Epoxy resin composition and cured product thereof

Abstract

Provided is an epoxy resin composition that contains an epoxy resin (A), a curing agent (B), and an imidazole adduct type curing accelerator (C). The curing agent (B) contains a compound (B-1) represented by formula (B-1) [R1 represents a hydrogen atom, a halogen atom, a methoxy group, or a hydrocarbon group having 1-12 carbon atoms] and a compound (B-2) represented by formula (B-2) [R2 represents a hydrogen atom, a halogen atom, a methyl group, or a methoxy group]. The contained amount of the compound (B-2) with respect to 100 parts by mass of the epoxy resin (A) is 2-5 parts by mass.

Description

[Technical field]

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

[0002] Epoxy resins are used in a variety of applications, such as fiber reinforcement, electronic components, adhesives, and coatings, because their cured products have excellent heat resistance, strength, chemical resistance, and adhesive properties. In various applications, a composition containing an epoxy resin (hereinafter referred to as an "epoxy resin composition") usually contains a curing agent for curing the composition, and may further contain a curing accelerator (for example, JP 2015-083634 A (Patent Document 1) and JP 2013-032510 A (Patent Document 2)). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-083634 A [Patent Document 2] JP 2013-032510 A Summary of the Invention [Problem to be solved by the invention]

[0004] An epoxy resin composition is required to have properties according to the application. In general, an epoxy resin composition is required to have a low viscosity and a long pot life from the viewpoint of workability. In addition, a cured product of the epoxy resin composition is required to have high heat resistance and may be required to have tensile properties depending on the application.

[0005] An object of the present invention is to provide an epoxy resin composition which has a low viscosity, a long pot life and is capable of giving a cured product exhibiting good heat resistance, and a cured product thereof. [Means for solving the problem]

[0006] The present invention provides an epoxy resin composition and a cured product thereof as described below. [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) is represented by the following formula (B-1):

[0007] [ka] [In the formula, R 1 represents a hydrogen atom, a halogen atom, a methoxy group, or a hydrocarbon group having 1 to 12 carbon atoms.] and a compound (B-1) represented by the following formula (B-2):

[0008] [ka] [In the formula, R 2 represents a hydrogen atom, a halogen atom, a methyl group, or a methoxy group. and a compound (B-2) represented by the formula: The epoxy resin composition, wherein the content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the epoxy resin (A). [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. [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). [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 or more and 0.95 or less in terms of mass ratio. [5] The epoxy resin composition according to any one of [1] to [4], wherein the epoxy resin (A) contains an epoxy resin having two epoxy groups in the molecule. [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. [7] A cured product of the epoxy resin composition according to any one of [1] to [6]. [8] A prepreg comprising the epoxy resin composition according to any one of [1] to [6] and fibers. [9] A composition comprising a cured product of the epoxy resin composition according to any one of [1] to [6] and fibers. Effect of the Invention

[0009] It is possible to provide an epoxy resin composition which has low viscosity, a long pot life and can give a cured product exhibiting good heat resistance, and a cured product thereof. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Epoxy resin composition> The epoxy resin composition according to the present invention (hereinafter also referred to as "epoxy resin composition") comprises the following components: Epoxy resin (A), A curing agent (B), and Imidazole adduct type curing accelerator (C) Includes. The curing agent (B) includes 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)").

[0011] Hereinafter, each component that is or may be contained in the epoxy resin composition and the epoxy resin composition will be described in detail. In this specification, the compounds exemplified as each component that is or can be contained in the epoxy resin composition can be used alone or in combination of two or more types, unless otherwise specified.

[0012] [1] Epoxy resin (A) 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 preferably contains an epoxy resin having two or more epoxy groups in the molecule, and more preferably contains an epoxy resin having two epoxy groups in the molecule.

[0013] Examples of epoxy resins having two or more epoxy groups in a molecule include: aromatic glycidyl ether type epoxy resins obtainable by reacting epichlorohydrin with polyhydric phenol compounds such as bisphenol A, bisphenol F, bisphenol AD, bisphenol S, biphenyldiol, naphthalenediol, and novolak resins obtained by condensing or co-condensing phenols with aldehydes; aliphatic glycidyl ether type epoxy resins obtainable by reacting polyhydric alcohol compounds such as 1,4-butanediol, 1,6-hexanediol, polyethylene glycol, polypropylene glycol, neopentyl glycol, glycerin, pentaerythritol, and sorbitol with epichlorohydrin; glycidyl ester type epoxy resins obtainable by reacting polybasic acids such as phthalic acid, hexahydrophthalic acid, and dimer acid with epichlorohydrin; glycidylamine-type epoxy resins obtainable by reacting epichlorohydrin with amines such as aniline, toluidine, diaminodiphenylmethane, p-aminophenol, and p-aminocresol; Alicyclic epoxy resins can be obtained by oxidizing olefin compounds with two or more unsaturated bonds in the molecule, such as soybean oil and polybutadiene, and cyclic olefin compounds with two or more unsaturated bonds in the molecule, such as indene, 4-vinyl-1-cyclohexene, and 3-cyclohexene-1-carboxylate (3-cyclohexenyl)methyl, with a peracid (peracetic acid, etc.). etc. The above-exemplified epoxy resin may be an epoxy resin having two epoxy groups in the molecule.

