WO2022070846A1 - 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 same - Google Patents

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

Field-polymerized thermoplastic epoxy resin precursor mixture, epoxy resin composition, epoxy resin composition sheet, prepreg, and field-polymerized thermoplastic fiber reinforced plastic using these.

The present invention relates to a field-polymerized thermoplastic epoxy resin and a thermoplastic fiber reinforced plastic. Here, the on-site polymerization type thermoplastic resin has a low molecular weight at the time of shipment from the factory, but after being impregnated with the reinforced fiber at the fiber reinforced thermoplastic (FRTP) manufacturing site, it is rapidly polymerized by hot melt (heat melting). This refers to a resin that can be converted into a high-molecular-weight thermoplastic resin.

Thermoplastic resin is a material that has plasticity when heated and can be easily molded. However, since thermoplastic resins generally have a high molecular weight and a high melt viscosity, high temperature and high pressure are required for molding. It is not easy to combine with a narrow space or a material that is difficult to heat or pressurize.

To solve this problem, Patent Document 1 proposes a method for producing a field-polymerized 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 lower viscosities than general thermoplastic resins. Further, since it can be dissolved even with an organic solvent having a low boiling point, it can be reliably impregnated and can be easily dried. By in-situ polymerization, a thermoplastic resin with voids reduced to a sufficient level can be obtained.

Further, Non-Patent Document 1 discloses that the glass transition temperature (Tg) of a polymer is controlled by changing the skeleton of the main chain depending on the type of the epoxy resin or the phenol compound in the field-polymerized thermoplastic epoxy resin. However, no further studies have been made here on materials with altered backbone skeletons.
According to the studies by the present inventors, if an attempt is made to sufficiently polymerize a skeleton having excellent heat resistance in order to develop mechanical strength, it gels and cannot exhibit thermoplasticity, and this cannot be achieved at the same time. rice field.

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

Further, Patent Document 3 discloses a method for producing a crystalline adduct having a lower melting point by heating and cooling a mixture of bisphenol A and bisphenol TMC. This bisphenol crystalline adduct is only disclosed with respect to its melting point, and there is no description regarding its application to epoxy resins, especially field-polymerized thermoplastic epoxy resins.

International release WO2004 / 060981 JP-A-2015-157907 Japanese Unexamined Patent Publication No. 9-059196

The present invention relates to a field-polymerized thermoplastic epoxy resin, which has excellent heat resistance and produces little gel, a field-polymerized thermoplastic epoxy resin, a thermoplastic fiber-reinforced plastic, an epoxy resin composition obtained thereof, and a precursor thereof. The subject is to provide a body mixture.

As a result of diligent studies to solve the above problems, when a epoxy resin having a substituent such as an alkyl group at the ortho position is used with respect to the glycidoxy group (glycidyloxy group), the polymer is heat resistant. It has been found that a high-molecular-weight epoxy resin having excellent properties, increasing the molecular weight without gelation, and having thermoplasticity can be obtained. Since this polymerization reaction proceeds in the same manner even when the carbon fiber is impregnated, it can be provided as a thermoplastic fiber reinforced plastic.

That is, the present invention is a precursor mixture used for a field-polymerized thermoplastic epoxy resin obtained by addition polymerization of an epoxy resin (A) and a bifunctional phenol compound (B).
The epoxy resin (A) containing 50% by weight or more of the bifunctional epoxy resin (a) represented by the following formula (1) and the bifunctional phenol compound (B) are contained as essential components in 1 mol of the epoxy resin (A). On the other hand, the bifunctional phenol compound (B) is 0.9 to 1.1 mol, and is a precursor mixture characterized by having a viscosity at 60 ° C. of 1 Pa · s or more and 50 Pa · s or less.

Here, A in the formula (1) is the formula (2), n is the number of repetitions, and the average value thereof is 0 to 5. X is a single bond, an alkylene group having 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S-, or -SO _2- , and Y ¹ is independently 1 to 9 carbon atoms. It is either an alkyl group of 4 or an aryl group having 6 to 10 carbon atoms, and Y ² and Y ³ are independently of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an aryl group having 6 to 10 carbon atoms. Either.

