JP2021116349A - Epoxy resin composition, prepreg and fiber-reinforced plastic - Google Patents

Abstract

To provide an epoxy resin composition and a prepreg that can complete their curing in a short time even at low temperature and yield a fiber-reinforced plastic superior in mechanical properties such as flexural strength, flexural modulus, fracture strain as well as heat resistance, and to provide such a fiber-reinforced plastic superior in mechanical properties such as flexural strength, flexural modulus, fracture strain as well as heat resistance.SOLUTION: An epoxy resin composition contains at least specific components (A) and (D). When the epoxy resin composition is cured under conditions of 140°C and 30 minutes, a resultant cured product has a flexural strength of 155 MPa or more and a flexural modulus of 3.3 GPa or more, and has a glass transition temperature of 125°C or higher, and a rubber state elastic modulus of 10 MPa or less in dynamic viscoelasticity evaluation.SELECTED DRAWING: None

Description

The present invention relates to epoxy resin compositions, prepregs, and fiber reinforced plastics.

Fiber reinforced plastic, which is one of the fiber reinforced composite materials, is lightweight, has high bending strength, and has high rigidity, so that it is widely used from sports / leisure applications to industrial applications such as automobiles and aircraft. Among the fiber-reinforced plastics, the fiber-reinforced plastic tubular body is widely used for sports and leisure applications such as fishing poles, golf club shafts, ski poles, and bicycle frames.

As a method for producing fiber reinforced plastic, there is a method of using an intermediate material, that is, a prepreg, in which a reinforcing material made of long fibers such as reinforcing fibers is impregnated with a matrix resin. According to this method, there is an advantage that the content of the reinforcing fiber in the fiber fiber reinforced plastic can be easily controlled and the content can be designed to be higher.

Specific methods for obtaining fiber reinforced plastics using a prepreg include, for example, a molding method using an autoclave, press molding, internal pressure molding, oven molding, and the like. In any of these methods, usually, when two or more prepregs are laminated, molded into a desired mold, and then heat-cured, it takes about 2 to 6 hours to cure at about 160 ° C. or higher. I need time. That is, the production of fiber reinforced plastic requires high temperature and long treatment.
In order to improve the molding cycle, it is required that molding can be performed at a relatively low temperature of about 100 to 140 ° C. in a short time of about several minutes to several tens of minutes. Further, in order to avoid deformation when the fiber reinforced plastic is taken out from the mold, the fiber reinforced plastic is required to have heat resistance. Specifically, it is desired that the glass transition temperature of the cured prepreg, that is, the fiber reinforced plastic is higher than the temperature of the mold at the time of molding.

As the matrix resin used for the prepreg, an epoxy resin composition having excellent mechanical properties, heat resistance, and handleability is widely used. In particular, epoxy resin compositions used for sports / leisure applications, industrial applications, etc. are required to have both heat resistance and breaking strain as described above.

In order to improve the breaking strain of the epoxy resin composition, for example, it is effective to reduce the crosslink density of the cured product of the epoxy resin composition. The crosslink density of the cured product of the epoxy resin composition correlates with the rubber-like flat region storage elastic modulus and the glass transition temperature. Generally, the lower the crosslink density, the lower the elastic modulus stored in the rubber-like flat region, and the glass transition temperature tends to decrease. That is, the lower the crosslink density, the better the breaking strain of the cured product of the epoxy resin composition, but the more easily the heat resistance decreases. As the glass transition temperature of the cured product of the epoxy resin composition decreases, the glass transition temperature of the fiber reinforced plastic also decreases. Therefore, it is difficult to achieve both breaking strain and heat resistance of the fiber reinforced plastic.
Therefore, epoxy resin compositions and prepregs can be used to obtain fiber-reinforced plastics that can be cured in a short time even at low temperatures, enable high-cycle molding, and have excellent mechanical properties, especially excellent heat resistance and fracture strain. Is required.

As a prepreg having excellent heat resistance and bending strength, Patent Document 1 discloses a prepreg using an epoxy resin having a rigid skeleton and an epoxy resin having a high weight average molecular weight. Further, as a prepreg having excellent tensile bending strength and heat resistance, Patent Document 2 uses a phenylglycidyl ether type epoxy resin and a fluorene type epoxy resin, which are characterized by having a rubber-like flat region storage elastic modulus of 10 MPa or less. The prepreg that was there is disclosed.

Japanese Unexamined Patent Publication No. 2005-330482 Japanese Unexamined Patent Publication No. 2017-119813

However, the epoxy resin composition described in Patent Document 1 requires a curing time of 90 minutes at 130 ° C. Further, the epoxy resin composition described in Patent Document 2 requires a curing time of 4 hours at 150 ° C. after being cured at 100 ° C. for 2 hours, and the glass transition temperature is about 110 ° C.

The present invention comprises an epoxy resin composition and a prepreg that can be cured in a short time even at a low temperature and can obtain a fiber reinforced plastic having excellent mechanical properties such as bending strength, flexural modulus and breaking strain, and heat resistance, and bending strength. It is an object of the present invention to provide a fiber reinforced plastic having excellent mechanical properties such as flexural modulus and breaking strain and heat resistance.

The present invention includes the following aspects [1] to [6].
[1] An epoxy resin composition containing at least the following components (A) and (D), and the cured product obtained by curing the epoxy resin composition at 140 ° C. for 30 minutes has a bending strength of 155 MPa or more and a flexural modulus of 3. An epoxy resin composition having 3 GPa or more, a glass transition temperature of 125 ° C. or more, and a rubber state elastic modulus of 10 MPa or less in the dynamic viscoelasticity evaluation.
Component (A): Fluorene type epoxy resin component (D): Hardener
[2] The epoxy resin composition according to claim 1, wherein the epoxy resin composition contains a component (B) and a component (C).
Component (B): Oxazoridone type epoxy resin Component (C): Triglycidyl aminophenol type epoxy resin
[3] The epoxy resin composition according to [1] or [2], wherein the epoxy equivalent of the component (A) is 200 to 350.
[4] The epoxy resin composition according to any one of [1] to [3], wherein the component (D) is an amine type curing agent.
[5] The prepreg according to any one of [1] to [4], wherein the reinforcing fiber is a carbon fiber.
[6] A fiber-reinforced plastic which is a cured product of a laminated body in which two or more prepregs according to [5] are laminated.
[7] An epoxy resin composition containing the following components (A) to (D).
Component (A): Fluorene type epoxy resin component (B): Oxazolidene type epoxy resin component (C): Triglycidyl aminophenol type epoxy resin component (D): Curing agent

The prepreg of the present invention can be cured in a short time even at a low temperature, and a fiber reinforced plastic having excellent mechanical properties such as bending strength, flexural modulus, and breaking strain and heat resistance can be obtained. The fiber-reinforced plastic of the present invention is excellent in mechanical properties such as bending strength, flexural modulus, breaking strain, and heat resistance.

