GB364087A - Improvements in the manufacture and production of vat dyestuffs - Google Patents

Abstract

Chlordibenzanthrones dyeing navy-blue to dark blue shades fast to spotting with water are prepared by treating a nitrodibenzanthrone with chlorine or agents supplying chlorine in the absence of any diluent or in the presence of an organic diluent other than phthalic anhydride or a halogenated derivative thereof, until the nitrogen content is reduced to at the most 0,5 per cent. If by such halogenation the products have a higher nitrogen content than 0,5 per cent, those parts having a nitrogen content of less than 0,5 per cent may be separated out by known methods, for example by recrystallization from organic solvents, or by way of the oxonium sulphates. Purification of crude products may also be effected by these means, or by vatting, or treatment with oxidizing agents. Suitable solvents are chlorbenzene, trichlorbenzene, and nitrobenzene, and chlorinating agents include sulphuryl chloride, benzotrichloride, and benzoyl chloride or mixtures of these. One or more halogen transferrers may be present. Reacting conditions depend on the nature of the starting-material; thus a very pure product in a glassy state is difficulty soluble, and stronger reacting conditions are necessary. The preparation of the nitro derivative and the chlorination can be effected in one operation. The chlorine content of highly chlorinated products may be diminished by the action of reducing agents according to the process of Specification 346,676. In Examples (1) nitrodibenzanthrone (Example 2 of Specification 1818/05, [Class 2, Acids and salts, Organic &c.]) is chlorinated in trichlorbenzene or nitrobenzene (with antimony, iodine or other catalyst present, if desired) until the product is practically free from nitrogen; similar products are obtained from other nitrodibenzanthrones, for example the pure mononitro derivative obtainable according to Specification 220,212, [Class 2 (iii), Dyes, &c.]: (2) the product obtained by nitrating pure dibenzanthrone is boiled with benzoyl chloride; trichlorbenzene is then added and with further boiling a stream of chlorine passed through until the product is practically free from nitrogen; the benzoyl chloride may be replaced by benzotrichloride and chlorine by sulphuryl chloride; alternatively dibenzanthrone may be nitrated in nitrobenzene and a treatment with chlorine follow immediately: (3) nitrodibenzanthrone (prepared by nitration in chloracetic acid) is chlorinated in trichlorbenzene. The product is dissolved in monohydrate and a little water added; the oxonium sulphate separating is removed and decomposed with water to give a product containing only traces of nitrogen. Specifications 22519/05, [Class 2, Acids and salts, Organic &c.], and 12817/13, [Class 2 (iii), Dyes &c.], also are referred to. The Provisional Specification refers to the use of organic diluents generally in the process.