Epoxy resin, curable resin components, cured products of that, and carbon fiber reinforced composite materials.

Abstract

Invention details;

Description

Epoxy resin, curable resin composition, cured product thereof, and carbon fiber reinforced composite material

[0001] The present invention relates to an epoxy resin, a curable resin composition, and a cured product thereof, as well as a carbon fiber reinforced composite material.

[0002] Epoxy resins, when cured with various curing agents, become cured products with excellent mechanical properties, water resistance, chemical resistance, heat resistance, electrical properties, etc., and are used in a wide range of fields, such as adhesives, paints, laminates, molding materials, and casting materials. Carbon fiber reinforced composite materials (CFRP), which are made by impregnating and curing reinforcing fibers with epoxy resin and a curing agent as a matrix resin, can be imparted with properties such as light weight and high strength. In recent years, these materials have been widely used in aircraft structural components, wind turbine blades, automobile exterior panels, and computer applications such as IC trays and laptop computer housings, and demand for them is increasing. In particular, they are used as matrix resins for aircraft applications, taking advantage of the light weight and high strength properties of the molded products.

[0003] Cured thermosetting resins, such as epoxy resins, used as matrix resins for CFRP and other materials are generally brittle, and require high mechanical strength when used as structural materials for aerospace applications, vehicles, etc. To compensate for the low flexural strength, toughness, adhesiveness, etc. of thermosetting resins, a method of adding a highly tough thermoplastic resin to the thermosetting resin matrix is ​​widely known (Patent Documents 1 to 3). Specifically, the flexural strength and toughness of prepregs are improved by combining particles of thermoplastic resins such as polyethersulfone, polyetherimide, and polyamide with the thermosetting resin matrix resin.

[0004] In recent years, the properties required of CFRP have become stricter, and resins with better heat resistance are required, particularly when used in aerospace applications and as structural materials for vehicles, etc. (Patent Document 4).

[0005] Japanese Patent Publication No. 60-243113 Japanese Patent Publication No. 09-100358 Japanese Patent Publication No. 2013-155330 Japanese Patent Publication No. 2010-275492 Japanese Patent Publication No. 2007-211254

[0006] Patent Document 5 describes an epoxy resin with low water absorption. However, the epoxy resin described in Patent Document 5 has low heat resistance, making it difficult to apply it as a CFRP material.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epoxy resin, a curable resin composition, and cured products thereof, and a carbon fiber reinforced composite material, all of which have excellent heat resistance.

[0008] That is, the present invention provides the following [1] to [6]. In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limits are included. [1] An epoxy resin represented by the following formula (1), in which, when the peak area of ​​a compound represented by the following formula (2) in a chromatogram of high performance liquid chromatography is a and the peak area of ​​a compound represented by the following formula (3) is b, the ratio b / a is 0.012 or more and 0.050 or less.

[0009]

[0010] In formula (1), n ​​is the average number of repeating units and is a real number in the range of 1 < n < 15. Each X is independently a monovalent group represented by formula (a) or formula (b), and at least one X is a monovalent group represented by formula (a). * is bonded to an oxygen atom.

[0011]

[0012]

[0013] [2] The epoxy resin according to the preceding item [1], having an epoxy equivalent of 200 g / eq. or more and 220 g / eq. or less. [3] A curable resin composition containing the epoxy resin according to the preceding item [1] or [2] and a curing agent. [4] The curable resin composition according to the preceding item [3], wherein the curing agent is an amine-based curing agent. [5] A cured product obtained by curing the curable resin composition according to the preceding item [3] or [4]. [6] A carbon fiber reinforced composite material obtained by curing the curable resin composition according to the preceding item [3] or [4].

[0014] According to the present invention, it is possible to provide an epoxy resin, a curable resin composition, and a cured product thereof, and a carbon fiber reinforced composite material, the cured product of which has excellent heat resistance.