[Prepreg]
The prepreg of the present invention contains an epoxy resin composition and reinforcing fibers.

<Epoxy resin composition>
One aspect of the epoxy resin composition comprises at least the components (A) and (D). Further, one aspect of the epoxy resin composition is that the cured product obtained by curing the epoxy resin composition at 140 ° C. for 30 minutes has a bending strength of 155 MPa or more, a flexural modulus of 3.3 GPa or more, and a glass transition temperature of 125 ° C. As described above, the composition has a rubber state elastic modulus of 10 MPa or less in the dynamic viscoelasticity evaluation. Moreover, the epoxy resin composition may contain a component (arbitrary component) other than the component (B), the component (C) and the component (D) shown below. From the viewpoint of heat resistance, the glass transition temperature, which is an index of the heat resistance of the cured product of the epoxy resin composition, is preferably 130 ° C. or higher, more preferably 135 ° C. or higher, and even more preferably 140 ° C. or higher. Further, from the viewpoint of toughness, 250 ° C. or lower is preferable, 200 ° C. or lower is more preferable, and 180 ° C. or lower is further preferable. The bending strength of the cured product obtained by curing the epoxy resin composition at 140 ° C. for 30 minutes is preferably 160 MPa or more, more preferably 170 MPa or more, and preferably 180 MPa or less from the viewpoint of cost. The flexural modulus of the cured product is preferably 3.5 GPa or more, more preferably 4.0 GPa or more, and preferably 4.5 GPa or less from the viewpoint of cost. The elastic modulus in the rubber state in the dynamic viscoelasticity evaluation of the cured product is preferably 9 MPa or less, more preferably 8 MPa or less, and preferably 6 MPa or more, more preferably 7 MPa or more from the viewpoint of fracture strain.

(Ingredient (A))
The component (A) is a fluorene type epoxy resin. The fluorene type epoxy resin is an epoxy resin having a fluorene ring structure. When the epoxy resin composition contains the component (A), it is possible to improve the mechanical properties and heat resistance of the cured product of the epoxy resin composition (hereinafter, also referred to as "resin cured product") in terms of bending strength and flexural modulus. It becomes.

・・・・・（１）
（式（１）中、Ｒ^１およびＲ^２はそれぞれ独立に置換基、Ｒ^３はそれぞれ独立に水素原子またはアルキル基を示し、Ａは縮合多環式芳香族炭化水素環、aは１以上の整数、bは０以上の整数、cは０〜４の整数である。）
前記式（１）において、Ｒ^１で表される置換基としては、例えば、シアノ基、ハロゲン原子、炭化水素基などが挙げられ、特に、ハロゲン原子、シアノ基またはアルキル基であることが好ましい。ハロゲン原子としては、フッ素原子、塩素原子、臭素原子、ヨウ素原子などが挙げられる。アルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、ｔ−ブチル基などが挙げられる。アルキル基の炭素数は１〜６であることが好ましい。なお、cが２以上である場合、Ｒ^１は互いに異なっていてもよく、同一であってもよい。フルオレン骨格を構成する２つのベンゼン環に置換するＲ^１は同一であってもよく、異なっていてもよい。また、フルオレンを構成するベンゼン環に対するＲ^１の結合位置は、特に限定されない。好ましい置換数ｃは、０〜１が好ましく、０がより好ましい。なお、フルオレンを構成する２つのベンゼン環において、置換数ｃは、互いに同一であってもよく、異なっていてもよい。Ａに置換するＲ^２としては、アルキル基、アルコキシ基、アリールオキシ基、アラルキルオキシ基、アシル基、ハロゲン原子、ニトロ基、シアノ基、アミノ基などが挙げられ、特に、アルキル基、アルコキシ基、またはハロゲン原子が好ましい。アルキル基、ハロゲン原子としては先に述べた基が挙げられ、アルコキシ基としては、メトキシ基、エトキシ基などが挙げられる。なお、同一のＡにおいて、ｂが複数である場合、Ｒ^２は互いに異なっていてもよく、同一であってもよい。また、２つのＡにおいて、Ｒ^２は同一であってもよく、異なっていてもよい。置換数bは、好ましくは０〜８、より好ましくは０〜６、さらに好ましくは０〜４、特に０〜２が好ましい。なお、２つのＡにおいて、置換数bは、互いに同一または異なっていてもよい。
Ｒ^３は、水素原子またはメチル基であり、好ましいＲ^３は水素原子である。 置換数aは、１〜４が好ましく、１〜３がより好ましく、１〜２がさらに好ましい。１が特に好ましい。。置換数aは、それぞれのＡに結合しているエポキシ基を含有する基において、同一または異なっていてもよく、同一であることが好ましい。なお、エポキシ基を含有する基の置換位置は、特に限定されないが、縮合多環式炭化水素環において、フルオレンの９位に結合した炭化水素環とは異なる炭化水素環（例えば、ナフタレン環の５位、６位など）に置換していることが好ましい。 The fluorene type epoxy resin preferably has a structure represented by the following formula (1).

(1)
(In the formula (1), R ¹ and R ² each independently represent a substituent, R ³ each independently represents a hydrogen atom or an alkyl group, A is a condensed polycyclic aromatic hydrocarbon ring, and a is one or more. An integer, b is an integer of 0 or more, and c is an integer of 0 to 4.)
In the above formula (1) ^{, examples of the substituent represented by R 1} include a cyano group, a halogen atom, a hydrocarbon group and the like, and a halogen atom, a cyano group or an alkyl group is particularly preferable. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a t-butyl group and the like. The alkyl group preferably has 1 to 6 carbon atoms. When c is 2 or more, R ¹ may be different from each other or may be the same. R ¹ to be substituted with two benzene rings constituting the fluorene skeleton may be the same or may be different. Further, the bonding position of R ¹ for benzene rings constituting the fluorene is not particularly limited. The preferred number of substitutions c is preferably 0 to 1, more preferably 0. In the two benzene rings constituting fluorene, the substitution number c may be the same as or different from each other. ^{Examples of R 2} substituted with A include an alkyl group, an alkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a halogen atom, a nitro group, a cyano group, an amino group and the like, and in particular, an alkyl group, an alkoxy group and the like. Alternatively, a halogen atom is preferable. Examples of the alkyl group and halogen atom include the groups described above, and examples of the alkoxy group include a methoxy group and an ethoxy group. In the same A, when there are a plurality of b, R ² may be different from each other or may be the same. Further, in the two A, R ² may be the same or different. The number of substitutions b is preferably 0 to 8, more preferably 0 to 6, still more preferably 0 to 4, and particularly preferably 0 to 2. In addition, in two A, the substitution number b may be the same or different from each other.
R ³ is a hydrogen atom or a methyl group, preferably R ³ is a hydrogen atom. The number of substitutions a is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 to 2. 1 is particularly preferable. .. The number of substitutions a may be the same or different in the group containing the epoxy group bonded to each A, and is preferably the same. The substitution position of the group containing an epoxy group is not particularly limited, but in the condensed polycyclic hydrocarbon ring, a hydrocarbon ring different from the hydrocarbon ring bonded to the 9-position of fluorene (for example, 5 of the naphthalene ring). It is preferable to replace it with a position, a 6-position, etc.).