[0014] Examples of aromatic glycidyl ether type epoxy resins having two epoxy groups in the molecule include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, bisphenol S type epoxy resins, biphenyl diol type epoxy resins, and naphthalene diol type epoxy resins. Examples of aliphatic glycidyl ether type epoxy resins having two epoxy groups in the molecule include hydrogenated bisphenol A type epoxy resins, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether. Examples of glycidyl ester type epoxy resins having two epoxy groups in the molecule include diglycidyl phthalate, diglycidyl hexahydrophthalate, and diglycidyl dimerate. Examples of the glycidylamine type epoxy resin having two epoxy groups in the molecule include glycidylaniline and glycidyltoluidine.

[0015] From the viewpoints of the viscosity of the epoxy resin, and therefore 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 contains an aromatic glycidyl ether type epoxy resin, more preferably contains a bisphenol type epoxy resin, and further preferably contains a bisphenol A type epoxy resin.

[0016] The epoxy resin (A) preferably contains a liquid epoxy resin, and more preferably, when the epoxy resin (A) contains one or more kinds of epoxy resins, the epoxy resin (A) as a whole is liquid. In this specification, "liquid" refers to exhibiting fluidity at 25° C. In this specification, a substance that is "liquid" generally exhibits viscosity, and the viscosity may be 0.0001 Pa·s to 1000 Pa·s, or may be 0.001 Pa·s to 500 Pa·s, measured at 25° C. using a viscometer that uses an electromagnetic spinning method (EMS viscometer) or an E-type viscometer in the viscosity range that cannot be measured by an EMS viscometer. The term "liquid" includes a state in which one or more components are dispersed in another component.

[0017] Examples of the case where the epoxy resin (A) as a whole is liquid include the following cases. a) When the epoxy resin (A) consists of one type of liquid epoxy resin b) When the epoxy resin (A) is a mixture of two or more liquid epoxy resins c) When the epoxy resin (A) is a mixture of one or more liquid epoxy resins and one or more solid epoxy resins, the mixture is liquid. d) When the epoxy resin (A) is a mixture of two or more solid epoxy resins, the mixture is in a liquid state.

[0018] Therefore, the epoxy resin (A) may contain a solid epoxy resin. In this specification, "solid" means that it is solid at 25°C. The solid epoxy resin may be dissolved or dispersed in the liquid epoxy resin. In order to carry out the curing reaction uniformly, it is preferable that the solid epoxy resin is dissolved uniformly.

[0019] From the viewpoint of adjusting the viscosity of the epoxy resin composition within a preferred range, the viscosity of the epoxy resin (A) (when two or more types of epoxy resins are contained, the viscosity of a mixture of the two or more types of epoxy resins) measured at 25°C with 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. The viscosity of the epoxy resin (A) at 25° C. is usually 0.01 Pa·s or more, may be 0.1 Pa·s or more, or may be 1 Pa·s or more. The viscosity of the epoxy resin (A), measured at 25°C with an EMS viscometer, is preferably from 0.01 Pa·s to 50 Pa·s, more preferably from 0.1 Pa·s to 40 Pa·s, and even more preferably from 1 Pa·s to 20 Pa·s.

[0020] The epoxy resin having two or more epoxy groups in the molecule may be used alone or in combination of two or more kinds. The combined use of bisphenol A type epoxy resin and biphenyl type epoxy resin is preferred since this can advantageously achieve both good heat resistance and good tensile properties.

[0021] The epoxy resin (A) preferably contains an epoxy resin having two epoxy groups in the molecule. The epoxy resin (A) may contain one or more epoxy resins selected from the group consisting of epoxy resins having two epoxy groups in the molecule, epoxy resins having one epoxy group in the molecule, and epoxy resins having three or more epoxy groups in the molecule. 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, and from the viewpoint of the properties (heat resistance and / or tensile properties, etc.) of the cured product of the epoxy resin composition, is preferably 60 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, still more preferably 90 parts by mass or more, and may be 100 parts by mass.

