Production of mould parts, e.g. foundry cores, involves moulding a mixture of sand and resol-based binder containing oxyanions, passing carbon dioxide to harden the binder and purging with compressed air

摘要

In a process for the production of hardened mould parts from granular moulding material (I) by moulding a mixture of (I) with an aqueous binder containing a resol and oxyanions which are prevented from reacting by the high pH, the mould is purged with a gas containing little or no carbon dioxide after the binder has been hardened by passing carbon dioxide. A process for the production of hardened mould parts from a granular moulding material (I) involves (1) making a mixture of (a) (I) and (b) a binder comprising an aqueous solution of resol (A-stage resin) and oxyanions which can react with the resol to harden the binder, the pH of the solution being high enough to prevent any significant hardening, (2) moulding the mixture and (3) passing carbon dioxide gas through the mould to harden the binder by reaction of the oxyanions with the resol and then (4) passing a low-CO2 or at least essentially CO2-free gas through the mould.