RESIN COATED SAND FOR SHELL MOLD

摘要

PURPOSE:To develop resin coated sand for a shell mold having excellent sand mold strength and moldability of casting mold by mixing a novolak type phenolic resin contg. the compd. of an alkaline earth metal at a low ratio and having a specific ortho rate and hexamine with sand at a specific ratio thereby coating the sand. CONSTITUTION:The novolak type phenolic resin which contains <=0.05wt% compd. such as oxide or hydroxide of the alkaline earth metal, has 45-50% ortho rate and is added with 0.05-2pts.wt. amino silane coupling agent such as N-beta(aminoethyl)-gamma-aminopropyl trimethoxysilane and 0.05-3pts.wt. org. acid such as salicylic acid or benzoic acid in order to improve hardenability is salicylic acid or benzoic acid in order to improve hardenability is mixed at 0.5-4pts. wt. and 140 deg.C with 100pts.wt. silica sand heated to 170 deg.C. The above-mentioned resin or the like is coated on the surface of the sand, by which the resin coated sand for the shell mold having the excellent sand mold strength and moldability is thus developed.