehydrating agents such as calcium oxide, colorants such as pigments and dyes, extender pigments, ultraviolet absorbers, antioxidants, stabilizers (gelling inhibitors), plasticizers, leveling agents, defoaming agents, silane coupling agents, antistatic agents, flame retardants, lubricants, viscosity reducers, low shrinkage agents, organic fillers, inorganic fillers, thermoplastic resins, drying agents, dispersants, and the like.

[0068] In bonding dissimilar materials, the epoxy adhesive of the present invention is preferably solid at room temperature from the viewpoint of preventing dripping during bonding. On the other hand, from the viewpoint of smooth adhesion 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 of this softening point is not particularly limited, but for example, it is 30°C or higher.

[0069] The viscosity of the adhesive of the present invention at 60°C and 1 atm is preferably 0.01 to 20,000 Pa·s, particularly preferably 0.01 to 10,000 Pa·s, even more preferably 0.01 to 8,000 Pa·s, and more preferably 0.01 to 5,000 Pa·s. Alternatively, the viscosity may be preferably 0.05 to 4,000 Pa·s, 0.1 to 3,000 Pa·s, 1 to 1,000 Pa·s, or 10 to 800 Pa·s. If the viscosity is too high or too low, the applicability to the substrate when used as an adhesive tends to decrease. The viscosity was measured at 60°C using a Type B rotational viscometer (Brookfield viscometer) in accordance with JIS Z 8803.

[0070] The epoxy adhesive of the present invention is suitably used for bonding dissimilar materials. While there are no particular limitations on the combination of dissimilar materials, examples include two combinations selected from various materials such as hot-rolled steel sheets, cold-rolled steel sheets, high-tensile steel sheets, stainless steel sheets, plated steel sheets (galvanized steel sheets, zinc-nickel steel sheets, etc.), aluminum sheets, aluminum alloy sheets (aluminum-manganese alloy sheets, aluminum-magnesium alloy sheets, etc.), fiber-reinforced plastic (FRP) sheets such as carbon fiber and glass fiber, and carbon fiber reinforced plastic (CFRP). Among these, the epoxy adhesive of the present invention is particularly suitable for bonding dissimilar metals and CFRP. Among dissimilar metals, it is especially preferable to use it for bonding metals, primarily iron and aluminum.

[0071] <Method for manufacturing epoxy adhesives> The epoxy adhesive of the present invention can be manufactured by mixing its components.

[0072] The preferred method for mixing the above components is to heat the mixture to liquefy some of the epoxy resins and liquefiable components before mixing. 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. If the mixing temperature is below the lower limit, the mixture tends to solidify due to the solidification of each component, resulting in poor mixing. If the temperature is above the upper limit, the mixture tends to polymerize and gel during mixing.

[0073] The mixing time is usually 1 minute or more, preferably 10 minutes or more, and particularly preferably 20 minutes or more, and usually 24 hours or less, preferably 18 hours or less, and particularly preferably 12 hours or less. If the mixing time falls below the lower limit, uniform mixing tends not to occur, and if it exceeds the upper limit, the mixture tends to polymerize and gel during mixing.

[0074] The above components can be mixed using various methods that apply shear force, such as stirring, shaking, and kneading, which are commonly used in the mixing of epoxy adhesives. The mixing method is selected based on various factors, including the physical properties of the adhesive and the production volume. The resulting epoxy adhesive may be in a uniform state or a non-uniform state with dispersed particles. This state is selected depending on the intended use of the adhesive.

[0075] The epoxy adhesive of the present invention is preferably a one-component adhesive from the viewpoint of ease of handling.

[0076] The epoxy adhesive of the present invention can be used to obtain a laminate by applying the adhesive to one or both of a plurality of members having different coefficients of thermal expansion, then sandwiching the adhesive between the dissimilar members and bonding them together, and finally curing the adhesive.

[0077] There are no particular restrictions on the curing conditions, but for example, when using a one-component adhesive, heating to a temperature of 80°C or higher, preferably 130°C or higher, and more preferably 150°C or higher allows curing to be performed preferably within 60 minutes, more preferably within 30 minutes, to obtain a laminate with dissimilar members joined together.

[0078] <Adhesive Sheet> The epoxy adhesive of the present invention can be suitably used as an adhesive sheet containing the epoxy adhesive, and among these, an adhesive sheet for bonding dissimilar materials is particularly preferred. The adhesive sheet containing the epoxy adhesive of the present invention may, for example, have an adhesive layer obtained using the epoxy adhesive on a base film, or it may have an adhesive layer obtained by impregnating a support with the epoxy adhesive.

