RESIN-COATED MOLDING SAND CURABLE BY HEATING AND ITS PRODUCTION

摘要

PURPOSE:To obtain resin-coated molding sand curable by heating which has a good collapsing property of a mold after casting by coating the molding sand with a compsn. contg. a block isocyanate compd. and a resol type phenolic resin. CONSTITUTION:A resol resin for which a bisphenol or the like for the purpose of maintaining the dry strength of the sand is used and which is solid at an ordinary temp. is used as a resol type phenolic resin. The resol type phenolic resin is synthesized by bringing 1.5-4.0mol formaldehyde into reaction with 1mol bisphenol A. The resin-coated sand is obtd. by mixing under agitation a solid or soln. of a block isocyanate compd. and a solid or soln. of the resol type phenolic resin with the molding sand heated to 90-180 deg.C and evaporating the solvent during mixing according to need.