GB616927A - Hydrolysed interpolymers of vinyl fluoride with vinyl esters - Google Patents

Abstract

Hydrolysed interpolymers are obtained by hydrolysing interpolymers of vinyl fluoride with a vinyl ester of an organic monocarboxylic acid free from non-benzenoid carbon-to-carbon unsaturation in which any carbon atom alpha to the carbon atom in the carboxyl group is attached to at least one but not more than three carbon atoms, wherein the mol. ratio of the vinyl fluoride to vinyl organic ester is within the range of from 1 : 30 to 1 : 6. Specified esters are vinyl formate, acetate, propionate, butyrate, isobutyrate, stearate, benzoate, cyclohexanoate, hexadecanoate, tetradecanoate, toluate, naphthoate and chloroacetate. Hydrolysis may be effected by cooling to 5 DEG -10 DEG C. an aqueous dispersion of the interpolymer, mixing therewith a methanol-water solution of the theoretically required amount of caustic soda at the same temperature and heating the mixture to 80 DEG -85 DEG C. until a clear solution is obtained. The solution is neutralised, e.g. with hydrochloric acid, filtered, the product precipitated by sodium chloride and filtered. Alternatively, the interpolymer, dissolved in a benzene-methanol mixture may be added to a refluxing methanol solution of caustic alkali, the mixture further refluxed, cooled and the precipitated product filtered. Substantially completely hydrolyzed interpolymers are soluble in hot water and in hot mixtures of water and an alcohol of the general formula CnH2n+1 OH, where n=1, 2, 3 or 4 containing up to 25 per cent by weight of the alcohol. On cooling, the resultant solutions form reversible gels. These are suitable in photographic applications, as films, filaments which may be oriented by stretching, and fibres. Interpolymers for use in the invention may be prepared by interpolymerizing one molar proportion of vinyl fluoride with from 6 to 30 molar proportions of the vinyl ester at temperatures of 70 DEG C. or less, at pressures up to 300 lbs./sq. in. in the presence of a peroxy catalyst and in aqueous dispersions containing sodium lauryl sulphate and sodium dihydrogen phosphate.