[0079] When providing an adhesive layer containing the epoxy adhesive on a base film, it is preferable to use a release film such as silicone or melamine as the base film. Specifically, release-treated PET film, polyethylene film, polypropylene film, fluorine film, polyimide film, etc., can be used.

[0080] Furthermore, when impregnating the support with the epoxy adhesive, the support can be, for example, a nonwoven fabric or a porous material, with nonwoven fabric being preferred. The density of the support material is set to 0.05 g / cm³ from the viewpoint of suppressing resin flow under pressure when bonding multiple components, improving resin retention in sheet adhesives, and enhancing adhesion due to the rigidity of the adhesive layer. 3 The above is preferable, and 0.08 g / cm³ 3 The above is more preferable, 0.1 g / cm³ 3 The above is even more preferable. Furthermore, from the viewpoint of improving resin impregnation into the support in adhesive sheets, improving lightness, and improving interfacial adhesion, 1.0 g / cm³ 3 Preferably, it is 0.9 g / cm³. 3 It is more preferable that the following is the case: 0.8 g / cm³ 3 The following is even more preferable:

[0081] The thickness of the adhesive layer in the adhesive sheet is preferably 0.1 to 2.0 mm. By having the thickness of the adhesive layer within the above numerical range, it is possible to reduce warping while maintaining good adhesion when bonding multiple members with different coefficients of thermal expansion. In particular, 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. Furthermore, since the tensile shear bonding strength after bonding improves as the thickness of the adhesive layer decreases, 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.

[0082] The adhesive sheet can be obtained by forming an epoxy adhesive into a sheet. As a method for forming the material into a sheet, one method involves laminating or coating the epoxy adhesive onto a base film to obtain a laminate of base film / epoxy adhesive / base film. Specifically, this can be done using sheet forming equipment such as extrusion lamination with T-dies, calender rolls, or double belt presses, or by comma coating, gravure coating, reverse coating, knife coating, dip coating, spray coating, air knife coating, spin coating, roll coating, print coating, dip coating, slide coating, curtain coating, die coating, casting, bar coating, or extrusion coating.

[0083] During the sheet molding process described above, an impregnation step may be performed in which the epoxy adhesive is impregnated into the support material. The impregnation method for the epoxy adhesive in the impregnation step can be any known method. Examples of such impregnation methods include a lamination method in which the epoxy adhesive applied to the base film in the sheet molding step is laminated with a support so that the structure is base film / epoxy adhesive / support / epoxy adhesive / base film, and then impregnated using a vacuum laminator, calender roll, double belt press, etc., or a dip-nip method, kiss coat method, spray method, curtain coat method, etc., in which the epoxy adhesive is directly impregnated into the support. The thickness of the support and the amount of epoxy adhesive impregnated into the support are preferably adjusted so that the thickness of the adhesive layer is 0.1 to 2.0 mm.

[0084] Laminates obtained using the epoxy adhesive of the present invention can be used as structural members (panel parts, frame parts, undercarriage parts, etc.) of transportation equipment such as vehicles, aircraft, and ships. They are particularly preferably used as structural panels, and are especially useful as structural panels for vehicles. [Examples]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Also, "parts" and "%" refer to mass.

[0086] First, the constituent components of the epoxy resin adhesive compositions to be used in the examples and comparative examples were prepared. <Epoxy resin (A)> • Epoxy resin 1: Bisphenol A type epoxy resin (A1-1) (Mitsubishi Chemical Corporation "jER1001", solid at room temperature) • Epoxy resin 2: Bisphenol F type epoxy resin (A2-1) (Mitsubishi Chemical Corporation "jER807", liquid at room temperature) • Epoxy resin 3: Bisphenol F type epoxy resin (A2-2) (Mitsubishi Chemical Corporation "jER4005P", solid at room temperature) • Epoxy resin 4: Rubber-modified (CTBN-modified) epoxy resin (A3) (solid at room temperature) dispersed with 15% bisphenol A type epoxy resin (A1-2) (liquid at room temperature) (ADEKA "EPR-1630") [Rubber-modified epoxy resin (A3):Bisphenol A type epoxy resin (A1-2) = 85:15] • Epoxy resin 5: Phenolic aralkyl epoxy resin (A4-1) (Mitsubishi Chemical Corporation "YX7700", solid at room temperature) • Epoxy resin 6: Biphenyl-type epoxy resin (A4-2) (Mitsubishi Chemical Corporation "YX4000", solid at room temperature)

