Precursor mixture of in situ polymerization type thermoplastic epoxy resin, epoxy resin composition, epoxy resin composition sheet, prepreg, and in situ polymerization type thermoplastic fiber reinforced plastic using the same

Abstract

The present invention relates to an in situ polymerization type thermoplastic epoxy resin, and provides an in situ polymerization type thermoplastic epoxy resin or thermoplastic fiber-reinforced plastic, which has excellent heat resistance, while being suppressed in the formation of a gel fraction.　A precursor mixture which is obtained by addition polymerization of an epoxy resin and a bifunctional phenolic compound, and which is used for an in situ polymerization type thermoplastic epoxy resin. This precursor mixture is characterized in that: an epoxy resin that contains 50% by weight or more of a bifunctional epoxy resin (a) represented by formula (1), and a bifunctional phenolic compound are contained as essential components; from 0.9 to 1.1 moles of the bifunctional phenolic compound is contained relative to 1 mole of the epoxy resin; and the viscosity at 60°C is from 1 Pa·s to 50 Pa·s. In formula (1), A is represented by formula (2); n is the number of repeating units, and the average value thereof is within the range of from 0 to 5; and X represents a single bond, an alkylene group having from 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S- or -SO2-; each Y1 independently represents an alkyl group having from 1 to 4 carbon atoms or an aryl group having from 6 to 10 carbon atoms; each of Y2 and Y3 independently represents a hydrogen atom, an alkyl group having from 1 to 4 carbon atoms, or an aryl group having from 6 to 10 carbon atoms.

Description

[Technical field]

[0001] The present invention relates to an in-situ polymerization type thermoplastic epoxy resin and a thermoplastic fiber reinforced plastic. Here, the in-situ polymerization type thermoplastic resin refers to a resin that has a low molecular weight when shipped from a factory, but can be quickly polymerized by hot melt (heat melting) after impregnating reinforcing fibers at the fiber reinforced thermoplastic plastic (FRTP) manufacturing site to be converted into a high molecular weight thermoplastic resin. [Background technology]

[0002] Thermoplastic resins are materials that become plastic when heated and can be easily molded. However, thermoplastic resins generally have high molecular weights and high melt viscosity, so high temperatures and high pressures are required to mold them. It is not easy to compound them in narrow spaces or with materials that are difficult to heat or pressurize.

[0003] In response to this problem, Patent Document 1 proposes a method for producing an in-situ polymerization type thermoplastic epoxy resin using a bifunctional epoxy resin and a bifunctional curing agent. Both the bifunctional epoxy resin and the bifunctional curing agent are monomers or oligomers, and have a lower viscosity than general thermoplastic resins. In addition, they can be dissolved in organic solvents with low boiling points, so they can be reliably impregnated and can be easily dried. By in-situ polymerization, it is possible to obtain a thermoplastic resin with voids reduced to a sufficient level.

[0004] In addition, Non-Patent Document 1 discloses that the glass transition temperature (Tg) of a polymerized in-situ polymerized thermoplastic epoxy resin can be controlled by changing the backbone structure of the main chain depending on the type of epoxy resin or phenol compound. However, no further consideration is given to materials with a changed backbone structure. According to the investigations of the present inventors, when an attempt is made to sufficiently polymerize a skeleton having excellent heat resistance in order to develop mechanical strength, gelation occurs and thermoplasticity cannot be developed, and it is therefore impossible to achieve both.

[0005] Patent Document 2 describes the use of a specific catalyst as a method for obtaining a high molecular weight epoxy resin with excellent storage stability, and the storage stability disclosed in the examples is that of a high molecular weight epoxy resin polymerized with stirring using an organic solvent and an isophorone diisocyanate adduct used as a curing agent. However, the characteristics of the high molecular weight epoxy resin itself are not described except for the epoxy equivalent.

[0006] Patent Document 3 discloses a method for producing a crystalline adduct of bisphenol A and bisphenol TMC, in which the melting point is lowered by heating and cooling a mixture of the two. This crystalline bisphenol adduct is disclosed only in terms of its melting point, and there is no mention of its application to epoxy resins, particularly in-situ polymerized thermoplastic epoxy resins. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication WO2004 / 060981 [Patent Document 2] JP 2015-157907 A [Patent Document 3] Japanese Patent Application Publication No. 9-059196 [Non-patent literature]

[0008] [Non-Patent Document 1] Review of Epoxy Resins: Recent Advances I, p422-p430 (Epoxy Resin Technology Association) Summary of the Invention

[0009] An object of the present invention is to provide an in situ polymerization type thermoplastic epoxy resin which is excellent in heat resistance and produces little gel content, a thermoplastic fiber reinforced plastic, an epoxy resin composition from which they can be obtained, and a precursor mixture thereof. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, it was found that when an epoxy resin having a substituent such as an alkyl group at the ortho position to the glycidoxy group (glycidyloxy group) of the epoxy resin used is used, the polymer has excellent heat resistance, the molecular weight increases without gelation, and a high molecular weight epoxy resin with thermoplasticity can be obtained. This polymerization reaction proceeds in the same way when carbon fiber is impregnated, so it can be provided as a thermoplastic fiber-reinforced plastic.

