JP2012144672A - Epoxy resin composition, prepreg and fiber-reinforced composite material - Google Patents

Abstract

【選択図】なしAn epoxy resin composition capable of improving excellent flame retardancy and heat resistance is provided.
An epoxy resin (A), a phosphazene compound (B) having a structure represented by formula (1), an aromatic phosphorus compound (C) having a structure represented by formula (2), and an epoxy resin curing agent (D). An epoxy resin composition in which the mass ratio (B) / (C) of the phosphazene compound (B) component and the aromatic phosphorus compound (C) component is 0.1 to 9.0.

[Selection figure] None

Description

  The present invention relates to an epoxy resin composition having excellent flame retardancy, and a prepreg and a fiber-reinforced composite material using the epoxy resin composition.

  A fiber-reinforced composite material (hereinafter referred to as FRP) reinforced with reinforcing fibers has excellent specific strength, specific rigidity, and the like, and has characteristics that are lightweight. Widely used in sports applications such as materials, automotive parts, rackets and golf shafts.

  In particular, in recent years, there has been an increasing demand for flame retardancy and low smoke generation during combustion, particularly in applications such as electronic materials, automobile parts, railway vehicles, and aircraft. However, the conventional FRP using the epoxy resin composition has no flame retardancy and has a problem in smoke generation during combustion.

  Various flame retardant methods for FRP have been studied so far, and brominated epoxy resins have been widely adopted because of their high flame retardancy. However, although brominated epoxy resins have high flame retardancy, toxicity of halogen-based gas generated at the time of fire becomes a problem, and alternative methods have been desired from the viewpoint of safety to human bodies and protection of the global environment.

Therefore, a method of adding red phosphorus or a phosphoric acid ester compound to an epoxy resin (Patent Document 1) has become the mainstream as a flame retardant method replacing the brominated epoxy resin. However, depending on the amount of addition, etc., these methods are 1) decrease in mechanical strength, 2) poor storage stability, 3) gradual leaching of phosphorus compounds over a long period of time, 4) easy hydrolysis Therefore, problems such as difficulty in adoption in printed wiring boards and electronic materials that require high insulation and water resistance remain.
Moreover, when a phosphoric acid ester compound is used, there exists a problem that the heat resistance of a resin composition falls.

International Publication No. 2005/082982 Pamphlet

  The present invention has been made in view of the above circumstances, and can achieve excellent flame retardancy without containing a halogen-based flame retardant, red phosphorus, and phosphate ester, and can improve heat resistance. It is an object of the present invention to provide an epoxy resin composition that can be used, and a prepreg and a fiber-reinforced composite material using the epoxy resin composition.

  As a result of intensive studies, the present inventors have used a phosphazene compound (B) represented by the following formula (1) and a cyclic phosphorus compound (C) represented by the following formula (2) in combination, and the component (B) and ( It was found that the flame retardancy synergistic effect of component C) can achieve excellent flame retardancy of the epoxy resin composition and can improve heat resistance.

The present invention has the following aspects.
[1] An epoxy resin (A), a phosphazene compound (B) having a structure represented by formula (1), an aromatic phosphorus compound (C) having a structure represented by formula (2), and an epoxy resin curing agent (D) An epoxy resin composition comprising a phosphazene compound (B) component and an aromatic phosphorus compound (C) component having a mass ratio (B) / (C) of 0.1 to 9.0.

[In formula, R < ₁ > and R < ₂ > may be the same or different, C1-C18 alkyl group, C5-C8 cycloalkyl group, C6-C14 aryl group, C7-C7 18 alkylaryl groups, alkenyl groups having 2 to 18 carbon atoms, alkenyl aryl groups having 8 to 18 carbon atoms, amino group-substituted phenyl groups, aminoalkyl group-substituted phenyl groups (the number of carbon atoms of the aminoalkyl group as a substituent is 1 Or 6), a hydroxy group-substituted phenyl group, or a hydroxyalkyl group-substituted phenyl group (the hydroxyalkyl group as the substituent has 1 to 6 carbon atoms). n represents an integer of 3 to 10,000. ]

[Wherein, R ₃ represents a hydroxy substituted aryl group having 6 to 20 carbon atoms, a hydroxy substituted alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or 7 carbon atoms. A -21-substituted cyano-substituted aryl group, a C1-C18 cyano-substituted alkyl group, a hydrogen atom, or a hydroxy group. ]

[2] A prepreg obtained by impregnating the reinforcing resin with the epoxy resin composition of [1].
[3] A fiber-reinforced composite material obtained by curing the prepreg of [2].
[4] The fiber-reinforced composite material according to [3], which has a flame retardancy of UL-94V and V-0 when formed into a 0.6 mm-thick molded plate.