[0087] <Hardening agent (B)> • Hardener (B-1): Dicyandiamide (DUCY7, manufactured by Mitsubishi Chemical Corporation)

[0088] <Polymer microparticles having a core-shell structure (C)> • Polymer microparticles with a core-shell structure 1: Bisphenol A type epoxy resin (A1-3) (liquid at room temperature) 60% dispersion (Kaneka Corporation "Kane Ace MX-154") [Polymer microparticles with a core-shell structure (C-1): Bisphenol A type epoxy resin (A1-3) = 40:60] • Polymer microparticles with a core-shell structure 2: Core-shell rubber (C-2) dispersed with 3% bisphenol A type epoxy resin (A1-4) (liquid at room temperature) and 59% bisphenol F type epoxy resin (A2-3) (liquid at room temperature) (KANE-ACE MX-267, manufactured by Kaneka Corporation) [Polymer microparticles with a core-shell structure (C-2): Bisphenol A type epoxy resin (A1-4): Bisphenol F type epoxy resin (A2-3) = 38:3:59]

[0089] <Curing accelerator (D)> • Curing accelerator (D-1): 2,4-diamino-6-(2-methylimidazolyl-(1))-ethyl-s-triazine (manufactured by Shikoku Chemicals Co., Ltd., "2MZA-PW")

[0090] <Preparation of epoxy adhesives> [Example 1] 20 parts epoxy resin 2, 10 parts epoxy resin 3, 20 parts epoxy resin 4, 40 parts epoxy resin 5, and 10 parts polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts curing agent (B-1) and 2 parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an adhesive. The adhesive of Example 1 was solid at room temperature. The viscosity at 60°C was 160 Pa·s.

[0091] [Example 2] 10 parts epoxy resin 2, 10 parts epoxy resin 3, 20 parts epoxy resin 4, 40 parts epoxy resin 5, and 20 parts polymer fine particles 2 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts curing agent (B-1) and 2 parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain the adhesive. The adhesive of Example 2 was solid at room temperature.

[0092] [Example 3] 10 parts epoxy resin 2, 10 parts epoxy resin 3, 20 parts epoxy resin 4, 40 parts epoxy resin 6, and 20 parts polymer fine particles 2 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts curing agent (B-1) and 2 parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain the adhesive. The adhesive of Example 3 was solid at room temperature.

[0093] [Example 4] Ten parts of epoxy resin 2, ten parts of epoxy resin 3, forty parts of epoxy resin 4, thirty parts of epoxy resin 5, and ten parts of polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, eight parts of curing agent (B-1) and two parts of curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain the adhesive. The adhesive of Example 4 was solid at room temperature.

[0094] [Example 5] 10 parts epoxy resin 2, 10 parts epoxy resin 3, 20 parts epoxy resin 4, 40 parts epoxy resin 5, and 20 parts polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts curing agent (B-1) and 2 parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain the adhesive. The adhesive of Example 5 was solid at room temperature.

[0095] [Example 6] 17 parts epoxy resin 2, 25 parts epoxy resin 4, 38 parts epoxy resin 5, and 20 parts polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts curing agent (B-1) and 2 parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an epoxy resin composition for adhesive. The adhesive of Example 6 was solid at room temperature.

[0096] [Example 7] 15 parts of epoxy resin 1, 5 parts of epoxy resin 2, 25 parts of epoxy resin 4, 40 parts of epoxy resin 5, and 15 parts of polymer fine particles 2 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an epoxy resin composition for adhesive. The adhesive of Example 7 was solid at room temperature.

[0097] [Example 8] 20 parts of epoxy resin 1, 20 parts of epoxy resin 2, 20 parts of epoxy resin 4, 20 parts of epoxy resin 5, and 20 parts of polymer fine particles 2 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an epoxy resin composition for adhesives. The adhesive of Example 8 was solid at room temperature.

[0098] [Example 9] 25 parts of epoxy resin 1, 20 parts of epoxy resin 2, 15 parts of epoxy resin 4, 20 parts of epoxy resin 5, and 20 parts of polymer fine particles 2 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, 8 parts of curing agent (B-1) and 2 parts of curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an epoxy resin composition for adhesive. The adhesive of Example 9 was solid at room temperature.

[0099] [Comparative Example 1] Five parts epoxy resin 2, twenty parts epoxy resin 4, fifty-five parts epoxy resin 5, and twenty parts polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, eight parts curing agent (B-1) and two parts curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an adhesive. The adhesive of Comparative Example 1 was solid at room temperature.

