GB571390A - Process and composition for making moulds and article so produced - Google Patents

Abstract

Moulds for use in casting metals, plastics or other materials are prepared by mixing pulverulent material such as foundry sand, loam, plaster of Paris, cement, or the like, with an aqueous dispersion of a hydrophilic coagulable cellulosic material as a binder and coagulating the binder; alternatively, moulds prepared in the usual way are treated on their faces with the cellulosic material. Coagulation may be effected by heating the mould and heating may be continued beyond evaporation of the liquid to effect graphitization of the cellulosic material. The cellulosic material is soluble in alkali and may be soluble or insoluble in water, and comprises alkyl cellulose ethers, e.g. methyl cellulose ether; hydroxy-alkyl cellulose ethers, e.g. hydroxy-ethyl cellulose ethers or ethyl-hydroxy-ethyl cellulose; carboxy-alkyl cellulose ethers, e.g. cellulose glycollic acid ether and its sodium and potassium salts; cellulose xanthate; cuprammonium cellulose; cellulose or regenerated cellulose rendered alkali-soluble by degradation and/or oxidation by heat, acids, alkalis, or the like to produce a material soluble in an alkaline solution of sodium zincate or stannate; or dispersions of cellulose in solvents such as zinc chloride, alkali perchlorates, alkali thiocyanates, concentrated sulphuric acid, or phosphoric acid. The material may be dispersed in sodium hydroxide, potassium hydroxide, quaternary ammonium hydroxide, tetrabenzyl ammonium hydroxide, or tribenzyl methyl ammonium hydroxide. The dispersions may comprise 2-8 per cent by weight of cellulosic material, 3-10 per cent alkali, and the remainder water. Fillers such as wood flour, clay, starch, and the like, and pigments may be added. The dispersion is mixed with the pulverulent material and the whole or part of the mould, including cores, is built therefrom, or the mould surfaces may be coated therewith by spraying, dipping, or brushing. After use, the material can be broken apart and re-used. According to examples, cellulosic materials are used to bind gypsum plaster, sand and wood flour.ALSO:Moulds for use in casting metals, plastics or other materials are prepared by mixing pulverulent material such as foundry sand, loam, plaster of Paris, cement, or the like, with an aqueous dispersion of a hydrophilic coagulable cellulosic material as a binder and coagulating the binder; alternatively, moulds prepared in the usual way are treated on their faces with the cellulosic material. Coagulation may be effected by heating the mould and heating may be continued beyond evaporation of the liquid to effect graphitization of the cellulosic material. The cellulosic material is soluble in alkalies and may be soluble or insoluble in water, and comprises alkyl cellulose ethers, e.g. methyl cellulose ether; hydroxy-alkyl cellulose ethers, e.g. hydroxy-ethyl cellulose ethers or ethyl-hydroxy-ethyl cellulose; carboxy-alkyl cellulose ethers, e.g. cellulose glycollic acid ether and its sodium and potassium salts; cellulose xanthate; cuprammonium cellulose; cellulose or regenerated cellulose rendered alkali-soluble by degradation and/or oxidation by heat, acids, alkalis, or the like to produce a material soluble in an alkaline solution of sodium zincate or stannate; or dispersions of cellulose in solvents such as zinc chloride, alkali perchlorates, alkali thiocyanates, concentrated sulphuric acid, or phosphoric acid. The material may be dispersed in sodium hydroxide, potassium hydroxide, quaternary ammonium hydroxide, tetrabenzyl ammonium hydroxide, or tribenzyl methyl ammonium hydroxide. The dispersions may comprise 2-8 per cent by weight of cellulosic material, 3-10 per cent alkali, and the remainder water. Fillers such as wood flour, clay, starch, and the like, and pigments may be added. The dispersion is mixed with the pulverulent material and the whole or part of the mould, including cores, is built therefrom, or the mould surfaces may be coated therewith by spraying, dipping, or brushing. After use, the material can be broken apart and re-used. According to examples, cellulosic materials are used to bind gypsum plaster, sand and wood flour.