[0015] 1 is an HPLC chart of Synthesis Example 1. 2 is an HPLC chart of Synthesis Example 2. 3 is an HPLC chart of Synthesis Example 3. 4 is an HPLC chart of Synthesis Example 4. 5 is an HPLC chart of Synthesis Example 5. 6 is an HPLC chart of Synthesis Example 6. 7 is an HPLC chart of Synthesis Example 7.

[0016] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in further detail.

[0017] The epoxy resin of the present invention is represented by the following formula (1), and when the peak area of ​​a compound represented by the following formula (2) in a chromatogram of high performance liquid chromatography is a and the peak area of ​​a compound represented by the following formula (3) is b, the ratio b / a is 0.012 or more and 0.050 or less.

[0018]

[0019] In formula (1), n ​​is the average number of repeating units and is a real number in the range of 1 < n < 15. Each X is independently a monovalent group represented by formula (a) or formula (b), and at least one X is a monovalent group represented by formula (a). * is bonded to an oxygen atom.

[0020]

[0021]

[0022] In the formula (1), the value of n can be calculated from the number average molecular weight of the epoxy resin determined by gel permeation chromatography (GPC, detector: RI) or the area ratio of each separated peak. n is preferably a real number in the range of 1<n<15, more preferably 1<n<10, and particularly preferably 1<n<5.

[0023] The epoxy resin of this embodiment can obtain a cured product with excellent heat resistance by controlling the b / a value. Specifically, b / a is preferably 0.012 or more and 0.050 or less, more preferably 0.014 or more and 0.040 or less, and even more preferably 0.015 or more and 0.030 or less. The reason why heat resistance is improved when b / a is 0.12 or more is not clearly understood, but it is thought that the inclusion of a certain amount of the compound represented by formula (3) makes molecular movement difficult due to the influence of hydrogen bonding. When b / a is greater than 0.050, the amount of the compound represented by formula (3) increases, resulting in fewer crosslinking points during curing and a lower glass transition temperature (Tg). In this embodiment, HPLC (high performance liquid chromatography) is measured using the method described in the Examples below.

[0024] The glass transition point (Tg) of the epoxy resin of this embodiment is preferably 170 to 300°C, more preferably 172 to 250°C, and even more preferably 174 to 200°C. A glass transition point below 170°C is undesirable because it is difficult to apply to components requiring heat resistance, such as those around aircraft engines, and the resin softens during use, significantly reducing mechanical strength and leading to material damage. Furthermore, the glass transition point of an epoxy resin generally correlates with crosslink density, and the higher the crosslink density, the higher the glass transition point. In other words, a glass transition point above 300°C is undesirable because the crosslink density increases and the mechanical strength of the cured product becomes brittle. The glass transition point (Tg) of this embodiment is measured using the method described in the Examples below.

[0025] The epoxy equivalent of the epoxy resin of this embodiment is preferably 200 g / eq. or more and 220 g / eq. or less, more preferably 204 g / eq. or more and 218 g / eq. or less, and even more preferably 213 g / eq. or more and 218 g / eq. or less.

[0026] The epoxy resin represented by the formula (1) can be obtained by reacting a phenol resin represented by the following formula (4) with epihalohydrin.

[0027]

[0028] In formula (4), n is the average number of repetitions and is a real number in the range of 1<n<15.

[0029] The preferred range of n in the formula (4) is the same as that in the formula (1).

[0030] The epihalohydrin is readily available on the market. The amount of epihalohydrin used is preferably 2.0 to 10 mol, more preferably 3.0 to 8.0 mol, and even more preferably 3.5 to 6.0 mol, per mol of hydroxyl groups in the phenolic resin represented by formula (4). Preferred epihalohydrins that can be used in this embodiment include epichlorohydrin, α-methylepichlorohydrin, β-methylepichlorohydrin, epibromohydrin, and the like, and epichlorohydrin, which is easily available industrially, is particularly preferred.

