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

Abstract

Invention details;

Description

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

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

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

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

[0004] In recent years, the required properties of CFRP have become stricter, and when used as a structural material for aerospace applications and vehicles, heat resistance of 180°C or higher and bending strength of 100 MPa or higher are required (Patent Documents 4 and 5).

[0005] Japanese Patent Publication No. 60-243113 Japanese Patent Publication No. 09-100358 Japanese Patent Publication No. 2013-155330 Japanese Patent Publication No. 2010-275492 International Publication No. 2019-021879 Japanese Patent Publication No. 2007-211254

[0006] Patent Document 6 describes a low water-absorbent epoxy resin. However, the epoxy resin described in Patent Document 6 has low bending strength and is brittle (has low elongation), 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, a curable resin composition, and cured products thereof, and a carbon fiber reinforced composite material, which are excellent in heat resistance and flexural strength.

[0008] That is, the present invention is as shown in the following [1] to [5]. In the present invention, "(Numerical value 1) to (Numerical value 2)" indicates that the upper and lower limits are included. [1] An epoxy resin represented by the following formula (1) and having an epoxy equivalent of 210 g / eq. or more and 218 g / eq. or less.

[0009]

[0010] (In formula (1), n ​​is the average number of repeating units and is a real number in the range of 1<n<15.) [2] A curable resin composition containing the epoxy resin according to the preceding item [1] and a curing agent. [3] The curable resin composition according to the preceding item [2], wherein the curing agent is an amine-based curing agent. [4] A cured product obtained by curing the curable resin composition according to the preceding item [2] or [3]. [5] A carbon fiber reinforced composite material comprising a cured product obtained by curing the curable resin composition according to the preceding item [2] or [3], and carbon fibers.

[0011] According to the present invention, it is possible to provide an epoxy resin, a curable resin composition, and a cured product thereof, and a carbon fiber reinforced composite material, the cured product of which has excellent heat resistance and flexural strength.

[0012] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in further detail.

[0013] The epoxy resin of this embodiment is represented by the following formula (1), and the epoxy equivalent is preferably 210 g / eq. or more and 218 g / eq. or less, more preferably 211 g / eq. or more and 218 g / eq. or less, and even more preferably 213 g / eq. or more and 218 g / eq. or less. When the epoxy equivalent is 210 g / eq. or more, heat resistance is good, and when it is 218 g / eq. or less, flexural strength is good. In other words, when the epoxy equivalent is 210 g / eq. or more and 218 g / eq. or less, heat resistance and flexural strength properties can both be achieved.

[0014]

[0015] (In formula (1), n ​​is the average number of repetitions and is a real number in the range of 1<n<15.)

[0016] In the formula (1), the value of n can be calculated from the number average molecular weight of the epoxy resin determined by gel permeation chromatography (GPC, detector: RI) or the area ratio of each separated peak. n is preferably a real number in the range of 1<n<15, more preferably 1<n<10, and particularly preferably 1<n<5.

[0017] By controlling the epoxy equivalent, the epoxy resin of this embodiment can produce a cured product with excellent heat resistance and flexural strength. The flexural strength is preferably 100 to 130 MPa, more preferably 105 to 125 MPa, and even more preferably 110 to 120 MPa. A flexural strength of less than 100 MPa is not preferable because the flexural strength of the resulting carbon fiber reinforced composite material is insufficient, resulting in reduced reliability. The flexural strength of this embodiment is measured by the method described in the Examples below.

[0018] Furthermore, it is particularly preferable that the maximum bending elongation of the cured product obtained from the epoxy resin of this embodiment is 5% or more. There is no particular limit to the maximum value, but a preferred maximum value is 7% or less. By ensuring that the maximum bending elongation is 5% or more, the brittleness of the cured product can be reduced, resulting in a tough cured product.

[0019] The glass transition point (Tg) of the epoxy resin of this embodiment is preferably 180 to 300°C, more preferably 185 to 250°C, even more preferably 190 to 200°C, and particularly preferably 220 to 250°C. A glass transition point below 180°C is undesirable because it is difficult to apply to components requiring heat resistance, such as those around aircraft engines, and the resin softens during use, significantly reducing mechanical strength and leading to material damage. Furthermore, the glass transition point of an epoxy resin generally correlates with crosslink density, and the higher the crosslink density, the higher the glass transition point. In other words, a glass transition point above 300°C is undesirable because the crosslink density increases and the cured product becomes brittle. The glass transition point (Tg) of this embodiment is measured using the method described in the Examples below.

