摘要 |
Casting compositions comprise liquid thermosetting resins and at least 50 per cent by weight of sand. Specified resins are unsaturated polyesters together with non-volatile cross-linking solvents, e.g. styrene, vinyl toluene, cyclopentadiene, vinyl acetate, diallyl phthalate and triallyl cyanurate, and "epon" type resins derived by condensing epichlorhydrin with bisphenol A. The polyesters may be derived from maleic, fumaric, phthalic, malic, adipic, pimelic, suberic, sebacic and succinic acids and anhydrides, and ethylene glycol, diethylene glycol and propylene glycol. They may be modified by unsaturated monohydric alcohols, e.g. allyl alcohol, and fatty acids, and may contain inhibitors, e.g. hydroquinone, tert.-butyl catechol and quinone, catalysts, e.g. hydrogen peroxide, benzoyl peroxide and methyl ethyl ketone peroxide, and driers, e.g. cobalt and manganese naphthenates. Preferably a mixture of rigid and flexible polyesters is used. The compositions may also contain pigments, e.g. titanium dioxide, anti-foaming agents, suspending agents, e.g. cation modified clays such as the ammonium, phosphonium, oxonium, sulphonium, arsonium, stibonium and telluronium derivatives of bentonite, e.g. dimethyldioctadecyl ammonium bentonite, fireproofing agents, e.g. antimony trioxide and chlorinated paraffin wax, and tricresyl phosphate. The compositions may be cast in stainless steel, glass or wood moulds which may be coated with polytetrafluorethylene, glass, enamel, frit or porcelain, to form tubs and table tops. The initial stages of curing may be conducted to low temperatures and the articles then heated to complete the curing. |