Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
  • C08G59/22—Di-epoxy compounds
  • C08G59/24—Di-epoxy compounds carbocyclic
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/62—Alcohols or phenols
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs

Definitions

• the present invention relates to epoxy resin compositions, reinforcing fiber-containing epoxy resin compositions, prepregs, and fiber-reinforced plastics using these.
• Fiber reinforced plastic exhibits excellent physical properties such as light weight and high strength, and is used in many fields. Among them, those using carbon fiber as a reinforcing fiber (CFRP) are known to be particularly excellent in mechanical strength.
• Epoxy resin is mainly used as the base material resin for FRP because it has an excellent balance of price and physical properties. Epoxy resins are also known to exhibit good mechanical properties as base material resins for CFRP because they form good adhesive surfaces with reinforcing fibers due to their secondary hydroxyl groups.
• thermoplastic resin as the base material resin
• FRTP thermoplastic resin
• Nylon, polypropylene, polycarbonate, etc. are mainly used as the base material resin of FRTP.
• a problem with FRTP is that the 90-degree bending strength of unidirectional materials (UD materials) is low due to the low adhesion between reinforcing fibers and resin.
• various methods are being considered for modifying the reinforcing fiber surface, such as washing the sizing agent attached to the fiber and oxidizing the fiber surface with ozone or acid.
• all require additional steps and are not convenient (Non-Patent Document 1).
• thermoplastic epoxy resin has been proposed as a thermoplastic resin that improves adhesion to reinforcing fibers. Since the in-situ polymerizable thermoplastic epoxy resin is impregnated into fibers in a low viscosity state before polymerization, it has good impregnation properties and can increase the ratio of reinforcing fibers. Also, due to the presence of the secondary hydroxyl group of the epoxy resin, good adhesion to the reinforcing fiber is expected.
• Non-Patent Document 2 the interfacial shear strength between carbon fiber and base material increases as the molecular weight of thermoplastic epoxy increases.
• thermoplastic epoxy resin it is necessary to spend a sufficient amount of time for polymerization in order to sufficiently increase the molecular weight within the reinforcing fibers of the thermoplastic epoxy resin.
• the skeleton of the thermoplastic epoxy resin is made bulky for high heat resistance, the steric hindrance of the reaction becomes large, so that the curing time for polymerization becomes longer, resulting in poor productivity. Therefore, there has been a demand for a method for improving the adhesiveness of a thermoplastic epoxy resin to reinforcing fibers and improving the flexural strength in the 90-degree direction by a simple method with excellent productivity.
• the present invention provides an epoxy resin composition comprising a bifunctional phenol compound, a bifunctional epoxy resin and a polymerization catalyst as essential components,
• a bifunctional epoxy resin containing 50% by weight or more of a bifunctional epoxy resin (a) represented by the following formula (1)
• the bifunctional epoxy resin is 1.01 to 1.05 mol per 1 mol of the bifunctional phenol compound
• the polymer obtained from the epoxy resin composition is a thermoplastic epoxy resin, and its epoxy equivalent is 5000 g/eq. 20000 g/eq. , a bending strength of 70 MPa or more, and a component that becomes insoluble when dissolved in tetrahydrofuran is 10% by weight or less in the polymer.
• a in formula (1) is represented by formula (2), n is the number of repetitions, and its average value is 0-5.
• X is a single bond, a hydrocarbon group having 1 to 13 carbon atoms, —O—, —CO—, —COO—, —S—, —SO 2 —, and Y 1 independently has 1 carbon atom; an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms, and Y 2 and Y 3 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 10 carbon atoms. is either
• the present invention also provides a reinforcing fiber-containing epoxy resin composition or prepreg obtained by mixing the above epoxy resin composition and reinforcing fibers.
• the reinforcing fibers are preferably PAN-based carbon fibers, and are preferably contained in the resin composition or prepreg at a ratio of 50% by weight or more and 80% by weight or less.