[0011] That is, the present invention relates to a precursor mixture for use in an in-situ polymerized thermoplastic epoxy resin obtained by addition polymerization of an epoxy resin (A) and a bifunctional phenol compound (B), The precursor mixture comprises, as essential components, an epoxy resin (A) containing 50% by weight or more of a bifunctional epoxy resin (a) represented by the following formula (1) and a bifunctional phenol compound (B), the amount of the bifunctional phenol compound (B) being 0.9 to 1.1 mol per mol of the epoxy resin (A), and the viscosity at 60°C being 1 Pa s or more and 50 Pa s or less. [ka] In the formula (1), A is the formula (2), n is the number of repetitions, the average value of which is 0 to 5, X is a single bond, an alkylene group having 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S-, or -SO2-, and Y 1 is independently an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms; Y 2 and Y 3 each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0012] When the precursor mixture is made to a thickness of 2 mm, the haze value in the thickness direction is preferably less than 30%, and the precursor mixture preferably has a weight average molecular weight of 300 or more and 500 or less according to a standard polystyrene calibration curve.

[0013] The bifunctional phenol compound (B) is preferably a bisphenol compound and / or a biphenol compound, and the proportion of the most abundant component in the bifunctional phenol compound (B) is preferably 90% by weight or less.

[0014] The present invention also provides an epoxy resin composition comprising the precursor mixture and a polymerization catalyst, the precursor mixture being compatible with each other.

[0015] The epoxy resin composition preferably has a haze value of less than 30% in the thickness direction when made to a thickness of 2 mm, and a viscosity at 60° C. of 3 Pa·s or more and 150 Pa·s or less.

[0016] The present invention also provides an epoxy resin composition sheet comprising the above epoxy resin composition having a thickness of 10 μm or more and 300 μm or less.

[0017] The present invention also relates to an in situ polymerization type thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition, or a sheet-like in situ polymerization type thermoplastic epoxy resin obtained by polymerizing a sheet of the epoxy resin composition. The in situ polymerization type thermoplastic epoxy resin and the sheet-like in situ polymerization type thermoplastic epoxy resin preferably have a gel fraction of 0% by weight or more and 10% by weight or less.

[0018] The present invention also relates to a prepreg obtained from the epoxy resin composition and / or the epoxy resin composition sheet and reinforcing fibers, and to an in-situ polymerization type thermoplastic fiber reinforced plastic obtained by polymerizing the prepreg.

[0019] The precursor mixture for in situ polymerization type thermoplastic epoxy resin of the present invention can provide an epoxy resin composition or prepreg that is free from crystal precipitation and has excellent handleability in the hot melt system. Also, it can provide an in situ polymerization type thermoplastic epoxy resin that can increase the glass transition temperature in a polymer having a sufficiently high molecular weight while reducing the generation of gel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described in detail below based on preferred embodiments thereof. The in situ polymerization type thermoplastic epoxy resin is obtained by addition polymerization of an epoxy resin (A) and a bifunctional phenol compound (B), and the precursor mixture (sometimes called a precursor) used for the in situ polymerization type thermoplastic epoxy resin of the present invention contains, as the epoxy resin (A), a bifunctional epoxy resin (a) represented by formula (1) as an essential component in an amount of 50% by weight or more, preferably 66% by weight or more, more preferably 75% by weight or more, and even more preferably 80% by weight or more. The epoxy equivalent of the epoxy resin (A) is preferably 150 to 350 g / eq.

[0021] In formula (1), A is formula (2). n is the number of repetitions and its average value is 0 to 5, and preferably 0 to 1.

[0022] In formula (2), X is any one of a single bond, an alkylene group having 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S-, and -SO2-. Examples of the alkylene group having 1 to 9 carbon atoms include, for example, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -CHPh-, -C(CH3)Ph-, 1,1-cyclopropylene group, 1,1-cyclobutylene group, 1,1-cyclopentylene group, 1,1-cyclohexylene group, 4-methyl-1,1-cyclohexylene group, 3,3,5-trimethyl-1,1-cyclohexylene group, 1,1-cyclooctylene group, 1, Examples include 1-cyclononylene group, 1,2-ethylene group, 1,2-cyclopropylene group, 1,2-cyclobutylene group, 1,2-cyclopentylene group, 1,2-cyclohexylene group, 1,2-phenylene group, 1,3-propylene group, 1,3-cyclobutylene group, 1,3-cyclopentylene group, 1,3-cyclohexylene group, 1,3-phenylene group, 1,4-butylene group, 1,4-cyclohexylene group, 1,4-phenylene group, etc. Ph represents a phenyl group. Among these, a single bond, -O-, -CO-, -COO-, -S-, -SO2-, -CH2-, -CH(CH3)-, -C(CH3)2-, -CHPh-, -C(CH3)Ph-, 1,1-cyclohexylene group, 4-methyl-1,1-cyclohexylene group, 3,3,5-trimethyl-1,1-cyclohexylene group, 1,4-cyclohexylene group, and 1,4-phenylene group are preferred, and a single bond, -O-, -CO-, -COO-, -S-, -SO2-, -CH2-, -CH(CH3)-, -C(CH3)2-, -C(CH3)Ph-, 1,1-cyclohexylene group, and 3,3,5-trimethyl-1,1-cyclohexylene group are more preferred. Here, Ph represents a phenyl group.

