Condensation product from phenothiazine and p-nitrosophenol, process for the production of the condensation product, process for the production of sulfur dyestuffs using the condensation product and the sulfur dyestuffs prepared therewith
AssigneeCassella Aktiengesellschaft
InventorsGert Nagl, Joachim Ribka, Heinz Dickmanns, Ulrich Gotsmann
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Abstract
Green sulfur dyestuff is produced by reacting phenothiazine in sulfuric acid with an oxidizing agent, condensing the oxidized phenothiazine with p-nitrosophenol and thionating with sulfur and sodium sulfide the condensate in a bake or reflux process.
Claims10
The process for preparing a condensation product from phenothiazine and p-nitrosophenol in sulfuric acid comprising the steps of
- (a) oxidizing phenothiazine with at least 0.5 oxidation equivalents of sulphur trioxide or p-nitrosophenol per mole of phenothiazine in 60 to 100% sulfuric acid and then
- (b) condensing the product of step (a) in 60 to 90% sulfuric acid with p-nitrosophenol whereby a condensation product is obtained which contains at least 60% by weight of the indophenol-S-oxide ##STR5## and/or its tautomers.
Process for the production of sulfur dyes wherein a condensation product, which contains at least 60% by weight of the indophenol-S-oxide of the formula ##STR6## and/or its tautomers or the reduction product thereof, is thionated by the bake or reflux process.
Dependencies are inferred from the claim text.