[0020] The epoxy resin represented by the formula (1) can be obtained by reacting a phenolic resin represented by the following formula (2) with epihalohydrin.

[0021]

[0022] (In formula (2), n is the average number of repetitions and is a real number in the range of 1<n<15.)

[0023] The preferred range of n in the formula (2) is the same as that in the formula (1).

[0024] The epihalohydrin is readily available on the market. The amount of epihalohydrin used is preferably 2.0 to 10 mol, more preferably 3.0 to 8.0 mol, and even more preferably 3.5 to 6.0 mol, per mol of hydroxyl groups in the raw material phenol mixture. 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.

[0025] In the above reaction, an alkali metal hydroxide can be used as a catalyst to promote the epoxidation step. Usable alkali metal hydroxides include sodium hydroxide and potassium hydroxide. A solid alkali metal hydroxide may be used, or an aqueous solution of the alkali metal hydroxide may be used. In this embodiment, it is particularly preferable to use a solid alkali metal hydroxide formed into flakes in terms of solubility and handling. The amount of alkali metal hydroxide used is preferably 0.90 to 1.5 mol, more preferably 0.95 to 1.25 mol, and even more preferably 0.99 to 1.15 mol, per mol of hydroxyl groups in the raw material phenol mixture.

[0026] 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.

[0027] The reaction temperature is preferably 30 to 90°C, more preferably 35 to 80°C. In particular, in this embodiment, for higher purity epoxidation, a temperature of 50°C or higher is preferred, and 60°C or higher is particularly preferred. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, and particularly preferably 1 to 3 hours. A short reaction time is not preferred because the reaction does not proceed to completion, while a long reaction time is not preferred because by-products are produced.

[0028] 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 preferably 0.01 to 0.3 mol, more 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 preferably 50 to 120°C, and the reaction time is more preferably 0.5 to 2 hours.

[0029] 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.

[0030] In the synthesis method of the phenolic resin represented by the formula (2), when furfural is reacted (condensed) with a phenol, the amount of the phenol is preferably 1.5 to 20 moles, particularly preferably 3 to 10 moles, per mole of furfural.

[0031] Examples of phenols include disubstituted phenols such as catechol, resorcinol, and hydroquinone, and monosubstituted phenols such as phenol, cresol, and xylenol, and these may be used alone or in combination of two or more.

[0032] Examples of the solvent include, but are not limited to, methanol, ethanol, propanol, isopropanol, toluene, xylene, 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 phenol.

[0033] A basic catalyst is preferably used in the condensation reaction of furfural and phenols. Condensation polymerization is also possible with an acidic catalyst, but reactions between furfurals occur, resulting in increased by-products. Alternatively, an organometallic compound can be used as a catalyst, but this is cost-inefficient. Specific examples of basic catalysts include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, and potassium tert-butoxide; and alkaline earth metal alkoxides such as magnesium methoxide and magnesium ethoxide. However, the basic catalyst is not limited to these, and may be used alone or in combination of two or more. The amount of catalyst used is preferably 0.005 to 2.0 times, more preferably 0.01 to 1.1 times, the moles per mole of phenol.

[0034] The condensation reaction in the presence of these basic catalysts is preferably carried out in the range of 40 to 180°C, particularly preferably in the range of 80 to 165°C. The time for the condensation reaction can be selected preferably in the range of 0.5 to 10 hours. The reaction product thus obtained is neutralized to neutralize the system or repeatedly washed with water in the presence of a solvent, and then the water is separated and drained, and the solvent and unreacted materials are removed under heating and reduced pressure to obtain the phenolic resin represented by formula (2).

[0035] The curable resin composition of the present embodiment contains a curing agent. Examples of curing agents that can be used include amine-based curing agents, acid anhydride-based curing agents, amide-based curing agents, and phenol-based curing agents.

