Epoxy resin mixture, epoxy resin composition, resin sheet, prepreg and carbon fiber reinforced composite material

Abstract

The present invention provides an epoxy resin mixture, an epoxy resin composition, a resin sheet, a prepreg and a carbon fiber reinforced composite material. An epoxy resin mixture contains an epoxy resin represented by the following formula (1) and an epoxy resin represented by the following formula (2) in a weight ratio of 1:5 to 1:0.2. (In formula (1), there are multiple R1s that exist independently and represent hydrogen atoms or alkyl groups with 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.) (In formula (2), there are multiple R2s and R3s that exist independently and represent hydrogen atoms or alkyl groups with 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.)#imgabs0#

Description

Technical Field

[0001] The present invention relates to an epoxy resin mixture, an epoxy resin composition, a resin sheet, a prepreg and a carbon fiber reinforced composite material suitable for a carbon fiber reinforced composite material, a prepreg using the same, and a carbon fiber reinforced composite material obtained by curing the prepreg. Background Art

[0002] Epoxy resin is hardened by various hardeners to form a hardened material with excellent mechanical properties, water resistance, chemical resistance, heat resistance, electrical properties, etc., and is used in a wide range of fields such as adhesives, coatings, laminates, molding materials, and casting materials. Carbon fiber reinforced plastic (CFRP), which is formed by impregnating epoxy resin and hardener into reinforcing fibers and hardening them, has been widely used in aircraft structural components, windmill blades, automobile outer panels, integrated circuit (IC) trays, notebook computer frames (covers), etc. in recent years due to its lightweight / high strength characteristics. The demand for it is gradually increasing. In particular, epoxy resin is used in the matrix resin for aircraft applications by utilizing the lightweight and high strength characteristics of its molded body.

[0003] Generally speaking, the resin used in the matrix resin of CFRP etc. includes bisphenol A epoxy resin, bisphenol F epoxy resin, tetraglycidyl (diaminodiphenylmethane) etc. In addition, glycidylamine epoxy resin such as tetraglycidyl (diaminodiphenylmethane) etc. is used in aircraft applications.

[0004] In recent years, with the expansion of CFRP, the required properties of the matrix resin have become stricter. When used in aerospace applications or structural materials for vehicles, heat resistance of more than 180°C is required (Patent Document 1). Glycidylamine-based materials have high heat resistance, but have high water absorption, and there is a problem of deterioration of properties after water absorption. On the other hand, the water absorption of conventional glycidyl ether-type epoxy resins is relatively low, but there is a problem of low elastic modulus. Therefore, a material that satisfies high heat resistance, high elastic modulus, high strength, and low water absorption is sought.

[0005] As one of the conventionally known epoxy resins, there is an epoxy resin made of naphthol novolac (Patent Document 2). However, this epoxy resin has a high melt viscosity and high viscosity, so when impregnated into a carbon fiber composite material, the resin cannot be impregnated into all parts of the carbon fiber and becomes an uneven prepreg, which causes a decrease in the mechanical strength of the carbon fiber composite material.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2016 / 204173

[0009] Patent Document 2: Japanese Patent Publication No. 62-20206 Summary of the invention

[0010] Problems to be solved by the invention

[0011] Generally, as a method for reducing the melt viscosity of epoxy resins, there is a method of adding a second epoxy resin. As representative epoxy resins, bisphenol F epoxy resin and bisphenol A epoxy resin, which are liquid epoxy resins, have been studied. However, although the melt viscosity of the epoxy resin after mixing can be reduced in the case of liquid epoxy resins, the heat resistance of the cured product is reduced, so it cannot be used as a carbon fiber composite material used in aerospace applications or vehicles. In addition, although the method of adding an epoxy resin with a small molecular weight such as an epoxy resin of 4,4'-biphenyl or an epoxy resin of tetramethylbiphenyl can reduce the melt viscosity after mixing, it will cause the elastic modulus of the cured product to decrease, resulting in a decrease in the mechanical strength of the carbon fiber composite material.

[0012] In view of the above problems, an object of the present invention is to provide an epoxy resin mixture, an epoxy resin composition, a prepreg, a resin sheet, and a carbon fiber reinforced composite material, wherein the epoxy resin mixture has a low melt viscosity and its cured product has high heat resistance, high elastic modulus, and excellent low water absorption.

[0013] Technical means of solving problems

[0014] The inventors of the present invention have conducted diligent research and found that a cured product of a mixture of a cresol novolac epoxy resin and a naphthol cresol epoxy resin having a specific structure has high heat resistance, high elastic modulus, high strength, low water absorption, and excellent flame retardancy, thereby completing the present invention.

[0015] That is, the present invention is as shown in the following [1] to [8]. [1]

[0017] An epoxy resin mixture contains an epoxy resin represented by the following formula (1) and an epoxy resin represented by the following formula (2) at a weight ratio of 1:5 to 1:0.2.

[0018]

[0019] (In formula (1), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.)

[0020]

[0021] (In formula (2), plural R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.) [2]

[0023] The epoxy resin mixture according to the aforementioned item [1] is obtained by reacting a phenol resin represented by the following formula (3) and a phenol resin represented by the following formula (4) with an epihalohydrin.

[0024]

[0025] (In formula (3), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10.)

[0026]

[0027] (In formula (4), a plurality of R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10.) [3]

[0029] An epoxy resin composition comprising the epoxy resin mixture according to the above item [1] or [2] and a hardener. [4]

[0031] The epoxy resin composition according to the above item [3], wherein the hardener is an amine hardener. [5]

[0033] The epoxy resin composition according to the above item [3] or [4], which is used for a carbon fiber reinforced composite material. [6]

[0035] A resin sheet obtained by applying the epoxy resin composition according to any one of the above items [3] to [5] onto a supporting substrate. [7]

[0037] A prepreg obtained by impregnating carbon fibers with the epoxy resin composition according to any one of the above items [3] to [5] or the resin sheet according to the above item [6]. [8]

[0039] A carbon fiber reinforced composite material is obtained by hardening the prepreg described in the above item [7].