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

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

Further, the present invention is an epoxy resin composition in which a polymerization catalyst is blended with the precursor mixture and the mixture is compatible with each other.

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

Further, the present invention is an epoxy resin composition sheet in which the epoxy resin composition has a thickness of 10 μm or more and 300 μm or less.

Further, the present invention is a field-polymerized thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition, or a sheet-shaped field-polymerized thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition sheet. .. These field-polymerized thermoplastic epoxy resins and sheet-shaped field-polymerized thermoplastic epoxy resins preferably have a gel fraction of 0% by weight or more and 10% by weight or less.

The present invention is a prepreg obtained from the epoxy resin composition and / or the epoxy resin composition sheet and the reinforcing fiber, and is a field-polymerized thermoplastic fiber reinforced plastic obtained by polymerizing the prepreg. ..

The precursor mixture for the field-polymerized thermoplastic epoxy resin of the present invention does not precipitate crystals, and an epoxy resin composition or prepreg having excellent handleability can be obtained by a hot melt method. In addition, it is possible to obtain a field-polymerized thermoplastic epoxy resin capable of reducing gel formation while increasing the glass transition temperature in a polymer having a sufficiently high molecular weight.

Hereinafter, the present invention will be described in detail according to the preferred embodiment thereof.
The field-polymerized thermoplastic epoxy resin is obtained by addition polymerization of the epoxy resin (A) and the bifunctional phenol compound (B), and is a precursor mixture (with a precursor) used in the field-polymerized thermoplastic epoxy resin of the present invention. (May be referred to as) contains, as the epoxy resin (A), the bifunctional epoxy resin (a) represented by the formula (1) as an essential component in an amount of 50% by weight or more. It is preferably 66% by weight or more, more preferably 75% by weight or more, and further preferably 80% by weight or more.
The epoxy equivalent of the epoxy resin (A) is preferably 150 to 350 g / eq.

In equation (1), A is equation (2). n is the number of repetitions, and the average value thereof is 0 to 5, preferably 0 to 1.

In the formula (2), X is any one of a single bond, an alkylene group having 1 to 9 carbon atoms, -O-, -CO-, -COO-, -S-, and -SO _2- .
Examples of the alkylene group having 1 to 9 carbon atoms include -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -CHPh-, and -C. (CH ₃ ) 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, 1,1-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 and the like can be mentioned. In addition, Ph represents a phenyl group.
Of these, single bond, -O-, -CO-, -COO-, -S-, -SO _2- , -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- , -CHPh-, -C (CH ₃ ) Ph-, 1,1-cyclohexylene group, 4-methyl-1,1-cyclohexylene group, 3,3,5-trimethyl-1,1-cyclohexylene group, 1 , 4-Cyclohexylene group, 1,4-phenylene group are preferable, single bond, -O-, -CO-, -COO-, -S-, -SO _2- , -CH _2- , -CH (CH ₃ ). )-, -C (CH ₃ ) _2- , -C (CH ₃ ) Ph-, 1,1-cyclohexylene group, 3,3,5-trimethyl-1,1-cyclohexylene group are more preferable. In addition, Ph represents a phenyl group.

Y ¹ in the formula (2) is independently one of an alkyl group having 1 to 4 carbon atoms and 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. Can be mentioned.
Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, an ethylphenyl group, a xsilyl group, an n-propylphenyl group, an isopropylphenyl group, a mesityl group and a naphthyl group.
Of these, methyl group, ethyl group, n-propyl group, n-butyl group, t-butyl group, phenyl group, tolyl group, xylyl group and naphthyl group are preferable, and methyl group, ethyl group and n-propyl group are preferable. More preferably, n-butyl group, t-butyl group, phenyl group and tolyl group.
Y ² in the formula (2) is 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, and a substituent other than the hydrogen atom is preferable. ^The substituent is the same as the substituent exemplified in Y1. Preferred Y ² is similar to Y ¹ .
Y3 in the formula ( ² ) is independently one of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an aryl group having 6 to 10 carbon atoms. ^The substituent is the same as the substituent exemplified in Y1. Preferred Y ³ is similar to a hydrogen atom or Y ¹ .