[0022] The epoxy equivalent of the epoxy resin (A) (when two or more epoxy resins are contained, the epoxy equivalent as a mixture of the two or more epoxy resins) is, from the viewpoints of the tensile properties, heat resistance, strength, etc. of the cured product of the epoxy resin composition, preferably from 30 g / eq to 500 g / eq, more preferably from 40 g / eq to 400 g / eq, even more preferably from 50 g / eq to 300 g / eq, and still more preferably from 50 g / eq to 250 g / eq. The epoxy equivalent of the epoxy resin can be measured in accordance with JIS K 7236.

[0023] [2] Hardener (B) The curing agent (B) contains a compound capable of crosslinking and curing the epoxy resin (A). As such compounds, 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). The curing agent (B) may contain one type of compound (B-1), or may contain two or more types of compound (B-1). The curing agent (B) may contain one type of compound (B-2) or two or more types of compound (B-2).

[0024] 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. R 1 Examples of the halogen atom in include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R 1 Examples of the hydrocarbon group having 1 to 12 carbon atoms in the formula include an aliphatic group (such as an alkyl group), an alicyclic group (such as a cycloalkyl group), an aromatic group, a hydrocarbon group consisting of a combination of an aliphatic group and an alicyclic group, and a hydrocarbon group consisting of a combination of an aromatic group and an aliphatic group and / or an alicyclic group. 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. R 1 is preferably a hydrogen atom or a hydrocarbon group, and more preferably a hydrogen atom.

[0025] The positional relationship of the two OH groups in the compound (B-1) may be any one of ortho-, meta-, or para-positions, but from the viewpoint of reducing the viscosity of the epoxy resin composition and suppressing crystal precipitation in the epoxy resin composition, the positions are preferably ortho- or meta-positions, and more preferably meta-positions.

[0026] From the viewpoints of reducing the viscosity of the epoxy resin composition, suppressing crystal precipitation 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 less, and more preferably a compound having a melting point of 130° C. or less.

[0027] Examples of the compound (B-1) having a melting point of 150° C. or less include catechol (1,2-dihydroxybenzene), resorcin (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. In an epoxy resin composition according to one preferred embodiment, the compound (B-1) includes 1,3-dihydroxybenzene.

[0028] In the above formula (B-2), R 2 represents a hydrogen atom, a halogen atom, a methyl group, or a methoxy group. R 2 Examples of the halogen atom in include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R 2 From the viewpoint of melting point, is preferably a hydrogen atom, a methyl group, or a methoxy group, and more preferably a hydrogen atom.

[0029] In one preferred embodiment of the epoxy resin composition, the compound (B-1) contains 1,3-dihydroxybenzene and the compound (B-2) contains dihydrocoumarin (R 2 :Hydrogen atom).

[0030] The content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the epoxy resin (A). According to the epoxy resin composition of the present invention, in which the content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the epoxy resin (A), it is possible to provide a cured product that exhibits low viscosity and a long pot life and good heat resistance. From this viewpoint, the content of the compound (B-2) is preferably 2.5 parts by mass or more and 4.5 parts by mass or less, more preferably 2.5 parts by mass or more and 4 parts by mass or less, and even more preferably 2.5 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the epoxy resin (A). The inclusion of the above-mentioned predetermined amount of the compound (B-2) can be advantageous in terms of improving the tensile properties of the cured product.

[0031] If the content of the compound (B-2) in the epoxy resin composition is too small, the viscosity of the epoxy resin composition may increase and / or the heat resistance of the cured product may decrease, whereas if the content of the compound (B-2) in the epoxy resin composition is too large, the pot life of the epoxy resin composition may deteriorate.

[0032] Incorporation of the compound (B-1) into 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. The epoxy resin composition may further contain a compound having three or more phenolic hydroxyl groups, which may improve the properties (heat resistance and / or tensile properties, etc.) of the cured product of the epoxy resin composition.

[0033] Examples of the compound having three or more phenolic hydroxyl groups include a compound in which one of the hydrogen atoms directly bonded to the benzene ring of the compound (B-1) is substituted with a hydroxyl group, a phenol resin, and a novolak resin.

[0034] The epoxy resin composition may also contain a compound having one phenolic hydroxyl group. Examples of the compound having one phenolic hydroxyl group include phenol, cresol, xylenol, and t-butylphenol.

[0035] The molar ratio of the phenolic hydroxyl group content to the epoxy group content in the epoxy resin composition is, for example, 0.20 or more and 0.75 or less, and from the viewpoint of improving the properties of the cured product (heat resistance and / or tensile properties, etc.), it is preferably 0.25 or more and 0.67 or less, more preferably 0.3 or more and 0.6 or less, even more preferably 0.35 or more and 0.55 or less, and still more preferably 0.4 or more and 0.5 or less.

[0036] The "epoxy group content in the epoxy resin composition" refers to the number (molar number) of epoxy groups contained in the epoxy resin (A). The "phenolic hydroxyl group content" refers to the content of phenolic hydroxyl groups in the epoxy resin composition, and refers to the total number (number of moles) of phenolic hydroxyl groups in compound (B-1) and the number (number of moles) of phenolic hydroxyl groups in phenolic compounds having phenolic hydroxyl groups other than compound (B-1).

