Improvements in or relating to sand coated with a resin for the hot-box method of manufacture of foundry cores

摘要

A resin-forming composition is obtained by reacting 2.25 to 4.5 moles of formaldehyde with 1 mole of phenol in the presence of furtural alcohol under aqueous alkaline conditions. The product is mixed with sand, a curing agent, and optionally a secondary binding agent such as a rosin to give foundry mould compositions. Urea may also be included to react with excess formaldehyde. The curing agent may be a mixture of an acid and an ester which decomposes to release further acid during curing, e.g. a mixture of p-toluene sulphonic acid and an alkyl ester thereof.