Epoxy resin composition and cured product thereof

Abstract

Provided is an epoxy resin composition comprising an epoxy resin (A), a curing agent (B) and an imidazole adduct type curing accelerator (C), wherein the curing agent (B) comprises a 1 represents a hydrogen atom, a halogen atom, a methoxy group or a hydrocarbon group having 1 to 12 carbon atoms. ] The compound (B-1) represented by formula (B-2) [R 2 represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group. ] The compound (B-2) shown in FIG, wherein the content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition and a cured product thereof. Background Art

[0002] Epoxy resins are used in a variety of applications, including fiber-reinforced materials, electronic components, adhesives, and coatings, due to the excellent heat resistance, strength, chemical resistance, and adhesion of their cured products.

[0003] In various applications, a composition containing an epoxy resin (hereinafter referred to as an "epoxy resin composition") generally contains a curing agent for curing the composition, and sometimes further contains a curing accelerator [for example, Japanese Patent Application Publication No. 2015-083634 (Patent Document 1) and Japanese Patent Application Publication No. 2013-032510 (Patent Document 2)].

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-083634

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-032510 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Epoxy resin compositions require properties corresponding to their intended use. Typically, epoxy resin compositions require low viscosity and a long pot life from the perspective of workability. Furthermore, cured products of epoxy resin compositions require high heat resistance and sometimes tensile properties, depending on their intended use.

[0010] An object of the present invention is to provide an epoxy resin composition having low viscosity and a long pot life and capable of providing a cured product exhibiting good heat resistance, and a cured product thereof.

[0011] Means for solving problems

[0012] The present invention provides the following epoxy resin compositions and cured products.

[0013] [1] An epoxy resin composition comprising an epoxy resin (A), a curing agent (B) and an imidazole adduct type curing accelerator (C),

[0014] The curing agent (B) comprises a compound (B-1) represented by the following formula (B-1) and a compound (B-2) represented by the following formula (B-2).

[0015]

[0016] [Where R 1 represents a hydrogen atom, a halogen atom, a methoxy group, or a hydrocarbon group having 1 to 12 carbon atoms.]

[0017]

[0018] [Where R 2 represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group.]

[0019] The content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

[0020] [2] The epoxy resin composition according to [1], wherein the molar ratio of the phenolic hydroxyl group content to the epoxy group content in the epoxy resin composition is 0.20 or more and 0.75 or less.

[0021] [3] The epoxy resin composition according to [1] or [2], wherein the content of the compound (B-2) is 2.5 parts by mass or more and 4 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0022] [4] The epoxy resin composition according to any one of [1] to [3], wherein the ratio of the content of the compound (B-2) to the content of the compound (B-1) is 0.20 to 0.95 in terms of mass ratio.

[0023] [5] The epoxy resin composition according to any one of [1] to [4], wherein the epoxy resin (A) comprises an epoxy resin having two epoxy groups in the molecule.

[0024] [6] The epoxy resin composition according to any one of [1] to [5], further comprising a Lewis acid compound (D) having a boron atom or an aluminum atom.

[0025] [7] A cured product, which is a cured product of the epoxy resin composition according to any one of [1] to [6].

[0026] [8] A prepreg comprising the epoxy resin composition according to any one of [1] to [6] and fibers.

[0027] [9] A composition comprising a cured product of the epoxy resin composition according to any one of [1] to [6] and fibers.

[0028] Effects of the Invention

[0029] An epoxy resin composition and a cured product thereof can be provided, wherein the epoxy resin composition has low viscosity and a long pot life and can provide a cured product exhibiting good heat resistance. DETAILED DESCRIPTION

[0030] <Epoxy resin composition>

[0031] The epoxy resin composition of the present invention (hereinafter also referred to as “epoxy resin composition”) contains the following components:

[0032] Epoxy resin (A);

[0033] a curing agent (B); and

[0034] Imidazole adduct type curing accelerator (C).

[0035] The curing agent (B) contains a compound represented by the above formula (B-1) (hereinafter also referred to as "compound (B-1)") and a compound represented by the above formula (B-2) (hereinafter also referred to as "compound (B-2)".

[0036] Hereinafter, each component contained or may be contained in the epoxy resin composition and the epoxy resin composition will be described in detail.

[0037] In addition, unless otherwise specified, the compounds exemplified as the components contained or may be contained in the epoxy resin composition in this specification may be used alone or in combination of two or more.

[0038] 〔1〕Epoxy resin (A)

[0039] The epoxy resin (A) is not particularly limited as long as it has one or more epoxy groups in the molecule. From the viewpoints of the curability of the epoxy resin composition and the heat resistance and strength of the cured product, it is preferably an epoxy resin having two or more epoxy groups in the molecule, and more preferably an epoxy resin having two epoxy groups in the molecule.

[0040] Examples of the epoxy resin having two or more epoxy groups in the molecule include:

[0041] Aromatic glycidyl ether epoxy resins that can be obtained by reacting polyphenol compounds such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, biphenyl glycol, naphthalene glycol, and novolac resins obtained by condensing or co-condensing phenols and aldehydes with epichlorohydrin;

[0042] Aliphatic glycidyl ether epoxy resins can be obtained by reacting polyol compounds such as 1,4-butanediol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, neopentyl glycol, glycerol, pentaerythritol, and sorbitol with epichlorohydrin;

[0043] Glycidyl ester type epoxy resins can be obtained by reacting polyacids such as phthalic acid, hexahydrophthalic acid, dimer acid, etc. with epichlorohydrin;

[0044] Glycidylamine-type epoxy resins can be obtained by reacting amines such as aniline, toluidine, diaminodiphenylmethane, p-aminophenol, and p-aminocresol with epichlorohydrin;

[0045] Alicyclic epoxy resins can be obtained by oxidizing olefin compounds having two or more unsaturated bonds in the molecule such as soybean oil and polybutadiene, or cyclic olefin compounds having two or more unsaturated bonds in the molecule such as indene, 4-vinyl-1-cyclohexene, and 3-cyclohexene-1-carboxylic acid (3-cyclohexenyl) methyl ester with a peracid (such as peracetic acid).

