Phenolic resin, epoxy resin, curable resin composition, cured product, and carbon fiber reinforced composite material

Abstract

The present invention provides a phenolic resin excellent in industrial productivity and ease of handing, an epoxy resin of which cured product has excellent flexural strength, a curable resin composition and a cured article thereof, and a phenolic resin serving as a precursor.　A phenolic resin is represented by formula (1) and has a softening point of 60°C-120°C inclusive. In formula (1), more than one R1 represents respectively independently a hydrogen atom, a hydrocarbon group having 1-4 carbon atoms or an alkoxy group having 1-4 carbon atoms. R2 represents a hydrogen atom or a methyl group, and R3 represents a hydrogen atom or a hydrocarbon group having 1-4 carbon atoms. More than one m is respectively independently an integer of 0-2, and p is an integer of 0-4. n is the average value of repetitions, and is a real number satisfying 1<n<15.

Description

[Technical Field]

[0001] The present invention relates to a phenolic resin, an epoxy resin, a curable resin composition, and a cured product obtained by curing these, as well as a carbon fiber reinforced composite material. [Background technology]

[0002] Epoxy resins, when cured with various curing agents, produce cured products with excellent mechanical properties, water resistance, chemical resistance, heat resistance, and electrical properties. These products are used in a wide range of applications, including adhesives, paints, laminates, molding compounds, and casting materials. Carbon fiber-reinforced composites (CFRPs), which are made by impregnating and curing carbon fibers with epoxy resin and a curing agent as a matrix resin, offer lightweight and high-strength properties. These composites have been widely used in recent years for aircraft structural components, wind turbine blades, automobile exterior panels, and computer applications such as IC trays and laptop computer housings, and demand for CFRP is increasing. Taking advantage of the lightweight and high-strength properties of the molded products, CFRP is particularly used as a matrix resin for aircraft applications.

[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, and other applications. To compensate for the low flexural strength, toughness, adhesiveness, and other properties of thermosetting resins, a widely known method involves adding a highly tough thermoplastic resin to the thermosetting resin matrix (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 required properties of CFRP have become stricter, and further improvements in bending strength and toughness are required when applying it to aerospace applications and structural materials for vehicles. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 60-243113 [Patent Document 2] Japanese Patent Application Publication No. 09-100358 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-155330 [Patent Document 4] Japanese Patent Application Publication No. 58-24531 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 4 discloses 1,3-di(2-(3,4-dihydroxyphenyl)-2-propyl)benzene, and indicates that the compound is a crystal with a melting point of 133 to 137°C. Because recrystallization is required to synthesize the compound, a large amount of organic solvent and resin is discarded, which poses problems in terms of cost and the environment when considering industrial production. Furthermore, in order to knead and melt the compound with other resins, it is necessary to heat the compound to 140°C or higher, which poses problems in terms of handling and large amounts of energy consumption.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a phenolic resin that is excellent in industrial productivity and handleability, an epoxy resin whose cured product has excellent flexural strength, a curable resin composition and its cured product, and a phenolic resin that can be used as a precursor. [Means for solving the problem]

[0008] That is, the present invention is as set forth in the following [1] to

[11] . In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limit values ​​are included. [1] A phenolic resin represented by the following formula (1) having a softening point of 60°C or higher and 120°C or lower.

[0009] [ka] (In formula (1), the plurality of R 1 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. R 2 is represented by a hydrogen atom or a methyl group, and R 3 represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. The plurality of m each independently is an integer of 0 to 2, and p is an integer of 0 to 4. n is the average value of the number of repetitions and is a real number of 1 < n < 15.) [2] A phenol resin represented by the following formula (3) having a softening point of 60°C or higher and 120°C or lower.

[0010] [Chemical formula]