Although the epoxy resin composition of the present invention does not contain a halogen-based flame retardant, red phosphorus, or phosphate ester, the cured product can achieve excellent flame retardancy and is also heat resistant. Can be improved.
In the prepreg of the present invention, the cured product achieves excellent flame retardancy even though the epoxy resin composition constituting the prepreg does not contain a halogen flame retardant, red phosphorus, or phosphate ester. In addition, the heat resistance can be improved.
The fiber-reinforced composite material of the present invention can achieve excellent flame retardancy and can also improve heat resistance.

<Epoxy resin (A)>
As the epoxy resin (A), bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, alicyclic epoxy resin, epoxy resin having biphenyl skeleton, phenol novolac type epoxy resin , Cresol novolac type epoxy resin, resorcinol type epoxy resin, polyethylene glycol type epoxy resin, polypropylene glycol type epoxy resin, epoxy resin having naphthalene skeleton, trisphenylmethane type epoxy resin, phenol aralkyl type epoxy resin, aminoglycidyl type epoxy resin, An aminophenol-type epoxy resin, aminocresol-type epoxy resin, dicyclopentadiene-type epoxy resin, and phenols as precursors One or more selected the carboxy resin from the group consisting of modified epoxy resin with urethane or isocyanate is used.
Among these, 1 selected from the group consisting of bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, and trisphenylmethane type epoxy resin in terms of handling properties such as mechanical properties, heat resistance and viscosity. Species or two or more are preferred. In particular, a phenol novolac type epoxy resin is preferable because excellent flame retardancy is easily obtained.
The epoxy resin composition of this embodiment preferably has a viscosity at 30 ° C. of 10 ³ to 10 ⁶ Pa · s and a viscosity at 70 ° C. of 10 ⁰ to 10 ³ Pa · s for convenience of handling.

<Phosphazene Compound (B)>
The phosphazene compound (B) is not particularly limited as long as it is a compound having a structural unit represented by the formula (1) (including cyclic phosphazene compounds).
In Formula (1), preferable R ₁ and R ₂ are an aryl group having 6 to 8 carbon atoms and an alkyl group having 1 to 3 carbon atoms. n is preferably from 3 to 20, and more preferably from 3 to 8.
From the viewpoint of availability, a cyclic phosphazene compound in which R ₁ and R ₂ are phenyl groups and n = 3 is more preferable.

<Aromatic phosphorus compound (C)>
The aromatic phosphorus compound (C) is not particularly limited as long as it is a compound represented by the formula (2).
In the formula (2), R ₃ is preferably a hydroxy-substituted phenyl group from the viewpoint of flame retardancy and storage stability.
The compound represented by Formula (2) can be obtained from a commercial item. Examples thereof include HCA-HQ, BCA, and HCA (all are product names) manufactured by Sanko Co., Ltd.

<Content ratio>
The phosphorus content of the epoxy resin composition is preferably 0.5 to 3.0% by mass. When the phosphorus content is 0.5% by mass or more, a sufficient flame retardancy improvement effect is easily obtained, and when it is 3% by mass or less, problems such as a decrease in mechanical strength and poor storage stability are unlikely to occur. . A more preferable range of the phosphorus content is 0.9 to 2.9% by mass.
The total amount of the phosphazene compound (B) and the aromatic phosphorus compound (C) added to the epoxy resin composition may be set so that the total content of phosphorus derived therefrom is within the above range. preferable.
The mass ratio (B) / (C) of the phosphazene compound (B) and the aromatic phosphorus compound (C) is 0.1 to 9.0. Within this range, the synergistic effect of the B component and the C component can be effectively obtained, and the amount of flame retardant added to impart flame retardancy can be reduced. In terms of increasing the flame retardancy of the cured product of the epoxy resin composition, the content ratio of the phosphazene compound (B) is preferably larger within the above range, and the Tg of the cured product of the epoxy resin composition is increased. In terms of improving heat resistance, it is preferable that the content of the aromatic phosphorus compound (C) is large within the above range.