[0040] Effects of the Invention

[0041] According to the present invention, there are provided an epoxy resin mixture, an epoxy resin composition, a resin sheet, a prepreg, and a carbon fiber reinforced composite material, the cured product of which has a high elastic modulus. DETAILED DESCRIPTION

[0042] The epoxy resin mixture of the present invention contains an epoxy resin represented by the following formula (1) and an epoxy resin represented by the following formula (2).

[0043]

[0044] (In formula (1), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.)

[0045] In formula (1), R1 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. The substitution position is preferably normal or para relative to the OH group, and particularly preferably para.

[0046] When the substitution position is the para position, when reacting with a curing agent, a structure in which the network of the cured product is densely filled is formed, and the bending modulus becomes high, which is preferred.

[0047] In formula (1), n ​​is a real number of 1 to 10, preferably a real number of 1 to 8, and more preferably a real number of 2 to 6. The value of n can be calculated from the weight average molecular weight (Mw) of the olefin compound measured by gel permeation chromatography (GPC).

[0048]

[0049] (In formula (2), plural R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10. G represents a substituted or unsubstituted glycidyl group.)

[0050] In formula (2), R2 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

[0051] In formula (2), as the raw material naphthol, α-naphthol and β-naphthol can be used, and α-naphthol is preferred. When β-naphthol is used as a resin raw material, the β-naphthol part will dissociate by high temperature heating to form a β-naphthol dimer, resulting in reduced heat resistance, which is not preferred.

[0052] In formula (2), R3 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group. The substitution position is preferably normal or para relative to the OH group, and particularly preferably para.

[0053] When the substitution position is the para position, when reacting with a curing agent, a structure in which the network of the cured product is densely filled is formed, and the bending modulus becomes high, which is preferable.

[0054] In formula (2), n is a real number of 1-10, preferably a real number of 1-6, and more preferably a real number of 1-4.

[0055] The epoxy resin represented by the formula (1) can be obtained by reacting a phenol resin represented by the following formula (3) with an epihalohydrin.

[0056]

[0057] (In formula (3), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10.)

[0058] The preferred ranges of R1 and n in formula (3) are the same as those in formula (1).

[0059] In formula (3), in the measurement by gel permeation chromatography (GPC), the component represented by n=1 (binucleides) is usually less than 10 area%. The lower limit may be 0 area%, but the preferred lower limit is 1 area% or more, and more preferably 2 area% or more. In addition, the preferred upper limit is less than 8 area%, and more preferably less than 6 area%.

[0060] In formula (3), the increase in the component represented by n=1 makes the epoxy resin formed by the reaction with epihalohydrin excellent in melt viscosity, but the heat resistance of the cured epoxy resin decreases due to the increase in the difunctional component. On the other hand, if it is less than 10 area %, the multifunctional component increases relatively, so the heat resistance of the cured epoxy resin increases.

[0061] In formula (3), in gel permeation chromatography (GPC) analysis, the component represented by n=2 (trinuclear body) is usually 1 area % or more and less than 60 area %, preferably 10 area % or more and less than 50 area %, and more preferably 20 area % or more and less than 40 area %.

[0062] In formula (3), when the component represented by n=2 is 1 area % or more, the viscosity is appropriate, so the workability is improved. On the other hand, when it is less than 40 area %, the heat resistance is improved.

[0063] In formula (3), in the measurement by gel permeation chromatography (GPC), the total content of the component represented by n = 1 (binuclear body) and the component represented by n = 3 (tetranuclear body) is usually 1 area % or more and less than 20 area %. The preferred lower limit is 5 area % or more, and more preferably 10 area % or more. In addition, the preferred upper limit is less than 18 area %.

[0064] In formula (3), when the total content of the components represented by n=1 and n=3 is 1 area % or more, there are many low molecular weight components, so the melt viscosity of the resin is excellent. In addition, since the n=3 component is multifunctional, the heat resistance of the cured epoxy resin becomes high. On the other hand, if it is less than 20 area %, the melt viscosity of the resin does not become too high, and the cured epoxy resin shows high heat resistance.

[0065] In formula (3), in the measurement by gel permeation chromatography (GPC), the total content of the component represented by n = 2 (trinuclear body) and the component represented by n = 4 (pentanuclear body) is usually 10 area % or more and less than 80 area %. The preferred lower limit is 25 area % or more, and more preferably 30 area % or more. In addition, the preferred upper limit is less than 70 area %.

[0066] In formula (3), if the total content of the components represented by n=2 and n=4 is 10 area % or more, the low molecular weight components increase, so the melt viscosity of the resin is excellent. In addition, since the n=4 component is multifunctional, the heat resistance of the cured epoxy resin becomes high. On the other hand, if it is less than 80 area %, the melt viscosity of the resin does not become too high, and the cured epoxy resin shows high heat resistance.

[0067] In addition, GPC analysis was performed under the following conditions.

[0068] In the present invention, GPC analysis is performed under the following conditions.

[0069] [Various conditions for GPC]

[0070] Manufacturer: Waters

[0071] Column: Guard column SHODEX GPC KF-601 (two) KF-602 KF-602.5 KF-603

[0072] Flow rate: 1.23ml / min.

[0073] Column temperature: 25℃

[0074] Solvent used: Tetrahydrofuran (THF)

[0075] Detector: RI (refractive index) (differential refractometer)

[0076] The epoxy resin represented by the formula (2) can be obtained by reacting a phenol resin represented by the following formula (4) with an epihalohydrin.

[0077]

[0078] (In formula (4), a plurality of R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents a real number of 1 to 10.)

[0079] The preferred ranges of R2, R3 and n in formula (4) are the same as those in formula (2).

