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

Abstract

The present invention provides: an epoxy resin which has excellent heat resistance; a curable resin composition which contains the epoxy resin; and a carbon fiber-reinforced composite material in which these are cured.　The epoxy resin is obtained by reacting a phenolic compound represented by formula (1) with an epihalohydrin. [Chemical formula 1] (In formula (1), a dotted line between C1 and C2, a dotted line between C2 and C3, a dotted line between C3 and C4, a dotted line between C4 and C5, a dotted line between C5 and C6, and a dotted line between C6 and C1 each indicate that a single bond or a double bond may exist as long as the valence permits, m and n are each an average value of the number of repetitions, m is a real number satisfying 1 < m ≤ 5, and n is a real number satisfying 1 < n ≤ 10.)

Description

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

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

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

[0003] Among these, fiber-reinforced plastic molded products reinforced with reinforcing fibers have attracted attention for their lightweight yet excellent mechanical strength characteristics, and are being increasingly used in a variety of structural applications, including housings and various components for automobiles, aircraft, ships, etc. In particular, as carbon fiber reinforced composite materials (CFRP) are increasingly being applied to aircraft and automobiles, the amount of epoxy resin used as their matrix resin is steadily increasing.

[0004] Traditionally, many epoxy resins and curing agents have been derived from petroleum. However, in recent years, concerns have arisen about the depletion of petroleum resources, and methods of recycling many materials, such as using renewable resources such as plants, or decomposing the cured materials, are being considered.

[0005] Japanese Patent Application Publication No. 04-117420

[0006] Patent Document 1 describes an epoxy resin made from biomass-derived raw materials. However, the epoxy resin described in Patent Document 1 has low heat resistance and poor mechanical properties such as flexural strength and flexural modulus, making it difficult to use as a CFRP material.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epoxy resin having excellent heat resistance, a curable resin composition containing the epoxy resin, and a carbon fiber reinforced composite material obtained by curing the epoxy resin or the cured resin composition.

[0008] That is, the present invention is as shown in the following [1] to [7]. In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limits are included. [1] An epoxy resin obtained by reacting a phenolic compound represented by the following formula (1) with epihalohydrin.

[0009]

[0010] (In formula (1), C １ and C ２ Between ２ and C ３ Between ３ and C ４ Between ４ and C ５ Between ５ and C ６ Between and C ６ and C １ The dotted line between indicates that either a single bond or a double bond may be present within the range permitted by the valence. m and n each represent the average number of repeating units, and m is a real number satisfying 1<m≦5 and n is a real number satisfying 1<n≦10.) [2] The epoxy resin according to the preceding paragraph [1], wherein the phenolic compound represented by formula (1) is obtained by adding a phenol to a cyclic terpene compound. [3] The epoxy resin according to the preceding paragraph [1], wherein the epoxy equivalent is 280 g / eq. or more and 600 g / eq. or less. [4] A curable resin composition containing the epoxy resin according to any one of the preceding paragraphs [1] to [3] and a curing agent. [5] A cured product obtained by curing the curable resin composition according to the preceding paragraph [4]. [6] A carbon fiber reinforced composite material obtained by curing the curable resin composition according to the preceding paragraph [4]. [7] The epoxy resin according to the preceding paragraph [1], wherein the phenolic compound represented by formula (1) is YS Polystar K125 (trade name, manufactured by Yasuhara Chemical Co., Ltd.).

[0011] According to the present invention, it is possible to provide an epoxy resin, a curable resin composition, and a carbon fiber reinforced composite material obtained by curing these, which have excellent heat resistance when cured.

[0012] 1 is a GPC chart of the epoxy resin of Example 1. FIG. 2 is a GPC chart of the epoxy resin of Comparative Example 1.

[0013] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in further detail.

[0014] The epoxy resin of the present embodiment is obtained by reacting a phenolic resin represented by the following formula (1) with epihalohydrin.

[0015]

[0016] (In formula (1), C １ and C ２ Between ２ and C ３ Between ３ and C ４ Between ４ and C ５ Between ５ and C ６ Between and C ６ and C １ The dotted line between indicates that either a single bond or a double bond may be present within the range permitted by the atomic valence. m and n are the average values ​​of the number of repeats, and m is a real number satisfying 1<m≦5 and n is a real number satisfying 1<n≦10.

