GB976963A - Improvements in or relating to aqueous coating compositions - Google Patents

Abstract

Hydroxyethyl mono-maleate is made by heating maleic anhydride (4.0 moles) with ethylene glycol (4.8 moles) under an atmosphere of carbon dioxide.ALSO:Water-soluble at least partial salts are made from copolymers prepared from ethylenically unsaturated monomers which include in their compositions 2-25% by weight of copolymerized unsaturated carboxylic acid, e.g. acrylic, methacrylic, chloroacrylic, crotonic, itaconic, maleic and fumaric acids and hydroxyethyl monomaleate, and 2-20% by weight of copolymerized monomer containing basic or amido nitrogen groups, e.g. acrylamide, methacrylamide, vinyl pyridine, vinyl pyrrolidone, and tert.-butylaminoethyl and dimethylaminoethyl methacrylates. The remaining monomers from which the copolymers are derived may be selected from styrene, vinyl toluene, vinyl acetate, acrylonitrile and C1-C8 esters of acrylic and methacrylic acids. The copolymers are made by the polymerization of the mixed monomers in solution in a water-miscible solvent, e.g. isopropyl alcohol, and in the presence of an initiator, e.g. benzoyl peroxide or azodiisobutyronitrile. After copolymerization is complete most of the solvent is distilled from the copolymer, water is added thereto, followed by neutralization by a base, e.g. ammonia, triethanolamine, triethylamine or sodium hydroxide. The resulting copolymer solutions are used in coating applications, for which purpose these are added thereto polyepoxides, e.g. vinyl cyclohexene dioxide and the condensation products of epichlorohydrin with glycol, glycerol and diphenylolpropane. Also present in the compositions may be water-dispersible aminoplasts, e.g. etherified condensation products of formaldehyde with urea and melamine, including the urea-formaldehyde resins described in Specification 823,246 and epichlorohydrin-modified aminoplasts described in Specification 796,815; pigments, e.g. titanium dioxide calcium carbonate, iron oxide, and basic lead silicochromate; ethylene glycol monoethylether, and rubber latex. Coatings made from the compositions are hardened by baking.ALSO:Phosphated steel panels are coated by applying thereto a water-borne coating composition comprising a mixture of (a) 75-95% by weight of a water-soluble at least partial salt of a copolymer which includes in its composition 2-25% by weight of copolymerized unsaturated carboxylic acid, e.g. acrylic, methacrylic, chloroacrylic, crotonic, itaconic, maleic or fumaric acid, or hydroxyethyl monomaleate and 2-20% by weight of monomer containing basic or amido nitrogen groups, e.g. acrylamide, methacrylamide, vinyl pyridine and tert. butylaminoethyl or dimethylaminoethyl methacrylate, and (b) a water-dispersible multifunctional epoxide in an amount between 0,3 and 1,3 equivalents per equivalent of acid in the copolymer. The remaining monomers from which the copolymer is derived may be selected from vinyl acetate, styrene, vinyl toluene, acrylonitrile and C1-C8 esters of acrylic and methacrylic acids. The preferred copolymer salt is the ammonium salt. Also present in the compositions may be water-soluble aminoplasts, e.g. etherified condensation products of formaldehyde with urea or melamine; pigments, e.g. titanium dioxide, iron oxide, calcium carbonate and lead silicochromate; ethylene glycol monoethyl ether and rubber latex. The compositions are sprayed on to the steel panels, and then cured by baking. According to the make up of the compositions the resulting coating may be glossy, or may be of the primer type to which an alkyd/melamine-formaldehyde enamel may be applied. Specifications 796,815 and 823,246 are referred to.