[0046] The epoxy resins exemplified above may be epoxy resins having two epoxy groups in the molecule.

[0047] Examples of the aromatic glycidyl ether epoxy resin having two epoxy groups in the molecule include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD ​​epoxy resin, bisphenol S epoxy resin, biphenyl glycol epoxy resin, and naphthalene glycol epoxy resin.

[0048] Examples of the aliphatic glycidyl ether epoxy resin having two epoxy groups in the molecule include hydrogenated bisphenol A epoxy resin, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0049] Examples of the glycidyl ester-type epoxy resin having two epoxy groups in the molecule include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl dimer acid ester.

[0050] Examples of the glycidylamine-type epoxy resin having two epoxy groups in the molecule include glycidylaniline and glycidyltoluidine.

[0051] From the viewpoints of the viscosity of the epoxy resin, and further the viscosity and curability of the epoxy resin composition, as well as the heat resistance and strength of the cured product, the epoxy resin (A) preferably comprises an aromatic glycidyl ether epoxy resin, more preferably a bisphenol epoxy resin, and even more preferably a bisphenol A epoxy resin.

[0052] The epoxy resin (A) preferably contains a liquid epoxy resin. More preferably, when the epoxy resin (A) contains one or more epoxy resins, the entire epoxy resin (A) is liquid.

[0053] In this specification, "liquid" means exhibiting fluidity at 25°C. In this specification, a "liquid" substance generally exhibits viscosity, and its viscosity can be 0.0001 Pa·s to 1000 Pa·s, or 0.001 Pa·s to 500 Pa·s, as measured at 25°C using a viscometer using an electromagnetic rotation method (EMS viscometer), or within a viscosity range that cannot be measured using an EMS viscometer, as measured at 25°C using an E-type viscometer.

[0054] The term "liquid state" includes a state in which one or more components are dispersed in other components.

[0055] As a case where the epoxy resin (A) is entirely liquid, the following cases are mentioned, for example.

[0056] a) When the epoxy resin (A) is composed of one liquid epoxy resin

[0057] b) When the epoxy resin (A) is a mixture of two or more liquid epoxy resins

[0058] c) The epoxy resin (A) is a mixture of one or more liquid epoxy resins and one or more solid epoxy resins, and the mixture is liquid.

[0059] d) The epoxy resin (A) is a mixture of two or more solid epoxy resins, and the mixture is in a liquid state.

[0060] Therefore, the epoxy resin (A) may include a solid epoxy resin. In this specification, "solid" means solid at 25°C. The solid epoxy resin may be dissolved in the liquid epoxy resin or dispersed in the liquid epoxy resin. In order to uniformly carry out the curing reaction, the solid epoxy resin is preferably uniformly dissolved.

[0061] From the viewpoint of adjusting the viscosity of the epoxy resin composition to a preferred range, the viscosity of the epoxy resin (A) (when containing two or more epoxy resins, the viscosity of the mixture of the two or more epoxy resins) at 25°C based on an EMS viscometer is preferably 50 Pa·s or less, more preferably 40 Pa·s or less, and even more preferably 20 Pa·s or less.

[0062] The viscosity of the epoxy resin (A) at 25° C. is usually 0.01 Pa·s or higher, and may be 0.1 Pa·s or higher, or 1 Pa·s or higher.

[0063] The viscosity of the epoxy resin (A) is preferably 0.01 Pa·s to 50 Pa·s, more preferably 0.1 Pa·s to 40 Pa·s, and even more preferably 1 Pa·s to 20 Pa·s, as measured at 25°C by an EMS viscometer.

[0064] The epoxy resin having two or more epoxy groups in the molecule may be used alone or in combination of two or more.

[0065] Combination use of a bisphenol A epoxy resin and a biphenyl epoxy resin is sometimes advantageous in achieving both good heat resistance and good tensile properties, and is therefore preferred.

[0066] The epoxy resin (A) preferably contains an epoxy resin having two epoxy groups in the molecule.

[0067] The epoxy resin (A) may contain an epoxy resin having two epoxy groups in the molecule, and one or more epoxy resins selected from an epoxy resin having one epoxy group in the molecule and an epoxy resin having three or more epoxy groups in the molecule.

[0068] The content of the epoxy resin having two epoxy groups in the molecule in the epoxy resin (A) is, for example, 50 parts by mass or more in 100 parts by mass of the epoxy resin (A). From the viewpoint of the properties of the cured product of the epoxy resin composition (heat resistance and / or tensile properties, etc.), it is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, further preferably 80 parts by mass or more, further preferably 90 parts by mass or more, and may be 100 parts by mass.

[0069] From the viewpoints of tensile properties, heat resistance, and strength of the cured product of the epoxy resin composition, the epoxy equivalent of the epoxy resin (A) (when containing two or more epoxy resins, the epoxy equivalent as a mixture of the two or more epoxy resins) is preferably 30 g / eq or more and 500 g / eq or less, more preferably 40 g / eq or more and 400 g / eq or less, even more preferably 50 g / eq or more and 300 g / eq or less, and even more preferably 50 g / eq or more and 250 g / eq or less.

[0070] The epoxy equivalent of the epoxy resin can be measured in accordance with JIS K 7236.

[0071] 〔2〕Curing agent (B)

[0072] The curing agent (B) contains a compound capable of crosslinking and curing the epoxy resin (A). The curing agent (B) contains a compound (B-1) represented by the above formula (B-1) and a compound (B-2) represented by the above formula (B-2).

[0073] The curing agent (B) may contain one type of compound (B-1) or two or more types.