[0017] In the formula (1), the values ​​of m and n can be calculated from the number average molecular weight determined by gel permeation chromatography (GPC, detector: RI), gas chromatography (GC-MS, ionization method: EI), or NMR measurement, or from the area ratio of each separated peak. m is a real number that satisfies 1<m≦5, and preferably 3≦m≦5. n is a real number that satisfies 1<n≦10, but preferably 1<n≦5, and more preferably 3≦n≦5.

[0018] The phenolic resin represented by formula (1) can be obtained by subjecting a cyclic terpene compound to an addition reaction with a phenol. The starting cyclic terpene compound may be a monocyclic or bicyclic terpene compound, and specific examples thereof include α-pinene, β-pinene, α-terpinene, β-terpinene, γ-terpinene, 3,8-menthadiene, 2,4-menthadiene, limonene, and terpinolene. Phenols, which are the other starting material for producing a cyclic terpene skeleton-containing polyhydric phenol compound, include disubstituted phenols such as catechols, resorcinols, and hydroquinones, and monosubstituted phenols such as phenol, bisphenol A, and bisphenol F, which may be used alone or in combination of two or more. A commercially available example of the phenolic compound represented by formula (1) is YS Polystar K125 (trade name, manufactured by Yasuhara Chemical Co., Ltd.), which has the following formula (2) as its representative structure:

[0019]

[0020] The epihalohydrin is readily available on the market. The amount of epihalohydrin used is usually 2.0 to 10 mol, preferably 3.0 to 8.0 mol, and more preferably 3.5 to 6.0 mol, per mol of hydroxyl groups in the phenolic resin represented by formula (1). Preferred epihalohydrins that can be used in this embodiment include epichlorohydrin, α-methylepichlorohydrin, β-methylepichlorohydrin, and epibromohydrin, with epichlorohydrin being particularly preferred because it is easily available industrially.

[0021] In the reaction between the phenolic resin represented by formula (1) and epihalohydrin, 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., and while a solid or an aqueous solution thereof may be used, 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 typically 0.90 to 1.5 mol, preferably 0.95 to 1.25 mol, and more preferably 0.99 to 1.15 mol, per mol of hydroxyl groups in the raw phenol mixture.

[0022] 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 usually 0.1 to 15 g, and preferably 0.2 to 10 g, per mole of hydroxyl groups in the starting phenol mixture.

[0023] The reaction temperature is usually 30 to 90°C, preferably 35 to 80°C. In particular, in this embodiment, for higher purity epoxidation, a temperature of 50°C or higher is preferred, and 60°C or higher is particularly preferred. The reaction time is usually 0.5 to 10 hours, 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, and if the reaction time is too long, by-products will be produced, which is undesirable.

[0024] 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 resulting solution to carry out the reaction and ensure ring closure. In this case, the amount of alkali metal hydroxide used is typically 0.01 to 0.3 mol, preferably 0.05 to 0.2 mol, per mol of hydroxyl groups in the starting phenol mixture used in the epoxidation. The reaction temperature is typically 50 to 120°C, and the reaction time is typically 0.5 to 2 hours.

[0025] 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.

[0026] The epoxy resin of this embodiment preferably has a weight-average molecular weight of 500 or more and 4,500 or less, more preferably 600 or more and 3,000 or less, and even more preferably 800 or more and 2,000 or less. If the weight-average molecular weight is less than 500, it is difficult to obtain the effect of improving heat resistance due to an increase in molecular weight. On the other hand, if the weight-average molecular weight is more than 4,500, not only is purification by water washing or the like difficult, but the viscosity is too high when used in a carbon fiber reinforced composite material, making it difficult to ensure fluidity, impregnating and wetting the fibers, and making it difficult to ensure the fluidity of the prepreg.

[0027] The epoxy resin of this embodiment preferably has an epoxy equivalent of 280 g / eq. or more and 600 g / eq. or less, and more preferably 300 g / eq. or more and 500 g / eq. or less. If the epoxy equivalent is less than 280 g / eq., the water absorption of the cured product becomes high, making it difficult to use in carbon fiber reinforced composite materials. On the other hand, if the epoxy equivalent is more than 600 g / eq., the viscosity becomes too high to ensure fluidity, impairing fiber impregnation and wettability, and making it difficult to ensure the fluidity of the prepreg.

[0028] The epoxy resin of this embodiment preferably has a resinous form having a softening point, and the softening point is preferably from 40° C. to 120° C., and more preferably from 80° C. to 100° C. A softening point of 40° C. or higher means that the resin has an appropriate molecular weight distribution or is free of residual solvents, etc., and has good heat resistance, making it possible to suppress problems such as poor curing and voids during molding. A softening point of 120° C. or lower makes the resin easy to handle when kneaded with other resins.

