Patent ID: 7984750
Filing Date: 2011-07-26
Classification: B22C

Abstract:
1. A method of making a polyurethane resin bonded sand core for a casting process in which the core is to be contacted with cast metal in defining a surface of a casting and the polyurethane resin binder is to be decomposed by cast metal heat for removal of the core sand from the solidified casting, the method comprising: preparing two or more streams of polyurethane resin precursor materials for addition to a mass of sand particles, the precursor materials being formulated to form a polyurethane resin bond between sand particles for the molding of a sand core for a metal casting, the polyurethane resin being intended to decompose when heated by cast metal; adding an alkali metal hydroxide to at least one of the streams of polyurethane precursor resin materials; mixing the polyurethane precursor streams, including the alkali metal hydroxide, with sand particles; and molding the sand particles as the precursor streams interact and cure to form a polyurethane resin bonded sand core, the composition and amount of alkali metal hydroxide particles being effective to reduce the decomposition temperature of the polyurethane resin when cast metal contacts a surface of the core.