| abstract |
Binder, which is not self-hardening, for moulding compsns. for prepn. of foundry moulds and cores consists of (a) an aq. soln. of an alkali silicate, esp. Na siliate, with a ratio by wt. of Me2O:SiO2 of 1:2.0-2.8, and 45-60 degrees Be, and (b) is not 1 anionic or nonionic surfactant. Compsn. is free-flowing and can be filled easily into complicated mould shapes, but does not settle during hardening, is gas-permeable and can be hardened by CO2, and becomes compact during hardening, thus avoiding penetration of metal into the mould. The compsn. has unlimited storage life. More conc. binders, with higher viscosity, can be used. |