Abstract: This invention provides reaction resin molded materials (OX/ICR molded materials) containing oxazolidinone and isocyanurate rings prepared from reaction resin mixtures of polyepoxides and polyisocyanates (EP/IC resins) in the presence of a hardening catalyst and has as an object to provide a simple manufacturing method for heat resistant OX/ICR molded materials with improved mechanical properties. According to this invention, EP/IC resins which are capable of casting and impregnating and which are free from solvents are provided. These resins have a formula mole ratio of EP:IC of about 1 to 5 and a viscosity of up to 7,000 mPa sec at 25.degree. C. and are cross-linked by means of tertiary amine or imidazole hardening catalysts at gelling temperatures of up to 130.degree. C. and post-hardening temperatures of 130.degree. to 200.degree. C. to produce OX/ICR molded materials with a mole ratio OX:ICR greater than 1, wherein the reaction of the epoxy and isocyanate groups is above 90% after the hardening.