<Curing agent for epoxy resin (D)>
Examples of the epoxy resin curing agent (D) include amines, acid anhydrides (such as carboxylic acid anhydrides), phenols (such as novolak resins), mercaptans, Lewis acid amine complexes, onium salts, imidazoles, and the like. Any structure can be used as long as it can be cured. Among these, amine type curing agents are preferable.
These curing agents may be used alone or in combination of two or more.

  Examples of amine-type curing agents include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, imidazole derivatives, dicyandiamide, tetramethylguanidine, thiourea-added amines, and isomers and modified products thereof. Can be mentioned. Among these, dicyandiamide is particularly preferable in terms of excellent prepreg storage.

  The compounding amount of the epoxy resin curing agent (D) is preferably such that the ratio of the active hydrogen equivalent of the epoxy resin curing agent (D) to the epoxy equivalent of the epoxy resin (A) is 0.5 to 1. The ratio is more preferably 0.6 to 0.8. By setting it to 0.5 or more, sufficient curing can be achieved. By setting it to 1 or less, the toughness of the cured product can be increased.

<Curing accelerator>
If necessary, a curing accelerator can be contained in the epoxy resin composition.
The curing accelerator is not particularly limited as long as it has an effect of promoting the curing reaction by the epoxy resin curing agent (D) to be used.
For example, when the epoxy resin curing agent (D) is dicyandiamide, 3-phenyl-1,1-dimethylurea, 3- (3,4-dichlorophenyl) -1,1-dimethylurea (DCMU), 3- (3 Urea derivatives such as -chloro-4-methylphenyl) -1,1-dimethylurea and 2,4-bis (3,3-dimethylureido) toluene are preferred. Further, when the epoxy resin curing agent (D) is a carboxylic acid anhydride or a novolac resin, a tertiary amine is preferred. Moreover, when the epoxy resin curing agent (D) is diaminodiphenylsulfone, urea compounds such as imidazole compounds and phenyldimethylurea (PDMU), and amine complexes such as monoethylamine trifluoride and amine trichloride are preferable. Among these, a combination of dicyandiamide and DCMU is particularly preferable.

<Thermoplastic resin>
The epoxy resin composition of this embodiment may contain a thermoplastic resin as long as it does not impair the effects of the present invention.
The type of thermoplastic resin is not particularly limited. For example, phenoxy resin, polyamide, polyester, polycarbonate, polyether sulfone, polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyimide, polytetrafluoroethylene, poly Examples include ether, polyolefin, liquid crystal polymer, polyarylate, polysulfone, polyacrylonitrile styrene, polystyrene, polyacrylonitrile, polymethyl methacrylate, ABS, AES, ASA, and polyvinyl formal.
Among these, a phenoxy resin is preferable in terms of flame retardancy and solubility in an epoxy resin.

<Additives>
The epoxy resin composition of this embodiment may contain various known additives as long as it does not impair the effects of the present invention. Examples of the additive include silicone oils, natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters, paraffins and other mold release agents, crystalline silica, fused silica, calcium silicate. Further, powders such as alumina, calcium carbonate, talc and barium sulfate, inorganic fillers such as glass fibers and carbon fibers, colorants such as carbon black and bengara, silane coupling agents and the like can be used.

≪Method for preparing epoxy resin composition≫
The epoxy resin composition of this embodiment can be prepared by mixing each component. Examples of the method for mixing the components include a method using a mixer such as a three-roll mill, a planetary mixer, a kneader, a universal agitator, a homogenizer, or a homodisper.

