Patent GB-870945-A (GB)
Title: Improvements in or relating to coating compositions
IPC: C09D5/25
Filed: 1958-09-16
Abstract: An aqueous dispersion copolymer composition is prepared by (a) forming a homogeneous dispersion comprising water and a mixture of alphaethylenically unsaturated monomers, at least ternary in composition, comprising 1%-15% of (A) at least one monoethylenically unsaturated monocarboxylic acid, such as acrylic, methacrylic, alpha-ethyl, alpha-phenyl, beta-phenyl or beta-ethyl, crotonic, isocrotonic, beta, beta-dimethyl acrylic, angelic, tiglic or isohydrosorbic acid; 15%-65% of (B) at least one ester of a saturated monohydric alcohol and a monoethylenically unsaturated monocarboxylic acid having an alpha-bound terminal methylene group, such as an ester of acrylic, methacrylic, alpha-ethyl or alpha-phenyl acrylic acid, with one of a number of specified alcohols, particularly a saturated aliphatic monohydric alcohol having 1 to 8 carbon atoms, and 30%-80% of (C) at least one nitrile of a monoethylenically unsaturated monocarboxylic acid having an alpha-bound terminal methylene group, such as acrylonitrile, all the percentages being based on the total weight of (a), (b) and (c), (b) initiating a polymerization reaction in the dispersion in the presence of a vinyl polymerization catalyst and effecting the copolymerization of the monomers in the absence of emulsifiers which lower the surface tension of the aqueous dispersion below 50 dynes/cm. and in the presence of colloidal silica present as an alkali-stabilized silica aquasol in an amount of at least 0,1% of silica based on the weight of the monomers; (c) forming an ammonium salt of the resulting aqueous dispersed acidic copolymer by ammoniacal neutralization to a pH of from 5,5 to 8, and (d) stabilizing the resulting aqueous dispersion of the ammonium salt of the copolymer by heating it at a temperature from 45 DEG C. to 95 DEG C. and thereafter cooling it to room temperature.  The mixture of monomers may also include a non-carboxylic auxiliary copolymerizable organic monomer having one or two sites of ethylenic unsaturation, each site constituting an alpha-bound methylene group, such as styrene, alpha-methyl styrene, vinyl touene, glycidyl methacrylate, divinyl benzene or the methacrylic acid diester of a glycol.  The catalyst system is preferably a bisulphite-persulphate redox system. Electrical insulating compositions particularly suitable for coating wire, may be prepared by mixing the aqueous dispersions with a water-dilutable, heat-reactive condensate containing methylene bridges, such as condensation products of formaldehyde with phenols, ketones, urea or melamine or mixtures thereof.  These compositions may also contain small proportions of a water-miscible solvent for the copolymer such as tetramethylene sulphone, cyclic ethylene carbonate, dimethylformamide, dimethyl acetamide, alkyl monoethers of ethylene glycol and diethylene glycol and diacetone alcohol, a bodying agent such as methyl cellulose, polyvinyl alcohol, or an alkali metal, or ammonium polyacrylate or polymethacrylate, or a resinous modifier such as polytetrafluorethylene or polyvinyl fluoride.  Specifications 667,154, 699,557, 761,928 and 826,455 are referred to.