[0011] (In formula (3), n is the average value of the number of repetitions and is a real number of 1 < n < 15.) [3] The phenol resin according to the previous item [1] or [2], wherein the content of the compound represented by n = 1 in the measurement by gel permeation chromatography is less than 90 area%. [4] A curable resin composition containing the phenol resin according to any one of the previous items [1] to [3]. [5] The phenol resin according to any one of the previous items [1] to [3], and at least one selected from a curing accelerator, a polymerization initiator, an epoxy resin, an active ester compound, a phenol resin other than the said phenol resin, a polyphenylene ether compound, a compound having an ethylenically unsaturated bond, an isocyanate resin, a polyamide resin, a maleimide compound, a cyanate ester resin, a polyimide resin, polybutadiene and its modified products, polystyrene and its modified products, polyethylene and its modified products, a benzoxazine compound, a curable resin composition. [6] An epoxy resin obtained by reacting the phenol resin according to any one of the previous items [1] to [3] with epihalohydrin. [7] The epoxy resin according to the preceding paragraph [4], having an epoxy equivalent of 190 g / eq. or more and 280 g / eq. or less. [8] A curable resin composition containing the epoxy resin according to the above item [6] or [7] and a curing agent. [9] A curable resin composition comprising the epoxy resin according to the preceding item [6] or [7], and at least one selected from the group consisting of a curing accelerator, a polymerization initiator, an epoxy resin other than the above-mentioned epoxy resin, an active ester compound, a phenolic resin, a polyphenylene ether compound, a compound having an ethylenically unsaturated bond, an isocyanate resin, a polyamide resin, a maleimide compound, a cyanate ester resin, a polyimide resin, polybutadiene and modified products thereof, polystyrene and modified products thereof, polyethylene and modified products thereof, and a benzoxazine compound.

[10] A cured product obtained by curing the curable resin composition according to the above item [8] or [9].

[11] A carbon fiber reinforced composite material obtained by curing the curable resin composition according to the above item [8] or [9]. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a phenolic resin that is excellent in industrial productivity and handleability, an epoxy resin whose cured product has excellent flexural strength, a curable resin composition, and a cured product thereof. [Brief explanation of the drawings]

[0013] [Figure 1] 1 shows a GPC chart of the phenolic resin obtained in Synthesis Example 1. [Figure 2] 1 shows a GPC chart of the epoxy resin obtained in Synthesis Example 2. [Figure 3] 1 shows a GPC chart of the phenolic resin obtained in Synthesis Example 3. [Figure 4] 1 shows a GPC chart of the epoxy resin obtained in Synthesis Example 4. [Figure 5] The GPC chart of the phenolic resin obtained in Synthesis Example 5 is shown. [Figure 6] The GPC chart of the epoxy resin obtained in Synthesis Example 6 is shown. [Figure 7] The GPC chart of the epoxy resin obtained in Synthesis Example 7 is shown.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments according to the present invention (hereinafter also referred to as "the present embodiment") will be described in more detail.

[0015] The phenolic resin of the present embodiment is represented by the following formula (1).

[0016]

Chemical formula

[0017] In formula (1), a plurality of R 1 each independently represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. R 2 is represented by a hydrogen atom or a methyl group, and R 3 is represented by a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. A plurality of m each independently is an integer of 0 to 2, and p is an integer of 0 to 4. n is an average value of the repetition number and is a real number of 1 < n < 15.

[0018] In the above formula (1), the value of n can be determined from the number average molecular weight determined by measurement of gel permeation chromatography (GPC, detector: RI), or from the area ratio of each separated peak. It is preferable that n is a real number of 1 < n < 15, more preferably 1 < n < 10, and particularly preferably 1 < n < 5. ​In the phenolic resin of this embodiment, the content of the compound represented by n=1 as measured by gel permeation chromatography is preferably less than 90 area %, more preferably less than 80 area %. Furthermore, the content of the compound represented by n=1 is preferably 30 area % or more, more preferably 50 area % or more. When the content of the compound represented by n=1 is less than 90 area %, the resin becomes weakly crystalline and has a resinous structure, improving handleability. When the content of the compound represented by n=1 is 30 area % or more, the softening point is low, improving handleability.

[0020] The phenol resin of this embodiment preferably has a softening point of 60° C. or higher and 120° C. or lower, and more preferably 60° C. or higher and 100° C. or lower. When the softening point is in the above range, the resin has excellent handleability.

[0021] The phenolic resin of this embodiment preferably has a hydroxyl group equivalent of 100 to 140 g / eq., and more preferably 110 to 130 g / eq.

[0022] The phenol resin represented by the formula (1) is more preferably represented by the following formula (3), and particularly preferably represented by the following formula (3-1).

[0023] [ka]

[0024] [ka]

[0025] In the formulas (3) and (3-1), the value and preferred range of n are the same as those in the formula (1).

[0026] The phenolic resin of this embodiment may be mixed with the epoxy resin of this embodiment described below or various materials exemplified in this specification to be used as a curable resin composition.

[0027] Next, the reaction for obtaining the phenolic resin of this embodiment will be described. The phenolic resin of this embodiment can be obtained, for example, by reacting a catechol with a di-substituted benzene compound under acidic conditions. Examples of catechols include catechol, 3-methylcatechol, 4-methylcatechol, 4,5-dimethylcatechol, 3-t-butylcatechol, 4-t-butylcatechol, and 3,5-di-t-butylcatechol. These compounds may be used alone or in combination of two or more. Examples of di-substituted benzene compounds include α,α'-dihydroxy-1,3-diisopropylbenzene, α,α'-dihydroxy-1,4-diisopropylbenzene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene, 1,3-divinylbenzene, and 1,4-divinylbenzene. These compounds may be used alone or in combination of two or more.