[0023] Y in Equation (2) 1 are independently either an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, and a t-butyl group. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, an ethylphenyl group, a xylyl group, an n-propylphenyl group, an isopropylphenyl group, a mesityl group, and a naphthyl group. Of these, methyl, ethyl, n-propyl, n-butyl, t-butyl, phenyl, tolyl, xylyl, and naphthyl groups are preferred, and methyl, ethyl, n-propyl, n-butyl, t-butyl, phenyl, and tolyl groups are more preferred. Y in Equation (2) 2 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, and a substituent other than a hydrogen atom is preferable. 1 The preferred substituents are the same as those exemplified in the above. 2 is Y 1 is the same as: Y in Equation (2) 3 are independently any one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an aryl group having 6 to 10 carbon atoms.1 The preferred substituents are the same as those exemplified in the above. 3 is a hydrogen atom or Y 1 is the same as:

[0024] Examples of the bifunctional epoxy resin (a) include tetramethylbisphenol F type epoxy resins (e.g., YSLV-80XY (manufactured by Nippon Steel Chemical & Material Co., Ltd.)), tetramethylbiphenol type epoxy resins (e.g., YX-4000 (manufactured by Mitsubishi Chemical Corporation)), and biscresolfluorene type epoxy resins (e.g., OGSOL CG-500 (manufactured by Osaka Gas Chemicals Co., Ltd.)).

[0025] In addition, epoxy resins other than the bifunctional epoxy resin (a) can be used in combination as long as they are bifunctional epoxy resins, and the purity is preferably 95% or more. If the purity as a bifunctional compound is high, positional isomers and oligomers may be included. Examples of epoxy resins that can be used in combination include bisphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, bisphenol acetophenone type epoxy resins, diphenyl sulfide type epoxy resins, diphenyl ether type epoxy resins, and bisphenol fluorene type epoxy resins, biphenol type epoxy resins, diphenyl dicyclopentadiene type epoxy resins, alkylene glycol type epoxy resins, dihydroxy naphthalene type epoxy resins, and dihydroxy benzene type epoxy resins, but are not limited thereto.

[0026] If monofunctional impurities are contained, the molecular weight after polymerization will not increase, and the mechanical properties of the produced thermoplastic resin may deteriorate. Therefore, it is preferable that the monofunctional impurities are 2% by weight or less relative to the bifunctional epoxy resin. When trifunctional or higher impurities are contained, the impurities tend to form crosslinked structures starting from the impurities, which may lead to increased dispersion of the polymer and gelation, resulting in loss of thermoplasticity. Therefore, it is preferable that the amount of trifunctional or higher impurities is 1% by weight or less relative to the bifunctional epoxy resin. In addition, impurity components that do not have active groups that react with either epoxy resins or phenolic hydroxyl groups and that do not inhibit the polymerization reaction by themselves may cause the molecular weight after polymerization to decrease if their amount is large. Therefore, it is preferable that the amount of such impurity components is 2% by weight or less relative to the bifunctional epoxy resin.

[0027] The other essential component, the bifunctional phenol compound (B), is a compound having two phenolic hydroxyl groups in one molecule, and its purity is preferably 95% by weight or more. If the purity as a bifunctional compound is high, positional isomers may be included. In other words, it is preferable that the impurities and impurity components are as follows. If monofunctional impurities are contained, the molecular weight after polymerization will not increase, and the mechanical properties of the produced thermoplastic resin may deteriorate. Therefore, it is preferable that the monofunctional impurities are 2% by weight or less relative to the bifunctional phenol compound. When trifunctional or higher impurities are contained, the impurities tend to form crosslinked structures as starting points, which may lead to increased dispersion of the polymer and gelation, resulting in loss of thermoplasticity. Therefore, it is preferable that the trifunctional or higher impurities are 1% by weight or less relative to the bifunctional phenol compound. In addition, even if there is an impurity component that does not have an active group that reacts with either the epoxy resin or the phenolic hydroxyl group and does not inhibit the polymerization reaction by itself, if the amount is large, there is a risk that the molecular weight after polymerization will be small. Therefore, the amount of the impurity component is preferably 2% by weight or less relative to the bifunctional phenol compound.

[0028] Examples of the bifunctional phenol compound (B) are shown below, but are not limited to those shown below as long as they are bifunctional. Examples include bisphenols such as bisphenol A, bisphenol F (all manufactured by Nippon Steel Chemical & Material Co., Ltd.), bisphenol fluorene, biscresol fluorene (all manufactured by Osaka Gas Chemical Co., Ltd.), Bis-E, Bis-Z, BisOC-FL, BisP-AP, BisP-CDE, BisP-HTG, BisP-MIBK, BisP-3MZ, S-BOC, Bis25X-F (all manufactured by Honshu Chemical Industry Co., Ltd.), and bisphenol S; benzenediols such as hydroquinone, methylhydroquinone, dibutylhydroquinone, resorcin, methylresorcin, catechol, and methylcatechol; naphthalenediols such as naphthalenediol; and biphenols such as biphenol, dimethylbiphenol, and tetramethylbiphenol. Among these, bisphenol compounds or biphenol compounds are preferred.