Examples of the bifunctional epoxy resin (a) include a tetramethylbisphenol F type epoxy resin (for example, YSLV-80XY (manufactured by Nittetsu Chemical & Materials Co., Ltd.)) and a tetramethylbiphenol type epoxy resin (for example, YX-4000). (Made by Mitsubishi Chemical Co., Ltd.), etc.), biscresol fluorene type epoxy resin (for example, OGSOL CG-500 (manufactured by Osaka Gas Chemical Co., Ltd.), etc.) and the like.

Further, an epoxy resin other than the bifunctional epoxy resin (a) can be used in combination as long as it is a bifunctional epoxy resin, and its purity is preferably 95% or more. Then, as long as the purity as a bifunctional compound is high, positional isomers and oligomers may be contained. Examples of the epoxy resin that can be used together include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol acetophenone type epoxy resin, diphenyl sulfide type epoxy resin, diphenyl ether type epoxy resin, bisphenol fluorene type epoxy resin, and the like. Examples thereof include, but are not limited to, bisphenol type epoxy resin, biphenol type epoxy resin, diphenyldicyclopentadiene type epoxy resin, alkylene glycol type epoxy resin, dihydroxynaphthalene type epoxy resin, and dihydroxybenzene type epoxy resin.

When monofunctional impurities are contained, the molecular weight after polymerization does not increase, so that the mechanical properties of the produced thermoplastic resin may deteriorate. Therefore, the monofunctional impurities are preferably 2% by weight or less with respect to the bifunctional epoxy resin.
When impurities having trifunctionality or higher are contained, it becomes easy to form a crosslinked structure starting from the impurities, so that the dispersion of the polymer becomes large and there is a possibility that gelation may occur and the thermoplasticity may be impaired. Therefore, the amount of trifunctional or higher impurities is preferably 1% by weight or less with respect to the bifunctional epoxy resin.
It should be noted that even for an impurity component that does not have an active group that reacts with either an epoxy resin or a phenolic hydroxyl group and that does not inhibit the polymerization reaction by itself, the molecular weight after polymerization may decrease as the amount increases. Therefore, it is preferably 2% by weight or less with respect to the bifunctional epoxy resin.

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. Then, as long as the purity as a bifunctional compound is high, the positional isomer may be contained. That is, it is preferable that impurities and impurity components are as follows.
When monofunctional impurities are contained, the molecular weight after polymerization does not increase, so that the mechanical properties of the produced thermoplastic resin may deteriorate. Therefore, the monofunctional impurities are preferably 2% by weight or less with respect to the bifunctional phenol compound.
When impurities having trifunctionality or higher are contained, it becomes easy to form a crosslinked structure starting from the impurities, so that the dispersion of the polymer becomes large and there is a possibility that gelation may occur and the thermoplasticity may be impaired. Therefore, the amount of trifunctional or higher impurities is preferably 1% by weight or less with respect to the bifunctional phenol compound.
It should be noted that even for an impurity component that does not have an active group that reacts with either an epoxy resin or a phenolic hydroxyl group and that does not inhibit the polymerization reaction by itself, the molecular weight after polymerization may decrease as the amount increases. Therefore, the impurity component is preferably 2% by weight or less with respect to the bifunctional phenol compound.

The bifunctional phenol compound (B) is exemplified below, but if it is bifunctional, it is not limited to the following. Bisphenol A, Bisphenol F (above, manufactured by Nittetsu Chemical & Materials Co., Ltd.), Bisphenol Fluolene, Bisphenol Fluolen (above, 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 Kagaku Kogyo Co., Ltd.), bisphenols such as bisphenol S, hydroquinone, methylhydroquinone, dibutylhydroquinone. , Resolcin, methylresorcin, catechol, methylcatechol and other benzenediols, naphthalenediol and other naphthalenediols, biphenols, dimethylbiphenols, tetramethylbiphenols and other biphenols and the like. Of these, bisphenol compounds or biphenol compounds are preferable.

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 most abundant component 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.