[0080] The epoxy resin mixture of the present invention contains the epoxy resin represented by the formula (1) (hereinafter also referred to as "component A") and the epoxy resin represented by the formula (2) (hereinafter also referred to as "component B") in a weight ratio of 1:5 to 1:0.2, preferably a ratio of 1:5 to 1:0.2, more preferably a ratio of 1:3 to 1:0.5, and particularly preferably a ratio of 1:2 to 1:1. If the amount of component A is small, the viscosity becomes high and it becomes difficult to handle. If the amount of component B is small, the heat resistance decreases. The ratio of component A to component B can be used to adjust the epoxy resin mixture to a viscosity suitable for the process. When the epoxy resin mixture is used as the matrix resin of the prepreg of CFRP, a prepreg with excellent viscosity can be produced by increasing the amount of component A added.

[0081] The epoxy equivalent of the epoxy resin mixture of the present invention is preferably 200 to 300 g / eq., more preferably 205 to 260 g / eq., and further preferably 210 to 240 g / eq. When the epoxy equivalent is within the above range, the amount of epoxy groups per unit structure becomes appropriate, which is preferred in terms of heat resistance.

[0082] The epoxy resin mixture of the present invention has a resinous form, and this form has a softening point. Here, as the softening point, it is preferably 60°C to 120°C, more preferably 70°C to 110°C, and further preferably 80°C to 100°C. If the softening point is above 60°C, it means that the molecular weight distribution becomes appropriate, or there is no residue of solvent, etc., the heat resistance becomes good, and problems such as poor hardening and voids during molding can be suppressed. On the contrary, if the softening point is below 100°C, the operation when mixing with other resins becomes good.

[0083] In addition, the melt viscosity is preferably 0.2 Pa·s to 1.0 Pa·s (ICI melt viscosity (150°C) cone and plate method), more preferably 0.3 Pa·s to 0.8 Pa·s, and further preferably 0.4 Pa·s to 0.6 Pa·s. When the viscosity is 0.2 Pa·s or more, an appropriate molecular weight distribution is formed, and the solubility in the solvent is good. On the contrary, when the melt viscosity is 1.0 Pa·s or less, the operation when kneading with other resins becomes good.

[0084] Next, the reaction for obtaining the epoxy resin mixture of the present invention will be described.

[0085] The epoxy resin mixture of the present invention can be obtained by mixing component A obtained by reacting a phenol resin represented by formula (3) with an epihalohydrin and component B obtained by reacting a phenol resin represented by formula (4) with an epihalohydrin; or by mixing a phenol resin represented by formula (3) and a phenol resin represented by formula (4) and reacting the mixture with an epihalohydrin.

[0086] As a method for mixing the above-mentioned component A and component B, two methods are generally mentioned: (a) melt mixing and (b) solution mixing.

[0087] In the case of (a) melt mixing, component A and component B can be melted at 50°C to 200°C to form a uniform mixture. At this time, if the temperature is low, the mixing will be uneven, and it is likely to become a sticky resin composition or a resin composition with component bleeding, which is not preferred. In addition, when the treatment is performed at 200°C or above, it is preferred to perform the treatment under reduced pressure and / or in the presence of an inert gas such as nitrogen.

[0088] In the case of solution mixing (b), it is preferred that component A and component B are uniformly dissolved in an organic solvent (C1-C6 ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone; C1-C6 esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ester; C1-C10 hydrocarbons such as toluene, xylene; C1-C6 ethers such as tetrahydrofuran, dioxane, propylene glycol monomethyl ether) at 50°C to 200°C, and then the solvent is distilled off under heating and reduced pressure to obtain a mixture.

[0089] In either case, the epoxy resin mixture is obtained by dropping a uniform epoxy resin mixture onto a surface support (steel belt, drum chipper, etc.) cooled to 0 to 100° C. The shape is preferably a flake shape or a marble shape with a diameter of 1 to 20 mm.

[0090] The epihalohydrin used in the epoxidation reaction is easily available on the market. The amount of epihalohydrin used is usually 3.5 to 10 mol, preferably 4.0 to 8.0 mol, and more preferably 4.5 to 7.0 mol, per 1 mol of hydroxyl groups in the raw material phenol mixture.

[0091] In addition, an alkali metal hydroxide can be used as a catalyst to promote the epoxidation reaction. As usable alkali metal hydroxides, sodium hydroxide, potassium hydroxide, etc. can be listed, and solid forms or aqueous solutions thereof can be used. In the present invention, in particular, in terms of solubility and handling, it is preferred to use solid forms formed into flakes.

[0092] The amount of alkali metal hydroxide used is generally 0.90 to 1.5 moles, preferably 0.95 to 1.25 moles, and more preferably 0.99 to 1.15 moles, relative to 1 mole of hydroxyl groups in the raw material phenol mixture. The reaction temperature at this time is generally 30°C to 90°C, preferably 35°C to 80°C. In particular, in the present invention, for higher purity epoxidation, it is preferably above 60°C, especially above 65°C, and further preferably a reaction under conditions close to reflux conditions. The reaction time is generally 0.5 to 10 hours, preferably 1 to 8 hours, and particularly preferably 1 to 3 hours. If the reaction time is short, the reaction cannot be fully carried out, and if the reaction time becomes long, by-products will be formed, so it is not preferred.

[0093] In addition, by first adding a part of alkali metal hydroxide and reacting it, epihalohydrin and phenolic resin can be urged to carry out addition reaction and generate chlorohydrin.Preferred addition at this moment is generally 0.01 mole~0.7 mole relative to 1 mole of hydroxyl of raw material phenol mixture, is preferably 0.05 mole~0.5 mole, more preferably 0.10 mole~0.30 mole.If the amount of alkali metal hydroxide is few, then reaction will not be carried out, if the amount of alkali metal hydroxide is too much, then reaction is carried out sharply, promotes the high molecular weight of resin and is not preferred.In addition, because sharp exothermic reaction can occur and dangerous, it is not preferred industrially.