[0029] Two or more kinds of the bifunctional phenol compound (B) may be used. When a plurality of bifunctional phenol compounds are used, the ratio of the component having the largest amount is preferably 90% by weight or less, more preferably 80% by weight or less. The melting point of the bifunctional phenol compound (B) is preferably 150° C. or higher.

[0030] The organic solvent is not an essential component in the precursor mixture. It is preferably 10 parts by weight or less relative to 100 parts by weight of the total amount of the epoxy resin (A) and the bifunctional phenol compound (B). It is more preferably 5 parts by weight or less, and is preferably not contained. In addition, when an organic solvent is used, it is preferable that the boiling point of the organic solvent at 1 atmospheric pressure is 200°C or less.

[0031] The melting conditions of the precursor mixture depend on the melting point of the bifunctional phenol compound (B) used, but it is preferable to dissolve it at 200° C. or less. Alternatively, the bifunctional phenol compound (B) may be melted in advance at 300° C. or less, preferably 200° C. or less, and then the epoxy resin (A) may be added thereto, followed by quenching and mixing at 150° C. or less.

[0032] Here, the blending ratio of the epoxy resin (A) and the bifunctional phenol compound (B) is 0.9 to 1.1 mol, preferably 0.95 to 1.05 mol, more preferably 0.96 to 1.04 mol, and even more preferably 0.97 to 1.03 mol, of the bifunctional phenol compound (B) relative to 1 mol of the epoxy resin (A). If the blending ratio of the bifunctional phenol compound (B) is within this range, the molecular weight of the resulting in situ polymerization type thermoplastic epoxy resin is sufficiently extended, which is preferable.

[0033] It is desirable that the molten mixture is completely dissolved, but for example, when the molten mixture is poured into a glass petri dish to a thickness of 2 mm without any bubbles and the haze value in the thickness direction is measured, if the haze value in the thickness direction is less than 30%, it is judged that the mixture has dissolved to a level that does not affect the polymerization reaction. The haze value is more preferably less than 20%, and even more preferably less than 10%.

[0034] The viscosity of the precursor mixture at 60°C is 1 Pa·s or more and 50 Pa·s or less. If the viscosity is less than 1 Pa·s, the thermoplastic epoxy resin precursor mixture and subsequent materials will be too soft, which may result in poor handling at around room temperature. If the viscosity exceeds 50 Pa·s, the workability when mixing the polymerization catalyst in the next step may be poor, and high-temperature processing may be required, which may result in poor storage stability. A more preferable viscosity is 3 Pa·s or more and 40 Pa·s or less, and preferably 5 Pa·s or more and 30 Pa·s or less.

[0035] The weight average molecular weight of the precursor mixture according to a standard polystyrene calibration curve is preferably 300 to 500. A more preferred weight average molecular weight is 300 to 450, and more preferably 300 to 400. By setting the weight average molecular weight within this range, it is easy to set the viscosity of the precursor mixture at 60° C. within the preferred range.

[0036] The epoxy resin composition of the present invention is obtained by mixing the precursor mixture with a polymerization catalyst. Examples of polymerization catalysts that can be used include phosphine compounds, quaternary phosphonium salts, imidazoles, and tertiary amines. Among these, phosphine compounds are particularly preferred, and triphenylphosphine, tris(o-tolyl)phosphine, tris(p-tolyl)phosphine, tris(p-methoxyphenyl)phosphine, and tris(2,6-dimethoxyphenyl)phosphine (all manufactured by Hokko Chemical Industry Co., Ltd.) are particularly preferred. In addition, Hishicolin PX-4MP and Hishicolin PX-4ET (all manufactured by Nippon Chemical Industry Co., Ltd.) are preferred as quaternary phosphonium salts. Furthermore, 2-phenylimidazole and 2,3-dihydro-1H-pyrrolo-[1,2-a]benzimidazole (all manufactured by Shikoku Chemical Industry Co., Ltd.) are preferred as imidazoles. The amount of the polymerization catalyst is 0.05% by weight or more and 10% by weight or less based on the sum of the epoxy resin (A) and the phenol compound (B). More preferably, it is 0.1% by weight or more and 5% by weight or less. If the amount of the catalyst is less than 0.05% by weight, the molecular weight will not increase sufficiently or the polymerization will take a long time, resulting in a loss of productivity. On the other hand, if the amount of the catalyst is more than 10% by weight, not only will the storage stability be impaired, but the molecular weight will not increase sufficiently.

[0037] The epoxy resin composition of the present invention is a mixture containing an epoxy resin, a phenolic compound, and a polymerization catalyst, and can be polymerized by heating. When adding the polymerization catalyst, a small amount of organic solvent may be used for the purpose of uniform mixing. The amount of organic solvent used is 10% by weight or less of the sum of the epoxy resin and the phenolic compound, preferably 5% by weight or less, and more preferably 1% by weight or less. If the organic solvent is used in an amount exceeding 10% by weight, there is a problem that the molecular weight of the polymer does not increase sufficiently.

[0038] The viscosity of the epoxy resin composition at 60°C is preferably 3 Pa·s or more and 150 Pa·s or less. If the viscosity is less than 3 Pa·s, the resin components in the resin sheets and prepregs described below become too soft, which may result in poor handling at around room temperature. If the viscosity exceeds 150 Pa·s, the process of applying the composition to a film and the process of impregnating the reinforcing fibers must be performed at high temperatures, which may affect storage stability. A more preferred viscosity is 10 Pa·s or more and 140 Pa·s or less, and preferably 20 Pa·s or more and 130 Pa·s or less. As with the precursor mixture, the epoxy resin composition also preferably has a haze value in the thickness direction when made to a thickness of 2 mm of less than 30%, more preferably less than 20%, and even more preferably less than 10%.