• the present invention also provides a fiber-reinforced plastic using the reinforcing fiber-containing epoxy resin composition or the prepreg.
• the present invention can provide a thermoplastic epoxy resin composition with excellent adhesion to reinforcing fibers.
• the adhesiveness to a reinforcing fiber can be demonstrated by the simple method of adjusting the preparation ratio of a raw material.
• the epoxy resin composition of the present invention is a composition that contains a bifunctional phenol compound, a bifunctional epoxy resin and a polymerization catalyst as essential components and can be polymerized by heating. It may contain organic solvents and additives such as fillers and flame retardants.
• the bifunctional epoxy resin contains 50% by weight or more of the epoxy resin (a) represented by the formula (1) as an essential component. It is preferably 66% by weight or more, more preferably 75% by weight or more, and still more preferably 80% by weight or more.
• Epoxy resin (a) constitutes part of a bifunctional epoxy resin. Moreover, the epoxy equivalent of the bifunctional epoxy resin is 150 to 350 g/eq. is preferred.
• A is a divalent group represented by formula (2) above.
• n is the number of repetitions, and its average value is 0-5, preferably 0-1.
• X is a single bond, a hydrocarbon group having 1 to 13 carbon atoms, -O-, -CO-, -COO-, -S- or -SO 2 -.
• the hydrocarbon group having 1 to 13 carbon atoms is preferably an alkylene group having 1 to 9 carbon atoms or an arylene group having 6 to 13 carbon atoms, such as —CH 2 —, —CH(CH 3 )—, —C( CH 3 ) 2 —, —C(CF 3 ) 2 —, —CHPh—, —C(CH 3 )Ph—, 1,1-cyclopropylene group, 1,1-cyclobutylene group, 1,1-cyclopentyl rene group, 1,1-cyclohexylene group, 4-methyl-1,1-cyclohexylene group, 3,3,5-trimethyl-1,1-cyclohexylene group, 1,1-cyclooctylene group, 1, 1-cyclononylene group
• Y 1 is independently either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms.
• alkyl groups having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group and t-butyl group. mentioned.
• the aryl group having 6 to 10 carbon atoms include phenyl group, tolyl group, ethylphenyl group, xylyl group, n-propylphenyl group, isopropylphenyl group, mesityl group and naphthyl group.
• methyl group, ethyl group, n-propyl group, n-butyl group, t-butyl group, phenyl group, tolyl group, xylyl group or naphthyl group are preferred, and methyl group, ethyl group and n-propyl group.
• n-butyl group, t-butyl group, phenyl group, or tolyl group are more preferred.
• Y 2 is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and is preferably a group other than a hydrogen atom. Examples of the alkyl group and the aryl group are the same as the groups exemplified for Y 1 above. Preferred Y2 is the same as Y1 . Y 3 is independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 10 carbon atoms. Examples of the alkyl group and aryl group are the same as the groups exemplified for Y1 . Preferred Y3 is a hydrogen atom or the same groups as those exemplified for Y1.
• bifunctional epoxy resin (a) for example, tetramethylbisphenol F type epoxy resin (eg, YSLV-80XY (manufactured by Nippon Steel Chemical & Materials Co., Ltd.), etc.), tetramethylbiphenol type epoxy resin (eg, YX-4000 (manufactured by Mitsubishi Chemical Co., Ltd.), etc.), biscresol fluorene-type epoxy resins (eg, OGSOL CG-500 (manufactured by Osaka Gas Chemicals Co., Ltd.), etc.).
• epoxy resins other than the epoxy resin (a) can be used together as long as they are bifunctional epoxy resins, and the purity thereof is preferably 95% or more. If the purity as a bifunctional epoxy resin is high, positional isomers and oligomers may be included.
• epoxy resins that can be used in combination with the epoxy resin (a) include bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin, bisphenolacetophenone-type epoxy resin, diphenyl sulfide-type epoxy resin, diphenyl ether-type epoxy resin, and bisphenol.