[0094] The reaction temperature at this time is usually 30°C to 90°C, preferably 35°C to 80°C. In particular, in the present invention, for higher purity epoxidation, it is preferably 60°C or higher, particularly preferably 65°C or higher. The reaction time is usually 0.5 hours to 10 hours, preferably 1 hour to 8 hours, particularly preferably 1 hour to 3 hours. If the reaction time is short, the reaction cannot be fully carried out, and if the reaction time is long, by-products will be formed, so it is not preferred.

[0095] In addition, in order to promote the reaction, a non-protonic polar solvent such as dimethylformamide and dimethyl sulfoxide; a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide, trimethylbenzylammonium chloride, etc. may be added as a catalyst. The amount of the quaternary ammonium salt used is usually 0.1 g to 15 g, preferably 0.2 g to 10 g, relative to 1 mol of the hydroxyl group of the raw material phenol mixture.

[0096] After washing the reaction products of these epoxidation reactions, or without washing, epihalohydrin, solvent, etc. are removed under heating and reduced pressure. In addition, in order to make an epoxy resin with less hydrolyzable halogen, a ketone compound of 4 to 7 carbon atoms (for example, methyl isobutyl ketone, methyl ethyl ketone, cyclopentanone, cyclohexanone, etc.) can also be used as a solvent to dissolve the recovered epoxy resin, and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide and potassium hydroxide is added to react to make the closed loop reliable. In this case, the amount of the alkali metal hydroxide used is usually 0.01 mole to 0.3 mole relative to 1 mole of the hydroxyl group of the raw material phenol mixture used in the epoxidation, preferably 0.05 mole to 0.2 mole. The reaction temperature is usually 50°C to 120°C, and the reaction time is usually 0.5 hour to 2 hours.

[0097] After the reaction is completed, the generated salt is removed by filtration, washing with water, etc., and the solvent is further distilled off under heating and reduced pressure to obtain the epoxy resin mixture of the present invention.

[0098] The epoxy resin mixture of the present invention obtained in this way has excellent bending elastic modulus, heat resistance and low water absorption. The bending elastic modulus is preferably 3.2GPa to 3.8GPa, more preferably 3.3GPa to 3.7GPa, and particularly preferably 3.4GPa to 3.6GPa. If the bending elastic modulus is more than 3.2GPa, the required mechanical strength can be obtained when the carbon fiber composite material is made, so it becomes a material that can also withstand reliability tests. In addition, if the bending elastic modulus is less than 3.8GPa, it becomes a tough material, so it is not easy to break, and it becomes a material that can also withstand reliability tests.

[0099] The heat resistance (Tg) is preferably 180°C to 300°C, more preferably 190°C to 270°C, and particularly preferably 200°C to 250°C. If the heat resistance is above 180°C, the resin will not soften even when applied to components such as the periphery of an aircraft engine, and high mechanical strength can be maintained. In addition, the heat resistance of epoxy resin is generally related to the crosslinking density, so when the heat resistance is too high, the crosslinking density becomes too high, and the mechanical strength of the hardened material sometimes becomes brittle, so the heat resistance is preferably below 300°C.

[0100] Regarding the water absorption, the weight increase rate after boiling in water at 100°C for 72 hours is preferably 0.5% to 1.5%, more preferably 0.7% to 1.4%, and particularly preferably 0.9% to 1.3%. The lower the water absorption, the better. However, generally speaking, epoxy resins that show low water absorption often have many alkyl groups in their skeletons, and the cured product tends to become brittle. Therefore, the water absorption is preferably 0.5% or more. In addition, if the water absorption is too high, the cured product absorbs water and the material softens significantly, reducing the mechanical strength. Therefore, the water absorption is preferably 1.5% or less.

[0101] The epoxy resin composition of the present invention contains a curing agent. Examples of the curing agent that can be used include amine curing agents, acid anhydride curing agents, amide curing agents, and phenol curing agents.

[0102] In the epoxy resin composition of the present invention, in particular, in order to achieve a balanced balance between low linear expansion of the epoxy resin composition and heat resistance of the cured resin, an amine curing agent is preferred. In particular, from the viewpoint of strength and heat resistance, aniline novolac, o-ethylaniline novolac, aniline resin obtained by reaction of aniline with xylylene chloride, aniline resin obtained by polycondensation of aniline with substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, etc.) are preferred.

[0103] Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, pyromellitic dianhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0104] Examples of the amide-based curing agent include dicyandiamide and polyamide resins synthesized from a dimer of linolenic acid and ethylenediamine.

[0105] Examples of the phenolic curing agent include polyphenols (bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, terpene diphenol, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 3,3',5,5'-tetramethyl-(1,1'-biphenyl)-4,4'-diol, hydroquinone, resorcinol, naphthalene diol, tris-(4-hydroxyphenyl)methane and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane); phenols (e.g., phenol, alkyl-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene and dihydroxynaphthalene) with aldehydes (formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, o-hydroxybenzaldehyde and furfural), ketones (p-hydroxybenzene) Phenolic resins obtained by condensation of the phenols with substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, etc.); modified products of the phenols and / or the phenol resins; halogenated phenols such as tetrabromobisphenol A and brominated phenol resins.

[0106] In the epoxy resin composition of the present invention, the amount of the curing agent used is preferably 0.7 to 1.2 equivalents per 1 equivalent of the epoxy group of the epoxy resin. If the amount is less than 0.7 equivalents or exceeds 1.2 equivalents per 1 equivalent of the epoxy group, there is a concern that curing may be incomplete and good curing properties may not be obtained.

