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

Abstract

The present invention provides a phenolic resin having excellent industrial productivity and handling properties, an epoxy resin having excellent impact resistance as a cured product, a curable resin composition, and a cured product thereof.　The phenolic resin is represented by formula (1) and has a softening point of 60°C to 120°C. (In formula (1), the plurality of R1 each independently represent a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. R2 represents a methyl group. R3 represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. The plurality of m each independently represent an integer of 0 to 2, and p is an integer from 0 to 4. The plurality of a are each independently an integer of 1 or 2, and, from among the plurality of a, at least one is 1 and at least one is 2. n is the average value of repetitions, and is a real number satisfying 1<n<15.)

Description

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

[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.

[0002] Epoxy resins, when cured with various curing agents, become cured products with excellent mechanical properties, water resistance, chemical resistance, heat resistance, electrical properties, and the like, 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 carbon fibers with epoxy resins and curing agents as a matrix resin, can be endowed with properties such as light weight and high strength. Therefore, in recent years, CFRP has 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 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 composites 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 further improvements in bending strength and toughness are required when applying it to aerospace applications and structural materials for vehicles, etc.

[0005] JP-A No. 60-243113 JP-A No. 09-100358 JP-A No. 2013-155330 JP-A No. 58-24531

[0006] Patent Document 4 discloses 1,3-di(2-(3,4-dihydroxyphenyl)-2-propyl)benzene, and indicates that the compound is in the form of 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 an object of the present invention is to provide a phenolic resin that is excellent in industrial productivity and handleability, an epoxy resin whose cured product is excellent in impact resistance, a curable resin composition, and a cured product thereof.

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

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

[0009]

[0010] (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 represents a methyl group. 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. Each of the multiple a's is independently an integer of 1 or 2, and at least one of the multiple a's is 1 and at least one is 2. n is the average number of repetitions and is a real number satisfying the condition 1<n<15.) [2] A phenolic resin represented by the following formula (3A), which has a softening point of 60°C or higher and 120°C or lower.

[0011]

[0012] (In formula (3A), there are multiple R １each independently represents a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Each of the multiple m's is independently an integer of 0 to 2. Each of the multiple a's is independently an integer of 1 or 2, and at least one of the multiple a's is 1 and at least one is 2. n is the average value of the 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 the preceding item [1] or [2]. [4] A curable resin composition containing the phenolic resin according to the preceding item [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] An epoxy resin obtained by reacting the phenolic resin described in the preceding paragraph [1] or [2] with epihalohydrin. [6] The epoxy resin described in the preceding paragraph [5], having an epoxy equivalent of 190 g / eq. or more and 280 g / eq. or less. [7] A curable resin composition containing the epoxy resin described in the preceding paragraph [5] or [6] and a curing agent. [8] A curable resin composition containing the epoxy resin described in the preceding paragraph [5] or [6] and at least one selected from 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 described in the preceding paragraph [7].

[10] A carbon fiber reinforced composite material obtained by curing the curable resin composition according to the preceding item [7].

[0013] 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 is excellent in impact resistance, a curable resin composition, and a cured product thereof.

[0014]

[0033] Figure 1 shows a GPC chart of the phenolic resin obtained in Synthesis Example 1.

[0034] Figure 2 shows a GPC chart of the epoxy resin obtained in Synthesis Example 2.

[0035] Figure 3 shows a GPC chart of the phenolic resin obtained in Synthesis Example 3.

[0036] Figure 4 shows a GPC chart of the epoxy resin obtained in Synthesis Example 4.

[0037] Figure 5 shows a GPC chart of the phenolic resin obtained in Synthesis Example 5.

[0038] Figure 6 shows a GPC chart of the epoxy resin obtained in Synthesis Example 6.

[0015] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in further detail.

[0016] The phenolic resin of the present embodiment is represented by the following formula (1).

[0017]

[0018] 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 represents a methyl group. ３ represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. Multiple m's each independently represent an integer of 0 to 2, and p represents an integer of 0 to 4. n represents the average number of repeats and is a real number in the range of 1<n<15.

