Preparation of 4,4',7,7'-tetrachlorothioindigo pigments of high color strength
US4431824A · kind A · utility
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15Claims
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Key dates
| Filing date | Jan 6, 1982 |
| Grant date | Feb 14, 1984 |
| Priority date | — |
| Expiry date | Jan 6, 2002 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC09B67/0014
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
4,4',7,7'-Tetrachlorothioindigo pigments of high color strength are prepared by oxidizing 3-hydroxy-4,7-dichlorothionaphthene or a mixture of tetrachlorothioindigo and hydroxydichlorothionaphthene in aqueous alkaline suspension with a salt of a nitro-aromatic sulfonic acid, in the presence of a high-boiling, water-immiscible or only slightly water-miscible aromatic liquid, at from 40.degree. to 100.degree. C., and heating the organic suspension to 110.degree.-180.degree. C. Pigmentary forms of tetrachlorothioindigo are isolated which give deep colorations of high brilliance when reduced with white pigments.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.