[0031] In the above reaction, an alkali metal hydroxide can be used as a catalyst to promote the epoxidation step. Usable alkali metal hydroxides include sodium hydroxide and potassium hydroxide. A solid alkali metal hydroxide may be used, or an aqueous solution of the alkali metal hydroxide may be used. In this embodiment, the use of a solid alkali metal hydroxide formed into flakes is particularly preferred from the standpoints of solubility and handling. The amount of alkali metal hydroxide used is preferably 0.90 to 1.5 mol, more preferably 0.95 to 1.25 mol, and even more preferably 0.99 to 1.15 mol, per mol of hydroxyl groups in the phenolic resin represented by formula (4).

[0032] To accelerate the reaction, a quaternary ammonium salt such as tetramethylammonium chloride, tetramethylammonium bromide, or trimethylbenzylammonium chloride may be added as a catalyst. The amount of the quaternary ammonium salt used is preferably 0.1 to 15 g, more preferably 0.2 to 10 g, per mole of hydroxyl groups in the phenolic resin represented by formula (4).

[0033] The reaction temperature is preferably 30 to 90°C, more preferably 35 to 80°C. In particular, in this embodiment, for higher purity epoxidation, a temperature of 50°C or higher is preferred, and 60°C or higher is particularly preferred. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, and particularly preferably 1 to 3 hours. A short reaction time is not preferred because the reaction does not proceed to completion, while a long reaction time is not preferred because by-products are produced.

[0034] The reaction product of these epoxidation reactions (mixture A containing the epoxy resin represented by the formula (1)) can be washed with water, or without washing with water, and then epihalohydrin, solvent, etc. can be removed under heating and reduced pressure to obtain mixture B containing the epoxy resin represented by the formula (1). Mixture B contains the epoxy resin represented by the formula (1), a trace amount of residual solvent, and by-product salts. Furthermore, in order to obtain an epoxy resin with a lower hydrolyzable halogen content, mixture B is dissolved in a solvent such as a ketone compound having 4 to 7 carbon atoms (e.g., methyl isobutyl ketone, methyl ethyl ketone, cyclopentanone, cyclohexanone, etc.) or an aromatic hydrocarbon compound having 6 to 10 carbon atoms (e.g., toluene, xylene, etc.), and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added to carry out the reaction. In Patent Document 5, the reaction is carried out by adding only an aqueous solution of an alkali metal hydroxide, but in this embodiment, water and / or alkali metal hydroxide are added to the aqueous solution of the alkali metal hydroxide. The reaction is carried out by further adding alcohol. It has been found that this produces a compound represented by formula (3), thereby improving heat resistance. The amount of alkali metal hydroxide used is preferably 0.01 to 0.3 mol, and more preferably 0.05 to 0.2 mol, per mol of hydroxyl groups in the phenolic resin represented by formula (4) used in the epoxidation. The amount of water used is 10 to 40 wt%, and preferably 15 to 25 wt%, based on the theoretical yield of the epoxy resin represented by formula (1). Examples of alcohols include methanol, ethanol, propanol, and isopropanol. The amount of alcohol used is 5 to 40 wt%, and preferably 15 to 25 wt%, based on the theoretical yield of the epoxy resin represented by formula (1). The total amount of water and alcohol used is 15 to 60 wt%, and preferably 20 to 50 wt%, based on the theoretical yield of the epoxy resin represented by formula (1). The reaction temperature is preferably 50 to 120°C, and the reaction time is more preferably 0.5 to 2 hours.

[0035] After the reaction is completed, the salt produced is removed by filtration, washing with water, or the like, and the solvent is then distilled off under heating and reduced pressure to obtain the epoxy resin of the present embodiment.

[0036] In the synthesis method of the phenolic resin represented by the formula (4), when furfural is reacted (condensed) with a phenol, the amount of the phenol is preferably 1.5 to 20 moles, particularly preferably 3 to 10 moles, per mole of furfural.

[0037] Examples of phenols include disubstituted phenols such as catechol, resorcinol, and hydroquinone, and monosubstituted phenols such as phenol, cresol, and xylenol, and these may be used alone or in combination of two or more.

[0038] Examples of solvents used in the synthesis of phenolic resins include, but are not limited to, methanol, ethanol, propanol, isopropanol, toluene, xylene, etc. These may be used alone or in combination of two or more. When a solvent is used, the amount used is preferably in the range of 5 to 500 parts by weight, more preferably 10 to 300 parts by weight, per 100 parts by weight of the phenols.