[0039] An epoxy resin composition sheet is a sheet in which an epoxy resin composition is applied to a base film. If necessary, the sheet can be sandwiched between cover films. The base film is generally made of polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene, paper, etc. The base film may or may not be release-treated, but in the case of paper, release treatment is required. When a cover film is used, a polyethylene film or paper that has been subjected to release treatment is generally used. The coating thickness is 10 μm or more and 300 μm or less, preferably 15 μm or more and 150 μm or less, and more preferably 20 μm or more and 100 μm or less. In the present invention, as described later, this may be attached to an adherend and thermally polymerized, or may be impregnated into reinforcing fibers. The thermal polymerization is usually performed at a temperature in the range of 100°C to 200°C. If the thermal polymerization temperature is less than 100°C, the glass transition temperature of the polymer exceeds this temperature during the polymerization, and the reaction does not proceed sufficiently. If the reaction temperature exceeds 200°C, an undesired side reaction may occur, resulting in gelation. The time required for polymerization is usually 5 minutes to 6 hours. The higher the reaction temperature, the shorter the time, but if the reaction temperature is less than 5 minutes, the polymerization reaction does not proceed sufficiently. If the reaction temperature exceeds 6 hours, productivity will decrease, which is not preferable.

[0040] The thermoplastic epoxy resin is a thermoplastic epoxy resin obtained by polymerizing an epoxy resin composition or an epoxy resin composition sheet. When an epoxy resin composition sheet is used, a sheet-like thermoplastic epoxy resin is obtained. In order to exhibit thermoplasticity, the solvent insoluble matter (gel fraction) must be 0% by weight or more and 10% by weight or less. This solvent insoluble matter (gel fraction) can be measured by the method described in the examples. The molecular weight of the thermoplastic epoxy resin is 5000 or more, preferably 7500 or more, and desirably 10000 or more in number average molecular weight. If the number average molecular weight is less than 5000, the degree of polymerization is not sufficient to obtain mechanical strength, and strength is not obtained. There is no particular upper limit, but generally, if the number average molecular weight exceeds 30000, polymerization does not proceed easily and a number average molecular weight of 50000 or less can be obtained. The weight average molecular weight is preferably 50000 or more and 300000 or less. The dispersion indicated by the polymerization average molecular weight / number average molecular weight is preferably 1 or more and 20 or less, and desirably 2 or more and 15 or less. If the dispersion exceeds 20, gelation tends to occur easily. Also, the dispersion is not less than 1.

[0041] The reinforcing fibers are fibers for reinforcing the thermoplastic epoxy resin, which is the matrix resin, and examples of such fibers include carbon fibers, glass fibers, aramid fibers, etc. Furthermore, there is no limitation on the form of these fibers, and any form such as long fibers, chopped fibers, nonwoven fabrics, cloths, etc. can be used.

[0042] In the present invention, the prepreg (epoxy resin prepreg) is a composite of an epoxy resin composition or an epoxy resin composition sheet and reinforcing fibers. If voids remain during impregnation, they may become defects in the final product and may not be able to achieve the desired strength, so it is desirable to reduce the voids during impregnation. As a means for this, heat treatment can be performed. Heat treatment is generally performed at 50°C or higher and 100°C or lower. If it is less than 50°C, the viscosity of the resin cannot be sufficiently reduced, and impregnation failure may occur. If it exceeds 100°C, there is a risk of polymerization reaction proceeding. The heat treatment time is usually 5 seconds or longer and 3 minutes or shorter. If it is less than 5 seconds, the viscosity may not be sufficiently reduced and impregnation may not proceed depending on the thickness. If it exceeds 3 minutes, the polymerization reaction may proceed slightly, and the desired tackiness may not be obtained. In addition, as a means for further improving the impregnation accuracy, thermocompression bonding using a heated roll or the like can be mentioned. The pressure depends on the substrate, but is 0.1 kgf / cm or higher and 10 kgf / cm or lower. If the line pressure is less than 0.1 kgf / cm, impregnation may be insufficient, and if it exceeds 10 kgf / cm, the reinforcing fibers may be damaged or the resin may flow out. The volume ratio of resin to reinforcing fibers is 30:70 to 80:20. If the resin ratio is less than 30, there is a problem of insufficient resin and many voids. If the resin ratio is more than 80, the amount of reinforcing fibers is small, and sufficient properties cannot be obtained.

[0043] In the present invention, the in-situ polymerization type thermoplastic fiber reinforced plastic is a product obtained by thermally polymerizing an epoxy resin prepreg. Its molecular weight is 5000 or more, preferably 7500 or more, and desirably 10000 or more in number average molecular weight (Mn). If the number average molecular weight is less than 5000, it cannot be said that the degree of polymerization is sufficient to obtain mechanical strength, and strength cannot be obtained. There is no particular upper limit, but generally, if the number average molecular weight exceeds 30000, polymerization does not proceed easily and a product of 50000 or less is obtained. The weight average molecular weight (Mw) is 50000 or more and preferably 300000 or less. The dispersion indicated by the polymerization average molecular weight / number average molecular weight is preferably 1 to 20, and desirably 2 to 15. If the dispersion exceeds 20, it tends to be easily gelled. In addition, the dispersion is not less than 1. EXAMPLES

[0044] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" refers to parts by weight, and "%" refers to % by weight. The raw materials used in the following examples are as follows.