[0107] In addition, in the epoxy resin composition of the present invention, a hardening accelerator may be formulated as needed. The gelation time may also be adjusted by using a hardening accelerator. Examples of hardening accelerators that can be used include: imidazoles such as 2-methylimidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole; tertiary amines such as 2-(dimethylaminomethyl)phenol and 1,8-diaza-bicyclo(5,4,0)undecene-7; phosphines such as triphenylphosphine; and metal compounds such as tin octanoate. The hardening accelerator may be used in an amount of 0.01 to 5.0 parts by weight relative to 100 parts by weight of the epoxy resin as needed.

[0108] In the epoxy resin composition of the present invention, other epoxy resins may be formulated in addition to component A and component B. Specific examples thereof include polycondensates of phenols (phenol, alkyl-substituted phenol, aromatic-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, dihydroxynaphthalene, etc.) and various aldehydes (formaldehyde, acetaldehyde, alkyl aldehydes, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthaldehyde, glutaraldehyde, o-phthalaldehyde, crotonaldehyde, cinnamaldehyde, etc.); polymers of phenols and various diene compounds (dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinyl norbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, etc.); polymers of phenols and ketones (acetone, methyl ethyl ketone, polycondensates of phenols and substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene and 1,4-bis(hydroxymethyl)benzene, etc.); polycondensates of bisphenols and various aldehydes; glycidyl ether epoxy resins obtained by glycidylating alcohols; alicyclic epoxy resins represented by 4-vinyl-1-cyclohexene diepoxide or 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate; tetraglycidyldiaminodiphenylmethane (tetraglycidyldiaminodiphenylmethane) The epoxy resins include glycidylamine epoxy resins represented by triglycidyl-p-aminophenol and the like; glycidyl ester epoxy resins, but are not limited to these as long as they are commonly used epoxy resins.

[0109] When component A, component B and other epoxy resins are used in combination, the total amount of component A and component B in the total amount of epoxy resin is preferably 30% by weight or more, particularly preferably 40% by weight or more. If the total amount of component A and component B is less than 30% by weight, physical properties such as high heat resistance, high elastic modulus, and low water absorption cannot be obtained.

[0110] Furthermore, the epoxy resin composition of the present invention may be mixed with known additives as needed. Specific examples of usable additives include: polybutadiene and modified products thereof, modified products of acrylonitrile copolymers, polyphenylene ether, polystyrene, polyethylene, polyimide, fluororesin, maleimide compounds, cyanate compounds, silicone gel, silicone oil, and inorganic fillers such as silicon dioxide, aluminum oxide, calcium carbonate, quartz powder, aluminum powder, graphite, talc, clay, iron oxide, titanium oxide, aluminum nitride, asbestos, mica, and glass powder, surface treatment agents for fillers such as silane coupling agents, mold release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0111] In the epoxy resin composition of the present invention, known maleimide compounds can be deployed as needed. As specific examples of usable maleimide compounds, 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, metaphenylene bismaleimide, 2,2'-bis〔4-(4-maleimide phenoxy) phenyl〕propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenyl sulfone bismaleimide, 1,3-bis(3-maleimide phenoxy) benzene, 1,3-bis(4-maleimide phenoxy) benzene, etc. can be cited, but are not limited to these. These can be used alone or in combination of two or more. When the maleimide compound is prepared, a curing accelerator is prepared as necessary. The above-mentioned curing accelerator or a radical polymerization initiator such as an organic peroxide or an azo compound can be used.

[0112] An organic solvent can be added to the epoxy resin composition of the present invention to prepare a varnish-like composition (hereinafter referred to as varnish). Examples of the solvent used include: γ-butyrolactones; amide solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidinone; sulfones such as tetramethylene sulfone; ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, and propylene glycol monobutyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; and aromatic solvents such as toluene and xylene. The solvent is usually used in a range of 10% to 80% by weight, preferably 20% to 70% by weight, of the solid content concentration excluding the solvent in the obtained varnish.

[0113] Next, the resin sheet, prepreg, and carbon fiber reinforced composite material of the present invention will be described.

[0114] The epoxy resin composition of the present invention can be applied to one or both sides of a supporting substrate and used as a resin sheet. As a coating method, for example, a casting method; a method of extruding a resin from a nozzle or a die using a pump or an extruder and adjusting the thickness using a scraper; a method of adjusting the thickness by calendering with a roller; a method of spraying using a sprayer, etc. In addition, in the process of forming a layer, it is also possible to heat while being carried out within a temperature range that can avoid thermal decomposition of the epoxy resin composition. In addition, calendering treatment, grinding treatment, etc. may also be implemented as needed. As a supporting substrate, for example, a porous substrate including paper, cloth, non-woven fabric, etc., a plastic film or sheet such as a polyethylene film, a polypropylene film, a polyethylene terephthalate film, a polyester film, a mesh fabric, a foam, a metal foil, and a laminate thereof, etc., can be cited, but it is not limited to these. The thickness in the supporting substrate is not particularly limited and can be appropriately determined according to the purpose.

[0115] The prepreg of the present invention can be obtained by heating and melting the epoxy resin composition and / or the resin sheet of the present invention to reduce the viscosity and then impregnating the epoxy resin composition and / or the resin sheet into a fiber base material.

[0116] In addition, the prepreg of the present invention can also be obtained by impregnating a varnish-like epoxy resin composition into a fiber substrate and heating and drying. The prepreg is cut into a desired shape and stacked, and then, while applying pressure to the stack by a press molding method, an autoclave molding method, a sheet winding molding method, etc., the epoxy resin composition is heated and hardened, thereby obtaining the carbon fiber reinforced composite material of the present invention. In addition, copper foil or an organic film can also be stacked when the prepreg is stacked.

[0117] Furthermore, the carbon fiber reinforced composite material of the present invention can be obtained by molding using a known method other than the above method. For example, the following resin transfer molding technology (RTM (resin transfer molding) method) can also be used: a carbon fiber substrate (usually a carbon fiber fabric) is cut, stacked, and shaped to make a preform (a preformed body before impregnation with resin), the preform is arranged in a molding mold and the mold is closed, the resin is injected to impregnate the preform and harden it, and then the mold is opened to take out the molded product.

