GB538958A - Improvements in the production of coloured products containing organic film-forming substances - Google Patents

Abstract

538,958. Cellulose derivative and synthetic resin compositions ; artificial filaments &c. LORD. G., and REEVES, G. Feb. 21, 1940, No. 3273. [Classes 2 (ii) and 2 (iii)] [Also in Group III] A coloured product is obtained by precipitating a colouring matter in finely divided form in an aqueous liquid, replacing water of the wet colouring matter by a liquid which is miscible with a solution of a film-forming substance in an organic liquid, the replacement being effected while maintaining the colouring matter wet with liquid, mixing the wet colouring matter with the solution of the film-forming substance and then precipitating the coloured filin-forming substance. A solution of the coloured product may be used for the production of artificial filaments, films, and the like. The water of the wet colouring matter may be displaced by a solvent of the film-forming substance. The coloured solutions may be precipitated by treatment with a non-solvent so as to obtain the coloured film-forming product which is subsequently worked up to any desired form. In an example, a vat dyestuff dissolved in sulphuric acid at 0‹ C. is poured into a large amount of water and crushed ice. The dyestuff is precipitated in finely divided form, filtered, washed, and pressed. It is then rinsed with acetone and ground with more acetone in a pebble mill. The paste is added to a solution of cellulose acetate and the solution is then poured into. water to precipitate the coloured cellulose acetate. Dyestuffs which may be used are those of the indigoid, thioindigoid, anthraquinone, and dibenzpyrenequinone series, phthalocyanine dyes, azo dyes, or water-insoluble bases of basic dyes. Inorganic pigments may be used. A deeply coloured product may first be produced and this mav be mixed with an uncoloured solution of film-forming substance to give a final product of the desired shade. The film- or filamentforming substance may be cellulose propionate, butyrate, aceto-propionate or other cellulose ester or ether, or polyvinyl acetate.