[0045] [Epoxy resin] A1: Tetramethylbisphenol F type epoxy resin (Nippon Steel Chemical & Material Co., Ltd., YSLV-80XY, epoxy equivalent 192g / eq) A2: Tetramethylbiphenol type epoxy resin (Mitsubishi Chemical Corporation, YX4000, epoxy equivalent 188g / eq) A3: Bisphenol A type liquid epoxy resin (Nippon Steel Chemical & Material Co., Ltd., YD-128, epoxy equivalent 188g / eq)

[0046] [Phenol compounds] B1: Bisphenol A (manufactured by Nippon Steel Chemical & Material Co., Ltd.) B2: 4,4'-(3,3,5-trimethylcyclohexylidene)bisphenol (Honshu Chemical Industry Co., Ltd., BisP-HTG) B3: 9,9-bis(4-hydroxy-3-methylphenyl)fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., BCF)

[0047] [Organic solvents] C1: Cyclohexanone (first-grade reagent, Fujifilm Wako Pure Chemical Industries, Ltd.)

[0048] [Polymerization catalyst] E1: 2,3-dihydro-1H-pyrrolo-[1,2-a]benzimidazole (manufactured by Shikoku Chemical Industry Co., Ltd., TBZ) E2: Tris(paratolyl)phosphine (TPTP, manufactured by Hokko Chemical Industry Co., Ltd.) E3: Tris(paramethoxyphenyl)phosphine (TPAP, manufactured by Hokko Chemical Industry Co., Ltd.)

[0049] [Reinforced fiber] I1: PAN-based carbon fiber (Toray Industries, Inc., T700SC-12K-60E)

[0050] Example 1 278.1 parts of A1, 50.0 parts of B1, and 150.0 parts of B2 were weighed out and pulverized and mixed using a Henschel mixer. Then, melt mixing was performed using an S1KRC kneader (manufactured by Kurimoto Iron Works, Ltd.) whose barrel temperature was preheated to 170°C, and the entire amount was collected in a metal can and cooled while stirring to obtain a thermoplastic epoxy resin precursor mixture (D1).

[0051] The obtained precursor mixture (D1) was placed in a colorless, transparent glass petri dish to a thickness of 2 mm, and the haze value in the thickness direction was evaluated using a haze standard plate manufactured by Murakami Color Research Laboratory as a reference on a five-level scale: "less than 5% (<5)," "5% to less than 10% (<10)," "10% to less than 20% (<20)," "20% to less than 30% (<30)," and "30% or more (30≦)." The result was less than 10%.

[0052] The viscosity of the obtained precursor mixture (D1) at 60° C. was measured using CV-1s manufactured by Toa Kogyo Co., Ltd. and was found to be 25 Pa·s.

[0053] The weight average molecular weight (Mw) of the obtained precursor mixture (D1) was 371. The method for measuring Mw is as follows. Analysis was performed using a Tosoh Corporation HLC-8420GPC. The columns were TSKgel G4000HXL, TSKgel G3000HXL, and TSKgel G2000HXL connected in series, and the column oven was set to 40°C. The eluent was tetrahydrofuran, and the detector was an RI detector. The flow rates were 1 mL / min on the sample side and 0.5 mL / min on the reference side. Approximately 0.05 g of sample was weighed out, dissolved in 10 mL of tetrahydrofuran containing 5% cyclohexanone as an external standard substance, and filtered through a 0.45 μm PTFE membrane filter for analysis. Mw was converted using a standard polystyrene calibration curve, and elution time was corrected using cyclohexanone.

[0054] Examples 2 to 6, Comparative Examples 1 to 3 A thermoplastic epoxy resin precursor mixture was obtained under the conditions shown in Table 1 by the same operation as in Example 1. However, in the operations of Example 5 and Comparative Examples 1 to 3, instead of mixing with a Henschel mixer, mixing was performed with a centrifugal stirring device of a rotation-revolution type, and then melt mixing was performed with a kneader. The haze value, viscosity, and Mw of the obtained precursor mixture were measured in the same manner as in Example 1, and the measurement results are shown in Table 1. In Comparative Example 2, although the liquid discharged from the kneader was transparent, crystals were precipitated during stirring in the cooling process, causing the sample to become cloudy. In addition, crystals continued to precipitate even during the viscosity measurement at 60°C, and the viscosity was not stable, so measurement was not possible.

[0055] [Table 1]

[0056] Table 1 is described below. In all of Examples 1 to 6 and Comparative Examples 1 to 3, a precursor mixture was obtained that was uniformly dissolved and was liquid at 60°C and semi-solid to liquid at room temperature. In Comparative Example 2, it is believed that bisphenol A (BPA) recrystallized. Although BPA may have recrystallized in Comparative Example 1, this was not observed in this experiment. Comparative Example 1 had a severe thermal history, which may have deteriorated part of the resin component and inhibited crystallization. It was also shown that mixing two or more types of phenolic compounds can effectively suppress the precipitation of crystals at room temperature.

