GB976683A - Heat-curable coating compositions - Google Patents

Abstract

A heat curable coating composition comprises a ternary combination of (I) a water insoluble interpolymer of a plurality of mono-olefinically unsaturated monomers including at least one having a substituent -COOH, CONH2 or CONHX where X is C1-4 alkyl, -R2OH, -R2OR3, -CH.R4.OH or -CH.R4.OR5 and R2 is a C1- 4 divalent saturated aliphatic hydrocarbon radical and R3, R4 and R5 are each C1-4 alkyl, and also at least one styrene and/or nuclear and/or alpha hydrocarbon substituted styrene, the interpolymer having an acid number from 15 to 150; (II) a soluble heat-reactive alcohol-modified condensate of formaldehyde and benzoguanamine and/or melamine; and (III) as plasticizing component an hydroxyl terminated polyester of at least one C6-10 saturated aliphatic dicarboxylic acid with a diol mixture including 1,4-and 1,3 butanediols in the proportions 40 to 90 and 10 to 60 wt. per cent respectively. The relative proportions are 65 to 87 wt. per cent of (I+II) and 13 to 35% of III with the weight ratio of (II); (I) being from 0.4 to 1.5:1; (I), (II) and (III) being in solution in a volatile organic mutual non-reactive solvent. (I) is preferably a terpolymer of a styrene series hydrocarbon, e.g. styrene, an alkyl, glycidyl or glycol monoether ester of acrylic or methacrylic acid, e.g. ethyl acrylate, and C3-5 mono- or di-carboxylic acid, e.g. methacrylic acid, an amide, e.g. acrylamide or modified amide thereof. Extensive lists of such monomers are given and modification of the amides may be by reaction with formaldehyde in the presence or absence of an alcohol or with alkylene oxides. Aminoplasts (II) are preferably those described in Specifications 486,519, 486,577 and 466,096 and may be used in admixture with alcohol-modified urea-formaldehyde condensates. In (III) the diol mixture may include up to 10% of C2 and C3 diols. Specified solvents and diluents are aromatic and aliphatic hydrocarbons, esters, ketones, alcohols and ether alcohols. Optional ingredients mentioned are pigments, e.g. metal oxides and salts, carbon black, organic dyes and lakes, mica and aluminium flakes; epoxy resins and epoxidised oils; and polysiloxanes. The compositions may be used to coat tins and metal bottle tops (see Division B2). Specifications 483,399, 686,234, 805,527, 872,139 and 909,322 also are referred to.ALSO:A heat-curable coating composition (see Division C3) comprises a ternary combination of (I) a water-insoluble interpolymer of a plurality of mono-olefinically unsaturated monomers (e.g. acrylates) including at least one aromatic hydrocarbon (e.g. styrene) and at least one carrying carboxyl or amide groups, (II) an alcohol-modified condensate of formaldehyde with guanamine and/or melamine, and (III) an hydroxy terminated polyester of a C6-10 saturated aliphatic dicarboxylic acid and a mixture of 1,3- and 1,4-butanediols, dissolved in a volatile organic mutual solvent. Specified solvents and diluents are aromatic and aliphatic hydrocarbons, esters, ketones, alcohols and ether alcohols. Optional ingredients mentioned are pigments, e.g. metal oxides, hydroxides, hydrous oxides, chromates, silicates, sulphates, sulphides and carbonates, carbon black, organic dyes and lakes, mica and aluminium flakes; epoxy resins and epoxidized oils; and polysiloxanes. Applications The compositions are suitable for coating metal tins and bottle tops, especially those having a lithographic coating. They may have an interior coating, e.g. of polybutadiene as described in Specification 805,527, and two exterior coatings, the first a lithographed coating which is cured before the second clear protective coating is applied. Either or both coatings may employ the composition of the invention. Curing is normally effected by baking. The coatings may be applied to sheets which are subsequently shaped or to the preshaped article. In examples, coatings are applied to tin-plated sheet steel, sheet steel, a pre-shaped aluminium container, aluminium sheets and strips and galvanized iron. Specifications 466,096, 483,399, 486,519, 486,577, 686,234, 872,139 and 909,322 also are referred to.