Bayer Aktiengesellschaft

Anton Adams

Detlef-Ingo Schutze

Werner Steinbeck

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.

Process for the preparation of S-arylthioglycolic acids of the formula ##STR1## in which A designates a benzene ring, which can be substituted by 1, 2, 3, 4 or 5 substituents from the series halogen, nitro, hydroxyl, mercapto, trifluoromethyl, alkyl, aryl, alkoxy, aryloxy, acylamino, alkylamino, arylamino, alkylmercapto, arylmercapto, cyano, carboxyl, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aryloxycarbonyl or optionally substituted aminocarbonyl, or represents a benzene ring, which optionally carries 1 or 2 of the previously mentioned substituents, to which a carbocyclic or heterocyclic aromatic ring is attached, characterized in that aryldiazonium salts of the formula ##STR2## in which A has the meanings given for the formula (I) and

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Siegbrug-Kaldenauen, Germany

Anton Adams