[0036] In the curable resin composition of the present embodiment, an amine-based curing agent is preferred, since it can achieve a good balance between the resin viscosity of the curable resin composition and the heat resistance of the cured resin. Examples of amine-based curing agents include 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diaminodiphenyl sulfone (4,4'-DDS), diaminodiphenylmethane (DDM), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane (TEDDM), 3,3'-diisopropyl-5,5'-diethyl-4 ,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2-(dimethylaminomethyl)phenol (DMP-10), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), 2-ethylhexanoic acid ester of 2,4,6-tris(dimethylaminomethyl)phenol, and the like can be used. Other examples include aniline novolak, orthoethylaniline novolak, aniline resins obtained by reacting aniline with xylylene chloride, and aniline resins obtained by polycondensation of aniline with substituted biphenyls (4,4'-bis(chloromethyl)-1,1'-biphenyl, 4,4'-bis(methoxymethyl)-1,1'-biphenyl, etc.) or substituted phenyls (1,4-bis(chloromethyl)benzene, 1,4-bis(methoxymethyl)benzene, 1,4-bis(hydroxymethyl)benzene, etc.).

[0037] 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.

[0038] Examples of the amide-based curing agent include dicyandiamide, or a polyamide resin synthesized from a dimer of linolenic acid and ethylenediamine.

[0039] 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.

[0040] In the curable resin composition of this embodiment, it is also preferable to use the phenol resin represented by the formula (2) as the entire amount of the curing agent or as a part thereof.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The curable resin composition of the present embodiment may contain known additives as needed. Specific examples of the additives that can be used include polybutadiene and its modified products, modified acrylonitrile copolymers, polyphenylene ether, polystyrene, polyethylene, polyimide, fluororesin, maleimide compounds, cyanate ester compounds, silicone gel, silicone oil, inorganic fillers such as silica, alumina, calcium carbonate, quartz powder, aluminum powder, graphite, talc, clay, iron oxide, titanium oxide, aluminum nitride, asbestos, mica, and glass powder, surface treatment agents for fillers such as silane coupling agents, release agents, and colorants such as carbon black, phthalocyanine blue, and phthalocyanine green.

[0045] 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.

[0046] The curable resin composition of this embodiment can be made into a varnish-like composition (hereinafter simply referred to as "varnish") by adding an organic solvent. Examples of the solvent that can be used include amide-based solvents such as γ-butyrolactones, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylimidazolidinone; sulfones such as tetramethylene sulfone; ether-based solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate, and propylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone; and aromatic solvents such as toluene and xylene. The solvent is used so that the solids concentration excluding the solvent in the resulting varnish is preferably 10 to 80 wt %, more preferably 20 to 70 wt %.

[0047] The curable resin composition of this embodiment can also be used as a resin sheet, prepreg, or carbon fiber reinforced composite material. The curable resin composition of this embodiment can be applied to one or both sides of a support substrate and used as a resin sheet. Examples of application methods include casting, extruding the resin through a nozzle or die using a pump or extruder, adjusting the thickness with a blade, calendering the resin with a roll to adjust the thickness, and spraying using a sprayer. The layer formation process may be performed while heating within a temperature range that avoids thermal decomposition of the curable resin composition. If necessary, rolling, grinding, or other processes may also be performed. Examples of support substrates include, but are not limited to, porous substrates made of paper, cloth, nonwoven fabric, etc.; plastic films or sheets such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; nets; foams; metal foils; and laminates thereof. The thickness of the support substrate is not particularly limited and can be determined appropriately depending on the application.

[0048] The curable resin composition and / or resin sheet of this embodiment can be heated and melted to reduce the viscosity, and then impregnated into a fiber substrate to obtain the prepreg of this embodiment.

[0049] Alternatively, the prepreg of this embodiment can be obtained by impregnating a fiber substrate with a varnish-like curable resin composition and drying it by heating. The prepreg is cut into a desired shape, laminated, and then the curable resin composition is heat-cured while applying pressure to the laminate by press molding, autoclave molding, sheet winding, or the like, to obtain the carbon fiber reinforced composite material of this embodiment. Copper foil or an organic film can also be laminated during lamination of the prepreg.

