GB277949A - Improved manufacture of pigments and pigmented products - Google Patents

Abstract

277,949. Stubner, E. C. de. Sept. 23, 1926, [Convention date]. Colouring plastic compositions.-For the colouring of products such as collodion, celluloid, and artificial leather, pigments formed by precipitation in aqueous media are dehydrated by adding a fluid miscible with water and compatible with the material, or some constituent thereof. which is to be coloured. The precipitate is washed, and preferably filter-pressed or centrifuged to remove surplus water; it is then treated with the appropriate fluid. For example, for colouring cellulose formate, pyridine is suitable; for cellulose triacetate or triethyl cellulose, alcohol or acetone. The fluid may be continuously applied to the precipitate, as by percolation, the fluid being recovered and dehydrated for reuse. Products having a cellulose base may be pigmented by forming the precipitate in situ on the material and then effecting dehydration with a water miscible fluid in which the cellulose derivative is insoluble, but which is compatible with the solvent in which the cellulose derivative may be subsequently dissolved. In an example lead chromate is precipitated from solutions of potassium bichromate and lead acetate in the presence of hydrated soluble cellulose, and the product dehydrated with alcohol. The dehydrated coloured product may be employed for making coloured celluloid, artificial leather, &c. Metals such as copper, silver, antimony, gold, &c., which may be produced by precipitation in aqueous media, may be used as pigments.