Improvements in the production of thermoplastic powders

Dry powdered thermoplastic material, which does not contain a plasticizer, is heated in intimate admixture with an effect material to a temperature of at least 120 DEG C., but insufficiently high to cause any substantial fusing together of the particles of the thermoplastic material, until mechanical segregation of the effect material from the thermoplastic material has been rendered difficult. The thermoplastic material may be cellulose acetate, cellulose propionate, cellulose acetate-propionate, cellulose acetate-butyrate, ethyl cellulose, benzyl cellulose, nylon 66, polyvinyl chloride, polystyrene or polymethyl-methacrylate. The effect material may be a dye or pigment. The dyes specified include azo, aminoanthraquinone or nitro-aromatic amine dyestuffs, and the pigments include titanium dioxide, barium sulphate, prussian blue, ultramarine, chrome yellow, ferric oxide, indanthrone and its halogen derivatives, flavanthrone, dibenzanthrone and its halogen and alkoxy derivatives, water-insoluble ...