[0118] In addition, other RTM methods such as Vacuum assist Resin Transfer Molding (VaRTM), Seeman's Composite Resin Infusion Molding Process (SCRIMP), and Controlled Atmospheric Pressure Resin Infusion (CAPRI) described in Japanese Patent Table 2005-527410 may also be used. The CAPRI method involves venting the resin supply tank to a pressure lower than atmospheric pressure, using cyclic compression, and controlling the net molding pressure, thereby more appropriately controlling the resin injection process, especially the VaRTM method.

[0119] Furthermore, the following methods may also be used: a membrane stacking method in which a fiber substrate is clamped by resin sheets (films); or a method in which a powdered resin is attached to a reinforcing fiber substrate in order to improve impregnation; a forming method in which a fluidized bed or fluid slurry method is used in the process of mixing the resin with the fiber substrate (powder impregnated yarn); or a method in which resin fibers are interwoven into a fiber substrate.

[0120] As carbon fiber, acrylic, pitch, rayon and other carbon fibers can be cited, among which acrylic carbon fibers with high tensile strength can be preferably used. As the form of carbon fiber, twisted yarn, untwisted yarn and untwisted yarn can be used, but untwisted yarn or untwisted yarn can be preferably used for the purpose of good balance between the formability and strength characteristics of carbon fiber reinforced composite materials.

[0121] Example

[0122] Below, enumerate synthesis example and embodiment to further illustrate the present invention.As long as do not depart from the gist of the present invention, the material, processing content, processing steps etc. represented below can be appropriately changed.Therefore, the scope of the present invention should not be subject to the specific example restrictive interpretation represented below.

[0123] Various analytical methods used in Examples are described below.

[0124] Epoxy equivalent

[0125] The measurement was performed by the method described in Japanese Industrial Standards (JIS) K-7236, and the unit is g / eq.

[0126] Softening point

[0127] The temperature was measured by a method in accordance with JIS K-7234, and the unit is °C.

[0128] GPC (Gel Permeation Chromatography) Analysis

[0129] Manufacturer: Waters

[0130] Column: Guard column SHODEX GPC KF-601 (two), KF-602, KF-602.5, KF-603

[0131] Flow rate: 1.23ml / min.

[0132] Column temperature: 25℃

[0133] Solvent used: THF (tetrahydrofuran)

[0134] Detector: RI (differential refractometer)

[0135] [Synthesis example 1]

[0136] 216 parts (2 mol) of p-cresol were placed in a four-necked flask equipped with a thermometer and a stirrer, and 400 parts (2 mol as caustic soda) of a 20% aqueous sodium hydroxide solution were added dropwise to obtain a sodium salt of p-cresol.

[0137] Next, 120 parts (4 mol) of paraformaldehyde was slowly added in an ice bath while keeping the reaction temperature at 5°C or lower. The reaction was carried out for 1 hour while keeping the reaction temperature at 5°C or lower, and then the temperature was raised to 20°C and the reaction was further carried out for 1 hour.

[0138] The obtained reaction solution was cooled, and concentrated hydrochloric acid was added dropwise while maintaining the temperature at 30°C, and pH paper was used to confirm that the solution was neutral. The reaction solution was filtered, washed with water, and then dried to obtain 300 parts of the target dimethylol compound (DM-1) (yield 89%).

[0139] [Synthesis example 2]

[0140] In a four-necked flask equipped with a thermometer and a stirrer, 378 parts (3.5 mol) of p-cresol and 2 parts (0.012 mol) of p-toluenesulfonic acid were added, and the reaction solution was maintained at 45°C using a water bath. Subsequently, under a water bath, while the reaction temperature was maintained at 45°C, 168 parts (1 mol) of DM-1 obtained in Synthesis Example 1 were slowly added. While the reaction temperature was maintained at 45°C, the reaction was carried out for 5 hours, and then the temperature was raised to 80°C and the reaction was further carried out for 1 hour. 4 parts (0.01 mol) of sodium tripolyphosphate were added to the obtained reaction solution, stirred for a few minutes and washed with water, and then pH paper was used to confirm that the system became neutral. The solution was subjected to reduced pressure distillation using a rotary evaporator, and unreacted p-cresol was recovered to obtain 290 parts of p-cresol novolac (P-1). The GPC measurement results are shown in Table 1, and the resin property evaluation results are shown in Table 2.

[0141] [Synthesis example 3]

[0142] In a four-necked flask equipped with a thermometer and a stirrer, 248 parts of p-cresol novolac (P-1), 777 parts (8.4 moles) of epichlorohydrin, 389 parts (5.0 moles) of dimethyl sulfoxide, and 78 parts of water were respectively added, and the temperature was raised to 70°C using a water bath. When the internal temperature reached 70°C, 88 parts (2.3 moles) of flaky sodium hydroxide were added in batches over 180 minutes, and the mixture was reacted at 70°C for 2 hours. The reaction solution was transferred to a separatory funnel, washed with warm water, and the resulting solution was subjected to reduced pressure distillation using a rotary evaporator to recover unreacted epichlorohydrin. The residue was dissolved in 914 parts (9.1 moles) of methyl isobutyl ketone, the solution was heated to 70°C, 25 parts (0.2 moles in terms of sodium hydroxide) of 30% by weight of sodium hydroxide solution were added, and the reaction was carried out for 1 hour. Then, the cleaning solution was washed with water until it became neutral. The obtained solution was distilled off methyl isobutyl ketone and the like by a rotary evaporator at 180°C under reduced pressure, thereby obtaining 330 g of epoxy resin (EP-1). The obtained resin had an ICI viscosity (150°C) of 0.18 Pa·s, a softening point of 74°C, and an epoxy equivalent of 226 g / eq. The results of the evaluation of the resin properties are shown in Table 2.