[0039] A basic catalyst is preferably used in the condensation reaction of furfural and phenols. Condensation polymerization is also possible with an acidic catalyst, but reactions between furfurals occur, resulting in increased by-products. Alternatively, an organometallic compound can be used as a catalyst, but this is cost-inefficient. Specific examples of basic catalysts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, and potassium tert-butoxide; and alkaline earth metal alkoxides such as magnesium methoxide and magnesium ethoxide. However, the basic catalyst is not limited to these, and may be used alone or in combination of two or more. The amount of catalyst used is preferably 0.005 to 2.0 times, more preferably 0.01 to 1.1 times, the moles per mole of hydroxyl groups in the phenols.

[0040] The condensation reaction in the presence of these basic catalysts is preferably carried out in the range of 40 to 180°C, particularly preferably in the range of 80 to 165°C. The time for the condensation reaction can be selected preferably in the range of 0.5 to 10 hours. The reaction product thus obtained is neutralized to neutralize the system or repeatedly washed with water in the presence of a solvent, and then the water is separated and drained, and the solvent and unreacted materials are removed under heating and reduced pressure to obtain the phenolic resin represented by formula (4).

[0041] The curable resin composition of the present embodiment contains a curing agent. Examples of curing agents that can be used include amine-based curing agents, acid anhydride-based curing agents, amide-based curing agents, and phenol-based curing agents.

[0042] In the curable resin composition of the present embodiment, an amine-based curing agent is preferred, since it can achieve a good balance between the resin viscosity of the curable resin composition and the heat resistance of the cured resin. Examples of amine-based curing agents include 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), diaminodiphenylmethane (DDM), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane (TEDDM), 3,3'-diisopropyl-5,5'-diethyl-4 ,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2-(dimethylaminomethyl)phenol (DMP-10), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 2-ethylhexanoic acid ester of 2,4,6-tris(dimethylaminomethyl)phenol, and the like can be used. Other examples include aniline novolak, orthoethylaniline novolak, aniline resins obtained by reacting aniline with xylylene chloride, and aniline resins obtained by polycondensation of aniline with substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl, 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, etc.).

[0043] Examples of the acid anhydride curing agent include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0044] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0045] Examples of phenolic curing agents include polyhydric phenols (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, naphthalenediol, tris-(4-hydroxyphenyl)methane, and 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, etc.); phenols (for example, phenol, alkyl-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, and dihydroxynaphthalene, etc.); and aldehydes (formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, o-hydroxybenzoates, benzophenone ... 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, 1,4-bis(hydroxymethyl)benzene, etc.); modified products of the phenols and / or the phenolic resins; and halogenated phenols such as tetrabromobisphenol A and brominated phenolic resins.

[0046] In the curable resin composition of this embodiment, it is also preferable to use the phenol resin represented by the formula (4) as the entire amount of the curing agent or as a part thereof.

[0047] In the curable resin composition of this embodiment, the amount of curing agent used is preferably 0.7 to 1.2 equivalents relative to 1 equivalent of the epoxy group of the epoxy resin. If the amount is less than 0.7 equivalents relative to 1 equivalent of the epoxy group or if it exceeds 1.2 equivalents, curing may be incomplete and good cured physical properties may not be obtained.

[0048] Furthermore, a curing accelerator may be blended into the curable resin composition of this embodiment as needed. The gelation time can also be adjusted by using a curing accelerator. Examples of usable curing accelerators 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 octoate. The curing accelerator is used in an amount of 0.01 to 5.0 parts by weight per 100 parts by weight of the epoxy resin, as needed.