[0074] The curing agent (B) may contain one type of compound (B-2) or two or more types.

[0075] In the above formula (B-1), R 1 represents a hydrogen atom, a halogen atom, a methoxy group or a hydrocarbon group having 1 to 12 carbon atoms.

[0076] As R 1 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0077] As R 1 The hydrocarbon group having 1 to 12 carbon atoms in the alkyl group includes an aliphatic group (such as an alkyl group), an alicyclic group (such as a cycloalkyl group), an aromatic group, a hydrocarbon group comprising a combination of an aliphatic group and an alicyclic group, and a hydrocarbon group comprising a combination of an aromatic group and an aliphatic group and / or an alicyclic group.

[0078] The number of carbon atoms in the hydrocarbon group is preferably 1 to 8. From the viewpoint of the viscosity of the epoxy resin composition, the hydrocarbon group is a methyl group or a 1-phenylethyl group.

[0079] R 1 It is preferably a hydrogen atom or a hydrocarbon group, and more preferably a hydrogen atom.

[0080] The positional relationship of the two OH groups possessed by compound (B-1) may be any of the ortho, meta, and para positions. From the viewpoint of reducing the viscosity of the epoxy resin composition and suppressing crystallization in the epoxy resin composition, the ortho or meta position is preferred, and the meta position is more preferred.

[0081] From the viewpoint of reducing the viscosity of the epoxy resin composition, suppressing crystallization in the epoxy resin composition, and lowering the dissolution temperature when preparing the epoxy resin composition, the compound (B-1) is preferably a compound having a melting point of 150°C or lower, more preferably a compound having a melting point of 130°C or lower.

[0082] Examples of the compound (B-1) having a melting point of 150° C. or lower include catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), 4-fluoro-1,3-dihydroxybenzene, 2-chloro-1,3-dihydroxybenzene, 4-chloro-1,3-dihydroxybenzene, 2-methoxy-1,3-dihydroxybenzene, 4-methoxy-1,3-dihydroxybenzene, 5-methoxy-1,3-dihydroxybenzene, 4-methyl-1,3-dihydroxybenzene, 5-methyl-1,3-dihydroxybenzene, 2-ethyl-1,3-dihydroxybenzene, 4-ethyl-1,3-dihydroxybenzene, 5-ethyl-1,3-dihydroxybenzene, and 4-(1-phenylethyl)-1,3-dihydroxybenzene.

[0083] In the epoxy resin composition according to one preferred embodiment, the compound (B-1) contains 1,3-dihydroxybenzene.

[0084] In the above formula (B-2), R 2 represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group.

[0085] As R 2 Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0086] From the perspective of melting point, R 2 It is preferably a hydrogen atom, a methyl group or a methoxy group, and more preferably a hydrogen atom.

[0087] In a preferred embodiment of the epoxy resin composition, the compound (B-1) comprises 1,3-dihydroxybenzene, and the compound (B-2) comprises dihydrocoumarin (R 2 : hydrogen atom).

[0088] The content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

[0089] The content of compound (B-2) is 2 mass parts or more and 5 mass parts or less of the epoxy resin composition of the present invention relative to epoxy resin (A) 100 mass parts, low viscosity and long pot life can be shown, and a cured product showing good heat resistance can be provided. From this viewpoint, the content of compound (B-2) is preferably 2.5 mass parts or more and 4.5 mass parts or less relative to epoxy resin (A) 100 mass parts, more preferably 2.5 mass parts or more and 4 mass parts or less, further preferably 2.5 mass parts or more and 3.5 mass parts or less. The compound (B-2) containing the above-mentioned prescribed amount is also advantageous in improving the tensile properties of the above-mentioned cured product.

[0090] If the content of compound (B-2) in the epoxy resin composition is too low, the viscosity of the epoxy resin composition may increase and / or the heat resistance of the cured product may decrease. If the content of compound (B-2) in the epoxy resin composition is too high, the pot life of the epoxy resin composition may be deteriorated.

[0091] Containing the compound (B-1) in the epoxy resin composition is advantageous in improving the properties (heat resistance and / or tensile properties, etc.) of the cured product of the epoxy resin composition.

[0092] The epoxy resin composition may further contain a compound having three or more phenolic hydroxyl groups. Inclusion of such a compound may improve the properties (heat resistance and / or tensile properties, etc.) of the cured product of the epoxy resin composition.

[0093] Examples of the compound having three or more phenolic hydroxyl groups include compounds obtained by replacing one hydrogen atom directly bonded to the benzene ring of the compound (B-1) with a hydroxyl group, phenolic resins, and novolac resins.

[0094] The epoxy resin composition may contain a compound having one phenolic hydroxyl group. Examples of the compound having one phenolic hydroxyl group include phenol, cresol, xylenol, and tert-butylphenol.

[0095] The molar ratio of the phenolic hydroxyl group content to the epoxy group content in the epoxy resin composition is, for example, 0.20 to 0.75. From the viewpoint of improving the properties of the cured product (heat resistance and / or tensile properties, etc.), it is preferably 0.25 to 0.67, more preferably 0.3 to 0.6, further preferably 0.35 to 0.55, and even more preferably 0.4 to 0.5.

[0096] The “epoxy group content in the epoxy resin composition” refers to the number (number of moles) of epoxy groups possessed by the epoxy resin (A).

[0097] The "phenolic hydroxyl group content" is the phenolic hydroxyl group content in the epoxy resin composition, and refers to the total number (in moles) of phenolic hydroxyl groups possessed by compound (B-1) and the number (in moles) of phenolic hydroxyl groups possessed by phenolic compounds having phenolic hydroxyl groups other than compound (B-1).

[0098] The content of the compound (B-1) in the epoxy resin composition is preferably an amount such that the molar ratio falls within the above range, and is, for example, 1 part by mass or more and 30 parts by mass or less, preferably 5 parts by mass or more and 25 parts by mass or less, and more preferably 8 parts by mass or more and 22 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A).