[0037] The content of compound (B-1) in the epoxy resin composition is preferably an amount such that the molar ratio falls within the above-mentioned 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 epoxy resin (A).

[0038] From the viewpoint of the curability of the epoxy resin composition, the ratio of the content of compound (B-2) to the content of compound (B-1) in the epoxy resin composition, in terms of mass ratio, 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.

[0039] The epoxy resin composition may further contain another epoxy resin curing agent other than those described above. The other epoxy resin curing agent may be a conventionally known curing agent. However, from the viewpoints 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 still more preferably 1 part by mass or less (for example, 0 part by mass) when the total amount of the curing agent (B) is 100 parts by mass.

[0040] [3] Imidazole adduct type curing accelerator (C) In this specification, the term "curing accelerator" refers to an agent that has the function of accelerating the curing reaction. The term "accelerate" as used herein also includes the initiation of the curing reaction. In the present invention, among the curing accelerators, an imidazole adduct type curing accelerator (C) is used. The use of an imidazole adduct type curing accelerator (C) can be advantageous in achieving both the pot life and curability (fast curing, etc.) of the epoxy resin composition. This is presumably because the imidazole adduct type curing accelerator (C) can effectively initiate and / or accelerate the curing reaction between epoxy resins (A) and between epoxy resin (A) and compound (B-1) and compound (B-2), and the imidazole adduct type curing accelerator (C) generally has latency, which is advantageous in extending the pot life.

[0041] In addition, the use of the imidazole adduct type curing accelerator (C) as the curing accelerator is advantageous in that it enables the curing reaction to occur at a relatively low temperature, and is also advantageous in that it enhances the storage stability of the epoxy resin composition. The imidazole adduct curing accelerator (C) may be used alone or in combination of two or more kinds.

[0042] "Latency" refers to the property of being able to exhibit the function of promoting the curing reaction by heat, light, pressure, etc. while being able to be stored stably at room temperature (25°C) even in the presence of an epoxy resin, or in the presence of an epoxy resin and a curing agent. The imidazole adduct curing accelerator (C) used in the present invention preferably has a property (thermal latency) that allows it to exhibit a function of accelerating the curing reaction by heat.

[0043] The imidazole adduct type curing accelerator (C) is a compound in which an adduct is added to an imidazole compound. The addition of the adduct imparts latency. The adduct is, for example, a compound that can be bonded to the N atom of the imidazole ring, preferably the N atom at the 1-position, by reaction with the imidazole compound. The bond is usually a covalent bond. 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.

[0044] The imidazole adduct type curing accelerator (C) is preferably a polymer compound obtained by reacting an imidazole compound with the above-mentioned adduct. The above-mentioned adduct may be further made into a solid solution with a phenolic resin or the like, or may be surface-treated with an organic acid or a boric acid compound. The imidazole adduct type curing accelerator (C) thus produced is usually pulverized to a particle size of about 0.5 to 50 μm and dispersed in an epoxy resin for use. Since the imidazole adduct type curing accelerator (C) generally has low solubility in epoxy resins at room temperature, the imidazole adduct type curing accelerator (C) mixed with an epoxy resin often exhibits thermal latency.

[0045] The imidazole adduct type curing accelerator (C) can be produced by a method described in known patent documents, such as JP-A-59-053526, JP-A-60-004524, JP-A-60-072917, JP-A-2005-206744, JP-A-06-073156, JP-A-06-172495, JP-A-2008-214567, and JP-A-2014-177525.

[0046] As the imidazole adduct type curing accelerator (C), a commercially available product may be used. Commercially available imidazole adduct curing accelerators (C) include, by trade name, "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 Corporation); "ADEKA HARDNER EH-5011S" and "ADEKA HARDNER EH-5046S" (all manufactured by ADEKA Corporation); "Cureduct P-0505" (manufactured by Shikoku Kasei Corporation); "Amicure PN-23", "Amicure PN-23J", "Amicure PN-31", "Amicure PN-31J", "Amicure PN-40", "Amicure PN-40J", "Amicure PN-50", "Amicure PN-F", and "Amicure PN-H" (all manufactured by Ajinomoto Fine-Techno Co., Ltd.).

[0047] The epoxy resin composition may contain one or more curing accelerators other than the imidazole adduct curing accelerator (C) as long as the effects of the present invention are not impaired. The other curing accelerators are not particularly limited, and examples thereof include tertiary amine compounds and their salts, imidazole compounds (non-adduct type), imidazolium salts, phosphorus compounds such as triphenylphosphine and phosphonium salts, metal carboxylates, and 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole (TBZ).