[0049] The curable resin composition of the present embodiment may contain other epoxy resins. Specific examples thereof include phenols (phenol, alkyl-substituted phenol, aromatic-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, alkyl-substituted dihydroxybenzene, dihydroxynaphthalene, etc.) and various aldehydes (formaldehyde, acetaldehyde, alkyl aldehyde, benzaldehyde, alkyl-substituted benzaldehyde, hydroxybenzaldehyde, naphthaldehyde, etc.). , glutaraldehyde, phthalaldehyde, crotonaldehyde, cinnamaldehyde, etc.), polymers of phenols and various diene compounds (dicyclopentadiene, terpenes, vinylcyclohexene, norbornadiene, vinylnorbornene, tetrahydroindene, divinylbenzene, divinylbiphenyl, diisopropenylbiphenyl, butadiene, isoprene, etc.), polymers of phenols and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, benzo[a]thiazolinone, benzo[b ... phenolic resins obtained by polycondensation 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, 1,4-bis(hydroxymethyl)benzene, etc.); polycondensates of bisphenols and various aldehydes; glycidyl ether epoxy resins obtained by glycidylating alcohols, etc.; alicyclic epoxy resins typified by 4-vinyl-1-cyclohexene diepoxide and 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, etc.; glycidylamine epoxy resins typified by tetraglycidyldiaminodiphenylmethane (TGDDM) and triglycidyl-p-aminophenol, etc.; glycidyl ester epoxy resins, etc., but are not limited to these, so long as they are commonly used epoxy resins.

[0050] The curable resin composition of the present embodiment may contain known additives as needed. Specific examples of the additives that can be used include polybutadiene and its modified products, modified acrylonitrile copolymers, polyphenylene ether, polystyrene, polyethylene, polyimide, fluororesin, maleimide compounds, cyanate ester compounds, silicone gel, silicone oil, inorganic fillers such as silica, alumina, 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, release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0051] The curable resin composition of this embodiment can contain a known maleimide compound as needed. Specific examples of usable maleimide compounds include 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, m-phenylene bismaleimide, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene, and biphenylaralkyl maleimide, but are not limited to these. These compounds may be used alone or in combination of two or more. When a maleimide compound is blended, a curing accelerator is blended as necessary. The above-mentioned curing accelerators, as well as radical polymerization initiators such as organic peroxides and azo compounds can be used.

[0052] The curable resin composition of this embodiment can be made into a varnish-like composition (hereinafter simply referred to as "varnish") by adding an organic solvent. Examples of the solvent that can be used include amide-based solvents such as γ-butyrolactones, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidinone; sulfones such as tetramethylene sulfone; ether-based solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate, and propylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; and aromatic solvents such as toluene and xylene. The solvent is used so that the solids concentration excluding the solvent in the resulting varnish is preferably 10 to 80 wt %, more preferably 20 to 70 wt %.

[0053] The curable resin composition of this embodiment can also be used as a resin sheet, prepreg, or carbon fiber reinforced composite material. The curable resin composition of this embodiment can be applied to one or both sides of a support substrate to form a resin sheet. Examples of application methods include casting, extruding the resin through a nozzle or die using a pump or extruder, adjusting the thickness with a blade, adjusting the thickness by calendaring with a roll, and spraying using a sprayer. The layer formation process may be performed while heating within a temperature range that avoids thermal decomposition of the curable resin composition. Furthermore, rolling, grinding, and other processes may be performed as necessary. Examples of support substrates include, but are not limited to, porous substrates made of paper, cloth, nonwoven fabric, etc.; plastic films or sheets such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; nets; foams; metal foils; and laminates thereof. The thickness of the support substrate is not particularly limited and can be determined appropriately depending on the application.

[0054] The curable resin composition and / or resin sheet of this embodiment can be heated and melted to reduce the viscosity, and then impregnated into a fiber substrate to obtain the prepreg of this embodiment.

[0055] Alternatively, the prepreg of this embodiment can be obtained by impregnating a fiber substrate with a varnish-like curable resin composition and drying it by heating. The prepreg is cut into a desired shape, laminated, and then the curable resin composition is heat-cured while applying pressure to the laminate by press molding, autoclave molding, sheet winding, or the like, to obtain the carbon fiber reinforced composite material of this embodiment. Copper foil or an organic film can also be laminated during lamination of the prepreg.