[0028] Examples of the solvent include, but are not limited to, methanol, ethanol, propanol, isopropanol, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc., and 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 catechol compound.

[0029] Examples of acidic catalysts include hydrochloric acid, phosphoric acid, sulfuric acid, formic acid, zinc chloride, ferric chloride, aluminum chloride, p-toluenesulfonic acid, methanesulfonic acid, activated clay, and ion exchange resins. These may be used alone or in combination of two or more. The amount of catalyst used is usually 0.1 to 50% by weight, preferably 1 to 30% by weight, based on the catechol compound used. If the amount is too high, the reaction solution becomes too viscous, making stirring difficult, and if the amount is too low, the reaction proceeds slowly.

[0030] Next, the reaction for obtaining the epoxy resin of this embodiment will be described. The epoxy resin of this embodiment can be obtained, for example, by reacting the phenolic resin with epihalohydrin. Examples of epihalohydrin that can be used include epichlorohydrin, β-methylepichlorohydrin, and epibromohydrin. The amount of epihalohydrin used is preferably 1.0 to 20 mol, more preferably 3.0 to 8.0 mol, and even more preferably 4.0 to 6.0 mol, per mol of hydroxyl groups in the phenolic resin.

[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, potassium hydroxide, etc. A solid or an aqueous solution thereof may be used, but in this embodiment, a flake-shaped solid is preferably used in terms 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 raw phenol mixture.

[0032] To promote 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 raw material phenol mixture.

[0033] The reaction temperature is preferably 30 to 90° C., more preferably 35 to 80° C. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, and particularly preferably 1 to 3 hours. If the reaction time is too short, the reaction will not proceed to completion, while if the reaction time is too long, by-products will be produced, which is undesirable.

[0034] The reaction products of these epoxidation reactions are washed with water, or without washing, and then heated under reduced pressure to remove epihalohydrin and solvent. Furthermore, to obtain epoxy resins with fewer hydrolyzable halogens, the recovered epoxy resins can be dissolved in a ketone compound having 4 to 7 carbon atoms (e.g., methyl isobutyl ketone, methyl ethyl ketone, cyclopentanone, cyclohexanone, etc.) as a solvent, and an aqueous solution of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is added to the reaction mixture to ensure ring closure. In this case, the amount of alkali metal hydroxide used is preferably 0.01 to 0.3 mol, more preferably 0.05 to 0.2 mol, per mol of hydroxyl groups in the raw phenol mixture used in the epoxidation. The reaction temperature is preferably 50 to 120°C, and the reaction time is preferably 0.5 to 2 hours.

[0035] After the reaction is complete, the salt formed 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] A typical structure of the epoxy resin of this embodiment is represented by the following formula (2).

[0037] [ka]

[0038] In formula (2), R 1 , R 2 , R 3 The values ​​and preferred ranges of m, p, and n are the same as those in formula (1). 4 represents a hydrogen atom or a methyl group.

[0039] The epoxy resin of the present embodiment preferably has a softening point of 100° C. or less, and more preferably 80° C. or less. A softening point of 100° C. or less provides excellent handleability. The lower limit of the softening point is preferably 40° C. or more.

[0040] The epoxy resin of this embodiment preferably has an epoxy equivalent of 190 g / eq. or more and 280 g / eq. or less, and more preferably 200 g / eq. or more and 240 g / eq. or less.

[0041] The epoxy resin represented by the formula (2) is more preferably represented by the following formula (4), and particularly preferably represented by the following formula (4-1).

[0042] [ka]

[0043] [ka]

[0044] In the formulas (4) and (4-1), the value and preferred range of n are the same as those in the formula (1).

[0045] 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.

[0046] 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. Amine 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, and 3,3'-diisopropyl-5,5'-diethyl-4,4' 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.).

[0047] 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.

[0048] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0049] 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 (e.g., phenol, alkyl-substituted phenol, naphthol, alkyl-substituted naphthol, dihydroxybenzene, and dihydroxynaphthalene, etc.); and aldehydes (formaldehyde, acetaldehyde, benzaldehyde, p-hydroxybenzaldehyde, o-hydroxybenzoates, etc.). 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.

