Method, resin and catalyst for increasing the tensile strength and core hardness of a sand mold or core

摘要

The tensile strength and core hardness of a sand mold or core is increased by incorporating into a mixture of a thermosetting acid- hardenable resin and sand, a dialkyl ester of the formula: ##EQU1## wherein R.sub.1 and R.sub. 2, which may be the same or different, are selected from alkyl of 1 to 20 carbon atoms and n is 2, 3 or 4. The ester may be added directly to the resin or sand, or in conjunction with the acid catalyst. Ferric chloride together with the dialkyl ester provides a sulfur-free catalyst for polymerization of the resin.