• Bisphenol-type epoxy resins such as fluorene-type epoxy resins, biphenol-type epoxy resins, diphenyldicyclopentadiene-type epoxy resins, alkylene glycol-type epoxy resins, dihydroxynaphthalene-type epoxy resins, and dihydroxybenzene-type epoxy resins can be mentioned.
• the bifunctional epoxy resin that can be used in combination with the epoxy resin (a) is preferably less than 50% by weight, more preferably less than 30% by weight, of the total epoxy resin. If the content exceeds 50% by weight, gelation occurs to generate a component that is difficult to dissolve in a solvent, which may deteriorate reshaping properties.
• the content of monofunctional impurities is preferably 2% by weight or less with respect to the bifunctional epoxy resin. If tri- or higher-functional impurities are contained, a crosslinked structure is likely to be formed starting from the impurities, which may increase the dispersion of the polymer and may cause gelation to impair thermoplasticity. Therefore, it is preferable that the tri- or higher-functional impurities be 1% by weight or less relative to the difunctional epoxy resin.
• An impurity component that does not have an active group that reacts with either the epoxy resin or the phenolic hydroxyl group and that does not inhibit the polymerization reaction by itself may decrease the molecular weight after polymerization if the amount increases. Therefore, it is preferably 2% by weight or less with respect to the bifunctional epoxy resin.
• the bifunctional phenol compound used in the epoxy resin composition of the present invention is a compound having two phenolic hydroxyl groups in one molecule, and preferably has a purity of 95% by weight or more. Further, if the purity as a bifunctional phenol compound is high, positional isomers may be contained. When monofunctional impurities are contained, the molecular weight after polymerization does not increase, so that the produced thermoplastic resin may have poor mechanical properties. Therefore, the content of monofunctional impurities is preferably 2% by weight or less with respect to the bifunctional phenol compound. If tri- or higher-functional impurities are contained, a crosslinked structure is likely to be formed starting from the impurities, which may increase the dispersion of the polymer and may cause gelation to impair thermoplasticity.
• trifunctional or higher functional impurities are preferably 1% by weight or less with respect to the bifunctional phenol compound.
• An impurity component that does not have an active group that reacts with either the epoxy resin or the phenolic hydroxyl group and that does not inhibit the polymerization reaction by itself may decrease the molecular weight after polymerization if the amount increases. Therefore, it is preferably 2% by weight or less with respect to the bifunctional phenol compound.
• the bifunctional phenol compound is preferably a bisphenol compound or a biphenol compound.
• bisphenol compounds include bisphenol A, bisphenol F (manufactured by Nippon Steel Chemical & Materials Co., Ltd.), bisphenol fluorene (manufactured by Osaka Gas Chemicals Co., Ltd.), Bis-E, Bis-Z, BisOC-FL, BisP- AP, BisP-CDE, BisP-HTG, BisP-MIBK, BisP-3MZ, S-BOC (manufactured by Honshu Chemical Industry Co., Ltd.), bisphenol S and the like.
• biphenol compounds include biphenol, dimethylbiphenol, tetramethylbiphenol and the like.
• bifunctional phenol compounds examples include benzenediols such as hydroquinone, methylhydroquinone, dibutylhydroquinone, resorcinol, methylresorcinol, catechol and methylcatechol, and naphthalene diols such as naphthalene diol.
• bisphenol compounds or biphenol compounds are preferred.
• the ratio of the bifunctional epoxy resin contained in the epoxy resin composition of the present invention is 1.01 to 1.05 mol, preferably 1.02 to 1.03 mol, per 1 mol of the bifunctional phenol compound. .
• the epoxy resin and the phenol compound react successively to form a straight chain structure, thereby exhibiting thermoplasticity.
• the epoxy resin is excessive, the epoxy group terminal is formed, and when the phenol compound is excessive, the phenol group terminal is formed and the reaction is completed.