[0099] From the viewpoint of curability of the epoxy resin composition, the ratio of the content of the compound (B-2) in the epoxy resin composition to the content of the compound (B-1) is preferably 0.20 or more and 0.95 or less, more preferably 0.20 or more and 0.75 or less, and even more preferably 0.20 or more and 0.50 or less in terms of mass ratio.

[0100] The epoxy resin composition may further contain other epoxy resin curing agents other than those mentioned above. Other epoxy resin curing agents may be conventionally known curing agents.

[0101] However, from the viewpoint of the viscosity or pot life of the epoxy resin composition and the properties of the cured product (heat resistance and / or tensile properties, etc.), the content of other epoxy resin curing agents in the curing agent (B) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less (e.g., 0 parts by mass), based on the total amount of the curing agent (B) being 100 parts by mass.

[0102] [3] Imidazole adduct type curing accelerator (C)

[0103] In this specification, the term "curing accelerator" refers to an agent that accelerates the curing reaction. The term "accelerator" as used herein also includes initiating the curing reaction.

[0104] In the present invention, an imidazole adduct curing accelerator (C) is used as a curing accelerator. The use of the imidazole adduct curing accelerator (C) is beneficial for achieving a balanced pot life and curability (fast curing, etc.) of the epoxy resin composition. This is presumably because the imidazole adduct curing accelerator (C) can effectively initiate and / or accelerate the curing reaction between the epoxy resins (A) and the curing reaction between the epoxy resin (A) and the compound (B-1) and the compound (B-2), and the imidazole adduct curing accelerator (C) generally has a latent property, thus being beneficial for extending the pot life.

[0105] Furthermore, the use of an imidazole adduct-type curing accelerator (C) as the curing accelerator is also advantageous in that the curing reaction can proceed at a relatively low temperature and in that the storage stability of the epoxy resin composition can be improved.

[0106] The imidazole adduct-type curing accelerator (C) may be used alone or in combination of two or more.

[0107] "Latent" means that the material can be stably stored at room temperature (25°C) even in the presence of an epoxy resin or an epoxy resin and a curing agent, and can exhibit a property that promotes the curing reaction by heat, light, pressure, etc.

[0108] The imidazole adduct-type curing accelerator (C) used in the present invention preferably has a property (thermal latency) capable of expressing a function of accelerating a curing reaction by heat.

[0109] Imidazole adduct-type curing accelerators (C) are compounds in which an adduct is added to an imidazole compound. The addition of the adduct imparts latency. For example, the adduct is a compound capable of reacting with the imidazole compound to form a bond with a nitrogen atom, preferably the nitrogen atom at the 1-position, of the imidazole ring. This bond is typically a covalent bond.

[0110] The adduct is preferably a compound capable of imparting good latency, and examples thereof include epoxy compounds, isocyanate compounds, (meth)acrylic compounds, and urea compounds.

[0111] The imidazole adduct-type curing accelerator (C) is preferably a polymer compound obtained by reacting the above-mentioned adduct with an imidazole compound.

[0112] In addition, the above-mentioned adduct may be further made into a solid solution with a phenolic resin or the like, or surface-treated with an organic acid, a boric acid compound or the like.

[0113] The thus produced imidazole adduct type curing accelerator (C) is usually pulverized into a particle size of about 0.5 to 50 μm and dispersed in an epoxy resin for use.

[0114] The solubility of an imidazole adduct type curing accelerator (C) in an epoxy resin is generally low at room temperature. Therefore, the imidazole adduct type curing accelerator (C) mixed with the epoxy resin often exhibits thermal latency.

[0115] The imidazole adduct curing accelerator (C) can be produced by the methods described in known patent documents, such as Japanese Patent Application Laid-Open No. 59-053526, Japanese Patent Application Laid-Open No. 60-004524, Japanese Patent Application Laid-Open No. 60-072917, Japanese Patent Application Laid-Open No. 2005-206744, Japanese Patent Application Laid-Open No. 06-073156, Japanese Patent Application Laid-Open No. 06-172495, Japanese Patent Application Laid-Open No. 2008-214567, and Japanese Patent Application Laid-Open No. 2014-177525.

[0116] As the imidazole adduct-type curing accelerator (C), a commercially available product can be used. Commercially available products of the imidazole adduct-type curing accelerator (C) are all represented by trade names, and include “FUJICURE FXR-1020”, “FUJICURE FXR-1030”, “FUJICURE FXR-1032”, “FUJICURE FXR-1081”, “FUJICURE FXR-1121”, and “FUJICURE FXR-1131” (all manufactured by T&K TOKA Co., Ltd.); “ADEKA HARDENER EH-5011S” and “ADEKA HARDENER EH-5046S” (all manufactured by ADEKA Co., Ltd.); “Cureduct P-0505” (manufactured by Shikoku Chemicals Co., Ltd.); “Amicure PN-23”, “Amicure PN-23J”, “Amicure PN-31”, “Amicure PN-31J”, “Amicure PN-40”, and “Amicure PN-40J", "Amicure PN-50", "Amicure PN-F", "Amicure PN-H" (the above, manufactured by Ajinomoto Fine-Techno Co., Ltd.), etc.

[0117] The epoxy resin composition may contain one or two or more curing accelerators other than the imidazole adduct-type curing accelerator (C) as long as the effects of the present invention are not inhibited.

[0118] Other curing accelerators are not particularly limited, and examples thereof include tertiary amine compounds and salts thereof, imidazole compounds (non-adduct type), imidazolium salts, triphenylphosphine, phosphorus compounds such as phosphonium salts, carboxylic acid metal salts, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole (TBZ), and the like.

