GB1441868A - Coating compositions - Google Patents

Abstract

1441868 Curable coating compositions E I DU PONT DE NEMOURS & CO 31 Oct 1974 [14 Nov 1973] 47185/74 Heading C3P [Also in Division B2] Curable coating compositions comprise (A) an aliphatic carboxylic acid which contains at least four carbon atoms in a chain which is optionally interrupted by oxygen or sulphur atoms, the chain having at least four carboxyl groups or groups containing carboxyl groups attached thereto, and the acid being free of ester groups, and (B) a fluoro-olefin copolymer containing pendant hydroxyl groups, the copolymer containing 6-65 wt. per cent fluorine and having a ratio of fluorine atoms to hydroxyl groups in the range 1 : 1 to 22 : 1; the amount of acid present being such that the number of carboxyl groups is at least equal to the number of pendant hydroxyl groups in the copolymer. The copolymer is suitably a hydrolysed fluoroolefin/vinyl ester copolymer of a fluoro-olefin/ omega-hydroxy-alkyl vinyl ether copolymer. The compositions may also include an esterification catalyst and a levelling agent, and may be made up in solvent form. After coating on to a suitable substrate the compositions are heated to effect curing, which takes place by reaction of (A) and (B) to form a cross-linked structure. In examples, (A) is one of 2,3,4,5- tetrehydrofuran - tetracarboxylic acid, 1,2,3,4- butane - tetracarboxylic acid, 1,2,3,4 - cyclopentane - tetracarboxylic acid and 1,1,2,2- tetrakis - (carboxymethylthio)ethane; (B) is a copolymer of tetrafluoroethylene and 4- hydroxybutyl vinyl ether; the solvent is either n-butanol/methyl isopropyl ketone mixture or sec-butanol/acetone mixture; the catalyst is p-toluene sulphonic acid; and a silicone levelling agent is present. Numerous substrates are mentioned, panels of polymethylmethacrylate being coated in examples.