[0050] 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 epoxy groups in the epoxy resin. If the amount is less than 0.7 equivalents relative to 1 equivalent of epoxy groups or more than 1.2 equivalents, curing may be incomplete and good cured physical properties may not be obtained.

[0051] 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 curing 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 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.

[0052] 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, alicyclic epoxy resins typified by 4-vinyl-1-cyclohexene diepoxide and 3,4-epoxycyclohexylmethyl-3,4'-epoxycyclohexanecarboxylate, glycidylamine epoxy resins typified by tetraglycidyldiaminodiphenylmethane (TGDDM) and triglycidyl-p-aminophenol, glycidyl ester epoxy resins, etc., but are not limited to these, so long as they are commonly used epoxy resins.

[0053] The curable resin composition of the present embodiment can be blended with known additives as needed.Specific examples of usable additives include active ester compounds, phenolic resins, compounds having ethylenically unsaturated bonds, isocyanate resins, polyamide resins, benzoxazine compounds, polybutadiene and its modified products, modified acrylonitrile copolymers, polyphenylene ether compounds, polystyrene and its modified products, polyethylene and its modified products, polyimide resins, fluororesins, maleimide compounds, cyanate ester resins, silicone gels, silicone oils, and 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, mold release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0054] Examples of the active ester compound include active ester compounds such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds.

[0055] Examples of polyphenylene ether compounds include SA-9000 (manufactured by SABIC, a polyphenylene ether compound having a methacrylic group) and OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical Co., Inc., a polyphenylene ether compound having a styrene structure).

[0056] Examples of the compound having an ethylenically unsaturated bond include reaction products of a phenol resin with an ethylenically unsaturated bond-containing halogen-based compound (chloromethylstyrene, allyl chloride, methallyl chloride, acrylic acid chloride, methacrylic acid chloride, etc.), reaction products of an ethylenically unsaturated bond-containing phenol (2-allylphenol, 2-propenylphenol, 4-allylphenol, 4-propenylphenol, eugenol, isoeugenol, etc.) with a halogen-based compound (1,4-bis(chloromethyl)benzene, 4,4'-bis(chloromethyl)biphenyl, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dibromobenzophenone, cyanuric chloride, etc.), reaction products of an epoxy resin or alcohols with (meth)acrylic acids (acrylic acid, methacrylic acid, etc.), and acid-modified products thereof.

[0057] Examples of the isocyanate resin include aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylene diisocyanate, m-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and naphthalene diisocyanate; aliphatic or alicyclic diisocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, hydrogenated xylene diisocyanate, norbornene diisocyanate, and lysine diisocyanate; polyisocyanates such as biuret compounds of one or more types of isocyanate monomers or isocyanate compounds obtained by trimerizing the above diisocyanate compounds; and polyisocyanates obtained by a urethanization reaction between the above isocyanate compounds and polyol compounds.

[0058] Examples of 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 Xylox-type maleimide compounds (anilix). Examples of suitable maleimides include maleimide (manufactured by Mitsui Chemicals Fine Co., Ltd.), biphenylaralkyl-type maleimide compounds (solidified by distilling off the solvent under reduced pressure from a resin solution containing the maleimide compound (M2) described in Example 4 of JP 2009-001783 A), bisaminocumylbenzene-type maleimide (maleimide compounds described in WO 2020 / 054601 A), maleimide compounds having an indane structure described in Japanese Patent No. 6629692 or WO 2020 / 217679, and the maleimide compounds described in MATERIAL STAGE Vol. 18, No. 12 2019, "Continued Epoxy Resin CAS Number Story - Curing Agent CAS Number Memorandum No. 31 Bismaleimide (1)" and MATERIAL STAGE Vol. 19, No. 2 2019, "Continued Epoxy Resin CAS Number Story - Curing Agent CAS Number Memorandum No. 32 Bismaleimide (2)." These may be used alone or in combination of two or more. When blending a maleimide compound, a curing accelerator may be blended as needed. The curing accelerators, as well as radical polymerization initiators such as organic peroxides, organic peroxides, and azo compounds can be used.

[0059] Examples of cyanate ester resins include dicyanatobenzene, tricyanatobenzene, dicyanatonaphthalene, dicyanatobiphenyl, 2,2'-bis(4-cyanatophenyl)propane, bis(4-cyanatophenyl)methane, bis(3,5-dimethyl-4-cyanatophenyl)methane, 2,2'-bis(3,5-dimethyl-4-cyanatophenyl)propane, 2,2'-bis(4-cyanatophenyl)ethane, 2,2'-bis(4-cyanatophenyl)hexafluoropropane, bis(4-cyanatophenyl)sulfone, bis(4-cyanatophenyl)thioether, phenol novolac cyanate, and phenol-dicyclopentadiene co-condensates in which the hydroxyl groups have been converted to cyanate groups.