The organic solvent is not an essential component in the precursor mixture. The total amount of the epoxy resin (A) and the bifunctional phenol compound (B) is preferably 10 parts by weight or less with respect to 100 parts by weight. It is more preferably 5 parts by weight or less, and preferably not contained. When an organic solvent is used, the boiling point of the organic solvent at 1 atm is preferably 200 ° C. or lower.

The melting conditions of the precursor mixture depend on the melting point of the bifunctional phenol compound (B) used, but it is preferably melted at 200 ° C. or lower. Alternatively, the epoxy resin (A) may be added to a place where the bifunctional phenol compound (B) is previously melted at 300 ° C. or lower, preferably 200 ° C. or lower, rapidly cooled, and mixed at 150 ° C. or lower.

Here, the blending ratio of the epoxy resin (A) and the bifunctional phenol compound (B) is 0.9 to 1.1 mol of the bifunctional phenol compound (B) with respect to 1 mol of the epoxy resin (A). There are, preferably 0.95 to 1.05 mol, more preferably 0.96 to 1.04 mol, still more preferably 0.97 to 1.03 mol. When the blending ratio of the bifunctional phenol compound (B) is within this range, the molecular weight of the obtained field-polymerized thermoplastic epoxy resin is sufficiently extended, which is preferable.

It is desirable that the melt mixture is completely melted, but for example, when the melt mixture is placed in a glass petri dish so as to have a thickness of 2 mm and the haze value in the thickness direction is measured, the haze value is measured. If the haze value in the thickness direction is less than 30%, it is determined that the mixture has been dissolved 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%.

Further, 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 precursor mixture of the thermoplastic epoxy resin and the material after that become too soft, and the handleability at around room temperature may deteriorate. Further, if the viscosity exceeds 50 Pa · s, the workability when blending the polymerization catalyst in the next step may deteriorate, or the storage stability may deteriorate because the treatment at a high temperature is required. There is. 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.

Further, the weight average molecular weight of the precursor mixture according to the standard polystyrene calibration curve is preferably 300 or more and 500 or less. A more preferable weight average molecular weight is 300 or more and 450 or less, and preferably 300 or more and 400 or less. By keeping the weight average molecular weight within the range, it is easy to set the viscosity of the precursor mixture at 60 ° C. in a preferable range.

The epoxy resin composition of the present invention is obtained by mixing a precursor mixture and a polymerization catalyst. Examples of the polymerization catalyst that can be used include phosphine compounds, quaternary phosphonium salts, imidazoles, and tertiary amines. Among these, phosphine compounds are particularly preferable, and triphenylphosphine, tris (o-tolyl) phosphine, tris (p-tolyl) phosphine, tris (p-methoxyphenyl) phosphine, and tris (2,6-dimethoxyphenyl) phosphine ( (Made by Hokuko Chemical Industry Co., Ltd.) is particularly preferable. As the quaternary phosphonium salt, Hishikorin PX-4MP and Hishikorin PX-4ET (both manufactured by Nippon Chemical Industrial Co., Ltd.) are preferable. Further, as imidazoles, 2-phenylimidazole and 2,3-dihydro-1H-pyrrolo- [1,2-a] benzimidazole (both manufactured by Shikoku Chemicals Corporation) are preferable. The blending amount of the polymerization catalyst is 0.05% by weight or more and 10% by weight or less with respect to 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 does not increase sufficiently, or the polymerization takes time and the productivity is impaired. On the other hand, when it is used in excess of 10% by weight, not only the storage stability is impaired but also the molecular weight does not increase sufficiently.

The epoxy resin composition of the present invention is a mixture containing an epoxy resin, a phenol 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 the organic solvent used is 10% by weight or less of the sum of the epoxy resin and the phenol compound, preferably 5% by weight or less, and further preferably 1% by weight or less. When the organic solvent is used in an amount of more than 10% by weight, there is a problem that the molecular weight of the polymer does not increase sufficiently.

Further, 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 component in the resin sheet or prepreg, which will be described later, becomes too soft, which may result in poor handleability near room temperature. Further, when the viscosity exceeds 150 Pa · s, it is necessary to raise the temperature of the step of applying to the film and the step of impregnating the reinforcing fiber to a high temperature, which may affect the storage stability. A more preferable 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 for the epoxy resin composition, similarly to the precursor mixture, the haze value in the thickness direction when the thickness is set to 2 mm is preferably less than 30%, more preferably less than 20%, still more preferably. Should be less than 10%.