• the proportion of the epoxy resin is less than 1.01 mol, the polymer tends to have a phenol group terminal, and there is a risk that the adhesion to the reinforcing fiber will not be exhibited.
• the proportion of the epoxy resin exceeds 1.05 mol, unreacted epoxy resin components remain in the resin even after the polymerization reaction is completed, which may adversely affect the strength of the resin.
• the epoxy resin composition if the phenolic compound exists in the epoxy resin in a crystalline state, the molar ratio deviates from the design when viewed microscopically. If the reaction is started in this state, the polymerization may not progress sufficiently. In order to allow the polymerization to proceed sufficiently, an epoxy resin composition in which the phenol compound and the epoxy resin are uniformly dissolved (compatibility) with each other is preferred. In addition, it is desirable that the epoxy resin composition is completely dissolved or in a uniform liquid state before the reinforcing fibers are blended.
• the haze value in the thickness direction is measured by adding the molten mixture, if the haze value in the thickness direction is less than 30%, it is determined that the mixture has dissolved or become a uniform liquid to a level that does not affect the polymerization reaction.
• the haze value is more preferably less than 20%, still more preferably less than 10%.
• polymerization catalyst used in the epoxy resin composition known catalysts can be used. Specific examples include phosphorus-based polymerization catalysts such as triphenylphosphine, tris(paratoluyl)phosphine, tris(orthotoluyl)phosphine, and tris(paramethoxyphenyl)phosphine.
• phosphorus-based polymerization catalysts such as triphenylphosphine, tris(paratoluyl)phosphine, tris(orthotoluyl)phosphine, and tris(paramethoxyphenyl)phosphine.
• Other polymerization catalysts include imidazole compounds such as 1B2MZ, 1B2PZ and TBZ (manufactured by Shikoku Kasei Kogyo Co., Ltd.).
• the above polymerization catalyst is desirably 0.05% by weight or more and 5% by weight or less with respect to the total amount of the resin composition comprising the bifunctional epoxy resin and the bifunctional phenol compound. If the content is less than 0.05% by weight, in situ polymerization may take a long time, resulting in a decrease in productivity, and there is also a risk of deactivation for some reason before the target molecular weight is reached. If it exceeds 5% by weight, while the polymerization reaction proceeds rapidly, the storage stability may be impaired, which may cause problems with process compatibility. , there is a risk of impairing the physical properties after polymerization, and it is also economically disadvantageous because it is simply expensive.
• the epoxy resin composition may contain an organic solvent as a solvent for the polymerization catalyst or for viscosity adjustment.
• the organic solvent to be used is not particularly limited as long as it does not inhibit the reaction between the epoxy resin and the phenolic compound, but hydrocarbon-based, ketone-based, and ether-based solvents are preferred in terms of availability. Specific examples include toluene, xylene, acetone, methyl ethyl ketone, isobutyl ketone, cyclopentanone, cyclohexanone, and diethylene glycol dimethyl ether.
• the proportion of the organic solvent is desirably 5% by weight or less with respect to the total weight of the epoxy resin composition.
• the progress of the polymerization of the epoxy resin composition should be judged by the transition of the epoxy equivalent of the polymer. If the heating is performed for less than 1 hour, the epoxy equivalent tends to increase, and there is a possibility that the polymerization has not progressed sufficiently. After heating for 1 hour or more, the epoxy equivalent did not substantially increase from the value at the time of 1 hour, and it can be judged that the polymerization proceeded sufficiently. Accordingly, the polymerization conditions for obtaining a polymer from the epoxy resin composition were heating at 160° C. for 1 hour. In the present invention, the polymer for measuring the tetrahydrofuran (THF)-insoluble matter is polymerized under these conditions.