[0060] The polyimide resin may be a mixture of the above diamines and tetracarboxylic dianhydrides (4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-cyclohexene-1,2-dicarboxylic anhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyl ... '-Diphenylsulfonetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2'-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, thio-4 ,4'-Diphthalic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, biphenyl Bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-Naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane 1,2-Ethylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-ethylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2-dichloro ... Propylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, oxy-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, thio-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, sulfonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, rel-[1S,5R,6R]-3-oxabicyclo[3,2,1] Examples include reaction products of octane-2,4-dione-6-spiro-3'-(tetrahydrofuran-2',5'-dione), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, ethylene glycol-bis-(3,4-dicarboxylic anhydride phenyl) ether, 4,4'-biphenyl bis(trimellitic acid monoester acid anhydride), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, etc.

[0061] Examples of polybutadiene and its modified products, polystyrene and its modified products, and polyethylene and its modified products include polybutadiene, hydroxyl-terminated polybutadiene, (meth)acrylate-terminated polybutadiene, carboxylic acid-terminated polybutadiene, amine-terminated polybutadiene, styrene-butadiene rubber, RICON-100, RICON-181, and RICON-184 (all manufactured by Cray Valley Chemical Industry Co., Ltd.), 1,2-SBS (manufactured by Nippon Soda Co., Ltd.), B-1000, B-2000, and B-3000 (all manufactured by Nippon Soda Co., Ltd.); polystyrene, styrene-2-isopropenyl-2-oxazoline copolymer (Epocross RPS-1005 and RP-61, both manufactured by Nippon Shokubai Co., Ltd.), and SEP (styrene-ethylene-propylene copolymer: Septon 1020). Kuraray Co., Ltd.), SEPS (styrene-ethylene propylene-styrene copolymer: Septon 2002, Septon 2004F, Septon 2005, Septon 2006, Septon 2063, Septon 2104, all manufactured by Kuraray Co., Ltd.), SEEPS (styrene-ethylene / ethylene propylene-styrene block copolymer: Septon 4003, Septon 4044, Septon 4055, Septon 4077, Septon 4099, all manufactured by Kuraray Co., Ltd.), SEBS (styrene-ethylene butylene-styrene block copolymer: Septon 8004, Septon 8006, Septon 8007L, all manufactured by Kuraray Co., Ltd.), SEEPS-OH (styrene-ethylene / ethylene propylene-styrene block copolymer with terminal hydroxyl groups: Septon HG252 Kuraray Co., Ltd.), SIS (styrene-isoprene-styrene block copolymer: Septon 5125, Septon 5127, both manufactured by Kuraray Co., Ltd.), hydrogenated SIS (hydrogenated styrene-isoprene-styrene block copolymer: Hybrar 7125F, Hybrar 7311F, both manufactured by Kuraray Co., Ltd.), SIBS (styrene-isobutylene-styrene block copolymer: SIBSTAR073T, SIBSTAR102T, SIBSTAR103T, all manufactured by Kaneka Corporation), Septon V9827, manufactured by Kuraray Co., Ltd.;Examples of such copolymers include ethylene-propylene copolymers, ethylene-styrene copolymers, ethylene-propylene-ethylidenenorbornene copolymers (EBT: K-8370EM, K-9330M, etc., manufactured by Mitsui Chemicals, Inc.), ethylene-propylene-vinylnorbornene copolymers (VNB-EPT: PX-006M, PX-008M, PX-009M, etc., manufactured by Mitsui Chemicals, Inc.), ethylene-vinyl alcohol copolymers, and ethylene-vinyl acetate copolymers;

[0062] Examples of benzoxazine compounds include benzoxazine Pd, Fa, and ALP-d (all manufactured by Shikoku Chemical Industry Co., Ltd.), JBZ-BA100N, JBZ-FA100N, JBZ-DP100N, JBZ-OP100N, JBZ-OP100D, and JBZ-OP100I (all manufactured by JFE Chemical Corporation), and BTBz (manufactured by Japan Material Technology Co., Ltd.).

[0063] The curable resin composition of the present embodiment can be obtained by uniformly mixing the above-mentioned components. The method for producing the curable resin composition of the present embodiment is not particularly limited, but the composition can be obtained, for example, by thoroughly mixing an epoxy resin with a curing agent, a curing accelerator, an inorganic filler, a mold release agent, a silane coupling agent, additives, etc., using an extruder, kneader, rolls, planetary mixer, etc. until the mixture is uniform.