[0143] [Synthesis Example 4]

[0144] In a four-necked flask equipped with a thermometer and a stirrer, 280 parts of naphthol-cresol novolac resin (OCN-7000 manufactured by Minghe Chemical Co., Ltd.), 677 parts of epichlorohydrin (7.3 moles), and 8 parts of water (0.4 moles) were added respectively, and the temperature was raised to 45°C using a water bath. When it reached 45°C, 84 parts of flaky sodium hydroxide (2.1 moles) were added in batches over 90 minutes, and the mixture was reacted at 45°C for 2 hours, and then at 70°C for 1 hour. The reaction solution was transferred to a separatory funnel, washed with warm water, and the resulting solution was subjected to reduced pressure distillation using a rotary evaporator to recover unreacted epichlorohydrin. The residue was dissolved in 800 parts (8.0 moles) of methyl isobutyl ketone, the solution was heated to 70°C, 19 parts of a 30% by weight sodium hydroxide aqueous solution (0.1 mole in terms of sodium hydroxide) were added, and the reaction was carried out for 1 hour. Then, the cleaning solution was washed with water until it became neutral. The obtained solution was distilled off methyl isobutyl ketone and the like by a rotary evaporator at 180°C under reduced pressure, thereby obtaining 351 parts of epoxy resin (EP-2). The obtained resin had an ICI viscosity (150°C) of 1.3 Pa·s, a softening point of 95°C, and an epoxy equivalent of 227 g / eq. The evaluation results of the resin properties are shown in Table 2.

[0145] [Example 1]

[0146] In a four-necked flask equipped with a thermometer and a stirrer, 45 parts of EP-1 obtained in Synthesis Example 3 and 55 parts of EP-2 obtained in Synthesis Example 4 were dissolved in 200 parts of methyl isobutyl ketone, and the solution was heated to 100°C and stirred for 2 hours. The solution was visually confirmed to be uniform, and the methyl isobutyl ketone was distilled off from the obtained resin solution at 180°C under reduced pressure using a rotary evaporator, thereby obtaining 95 parts of the epoxy resin (EP-3) of the present invention. The ICI viscosity (150°C) of the obtained resin was 0.59 Pa·s, the softening point was 86°C, and the epoxy equivalent was 229 g / eq. The results of the evaluation of the resin properties are shown in Table 2.

[0147] [Example 2]

[0148] The same process as in Example 1 was used except that 40 parts of EP-1 obtained in Synthesis Example 3 and 60 parts of EP-2 obtained in Synthesis Example 4 were used, and the obtained resin solution was dissolved in 200 parts of methyl isobutyl ketone. The methyl isobutyl ketone was distilled off by a rotary evaporator to obtain 95 parts of the epoxy resin (EP-4) of the present invention. The obtained resin had an ICI viscosity (150° C.) of 0.66 Pa·s, a softening point of 87° C., and an epoxy equivalent of 229 g / eq. The results of the evaluation of the resin properties are shown in Table 2.

[0149] [Example 3]

[0150] The same process as in Example 1 was used except that 35 parts of EP-1 obtained in Synthesis Example 3 and 65 parts of EP-2 obtained in Synthesis Example 4 were used, and the obtained resin solution was dissolved in 200 parts of methyl isobutyl ketone. The methyl isobutyl ketone was distilled off by a rotary evaporator to obtain 95 parts of the epoxy resin (EP-5) of the present invention. The ICI viscosity (150°C) of the obtained resin was 0.69 Pa·s, the softening point was 88°C, and the epoxy equivalent was 230 g / eq. The evaluation results of the resin properties are shown in Table 2.

[0151] [Example 4]

[0152] In a four-necked flask equipped with a thermometer and a stirrer, 86 parts of naphthol-cresol novolac resin (OCN-7000 manufactured by Minghe Chemical Co., Ltd.), 54 parts of p-cresol novolac (P-1) obtained in Synthesis Example 2, 415 parts (4.5 mol) of epichlorohydrin, and 8 parts (0.4 mol) of water were respectively placed, and the temperature was raised to 70°C using a water bath. When the temperature reached 70°C, 4 parts (0.1 mol) of flaky sodium hydroxide was added, and the mixture was reacted at 70°C for 2 hours. After the reaction, the reaction solution was cooled to 55°C, and 389 parts (1.6 mol) of dimethyl sulfoxide was added when the internal temperature reached 55°C. When the internal temperature was stabilized at 55°C, 41 parts (1 mol) of flaky sodium hydroxide was added in batches over 90 minutes, and the mixture was reacted at 55°C for 2 hours, and then at 70°C for 1 hour. The reaction solution was transferred to a separatory funnel, and warm water was added for washing. The obtained solution was subjected to reduced pressure distillation using a rotary evaporator to recover unreacted epichlorohydrin. The residue was dissolved in 390 parts (3.9 mol) of methyl isobutyl ketone, the solution was heated to 70°C, 11 parts (0.1 mol in terms of sodium hydroxide) of 30% by weight aqueous solution of sodium hydroxide were added, and the reaction was carried out for 1 hour. Then, the washing was carried out until the washing liquid became neutral. For the obtained solution, methyl isobutyl ketone and the like were distilled off using a rotary evaporator at 180°C and under reduced pressure, thereby obtaining 178 g of the epoxy resin (EP-6) of the present invention. The ICI viscosity (150°C) of the obtained resin was 0.50 Pa·s, the softening point was 85°C, and the epoxy equivalent was 216 g / eq. The results of the evaluation of the physical properties of the resin are shown in Table 2.

