Abstract: In order to satisfy the requirements for satisfactory levels of melting•burn-off characteristics in response to heat application, high temperature burn-off characteristics and ease of residual ash removal that a resin model should assure as an alternative to a wax model, the burn-off resin model according to the present invention, which can be used in the lost wax process, is manufactured by forming a liquid resin compound containing 1 to 30 wt. % of a plasticizer (D) and 1 to 20 wt. % of a wax component (E) blended into a double fluid reactive setting liquid urethane resin (C) constituted of a multifunctional polyol component (A) and a multifunctional polyisocyanate component (B) and then by setting the liquid resin compound within a working life of 5 minutes or less.

Abstract: The present invention comprises a process for combining foamed polystyrene fine particles (C) to two-component reaction curing type soft urethane liquid resin (A), injecting a resulting mixture into a mold for core (C) with a concave portion corresponding to said hollow portion, hardening it, removing a resulting cured matter from said mold for core (C), and forming a vanishing core (D) having a shape corresponding to said hollow portion; a process for setting said vanishing core (D) at a specific position inside a mold for resin model (E) having a concave portion corresponding to an outer shape of said resin model, injecting two-component reaction fast curing type urethane liquid resin (F), hardening it, removing a resulting cured matter, and forming a resin model (G) including said vanishing core (D); and a process for injecting organic solvent capable of dissolving foamed polystyrene (H) into said vanishing core (D of said resin model (G) to dissolve said foamed polystyrene fine particles (B), removing a r