[0029] The melt viscosity (150°C) of the epoxy resin of this embodiment is preferably 0.1 to 1.5 Pa·s. If the viscosity is higher than 1.5 Pa·s, problems arise with fluidity, resulting in problems with flowability and embeddability during pressing. If the viscosity is less than 0.1 Pa·s, the molecular weight is too small, resulting in insufficient heat resistance. In the prepreg molding method for carbon fiber reinforced composite materials, low tackiness is desired, so the melt viscosity (150°C) is preferably 0.5 to 1.2 Pa·s.

[0030] The curable resin composition of this embodiment contains the epoxy resin of this embodiment and a curing agent. The curable resin composition of this embodiment preferably has a heat resistance (Tg) of 160 to 300°C, more preferably 180 to 250°C. A heat resistance of less than 160°C is undesirable because it is difficult to apply to components requiring heat resistance, such as those around aircraft engines, and the resin softens during use, significantly reducing mechanical strength and leading to material damage. Furthermore, the heat resistance of epoxy resins is generally correlated with crosslink density, with higher crosslink density resulting in higher heat resistance. In other words, a heat resistance exceeding 300°C is undesirable because the crosslink density increases and the mechanical strength of the cured product becomes brittle.

[0031] Examples of curing agents that can be used in the curable resin composition of this embodiment include amine-based curing agents, acid anhydride-based curing agents, amide-based curing agents, and phenol-based curing agents.

[0032] In the curable resin composition of the present embodiment, an amine 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.).

[0033] 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.

[0034] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The curable resin composition of this embodiment can contain a known maleimide compound as needed. Specific examples of usable maleimide compounds include 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, m-phenylene bismaleimide, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylether bismaleimide, 4,4'-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)benzene, and biphenylaralkyl maleimide, but are not limited to these. These compounds may be used alone or in combination of two or more. When a maleimide compound is blended, a curing accelerator is blended as necessary. The above-mentioned curing accelerators, as well as radical polymerization initiators such as organic peroxides and azo compounds can be used.

[0040] The gel time of the curable resin composition of this embodiment 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.

[0041] The curable resin composition of the present embodiment may further contain various additives exemplified below as needed. However, the curable resin composition of the present embodiment is not limited to the additives listed below, and may contain various additives well known in the technical field as needed.

[0042] The curable resin composition of this embodiment may further contain a flame retardant, if necessary, for the purpose of imparting flame retardancy. The flame retardant is not particularly limited, and examples thereof include phosphorus compounds such as red phosphorus coated with a thermal epoxy resin such as a phenolic resin, phosphate esters, and triphenylphosphine oxide; nitrogen-containing compounds such as melamine, melamine derivatives, melamine-modified phenolic resins, compounds having a triazine ring, cyanuric acid derivatives, and isocyanuric acid derivatives; phosphorus and nitrogen-containing compounds such as cyclophosphazene; metal complex compounds such as dicyclopentadienyl iron; zinc compounds such as zinc oxide, zinc stannate, zinc borate, and zinc molybdate; metal oxides such as iron oxide and molybdenum oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; and composite metal hydroxides represented by the following composition formula (A). Further examples include known organic or inorganic compounds and metal hydroxides containing a halogen atom, antimony atom, nitrogen atom, or phosphorus atom.

[0043] The curable resin composition of the present embodiment may further contain an inorganic filler as needed. Specific examples of the inorganic filler include fine powders of fused silica, crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, talc, clay, mica, etc., and beads obtained by spheronizing these powders.

[0044] Inorganic fillers having a flame retardant effect may be used, such as aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as composite hydroxides of magnesium and zinc, and zinc borate.

[0045] When the curable resin composition contains an inorganic filler, its content is not particularly limited as long as the effects of this embodiment can be obtained. The content of the inorganic filler is preferably 50 wt% or more based on the total weight of the curable resin composition, and from the viewpoint of flame retardancy, it is more preferably 60 wt% to 95 wt%, and even more preferably 70 wt% to 90 wt%. By including an inorganic filler, the thermal expansion coefficient, thermal conductivity, elastic modulus, etc. of the cured product can be improved to desired properties. When the content of the inorganic filler is 50 wt% or more, the effect of improving these properties can be more effectively obtained. Furthermore, when it is 95 wt% or less, the increase in viscosity of the curable resin composition is further suppressed, sufficient fluidity is easily obtained, and moldability is further improved.