The epoxy equivalent of the component (A) is preferably 200 to 350, preferably 200 to 320, more preferably 230 to 310, and even more preferably 250 to 310. When the epoxy equivalent of the component (A) is equal to or higher than the lower limit value, the bending strength, flexural modulus and heat resistance of the cured resin product tend to be improved and the breaking strain tends to be maintained, and the fiber has both mechanical properties and heat resistance. Reinforced plastic is obtained. If it is not more than the upper limit value, a cured resin product having heat resistance tends to be obtained.

Commercially available products of the component (A) include "Ogsol (registered trademark)" CG-500 (epoxy equal amount: 296 g / eq), "Ogsol (registered trademark)" PG-100 (epoxy equal amount: 260 g / eq), and the like. Examples thereof include "Ogsol (registered trademark)" EG-200 (epoxy equal amount: 290 g / eq) (all manufactured by Osaka Gas Chemical Co., Ltd.). As the component (A), one type may be used alone, or two or more types may be used in combination.

The content of the component (A) with respect to the total mass (100 parts by mass) of the total epoxy resin contained in the epoxy resin composition is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and 20 to 30 parts by mass. More preferred.
If the content of the component (A) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is at least the lower limit, the heat resistance and mechanical characteristics of the cured resin tend to be improved. A fiber-reinforced plastic having both heat resistance and mechanical properties can be obtained. When the content of the component (A) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is not more than the upper limit value, a prepreg having excellent tack and drape properties can be obtained and the prepreg is broken. There is a tendency to obtain a cured resin product having high strain and no voids.

(Component (B))
The component (B) is an oxazolidone type epoxy resin. The oxazolidone type epoxy resin is an epoxy resin having an oxazolidone ring structure.
When the epoxy resin composition contains the component (B), the workability of the prepreg at room temperature is improved. Further, the heat resistance, breaking strain, and adhesiveness of the cured resin product to the reinforcing fibers are enhanced, and a fiber reinforced plastic having excellent heat resistance and breaking strain can be obtained. In addition, in this specification, "normal temperature" means 30 degreeC.

・・・・・（２）
（式（２）中、ｎ、ｍはそれぞれ独立に０以上の整数であり、Ｙは置換基を有していてもよい２価の基を示す。Ｚは炭素数１〜８のアルキル基、炭素数６〜１０のアリール基及び炭素数６〜１０のアラルキル基から選ばれる置換基を少なくとも１個有する環員数５〜８のシクロアルキリデン基を示す。Ｒ^４はそれぞれ独立して水素原子、炭素数１〜８のアルキル基、炭素数１〜８のアルコキシ基、炭素数６〜１０のアリール基、炭素数６〜１０のアラルキル基、炭素数６〜１０のアリールオキシ基または炭素数６〜１０のアラルキルオキシ基を示す。）
式（２）において、炭素数１〜８のアルキル基及び炭素数１〜８のアルコキシ基としては、前記式（１）において、Ｒ^１において列記したものが挙げられる。炭素数６〜１０のアリール基としては、フェニル基、キシリル基、トリル基などが挙げられる。炭素数６〜１０のアラルキル基としては、ベンジル基、フェニルエチル基などが挙げられる。炭素数６〜１０のアリールオキシ基としては、フェノキシ基、ナフチルオキシ基などが挙げられる。炭素数６〜１０のアラルキルオキシ基としては、ベンジルオキシ基、ナフチルメチルオキシ基などが挙げられる。ｎ、ｍは、耐熱性の観点から、０〜５が好ましく、０〜３がより好ましい。Ｙは、下記式（２ａ）〜（２ｋ）が挙げられ、中でも（２ｃ）が好ましい。

Ｚは、入手の容易性の観点から、シクロアルキリデン基を構成するシクロアルカン環は、シクロペンタン環、シクロヘキサン環、シクロヘプタン環、またはシクロオクタン環が好ましく、いずれのＺもシクロペンタン環またはシクロヘキサン環であることが好ましい。Ｚの置換基としては、接着性等の物性の観点から、メチル基やフェニル基が好ましい。Ｒ^４は、入手の容易性及び耐熱性等の物性の観点から、水素原子、１−フェニルエチル基またはメチル基であることが好ましい。 The oxazolidone type epoxy resin preferably has a structure represented by the following formula (2).

(2)
(In the formula (2), n and m are independently integers of 0 or more, Y represents a divalent group which may have a substituent, and Z is an alkyl group having 1 to 8 carbon atoms. It represents a cycloalkylidene group having 5 to 8 ring members having at least one substituent selected from an aryl group having 6 to 10 carbon atoms and an aralkyl group having 6 to 10 carbon atoms. R ⁴ is an independent hydrogen atom and carbon, respectively. An alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 6 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms or an aryloxy group having 6 to 10 carbon atoms. Indicates the aralkyloxy group of.)
In the formula (2), the alkyl group and alkoxy group having 1 to 8 carbon atoms having 1 to 8 carbon atoms, in the formula (1) include those listed in R ^1. Examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a xsilyl group, and a tolyl group. Examples of the aralkyl group having 6 to 10 carbon atoms include a benzyl group and a phenylethyl group. Examples of the aryloxy group having 6 to 10 carbon atoms include a phenoxy group and a naphthyloxy group. Examples of the aralkyloxy group having 6 to 10 carbon atoms include a benzyloxy group and a naphthylmethyloxy group. n and m are preferably 0 to 5, more preferably 0 to 3 from the viewpoint of heat resistance. Examples of Y include the following formulas (2a) to (2k), of which (2c) is preferable.

From the viewpoint of availability, the cycloalkane ring constituting the cycloalkylene group is preferably a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, or a cyclooctane ring, and any Z is a cyclopentane ring or a cyclohexane ring. Is preferable. As the substituent of Z, a methyl group or a phenyl group is preferable from the viewpoint of physical properties such as adhesiveness. R ⁴ is preferably a hydrogen atom, a 1-phenylethyl group or a methyl group from the viewpoint of easy availability and physical properties such as heat resistance.