[0048] From the viewpoint of more effectively exerting the above-mentioned effects, the content of the other curing accelerator in the curing accelerator 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) when the total amount of the curing accelerator is 100 parts by mass.

[0049] The content of the imidazole adduct 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 exerting the above-mentioned effects, the content 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, even more preferably 5 parts by mass or more and 20 parts by mass or less, and still more preferably 5 parts by mass or more and 15 parts by mass or less.

[0050] [4] Lewis acid compounds (D) The epoxy resin composition may further contain a Lewis acid compound (D) having a boron atom or an aluminum atom (hereinafter, also simply referred to as "Lewis acid compound (D)"). When the epoxy resin composition contains the Lewis acid compound (D), it becomes possible to further extend the pot life. In addition, when the epoxy resin composition contains the Lewis acid compound (D), it becomes possible to obtain a cured product of the epoxy resin composition having good properties (heat resistance and / or tensile properties, etc.) while further extending the pot life without impairing the fast curing property. The Lewis acid compound (D) is preferably in a liquid state. The meaning of "liquid state" is as described above. The epoxy resin composition may contain one or more Lewis acid compounds (D).

[0051] The Lewis acid compound (D) is a compound represented by the following formula (1). [ka]

[0052] In formula (1), X represents B (boron atom) or Al (aluminum atom). 3 , R 4 and R 5 R are each independently 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 of may be substituted with any substituent.

[0053] [ka]

[0054] In formula (2), R 6 and R 7 R are each 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 of may be substituted with any substituent.

[0055] In formula (1), R 3 , R 4 and R 5 are each 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 are each independently 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 even more preferably a linear or branched alkyl group having 2 to 8 carbon atoms or an oxyalkyl group having 1 to 8 carbon atoms.

[0056] Examples of the Lewis acid compound (D) in which X in formula (1) is B include triethyl borate, tri-n-propyl borate, tri-i-propyl borate, tri-n-butyl borate, tri-i-butyl borate, tri-sec-butyl borate, tri-t-butyl borate, tri-n-hexyl borate, and tri-n-octyl borate.

[0057] Examples of the Lewis acid compound (D) in which X in formula (1) is Al include aluminum sec-butoxide, aluminum diisopropylate monosec-butylate, aluminum ethyl acetoacetate diisopropylate, aluminum ethyl acetoacetate diisopropylate, aluminum tris(ethyl acetoacetate), aluminum monoacetylacetonate bis(ethyl acetoacetate), and aluminum stearyl acetoacetate diisopropylate.

[0058] 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, and from the viewpoint of further extending the pot life, 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 still more preferably 0.3 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the epoxy resin (A).

[0059] [5] Other ingredients The epoxy resin composition may further contain other ingredients in addition to the above-mentioned ingredients. Examples of other blending components include rubber particles, inorganic particles (particles made of metals such as aluminum, and metal compounds such as calcium carbonate and silica), flame retardants, surface treatment agents, release agents, antibacterial agents, leveling agents, defoamers, thixotropic agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, coupling agents, surfactants, metal alkoxides (not belonging to the Lewis acid compounds (D)), thermoplastic resins, diluents, barbituric acid, and the like. The other blending components may be used alone or in combination of two or more.

[0060] The addition of rubber particles makes it possible to improve toughness while maintaining good heat resistance in the cured product of the epoxy resin composition.

[0061] Examples of the rubber particles include core-shell type acrylic rubber particles, surface-modified acrylic rubber particles, crosslinked NBR particles, silicone rubber particles, etc. These rubber particles may be conventionally known. 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. The rubber particles may be used alone or in combination of two or more kinds.

[0062] The rubber particles may be commercially available, or may be a dispersion in which rubber particles are dispersed in epoxy resin in advance. Commercially available rubber particles or dispersions thereof, all under the trade name, include "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 Corporation); "Staphyloid AC" series (manufactured by Aica Kogyo Co., Ltd.); "Paraloid EXL" series (manufactured by Dow); "Metabrene" (manufactured by Mitsubishi Chemical Corporation); "XER-91" (manufactured by JSR Corporation); and "GENIOPERL P52" (manufactured by Asahi Kasei Wacker Silicone Co., Ltd.).

[0063] 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 exerting the above-mentioned effects, the content 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.

[0064] The content of the rubber particles in the epoxy resin composition is, for example, 1 mass% or more and 50 mass% or less, relative to the entire composition, and from the viewpoint of more effectively exerting the above-mentioned effects, the content is preferably 2 mass% or more and 30 mass% or less, and more preferably 2 mass% or more and 20 mass% or less.

[0065] The addition of a barbituric acid to an epoxy resin composition is advantageous in extending the pot life of the epoxy resin composition.

