GB840776A - Improvements in and relating to coal tar emulsions - Google Patents

Abstract

An aqueous emulsion of coal tar contains a polyvinyl resin or an alkyd resin, a solvent for the resin, an anionic surface-active agent and a stabilizing agent. The emulsion may be made by dispersing a mixture containing coal tar and resin together with a solvent for the resin in an aqueous solution containing an anionic surface active agent and a stabilizing agent. The coal tar employed in the present invention is the usual material resulting from the carbonization of coal by any of the known methods of carbonization, e.g. coke-oven tar, or gas works tar. There may be advantage in adding to the coal tar a certain amount, not more than 25% of its weight, of xylene or like hydrocarbon, thereby to lower the viscosity of the material and improve its miscibility with the resin solution. The anionic surface-active agents exemplified are: an ammonium salt of a sulphated polyoxyethylene ether of nonylphenol, alkali-metal and ammonium salts of oleic acid, sulphonated castor oil, sodium dodecyl benzene sulphonate, sulphated fatty alcohols, sulphosuccinic acid esters. The preferred stabilizing agents are: the sodium salt of carboxymethyl cellulose, animal glue or casein. The preferred synthetic resins are: a terpolymer of vinyl chloride, vinyl acetate and maleic anhydride in the ratio of 86:12:1, copolymers of vinyl chloride and vinyl acetate in the ratio 87:13, alkyd resins which are the reaction products of one or more dicarboxylic acids or their anhydrides, with one or more polyhydric alcohols. The solvent for the resin is generally blown linseed oil or isophorone.ALSO:An aqueous emulsion of coal tar contains a polyvinyl resin or an alkyd resin, a solvent for the resin, an anionic surface-active agent and a stabilizing agent. The emulsion may be made by dispersing a mixture containing coal tar and resin together with a solvent for the resin in an aqueous solution containing an anionic surface-active agent and a stabilizing agent. The coal tar employed in the present invention is the usual material resulting from the carbonization of coal by any of the known methods of carbonization, e.g. coke-oven tar, or gas works tar. There may be advantage in adding to the coal tar a certain amount, not more than 25% of its weight, or xylene or like hydrocarbon, thereby to lower the viscosity of the material and improve its miscibility with the resin solution. The anionic surface-active agents exemplified are: an ammonium salt of a sulphated polyoxyethylene ether of nonylphenol, alkali-metal and ammonium salts of oleic acid, sulphonated castor oil, sodium dodecyl benzene sulphonate, sulphated fatty alcohols, sulphosuccinic acid esters. The preferred stabilizing agents are: the sodium salt of carboxymethyl cellulose, animal glue or casein. The preferred synthetic resins are: a tripolymer of vinyl chloride, vinyl acetate and maleic anhydride in the ratio of 86:12:1, copolymers of vinyl chloride and vinyl acetate in the ratio 87:13, alkyd resins which are the reaction products of one or more dicarboxylic acids or their anhydrides, with one or more polyhydric alcohols, while the solvent for the resin is generally blown linseed oil or isophorone. The emulsions of the present invention can be easily applied to a surface, e.g. by spraying or brushing, to form a film which, on drying, forms a protective coating showing excellent continuity, avoidance or cracks, adherence to a metal surface, and resistance to weathering and chemical action. Such emulsion can also be applied on a wet surface and, since they contain only small amounts of organic solvents, their toxicity is low.