The oxazolidone ring structure is formed by the addition reaction of an isocyanate group and an epoxy group. The method for producing the oxazolidone type epoxy resin is not particularly limited, and for example, it can be obtained in a substantially theoretical amount by reacting an isocyanate compound and an epoxy resin in the presence of a catalyst used for forming an oxazolidone ring. The isocyanate compound and the epoxy resin are preferably reacted in an equivalent ratio (isocyanate compound: epoxy resin) in the range of 1: 2 to 1:10. When the equivalent ratio of the isocyanate compound and the epoxy resin is in the above range, the heat resistance and water resistance of the cured resin tend to be better.

The isocyanate compound used as the raw material of the component (B) is not particularly limited, but an isocyanate compound having a plurality of isocyanate groups is preferable in order to incorporate the oxazolidone ring structure into the skeleton of the epoxy resin. Further, in order for the cured resin product to have high heat resistance, diisocyanate having a rigid structure is preferable.
Specific examples of the isocyanate compound include methanediisocyanate, butane-1,1-diisocyanate, ethane-1,2-diisocyanate, butane-1,2-diisocyanate, transvinylene diisocyanate, propane-1,3-diisocyanate, butane-1. , 4-Diisocyanate, 2-butene-1,4-diisocyanate, 2-methylbutene-1,4-diisocyanate, 2-methylbutane-1,4-diisocyanate, pentane-1,5-diisocyanate, 2,2-dimethylpentane- 1,5-Diisocyanate, hexane-1,6-diisocyanate, heptane-1,7-diisocyanate, octane-1,8-diisocyanate, nonane-1,9-diisocyanate, decane-1,10-diisocyanate, dimethylsilanediisocyanate, Diphenylsilane diisocyanate, ω, ω'-1,3-dimethylbenzenediisocyanate, ω, ω'-1,4-dimethylbenzenediisocyanate, ω, ω'-1,3-dimethylcyclohexanediisocyanate, ω, ω'-1, 4-Dimethylcyclohexanediisocyanate, ω, ω'-1,4-dimethylnaphthalenediocyanate, ω, ω'-1,5-dimethylnaphthalenediocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 3- Isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-phenylenediocyanate, 1,4-phenylenediocyanate, 1-methylbenzene-2,4-diisocyanate, 1 -Methylbenzene-2,5-diisocyanate, 1-methylbenzene-2,6-diisocyanate, 1-methylbenzene-3,5-diisocyanate, diphenyl ether-4,4'-diisocyanate, diphenyl ether-2,4'-diisocyanate, Naphthalene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, biphenyl-4,4'-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 2,3'-dimethoxybisphenyl-4 , 4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxydiphenylmethane-4,4'-diisocyanate, 4,4'-dimethoxydiphenylmetha Bifunctional isocyanate compounds such as -3,3'-diisocyanate, norbornene diisocyanate, diphenylsulfite-4,4'-diisocyanate, diphenylsulphon-4,4'-diisocyanate; polymethylenepolyphenylisocyanate, triphenylmethanetriisocyanate Etc., but are limited to trifunctional or higher functional isocyanate compounds; multimers such as dimer and trimeric of the isocyanate compounds, blocked isocyanates masked with alcohol and phenol, and bisurethane compounds. is not it.
One of these isocyanate compounds may be used alone, or two or more thereof may be used in combination.

Among the above isocyanate compounds, a bifunctional isocyanate compound or a trifunctional isocyanate compound is preferable, a bifunctional isocyanate compound is more preferable, and isophorone, benzene, toluene, diphenylmethane, and so on, from the viewpoint that the heat resistance of the cured resin product tends to be further improved. A bifunctional isocyanate compound having a skeleton selected from naphthalene, norbornene polymethylene polyphenylene polyphenyl, and hexamethylene is more preferable. If the number of functional groups of the isocyanate compound is appropriately large, the storage stability of the epoxy resin composition is unlikely to decrease. If the number of functional groups of the isocyanate compound is appropriately small, the heat resistance of the cured resin product is unlikely to decrease.

Various epoxy resins can be used as the epoxy resin as the raw material of the component (B), but in order to efficiently incorporate the oxazolidone ring structure into the skeleton of the epoxy resin, it has epoxy groups at both ends of the molecule. Epoxy resin is preferred.
Specific examples of the epoxy resin include bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol S type, tetramethyl bisphenol A type, tetramethyl bisphenol F type, tetramethyl bisphenol AD type, tetramethyl bisphenol S type, and tetrabromo. Epoxy resins derived from divalent phenols such as bisphenol A type and biphenyl type; 1,1,1-tris (4-hydroxyphenyl) methane, 1,1,1- (4-hydroxyphenyl) ethane, 4,4- [1- [4- [1- (4-Hydroxyphenyl) -1-methylethyl] phenyl] ethylidene] Epoxy resin derived from tris (glycidyloxyphenyl) alkanes such as bisphenol; phenol novolac type, cresol novolac type , Epoxy resin derived from Novolak such as bisphenol A Novolak type, etc., but is not limited thereto. One of these epoxy resins may be used alone, or two or more of these epoxy resins may be used in combination. As the epoxy resin, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and a biphenyl type epoxy resin are preferable from the viewpoint of suppressing an excessive increase in the viscosity of the component (B).

As the isocyanate compound, a bifunctional isocyanate having a toluene skeleton such as tolylene diisocyanate (for example, 1-methylbenzene-2,4-diisocyanate, 1-methylbenzene-2,5-diisocyanate, 1-methylbenzene-2,6) The addition reaction product obtained by mixing and reacting one molecule of −diisocyanate, 1-methylbenzene-3,5-diisocyanate) and two molecules of bisphenol A diglycidyl ether as an epoxy resin is the workability of prepreg at room temperature. It is particularly preferable to improve the heat resistance of the cured resin product.

Commercially available products of the component (B) include, for example, AER4152, AER4151, LSA3301, LSA2102 (trade name, manufactured by Asahi Kasei E-Materials Co., Ltd.); ACR1348 (trade name, manufactured by ADEKA Corporation); DER (registered trademark). 852, 858 (both trade names, manufactured by Dow Chemical Japan Co., Ltd.); TSR-400 (trade name, manufactured by DIC Co., Ltd.); YD-952 (trade name, manufactured by Nittetsu Chemical & Materials Co., Ltd.) Made) and the like. Both are preferably used in the present invention, but YD-952 is particularly preferable.
As the component (B), one type may be used alone, or two or more types may be used in combination.

The content of the component (B) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is 40 to 70% by mass, preferably 40 to 65% by mass, more preferably 40 to 60% by mass. It is preferably 40 to 50% by mass, and particularly preferably 40 to 50% by mass.
When the content of the component (B) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is equal to or higher than the lower limit, the heat resistance of the cured resin, the adhesiveness to the carbon fiber, and the mechanical properties Is tending to improve, and a fiber-reinforced plastic having both heat resistance and mechanical properties can be obtained. When the content of the component (B) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is not more than the upper limit value, a prepreg having excellent tack and drape properties can be obtained and the prepreg is broken. There is a tendency to obtain a cured resin product having high strain and no voids.

