Neue wasserunloesliche Nitroazofarbstoffe und Verfahren zu deren Herstellung

1,134,374. Monoazo dyes. CIBA Ltd. 26 July, 1967 [29 July, 1966], No. 34292/67. Heading C4P. The invention comprises water-insoluble azo dyes of formula R 1 -NH-R 3 (N0 2 )-N = N-R 4 wherein R l is a phenyl residue, R 3 is a pphenylene residue containing the nitro group in meta-position to the azo group and R 4 is a phenyl residue containing a hydroxyl group in ortho-position to the azo group. The dyes are prepared by condensing a 21-hydroxy-azobenzene containing in the 4-position a halogen atom and in the 3-position a nitro group with an aminobenzene. The starting materials are prepared by coupling a diazotized 4-halo-3- nitroaniline with a phenol. The dyes are used to colour fibrous materials of cellulose acetate, polyamides and, in particular, polyesters in yellow to red shades.