Abstract: The purpose of the present invention is to provide a thermosetting epoxy resin composition with ability to allow cured products to have excellent toughness and to stably maintain high stiffness. In order to achieve the purpose, the thermosetting epoxy resin composition of the present invention includes the following components [a], [b], [c], and [d], wherein the stoichiometric ratio [b]/[a] of the component [b] to the component [a] is in the range from 0.7 to 2.0 thermosetting epoxy resin composition: [a] an epoxy resin; [b] an isocyanate curing agent; [c] an elastomeric toughening agent; [d] an oxazolidone cyclization catalyst.

Abstract: The purpose of the present invention is to provide a thermosetting epoxy resin composition that is excellent in terms of both pot life and fast curability at low temperatures and also a molded article that is prepared by thermally curing the thermosetting epoxy resin composition and is excellent in terms of both wet heat resistance and toughness. In order to achieve the purpose, the thermosetting epoxy resin composition of the present invention includes the following components [a], [b], [c], and [d], wherein the stoichiometric ratio of [b] to [a] is in the range from 0.5 to 2.0: [a] an epoxy resin; [b] an isocyanate curing agent; [c] a hydroxyl group capping agent; [d] an epoxy curing catalyst.

Abstract: The purpose of the present invention is to provide: a molding material from which a carbon fiber reinforced composite material having excellent impact resistance and tensile strength is obtained; and a molding material from which a glass fiber reinforced composite material, that has high bending strength and impact resistance, has excellent weather resistance, and can suppress a decrease in bending strength after water absorption, is obtained. In order to achieve the purpose, the molding material according to the present invention is a molding material formed of an epoxy resin composition and a carbon fiber and/or a glass fiber, wherein the epoxy resin composition includes all of [A] to [C], the carbon fiber satisfies conditions [a] and [b], and the glass fiber has a surface functional group capable of forming a covalent bond with an isocyanate group.

Abstract: The present invention aims to provide an epoxy resin composition for a fiber-reinforced composite material that maintains low viscosity during injection into reinforcing fibers to realize good impregnating and also has high toughness and high heat resistance and also aims to provide a fiber-reinforced composite material produced therefrom. Also provided is a molding method for a fiber-reinforced composite material including at least a reinforcing fiber [A] and a cured product of an epoxy resin composition [B], wherein the epoxy resin composition [B] includes the components [a], [b], and [c] specified below, and the epoxy resin composition [B] is cured in such a manner that the absorbance ratio Da/(Da+Db) is in the range of 0.4 to 1 in producing the fiber-reinforced composite material: [a] an epoxy resin having at least two oxirane groups in the molecule, [b] an epoxy resin curing agent having at least two isocyanate groups in the molecule, and [c] a catalyst.