[0046] The curable resin composition of the present embodiment may further contain an antioxidant as needed. This can prevent oxidation of the cured product of the curable resin composition, and can suppress weight loss of the cured product even when left in a high-temperature environment. Electrical properties are further improved.

[0047] Examples of the antioxidant include phenol-based antioxidants, phosphite-based antioxidants, sulfur-based antioxidants, hindered amine-based antioxidants, etc. These antioxidants may be used alone or in combination of two or more.

[0048] When the curable resin composition contains an antioxidant, the content thereof is not particularly limited as long as the weight loss suppression effect is achieved. From the viewpoint of the heat resistance (high Tg) of the curable resin composition, the content of the antioxidant is preferably 0.5 to 20 parts by weight, and more preferably 1 to 10 parts by weight, of the total amount of antioxidant per 100 parts by weight of the total amount of epoxy resin. By setting the content of the antioxidant to 0.5 parts by weight or more, the weight loss suppression effect of the cured product can be sufficiently obtained, and by setting the content of the antioxidant to 20 parts by weight or less, a decrease in the heat resistance (high Tg) of the cured product can be suppressed.

[0049] The curable resin composition of this embodiment may further contain a coupling agent, if necessary. This further improves the adhesion between the resin component and the inorganic filler, and further improves the electrical properties. The coupling agent can be appropriately selected from commonly used compounds. Examples of the coupling agent include known coupling agents such as various silane-based compounds such as epoxysilane, mercaptosilane, aminosilane, alkylsilane, ureidosilane, vinylsilane, styrylsilane, methacrylsilane, acrylicsilane, and sulfidosilane, titanium-based compounds, aluminum chelate compounds, and aluminum / zirconium-based compounds. Among these, silane-based compounds are preferred. These coupling agents may be used alone or in combination of two or more.

[0050] When the curable resin composition contains a coupling agent, the content thereof is preferably 0.05 to 5.0 parts by weight, and more preferably 0.1 to 4.5 parts by weight, relative to 100 parts by weight of the total amount of the inorganic filler. By making the content 0.05 parts by weight or more, the adhesion to the frame, etc. is further improved.

[0051] The method for preparing the curable resin composition of this embodiment is not particularly limited, and the components may be simply mixed uniformly, or may be prepolymerized. For example, a mixture containing the compound of this embodiment is heated in the presence or absence of a curing accelerator or a polymerization initiator, and in the presence or absence of a solvent, to form a prepolymer. Similarly, compounds such as amine compounds, compounds having ethylenically unsaturated bonds, maleimide compounds, cyanate ester compounds, polybutadiene and its modified products, polystyrene and its modified products, inorganic fillers, and other additives may be added to form a prepolymer. The components may be mixed or prepolymerized using, for example, an extruder, kneader, or rolls in the absence of a solvent, or a reaction kettle equipped with a stirrer in the presence of a solvent.

[0052] The curable resin composition of this embodiment can be obtained by uniformly mixing the above components. The curable resin composition of this embodiment can be easily formed into a cured product using a method similar to that known in the art. For example, the curable resin composition of this embodiment can be obtained by thoroughly mixing an epoxy resin and a curing agent, as well as optionally a curing accelerator, an inorganic filler, a mold release agent, a silane coupling agent, and additives, using an extruder, kneader, roll, planetary mixer, or the like, until the mixture is uniform. The resulting resin composition can take various forms, such as a resin sheet, a prepreg, a liquid composition, or a solid powder, depending on the molding method used.

[0053] When the curable resin composition of this embodiment is to be used in the form of a prepreg, for example, the curable resin composition and / or a resin sheet of this embodiment can be heated and melted to reduce viscosity and then impregnated into a fiber substrate to obtain the prepreg of this embodiment. Furthermore, if necessary, an organic solvent can be added to form a varnish-like composition (hereinafter simply referred to as "varnish"). 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 to form 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 then heated and dried 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. The prepreg is cut into the desired shape, laminated, and then heat-cured while applying pressure to the laminate using a method such as press molding, autoclave molding, or sheet winding molding, to obtain the CFRP of this embodiment. Furthermore, copper foil or an organic film can be laminated when laminating the prepreg.

[0054] Furthermore, the CFRP of this embodiment can be obtained by molding using known methods other than the above-mentioned 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 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.