The epoxy resin composition sheet is a base film coated with an epoxy resin composition. It can be sandwiched between cover films if necessary. As the base film, polyimide, polyethylene terephthalate, polybutylene terephthalate, polyethylene, paper and the like are generally used. The base film may or may not be mold-released, but in the case of paper, mold-release treatment is required. When a cover film is used, a polyethylene film or paper that has undergone mold 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 will be described later, this may be attached to an adherend and thermally polymerized, or may be impregnated into reinforcing fibers or the like. The thermal polymerization at that time is usually carried out in the range of 100 ° C to 200 ° C. When the thermal polymerization temperature is less than 100 ° C., the glass transition temperature of the polymer exceeds this during the polymerization, so that the reaction does not proceed sufficiently. If the reaction exceeds 200 ° C, an undesired side reaction may occur and gelation may occur. The time required for polymerization is usually 5 minutes to 6 hours. If the reaction temperature is high, the time will be short, but if it is less than 5 minutes, the polymerization reaction will not proceed sufficiently. Further, if it exceeds 6 hours, the productivity is deteriorated, which is not preferable.

The thermoplastic epoxy resin is a thermoplastic epoxy resin obtained by polymerizing an epoxy resin composition or an epoxy resin composition sheet. When the epoxy resin composition sheet is used, a sheet-shaped thermoplastic epoxy resin can be obtained. In order to exhibit thermoplasticity, the solvent insoluble content (gel content) must be 0% by weight or more and 10% by weight or less. The solvent-insoluble component (gel fraction) can be measured by the method described in Examples.
The molecular weight of the thermoplastic epoxy resin is 5000 or more, preferably 7500 or more, and preferably 10000 or more in terms of number average molecular weight. When the number average molecular weight is less than 5000, it cannot be said that the degree of polymerization is sufficient to obtain sufficient mechanical strength, and the strength cannot be obtained. There is no particular limitation on the upper limit, but in general, when the number average molecular weight exceeds 30,000, polymerization does not proceed easily, and a product of 50,000 or less can be obtained. The weight average molecular weight is 50,000 or more, preferably 300,000 or less. The dispersion represented by the polymerization average molecular weight / number average molecular weight is preferably 1 or more and 20 or less, and preferably 2 or more and 15 or less. When the dispersion exceeds 20, it tends to be easy to gel. Also, the variance will never be less than 1.

The reinforcing fiber is a fiber for reinforcing the thermoplastic epoxy resin which is a matrix resin, and examples thereof include carbon fiber, glass fiber, and aramid fiber. Further, the form of these fibers is not limited, and any form such as long fibers, chopped fibers, non-woven fabrics, and cloths can be used.

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 develop the desired strength. Therefore, it is desirable to reduce voids during impregnation. As a means for that, heat treatment can be performed. The heat treatment is generally performed at 50 ° C. or higher and 100 ° C. or lower. If the temperature is lower than 50 ° C., the viscosity of the resin cannot be sufficiently lowered, and impregnation failure may occur. If the temperature exceeds 100 ° C., the polymerization reaction may proceed. The heat treatment time is usually 5 seconds or more and 3 minutes or less. If it is less than 5 seconds, sufficient low viscosity 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. Further, as a means for further improving the impregnation accuracy, thermocompression bonding by a thermal roll or the like can be mentioned. The pressure depends on the substrate, but is 0.1 kgf / cm or more and 10 kgf / cm or less. If the linear pressure is less than 0.1 kgf / cm, the 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 the resin and the reinforcing fiber is 30:70 to 80:20. If the resin ratio is less than 30, there is a problem that the resin is insufficient and the number of voids increases. When the resin ratio exceeds 80, the amount of reinforcing fibers is small, so that sufficient characteristics cannot be obtained.