[0119] From the viewpoint of more effectively exhibiting the above-mentioned effects, when the total amount of the curing accelerator is 100 parts by mass, the content of other curing accelerators in the curing accelerator is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, further preferably 5 parts by mass or less, and even more preferably 1 part by mass or less (for example, 0 parts by mass).

[0120] The content of the imidazole adduct-type curing accelerator (C) in the epoxy resin composition is, for example, 1 part by mass or more and 50 parts by mass or less relative to 100 parts by mass of the epoxy resin (A). From the viewpoint of more effectively exhibiting the above-mentioned effect, it is preferably 2 parts by mass or more and 40 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, further preferably 5 parts by mass or more and 20 parts by mass or less, and even more preferably 5 parts by mass or more and 15 parts by mass or less.

[0121] 〔4〕Lewis acid compound (D)

[0122] The epoxy resin composition may further contain a Lewis acid compound (D) having a boron atom or an aluminum atom (hereinafter, also referred to as "Lewis acid compound (D)"). By including the Lewis acid compound (D) in the epoxy resin composition, the pot life can be further extended. In addition, by including the Lewis acid compound (D) in the epoxy resin composition, the pot life can be further extended without compromising the rapid curing property, and a cured product of the epoxy resin composition having good properties (heat resistance and / or tensile properties, etc.) can be obtained.

[0123] The Lewis acid compound (D) is preferably in a liquid state. The meaning of "liquid state" is as described above.

[0124] The epoxy resin composition may contain one or two or more Lewis acid compounds (D).

[0125] The Lewis acid compound (D) is a compound represented by the following formula (1).

[0126]

[0127] In formula (1), X represents B (boron atom) or Al (aluminum atom). 3 、R 4 and R 5 Each independently represents a linear or branched alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, or a monovalent group represented by the following formula (2). 3 、R 4 and R 5 Each may be substituted by any substituent.

[0128]

[0129] In formula (2), R 6 and R 7 Each R is independently a linear or branched alkyl group having 1 to 22 carbon atoms, an aryl group having 6 to 22 carbon atoms, or an oxyalkyl group having 1 to 22 carbon atoms. 6 and R 7 Each may be substituted by any substituent.

[0130] In formula (1), R 3 、R 4 and R 5Each is independently preferably a linear or branched alkyl group having 1 to 22 carbon atoms or a group represented by formula (2), more preferably a linear or branched alkyl group having 1 to 12 carbon atoms or a group represented by formula (2), and further preferably a linear or branched alkyl group having 2 to 8 carbon atoms or a group represented by formula (2). 6 and R 7 Each independently is preferably a linear or branched alkyl group having 1 to 22 carbon atoms or an oxyalkyl group having 1 to 22 carbon atoms, more preferably a linear or branched alkyl group having 1 to 12 carbon atoms or an oxyalkyl group having 1 to 12 carbon atoms, and still more preferably a linear or branched alkyl group having 2 to 8 carbon atoms or an oxyalkyl group having 1 to 8 carbon atoms.

[0131] Examples of the Lewis acid compound (D) in which X in formula (1) is B include triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, triisobutyl borate, tri-sec-butyl borate, tri-tert-butyl borate, tri-n-hexyl borate, and tri-n-octyl borate.

[0132] Examples of the Lewis acid compound (D) in which X in formula (1) is Al include aluminum sec-butoxide, aluminum diisopropylate mono-sec-butoxide, aluminum ethyl acetoacetate diisopropylate, aluminum ethyl acetoacetate diisopropylate, aluminum tris(ethyl acetoacetate), aluminum monoacetylacetonate bis(ethyl acetoacetate), and aluminum stearyl acetoacetate diisopropylate.

[0133] When the epoxy resin composition contains a Lewis acid compound (D), the content of the Lewis acid compound (D) in the epoxy resin composition is, for example, 0.01 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the epoxy resin (A). From the viewpoint of further extending the pot life, it is preferably 0.05 parts by mass or more and 20 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, even more preferably 0.2 parts by mass or more and 5 parts by mass or less, and even more preferably 0.3 parts by mass or more and 3 parts by mass or less.

[0134] 〔5〕Other ingredients

[0135] The epoxy resin composition may further contain other compounding components besides the above-mentioned components.

[0136] Examples of other ingredients include rubber particles, inorganic particles (particles containing metals such as aluminum, calcium carbonate, and metal compounds such as silica), flame retardants, surface treatment agents, release agents, antibacterial agents, leveling agents, defoaming agents, thixotropic agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, coupling agents, surfactants, metal alkoxides (metal alkoxides other than the Lewis acid compound (D)), thermoplastic resins, diluents, and barbituric acid.

[0137] Other compounding components may be used alone or in combination of two or more.

[0138] By adding rubber particles, the toughness of the cured product of the epoxy resin composition can be improved while maintaining good heat resistance.

[0139] Examples of the rubber particles include core-shell acrylic rubber particles, surface-modified acrylic rubber particles, crosslinked NBR particles, and silicone rubber particles. These rubber particles may be conventionally known rubber particles.

[0140] The average particle size of the rubber particles is, for example, 0.05 μm or more and 1 μm or less, and preferably 0.2 μm or more and 0.5 μm or less.

[0141] The rubber particles may be used alone or in combination of two or more.

[0142] As rubber particles, commercially available products or dispersions prepared by pre-dispersing rubber particles in an epoxy resin may be used. Commercially available rubber particles or dispersions are indicated by trade names, including "ACRYSET BPA328" (manufactured by Nippon Shokubai Co., Ltd.); "KaneAce MX-153," "KaneAce MX-154," "KaneAce MX-257," and "KaneAce MX-960" (all manufactured by Kaneka Co., Ltd.); "STAPHYLOID AC" series (manufactured by Aica Kogyo Co., Ltd.); "PARALOID EXL" series (manufactured by Dow Chemical); "METABLEN" (manufactured by Mitsubishi Chemical Co., Ltd.); "XER-91" (manufactured by JSR Corporation); and "GENIOPERL P52" (manufactured by Wacker Asahikasei Silicone Co., Ltd.).