[0100] [Comparative Example 2] Ten parts of epoxy resin 3, twenty parts of epoxy resin 4, thirty parts of epoxy resin 5, and forty parts of polymer fine particles 1 having a core-shell structure were mixed and stirred at 90°C until homogeneous. The mixture was then placed in a 70°C constant temperature bath to bring the resin temperature to 70°C. After that, eight parts of curing agent (B-1) and two parts of curing accelerator (D-1) were added and stirred until uniformly dispersed to obtain an adhesive. The adhesive of Comparative Example 2 was solid at room temperature.

[0101] Table 1 shows the composition of the adhesives obtained in Examples 1-9 and Comparative Examples 1-2. The content values ​​in Table 1 are rounded to one decimal place, and the content ratios [(A1) / (A2)] and [(A1) / (A3)] shown in Table 1 are values ​​calculated based on the content values ​​listed in Table 1 and rounded to three decimal places.

[0102] The adhesives obtained in Examples 1-9 and Comparative Examples 1-2 were used to perform the following shear adhesion measurements. The results are shown in Table 1. <Shear Adhesion Measurement> The shear adhesion strength was measured using Al (aluminum) test specimens ("Standard Test Plate Al5052P" manufactured by Nippon Test Panel Co., Ltd.) and Fe (SPCC steel sheet) test specimens ("Standard Test Plate SPCC-SB" manufactured by Nippon Test Panel Co., Ltd.) by the following method. The adhesive obtained above was applied to the surface of an Fe test specimen (12.5 mm x 25 mm x 1.6 mm thick) to a thickness of approximately 0.8 mm, and the thickness was further adjusted using a spacer. Then, an Al test specimen (12.5 mm x 25 mm x 1.6 mm thick) was placed on top, and the two specimens were pressed together using two binder clips (Lion Corporation "No. 107") to ensure a uniform Al / Fe thickness. After pressing, the samples were cured by heating in a hot air drying oven at 130°C for 20 minutes to obtain samples for measurement. After cooling to room temperature (25°C), the tensile shear force of the measurement sample was measured using a tensile testing machine (Shimadzu Corporation "Autograph AG-X") in accordance with JIS K6850. The test speed was 5 mm / min, and the test environment was 23°C and 50% RH.

[0103] (Adhesion strength evaluation criteria) The adhesive strength was evaluated based on tensile shear force and failure mode. The results of the tensile shear test were evaluated using the value of the maximum breaking point of the tensile testing machine. A score of ○ (Very good) was given if the tensile shear force was "15 MPa or more" and the failure mode was "cohesive failure," a score of △ (Good) was given if the tensile shear force was "15 MPa or more" and the failure mode was "partial cohesive failure," and a score of × (Poor) was given if the tensile shear force was "15 MPa or less" or the failure mode was "interfacial delamination." The failure mode was determined by visually and tactilely inspecting the bonded surfaces of the Al and Fe test pieces after delamination. If the hardened adhesive covered 60% or more of the area of ​​both test plates relative to the bonded area, it was determined to be cohesive failure. If the adhesive covered 30% or more but less than 60% of the area of ​​either test plate, it was determined to be partial cohesive failure. If the adhesive covered less than 30% of the area of ​​either test plate, it was determined to be interfacial delamination.

[0104] <Evaluation of suitability for sheet formatting> The suitability of the adhesives obtained in Examples 1-9 and Comparative Examples 1-2 for sheet formation was confirmed by the following method. The results are shown in Table 1. The adhesives obtained in Examples 1-9 and Comparative Examples 1-2 were placed in mayonnaise jars (size: No. 3K). The adhesive was placed to a height of 1-3 cm from the bottom of the mayonnaise jar. Then, the mayonnaise jar containing the adhesive was turned upside down with the opening facing downwards, held for 30 seconds, and then returned to its original position. If the adhesive dripped to a height of 1.2 times or more the height of the adhesive, it was judged to have dripped, and the suitability for sheet formation was evaluated as × (Poor). On the other hand, if the drip height was less than 1.2 times the height of the adhesive, it was judged that there had been no dripping, and the suitability for sheet formation was evaluated as ○ (Good).