(Component (C))
The component (C) is a triglycidyl aminofer type epoxy resin. When the epoxy resin composition contains the component (C), it is possible to improve the bending strength and flexural modulus of the cured resin product.

・・・・・（３）
（式（３）中、Ｒ^５は水素原子、または、アルキル基またはアルケニル基を示す。）
Ｒ^５のアルキル基としては、メチル基、エチル基、イソプロピル基、ブチル基、ｔ−ブチル基などが挙げられる。Ｒ^４のアルケニル基としては、ビニル基、アリル基等が挙げられる。この中でも、水素原子、または、メチル基が好ましい。弾性率等の観点から、下記式（４）または（５）で表される構造を有するエポキシ樹脂であることが好ましい。下記式（４）で表される構造を有するエポキシ樹脂がより好ましい。

・・・・・（４）

・・・・・（５） The triglycidyl aminofer type epoxy resin preferably has a structure represented by the following formula (3).

(3)
(In the formula (3), ^{R 5} is a hydrogen atom, or an alkyl or alkenyl group.)
Examples ^{of the alkyl group of R 5} include a methyl group, an ethyl group, an isopropyl group, a butyl group, a t-butyl group and the like. Examples ^{of the alkenyl group of R 4} include a vinyl group and an allyl group. Of these, a hydrogen atom or a methyl group is preferable. From the viewpoint of elastic modulus and the like, an epoxy resin having a structure represented by the following formula (4) or (5) is preferable. An epoxy resin having a structure represented by the following formula (4) is more preferable.

(4)

・ ・ ・ ・ ・ (5)

Commercially available products of the component (C) include MY0600, MY0610 (both trade names, manufactured by Huntsman Japan Corporation) and Epototo, which are triglycidyl-m-aminophenol type epoxy resins represented by the formula (4). YH-513 (trade name, manufactured by Nittetsu Chemical & Materials Co., Ltd.), MY0500, MY0510 (both trade names, Huntsman Japan), which are triglycidyl-p-aminophenol type epoxy resins represented by the formula (5). (Manufactured by Nittetsu Chemical & Materials Co., Ltd.), Epototo YH-523 (trade name, manufactured by Nittetsu Chemical & Materials Co., Ltd.), etc. In addition, two or more types of epoxy resins as described above can be used in combination.

The content of the component (C) with respect to the total mass (100 parts by mass) of the total epoxy resin contained in the epoxy resin composition is preferably 5 to 30 parts by mass, more preferably 5 to 20 parts by mass, and 5 to 15 parts by mass. More preferred. When the content of the component (C) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is at least the lower limit value, the bending strength and bending elasticity of the cured resin tend to be improved. , A fiber-reinforced plastic that has both mechanical properties and heat resistance can be obtained. When the content of the component (C) with respect to the total mass (100% by mass) of the total epoxy resin contained in the epoxy resin composition is not more than the upper limit value, a prepreg having excellent tackiness and drape property tends to be obtained.

(Component (D))
Component (D) is a curing agent. As the component (D), ureas, imidazoles, amines, acid anhydrides, boron chloride amine complexes and the like can be used. Among these, amines are preferable. Among the amines, diaminodiphenylsulfone and diaminodiphenylmethane, which are aromatic amines, dicyandiamide or a derivative thereof, and hydrazide compounds, which are aliphatic amines, are used because they are excellent in mechanical properties and heat resistance. One type of these amine curing agents may be used alone, or two or more types may be used in combination. Of these, dicyandiamide or a derivative thereof is particularly preferable. Since dicyandiamide or a derivative thereof has a high melting point and its compatibility with an epoxy resin is suppressed in a low temperature region, a curable resin composition having an excellent pot life tends to be obtained, which is preferable. Further, since dicyandiamide or a derivative thereof is a particulate thermoactive latent curing agent, it can be cured at a relatively low temperature by combining with other components. In this case, it is preferable to combine with ureas because the reduction in breaking strain can be suppressed.

The content of the component (D) with respect to the total mass (100 parts by mass) of the total epoxy resin contained in the epoxy resin composition is preferably 2 to 15 parts by mass, more preferably 5 to 9 parts by mass. When the content of the component (D) with respect to the total mass (100 parts by mass) of all the epoxy resins contained in the epoxy resin composition is at least the lower limit value, the curing reaction proceeds sufficiently. When the content of the component (D) with respect to the total mass (100 parts by mass) of all the epoxy resins contained in the epoxy resin composition is not more than the upper limit value, the storage stability of the epoxy resin composition is enhanced and the cured resin is obtained. Good physical properties can be maintained.

(Arbitrary ingredient)
Examples of the optional component include an epoxy resin other than the component (A), the component (B) and the component (C) (hereinafter, also referred to as “another epoxy resin”), a thermoplastic resin, an additive and the like.

Examples of other epoxy resins include bifunctional epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and modified epoxy resins; naphthalene type epoxy resin, glycidylamine type epoxy resin, and these epoxy resins. Examples thereof include, but are not limited to, trifunctional or higher functional epoxy resins such as modified epoxy resins. One of these other epoxy resins may be used alone, or two or more of them may be used in combination.

Examples of commercially available bifunctional epoxy resins include those shown below.
Commercially available products of bisphenol A type epoxy resin include, for example, jER 825, 826, 827, 828, 834, 1001 (trade name, manufactured by Mitsubishi Chemical Corporation); Epicron 850 (trade name, manufactured by DIC Corporation). Epoxy (registered trademark. The same shall apply hereinafter) YD-128 (trade name, manufactured by Nippon Steel & Sumitomo Metal Chemical Corporation); DER 331, 332 (both trade names, manufactured by Dow Chemical Japan Co., Ltd.); Bakelite (registered trademark). (The same applies hereinafter), EPR154, EPR162, EPR172, EPR173, EPR174 (trade names, all manufactured by Bakelite AG) and the like can be mentioned.
Commercially available products of bisphenol F type epoxy resin include, for example, jER 806, 807, 1750 (trade name, manufactured by Mitsubishi Chemical Corporation); Epicron 830 (trade name, manufactured by DIC Corporation); Epototo YD-170. , YD-175 (trade name, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.); Bakerite EPR169 (trade name, manufactured by Bakerite AG); GY281, GY282, GY285 (trade name, manufactured by Huntsman Advanced Materials), etc. Can be mentioned.