[0153] [Example 5, Example 6, Comparative Example 1 to Comparative Example 3]

[0154] The epoxy resins (EP-1, EP-2, EP-4, EP-6) obtained in Synthesis Example 3, Synthesis Example 4, Example 2, and Example 4, and o-cresol novolac type epoxy resin EOCN-104S (manufactured by Nippon Kayaku Co., Ltd., softening point 92°C, ICI viscosity (150°C) 3.0 Pa·s, epoxy equivalent 217 g / eq.) were used as the main agent, and phenol novolac (softening point 83°C, hydroxyl equivalent 106 g / eq.) as a hardener and triphenylphosphine (TPP) as a hardening accelerator were mixed in the weight ratio shown in the formulation composition of Table 3, and hardened at 160°C for 2 hours and 180°C for 6 hours.

[0155] [Example 7, Example 8, Comparative Examples 4 to 6]

[0156] The epoxy resins (EP-1, EP-2, EP-4, EP-6) obtained in Synthesis Example 3, Synthesis Example 4, Example 2, and Example 4, respectively, and dicyclopentadiene epoxy resin XD-1000 (manufactured by Nippon Kayaku Co., Ltd., softening point 73°C, ICI viscosity (150°C) 0.2 Pa·s, epoxy equivalent 253 g / eq.) were used as the main agent, and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane (abbreviation; TEDDM (3,3',5,5'-tetraethyl-4,4'-diamino diphenylmethane) as a hardener (manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent 78 g / eq.) and salicylic acid (manufactured by Junsei Chemical Co., Ltd., special grade) as a hardening accelerator were mixed in the weight ratio shown in the formulation composition of Table 4, and hardened at 160°C for 6 hours.

[0157] [Example 9]

[0158] The epoxy resin (EP-4) obtained in Example 2 was used as the main agent, and 4,4'-diaminodiphenyl sulfone (abbreviated as Seikacure S, manufactured by Wakayama Seika Industries Co., Ltd., active hydrogen equivalent 62 g / eq.) as a hardener and salicylic acid (manufactured by Junsei Chemical Co., Ltd., special grade) as a hardening accelerator were mixed in the weight ratio shown in the formulation composition of Table 5, and hardened at 160°C for 6 hours.

[0159] The physical property values ​​were measured under the following conditions.

[0160] <Heat resistance (Tg) measurement conditions>

[0161] Dynamic viscoelasticity tester: TA-Instruments, dynamic thermomechanical analyzer (DMA)-2980

[0162] Measuring temperature range: -30℃~280℃

[0163] Heating speed: 2℃ / min

[0164] Elastic modulus: storage elastic modulus at 50°C.

[0165] Tg: The peak point of Tanδ is set as Tg.

[0166] <Measurement conditions for flexural strength and flexural modulus>

[0167] ·Measured in accordance with JIS K-7074.

[0168] <Water absorption measurement conditions>

[0169] The weight of a disk-shaped test piece having a diameter of 5 cm and a thickness of 4 mm was measured before and after being boiled in water at 100° C. for 72 hours, and the increase rate (%) was defined as the water absorption rate.

[0170] [Table 1]

[0171] n＝l n＝2 n＝3 n＝4 n＝5 n=6 or more P-1[Area %] 4.7 46.0 9.7 17.5 6.7 15.5

[0172] [Table 2]

[0173]

[0174] [Table 3]

[0175]

[0176] [Table 4]

[0177]

[0178] [Table 5]

[0179]

[0180] According to the results of Tables 3 to 5, it was confirmed that the cured products of the Examples of the present application all had excellent flexural modulus, heat resistance (Tg), and low water absorption.

[0181] Industrial Applicability

[0182] The epoxy resin mixture of the present invention has excellent heat resistance, elastic modulus, low water absorption, and flame retardancy, so it is effectively used as a carbon fiber reinforced composite material. The carbon fiber reinforced composite material using the epoxy resin mixture of the present invention is lightweight and has excellent resistance to external impact, so it can be suitable for aircraft components such as fuselage, main wing, tail, movable wing, fairing, cowl, door, seat and interior decoration materials; spacecraft components such as motor housing and main wing; satellite components such as body structures and antennas; automobile components such as outer panels, chassis, aerodynamic components and seats; railway vehicle components such as body structures and seats; ship components such as hulls and seats, etc.

Claims

1. An epoxy resin mixture comprising an epoxy resin represented by the following formula (1) and an epoxy resin represented by the following formula (2) in a weight ratio of 1:5 to 1:0.2, and having an ICI melt viscosity of 0.2 Pa·s to 1.0 Pa·s at 150° C., In formula (1), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, n1 represents a real number of 1 to 10, G represents a substituted or unsubstituted glycidyl group, In formula (2), a plurality of R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, n2 represents a real number of 1 to 10, and G represents a substituted or unsubstituted glycidyl group. The epoxy resin mixture is obtained by reacting a phenol resin represented by the following formula (3) and a phenol resin represented by the following formula (4) with an epihalohydrin, In formula (3), a plurality of R1s exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n1 represents a real number of 1 to 10. In a measurement by gel permeation chromatography, the component represented by n1=1 is 1 area % or more and less than 10 area %, the component represented by n1=2 is 1 area % or more and less than 60 area %, the total content of the component represented by n1=1 and the component represented by n1=3 is 1 area % or more and less than 20 area %, the total content of the component represented by n1=2 and the component represented by n1=4 is 10 area % or more and less than 80 area %, In formula (4), a plurality of R2 and R3 exist independently and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n2 represents a real number of 1 to 10.

2. An epoxy resin composition comprising the epoxy resin mixture as claimed in claim 1 and a hardener.

3. The epoxy resin composition according to claim 2, wherein The hardener is an amine hardener.

4. The epoxy resin composition according to claim 2, used for carbon fiber reinforced composite materials. 5 . A resin sheet obtained by applying the epoxy resin composition according to claim 2 onto a supporting substrate. 6 . A prepreg, wherein carbon fibers are impregnated with the epoxy resin composition according to claim 2 or the resin sheet according to claim 5 .

7. A carbon fiber reinforced composite material, obtained by hardening the prepreg according to claim 6.

Images