[0105] [Table 1]

[0106] As shown in Table 1, the adhesive layers obtained by curing the adhesives of Examples 1 to 9 have a tensile shear force of 15 MPa or more, and the failure mode is cohesive failure or partial cohesive failure. This is thought to be because, by reducing the content ratio of bisphenol A type epoxy resin (A1) to bisphenol F type epoxy resin (A2) to a specific amount or less, the rigid bisphenol A type skeleton of (A1) is reduced and the flexible bisphenol F type skeleton of (A2) is increased, improving adhesion and flexibility, and thus maintaining a high shear force while the failure mode becomes cohesive failure or partial cohesive failure. On the other hand, the adhesive layers obtained by curing the adhesives of Comparative Examples 1 and 2 were thought to have poor flexibility and adhesion, resulting in interfacial delamination, because the amount of bisphenol A type epoxy resin (A1) added was large relative to the bisphenol F type epoxy resin (A2).

[0107] <Preparation of adhesive sheets> [Example 10] The adhesive obtained in Example 1 was applied to a PET film treated with silicone release agent as a base film, and then placed on a glass fiber nonwoven fabric (density 0.16 g / cm³). 3 It was impregnated with (0.77 mm thick). Another base film was inserted from the other side and an adhesive sheet (adhesive sheet thickness 0.8 mm) was made using a laminator.

[0108] Using the adhesive sheet obtained above, the tensile shear force was measured in accordance with the same method as described above. The adhesive sheet using the adhesive of the present invention exhibited excellent tensile shear adhesive strength.

[0109] While the above embodiments illustrate specific forms of the present invention, these embodiments are merely illustrative and should not be interpreted restrictively. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention. [Industrial applicability]

[0110] The epoxy resin composition for adhesives of the present invention can be used for structural members (frames, panel parts, etc.) of transportation equipment such as vehicles, aircraft, and ships, as well as for building materials and other components, and is particularly useful for structural members of vehicles.

Claims

1. An epoxy adhesive comprising an epoxy resin (A) and a curing agent (B), The epoxy resin (A) contains bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3). The rubber-modified epoxy resin (A3) is at least one of a carboxyl-terminated butadiene nitrile rubber-modified epoxy resin and a nitrile butadiene rubber-modified epoxy resin. The content of the bisphenol F type epoxy resin (A2) is 10 to 70% by mass relative to the total epoxy resin (A). The content ratio of the bisphenol A type epoxy resin (A1) to the bisphenol F type epoxy resin (A2) [(A1) / (A2)] is less than 2.

7. An epoxy adhesive characterized in that the content ratio of the bisphenol A type epoxy resin (A1) to the rubber-modified epoxy resin (A3) [(A1) / (A3)] is less than 3.

0.

2. The epoxy adhesive according to claim 1, characterized in that the content of the rubber-modified epoxy resin (A3) is 5 to 45% by mass relative to the total epoxy resin (A).

3. The epoxy adhesive according to claim 1 or 2, characterized in that the epoxy resin (A) contains an aromatic ring-containing epoxy resin (A4) that is solid at 25°C, excluding (A1) to (A3) above.

4. The epoxy adhesive according to any one of claims 1 to 3, characterized in that the content of epoxy resin that is solid at 25°C is 50% by mass or more relative to the total epoxy resin (A).

5. The epoxy adhesive according to any one of claims 1 to 4, characterized in that the curing agent (B) contains dicyandiamide.

6. Furthermore, the epoxy adhesive according to any one of claims 1 to 5 is characterized by containing polymer microparticles (C) having a core-shell structure.

7. An epoxy adhesive according to any one of claims 1 to 6, characterized in that it is solid at 25°C.

8. The epoxy adhesive according to any one of claims 1 to 7, characterized in that its viscosity at 60°C is 0.01 to 5000 Pa·s.

9. An epoxy adhesive according to any one of claims 1 to 8, characterized in that it is used for bonding dissimilar materials.

10. An adhesive sheet characterized by containing an epoxy adhesive according to any one of claims 1 to 8.

11. An adhesive sheet for bonding dissimilar materials, characterized by containing the epoxy adhesive described in claim 9.

12. The epoxy resin (A) comprises an epoxy resin (A) and a curing agent (B), wherein the epoxy resin (A) includes bisphenol A type epoxy resin (A1), bisphenol F type epoxy resin (A2), and rubber-modified epoxy resin (A3). The rubber-modified epoxy resin (A3) is at least one of a carboxyl-terminated butadiene nitrile rubber-modified epoxy resin and a nitrile butadiene rubber-modified epoxy resin. An adhesive sheet having an adhesive layer containing an epoxy adhesive in which the content ratio of the bisphenol A type epoxy resin (A1) to the rubber-modified epoxy resin (A3) [(A1) / (A3)] is less than 3.0, characterized in that the thickness of the adhesive layer is 0.1 to 2 mm.

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

14. The adhesive sheet according to claim 12 or 13, characterized in that it has a release film on at least one surface of the adhesive layer.

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