In the present invention, the field-polymerized thermoplastic fiber reinforced plastic is a heat-polymerized epoxy resin prepreg. Its molecular weight is a number average molecular weight (Mn) of 5000 or more, preferably 7500 or more, and preferably 10000 or more. When the number average molecular weight is less than 5000, it cannot be said that the degree of polymerization is sufficient to obtain sufficient mechanical strength, and the strength cannot be obtained. There is no particular limitation on the upper limit, but in general, when the number average molecular weight exceeds 30,000, the polymerization is difficult to proceed and a product of 50,000 or less can be obtained. The weight average molecular weight (Mw) is 50,000 or more, preferably 300,000 or less. The dispersion represented by the polymerization average molecular weight / number average molecular weight is preferably 1 or more and 20 or less, and preferably 2 or more and 15 or less. When the dispersion exceeds 20, it tends to be easy to gel. Also, the variance will never be less than 1.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, "parts" represents parts by weight and "%" represents% by weight. The raw materials used in the following examples are as follows.

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

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

[Organic solvent]
C1: Cyclohexanone (first-class reagent, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.)

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

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

Example 1
278.1 parts of A1 and 50.0 parts of B1 and 150.0 parts of B2 were weighed and pulverized and mixed using a Henschel mixer. Subsequently, melt mixing was performed using an S1KRC kneader (manufactured by Kurimoto, Ltd.) whose barrel temperature was preheated to 170 ° C., the entire amount was recovered in a metal can, cooled with stirring, and a precursor of a thermoplastic epoxy resin. A mixture (D1) was obtained.

The obtained precursor mixture (D1) was placed in a colorless and transparent glass petri dish so as to have a thickness of 2 mm, and the haze value in the thickness direction was set to less than 5% (with reference to the haze standard plate manufactured by Murakami Color Technology Research Institute). <5) ”“ 5% or more and less than 10% (<10) ”“ 10% or more and less than 20% (<20) ”“ 20% or more and less than 30% (<30) ”“ 30% or more (30 ≦) ” As a result of evaluation on a 5-point scale, it was less than 10%.

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

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 HLC-8420GPC manufactured by Tosoh Corporation. The column was connected in series with TSKgel G4000HXL, TSKgel G3000HXL and TSKgel G2000HXL, and the column oven was set to 40 ° C. The eluent was tetrahydrofuran and the detector was an RI detector. The flow rate was 1 mL / min on the sample side and 0.5 mL / min on the reference side. Approximately 0.05 g of the sample was weighed, 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 the elution time was corrected using cyclohexanone.

Examples 2 to 6, Comparative Examples 1 to 3
A precursor mixture of a thermoplastic epoxy resin was obtained by the same operation as in Example 1 under the conditions shown in Table 1. However, in the operations of Example 5 and Comparative Examples 1 to 3, instead of mixing with a Henschel mixer, the mixture was mixed with a rotating / revolving centrifugal stirrer and then melt-mixed 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 when the mixture was stirred in the cooling step, and the sample became turbid. Further, even during the measurement of the viscosity at 60 ° C., crystals continued to precipitate and were not stable, so the measurement was not possible.

Table 1 is described below. All of Examples 1 to 6 and Comparative Examples 1 to 3 were uniformly dissolved, and a precursor mixture which was liquid at 60 ° C. and semi-solid to liquid at room temperature could be obtained. In Comparative Example 2, it is considered that bisphenol A (BPA) recrystallized. It seems that BPA may recrystallize in Comparative Example 1, but this was not seen in this experiment. In Comparative Example 1, the thermal history is severe, and it is possible that a part of the resin component deteriorates and inhibits crystallization. It was also shown that the precipitation of crystals at room temperature can be effectively suppressed by mixing two or more kinds of phenol compounds.

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

The viscosity of the obtained epoxy resin composition (F1) at 60 ° C. was measured using MCR102 manufactured by Anton Pearl Co., Ltd. and found to be 62 Pa · s. The haze value of the epoxy resin composition was 5% or more and less than 10% (<10).

Further, the obtained epoxy resin composition (F1) was heated and stirred at about 70 ° C., poured into an iron chrome-plated mold container having a clearance set to 4 mm in advance, and placed in a hot air circulation oven at 160 ° C. for 4 hours. Thermal polymerization was carried out to obtain a thermoplastic epoxy resin.