[0050] Furthermore, the carbon fiber reinforced composite material of this embodiment can be obtained by molding using known methods other than the above-mentioned methods. For example, a resin transfer molding technique (RTM method) can be used, in which a carbon fiber substrate (usually a carbon fiber fabric) is cut, laminated, and shaped to produce a preform (a preform before being impregnated with a resin), the preform is placed in a mold, the mold is closed, resin is injected to impregnate the preform, and the resin is cured, and the mold is then opened to remove the molded product. Also usable are types of RTM methods, such as the VaRTM method, the SCRIMP (Seeman's Composite Resin Infusion Molding Process), and the CAPRI (Controlled Atmospheric Pressure Resin Infusion) method, which is described in 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.

[0051] 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.

[0052] 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.

[0053] The present invention will be explained in more detail below with reference to synthesis examples and examples. The materials, processing details, processing procedures, etc. shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0054] The analysis was carried out under the following conditions. Epoxy equivalent: Measured according to the method specified in JIS K7236. The unit is g / eq. 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 refractive index detector)

[0055] Synthesis Example 1: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 63 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 112 parts by weight of the phenolic resin represented by the formula (2). 78 parts by weight of the obtained phenolic resin represented by formula (2) were charged into a reaction vessel, followed by heating and stirring. After dissolving the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide were added in portions over 2 hours while maintaining the solution temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. The mixture was then repeatedly washed with water to remove by-product salts and dimethyl sulfoxide. The excess epichlorohydrin was then removed from the oil layer under reduced pressure and heating. 218 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 7 parts by weight of a 30% aqueous sodium hydroxide solution was added. The reaction mixture was then repeatedly washed with water until the wash solution became neutral. Then, methyl isobutyl ketone was distilled off from the oil layer under heating and reduced pressure to obtain 101 parts by weight of the epoxy resin represented by the above formula (1) (n in formula (1) is 2.2). The epoxy equivalent of the obtained epoxy resin was 218 g / eq.

[0056] Synthesis Example 2: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 53 parts by weight of furfural was added dropwise over 2 hours. The mixture was then reacted at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was reacted for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of a phenolic resin represented by Formula (2). 78 parts by weight of the obtained phenolic resin represented by Formula (2) were charged into a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was removed from the oil layer under heating and reduced pressure, and 218 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 7 parts by weight of 30% aqueous sodium hydroxide was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then removed from the oil layer under heating and reduced pressure by distillation, yielding 103 parts by weight of an epoxy resin represented by the above formula (1) (n in formula (1) is 2.1). The epoxy equivalent of the resulting epoxy resin was 213 g / eq.

[0057] Synthesis Example 3: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 44 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 109 parts by weight of a phenolic resin represented by Formula (2). 78 parts by weight of the resulting phenolic resin represented by Formula (2) were charged into a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, followed by heating and stirring. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was removed from the oil layer under heating and reduced pressure, and 218 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 7 parts by weight of 30% aqueous sodium hydroxide was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then removed from the oil layer under heating and reduced pressure by distillation, yielding 103 parts by weight of an epoxy resin represented by the above formula (1) (n in formula (1) is 2.0). The epoxy equivalent of the resulting epoxy resin was 211 g / eq.

[0058] Synthesis Example 4: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 90 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, and then heated to 145°C. During the temperature increase, the distilled water was removed from the system. After reaching 145°C, the mixture was allowed to react for 4 hours. The mixture was then cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 120 parts by weight of a phenolic resin represented by Formula (2). 78 parts by weight of the obtained phenolic resin represented by Formula (2) were charged into a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, and the mixture was heated and stirred. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was removed from the oil layer under heating and reduced pressure, and 218 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 7 parts by weight of 30% aqueous sodium hydroxide was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then removed from the oil layer under heating and reduced pressure by distillation, yielding 90 parts by weight of an epoxy resin represented by the above formula (1) (n in formula (1) is 2.6). The epoxy equivalent of the resulting epoxy resin was 223 g / eq.

