GB732005A - Foundry sand compositions and sand moulds formed therefrom - Google Patents

Abstract

A composition suitable for making foundry sand moulds or cores comprises sand, clay, water and a polymeric water-soluble polyelectrolyte having a weight-average molecular weight of at least 10,000 and a substantially linear continuous carbon chain obtained by the polymerization of a compound containing an aliphatic unsaturated group. The composition preferably contains from 1 to 15 parts of clay and from 0.02 to 1.0 parts of polyelectrolyte per 100 parts of sand. The polyelectrolyte may be (1) a copolymer of (a) a polycarboxylic acid or a derivative thereof such as maleic anhydride, maleic, fumaric, itaconic, citraconic and aconitic acids, the amides of these acids, the alkali metal, alkaline earth metal and ammonium salts of these acids, the partial alkyl esters, salts of the partial alkyl esters, and the substituted amides of these polycarboxylic acids and one or more of (b) acrylic acid, acrylamide, acrylic acid salts of alkali metal and ammonium, N-substituted acrylamide or a corresponding derivative of methacrylic or crotonic acid, ethylene, propylene, isobutylene, styrene, alpha-methylstyrene, vinyl acetate, vinyl chloride, vinyl formate, a vinyl alkyl ether, an alkyl acrylate or methacrylate, vinyl sulphonic acid, vinyl phosphonic acid and vinyl pyrrolidone; (2) a homopolymer of acrylic or methacrylic acid or the alkali metal or ammonium salts thereof, acrylamide, methacrylamide, an N-alkyl-substituted amide, an N-amino alkyl amide, an N-alkyl-aminoalkyl substituted amide, an amino alkyl acrylate, an aminoalkyl methacrylamide, or an N-alkyl substituted aminoalkyl acrylate or methacrylate, or a copolymer of one of the above with ethylene, propylene, isobutylene, styrene, alpha-methylstyrene, vinyl acetate, vinyl formate, a vinyl alkyl ether, acrylonitrile, methacrylonitrile, vinylidene chloride, vinyl chloride, or an alkyl acrylate, methacrylate, maleate or fumarate; (3) a polymer containing amine radicals such as a poly N-vinyl amine, a poly-N-allylamine, polyvinyl pyridine and its amine and quaternary ammonium salts, a product derived by the polymerization of an amide or imide, followed by reduction, and a product obtained by the hydrogenation of an acrylonitrile or methacrylonitrile polymer or copolymer; (4) a polymer of a vinyl-substituted amide such as vinyl pyrrolidone, vinyl piperidone, an alkyl-substituted product thereof, N - vinyl - N - methylformamide, N-vinyl formamide, and N-vinyl acetamide, or a copolymer of one of the above with vinyl acetate, acrylonitrile, isobutylene, ethylene, styrene, vinyl chloride, vinylidene chloride, vinyl formate, a vinyl alkyl ether, an alkyl acrylate or methacrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, a monoalkyl maleate, or an aminoalkyl ester or alkali metal or ammonium salt of acrylic acid; (5) a polymer of vinyl sulphonic acid or a copolymer thereof with vinyl chloride, acrylonitrile, styrene or vinyl acetate; (6) a polymer prepared by hydrolysis of a polymer containing nitrile groups; (7) a polymer containing hydrophilic lactone groups prepared by hydrolysis of a copolymer of maleic anhydride and vinyl acetate; (8) a polymer prepared by the hydrolysis of vinyl acetate copolymers; (9) a polymer prepared by esterifying polyvinyl alcohol with a dibasic acid; (10) a polymer obtained by reacting a polymer or copolymer of vinyl chloroacetate or vinyl chloroethyl ether with an amine; (11) a polymer prepared by the ammonolysis of polyvinyl methyl ketone. Preferred polyelectrolytes are the sodium salt of a partially hydrolysed polyacrylonitrile and a copolymer of vinyl acetate and maleic anhydride. Other ingredients which may be present in the composition are natural and synthetic resins, flour, cereals, sea coal, fly ash, zirconite, and bituminous additives such as asphalt.