Examples of commercially available products of trifunctional or higher functional epoxy resins include those shown below. Examples of commercially available products of the naphthalene type epoxy resin include HP-4032 and HP-4700 (both trade names, manufactured by DIC Corporation); NC-7300 (trade name, manufactured by Nippon Kayaku Co., Ltd.) and the like.

Examples of the thermoplastic resin include polyamide, polyester, polycarbonate, polyether sulfone, polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyether ketone, polyetherimide, polyimide, polytetrafluoroethylene, polyether, polyolefin, and liquid crystal. Polymer, polyallylate, polysulphon, polyacrylonitrile styrene, polystyrene, polyacrylonitrile, polymethylmethacrylate, acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-ethylene-propylene-diene-styrene copolymer (AES resin) , Acrylonitrile-styrene-alkyl (meth) acrylate copolymer (ASA resin), polyvinyl chloride, polyvinyl formal, phenoxy resin, block polymer and the like, but are not limited thereto.
One of these thermoplastic resins may be used alone, or two or more thereof may be used in combination.

Among the above thermoplastic resins, phenoxy resin, polyether sulfone, polyetherimide, polyvinyl formal, and block polymer are preferable from the viewpoint of excellent resin flow controllability and the like. In particular, if a phenoxy resin, a polyether sulfone, or a polyetherimide is used, the heat resistance and flame retardancy of the cured resin product are further enhanced. When polyvinyl formal is used, the tack of the obtained prepreg can be easily controlled within an appropriate range without impairing the heat resistance of the cured resin product. In addition, the adhesiveness between the reinforcing fiber and the cured resin product is further enhanced. When a block polymer is used, the toughness and impact resistance of the cured resin product are improved.

Examples of commercially available phenoxy resins include YP-50, YP-50S, YP70, ZX-1356-2, FX-316 (all trade names, manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.), and the like. Not limited.
Examples of commercially available polyvinyl formal products include K (average molecular weight: 59,000), L (average molecular weight: 66,000), H (average molecular weight: 73,000), and E (average molecular weight) of Vinilec (registered trademark). : 126,000) (both are trade names, manufactured by JNC Corporation) and the like, but are not limited thereto.

When the cured resin product is required to have heat resistance exceeding 180 ° C., a polyether sulfone or a polyetherimide is preferably used as the thermoplastic resin.
Examples of commercially available products of polyether sulfone include Sumika Excel (registered trademark) 3600P (average molecular weight: 16,400), 5003P (average molecular weight: 30,000), 5200P (average molecular weight: 35,000), and 7600P (average molecular weight: 35,000). Average molecular weight: 45,300) (both trade names, manufactured by Sumitomo Chemical Co., Ltd.) and the like.
Examples of commercially available polyetherimide products include ULTEM (registered trademark) 1000 (average molecular weight: 32,000), 1010 (average molecular weight: 32,000), and 1040 (average molecular weight: 20,000) (all of which are commercial products. Name, SABIC Innovative Plastics Japan GK), etc.), but are not limited to these.

Commercially available block polymers include, for example, Nanostrength® M52, M52N, M22, M22N, 123, 250, 012, E20, E40 (trade names, all manufactured by ARKEMA), TPAE-8, TPAE-. 10, TPAE-12, TPAE-23, TPAE-31, TPAE-38, TPAE-63, TPAE-100, PA-260 (all trade names, manufactured by T & K TOKA Co., Ltd.), etc., but are limited to these. Not done.

Examples of the additive include an epoxy resin curing accelerator, an inorganic filler, an internal mold release agent, an organic pigment, an inorganic pigment and the like.

(Manufacturing method of epoxy resin composition)
The epoxy resin composition can be obtained, for example, by mixing the above-mentioned components.
Examples of the mixing method of each component include a method using a mixer such as a three-roll mill, a planetary mixer, a kneader, a homogenizer, and a homodisper.
The epoxy resin composition can be used for producing a prepreg by impregnating an aggregate of reinforcing fibers, for example, as described later. In addition, a film of the epoxy resin composition can be obtained by applying the epoxy resin composition to a release paper or the like and curing it.

<Effect>
The epoxy resin composition thus obtained can be cured in a short time even at a low temperature. In one aspect of the invention, "low temperature" means a temperature of 100-140 ° C. Further, "short time" means 10 to 30 minutes.
The viscosity of the epoxy resin composition at 30 ° C. is preferably 100 to 1,000,000 Pa · s, and the tack adjustment and workability of the prepreg surface are excellent.
Further, the cured product (cured resin product) of the epoxy resin composition is excellent in mechanical properties such as bending strength, flexural modulus, and breaking strain, and heat resistance. For example, it is preferable that the cured product of the epoxy resin composition obtained by curing at 140 ° C. for 30 minutes has a bending strength of 155 MPa or more and a flexural modulus of 3.3 GPa or more. Further, the glass transition temperature, which is an index of the heat resistance of the cured product of the epoxy resin composition obtained under the same conditions, is preferably 125 ° C. or higher. Further, the rubber-like flat region storage elastic modulus in the dynamic viscoelasticity evaluation is preferably 10 MPa or less.

By setting the elastic modulus stored in the rubber-like flat region in the dynamic viscoelasticity evaluation of the cured product of the epoxy resin composition of the present invention to 10 MPa or less, a fiber composite material having excellent fracture strain can be obtained. Here, the rubber-like flat region storage elastic modulus is an index that correlates with the crosslink density. Generally, the lower the crosslink density, the lower the elastic modulus stored in the rubber-like flat region, and the lower the crosslink density, the higher the fracture strain of the cured product of the epoxy resin.

<Reinforcing fiber>
The reinforcing fiber exists as a reinforcing fiber base material (aggregate of reinforcing fibers) in the prepreg, and is preferably in the form of a sheet.
The reinforcing fibers may be those in which the reinforcing fibers are arranged in a single direction, or may be those in which the reinforcing fibers are arranged in a random direction.
Examples of the form of the reinforcing fibers include a woven fabric of reinforcing fibers, a non-woven fabric of reinforcing fibers, and a sheet in which long fibers of reinforcing fibers are aligned in one direction. The reinforcing fiber is a sheet composed of a bundle of reinforcing fibers in which long fibers are aligned in a single direction from the viewpoint that a fiber-reinforced composite material having high specific bending strength and specific elastic modulus can be formed. From the viewpoint of being preferable and easy to handle, a woven fabric of reinforcing fibers is preferable.

Examples of the material of the reinforcing fiber include glass fiber, carbon fiber (including graphite fiber), aramid fiber, and boron fiber.
From the viewpoint of mechanical properties and weight reduction of fiber reinforced plastic, carbon fiber is preferable as the reinforcing fiber. That is, the reinforcing fiber is preferably a reinforcing fiber base material containing carbon fiber.

