METHOD OF PRODUCING MOLDS FOR LOST WAX PRECISION CASTING

摘要

The problems of the invention are to establish a modeling resin composition excellent in shape retention and dewaxing properties in the skillful system which comprises a urethane resin easy of thermal decomposition, a plasticizer, and a wax or waxy component and a dewaxing method suitable for models made from the composition and to enhance the strength of a mold in the low-temperature region wherein dewaxing is carried out. According to the invention, a mold is produced by applying a primary layer consisting of plural refractory coating layers among which epoxy-silicone layers are laid and a backup layer consisting of plural thick coating layers on the surface of a resin model made by curing a two-part curable urethane resin fluid (F) which consists of a polyfunctional polyol component (A), a polyfunctional polyisocyanate component (B), a plasticizer (C), a wax or waxy component (D), and hollow resin balloons (E), preheating the obtained composite in a low-temperature region of 60 to 120°C for 2 to 8 hours to conduct initial dewaxing of removing 5 to 50% by weight of the resin model, raising the oven temperature gradually, and conducting the heating of the resulting composite in a medium-temperature region of 150 to 500°C for 2 to 5 hours and then the firing thereof in a high-temperature region of 500 to 1000°C for 2 to 5 hours.