[0057] Example 7 One part of E1 (polymerization catalyst) was dissolved in one part of C1 (organic solvent) in advance. The precursor mixture (D1) obtained in Example 1 was placed in a planetary mixer set at 60°C, and the polymerization catalyst solution was added and mixed. After mixing, the mixture was quickly removed and immediately cooled to 40°C or less to obtain an epoxy resin composition (F1).

[0058] The viscosity of the obtained epoxy resin composition (F1) at 60°C was measured using an Anton Paar MCR102 and found to be 62 Pa s. The haze value of the epoxy resin composition was 5% or more and less than 10% (<10).

[0059] The obtained epoxy resin composition (F1) was heated to about 70°C and stirred, poured into a chrome-plated iron mold container with a clearance of 4 mm set in advance, and thermally polymerized at 160°C for 4 hours in a hot air circulating oven to obtain a thermoplastic epoxy resin.

[0060] The epoxy equivalent of the obtained thermoplastic epoxy resin was measured in accordance with JIS K 7236 and found to be 18,000 g / eq.

[0061] The glass transition temperature (Tg) of the thermoplastic epoxy resin was 123° C. The method for measuring Tg is as follows. In accordance with JIS K 7121, measurements were performed using a differential scanning calorimeter (Hitachi High-Tech Science Corporation, EXSTAR6000 DSC6200) at a temperature increase rate of 10°C / min, and the temperature was expressed as DSC·Tmg (the midpoint temperature of the deformation curve to the tangent line between the glassy state and the rubbery state).

[0062] The gel fraction of the thermoplastic epoxy resin was 1% by weight or less. The gel fraction was measured by the following method. Approximately 1 g of the sample thermoplastic epoxy resin was weighed out in a 100 mL vial, 50 mL of tetrahydrofuran was added, ultrasonic diffusion was performed at room temperature for 1 hour, and the resin was left to stand at room temperature for more than 23 hours to dissolve. A 500 mesh wire mesh was dried in an oven at 100 °C for 1 hour and its weight was measured. The 500 mesh wire mesh was folded into a funnel shape, and the entire sample solution was poured onto the funnel. The vial was washed with tetrahydrofuran until no insoluble matter of the sample remained, and the solution was poured into the funnel. The insoluble matter on the mesh and the mesh were then washed with tetrahydrofuran and dried in an oven at 100 °C for more than 4 hours. The dry weight of the mesh was subtracted from the weight of the dried sample and mesh, and the result was divided by the weight of the sample to obtain the gel fraction in weight %.

[0063] The number average molecular weight (Mn), weight average molecular weight (Mw), and peak top molecular weight (Mt) of the thermoplastic epoxy resin were 25,000, 62,000, and 35,000, respectively. The molecular weight was measured by the following method. Analysis was performed using a Tosoh Corporation HLC-8320GPC. The columns were a TSKguardcolumnHXL, a TSKgel GMHXL, a TSKgel GMHXL, and a TSKgel G2000HXL connected in series, and the column oven was set to 40°C. The eluent was tetrahydrofuran, and the detector was an RI detector. The flow rates were 1 mL / min on the sample side and 0.5 mL / min on the reference side. Approximately 0.1 g of the thermoplastic epoxy resin sample was weighed out, dissolved in 10 mL of tetrahydrofuran containing 5% cyclohexanone as an external standard substance, and filtered through a 0.45 μm PTFE membrane filter for analysis. The molecular weight was converted using a standard polystyrene calibration curve, and the elution time was corrected using cyclohexanone.

[0064] In addition, in Table 2, the appearance of the test piece is indicated as × if cracks were found at the end of the test piece during the cooling process after polymerization of the thermoplastic epoxy resin, and indicated as ◯ if no change was found.

[0065] Examples 8 to 12, Comparative Examples 4 to 6 An epoxy resin composition and a thermoplastic epoxy resin were obtained in the same manner as in Example 7 under the conditions shown in Table 2. The melt viscosity and haze value of the obtained epoxy resin composition, and the appearance, epoxy equivalent, gel fraction, Tg, Mn, Mw, and Mt of the thermoplastic epoxy resin were measured in the same manner as in Example 7, and the measurement results are shown in Table 2.

[0066] [Table 2]

[0067] Table 2 will be described. In all of Examples 7 to 12, a resin composition with a viscosity suitable for the hot melt process was obtained. Furthermore, gelation was hardly observed in the polymerized product. In Comparative Examples 4 and 5, gel components were clearly generated in the thermoplastic epoxy resin. In Comparative Examples 4 and 5, where the steric hindrance around the glycidyl group is small, thermal degradation components were generated in the heat dissolving process and thermal polymerization process, which may have caused gelation during polymerization, while in Examples 7 to 12, where the steric hindrance around the glycidyl group is large, gelation was unlikely to occur. In Comparative Example 6, it is considered that polymerization did not proceed sufficiently, so gelation did not occur.