The fiber diameter of the carbon fiber is preferably 3 to 12 μm.
If the fiber diameter of the carbon fibers is equal to or greater than the above lower limit, the carbon fibers may move laterally and rub against each other in a process for processing the carbon fibers, for example, a comb, a roll, or the like, or the carbon fibers may rub against each other. When the surface of the roll is rubbed against the surface of the roll, the carbon fibers are less likely to be cut or fluff is less likely to occur. Therefore, a fiber-reinforced composite material having stable bending strength can be suitably produced. When the fiber diameter of the carbon fiber is equal to or less than the above upper limit value, the carbon fiber can be produced by a usual method.
The number of carbon fibers in the carbon fiber bundle is preferably 1,000 to 70,000.

From the viewpoint of the rigidity of the fiber reinforced plastic, the strand tensile bending strength of the carbon fiber is preferably 1.5 to 9 GPa, and the strand tensile elastic modulus of the carbon fiber is preferably 150 to 260 GPa.
The strand tensile bending strength and the strand tensile modulus of carbon fibers are values measured in accordance with JIS R 7601: 1986.

<Manufacturing method of prepreg>
The prepreg can be obtained, for example, by impregnating an aggregate of reinforcing fibers with the above-mentioned epoxy resin composition. The prepreg thus obtained is an aggregate of reinforcing fibers impregnated with an epoxy resin composition.
As a method of impregnating the aggregate of the reinforcing fibers with the epoxy resin composition, for example, a wet method in which the epoxy resin composition is dissolved in a solvent such as methyl ethyl ketone or methanol to reduce the viscosity and then impregnated with the aggregate of the reinforcing fibers; Examples thereof include, but are not limited to, a hot melt method (dry method) in which the epoxy resin composition is reduced in viscosity by heating and then impregnated with an aggregate of reinforcing fibers.

The wet method is a method in which an aggregate of reinforcing fibers is immersed in a solution of an epoxy resin composition, pulled up, and the solvent is evaporated using an oven or the like.
The hot melt method includes a method of directly impregnating an aggregate of reinforcing fibers with an epoxy resin composition whose viscosity has been reduced by heating, and a method of once applying the epoxy resin composition to the surface of a base material such as a release paper to form a film. There is a method in which the film is laminated from both sides or one side of the reinforcing fiber aggregate, and the reinforcing fiber aggregate is impregnated with the resin by heating and pressurizing. The coating layer obtained by coating on the surface of a base material such as a release paper may be used in the hot melt method as it is uncured, or may be used in the hot melt method after the coating layer is cured.
According to the hot melt method, there is virtually no solvent remaining in the prepreg, which is preferable.

The content of the epoxy resin composition in the prepreg (hereinafter, also referred to as “resin content”) with respect to the total mass (100% by mass) of the prepreg is preferably 15 to 50% by mass, more preferably 20 to 45% by mass. 25-40% by mass is more preferable.
When the resin content is at least the lower limit value, the adhesiveness between the reinforcing fiber and the epoxy resin composition can be sufficiently ensured. When the resin content is not more than the upper limit value, the mechanical properties of the fiber reinforced plastic are further enhanced.

<Effect>
The prepreg of the present invention described above includes the above-mentioned epoxy resin composition and reinforcing fibers. The epoxy resin composition contained in the prepreg of the present invention can prevent a decrease in the glass transition temperature and a decrease in the curing rate.
Therefore, the prepreg of the present invention can be cured in a short time even at a low temperature, and a fiber reinforced plastic having excellent mechanical properties such as bending strength, flexural modulus, and breaking strain and heat resistance can be obtained.
Further, by using the prepreg of the present invention, the processing time can be shortened in the molding of the fiber reinforced plastic, so that the fiber reinforced plastic can be manufactured at low cost.
Moreover, since the epoxy resin composition contained in the prepreg of the present invention has a controlled viscosity at 30 ° C., it is excellent in adjusting the tack on the surface of the prepreg and in workability.

[Fiber reinforced plastic]
The fiber-reinforced plastic of the present invention is a cured product of a laminated body in which two or more of the above-mentioned prepregs of the present invention are laminated. That is, the fiber-reinforced plastic of the present invention contains a cured product of the epoxy resin composition contained in the prepreg and the reinforcing fibers.
The fiber-reinforced plastic can be obtained, for example, by laminating two or more prepregs of the present invention and then molding the epoxy resin composition by heating while applying pressure to the obtained laminate.

Examples of the method for molding the fiber-reinforced plastic of the present invention include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, a sheet wrap molding method, and an epoxy resin composition for filaments and preforms of reinforcing fibers. RTM (Resin Transfer Molding), VaRTM (Vacum assisted Resin Transfer Molding: vacuum resin impregnation manufacturing method), filament winding, RFI (Resin Film Information), etc., which are impregnated with and cured to obtain a molded product, and the like. It is not limited to the method.

The lapping tape method is a method of winding a prepreg around a core metal such as a mandrel to form a tubular fiber reinforced plastic (fiber reinforced composite resin tubular body), and is used when producing a rod-shaped body such as a golf shaft or a fishing rod. It is preferably used. More specifically, the prepreg is wound around the mandrel, a wrapping tape made of a thermoplastic film is wound on the outside of the prepreg to fix the prepreg and apply pressure, and the epoxy resin composition in the prepreg is heat-cured in an oven. This is a method of obtaining a fiber-reinforced composite resin tubular body by pulling out the core metal.

In the internal pressure molding method, a preform in which a prepreg is wound around an internal pressure applying body such as a tube made of a thermoplastic resin is set in a mold, and then a high pressure gas is introduced into the internal pressure applying body to apply pressure and at the same time gold is applied. This is a method of heating a mold and molding it. The heating temperature is not particularly limited, but the higher the temperature, the shorter the molding time, which is preferable. Specifically, 120 ° C. or higher is preferable, and 140 ° C. or higher is more preferable. However, if the temperature is too high, it will take a very long time to lower the temperature of the mold, or if the prepreg is set without lowering the temperature, curing will start and the epoxy resin composition will reach every corner of the final molded product. Sometimes it doesn't spread. This method is preferably used when molding a complicated shape such as a golf shaft, a bat, a racket such as tennis or badminton.

Since the fiber reinforced plastic of the present invention described above is a cured product of a laminated body in which two or more prepregs of the present invention are laminated, it has mechanical properties such as bending strength, flexural modulus, and breaking strain, and heat resistance. Excellent in sex.

The fiber reinforced plastic of the present invention is suitably used for sports applications, general industrial applications and aerospace applications. More specifically, in sports applications, it is suitably used for golf shafts, fishing rods, rackets for tennis and badminton, stick applications such as hockey, and ski pole applications. Furthermore, in general industrial applications, it is used for structural materials of moving bodies such as automobiles, ships, and railroad vehicles, drive shafts, leaf springs, wind turbine blades, pressure vessels, flywheels, paper rollers, roofing materials, cables, and repair reinforcement materials. It is preferably used.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

<Each ingredient>
(Ingredient (A))
-YD-952: Oxazolidene type epoxy resin (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name: YD-952).