The epoxy equivalent of the obtained thermoplastic epoxy resin was measured according to JIS K7236 and found to be 18,000 g / eq.

The glass transition temperature (Tg) of the thermoplastic epoxy resin was 123 ° C. The method for measuring Tg is as follows.
According to JIS K 7121, DSC · Tmg (glass state and rubber state) when measured with a differential scanning calorimetry device (EXSTAR6000 DSC6200, manufactured by Hitachi High-Tech Science Co., Ltd.) under a temperature rise condition of 10 ° C./min. It was expressed as the temperature (intermediate temperature of the variation curve with respect to the tangent line).

The gel fraction of the thermoplastic epoxy resin was 1% by weight or less. The method for measuring the gel fraction is as follows.
About 1 g of the sample thermoplastic epoxy resin was precisely weighed in a 100 mL vial, 50 mL of tetrahydrofuran was added, ultrasonic diffusion was performed at room temperature for 1 hour, and then the sample was allowed to stand at room temperature for 23 hours or more to dissolve. Further, the wire mesh of 500 mesh was dried in an oven at 100 ° C. for 1 hour, and the weight thereof was measured. A 500-mesh wire mesh was folded into a funnel shape, and the entire sample solution was poured onto the funnel. The sample was washed with tetrahydrofuran until no insoluble matter remained in the vial and poured into the funnel, and then the insoluble matter on the mesh and the mesh were washed with tetrahydrofuran and then dried in an oven at 100 ° C. for 4 hours or more. .. The dry weight of the mesh was subtracted from the weight of the dried sample and mesh, and this was divided by the weight of the sample to determine the gel fraction in% by weight.

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 method for measuring the molecular weight is as follows.
Analysis was performed using HLC-8320GPC manufactured by Tosoh Corporation. The column was connected in series with TSKguardcolumnHXL, TSKgel GMHXL, TSKgel GMHXL and TSKgel G2000HXL, and the column oven was set to 40 ° C. The eluent was tetrahydrofuran and the detector was an RI detector. The flow rate was 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 as a sample was weighed, 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.

As for the appearance in Table 2, those in which cracks were confirmed at the end of the test piece in the cooling step after the polymerization of the thermoplastic epoxy resin were marked with x, and those without change were marked with 〇.

Examples 8-12, Comparative Examples 4-6
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, the appearance of the thermoplastic epoxy resin, the epoxy equivalent, the gel fraction, Tg, Mn, Mw, and Mt were measured in the same manner as in Example 7, and the measurement results were obtained. Is shown in Table 2.

Table 2 is described. From Examples 7 to 12, it was possible to obtain a resin composition having a viscosity suitable for the hot melt process. In addition, almost no gelation could be confirmed in the polymer. In Comparative Example 4 and Comparative Example 5, the gel component was clearly generated in the thermoplastic epoxy resin. In Comparative Example 4 and Comparative Example 5 in which the steric hindrance around the glycidyl group is small, a heat-deteriorating component may be generated in the heat dissolution step or the thermal polymerization step, which may cause gelation during the polymerization, while the glycidyl group around the periphery. It was considered that gelation was unlikely to occur in Examples 7 to 12 in which the steric hindrance was large. Further, it is probable that Comparative Example 6 did not gel because the polymerization did not proceed sufficiently.

Example 13
The release paper that had been released from the mold was fixed on a hot plate preheated to 70 ° C. so that the release surface was facing up, and the epoxy resin composition (F1) obtained in Example 6 was placed on the release paper. After putting it on, it was coated to a thickness of 50 μm using a bar coater preheated to 70 ° C. Immediately after coating, it was removed from the hot plate and air-cooled to obtain an epoxy resin composition sheet.
Subsequently, carbon fibers (I1) were laminated on the obtained epoxy resin composition sheet so as to have a strand density of 15 strands per 10 cm, and the surface pressure was 0.5 MPa using a hot press preheated to 90 ° C. After 1 minute, the pressure was applied so as to be the same, and the mixture was taken out and air-cooled to obtain an epoxy resin prepreg having Rc = 33%.
Further, nine of the obtained epoxy resin prepregs were laminated, sandwiched between release films, and vacuum-pressed to obtain a field-polymerized thermoplastic fiber reinforced plastic. The conditions for vacuum pressing were 160 ° C., 0.5 MPa, and 4 hours.