[0064] Depending on the molding method, the obtained curable resin composition can be in various forms such as a resin sheet, a prepreg, etc. A prepreg form can be obtained, for example, by heating and melting the curable resin composition and / or a resin sheet of the present embodiment to reduce the viscosity and impregnating the composition into a fiber substrate.

[0065] The curable resin composition of this embodiment can be dissolved in a solvent such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone, as needed, to form a varnish-like composition (hereinafter simply referred to as a varnish), which can then be impregnated into a substrate such as glass fiber, carbon fiber, polyester fiber, polyamide fiber, alumina fiber, or paper, and dried by heating to form a prepreg. In this case, the solvent is used in an amount that accounts for 10 to 70 wt %, preferably 15 to 70 wt %, of the mixture of the curable resin composition of this embodiment and the solvent.

[0066] The prepreg is cut into a desired shape and laminated, and then the curable resin composition is heated and cured while applying pressure to the laminate using a press molding method, autoclave molding method, sheet winding molding method, etc., to obtain a carbon fiber reinforced plastic (CFRP). Copper foil or an organic film can also be laminated during lamination of the prepreg.

[0067] In addition to the above-mentioned methods, CFRP can also be obtained by molding using known methods. For example, resin transfer molding (RTM) 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 resin). The preform is then placed in a mold, the mold is closed, resin is injected into the preform, the resin is impregnated, and cured, and the mold is opened to remove the molded product. Also usable are types of RTM, such as the VaRTM method, the SCRIMP (Seeman's Composite Resin Infusion Molding Process) method, and the CAPRI (Controlled Atmospheric Pressure Resin Infusion) method, which is described in JP 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. Other methods that can be used include the film stacking method, in which a fiber substrate is sandwiched between resin sheets (films), a method in which powder resin is attached to a reinforced fiber substrate to improve impregnation, a molding method that uses a fluidized bed or fluid slurry method in the process of mixing resin into the fiber substrate (Powder Impregnated Yarn), and a method in which resin fibers are mixed into the fiber substrate.

[0068] 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.

[0069] The cured product of the curable resin composition of the present embodiment can be used for various applications other than the above-mentioned applications such as CFRP, and examples thereof include adhesives, paints, coating agents, molding materials (including sheets, films, CFRP, etc.), encapsulants for semiconductor elements, encapsulants for liquid crystal display elements, encapsulants for organic EL elements, electrical and electronic parts such as printed wiring boards (BGA substrates, build-up substrates, etc.), 3D printing, and additives for other resins, etc.

[0070] Examples of the adhesives include adhesives for civil engineering, construction, automobiles, general office use, and medical use, as well as adhesives for electronic materials. Among these, adhesives for electronic materials include interlayer adhesives for multilayer substrates such as build-up substrates, die bonding agents, semiconductor adhesives such as underfills, underfills for reinforcing BGAs, and mounting adhesives such as anisotropic conductive films (ACFs) and anisotropic conductive pastes (ACPs), and are applicable to a variety of uses.

[0071] When the curable resin composition of this embodiment is applied to an encapsulant for semiconductor elements, a lead frame equipped with a semiconductor element or a semiconductor package substrate is placed in a mold, and the curable resin composition of this embodiment is molded by a melt casting method, transfer molding method, injection molding method, compression molding method, or the like, and further heated at 80 to 200°C for 2 to 10 hours to obtain a cured product. Examples of semiconductor devices manufactured using this encapsulant include potting, dipping, and transfer mold encapsulation for capacitors, transistors, diodes, light-emitting diodes, ICs, and LSIs, potting encapsulation for COB, COF, TAB, and the like for ICs and LSIs, underfill for flip chips, and encapsulation (including reinforcing underfill) when mounting IC packages such as QFP, BGA, and CSP.

