Bayer Aktiengesellschaft

Werner Steinbeck

Detlef-Ingo Schutze

Anton Adams

Wolfgang Harms

Gunter Gehrke

Process for preparing 4,4'-diamino-1,1'-dianthraquinonyl pigments by desulphonation of 4,4'-diamino-1,1'-dianthraquinonyl-3,3'-disulphonic acid in sulphuric acid, characterized in that after the desulphonation water is added to the sulphuric acid solution, 4,4'-diamino 1,1'-dianthraquinonyl is isolated as sulphate, the sulphate is hydrolysed, if necessary by redissolving it in sulphuric acid and adding the solution to water, and the pigment is isolated, if necessary, after treatment with an organic solvent.

Process for preparing 4,4'-diamino-1,1'-dianthraquinonyl pigments

Process for preparing 4,4'-diamino-1,1'-dianthraquinonyl pigments by desulphonation of 4,4'-diamino-1,1'-dianthraquinonyl-3,3'-disulphonic acid in sulphuric acid, characterized in that after the desulphonation water is added to the sulphuric acid solution, 4,4'-diamino 1,1'-dianthraquinonyl is isolated as sulphate, the sulphate is hydrolyzed, if necessary by redissolving it in sulphuric acid and adding the solution to water, and the pigment is isolated, if necessary, after treatment with an organic solvent.

A process for the preparation of a concentrated storage-stable aqueous solution of the dyestuff of the formula ##STR1## is characterized in that the reaction mixture obtainable from the quinone derivative of the formula ##STR2## by sulphation and subsequent oxidation cyclization, preferably with ammonium, sodium or potassium peroxodisulphate, in oleum is diluted with water or sulphuric acid to a sulphuric acid concentration of 37-50%, preferably 41-43%, and the product which thereby precipitates is separated off and brought to a pH of about 2-6, preferably 3-4, in water with basic lithium compounds, preferably lithium carbonate or lithium hydroxide.

Process for the preparation of a concentrated aqueous reactive dyestuff

95-99% pure 4,5-dinitro-1,8-dihydroxyanthraquinone which is essentially free from by-products is obtained by 'direct nitration' of 1,8-dihydroxyanthraquinones or 1,8-dimethoxyanthraquinones if the concentrations of acid are chosen such that, when the nitration reaction and, if appropriate, the saponification reaction have ended, an 80-100% strength sulphuric acid is present, or such a sulphuric acid concentration is established by adding water, and the 4,5-dinitro-1,8-dihydroxyanthraquinone which crystallizes out is separated off.

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Cologne, Germany

Werner Steinbeck