GB607792A - Dis-azo dyes - Google Patents

Abstract

Disazo dyes, useful for producing transparent coloured photographic images, particularly by imbibition methods, are manufactured by coupling, in alkaline solution, a diazotized p-nitroaniline or p-acylaminoaniline, which may be otherwise unsubstituted or may carry one or more further substituents selected from halogen atoms and alkyl, alkoxy or sulphonic (i.e. sulphonic acid or alkali metal sulphonate) groups, with a sulphonated 1-naphthol containing in the 8-position a halogen atom, a hydroxy group or an amino group (or acylamino group subsequently saponified), reducing the nitro group with sulphide or saponifying the acylamino group in the diazo component, rediazotizing and coupling in alkaline solution with a sulphorated 1-naphthol of the kind defined, which may be the same as or preferably different from the first. When the two coupling components are identical, the dyes may also be made by direct coupling with a tetrazotized p-diamine of the benzene series, which may carry the further substituents enumerated above. Examples are given of dyes from the following components: p-aminoacetanilide, 2-methyl-4-nitroaniline, 2-methoxy - 4 - benzoylamino 5 methylaniline, and corresponding 2-methoxy, 2 : 5-dimethoxy and 2 : 5-diethoxy compounds; 1 : 8-dihydroxy-naphthalene-3 : 6-disulphonic acid, 1 : 8-aminonaphthol-4-sulphonic and 3 : 6- and 2 : 4-disulphonic acids, 1-acetylamino-8-naphthol-3 : 6-disulphonic acid (subsequently saponified) and 8-chloro-1-naphthol-3:6-disulphonic acid. Additional coupling components specified are 1 : 8-dihydroxynaphthalene-4-sulphonic and 2:4-disulphonic acids, and 1:8-aminonaphthol-5-sulphonic and 4 : 6-disulphonic acids. Specifications 329,014 and 333,239, [both in Class 2 (iii)], are referred to. Samples have been furnished under Sect. 2 (5) of disazo dyes prepared from p-nitro-o-chloroaniline and from p-nitraniline-o-sulphonic acid.