[0068] Example 13 A release-treated release paper was fixed on a hot plate preheated to 70° C. with the release side facing up, and the epoxy resin composition (F1) obtained in Example 6 was placed on the release paper, and then coated to a thickness of 50 μm using a bar coater preheated to 70° C. Immediately after coating, the sheet was removed from the hot plate and air-cooled to obtain an epoxy resin composition sheet. Next, carbon fibers (I1) were laminated onto the obtained epoxy resin composition sheet so as to give a strand density of 15 strands per 10 cm, and pressure was applied to the sheet using a hot press preheated to 90°C so that the surface pressure became 0.5 MPa. After 1 minute, the sheet was removed and air-cooled to obtain an epoxy resin prepreg with Rc=33%. Nine of the epoxy resin prepregs were then laminated, sandwiched between release films, and vacuum pressed to obtain a thermoplastic fiber-reinforced plastic of in-situ polymerization type. The vacuum pressing conditions were 160°C, 0.5 MPa, and 4 hours.

[0069] The gelation of the obtained thermoplastic fiber reinforced plastic was judged to be not occurred. The gelation was judged to be not occurred by dissolving the resin content of about 0.1g of the test piece in 10mL of tetrahydrofuran by ultrasonic diffusion, and the test piece in which the carbon fiber bundle was loosened was judged to have no gel and rated as "○", and the test piece in which the carbon fiber bundle was not loosened was judged to have gelated and rated as "×".

[0070] The Mn, Mw and Mt of the thermoplastic fiber reinforced plastic were 23000, 76000 and 33000, respectively. The molecular weight was measured by the method described in Example 7.

[0071] Examples 14 to 18, Comparative Examples 7 to 9 Thermoplastic fiber reinforced plastics were obtained in the same manner as in Example 13, except that the epoxy resin compositions shown in Table 3 were used. The gelation of the obtained thermoplastic fiber reinforced plastics was judged, and Mn, Mw, and Mt were measured in the same manner as in Example 13. The measurement results are shown in Table 3.

[0072] [Table 3]

[0073] Table 3 will now be described. It was confirmed that in all of Examples 13 to 18, the cured products polymerized and the fibers broke apart when dissolved in tetrahydrofuran. On the other hand, Comparative Examples 7 and 8 were hardly dissolved in tetrahydrofuran and the fibers did not break apart. Comparative Example 9 dissolved in tetrahydrofuran, but the degree of polymerization was insufficient, and it cannot be said that it functions adequately as a structural material. [Industrial Applicability]

[0074] The precursor mixture of the present invention can be used for epoxy resin compositions (sheets), and can be particularly suitably used for in-situ polymerization type thermoplastic epoxy resins, prepregs, thermoplastic fiber reinforced plastics, and the like.

Claims

1. A precursor mixture for use in an in-situ polymerized thermoplastic epoxy resin obtained by addition polymerization of an epoxy resin and a bifunctional phenol compound, comprising: A precursor mixture comprising, as essential components, an epoxy resin containing 50% by weight or more of a bifunctional epoxy resin (a) represented by the following formula (1) and a bifunctional phenol compound, the amount of the bifunctional phenol compound being 0.9 to 1.1 moles per mole of the epoxy resin, and having a viscosity at 60°C of 1 Pa s or more and 50 Pa s or less: 【Chemistry 1】 (wherein A in formula (1) is formula (2), n is the number of repetitions and the average value is 0 to 5, and X is a single bond, an alkylene group having 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S-, -SO ２ -, and Y １ is independently an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 10 carbon atoms; 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.

2. 2. The precursor mixture according to claim 1, which has a haze value of less than 30% in the thickness direction when made into a thickness of 2 mm.

3. 3. The precursor mixture according to claim 1, having a weight average molecular weight of 300 or more and 500 or less, as determined by a standard polystyrene calibration curve.

4. The precursor mixture according to any one of claims 1 to 3, wherein the bifunctional phenol compound is a bisphenol compound and / or a biphenol compound.

5. The precursor mixture according to any one of claims 1 to 4, wherein the proportion of the most abundant component in the bifunctional phenol compound is 90% by weight or less.

6. 6. An epoxy resin composition comprising the precursor mixture according to claim 1 and a polymerization catalyst, the precursor mixture being compatible with the precursor mixture.

7. 7. The epoxy resin composition according to claim 6, which has a haze value in the thickness direction when made into a thickness of 2 mm of less than 30%.

8. 8. The epoxy resin composition according to claim 6, having a viscosity at 60° C. of 3 Pa·s or more and 150 Pa·s or less.

9. An in-situ polymerization type thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition according to any one of claims 6 to 8.

10. 10. The in situ polymerization type thermoplastic epoxy resin according to claim 9, characterized in that the gel fraction is 0% by weight or more and 10% by weight or less.

11. An epoxy resin composition sheet comprising the epoxy resin composition according to any one of claims 6 to 8 and having a thickness of 10 µm to 300 µm.

12. A sheet-shaped in-situ polymerization type thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition sheet according to claim 11.

13. 13. The sheet-shaped in-situ polymerization type thermoplastic epoxy resin according to claim 12, characterized in that the gel fraction is 0% by weight or more and 10% by weight or less.

14. A prepreg obtained from the epoxy resin composition according to any one of claims 6 to 8 and / or the epoxy resin composition sheet according to claim 11, and reinforcing fibers.

15. An in-situ polymerized thermoplastic fiber reinforced plastic obtained by polymerizing the prepreg according to claim 14.

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