[0072] When the curable resin composition of this embodiment is applied to printed wiring boards, it can be heated and melted to reduce viscosity, and then impregnated into reinforcing fibers such as glass fibers and polyamide fibers to obtain a prepreg. Specific examples include, but are not limited to, glass fibers such as E-glass cloth, D-glass cloth, S-glass cloth, Q-glass cloth, spherical glass cloth, NE-glass cloth, and T-glass cloth, and / or organic fibers. The shape of the substrate is not particularly limited, but examples include woven fabrics, nonwoven fabrics, rovings, and chopped strand mats. Known weaving methods for woven fabrics include plain weave, sieve weave, and twill weave, and these known methods can be appropriately selected depending on the intended application and performance. Furthermore, woven fabrics that have been subjected to fiber opening treatment or glass woven fabrics that have been surface-treated with a silane coupling agent or the like are preferably used. The thickness of the substrate is not particularly limited, but is preferably about 0.01 to 0.4 mm. Furthermore, a prepreg can be obtained by impregnating reinforcing fibers with the varnish and drying them under heat, and a copper clad laminate (CCL) can be produced from this. A laminate can also be produced using the curable resin composition of this embodiment by hot-press molding the obtained prepreg and CCL. The laminate is not particularly limited as long as it includes one or more prepregs, and may also include any other layers. Furthermore, a sheet-like adhesive can be obtained by applying the varnish to a release film, removing the solvent under heat, and B-staging the varnish. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer substrate or as an adhesive sheet for mounting semiconductors. The curable resin composition of this embodiment can also be suitably used for special substrate materials such as package substrates and high-density interconnects (HDIs). [Example]

[0073] The present embodiment will be described in more detail below with reference to synthesis examples and working examples. The materials, processing details, processing procedures, etc. shown below can be appropriately changed 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. The various analytical methods used in the examples are described below.

[0074] The analysis was carried out under the following conditions. Epoxy equivalent It is measured according to the method described in JIS K-7236, and the unit is g / eq.

[0075] GPC (gel permeation chromatography) Manufacturer:Waters Column: Guard column SHODEX GPC KF-401HQ, KF-402HQ, KF-402.5HQ, KF-403HQ, Flow rate: 0.3ml / min. Column temperature: 40℃ Solvent used: THF (tetrahydrofuran) Detector: RI (differential refractive index detector)

[0076] [Synthesis Example 1] A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 165 parts by weight of catechol, 97 parts by weight of α,α'-dihydroxy-1,3-diisopropylbenzene, 400 parts by weight of toluene, and 3 parts by weight of p-toluenesulfonic acid monohydrate. The mixture was stirred and heated to 110°C, allowing the mixture to dissolve and react. After reaching 110°C, the reaction was continued for 4 hours. Water distilled during the temperature increase and reaction was removed from the system. The mixture was then cooled to 80°C, and 100 parts by weight of water was added. 1 part by weight of sodium tripolyphosphate was added for neutralization. The salt and unreacted catechol were removed by repeated water washing. The toluene was then distilled off under reduced pressure with heating to obtain 140 parts by weight of the phenolic resin represented by formula (1). The hydroxyl equivalent was 114 g / eq., the softening point was 83°C, and the n=1 ratio by GPC was 65% by area. The GPC chart of the resulting phenolic resin is shown in Figure 1.

[0077] [Synthesis Example 2] 91 parts by weight of the phenolic resin obtained in Synthesis Example 1, 444 parts by weight of epichlorohydrin (ECH, hereinafter the same), and 8 parts by weight of benzyltrimethylammonium chloride (BTMAC, hereinafter the same) were charged into a reaction vessel, heated, stirred, and dissolved. After that, the mixture was allowed to react for 6 hours while maintaining the temperature at 50°C. 5 parts by weight of water was then charged, and 34 parts by weight of flaky sodium hydroxide was added in portions over 2 hours at 50°C. The reaction was then continued for 1.5 hours at 50°C and 30 minutes at 70°C. After repeated water washing to remove by-product salts, excess epichlorohydrin was distilled off from the oil layer under heating and reduced pressure, and 272 parts by weight of methyl isobutyl ketone was added to the residue and dissolved. This methyl isobutyl ketone solution was heated to 70°C, and 8 parts by weight of 30% aqueous sodium hydroxide solution was added. The reaction mixture was then allowed to react for 1 hour. The reaction solution was then 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 130 parts by weight of the epoxy resin represented by the above formula (4). The epoxy equivalent of the obtained epoxy resin was 208 g / eq. and the softening point was 53°C. The GPC chart of the obtained epoxy resin is shown in Figure 2.

[0078] [Synthesis Example 3] Synthesis was performed in the same manner as in Synthesis Example 1, except that 97 parts by weight of α,α'-dihydroxy-1,3-diisopropylbenzene was replaced with 49 parts by weight of α,α'-dihydroxy-1,3-diisopropylbenzene and 48 parts by weight of α,α'-dihydroxy-1,4-diisopropylbenzene, yielding 135 parts by weight of phenolic resin. The hydroxyl equivalent was 118 g / eq., the softening point was 86°C, and the n=1 content by GPC was 67 area %. The GPC chart of the resulting phenolic resin is shown in Figure 3.