[0059] Synthesis Example 5: 254 parts by weight of phenol, 63 parts by weight of water, and 27 parts by weight of sodium hydroxide were charged into a flask equipped with a stirrer, reflux condenser, and heater. After stirring and dissolving, the mixture was heated to 110°C, and 33 parts by weight of furfural was added dropwise over 2 hours. The mixture was then allowed to react at 110°C for 3 hours, after which the temperature was raised to 145°C. During the temperature increase, the distilled water was removed from the system. Immediately after reaching 145°C, the mixture was cooled to 80°C, and 63 parts by weight of water was charged. 4 parts by weight of phosphoric acid and 63 parts by weight of 35% hydrochloric acid were added for neutralization. After repeated water washing, unreacted phenol was distilled off under reduced pressure with heating to obtain 90 parts by weight of a phenolic resin represented by Formula (2). 78 parts by weight of the resulting phenolic resin represented by Formula (2) were charged into a reaction vessel with 254 parts by weight of ECH, 64 parts by weight of DMSO, and 13 parts by weight of water, followed by heating and stirring. After dissolution of the phenolic resin and ECH, 23 parts by weight of flaky sodium hydroxide was added in portions over 2 hours while maintaining the temperature at 45°C. The reaction was then continued for 2 hours at 45°C and 60 minutes at 70°C. After repeated water washing to remove by-product salts and dimethyl sulfoxide, excess epichlorohydrin was removed from the oil layer under heating and reduced pressure, and 218 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 7 parts by weight of 30% aqueous sodium hydroxide was added. The reaction was allowed to proceed for 1 hour, after which the reaction solution was repeatedly washed with water until the washings became neutral. The methyl isobutyl ketone was then removed from the oil layer under heating and reduced pressure by distillation, yielding 109 parts by weight of an epoxy resin represented by the above formula (1) (n in formula (1) is 1.7). The epoxy equivalent of the resulting epoxy resin was 204 g / eq.

[0060] [Examples 1 to 3, Comparative Examples 1 and 2] The epoxy resins obtained in Synthesis Examples 1 to 5 were used as the base resin, and 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane (abbreviation: TEDDM, manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent: 78 g / eq.) was used as the curing agent. These were mixed in the weight ratios shown in Table 1, and cured at 160°C for 6 hours to produce cured products.

[0061] Physical properties were measured under the following conditions. <Conditions for measuring glass transition point (Tg)> Dynamic viscoelasticity measuring device: TA-instruments, DMA-2980 Measurement temperature range: -30 to 280°C Heating rate: 2°C / min Tg: The peak temperature of the loss modulus was taken as Tg. <Conditions for measuring flexural strength and maximum flexural elongation> Measurements were made in accordance with JIS K-7074.

[0062]

[0063] The results in Table 1 confirm that the cured products of Examples 1 to 3 of the present invention have high glass transition temperatures, excellent heat resistance, and excellent flexural strength. On the other hand, it was confirmed that Comparative Example 1 has problems with flexural strength and maximum flexural elongation, and Comparative Example 2 has problems with heat resistance.

[0064] This application claims priority based on Japanese Patent Application No. 2023-113998, filed July 11, 2023.

Claims

DEPCT691. Epoxy resin which is represented by the following formula(1) and has an epoxy equivalent of 210 g / equivalent or more and 218 g / equivalent or less:[Chemistry1](Chemistry formula)(1)In formula(1), n ​​is the average number of repeating units and is a real number in the range 1. <n<152.องค์ประกอบเรซินที่สามารถบ่มได้ที่ประกอบรวมด้วยอีพอกซีเรซินตามข้อถือสิทธิที่1และสารช่วยบ่ม3.องค์ประกอบเรซินที่สามารถบ่มได้ตามข้อถือสิทธิที่2,ที่ซึ่งสารช่วยบ่มคือสารช่วยบ่มที่มีพื้นฐานเป็นเอมีน4.ผลิตภัณฑ์ซึ่งถูกบ่มซึ่งได้มาโดยการบ่มองค์ประกอบเรซินที่สามารถบ่มได้ตามข้อถือสิทธิที่2หรือ35.วัสดุคอมโพสิตที่เสริมแรงด้วยเส้นใยคาร์บอนที่ประกอบรวมด้วยผลิตภัณฑ์ซึ่งถูกบ่มซึ่งได้มาโดยการบ่มองค์ประกอบเรซินที่สามารถบ่มได้ตามข้อถือสิทธิที่2หรือ3,และเส้นใยคาร์บอน;