GB427973A - Process for the manufacture of azodyestuffs - Google Patents

Abstract

Disazo dyes are prepared by coupling a diazotized 2 : 4-dihalogenaniline - 6 - sulphonic acid in an acid medium with a middle component of the benzene series which couples in p-position to the amino group, rediazotizing, and coupling with a 2-acylamino-5-naphthol-7-sulphonic acid. The middle component may be coupled in the form of its N-o -methane-sulphonic acid, and the sulpho group removed before rediazotization. In the examples: (1) diazotized 2 : 4-dichloro-5-methylaniline-6-sulphonic acid is coupled in an acid medium with m-toluidine and the product is diazotized and coupled in a neutral or acid medium with 2 - benzoylamino - 5 - naphthol - 7 - sulphonic acid; the product gives red shades on cotton; (2) diazotized 2 : 4-dichloraniline-6-sulphonic acid is coupled with m-toluidine-o -methane-sulphonic acid, and hydrolysis is then effected with sulphuric acid; the aminoazo dye is diazotized and coupled with the mixed urea of 2 - amino - 5 - naphthol - 7 - sulphonic acid and p-aminoacetanilide; the product gives red shades on cotton; a similar product is obtained by using the symmetrical urea of 2-amino-5-naphthol-7-sulphonic acid as end component; (3) diazotized 2 : 4-dichloraniline-6-sulphonic acid is coupled with p-xylidine, and the aminoazo dye is diazotized and coupled with 2-acetylamino-5-naphthol-7-sulphonic acid; the product dyes cotton bluish-red. The Specification as open to inspection under Sect. 91 states that 2-amino-4-methylanisole or 3-amino-4-chlorotoluene may be used instead of m-toluidine in example 1, and that diazotized 2 : 4-dibromaniline-6-sulphonic acid may be used as the diazo component in example 3. This subject-matter does not appear in the Specification as accepted.