[0055] 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.

[0056] 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.

[0057] The cured product obtained in this embodiment can be used for various purposes other than the above-mentioned applications such as substrates and CFRP, etc. Specifically, general applications in which thermosetting resins such as epoxy resins are used can be mentioned, such as adhesives, paints, coating agents, insulating materials (including electric wire coatings), semiconductor encapsulants, etc.

[0058] When the curable resin composition of this embodiment is applied particularly to a semiconductor encapsulation material, 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 for 2 to 10 hours at 80 to 200° C. to obtain a cured product. Examples of semiconductor devices manufactured using this encapsulation material 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.

[0059] When the curable resin composition of this embodiment is used for substrate applications, 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, and chopped strand mat. 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 approximately 0.01 to 0.4 mm. Furthermore, a prepreg can be obtained by impregnating reinforcing fibers with the varnish and then heating and drying the varnish to produce a copper clad laminate (CCL). A laminate can also be produced using the curable resin composition of this embodiment by hot-press molding the resulting prepreg and CCL. The laminate is not particularly limited as long as it contains one or more prepregs, and may also contain any other layers. Furthermore, a sheet-like adhesive can be obtained by applying the epoxy resin varnish to a release film and then removing the solvent under heat to achieve a B-stage. This sheet-like adhesive can be used as an interlayer insulating layer in a multilayer substrate or as an adhesive sheet for mounting semiconductors. These curable resin compositions of this embodiment are suitable for use in printed wiring boards and also for special substrate materials such as package substrates and HDIs (high-density interconnects).

[0060] Examples of 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.

[0061] The present invention will be explained in more detail below with reference to synthesis examples and examples. The materials, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Various analytical methods used in the examples will be described below.

[0062] Various analytical methods were performed under the following conditions. Epoxy equivalent: Measured according to a method in accordance with JIS K-7236, and expressed in g / eq. Softening point: Measured according to a method in accordance with JIS K-7234, and expressed in °C. ICI viscosity: Measured according to a method in accordance with JIS K-7117-2, and expressed in Pa s.

[0063] GPC (gel permeation chromatography) analysis Manufacturer: Waters Column: Guard column SHODEX GPC KF-601, KF-602 KF-602.5, KF-603 Flow rate: 0.5 ml / min Column temperature: 40°C Solvent used: THF (tetrahydrofuran) Detector: RI (differential refractometer) NMR analysis Apparatus: AVANCE NEO 600 MHz (manufactured by Bruker) Measurement method: 13C (CDCl ３ ) Number of accumulations: 10,000 GC-MS analysis Apparatus: 6890N inert MSD (Agilent) Column: HP-5MS 15 m × 0.25 mm × 0.25 μm Carrier gas: He 1.0 mL / min (constant flow mode) Oven: 50 ° C (2 min) - 10 ° C / min - 300 ° C (23 min) Injection: 1 μL, Split 30:1, 300 ° C Ionization method: EI

[0064] Example 1 A flask equipped with a stirrer, a reflux condenser, and a stirring device was charged with 137 parts by weight of YS Polystar K125 (manufactured by Yasuhara Chemical Co., Ltd.) (in the above formula (2), m = 3.3, n = 4.4), 300 parts by weight of epichlorohydrin (ECH, the same applies hereinafter), 65 parts by weight of dimethyl sulfoxide (DMSO, the same applies hereinafter), and 6 parts by weight of water. The mixture was heated, stirred, and dissolved. After that, 21 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then further carried out at 65°C for 2 hours and at 70°C for 30 minutes. Next, excess epichlorohydrin was distilled off under heating and reduced pressure, and 314 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 90 parts by weight of water, 8 parts by weight of methanol, and 8 parts by weight of 30% aqueous sodium hydroxide solution were added. After reacting for 1 hour, the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then distilled off from the oil layer under heating and reduced pressure, yielding 149 parts by weight of solid epoxy resin. The resulting epoxy resin had an epoxy equivalent of 340 g / eq., a softening point of 100°C, an ICI viscosity of 1.03 Pa s (150°C), and a weight-average molecular weight of 830. The GPC results are shown in Figure 1.