• THF tetrahydrofuran
• the progress of the polymerization of the reinforcing fiber-containing epoxy resin composition and the prepreg was also judged by the transition of the epoxy equivalent in the same way as the progress of the polymer. If the heating time is less than 4 hours, the epoxy equivalent tends to increase, and the polymerization may not proceed sufficiently. After heating for 4 hours or more, the epoxy equivalent did not substantially increase from the value obtained at 4 hours, and it was judged that the polymerization proceeded sufficiently. In the case of the epoxy resin composition in which fibers are combined, the epoxy equivalent is almost the same by setting the heating time to four times that of the epoxy resin composition alone. It is considered that this is because the reaction is suppressed in the fiber. Accordingly, the curing conditions for obtaining the fiber-reinforced plastic from the reinforcing-fiber-containing epoxy resin composition or prepreg were heating at 160° C. for 4 hours.
• the bending strength of the polymer obtained by polymerizing the epoxy resin composition of the present invention in a state that does not contain fillers or additives such as reinforcing fibers is 70 MPa or more. If the flexural strength of the polymer is below the lower limit of the range, the fiber-reinforced plastic cannot exhibit sufficient mechanical strength. The higher the strength, the better the mechanical strength of the fiber-reinforced plastic, so there is no need to specify the upper limit.
• the epoxy equivalent of the polymer obtained by polymerizing the epoxy resin composition of the present invention is 5000 g/eq. 20000 g/eq. It is below. If the epoxy equivalent of the polymer is less than the lower limit of the range, the polymer may contain a large amount of epoxy resin that has not undergone polymerization sufficiently, resulting in deterioration of mechanical strength. If the epoxy equivalent of the polymer exceeds the upper limit of the range, the terminal group becomes a phenol group, which may deteriorate the adhesiveness of the reinforcing fiber.
• the epoxy resin composition of the present invention can contain additives.
• additives include fillers such as fumed silica, flame retardants such as aluminum hydroxide and red phosphorus, modifiers such as core-shell rubber, and the like. From the viewpoint of stabilizing the polymerization reaction, it is desirable to add an additive different from the resin phase, but a plasticizer and a compatible flame retardant may be included as long as they do not affect the reaction.
• the epoxy resin composition of the present invention can be made into a thermoplastic epoxy resin by polymerizing it.
• This thermoplastic epoxy resin is excellent as a resin component for fiber-reinforced plastics.
• the reinforcing fiber-containing epoxy resin composition of the present invention is obtained by mixing or impregnating the above epoxy resin composition and reinforcing fibers. Also, the prepreg can be obtained as follows.
• An epoxy resin composition film can be obtained by applying the epoxy resin composition of the present invention to a release-treated paper or plastic film, and optionally providing a release-treated cover film.
• the release paper, release plastic film, and cover film known ones can be used, and they are not particularly limited.
• the thickness of the epoxy resin composition film is determined by the design thickness of the prepreg and the resin ratio, but the normal thickness is 1 ⁇ m or more and 300 ⁇ m or less. When the thickness is less than 1 ⁇ m, there is a problem that the opening of the fibers becomes conspicuous unless the reinforcing fibers are defibrated cleanly. It is preferably 5 ⁇ m or more and 150 ⁇ m or less, more preferably 10 ⁇ m or more and 100 ⁇ m or less.
• the reinforcing fibers used in the present invention are for reinforcing plastics such as carbon fibers, aramid fibers, and cellulose fibers, and are not particularly limited.
• the form of the fibers is not particularly limited and includes UD sheets, woven fabrics, tows, chopped fibers, non-woven fabrics, papermaking, and the like.
• the thickness of each fiber bundle is 1 mm or less, preferably 0.5 mm or less, more preferably 0.2 mm or less.
• the reinforcing fiber-containing epoxy resin composition or prepreg of the present invention is obtained from the above epoxy resin composition and/or epoxy resin composition film and reinforcing fibers.
• the weight ratio of the reinforcing fiber to the epoxy resin composition is preferably 5:5 to 8:2. If the ratio of the reinforcing fibers is too small, the strength required of the fiber-reinforced material may not be sufficiently satisfied, and if the reinforcing fibers are too large, defects such as voids may occur.
