GB841910A - Improvements in or relating to pigmented coating compositions - Google Patents

Abstract

A coating composition comprises a methyl methacrylate polymer having a relative viscosity of 1,117-1,196 (as determined by the method described) as the preponderant film-forming material, solvent therefor, pigment, and 0,1-10 per cent by weight, based on the total weight of non-volatile constituents in the coating composition, of cellulose nitrate, propionate, butyrate, acetate-butyrate, acetate-propionate, or mixtures thereof. Both methyl methacrylate homopolymers, and copolymers with minor amounts preferably from 2-25 per cent by weight of acrylic and methacrylic acids, alkyl acrylates with 1-4 carbon atoms in the alkyl group, alkyl methacrylates with 2-4 carbon atoms in the alkyl group, vinyl acetate, acrylonitrile, and styrene (and especially a copolymer of 98 per cent by weight methyl methacrylate with 2 per cent by weight methacrylic acid), may be used. The cellulose ester preferably comprises 0,5-8 per cent by weight of the total weight of nonvolatile constituents in the composition. A plasticizer for the polymer may be present, especially benzyl butyl phthalate in amount 10-50 per cent by weight based on the weight of the polymer. Other preferred platicizers include dibutyl-, 2-ethylhexyl benzyl-, and dicyclohexylphthalates, and triphenyl phosphate. Other plasticizers which may be used include diallyldibenzyl-, butyl cyclohexyl- and di (methyl cyclohexyl)- phthalates, mixed benzoic acid and fatty oil acid esters of pentaerythritol, poly (propylene adipate)- and diethylene glycoldibenzoates, tetrabutyl thiodisuccinate, butyl phthalyl butyl glycollate, acetyl tributyl citrate, dibenzyl sebacate, tricresyl phosphate, toluene ethyl sulphonamide and the di (2-ethyl hexyl) ester of hexamethylene diphthalate. Pigments may include iron blues, organic reds and maroons, lakes, phthalocyanines, silica, talc, china clay, metallic oxides, silicates, chromates, sulphides, sulphates, and carbon black. Solvents may include aliphatic, alicyclic and aromatic hydrocarbons (e.g. toluene, xylene), alcohols (e.g. isopropyl-, butyl-, and amyl alcohols and methyl isobutyl carbinol), esters and ethers (e.g. butyl acetate, methyl isobutyl carbinyl acetate, and ethylene glycol monoethyl ether acetate) and ketones (e.g acetone, methyl ethyl ketone, and methyl isobutyl ketone). Modifying agents may also be present e.g. soya lecithin, silicone fluids, triethanolamine, fatty oil acids and glyceride oil derivatives. Specifications 676,765 and 801,337 are referred to.