[0056] Furthermore, the carbon fiber reinforced composite material of this embodiment can be obtained by molding using known methods other than the above-mentioned methods. For example, a resin transfer molding technique (RTM method) can be used, in which a carbon fiber substrate (usually a carbon fiber fabric) is cut, laminated, and shaped to produce a preform (a preform before being impregnated with a resin), the preform is placed in a mold, the mold is closed, resin is injected to impregnate the preform, and the resin is cured, and the mold is then opened to remove the molded product. Also usable are types of RTM methods, such as the VaRTM method, the SCRIMP (Seeman's Composite Resin Infusion Molding Process), and the CAPRI (Controlled Atmospheric Pressure Resin Infusion) method, which is described in Japanese Patent Application Laid-Open No. 2005-527410 and which more appropriately controls the resin injection process, particularly the VaRTM method, by evacuating a resin supply tank to a pressure lower than atmospheric pressure, using cyclic compression, and controlling the net molding pressure.

[0057] Furthermore, a film stacking method in which a fiber substrate is sandwiched between resin sheets (films), a method in which powdered resin is attached to a reinforcing fiber substrate to improve impregnation, a molding method in which a fluidized bed or fluid slurry method is used in the process of mixing resin into a fiber substrate (Powder Impregnated Yarn), and a method in which resin fibers are mixed into a fiber substrate can also be used.

[0058] Examples of carbon fibers include acrylic, pitch, and rayon carbon fibers, and among these, acrylic carbon fibers, which have high tensile strength, are preferably used. The carbon fiber may be in the form of twisted yarn, untwisted yarn, or non-twisted yarn, but untwisted yarn or non-twisted yarn is preferred because it provides a good balance between the formability and strength properties of the fiber-reinforced composite material.

[0059] The present invention will be explained in more detail below with reference to synthesis examples and examples. The materials, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0060] The analysis was carried out under the following conditions. Hydroxyl equivalent: Measured by the following method, in units of g / eq. Phenolic resin was reacted with excess acetic anhydride, and titrated with a 0.5N KOH ethanol solution using a potentiometer to measure the amount of free acetic acid. Reagents: acetic anhydride, triphenylphosphine, pyridine Solvent: tetrahydrofuran, propylene glycol monomethyl ether Automatic titrator: COM-1600 manufactured by HIRANUMA Corporation Burette: B-2000 manufactured by HIRANUMA Corporation Epoxy equivalent: Measured by the method described in JIS K-7236, in units of g / eq. HPLC (High Performance Liquid Chromatography) Shimadzu Corporation: Liquid Delivery Unit LC-20AD Shimadzu Corporation: Photodiode Array Detector SPD-M20A Shimadzu Corporation: Column Oven CTO-20A Column: Intersil ODS-2.5 μm, 4.6 × 250 mm, 40°C Mobile Phase (Mobile Phase) A: Acetonitrile (AN) Mobile Phase (Mobile Phase) B: Water (W) Gradient elution was performed in which the mobile phase composition was graded as follows: Time Program: From the start of 0 minutes to 28 minutes, the ratio of mobile phase A to mobile phase B, AN / W, was changed from 50% / 50% to 100% / 0%. From the start of the experiment, the ratio AN / W of mobile phase A to mobile phase B was 100% / 0% from 28 minutes to 40 minutes. The flow rate of the mobile phase was 1.0 mL / min. Ultraviolet light with a wavelength of 274 nm was detected using a photodiode array (PDA) that detects ultraviolet light with wavelengths of 200 nm to 274 nm. GPC (Gel Permeation Chromatography) Analysis Apparatus: ACQUITY APC System (Waters) Column: Guard column SHODEX GPC KF-601, KF-602 KF-602.5, KF-603 Flow rate: 0.5 mL / min Column temperature: 40°C Solvent used: THF (tetrahydrofuran) Detector: RI (differential refractometer)

[0061] Synthesis Example 1: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 33 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 90 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 141 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged into a reaction vessel, followed by heating and stirring, with 254 parts by weight of epichlorohydrin (ECH, hereinafter the same), 64 parts by weight of dimethyl sulfoxide (DMSO, hereinafter the same), and 13 parts by weight of water. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 22 parts by weight of water, 22 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure, yielding 107 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 1.7). The epoxy equivalent of the resulting epoxy resin was 204 g / eq. The HPLC results are shown in Figure 1. The peaks for the compound represented by formula (2) were observed at 13.5, 14.2, and 15.3 minutes, and the peaks for the compound represented by formula (3) were observed at 10.5, 11.3, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.015.