≪Prepreg≫
The epoxy resin composition of this embodiment can be used as a prepreg by impregnating reinforcing fibers.
As the reinforcing fiber, various inorganic fibers or organic fibers such as carbon fiber, aramid fiber, nylon fiber, high-strength polyester fiber, glass fiber, boron fiber, alumina fiber, and silicon nitride fiber can be used. Among these, carbon fiber, aramid fiber, glass fiber, boron fiber, alumina fiber, and silicon nitride fiber are preferable from the viewpoint of flame retardancy, and carbon fiber is particularly preferable from the viewpoint of excellent specific strength and specific elasticity.
The form of the reinforcing fiber may be aligned in one direction, or may be a woven fabric or a non-crimp fabric.
The prepreg can be produced by a known method using the epoxy resin composition of the present embodiment and the reinforcing fiber.

≪Fiber reinforced composite material≫
The fiber reinforced composite material is obtained by curing the prepreg.
In the present invention, the fiber reinforced composite material is preferably a carbon fiber reinforced composite material containing carbon fibers as reinforcing fibers.
The carbon fiber reinforced composite material is excellent in flame retardancy and heat resistance. Regarding the flame retardancy, for example, the flame retardancy when the phosphorous content of the entire epoxy resin composition is 3% by mass or less and a 0.6 mm thick fiber reinforced composite material molded plate is UL-94V and V-0. Can be achieved. With respect to heat resistance, for example, the phosphorus content of the entire epoxy resin composition can be 3 mass% or less, and the Tg of the cured product of the resin composition can be 105 ° C or higher, more preferably 110 ° C or higher. is there.

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples.
The raw materials (resins etc.), carbon fibers, and evaluation methods used in the following examples are shown below.
<Raw material>
Epoxy resin A-1: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER828, epoxy equivalent 189 g / eq, viscosity (25 ° C.): 15 Pa · S, viscosity (75 ° C.): 16 mPa · S)
Epoxy resin A-2: bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER1001, epoxy equivalent 475 g / eq, viscosity (75 ° C.): 200 Pa · S)
Epoxy resin A-3: Bisphenol F type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER807, epoxy equivalent 168 g / eq, viscosity (25 ° C.): 4 Pa · S, viscosity (75 ° C.): 6 mPa · S)
Epoxy resin A-4: Phenol novolac type epoxy resin (manufactured by Nippon Steel Chemical Co., Ltd., product name: YDPN-638, epoxy equivalent 180 g / eq, viscosity (75 ° C.): 5.5 Pa · S)

Phosphazene compound B-1: Cyclic phenoxyphosphazene (Fushimi Pharmaceutical Co., Ltd., product name: Ravitor FP-110, a compound in which R ₁ and R ₂ are phenyl groups and n = 3 in the above formula (1), Phosphorus content 13.4% by mass)
Aromatic phosphorus compound C-1: 10- (2,5-dihydroxyphenyl) -10H-9-oxo-10-phosphaphenanthrene-10-oxide (product name: HCA-HQ, manufactured by Sanko Co., Ltd.) Compound represented by formula (3), phosphorus content 9.5% by mass)

Condensed phosphate ester 1 (comparative example): 1,3-phenylene bizdixylenyl phosphate (manufactured by ADEKA, product name: ADK STAB FP-500, phosphorus content 9.0 mass%
-Thermoplastic resin 1: Phenoxy resin (manufactured by Nippon Steel Chemical Co., Ltd., product name: YP-50S)
Curing agent D-1: Dicyandiamide (Mitsubishi Chemical Corporation, product name: DICY15)
Curing accelerator 1: 3- (3,4-dichlorophenyl) -1,1-dimethylurea (Hodogaya Chemical Co., Ltd., product name: DCMU99)
<Carbon fiber>
Carbon fiber 1: TR50S 15L (Product name, manufactured by Mitsubishi Rayon Co., Ltd., basis weight: 1 g / m)

<Evaluation method>
(1) UL-94V combustion test (resin plate):
A resin plate having a thickness of 2 mm was processed into a test piece (length 127 mm × width 12.7 mm), and a combustion test was performed according to the UL-94V standard using a combustion tester manufactured by Suga Test Instruments. That is, the test piece was attached to the clamp vertically, an indirect flame with a 20 mm flame was performed for 10 seconds, and the combustion time was measured. A burn test was performed on five specimens, and the number of samples burned to the clamp, the maximum value of each burn time, and the sum of the five burn times (total burn time) were recorded. Moreover, determination [V-0, V-1, V-2, fail] was performed based on the result. As for flame retardancy, V-0 is most excellent, and V-1, V-2 and fail are in that order.