[0143] The content of the rubber particles in the epoxy resin composition is, for example, 1 part by mass or more and 100 parts by mass or less relative to 100 parts by mass of the epoxy resin (A). From the viewpoint of more effectively exhibiting the above-mentioned effects, it is preferably 5 parts by mass or more and 80 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass or less.

[0144] The content of the rubber particles in the epoxy resin composition is, for example, 1% by mass to 50% by mass, based on the total mass of the composition. From the viewpoint of more effectively exhibiting the above-mentioned effects, it is preferably 2% by mass to 30% by mass, and more preferably 2% by mass to 20% by mass.

[0145] Adding barbituric acid to the epoxy resin composition is beneficial to extending the pot life of the epoxy resin composition.

[0146] [6] Epoxy resin composition

[0147] The epoxy resin composition of the present invention comprising epoxy resin (A), compound (B-1), compound (B-2), imidazole adduct curing accelerator (C), and optionally other components is preferably in liquid form. The meaning of "liquid form" is as described above.

[0148] In a liquid epoxy resin composition, all components contained therein may be in a dissolved state, or one or more components may be dispersed in other components.

[0149] The liquid epoxy resin composition of the present invention can have a low viscosity. Low viscosity can improve the productivity and workability of products using the epoxy resin composition. For example, a method for producing a molding material (composition) comprising a cured product of the epoxy resin composition and fibers, etc., includes a step of impregnating a fiber fabric or fiber bundle with the epoxy resin composition. Consequently, the use of a low-viscosity epoxy resin composition can improve the impregnation properties of the epoxy resin composition.

[0150] The viscosity of the epoxy resin composition, as measured at 25°C using an EMS viscometer, is preferably 50 Pa·s or less, more preferably 40 Pa·s or less, even more preferably 30 Pa·s or less, even more preferably 25 Pa·s or less, and particularly preferably 20 Pa·s or less. The viscosity of the epoxy resin composition at 25°C is typically 0.01 Pa·s or greater, and may be 0.1 Pa·s or greater, or 1 Pa·s or greater.

[0151] The viscosity of the epoxy resin composition is preferably 0.01 Pa·s to 50 Pa·s at 25°C measured by an EMS viscometer, more preferably 0.1 Pa·s to 40 Pa·s, further preferably 1 Pa·s to 30 Pa·s, further preferably 1 Pa·s to 25 Pa·s, and particularly preferably 1 Pa·s to 20 Pa·s.

[0152] The epoxy resin composition of the present invention can have a long pot life. For example, the viscosity of the epoxy resin composition when stored at 25°C for 1 day (24 hours) after preparation is preferably within the above range. In addition, the time from preparation of the epoxy resin composition until the composition thickens to twice the initial viscosity is preferably long. The time until the composition thickens to twice the initial viscosity is generally about 3 days or more, preferably 5 days or more, more preferably 6 days or more, and even more preferably 7 days or more.

[0153] The epoxy resin composition of the present invention can exhibit good curability, that is, the epoxy resin composition can be fully cured in a relatively short heat curing time and / or at a relatively low temperature.

[0154] <Cured product>

[0155] The cured product of the present invention is obtained by curing the epoxy resin composition of the present invention.

[0156] The cured product of the present invention is a cured product of the epoxy resin composition of the present invention, and therefore can have good heat resistance or good tensile properties.

[0157] The cured product of the present invention can exhibit a glass transition temperature of, for example, 110° C. or higher, further 115° C. or higher, further 120° C. or higher, and further 125° C. or higher.

[0158] The elongation at break of the cured product of the present invention in the tensile properties according to JIS K 7161-1 and JIS K 7161-2 may be, for example, 4.0% or more, further 5.0% or more, further 6.0% or more, further 7.0% or more, further 7.5% or more.

[0159] The epoxy resin composition of the present invention and its cured product have excellent heat resistance and, consequently, excellent tensile properties, and therefore can be used in a variety of applications, such as as adhesives, for sealing electronic components, and as resin compositions for impregnation into fibers. Furthermore, the epoxy resin composition of the present invention has low viscosity and excellent impregnation properties, and cures in a short time (e.g., 15 minutes at 135°C) upon heating, resulting in excellent productivity. Therefore, it is suitable for use as a resin composition for sealing electronic components and impregnation into fibers.

[0160] The present invention also relates to a product or component comprising the cured product. An example of the product is a formed article (composition) comprising the cured product and fibers. The product or component comprising the cured product may, for example, contain components other than the components (cured product) derived from the epoxy resin composition, such as fibers.

[0161] Hereinafter, the case of using the epoxy resin composition of the present invention as a resin composition for impregnation into fibers will be described.

[0162] Fibers used in combination with the epoxy resin composition of the present invention include PAN-based carbon fibers, pitch-based carbon fibers, glass fibers, aramid fibers, kenaf fibers, etc. The surface of the fibers may be subjected to a known sizing treatment.

[0163] As a method for producing a molded article by compounding the epoxy resin composition of the present invention with fibers, a known method can be used. Specifically, the following methods can be mentioned:

[0164] Wet filament winding method, in which the fiber is impregnated with an epoxy resin composition, wound around a mandrel or other forming mold to form it, and then heated to cure;

[0165] Dry filament winding method, which prepares a tow prepreg in which the fiber is pre-impregnated with an epoxy resin composition, winds the tow prepreg around a forming mold such as a mandrel to form it, and heats and cures it;

[0166] Resin transfer molding method, making a fiber fabric, stacking the fiber fabric on a mold and pressurizing it to make a preform, vacuum impregnating the preform with an epoxy resin composition, and heating and curing it;

[0167] The sheet winding method prepares a prepreg made by pre-impregnating a fiber fabric with an epoxy resin composition, winds it around a molding die such as a mandrel, and heat-cures it.