As a result of determining the gelation of the obtained thermoplastic fiber reinforced plastic, it was not gelled. To determine gelation, about 0.1 g of the test piece was dissolved in 10 mL of tetrahydrofuran by ultrasonic diffusion, and the loosened carbon fiber bundle was judged to be gel-free. Those in which the carbon fiber bundles were not loosened were judged to be gelled, and were judged to be "x".

The Mn, Mw, and Mt of the thermoplastic fiber reinforced plastic were 23000, 76000, and 33000, respectively. The method for measuring the molecular weight is the method described in Example 7.

Examples 14-18, Comparative Examples 7-9
A thermoplastic fiber reinforced plastic was obtained by the same operation as in Example 13 except that the epoxy resin composition shown in Table 3 was used. Judgment of gelation of the obtained thermoplastic fiber reinforced plastic, Mn, Mw, and Mt were measured in the same manner as in Example 13, and the measurement results are shown in Table 3.

Table 3 is described. In Examples 13 to 18, it was confirmed that the cured product was polymerized and that the fibers were disintegrated when dissolved in tetrahydrofuran. On the other hand, Comparative Example 7 and Comparative Example 8 were hardly dissolved in tetrahydrofuran, and the fibers did not come apart. Comparative Example 9 was dissolved in tetrahydrofuran, but the degree of polymerization was not sufficient, and the function as a structural material could not be said to be sufficient.

The precursor mixture of the present invention can be used for an epoxy resin composition (sheet), and can be particularly preferably used for a field-polymerized thermoplastic epoxy resin, prepreg, thermoplastic fiber reinforced plastic, or the like.

Claims (15)

1. A precursor mixture used in a field-polymerized thermoplastic epoxy resin obtained by addition polymerization of an epoxy resin and a bifunctional phenol compound.
   An epoxy resin containing 50% by weight or more of the bifunctional epoxy resin (a) represented by the following formula (1) and a bifunctional phenol compound are contained as essential components, and the bifunctional phenol compound is contained in 1 mol of the epoxy resin. Is 0.9 to 1.1 mol, and the precursor mixture has a viscosity at 60 ° C. of 1 Pa · s or more and 50 Pa · s or less.
   

   

   (Here, A in the formula (1) is the formula (2), n is the number of repetitions and the average value is 0 to 5. 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. The precursor mixture according to claim 1, wherein the haze value in the thickness direction when the thickness is 2 mm is less than 30%.
3. The precursor mixture according to claim 1 or 2, wherein the weight average molecular weight according to a standard polystyrene calibration curve is 300 or more and 500 or less.
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 ratio of the most abundant component in the bifunctional phenol compound is 90% by weight or less.
6. An epoxy resin composition obtained by blending a polymerization catalyst with the precursor mixture according to any one of claims 1 to 5 and dissolving them together.
7. The epoxy resin composition according to claim 6, wherein the haze value in the thickness direction when the thickness is 2 mm is less than 30%.
8. The epoxy resin composition according to claim 6 or 7, wherein the viscosity at 60 ° C. is 3 Pa · s or more and 150 Pa · s or less.
9. A field-polymerized thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition according to any one of claims 6 to 8.
10. The field-polymerized thermoplastic epoxy resin according to claim 9, wherein the gel content is 0% by weight or more and 10% by weight or less.
11. An epoxy resin composition sheet obtained from the epoxy resin composition according to any one of claims 6 to 8 having a thickness of 10 μm or more and 300 μm or less.
12. A sheet-shaped field-polymerized thermoplastic epoxy resin obtained by polymerizing the epoxy resin composition sheet according to claim 11.
13. The sheet-shaped in-situ polymerization type thermoplastic epoxy resin according to claim 12, wherein 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 a reinforcing fiber.
15. A field-polymerized thermoplastic fiber reinforced plastic obtained by polymerizing the prepreg according to claim 14.