[0065] Comparative Example 1 An epoxy resin was synthesized as follows, with reference to the synthesis method described in Example 1 of Cited Document 1. A flask equipped with a stirrer, reflux condenser, and stirring device was charged with 141 parts by weight of phenol and 1.4 parts by weight of boron trifluoride-diethyl ether complex. 34 parts by weight of limonene was added dropwise at 80°C over 1 hour, followed by stirring for an additional 2 hours. After washing with distilled water three times, unreacted phenol was removed by distillation under reduced pressure, yielding 62 parts by weight of a cyclic terpene skeleton-containing polyphenol compound. Next, 60 parts by weight of the cyclic terpene skeleton-containing polyphenol compound synthesized above, 171 parts by weight of epichlorohydrin, 74 parts by weight of DMSO, and 7 parts by weight of water were charged into a reaction vessel equipped with a stirrer, reflux condenser, and stirring device. After heating, stirring, and dissolution, 24 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 65°C. The mixture was then maintained at 65°C for 30 minutes to carry out the reaction. After the reaction was completed, the by-product salt and DMSO were removed by washing with water. Excess epichlorohydrin was then distilled off from the product under heating and reduced pressure. Methyl isobutyl ketone was then added to the residue to dissolve it, and 9 parts by weight of a 30% aqueous solution of sodium hydroxide was added. The reaction was allowed to proceed at 65°C for 1 hour. The reaction solution was then 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, yielding 61 parts by weight of a liquid epoxy resin. The resulting epoxy resin had an epoxy equivalent of 242 g / eq., an ICI viscosity of 0.04 Pa s (150°C), and a weight-average molecular weight of 450. The GPC results are shown in Figure 2.

[0066] The physical properties were measured under the following conditions. <Conditions for measuring heat resistance (Tg)> Dynamic viscoelasticity measuring device: TA-instruments, DMA-2980 Measurement temperature range: -30 to 280°C Heating rate: 2°C / min Tg: The peak point of Tan δ was taken as Tg. <Conditions for measuring flexural strength and elastic modulus> Device: Tensilon RTG-1310 (A&D) Sample size: Width 9 mm x Length 64 mm x Thickness 4 mm Standard: Conforms to JIS K-6911 <IZOD impact test> Device: IZOD impact tester DG-IB (Toyo Seiki Seisakusho, Ltd.) Sample size: 5 cm diameter x 4 mm thick disc Standard: Conforms to JIS K-6911

[0067] [Example 2, Comparative Example 2] The epoxy resins obtained in Example 1 and Comparative Example 1 were used as the base resin, and phenol novolak resin (manufactured by Gun-ei Chemical Co., Ltd., softening point 83.6°C) was used as the curing agent, and TPP (manufactured by Hokko Chemical Industry Co., Ltd.: triphenylphosphine) was used as the curing accelerator. These were mixed in the weight ratios shown in Table 1, and cured under the curing conditions of 160°C x 2 hours and 180°C x 6 hours to produce cured products.

[0068] [Example 3, Comparative Example 3] The epoxy resins obtained in Example 1 and Comparative Example 1 were used as the base resin, and 4,4'-methylenebis(2,6-diethylaniline) (abbreviation: M-DEA, manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the curing agent. These were mixed in the weight ratios shown in Table 1, and cured at 160°C for 6 hours to produce cured products.

[0069]

[0070] The results in Table 1 confirm that the cured products of the examples of the present invention are excellent in heat resistance and mechanical properties.

Claims

1. An epoxy resin obtained by reacting a phenol compound represented by the following formula (1) with epihalohydrin. (In formula (1), C １ and C. ２ Between ２ and C. ３ Between ３ and C. ４ Between ４ and C. ５ Between ５ and C. ６ Between and C ６ and C. １ The dotted line between indicates that a single bond or a double bond may be present within the range permitted by the atomic valence. m and n are the average values ​​of the repeating numbers, and m is a real number satisfying 1<m≦5 and n is a real number satisfying 1<n≦10.) 2. The epoxy resin according to claim 1, wherein the phenol compound represented by formula (1) is obtained by adding a phenol to a cyclic terpene compound.

3. The epoxy resin according to claim 1, having an epoxy equivalent of 280 g / eq. or more and 600 g / eq. or less.

4. The epoxy resin according to claim 1, wherein the phenol compound represented by the formula (1) is YS Polystar K125 (trade name, manufactured by Yasuhara Chemical Co., Ltd.).

5. A curable resin composition comprising the epoxy resin according to any one of claims 1 to 3 and a curing agent.

6. A cured product obtained by curing the curable resin composition according to claim 5.

7. A carbon fiber reinforced composite material obtained by curing the curable resin composition according to claim 5.

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