GB537070A - Manufacture of azo pigments - Google Patents

Abstract

537,070. Organic pigments. TWITCHETT, H. J., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Nov. 3, 1939, No. 29301. [Class 2 (iii)] The azo pigment, 3-nitro-4-aminotoluene # acetoacetanilide, is modified to obtain a product of a similar shade but of a greater tinctorial strength by effecting the coupling under such conditions that the coupling product of diazotized 3-nitro-4-aminotoluene with acetoacet-4- chloroanilide is present in the coupling medium either during the coupling or immediately thereafter, the second coupling component being used in a molecular proportion of 5 to 40 per cent. of the total amount of the two coupling components. In examples, (1) a solution of diazotized 3-nitro-4-aminotoluene is added slowly to a suspension of the two arylides obtained by dissolving the mixture in dilute sodium hydroxide and adding acetic acid and sodium acetate and, after stirring, the precipitate is filtered off, washed and dried ; (2) 90 per cent. of the diazo solution is added slowly to a similar suspension of acetoacetanilide, a similar suspension of acetoacet-4-chloroanilide is then added, whereupon the remaining 10 per cent. of the diazo solution is slowly added and the precipitate is filtered off &c. as in (1), (3) similar suspensions of acetoacetanilide and acetoacet-4-chloroanilide. are similarly coupled separately and simultaneously with 90 per cent. and 10 per cent. respectively of the diazo component and the resulting suspensions are immediately mixed and stirred and the precipitate is filtered off &c. as in (1); (4) 10 per cent. of the diazo solution is slowly added to a similar suspension of acetoacet-4-chloroanilide, a similar suspension of acetoacetanilide is then added, whereupon the remaining 90 per cent. of the diazo solution is slowly added and the precipitate is filtered off &c. as in (1). Specification 517,456 is referred to.