[0066] [6] Epoxy resin composition The epoxy resin composition according to the present invention, which contains the epoxy resin (A), the compound (B-1), the compound (B-2), the imidazole adduct type curing accelerator (C), and other components that are optionally added, is preferably in a liquid state. The meaning of "liquid state" is as described above. In a liquid epoxy resin composition, all of the components contained therein may be in a dissolved state, or one or more components may be in a dispersed state in the other components.

[0067] The liquid epoxy resin composition according to the present invention can have a low viscosity. The 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) containing a cured product of the epoxy resin composition and fibers or the like includes a step of impregnating a woven fabric or a fiber bundle with the epoxy resin composition, and the impregnation of the epoxy resin composition can be improved by using an epoxy resin composition having a low viscosity.

[0068] The viscosity of the epoxy resin composition, as measured at 25°C with 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, still 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 usually 0.01 Pa·s or more, may be 0.1 Pa·s or more, or may be 1 Pa·s or more. The viscosity of the epoxy resin composition, as measured at 25°C with an EMS viscometer, is preferably from 0.01 Pa·s to 50 Pa·s, more preferably from 0.1 Pa·s to 40 Pa·s, even more preferably from 1 Pa·s to 30 Pa·s, still more preferably from 1 Pa·s to 25 Pa·s, and particularly preferably from 1 Pa·s to 20 Pa·s.

[0069] The epoxy resin composition according to the present invention can have a long pot life. For example, the epoxy resin composition preferably has a viscosity within the above range when the composition is stored at 25°C for one day (24 hours) after preparation. In addition, the epoxy resin composition preferably has a long time until the viscosity becomes twice as large as the initial viscosity after preparation. The time until the viscosity becomes twice as large as the initial viscosity is usually about 3 days or more, preferably 5 days or more, more preferably 6 days or more, and even more preferably 7 days or more.

[0070] The epoxy resin composition according to the present invention can exhibit good curability, i.e., the epoxy resin composition can be sufficiently cured in a relatively short heat curing time and / or at a relatively low temperature.

[0071] <Cured product> The cured product according to the present invention is obtained by curing the above-mentioned epoxy resin composition according to the present invention. The cured product according to the present invention is a cured product of the above-mentioned epoxy resin composition according to the present invention, and therefore can have good heat resistance and further good tensile properties.

[0072] The cured product according to 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, or even 125° C. or higher. The cured product of the present invention may have a breaking elongation in tensile properties according to JIS K 7161-1 and JIS K 7161-2 of, for example, 4.0% or more, further 5.0% or more, further 6.0% or more, further 7.0% or more, or even 7.5% or more.

[0073] The epoxy resin composition according to the present invention and the cured product thereof have excellent heat resistance and further excellent tensile properties, and therefore can be used in various applications, for example, as an adhesive, sealing of electronic components, and a resin composition for impregnation into fibers. In addition, the epoxy resin composition according to the present invention has low viscosity and excellent impregnation properties, cures in a short time by heating (for example, 135°C, 15 minutes), and has excellent productivity, and therefore can be suitably used as a resin composition for sealing electronic components and for impregnation into fibers. The present invention also relates to a product or part containing the cured product. An example of the product is a molded product (composition) containing the cured product and fibers, etc. The product or part containing the cured product may contain components other than the epoxy resin composition-derived component (cured product), such as fibers.

[0074] The use of the epoxy resin composition according to the present invention as a resin composition for impregnation into fibers will be described below. The fibers that can be used in combination with the epoxy resin composition according to the present invention include PAN-based carbon fibers, pitch-based carbon fibers, glass fibers, aramid fibers, kenaf fibers, etc. The surfaces of the fibers may be subjected to a known sizing treatment.

[0075] A known method can be used as a method for producing a molded product by compounding the epoxy resin composition according to the present invention with fibers. Specifically, A wet filament winding method in which fibers are impregnated with an epoxy resin composition, wound around a molding die such as a mandrel, shaped, and cured by heating; A dry filament winding method in which a two-prepreg is prepared by pre-impregnating fibers with an epoxy resin composition, and the two-prepreg is wound around a molding die such as a mandrel to form the two-prepreg, and then cured by heating; A resin transfer molding method in which a fiber fabric is prepared, the fiber fabric is laminated in a mold and pressed to prepare a preform, which is then vacuum-impregnated with an epoxy resin composition and cured by heating; A sheet winding method in which a prepreg is prepared by pre-impregnating a woven fabric with an epoxy resin composition, and then the prepreg is wound around a molding die such as a mandrel to form the prepreg, and then cured by heating; A press molding method in which a prepreg is prepared by pre-impregnating a fiber fabric with an epoxy resin composition, the prepreg is laminated in a mold, and cured by heating and pressure in a press; An autoclave molding method in which a prepreg is prepared by pre-impregnating a woven fabric with an epoxy resin composition, the prepreg is placed on a molding tool, covered with a bag film, and cured under heat and pressure in an autoclave; etc.