(Component (B))
-CG-500: Fluorene type epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: Ogsol CG-500, epoxy equivalent: 296 g / eq).
-EG-200: Fluorene type epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: Ogsol EG-200, epoxy equivalent: 290 g / eq).
PG-100: Fluorene type epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: Ogsol PG-100, epoxy equivalent: 260 g / eq).

(Component (C))
-YH-513: Triglycidyl-m-aminophenol (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name: YH-513)
-YH-523: Triglycidyl-p-aminophenol (manufactured by Nittetsu Chemical & Materials Co., Ltd., trade name: YH-523)
(Component (D))
1400F: dicyandiamide (manufactured by Evonik Japan Co., Ltd., product name: DICYANEX1400F).

(Other ingredients)
-JER807: Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: jER807).
-Novolak type epoxy resin (manufactured by DIC Corporation, product name: N775)
EG-280: Fluorene type epoxy resin (manufactured by Osaka Gas Chemical Co., Ltd., trade name: Ogsol EG-280, epoxy equivalent: 494 g / eq).
-Omicure 94: 3-Phenyl-1,1-dimethylurea (manufactured by PIT Japan Co., Ltd., trade name: Omicure 94).

[Examples 1 to 12, Comparative Examples 1 to 2]
<Manufacturing of cured resin plate>
The epoxy resin composition was prepared as follows according to the formulation shown in Table-1.
First, components other than the component (D) and the curing agent were weighed in a glass flask, and heated and mixed at 120 ° C. to obtain a uniform epoxy resin main agent.
After cooling the obtained epoxy resin main agent to 60 ° C. or lower, the component (D) and the curing agent were weighed and added, and heated and mixed at 60 ° C. to uniformly disperse the epoxy resin composition.
Then, the obtained epoxy resin composition was cast by sandwiching it with a glass plate together with a 2 mm thick Teflon (registered trademark; the same applies hereinafter) spacer, and heat-cured at 140 ° C. for 30 minutes to obtain a cured resin plate having a thickness of 2 mm. (Cured product of epoxy resin composition) was obtained. The obtained cured resin plate was measured and evaluated as follows.
The results are shown in the table.

(Evaluation of mechanical properties)
The cured resin plate in each example was processed into a test piece having a length of 60 mm and a width of 8 mm. The obtained test piece was subjected to a three-point bending test under the following measurement conditions, and the bending strength and flexural modulus of the cured resin plate were measured.
-Measuring equipment: manufactured by INSTRON, product name: INSTRON 5565
-Jig: Indenter R = 3.2 mm, support R = 1.6 mm, ratio of distance between supports (L) to thickness (d) of test piece (L / d) = 16
-Measurement environment: temperature 23 ° C, humidity 50% RH

(Evaluation of heat resistance)
The cured resin plate in each example was processed into a test piece having a length of 55 mm and a width of 12.5 mm. For the obtained test piece, the storage elasticity (G') is measured under the measurement conditions shown below, log G'is plotted against temperature, and the approximate straight line of the flat region of log G'and G'are transferred. The temperature at the intersection with the approximate straight line of the region was recorded as the glass transition temperature (G'-Tg). The rubber state elastic modulus is the storage elastic modulus in the region where the storage elastic modulus is flat in the temperature region higher than the glass transition temperature, and here, the storage elastic modulus at a temperature 40 ° C. above the glass transition temperature. And said.
-Measuring equipment: manufactured by TA Instruments Japan Co., Ltd., product name: RES-RDA
・ Frequency: 1Hz
・ Temperature rise rate 5 ℃ / min

The cured resin plates obtained from the cured products of the epoxy resin compositions obtained in Examples 1 to 12 had a bending strength of 155 MPa or more and a flexural modulus of 3.3 GPa or more, and were excellent in mechanical properties. Further, the glass transition temperature was 125 ° C. or higher and the heat resistance was excellent, and the elastic modulus in the rubber state in the dynamic viscoelasticity evaluation was 10 MPa or less and the breaking strain was also excellent. If the prepreg contains the obtained epoxy resin composition, curing can be completed in a short time even at a low temperature, and a fiber-reinforced plastic having excellent mechanical properties such as bending strength and flexural modulus, heat resistance, and breaking strain can be obtained. It has been shown.

On the other hand, the epoxy resin composition of Comparative Example 1 had low bending strength and flexural modulus of the cured product (cured resin plate), and was inferior in mechanical properties. When the equivalent of epoxy etc. is less than the lower limit, it is presumed that the bending strength and flexural modulus decrease.
The epoxy resin composition of Comparative Example 2 containing no component (A) was inferior in breaking strain of the cured product of the epoxy resin composition.

According to the prepreg of the present invention, curing is completed in a short time even at a low temperature, and a fiber reinforced plastic having excellent mechanical properties such as bending strength, flexural modulus, and breaking strain and heat resistance can be obtained. Therefore, according to the present invention, a wide range of molded bodies having high productivity, high efficiency, and excellent mechanical properties, for example, molded bodies for sports / leisure use such as shafts for golf clubs to molded bodies for industrial use such as aircraft are provided. can do.

Claims (7)

An epoxy resin composition containing at least the following components (A) and (D), and the cured product obtained by curing the epoxy resin composition at 140 ° C. for 30 minutes has a bending strength of 155 MPa or more and a flexural modulus of 3.3 GPa or more. An epoxy resin composition having a glass transition temperature of 125 ° C. or higher and a rubber state elastic modulus of 10 MPa or lower in a dynamic viscoelasticity evaluation.
Component (A): Fluorene type epoxy resin component (D): Hardener The epoxy resin composition according to claim 1, wherein the epoxy resin composition contains a component (B) and a component (C).
Component (B): Oxazoridone type epoxy resin Component (C): Triglycidyl aminophenol type epoxy resin The epoxy resin composition according to claim 1 or 2, wherein the epoxy equivalent of the component (A) is 200 to 350. The epoxy resin composition according to any one of claims 1 to 3, wherein the component (D) is an amine-type curing agent. The prepreg according to any one of claims 1 to 4, wherein the reinforcing fiber is carbon fiber. A fiber-reinforced plastic which is a cured product of a laminated body in which two or more prepregs according to claim 5 are laminated. An epoxy resin composition containing the following components (A) to (D).
Component (A): Fluorene type epoxy resin component (B): Oxazolidene type epoxy resin component (C): Triglycidyl aminophenol type epoxy resin component (D): Curing agent