Epoxy resin composition, prepreg, and fiber-reinforced composite material

An epoxy resin composition comprising:

• at least one reactive diluent [A] having a viscosity of 2 Pas or less at 25° C. and selected from the group consisting of a reactive diluent having a structure represented by general formula (4), a reactive diluent having a structure represented by general formula (7), and a reactive diluent having a structure represented by general formula (8);
• at least one trifunctional or higher functional epoxy resin [B] selected from the group consisting of N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N′,N′-tetraglycidyl-4,4′-methylenedianiline, N,N,N′,N′-tetraglycidyl-2,2′-diethyl-4,4′-methylenedianiline and N,N,N′,N′-tetraglycidyl-m-xylylenediamine;
• at least one amine-based hardener [C] selected from the group consisting of an amine-based hardener having a structure represented by general formula (2) and an amine-based hardener having a structure represented by general formula (3);
• optionally, a non-phosphorus-containing aromatic polyamine hardener provided in an amount of up to 90 parts by mass based on 100 parts by mass total of [C] and the aromatic polyamine hardener;
• and
• at least one thermoplastic resin [D] composed of a polyaryl ether skeleton:
• wherein in the general formula (4), R3 and R4 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group;
• and X3 represents one selected from the group consisting of —O—, —S—, —CO—, —C(═O)O— and —S2−;
• wherein in the general formula (7), R7 and R8 each independently represent at least one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group, with the proviso that both of R7 and R8 are not hydrogen atoms;
• wherein in the general formula (8), R9 and R10 each independently represent a direct bond, an alkylene group with a carbon number of 1 to 8, a phenylene group or a cyclohexylene group;
• and R11 represents one selected from the group consisting of a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 4, an alicyclic hydrocarbon group with a carbon number of 3 to 6, an aromatic hydrocarbon group with a carbon number of 6 to 10, a halogen atom, an acyl group, a trifluoromethyl group and a nitro group;
• wherein in the general formula (2), R1 represents a hydrocarbon group with a carbon number of 2 to 4;
• and in the general formula (3), R2 represents a hydrogen atom or an amino group;
• wherein [A] is present in an amount of 10 to 50 parts by mass and [B] is present in an amount of 50 to 90 parts by mass, totaling 100 parts by mass;
• and
• wherein [C] is present in amount to provide a phosphorus atom content of 1.0 to 5.0% by mass, based on the overall mass of the epoxy resin composition.