[0076] The present invention also provides a cured product of a prepreg containing the epoxy resin composition of the present invention and a fiber. An example of the cured product of the prepreg is a cured product of a prepreg (such as a two-prepreg) in which a fiber or a woven fabric of fibers is pre-impregnated with the epoxy resin composition. The cured product may be a cured molded product as described above. EXAMPLES

[0077] 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 representing the content or amount used are based on mass unless otherwise specified.

[0078] <Examples 1 to 17 and Comparative Examples 1 to 8> (1) Preparation of epoxy resin composition Epoxy resin compositions were prepared by mixing the components shown in Tables 1 to 4 in the amounts shown in Tables 1 to 4. In Tables 1 to 4, the units for the amount of each component are parts by mass. In all of the Examples and Comparative Examples, the obtained epoxy resin compositions were liquid (had flowability at 25°C).

[0079] 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 charged amounts. In addition, the "Curing agent 2 / curing agent 1 mass ratio" column in Tables 1 to 4 shows the mass ratio of the curing agent 2 content to the curing agent 1 content in the epoxy resin composition. The rubber particles were blended by using a composition in which the rubber particles were dispersed in an epoxy resin as a blending component for preparing an epoxy resin composition.

[0080] Details of each compounding component shown in Tables 1 to 4 are as follows. [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 in which acrylic rubber particles are dispersed in an epoxy resin) manufactured by Nippon Shokubai Co., Ltd. [b] Epoxy resin 2: Liquid epoxy resin manufactured by Kookdo Chemical Co., Ltd. Product name "EPOKUKDO YD-127" (bisphenol A type epoxy resin, epoxy equivalent: 180-190g / eq, viscosity: 8-11 Pa·s (25°C)) [c] Epoxy resin 3: Liquid epoxy resin manufactured by ADEKA Corporation, product name "ADEKA RESIN EP-4300E" (bisphenol A type epoxy resin, epoxy equivalent: 185g / eq, viscosity: 8Pa·s (25°C)) [d] Epoxy resin 4: solid epoxy resin manufactured by Mitsubishi Chemical Corporation, product name "jER YX4000" (biphenyl type epoxy resin, epoxy equivalent: about 190g / eq, melting point: about 105°C) [e] Hardener 1: 1,3-dihydroxybenzene (resorcinol) [f] Hardener 2: Dihydrocoumarin [g] Curing accelerator 1: Imidazole adduct type curing accelerator manufactured by T&K TOKA Corporation, product name "Fujicure FXR-1121" (latent) [h] Curing accelerator 2: Imidazole adduct type curing accelerator manufactured by ADEKA Corporation, product name "ADEKA Hardener EH-5011S" (latent) [i] Curing accelerator 3: Imidazole type curing accelerator manufactured by ADEKA Corporation, product name "ADEKA Hardener EH-4344" (latent) [j] Curing accelerator 4: Imidazole type curing accelerator manufactured by ADEKA Corporation, product name "ADEKA Hardener EH-5046" (latent) [k] Curing accelerator 5: Imidazole type curing accelerator manufactured by T&K TOKA Corporation, product name "Fujicure FXR-1171" (latent) [l] Rubber particles: acrylic rubber particles contained in the product name "Acryset BP-328" manufactured by Nippon Shokubai Co., Ltd. (a composition in which acrylic rubber particles are dispersed in the above product name "jER828", which is an epoxy resin) [m] Lewis acid compound 1: Triethylborate [n] Lewis acid compound 2: Tri-i-propyl borate [o]Lewis acid compound 3: Tri-n-butylborate [p] Lewis acid compound 4: Tri-n-octylborate [q] Lewis acid compound 5: Aluminum ethyl acetoacetate diisopropylate (r)Lewis acid compound 6: Aluminum sec-butoxide

[0081] (2) Evaluation of epoxy resin compositions and their cured products (2-1) Viscosity and pot life of epoxy resin composition Immediately after preparation and for each of the epoxy resin compositions stored in a 25°C thermostatic chamber for a predetermined period after preparation, approximately 2 g of the epoxy resin composition was sealed in a sample tube together with a 4.7 mm aluminum spherical probe. The test tube was set in an EMS viscometer (EMS-1000) manufactured by Kyoto Electronics Manufacturing Co., Ltd., set at 25°C, and the viscosity of the epoxy resin composition was measured under the conditions of a motor rotation 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 no measurement was performed. The pot life can be evaluated from the increase in viscosity over the storage period.