[0062] Synthesis Example 2: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 53 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was allowed to react for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 142 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged to a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 22 parts by weight of water, 22 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure, yielding 103 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 2.0). The epoxy equivalent of the resulting epoxy resin was 214 g / eq. The HPLC results are shown in Figure 2. The peaks for the compound represented by formula (2) were observed at 13.5, 14.2, and 15.3 minutes, and the peaks for the compound represented by formula (3) were observed at 10.5, 11.3, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.015.

[0063] Synthesis Example 3: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 63 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 112 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 147 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged into a reaction vessel, followed by heating and stirring, with 254 parts by weight of epichlorohydrin (ECH, hereinafter the same), 64 parts by weight of dimethyl sulfoxide (DMSO, hereinafter the same), and 13 parts by weight of water. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 108 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 22 parts by weight of water, 22 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 103 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 2.2). The epoxy equivalent of the resulting epoxy resin was 218 g / eq. The HPLC results are shown in Figure 3. The peaks for the compound represented by formula (2) were observed at 13.7, 14.4, and 15.5 minutes, and the peaks for the compound represented by formula (3) were observed at 10.7, 11.5, and 11.8 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.017.

[0064] Synthesis Example 4: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 53 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was allowed to react for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 142 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged to a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 22 parts by weight of water, 26 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 101 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 2.1). The epoxy equivalent of the resulting epoxy resin was 213 g / eq. The HPLC results are shown in Figure 4. The peaks for the compound represented by formula (2) were observed at 13.5, 14.2, and 15.3 minutes, and the peaks for the compound represented by formula (3) were observed at 10.5, 11.3, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.026.

[0065] Synthesis Example 5: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 44 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 142 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged to a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 5 parts by weight of water and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 103 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 1.8). The epoxy equivalent of the resulting epoxy resin was 207 g / eq. The HPLC results are shown in Figure 5. The peaks for the compound represented by formula (2) were observed at 13.5 minutes, 14.2 minutes, and 15.3 minutes, and the peaks for the compound represented by formula (3) were observed at 10.5 minutes, 11.3 minutes, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.009.

[0066] Synthesis Example 6: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 40 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was allowed to react for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 107 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 141 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged into a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was gradually added to the flask over 2 hours while maintaining the temperature of the reaction solution at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salt. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 5 parts by weight of water and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. Next, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure to obtain 90 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 2.0). The epoxy equivalent of the resulting epoxy resin was 211 g / eq. The HPLC results are shown in Figure 6. The peaks for the compound represented by formula (2) were observed at 13.5, 14.2, and 15.3 minutes, and those for the compound represented by formula (3) were observed at 10.5, 11.3, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.009.

[0067] Synthesis Example 7: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 53 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was allowed to react for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 142 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged to a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and EC, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, yielding Mixture B containing the epoxy resin, a trace amount of residual solvent, and a trace amount of by-product salts. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the resulting Mixture B and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 7 parts by weight of water, 44 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 103 parts by weight of the epoxy resin represented by formula (1) (n in formula (1) is 2.3). The epoxy equivalent of the resulting epoxy resin was 266 g / eq. The HPLC results are shown in Figure 7. The peaks for the compound represented by formula (2) were observed at 13.5, 14.2, and 15.3 minutes, and the peaks for the compound represented by formula (3) were observed at 10.5, 11.3, and 11.6 minutes.The ratio b / a of the sum b of the peak areas at 10.5 minutes, 11.3 minutes, and 11.6 minutes to the sum a of the peak areas at 13.5 minutes, 14.2 minutes, and 15.3 minutes was 0.267.