[0079] [Synthesis Example 4] Synthesis was carried out in the same manner as in Synthesis Example 2, except that the phenolic resin was changed to the phenolic resin obtained in Synthesis Example 3, to obtain 128 parts by weight of an epoxy resin. The epoxy equivalent of the obtained epoxy resin was 214 g / eq. and the softening point was 58°C. The GPC chart of the obtained epoxy resin is shown in Figure 4.

[0080] [Synthesis Example 5] Synthesis was carried out according to Example 3 of Patent Document 4, yielding 95 parts by weight of a crystalline phenolic resin. The hydroxyl group equivalent was 101 g / eq., and the n=1 unit content by GPC was 90 area %. The GPC chart of the obtained phenolic resin is shown in Figure 5.

[0081] [Synthesis Example 6] Synthesis was carried out in the same manner as in Synthesis Example 2, except that the phenolic resin was changed to the phenolic resin obtained in Synthesis Example 5, to obtain 135 parts by weight of an epoxy resin. The obtained epoxy resin had an epoxy equivalent of 186 g / eq. and was liquid at 25°C. The GPC chart of the obtained epoxy resin is shown in Figure 6.

[0082] [Synthesis Example 7] Synthesis was performed according to Example 3 of Japanese Patent No. 7188657, yielding 112 parts by weight of epoxy resin. The epoxy equivalent of the obtained epoxy resin was 187 g / eq. and the softening point was 59°C. The GPC chart of the obtained epoxy resin is shown in Figure 7.

[0083] [Example 1, Comparative Example 1, Comparative Example 2] The epoxy resins obtained in Synthesis Examples 2, 6, and 7 were mixed with 4,4'-diaminodiphenyl sulfone (abbreviated as DDS) as a curing agent in the proportions (parts by weight) shown in Table 1, and cured at 180°C for 6 hours to produce cured products. The physical properties were then evaluated. The results are shown in Table 1.

[0084] The physical properties were measured under the following conditions. <Flexural strength, flexural modulus, measurement conditions> Measured according to JIS K-7074.

[0085] [Table 1]

[0086] From the results in Table 1, it was confirmed that Example 1, which used the epoxy resin of the present invention, had excellent bending strength.

Claims

1. A phenolic resin represented by the following formula (1) having a softening point of 60°C or higher and 120°C or lower, wherein the content of a compound represented by n=1 is less than 80 area % as measured by gel permeation chromatography. 【Chemistry 1】 (In formula (1), there are multiple R １ R each independently represents a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. ２ is represented by a methyl group, and R ３ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. Each of the multiple m's is independently an integer of 0 to 2, and p is an integer of 0 to 4. n is the average number of repeats and is a real number in the range of 1<n<15.

2. A phenolic resin represented by the following formula (3) having a softening point of 60°C or higher and 120°C or lower, wherein the content of a compound represented by n=1 is less than 80 area % as measured by gel permeation chromatography. 【Chemistry 2】 (In formula (3), n is the average number of repetitions and is a real number in the range of 1<n<15.)

3. A curable resin composition containing the phenolic resin according to claim 1 or 2.

4. 3. A curable resin composition comprising the phenolic resin according to claim 1 or 2, and at least one selected from the group consisting of a curing accelerator, a polymerization initiator, an epoxy resin, an active ester compound, a phenolic resin other than the phenolic resin, a polyphenylene ether compound, a compound having an ethylenically unsaturated bond, an isocyanate resin, a polyamide resin, a maleimide compound, a cyanate ester resin, a polyimide resin, polybutadiene and modified products thereof, polystyrene and modified products thereof, polyethylene and modified products thereof, and a benzoxazine compound.

5. 3. An epoxy resin obtained by reacting the phenolic resin according to claim 1 or 2 with epihalohydrin.

6. 6. The epoxy resin according to claim 5, having an epoxy equivalent of 190 g / eq. or more and 280 g / eq. or less.

7. A curable resin composition comprising the epoxy resin according to claim 5 and a curing agent.

8. 6. A curable resin composition comprising the epoxy resin according to claim 5, and at least one selected from the group consisting of a curing accelerator, a polymerization initiator, an epoxy resin other than the epoxy resin, an active ester compound, a phenolic resin, a polyphenylene ether compound, a compound having an ethylenically unsaturated bond, an isocyanate resin, a polyamide resin, a maleimide compound, a cyanate ester resin, a polyimide resin, polybutadiene and modified products thereof, polystyrene and modified products thereof, polyethylene and modified products thereof, and a benzoxazine compound.

9. A cured product obtained by curing the curable resin composition according to claim 7.

10. A carbon fiber reinforced composite material obtained by curing the curable resin composition according to claim 7.

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