[0082] (2-2) Curability of epoxy resin composition The epoxy resin composition was poured into a silicone mold heated to 135° C. and held at the same temperature for 15 minutes to carry out a curing reaction of the epoxy resin composition layer. After the curing reaction, the silicone mold was tilted and visually inspected for the occurrence of dripping, and the curability (fast curing ability) of the epoxy resin composition was evaluated according to the following evaluation criteria. The results are shown in Tables 1 to 4. A: No dripping occurred, the epoxy resin composition layer after the curing reaction was sufficiently cured, and the epoxy resin composition has fast curing properties. B: Since dripping occurred, the curing of the epoxy resin composition layer after the curing reaction was insufficient, and the epoxy resin composition did not have fast curing properties.

[0083] (2-3) Glass transition temperature (Tg) of the cured product The epoxy resin composition was poured into a silicone mold heated to 135° C. and held at the same temperature for 15 minutes to carry out a curing reaction of the epoxy resin composition layer. About 40 mg of the obtained cured epoxy resin composition was weighed into an aluminum cell, 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. The sample was heated from 25°C to 135°C at a heating rate of 15°C / min, held at 135°C for 20 minutes, cooled from 135°C to 30°C at a heating rate of -10°C / min, and then heated again from 30°C to 200°C at a heating rate of 10°C / min. The midpoint of the stepwise change in the DSC curve observed when the sample was heated was taken as Tg (°C).

[0084] (2-4) Breaking elongation of the cured product For the cured product of the epoxy resin composition, the breaking elongation in the tensile properties was measured in accordance with JIS K 7161-1 and JIS K 7161-2. Specifically, the epoxy resin composition was poured into a silicone mold and cured under the same temperature conditions as in (2-2) above to obtain a dumbbell test piece conforming to JIS K 7139A-2. Tensile tests were performed on the obtained test pieces at a speed of 10 mm / min in accordance with JIS K 7161-1 and JIS K 7161-2 using an autograph (AGX-10kNXplus) manufactured by Shimadzu Corporation. The results are shown in Tables 1 to 4. In measuring the breaking elongation, the gauge length was calculated using a video type non-contact extensometer (TRView).

[0085] (2-5) Fracture toughness of hardened material The fracture toughness K of the cured epoxy resin composition having a thickness of 6 mm was measured in accordance with ASTM D5045-14. 1C was measured. Specifically, the epoxy resin composition was poured into a silicone mold and cured under the same temperature conditions as in (2-2) above to obtain a 6 mm x 150 mm x 150 mm cured product. A 6 mm x 60 mm x 12 mm test piece was cut from this cured product, and notched with a 30°t1.0 isometric slicer blade, followed by pre-crack processing. The test pieces after the pre-crack processing were subjected to a bending test at a speed of 1 mm / min in accordance with ASTM D5045-14 using an Instron universal material testing machine (Model 5966) to measure the breaking load. In addition, test pieces measuring 6 mm x 150 mm x 12 mm were prepared from the above-mentioned 6 mm x 150 mm x 150 mm cured product by cutting, and after notching with a 30°t1.0 isometric slicing blade, pre-crack processing was performed. The test pieces after the pre-crack processing were subjected to a bending test at a speed of 2.6 mm / min using an Instron Universal Material Testing Machine Model 5966, and the 0.2% yield strength was measured. The 0.2% yield strength of the bending test was used as the yield stress, and the fracture toughness K 1C (MPa m 1 / 2 The results are shown in Tables 3 and 4. Fracture toughness K 1C The measurements were carried out for Examples 8 to 10 and 14.

[0086] [Table 1]

[0087]

Table 2

[0088]

Table 3

[0089]

Table 4

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) is represented by the following formula (B-1): 【Chemistry 1】 [In the formula, R １ represents a hydrogen atom, a halogen atom, a methoxy group, or a hydrocarbon group having 1 to 12 carbon atoms. and a compound (B-1) represented by the following formula (B-2): 【Chemistry 2】 [In the formula, R ２ represents a hydrogen atom, a halogen atom, a methyl group, or a methoxy group. and a compound (B-2) represented by the formula: the content of the compound (B-1) is 1 part by mass or more and 30 parts by mass or less based on 100 parts by mass of the epoxy resin (A), The content of the compound (B-2) is 2 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the epoxy resin (A).

2. 2. The epoxy resin composition according to claim 1, wherein a molar ratio of a phenolic hydroxyl group content to an 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 based on 100 parts by mass of the epoxy resin (A).

4. The epoxy resin composition according to any one of claims 1 to 3, wherein a ratio of a content of the compound (B-2) to a content of the compound (B-1) is 0.20 or more and 0.95 or less in terms of a mass ratio.

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

6. 6. The epoxy resin composition according to claim 1, further comprising (D) a Lewis acid compound having a boron atom or an aluminum atom.

7. A cured product of the epoxy resin composition according to any one of claims 1 to 6.

8. 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 any one of claims 1 to 6 and fibers.

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