• Parts means parts by weight and “%” means % by weight unless otherwise specified.
• the raw materials, catalysts, solvents, and reinforcing fibers used in the examples are as follows.
• epoxy resin Tetramethylbiphenol type epoxy resin (Mitsubishi Chemical Corporation, YX-4000, epoxy equivalent 188)
• A2 Bisphenol A type epoxy resin (manufactured by Nippon Steel Chemical & Materials Co., Ltd., YD-8125, epoxy equivalent 173)
• [Phenolic compound] B1 Bisphenol A (manufactured by Nippon Steel Chemical & Materials Co., Ltd., hydroxyl equivalent 114)
• B2 4,4'-bis(3,3,5-trimethylcyclohexylidene) bisphenol (manufactured by Honshu Chemical Industry Co., Ltd., BisP-HTG, hydroxyl equivalent 155)
• Epoxy equivalent weight Measurement was performed in accordance with the Japanese Industrial Standards JIS K7236, and the unit was expressed as "g/eq.”. Polymers were measured as they were, and reinforcing fiber plastics were measured using the obtained resin components after extracting the resin components according to the following procedure. About 4 g of the sample was weighed into a 110 mL vial bottle, 100 mL of tetrahydrofuran (THF) was added, ultrasonic diffusion was performed at room temperature for 1 hour, and the mixture was allowed to stand at room temperature for 23 hours or more to dissolve. The obtained THF solution was filtered under reduced pressure through a 5 ⁇ m filter paper, and the filtrate was recovered. The collected filtrate was dried in a silicone vat at 20° C. for 24 hours or more, and then dried in an oven set at 110° C. for 5 hours or more to obtain a film-formed resin component.
• THF tetrahydrofuran
• Hydroxyl equivalent The measurement was performed according to the JIS K0070 standard, and the unit was expressed as "g/eq.”.
• the hydroxyl group equivalent of the phenolic resin means the phenolic hydroxyl group equivalent.
• the epoxy resin composition is placed in a colorless and transparent glass Petri dish so as to have a thickness of 2 mm, and the haze value is determined as "less than 5% ( ⁇ 5)” or “less than 10%” with reference to a haze standard plate manufactured by Murakami Color Research Laboratory. ( ⁇ 10)", “less than 20% ( ⁇ 20)”, “less than 30% ( ⁇ 30)", and "30% or more (30 ⁇ )”. If the noise value was less than 30%, it was judged that the phenolic compound was uniformly dissolved in the epoxy resin, and was judged to be ⁇ .
• the vial was dried in an oven at 100° C. for 4 hours or more.
• the dry weight of the wire mesh was subtracted from the weight of the dried sample and the wire mesh, and this was divided by the weight of the sample to determine the gel fraction in weight % and evaluated.
• the gel fraction is equal to the weight percent of THF insolubles.
• the bending strength of the polymer was measured according to JIS K7171.
• a test machine Autograph AGS-X manufactured by Shimadzu Science
• the sample had a thickness of 4 mm, a length of 100 mm, a width of 15 mm, a bending span of 70 mm, and a test speed of 1 mm/min.
• the 90-degree bending strength of the unidirectionally reinforced fiber plastic was measured according to JIS K7074.
• a test machine (Autograph AGS-X manufactured by Shimadzu Science) was used, and the sample had a thickness of 2 mm, a length of 100 mm, a width of 15 mm, a bending span of 70 mm, and a test speed of 1 mm/min. .