[0168] The press molding method involves preparing a prepreg made by pre-impregnating a fiber fabric with an epoxy resin composition, laminating the prepreg in a mold, and pressing it to cure it under heat and pressure.

[0169] The autoclave molding method involves preparing a prepreg made by pre-impregnating a fiber fabric with an epoxy resin composition, placing the prepreg on a molding jig, covering it with a bag film, and curing it under heating and pressure in an autoclave.

[0170] The present invention also provides a cured product of a prepreg comprising the epoxy resin composition of the present invention and fibers. Examples of such cured products include cured products of prepregs (tow prepregs, etc.) obtained by pre-impregnating fibers or fabrics of fibers with the epoxy resin composition. As described above, such cured products may be cured molded articles.

[0171] Example

[0172] The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. In the Examples, % and parts indicating the content or usage amount are by mass unless otherwise specified.

[0173] <Examples 1 to 17, Comparative Examples 1 to 8>

[0174] (1) Preparation of epoxy resin composition

[0175] Epoxy resin compositions were prepared by mixing the components shown in Tables 1 to 4 below in the amounts shown. In Tables 1 to 4, the amounts of each component are expressed in parts by mass. In all Examples and Comparative Examples, the resulting epoxy resin compositions were liquid (fluid at 25°C).

[0176] The "OH / EP molar ratio" column in Tables 1 to 4 shows the molar ratio of the phenolic hydroxyl group content to the epoxy group content in the epoxy resin composition, calculated from the charge amount. Furthermore, the "Curing Agent 2 / Curing Agent 1 Mass Ratio" column in Tables 1 to 4 shows the mass ratio of the content of Curing Agent 2 to the content of Curing Agent 1 in the epoxy resin composition.

[0177] The rubber particles are incorporated by using a composition in which the rubber particles are dispersed in an epoxy resin as a component for preparing the epoxy resin composition.

[0178] The details of the respective blending components shown in Tables 1 to 4 are as follows.

[0179] [a] Epoxy Resin 1: Epoxy resin "jER828" (bisphenol A-type epoxy resin, epoxy equivalent: 184-194 g / eq, viscosity: 12-15 Pa·s (25°C)) contained in "ACRYSET BP-328" (a composition of acrylic rubber particles dispersed in an epoxy resin) manufactured by Nippon Shokubai Co., Ltd.

[0180] [b] Epoxy resin 2: Liquid epoxy resin manufactured by Kukto Chemical under the trade name "EPOKUKDO YD-127" (bisphenol A type epoxy resin, epoxy equivalent weight: 180-190 g / eq, viscosity: 8-11 Pa·s (25°C))

[0181] [c] Epoxy resin 3: Liquid epoxy resin manufactured by ADEKA Corporation, trade name "ADEKARESIN EP-4300E" (bisphenol A type epoxy resin, epoxy equivalent: 185 g / eq, viscosity: 8 Pa·s (25°C))

[0182] [d] Epoxy resin 4: solid epoxy resin manufactured by Mitsubishi Chemical Co., Ltd., trade name "jERYX4000" (biphenyl type epoxy resin, epoxy equivalent: about 190 g / eq, melting point: about 105°C)

[0183] [e] Curing agent 1: 1,3-dihydroxybenzene (resorcinol)

[0184] [f] Curing agent 2: dihydrocoumarin

[0185] [g] Curing accelerator 1: Imidazole adduct type curing accelerator manufactured by T&K TOKA Co., Ltd., trade name "FUJICURE FXR-1121" (latent)

[0186] [h] Curing accelerator 2: Imidazole adduct type curing accelerator manufactured by ADEKA Corporation, trade name "ADEKA HARDENER EH-5011S" (latent)

[0187] [i] Curing accelerator 3: imidazole curing accelerator manufactured by ADEKA Corporation, trade name "ADEKA HARDENEREH-4344" (latent)

[0188] [j] Curing accelerator 4: Imidazole curing accelerator manufactured by ADEKA Corporation, trade name "ADEKA HARDENERE H-5046" (latent)

[0189] [k] Curing accelerator 5: Imidazole curing accelerator manufactured by T&K TOKA Co., Ltd., trade name "FUJICURE FXR-1171" (latent)

[0190] [1] Rubber particles: Acrylic rubber particles contained in the trade name "ACRYSET BP-328" manufactured by Nippon Shokubai Co., Ltd. (a composition in which acrylic rubber particles are dispersed in the trade name "jER828" epoxy resin)

[0191] 〔m〕Lewis acid compound 1: triethyl borate

[0192] 〔n〕Lewis acid compound 2: triisopropyl borate

[0193] 〔o〕Lewis acid compound 3: tri-n-butyl borate

[0194] 〔p〕Lewis acid compound 4: tri-n-octyl borate

[0195] [q] Lewis acid compound 5: ethyl acetoacetate aluminum diisopropoxide

[0196] 〔r〕Lewis acid compound 6: aluminum sec-butoxide

[0197] (2) Evaluation of epoxy resin compositions and their cured products

[0198] (2-1) Viscosity and pot life of epoxy resin composition

[0199] For the epoxy resin composition just after preparation and the epoxy resin composition stored in a constant temperature bath at 25°C for a predetermined period after preparation, approximately 2 g of each epoxy resin composition was sealed in a test tube together with a 4.7 mm aluminum ball probe. The test tube was placed in an EMS viscometer (EMS-1000) manufactured by Kyoto Electronics Co., Ltd. set at 25°C, and the viscosity of the epoxy resin composition was measured under the conditions of a motor speed of 1000 rpm, a measurement time of 2 minutes, and a measurement interval of 30 seconds. The results are shown in Tables 1 to 4. In Tables 1 to 4, "-" means that the measurement was not performed.

