GB1216479A - Coating compositions - Google Patents

Abstract

1,216,479. Coating. NIPPON PAINT CO. Ltd. 12 Dec., 1967 [14 Dec., 1966], No. 56333/ 67. Heading B2E. [Also in Division C3] Coating compositions comprise an organic solvent having dissolved therein a copolymer obtained by copolymerising 50-90 parts by weight of methyl methacrylate with 10-50 parts by weight of a polymerisable monomer having at least one hydroxyl group, the total amount of the monomers being 100 parts by weight; and at least one polyisocyanate in an amount of between 0.2 and 5.0 equivalents with respect to the hydroxyl groups of the copolymer; the organic solvent being incapable of reacting with the said polyisocyanate compound. Preferably from 1-30 parts by weight of the methyl methacrylate are replaced by an acrylate or methacrylate of a C 2 -C 22 alkanol. In a modification, the copolymer is derived from (a) 50-95 parts by weight of a mixture of 60-85% (by weight) of methyl methacrylate, 5-30% of styrene, vinyltoluene and/or α-methylstyrene, and 10-35% of another copolymerisable compound (unspecified) and (b) 5-50 parts by weight of a polymerisable monomer having at least one hydroxyl group. The hydroxyl-containing monomer component in the above copolymers may be a hydroxy alkyl (meth) acrylate, N-methylol-(meth) acrylamide, (meth) allyl alcohol, crotyl alcohol or a 1:1 adduct of a polymerisable unsaturated compound having a terminal epoxy group and a fatty acid (e.g. an adduct of glycidyl (meth) acrylate or allyl glycidyl ether with a fatty acid or fatty acid mixture). The copolymers may optionally include small amounts of monomer components selected from (meth)-acrylic, crotonic, itaconic, maleic or fumaric acid, (meth) acrylamide, and monomers having a tertiary amino group, e.g. N,N-di-(m)ethylamino ethyl methacrylate. Suitable polyisocyanates include aliphatic, alicyclic and aromatic diisocyanates, polyurethane-polyisocyanates and isocyanurate, allophanate or biuret group-containing polyisocyanates. Specified as suitable solvents are aliphatic, alicyclic and aromatic hydrocarbons, halogenated hydrocarbons, ethers, esters, ketones and nitriles. Pigments may be included in the compositions, e.g. metal oxides, hydroxides, silicates, chromates, sulphides, sulphates and carbonates, organic pigments, carbon black and metal flakes; exemplified are titanium dioxide, aluminium flake and Microlith 4GT Blue. The compositions can be applied by spray coating, brush coating, dip coating or roller coating to materials such as metals, wood, rubbers, glass, fibres, leathers and various polymers. Coatings so produced can be dried and cured at room or elevated temperature; curing can be accelerated by the presence of a catalyst such as dibutyl tin dilaurate, stannous caprylate or dimethylbenzylamine. In Examples, coatings are formed on steel plates previously treated with an epoxy resin-modified acrylic primer.