• Resin adhesion amount Using an SEM (JSM-7900F, manufactured by JEOL Ltd.), the cross section of the fiber-reinforced plastic after the bending test was observed to confirm the amount of resin adhered to the fiber. If the adhesion between the fiber and the resin is good, it can be confirmed that the resin is well adhered to the fiber surface of the fractured surface. 10 fibers were observed by SEM, and the number of fibers with resin adhering to 80% or more of the fiber surface was evaluated. 9 or more: ⁇ , 8 or less: ⁇
• Example 1 2913 parts of A1, 1000 parts of B1 and 1000 parts of B2 were weighed and pulverized and mixed using a Henschel mixer. Subsequently, melt-mixing is performed using an S1KRC kneader (manufactured by Kurimoto, Ltd.) preheated to a barrel temperature of 170° C., the entire amount is collected in a metal can, and cooled while stirring to obtain a precursor of the epoxy resin composition. A mixture (F1) was obtained.
• S1KRC kneader manufactured by Kurimoto, Ltd.
• the resulting epoxy resin composition (G1) was heated to about 70°C with stirring, poured into an iron chromium-plated mold container with a clearance set to 4 mm in advance, and thermally polymerized at 160°C for 60 minutes in a hot air circulating oven. was performed to obtain a polymer.
• the epoxy equivalent of the obtained polymer As a result of measuring the epoxy equivalent of the obtained polymer, it was 9900 g/eq. Met. The flexural strength of the obtained polymer was measured and found to be 87 MPa. When the gel fraction of the obtained polymer was measured, it was 1%.
• Examples 2-3, Comparative Examples 1-4 An epoxy resin composition and a polymer were obtained in the same manner as in Example 1 under the conditions shown in Table 1. The epoxy equivalent, bending strength and gel fraction of the obtained polymer were measured in the same manner as in Example 1, and the evaluation results are shown in Table 1.
• Comparative Examples 3 and 4 stirring and mixing were performed in a planetary mixer set at 60° C. instead of pulverizing and mixing using a Henschel mixer.
• the barrel temperature during melt mixing was set at 80°C.
• the obtained epoxy resin composition had a haze value of 30% or more, and the molten state of the phenolic compound was judged to be x.
• the weight gel fraction was 95%, and the epoxy equivalent was not measured because the polymer could not be dissolved in the solvent.
• Example 4 A release paper that has been subjected to a release treatment is fixed on a hot plate preheated to 70° C. so that the release surface faces upward, and the epoxy resin composition (G1) obtained in Example 1 is applied onto the release paper. After mounting, a bar coater preheated to 70° C. was used to coat the resin so that the area weight of the resin was 79 g/m 2 . Immediately after coating, the sheet was removed from the hot plate and air-cooled to obtain an epoxy resin composition sheet. Subsequently, the carbon fibers (E) are laminated on the obtained epoxy resin composition sheet so that the area weight of the fibers is 153 g / m 2 , and the surface pressure is 0 using a hot press preheated to 90 ° C.
• the vacuum press conditions are 160° C., 0.1 MPa, and 240 minutes.
• the 90-degree bending strength of the obtained unidirectionally reinforced fiber plastic was measured and found to be 86 MPa.
• the epoxy equivalent of the resin component of the obtained unidirectionally reinforced fiber plastic it was found to be 9800 g/eq. Met.
• the epoxy equivalent of the polymer is 5000 g/eq. 20000 g/eq. It can be confirmed that the 90-degree bending strength of the reinforced fiber plastic becomes 80 MPa or more when the resin strength is 70 MPa or more. From Comparative Example 5 (Comparative Example 1), it can be confirmed that when the epoxy equivalent of the polymer is high, the fiber-resin adhesion is weak, and the 90° bending strength is not sufficiently exhibited. From Comparative Examples 6 and 7 (Comparative Examples 2 and 3), it can be confirmed that unless the resin strength of the polymer is sufficiently strong, the 90-degree bending strength is not sufficiently exhibited.
• Comparative Example 4 Comparative Example 4
• a resin containing a large amount of gel component tends to have a high minimum melt viscosity during the polymerization reaction, and voids tend to remain in the CFRP molding, which is considered to have an adverse effect on the 90-degree bending strength.

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