[0019] In the formula (1), the multiple a's each independently represent an integer of 1 or 2, and at least one of the multiple a's is 1 and at least one is 2. The ratio of those where a is 1 (i.e., those having one hydroxy group) to those where a is 2 (i.e., those having two hydroxy groups) is preferably 10:90 to 80:20. When the ratio of those where a is 2 is 20% or more, the heat resistance is improved, and when it is 90% or less, the softening point is low and handleability is improved. The above ratio can be controlled by the mixing ratio of the raw material phenols and catechols, which will be described later.

[0020] In the formula (1), the value of n can be calculated from the number average molecular weight determined by measurement using gel permeation chromatography (GPC, detector: RI) or the area ratio of each separated peak. n is preferably a real number satisfying 1<n<15, more preferably 1<n<10, and particularly preferably 1<n<5.

[0021] The phenol resin of the present 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 phenol resin has excellent handleability.

[0022] 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.

[0023] The phenolic resin represented by the formula (1) is more preferably represented by the following formula (3) or formula (3A).

[0024]

[0025] In formula (3) and formula (3A), R １ 、 m, a, and n have the same meanings as in 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 phenol, a catechol, and a di-substituted benzene compound under acidic conditions. Examples of phenols include phenol, cresol, and xylenol. Examples of catechols include catechol, 3-methylcatechol, 4-methylcatechol, 4,5-dimethylcatechol, 3-t-butylcatechol, 4-t-butylcatechol, and 3,5-di-t-butylcatechol, and 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, and 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 the acidic catalyst 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 large, the reaction solution becomes too viscous, making stirring difficult, and if the amount is too small, 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 phenol 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 phenol 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, the use of a solid 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 raw material 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 a reduced hydrolyzable halogen content, 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 solution to carry out the reaction and 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]

[0038] In formula (2), R １ , R ２ , R ３ , m, p, a, and n have the same meanings as 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. When the epoxy equivalent is 280 g / eq. or less, the heat resistance is good, and when it is 190 g / eq. or more, the impact resistance is good.

[0041] The epoxy resin represented by the formula (2) is more preferably represented by the following formula (4) or formula (4A).

[0042]

[0043] In the formulas (4) and (4A), m, a, and n have the same meanings as in the formula (1).

[0044] The curable resin composition of the present embodiment preferably 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.

[0045] 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, 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-ethylhexanoate 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.).

[0046] 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.

[0047] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0048] 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 4,4'-bis(chloromethyl)-1,1'-biphenyl and 4,4'-bis(methoxymethyl)-1,1'-biphenyl, or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, or the like); modified products of the phenols and / or the phenolic resins; and halogenated phenols such as tetrabromobisphenol A and brominated phenolic resins.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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 Company, a polyphenylene ether compound having a styrene structure).

[0055] 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.

[0056] 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 one or more biuret compounds 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.

[0057] 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 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, 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. 12 2019 Examples of suitable maleimide compounds include those described in "Epoxy Resin CAS Number Story Continued - Curing Agent CAS Number Memorandum No. 32, Bismaleimide (2)" published in February 2019. These compounds may be used alone or in combination of two or more. When incorporating maleimide compounds, a curing accelerator may be incorporated as needed. These may include the aforementioned curing accelerators, as well as radical polymerization initiators such as organic peroxides and azo compounds.

[0058] 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 hydroxyl groups have been converted to cyanate groups.