(2) UL-94V combustion test (carbon fiber composite material plate):
In the UL-94V combustion test (resin plate) of the above (1), the test piece is obtained by curing a carbon fiber prepreg having a fiber basis weight of 210 g / m ² and a resin content of 33% by mass. Evaluation was performed in the same manner as in the above (1) except that the carbon fiber composite material plate ([0 ° / 90 °] s) having a thickness of 8 mm was used.
(3) Measurement of Tg Q1000 manufactured by TA Instruments was used as a measuring instrument.
Regarding the cured product of the resin composition, the sample was pulverized, 5 mg was weighed, and DSC-Tg was measured according to JISK7121. The curing conditions for the resin composition were 130 ° C. × 2 hours, and the heating rate was 2 ° C./min.
(4) Viscosity measurement The viscosity at 30 ° C. and the viscosity at 70 ° C. of the epoxy resin composition (measuring device: AR-G2 (product name) manufactured by TA Instruments Co., Ltd.), measurement conditions: using a 25 mmφ parallel plate The measurement was performed at a plate gap of 500 nm, a temperature increase rate of 2 ° C./min, a temperature increase of 10 rad / sec, and a stress of 300 Pa).

<Method for preparing epoxy resin composition>
A curing agent master batch 1 having the composition shown in Table 1 and epoxy resin master batches 1 and 2 having the compositions shown in Tables 2 and 3 were prepared in advance, and these were mixed to prepare an epoxy resin composition.
[Preparation of curing agent master batch 1]
In the composition shown in Table 1, epoxy resin A-1, curing agent D-1, and curing accelerator 1 were weighed and mixed in a container. Furthermore, it further mixed finely with a three roll mill, and the hardening | curing agent masterbatch 1 was obtained.

[Preparation of epoxy resin master batches 1 and 2]
Epoxy resin A and thermoplastic resin 1 having the compositions shown in Tables 2 and 3 were weighed into a glass flask and then stirred and mixed in an oil bath heated to 170 ° C. for 3 hours to obtain epoxy resin master batches 1 and 2, respectively. It was.

<Examples 1 to 5 and Comparative Examples 1 and 2>
Each raw material was weighed into a glass flask so as to have the composition shown in Table 4, and then stirred and mixed in a water bath heated to 65 ° C. to obtain an epoxy resin composition. The ratio of the active hydrogen equivalent of the curing agent D-1 to the total epoxy equivalent of the epoxy resins A-1 to A-3 is 0.63.
Tg of the cured epoxy resin compositions obtained in Examples 4 and 5 and Comparative Example 2 was measured. The results are shown in Table 4.

The epoxy resin compositions obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were injected between two glass plates sandwiching a 2 mm-thick polytetrafluoroethylene spacer, 130 ° C. × 2 hours, heating rate 2 Heat curing was performed under curing conditions of ° C./min to obtain a resin plate. The obtained resin plate was subjected to a flame retardant combustion test according to UL-94. The results are shown in Table 4.
The obtained epoxy resin composition was made into a film with a comma coater manufactured by Hirano Techseed Co., Ltd., product name: M-500, to prepare a 52 g / m ² resin film. Using this resin film and the carbon fiber 1, a carbon fiber prepreg having a fiber basis weight of 210 g / m ² and a resin content of 33% by mass was obtained by a drum wind method.
The obtained carbon fiber prepreg is cut into a size of 200 mm × 200 mm, and four sheets are stacked so that the fiber direction is [0 ° / 90 °] s = 0 ° / 90 ° / 90 ° / 0 °, or 0 Three sheets are stacked so that the angle is 90 ° / 90 °, cured at 130 ° C. for 90 minutes, heated at a rate of 2 ° C./minute, and pressure of 0.6 MPa in an autoclave. Sheet laminated) or 0.6 mm (three laminated) carbon fiber composite material plates were obtained. The obtained raw fiber composite material plate was subjected to a flame retardant combustion test in accordance with UL-94. The results are shown in Table 4.