[0068] Synthesis Example 8: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 33 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 90 parts by weight of the phenolic resin represented by the formula (4). The hydroxyl equivalent of the resulting phenolic resin was 141 g / eq. 78 parts by weight of the obtained phenolic resin represented by formula (4) were charged to a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. The excess epichlorohydrin and DMSO were then distilled off under heating and reduced pressure to obtain a mixture B containing the epoxy resin represented by formula (1), a by-product salt, and a trace amount of residual solvent. The theoretical yield of epoxy resin in this reaction was 109 parts by weight. 218 parts by weight of methyl isobutyl ketone was added to the obtained mixture B, dissolving it, and the by-product salt was removed by washing with water. This methyl isobutyl ketone solution was heated to 70°C, and 22 parts by weight of water, 22 parts by weight of methanol, and 7 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure, yielding 107 parts by weight of an epoxy resin represented by the above formula (1) (n in formula (1) is 1.7). The epoxy equivalent of the resulting epoxy resin was 204 g / eq.

[0069] [Examples 1 to 4, Comparative Examples 1 to 3] The epoxy resins obtained in Synthesis Examples 1 to 7 were used as the base resin, and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane (abbreviation: TEDDM, manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent: 78 g / eq.) was used as the curing agent. These were mixed in the weight ratios shown in Table 1, and cured at 160°C for 6 hours to produce cured products.

[0070] The physical properties were measured under the following conditions: <Conditions for measuring glass transition temperature (Tg)> Thermomechanical measuring apparatus (TMA): TMA Q400EM manufactured by TA-instruments Heating rate: 2°C / min Measurement temperature range: 25°C to 300°C Tg: The point at which the thermal expansion coefficient changes was taken as Tg.

[0071]

[0072] From the results in Table 1, it was confirmed that the cured products of Examples 1 to 4 of the present invention had higher glass transition points and better heat resistance than the cured products of Comparative Examples 1 to 3.

[0073] This application claims priority based on Japanese Patent Application No. 2023-113999, filed July 11, 2023.

Claims

DEPCT691. Epoxy resin which is represented by the following formula(1), where b / a has a value of 0.012 or more and 0.050 or less, where “a” is the peak area of ​​the compound which is represented by the following formula(2) in the chromatogram of the epoxy resin high-performance liquid chromatography, and “b” is the peak area of ​​the compound which is represented by the following formula(3) in the chromatogram, [Chemistry1](Chemical Formula)(1)X=(Chemical Formula) or (Chemical Formula)(a)(b) in Formula(1), n ​​is the average number of repeat units and is the real number corresponding to 1. <n<15,Xแต่ละตัวโดยไม่ขึ้นต่อกันนั้นคือหมู่โมโนวาเลนท์ซึ่งถูกแสดงแทนโดยสูตร(a)หรือสูตร(b),และXอย่างน้อยหนึ่งตัวคือหมู่โมโนวาเลนท์ซึ่งถูกแสดงแทนโดยสูตร(a),และ*สร้างพันธะกับอะตอมออกซิเจน,[เคมี2](สูตรเคมี)(2)[เคมี3](สูตรเคมี)(3).2.อีพอกซีเรซินตามข้อถือสิทธิที่1,ที่มีสมมูลอีพอกซี200กรัม / สมมูลหรือมากกว่านั้นและ220กรัม / สมมูลหรือน้อยกว่านั้น3.องค์ประกอบเรซินที่สามารถบ่มได้ที่ประกอบรวมด้วยอีพอกซีเรซินตามข้อถือสิทธิที่1และสารช่วยบ่ม4.องค์ประกอบเรซินที่สามารถบ่มได้ตามข้อถือสิทธิที่3,ที่ซึ่งสารช่วยบ่มคือสารช่วยบ่มที่มีพื้นฐานเป็นเอมีน5.Products which are cured by curing resin components that are curable under claims 3 or 46; carbon fiber reinforced composite materials which are obtained by curing resin components that are curable under claims 3 or 4;

Images