Thio-indigo dyestuffs
AssigneeHoechst Aktiengesellschaft
InventorsErnst Spietschka, Manfred Urban
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Abstract
Thioindigo and its derivatives are obtained in high yield and excellent purity by oxidizing corresponding 3-hydroxy-thionaphthenes with peroxo-disulfate in an aqueous alkaline solution.
Claims2
A thioindigo dyestuff prepared by oxidizing, at a temperature of -20.degree. to +50.degree. C., a 3-hydroxy-thionaphthene or benzothionaphthene with an aqueous alkaline solution of an ammonium or alkali metal peroxo-disulfate.
4,4',7,7'-tetrachlorothioindigo of high purity prepared by oxidizing, at a temperature of -20.degree. to +50.degree. C., 4,7-dichloro-3-hydroxythionaphthene with an aqueous alkaline solution of an alkali metal peroxo-disulfate.
Dependencies are inferred from the claim text.