As shown in the results of Table 4, compared with Comparative Example 1 in which only the component (C) was added as a flame retardant, Example 1 using the component (B) in addition to the component (C) has flame retardancy. Improved. Compared to Comparative Example 2 in which only the component (B) was added as a flame retardant, Example 5 using the component (B) in addition to the component (C) improved the flame retardancy.
In Examples 4 and 5 in which the (B) component and the (C) component were used in combination, the Tg of the cured product was higher and the heat resistance was improved as compared with Comparative Example 2 in which only the (B) component was added. In Examples 4 and 5, Tg tends to increase as the content of component (C) increases. Therefore, although Examples 1-3 did not measure Tg, it is estimated that it is higher than 113 degreeC of Example 4. FIG.

<Examples 6 to 8>
An epoxy resin composition was obtained in the same manner as in Example 1 except that the formulation was changed as shown in Table 5. The ratio of the active hydrogen equivalent of the curing agent D-1 to the total epoxy equivalent of the epoxy resins A-1 and A-4 is 0.65.
About the epoxy resin composition of Example 6, the viscosity in 30 degreeC and 70 degreeC was measured. The results are shown in Table 5.
Tg was measured about the hardened | cured material of the epoxy resin composition obtained in Examples 6-8. The results are shown in Table 5.
The obtained epoxy resin composition was made into a film with the same comma coater as in Example 1 to produce a 53 g / m ² resin film. Using this resin film, a carbon fiber prepreg having a fiber basis weight of 215 g / m ² and a resin content of 33% was obtained in the same manner as in Example 1.
Using the obtained carbon fiber prepreg, a carbon fiber composite material plate having a thickness of 0.8 mm or 0.6 mm was obtained in the same manner as in Example 1, and a combustion test was performed. The results are shown in Table 5.

  As shown in the results of Table 5, good flame retardancy was also obtained in Examples 6 to 8 using epoxy resins A-1 and A-4.

<Comparative Example 3>
The raw materials were weighed in a glass flask with the composition shown in Table 6, and then stirred and mixed in a water bath heated to 65 ° C. to obtain an epoxy resin composition.
The obtained epoxy resin composition was molded into a 2 mm thick resin plate in the same manner as in Example 1, and a combustion test was performed. The results are shown in Table 6.
In Table 6, the results of Example 5 are also shown for comparison.

  As shown in the results of Table 6, compared to Comparative Example 3 using a condensed phosphate ester as a flame retardant, Example 5 using a component (B) instead of the condensed phosphate ester, Despite the same phosphorus content, flame retardancy was improved.

Claims (4)

A phosphazene comprising an epoxy resin (A), a phosphazene compound (B) having a structure represented by formula (1), an aromatic phosphorus compound (C) having a structure represented by formula (2), and an epoxy resin curing agent (D) The epoxy resin composition whose mass ratio (B) / (C) of a compound (B) component and an aromatic phosphorus compound (C) component is 0.1-9.0.

[In formula, R < ₁ > and R < ₂ > may be the same or different, C1-C18 alkyl group, C5-C8 cycloalkyl group, C6-C14 aryl group, C7-C7 18 alkylaryl groups, alkenyl groups having 2 to 18 carbon atoms, alkenyl aryl groups having 8 to 18 carbon atoms, amino group-substituted phenyl groups, aminoalkyl group-substituted phenyl groups (the number of carbon atoms of the aminoalkyl group as a substituent is 1 Or 6), a hydroxy group-substituted phenyl group, or a hydroxyalkyl group-substituted phenyl group (the hydroxyalkyl group as the substituent has 1 to 6 carbon atoms). n represents an integer of 3 to 10,000. ]

[Wherein, R ₃ represents a hydroxy substituted aryl group having 6 to 20 carbon atoms, a hydroxy substituted alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkyl group having 1 to 18 carbon atoms, or 7 carbon atoms. A -21-substituted cyano-substituted aryl group, a C2-C19 cyano-substituted alkyl group, a hydrogen atom, or a hydroxy group. ]   A prepreg formed by impregnating the reinforcing resin with the epoxy resin composition according to claim 1.   A fiber-reinforced composite material obtained by curing the prepreg according to claim 2.   The fiber-reinforced composite material according to claim 3, wherein the flame-retardant property is UL-94V and V-0 when a 0.6 mm-thick molded plate is formed.