Method for producing fiber-reinforced composite material, and heat-resistant mold material and heat-resistant structural material using the fiber-reinforced composite material

1. A method for producing a fiber-reinforced composite material, the method comprising:

(I) impregnating a fiber substrate comprising reinforcing fibers with an epoxy resin composition, to obtain a fiber-reinforced prepreg;

(II) curing the fiber-reinforced prepreg at a primary curing temperature in a range from 110-130° C., to obtain a primary fiber-reinforced composite material; and then

(III) curing the primary fiber-reinforced composite material at a secondary curing temperature, which is at least as high as the primary curing temperature, to obtain the fiber-reinforced composite material,

wherein the epoxy resin composition comprises:

(A) a triphenylmethane epoxy resin of formula 1:

(B) an N,N,N′,N′-tetraglycidyldiaminodiphenylmethane;

(C) a diaminodiphenylsulfone in an amount such that a ratio of amine equivalents to epoxy equivalents in the epoxy resin composition is from 0.8 to 1.2; and

(D) silica in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the sum of the triphenylmethane epoxy resin of formula 1 and the N,N,N′,N′-tetraglycidyldiaminodiphenylmethane.

2. The method of claim 1 , wherein the secondary curing temperature is 180° C. or higher.

3. The method of claim 2 , wherein the secondary curing temperature is no higher than 300° C.

4. The method of claim 1 , wherein the fiber substrate comprises carbon fibers.

5. The method of claim 1 , wherein the fiber substrate is a woven fabric.

6. The method of claim 1 , wherein the fiber substrate comprises a chopped material.

7. The method of claim 1 , wherein the curing (II) is carried out in a mother die, and

the method further comprises, after the curing (II), removing the primary fiber-reinforced composite material from the mother die,

wherein the curing (III) is carried out in a free standing state, thereby obtaining the fiber-reinforced composited material in the form of a heat-resistant mold material.

8. The method of claim 1 , wherein the curing (II) is carried out in a mother die, and

the method further comprises, after the curing (II), removing the primary fiber-reinforced composite material from the mother die,

wherein the curing (III) is carried out in a free standing state, thereby obtaining the fiber-reinforced composited material in the form of a heat-resistant structural material.

9. The method of claim 1 , wherein a mass ratio of (A) and (B) in the epoxy resin composition is in a range from 90:10 to 10:90.

10. The method of claim 1 , wherein a mass ratio of (A) and (B) in the epoxy resin composition is in a range from 90:10 to 30:70.

11. The method of claim 1 , wherein a mass ratio of (A) and (B) in the epoxy resin composition is in a range from 80:20 to 10:90.

12. The method of claim 1 , wherein the diaminodiphenylsulfone (C) is a 4,4′-diaminodiphenylsulfone or a 3,3′-diaminodiphenylsulfone.

13. The method of claim 1 , wherein the primary curing temperature is in a range from 110-120° C.

14. The method of claim 1 , wherein the secondary curing temperature is 200° C. or higher.

15. The method of claim 14 , wherein the secondary curing temperature is no higher than 300° C.

16. The method of claim 1 , wherein the secondary curing temperature is no higher than 300° C.

17. The method of claim 1 , wherein the fiber substrate comprises glass fibers.

18. The method of claim 1 , wherein the fiber substrate consists of carbon fibers.

19. The method of claim 1 , wherein (A) and (B) in the epoxy resin are in a mass ratio of 90:10 to 40:60.