GB341884A - Improvements in the manufacture and production of brominated vat dyestuffs of the benzanthrone series - Google Patents

Abstract

Brominated benzanthronepyrazolanthrone derivatives are prepared by brominating an alkali-condensed N.Bzt-pyrazolanthronylbenzanthrone in presence of an inorganic diluent and in presence of a halogenation catalyst. Suitable diluents are sulphuric acid and derivatives thereof, such as chlorsulphonic acid and oleum, metal chloride melts containing alkali or alkaline earth metal halides. When using these diluents and working at sufficiently high temperatures chlorine may also enter the brominated molecule; with chlorsulphonic acid above about 70 DEG , with aluminium chloride above about 150 DEG , and with iron chloride above about 100 DEG . Suitable catalysts are iodine, sulphur, selenium, phosphorus, and compounds thereof, or metals or metal salts, such as mercury, iron, nickel, manganese, antimony and compounds thereof. The nature and dyeing properties of the product are determined by the halogen transferrer and the reaction temperature employed; the most greenish dyeings are obtained at the lower temperatures in the presence of iodine or mercury as catalyst. Bromination in chlorsulphonic acid may often be effected with only theoretical quantities of bromine. These products are characterized by the greenish tinge of their dyeings which are uniform and fast to light and atmosphere. The leuco esters may be obtained by the usual methods. In examples is described the production of mono-, di-, tetrabromo-, tribromodichloro-, and other bromo- and bromochloroderivatives of the alkali-condensed N.Bzt-pyrazolanthronylbenzanthrone dyeing blue shades from the vat. Specifications 298,775 and 325,550, [both in Class 2 (iii), Dyes &c.], are referred to. Reference has been directed by the Comptroller to Specification 298,284, [Class 2 (iii), Dyes &c.].