[0059] 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-1,2dicarboxylic 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, 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-1,2,4,5-tetracarboxylic acid dianhydride, 3,3',4,4'-bicyclohexyltetracarboxylic acid dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 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 -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 ]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 acid anhydride, ethylene glycol-bis-(3,4-dicarboxylic acid anhydride phenyl) ether, 4,4'-biphenylbis(trimellitic acid monoester acid anhydride), 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, etc., reaction products thereof,

[0060] Examples of polybutadiene and modified products thereof, polystyrene and modified products thereof, and polyethylene and modified products thereof include polybutadiene, hydroxyl-terminated polybutadiene, (meth)acrylate-terminated polybutadiene, carboxylic acid-terminated polybutadiene, amine-terminated polybutadiene, styrene-butadiene rubber, RICON-100, RICON-181, RICON-184 (all manufactured by Cray Valley Chemical Industry Co., Ltd.), 1,2-SBS (manufactured by Nippon Soda Co., Ltd.), B-1000, B-2000, B-3000 (all manufactured by Nippon Soda Co., Ltd.); polystyrene, styrene-2-isopropenyl-2-oxazoline copolymer (Epocross RPS-1005, 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 a terminal hydroxyl group: Septon HG252, manufactured by Kuraray Co., Ltd.), SIS (styrene-isoprene-styrene block copolymer: Septon HG252, manufactured by Kuraray Co., Ltd.), block copolymers: Septon 5125, Septon 5127, both manufactured by Kuraray Co., Ltd.), hydrogenated SIS (hydrogenated styrene-isoprene-styrene block copolymers: Hybrar 7125F, Hybrar 7311F, both manufactured by Kuraray Co., Ltd.), SIBS (styrene-isobutylene-styrene block copolymers: 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;

[0061] Examples of the benzoxazine compound include benzoxazine P-d, 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.).

[0062] 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.

[0063] The obtained curable resin composition can be molded into 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.

[0064] The curable resin composition of this embodiment can also 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 produce 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.

[0065] The prepreg is cut into a desired shape, laminated, and then the curable resin composition is heated and cured while applying pressure to the laminate by press molding, autoclave molding, sheet winding molding, etc., to obtain a carbon fiber reinforced plastic (CFRP). Copper foil or an organic film can also be laminated during lamination of the prepreg.

[0066] In addition to the above-mentioned methods, CFRP can also be obtained by molding using known methods, such as resin transfer molding (RTM), 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 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 JP-A-2005-527410, in which a resin supply tank is evacuated to a pressure lower than atmospheric pressure, cyclic compression is used, and the net molding pressure is controlled to more appropriately control the resin injection process, particularly the VaRTM method. 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.

[0067] 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.

[0068] 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, electric and electronic parts such as printed wiring boards (BGA substrates, build-up substrates, etc.), 3D printing, and additives for other resins, etc.

[0069] Examples of the adhesive 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.

[0070] 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) for mounting IC packages such as QFP, BGA, and CSP.

[0071] 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 fabric, nonwoven fabric, roving, chopped strand mat, and the like. 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 opened or 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 approximately 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 comprises one or more prepregs, and may also have any other layer. 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 adhesive. 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 HDIs (high density interconnects).

[0072] The flexural strength of the curable resin composition of this embodiment is preferably 130 MPa or more, more preferably 140 MPa or more, and particularly preferably 150 MPa or more. The flexural modulus is preferably 3 GPa or more, more preferably 3.5 GPa or more, and particularly preferably 4 GPa or more. The IZOD impact strength is preferably 6 GPa or more, and more preferably 7 GPa or more. These measurements are performed using the methods described in the Examples below.

[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 changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Various analytical methods used in the examples will be described below.

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

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

[0076] Synthesis Example 1: A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 83 parts by weight of catechol, 71 parts by weight of phenol, 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 mixture was repeatedly washed with water to remove the salt and unreacted catechol. The toluene was then distilled off under reduced pressure with heating to obtain 110 parts by weight of a phenolic resin represented by the formula (1). The hydroxyl equivalent was 120 g / eq. and the softening point was 78°C. A 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, and then the mixture was allowed to react for 6 hours while maintaining the temperature at 50°C. Five parts by weight of water was then charged, and 31 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 a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, and the reaction solution was repeatedly washed with water until the washings became neutral. Methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 120 parts by weight of the epoxy resin represented by formula (2). The epoxy equivalent of the obtained epoxy resin was 200 g / eq. and the softening point was 50°C. The GPC chart of the obtained epoxy resin is shown in Figure 2.