[0200] The pot life can be evaluated based on the increase in viscosity over the storage period.

[0201] (2-2) Curability of epoxy resin composition

[0202] The epoxy resin composition was poured into a silicone mold heated to 135° C. and maintained at the same temperature for 15 minutes to perform a curing reaction of the epoxy resin composition layer.

[0203] After the curing reaction, the silicone mold was tilted to visually confirm whether or not droplets were drooping. The curability (fast curing property) of the epoxy resin composition was evaluated according to the following evaluation criteria. The results are shown in Tables 1 to 4.

[0204] A: No droplet dangling occurs, the epoxy resin composition layer after the curing reaction is fully cured, and the epoxy resin composition has fast curing properties.

[0205] B: Droplets dangled, and therefore the epoxy resin composition layer after the curing reaction was not sufficiently cured, and the epoxy resin composition did not have rapid curing properties.

[0206] (2-3) Glass transition temperature (Tg) of cured product

[0207] The epoxy resin composition was poured into a silicone mold heated to 135° C. and maintained at the same temperature for 15 minutes to perform a curing reaction of the epoxy resin composition layer.

[0208] About 40 mg of the cured product of the epoxy resin composition was weighed into an aluminum cuvette, and the glass transition temperature (Tg) was measured using a differential scanning calorimeter (DSAC-60A) manufactured by Shimadzu Corporation. The results are shown in Tables 1 to 4.

[0209] The temperature was raised from 25°C to 135°C at a heating rate of 15°C / min, maintained at 135°C for 20 minutes, then cooled from 135°C to 30°C at a cooling rate of -10°C / min, and then raised from 30°C to 200°C again at a heating rate of 10°C / min. The midpoint of the step-like change of the DSC curve observed at this time was taken as Tg (°C).

[0210] (2-4) Elongation at break of cured product

[0211] The elongation at break among the tensile properties of the cured product of the epoxy resin composition was measured in accordance with JIS K 7161-1 and JIS K 7161-2.

[0212] Specifically, the epoxy resin composition was poured into a silicone mold and cured under the same temperature conditions as in the above (2-2) to obtain a dumbbell test piece in accordance with JIS K7139A-2.

[0213] The resulting test pieces were subjected to tensile testing at a speed of 10 mm / min using an Autograph (AGX-10kNXplus) manufactured by Shimadzu Corporation in accordance with JIS K7161-1 and JIS K 7161-2. The results are shown in Tables 1 to 4. For the measurement of elongation at break, the distance between the marking lines was calculated using a video-based non-contact extensometer (TRView).

[0214] (2-5) Fracture toughness of cured product

[0215] The fracture toughness K of the cured epoxy resin composition having a thickness of 6 mm was measured according to ASTM D5045-14. 1C .

[0216] Specifically, the epoxy resin composition was poured into a silicone mold and cured under the same temperature conditions as in (2-2) above, yielding a 6 mm × 150 mm × 150 mm cured product. This cured product was then cut to produce a 6 mm × 60 mm × 12 mm test piece. This was cut using a 30° t1.0 equal-angle slicer and then pre-cracked.

[0217] The pre-cracked test piece was subjected to a bending test at a speed of 1 mm / min using a universal testing machine (Model 5966) manufactured by Instron in accordance with ASTM D5045-14 to measure the breaking load.

[0218] In addition, a test piece of 6 mm × 150 mm × 12 mm was prepared from the above-mentioned cured product of 6 mm × 150 mm × 150 mm by cutting, and after cutting with a 30° t1.0 equal-angle slicer, a pre-crack process was performed.

[0219] The test pieces after the precrack processing were subjected to a bending test at a speed of 2.6 mm / min using a universal testing machine 5966 manufactured by Instron, and the 0.2% yield strength was measured.

[0220] The fracture toughness K was calculated by using the 0.2% yield strength obtained in the bending test instead of the yield stress. 1C (MPa·m 1 / 2 The results are shown in Tables 3 and 4. Fracture toughness K 1C The measurement was carried out on Examples 8 to 10 and 14.

[0221] [Table 1]

[0222]

[0223] [Table 2]

[0224]

[0225] [Table 3]

[0226]

[0227] [Table 4]

[0228]

Claims

1. An epoxy resin composition comprising an epoxy resin (A), a curing agent (B) and an imidazole adduct type curing accelerator (C), The curing agent (B) comprises a compound (B-1) represented by the following formula (B-1) and a compound (B-2) represented by the following formula (B-2). In formula (B-1), R 1 represents a hydrogen atom, a halogen atom, a methoxy group or a hydrocarbon group having 1 to 12 carbon atoms, In formula (B-2), R 2 represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group, The content of the compound (B-2) is 2.5 parts by mass or more and 4.5 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

2. The epoxy resin composition according to claim 1, wherein The molar ratio of the phenolic hydroxyl group content to the epoxy group content in the epoxy resin composition is 0.20 or more and 0.75 or less.

3. The epoxy resin composition according to claim 1 or 2, wherein The content of the compound (B-2) is 2.5 parts by mass or more and 4 parts by mass or less relative to 100 parts by mass of the epoxy resin (A).

4. The epoxy resin composition according to claim 1 or 2, wherein The ratio of the content of the compound (B-2) to the content of the compound (B-1) is 0.20 or more and 0.95 or less in terms of mass ratio.

5. The epoxy resin composition according to claim 1 or 2, wherein The epoxy resin (A) includes an epoxy resin having two epoxy groups in the molecule. 6 . The epoxy resin composition according to claim 1 , further comprising a Lewis acid compound (D) having a boron atom or an aluminum atom. 7 . A cured product comprising the epoxy resin composition according to claim 1 . A prepreg comprising the epoxy resin composition according to any one of claims 1 to 6 and fibers. 9 . A composition comprising a cured product of the epoxy resin composition according to claim 1 and fibers.

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