GB360355A - Improvements in and relating to the production of vat dyestuffs and intermediate products - Google Patents

Abstract

Halogenated vat dyes and intermediates therefor are prepared by halogenating in the presence of an inert medium consisting of phthalic anhydride or halogenated derivatives thereof, starting materials which do not contain groups or substituents attacked by either phthalic anhydride or its halogenated derivatives. Halogens or the customary halogenating agents, such as sulphuryl chloride, may be employed, and at temperatures at which the phthalic anhydride medium is molten, for example at 200 DEG and upwards. The phthalic anhydride medium is unaffected by the halogen and has the further advantage of a low volatility and low fire risk at these high temperatures; it is easily recovered from the halogenated product by extraction with water leaving the product if a dyestuff, in a state of division suitable for immediate use. In examples is described the chlorination in presence of molten phthalic anhydride, of nitrodibenzanthrone to give a pentachloro- or hexachloro derivative (dyes deep blue shades); dibenzanthrone (iodine being employed as a catalyst in some cases) to give pentachloro-, hexachloro-, and nonachlorodibenzanthrone and other chloro derivatives, according to the duration of chlorination; the pentachloro derivative dyes fast bright reddish-blue shades: isodibenzanthrone (with or without the use of iodine as catalyst) to give violet and blue-violet dyeings: a mixture of dibenzanthrone and isodibenzanthrone: 1.2 : 2<1>.1<1>-dianthraquinone dihydroazine (iodine being present as catalyst) to give a blue dyestuff: indogo: thio-indigo: benzanthrone to give Bz1-chloro and more highly chlorinated derivatives: anthraquinone to give a mixture of bodies. Similarly is described the bromination in molten phthalic anhydride of Caledon Red BN (anthraquinone naphthacridone) and of pyranthrone to give red and red-orange vat dyes respectively. The halogenation of Bz1.Bz1<1>-dibenzanthronyl is also mentioned. Specifications 254,476, 339,324, 339,954, [all in Class 2 (iii), Dyes &c.], 350,030, and 354,323 are referred to.