GB203533A - Improvements in the manufacture and production of dyestuffs and intermediate products therefor - Google Patents

Abstract

Condensation products, which are probably 2 : 21-dibenzanthronyl compounds, are prepared by heating benzanthrone or its derivatives with alkaline condensing-agents under more moderate conditions than those yielding dibenzanthrone dyes; any dye simultaneously produced is removed by means of alkaline hydrosulphite. According to examples, benzanthrone is heated with caustic potash and ethyl or methyl alcohol, caustic potash in chlorbenzene, sodium anilide in aniline, or sodium methylanilide in methylaniline; the product forms yellow needles melting above 300 DEG C.; 6-methylbenzanthrone gives a similar product melting above 350 DEG C. These condensation products are converted into dibenzanthrone dyes by heating, with or without alkaline, acid, or oxidizing condensing-agents; if free halogens or sulphuric acid are used as condensing-agents the resulting dyes contain halogen or sulphonic groups; strongly oxidizing condensing-agents produce oxidized dibenzanthrones. According to examples:-dibenzanthrone is prepared by heating the benzanthrone condensation product described above with aluminium chloride in trichlorbenzene, mercuric sulphate and sulphuric acid, or caustic potash alone or in presence of a diluent; chlorinated dyes are obtained by heating the same condensation product with a mixture of ferric chloride and common salt, or ferric chloride in trichlorbenzene, or by dissolving the condensation product in chlorsulphonic acid and passing in chlorine. The same condensation product is boiled with sodium anilide in aniline, or other metal arylides may be used similarly; the same condensation product is treated with fuming sulphuric acid at a low temperature, and the resulting sulphonic acid is heated with mercuric sulphate and sulphuric acid giving a dibenzanthrone sulphonic acid; the condensation product is treated with manganese dioxide in sulphuric acid, giving an oxidized dibenzanthrone compound, which on reduction with bisulphite, gives a green dye; the sulphonated condensation product described above is treated with lead peroxide in sulphuric acid. Specifications 16538/04 and 14498/12 are referred to.