[0078] Synthesis Example 3: 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 dissolved and reacted while stirring and heating to 110°C. 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 mixture was repeatedly washed with water to remove the salt and unreacted catechol. The toluene was then distilled off under reduced pressure with heating to obtain 140 parts by weight of a phenolic resin. The hydroxyl equivalent was 114 g / eq. and the softening point was 83°C. A GPC chart of the resulting phenolic resin is shown in Figure 3.

[0079] Synthesis Example 4: 91 parts by weight of the phenolic resin obtained in Synthesis Example 3, 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, and then the mixture was allowed to react for 6 hours while maintaining the temperature at 50°C. Five 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 a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, and the reaction solution was repeatedly washed with water until the washings became neutral. Methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 130 parts by weight of an epoxy resin. 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 4.

[0080] Synthesis Example 5: A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 83 parts by weight of catechol, 81 parts by weight of p-cresol, 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 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 mixture was repeatedly washed with water to remove the salt and unreacted catechol. The toluene was then distilled off under heating and reduced pressure to obtain 115 parts by weight of a phenolic resin represented by the above formula (1). The hydroxyl equivalent was 130 g / eq. and the softening point was 90°C. A GPC chart of the resulting phenolic resin is shown in Figure 5.

[0081] Synthesis Example 6: 78 parts by weight of the phenolic resin obtained in Synthesis Example 5, 333 parts by weight of epichlorohydrin (ECH, hereinafter the same), and 7 parts by weight of benzyltrimethylammonium chloride (BTMAC, hereinafter the same) were charged into a reaction vessel, heated, stirred, and dissolved. The mixture was then allowed to react for 6 hours while maintaining the temperature at 50°C. Then, 4 parts by weight of water was charged, and 26 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 223 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 a 30% aqueous sodium hydroxide solution was added. The reaction was allowed to proceed for 1 hour, and the reaction solution was repeatedly washed with water until the washings became neutral. Methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure to obtain 100 parts by weight of the epoxy resin represented by formula (2). The epoxy equivalent of the obtained epoxy resin was 234 g / eq. and the softening point was 62°C. The GPC chart of the obtained epoxy resin is shown in Figure 6.

[0082] [Examples 1-2, Comparative Examples 1-2] The epoxy resins obtained in Synthesis Examples 2, 4, and 6 were blended with 4,4'-diaminodiphenyl sulfone (abbreviation: 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. Similarly, in Comparative Example 2, a cured product was prepared using epoxy resin ESPD295 (manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent 298 g / eq., softening point 68°C) represented by the following formula (5) and DDS. Thereafter, physical properties were evaluated. The results are shown in Table 1.

[0083]

[0084] The physical properties were measured under the following conditions: <Flexural strength, flexural modulus, measurement conditions> Measured according to JIS K-7074. <IZOD impact test, measurement conditions> Measured according to JIS K-6911.

[0085]

[0086] From the results in Table 1, it was confirmed that Examples 1 and 2, which used the epoxy resin of the present invention, met the target values ​​for various mechanical properties, and were particularly excellent in impact resistance (IZOD test 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. (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 represents a methyl group. 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. Each of the multiple a's is independently an integer of 1 or 2, and at least one of the multiple a's is 1 and at least one is 2. n is the average number of repeating units and is a real number in the range of 1<n<15.

2. A phenolic resin represented by the following formula (3A) having a softening point of 60°C or higher and 120°C or lower. (In formula (3A), there are multiple R １ each independently represents a hydrocarbon group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Each of the multiple m's is independently an integer of 0 to 2. Each of the multiple a's is independently an integer of 1 or 2, and at least one of the multiple a's is 1 and at least one is 2. 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. 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. An epoxy resin obtained by reacting the phenolic resin according to claim 1 or 2 with epihalohydrin.

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 containing the epoxy resin according to claim 5 and a curing agent.

8. A curable resin composition comprising the epoxy resin of 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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