Process for the preparation of 4,4'-dimethyl-6,6'-dichlorothioindigo
AssigneeClariant GmbH
InventorsWolfgang Bauer, Uwe Baeumler, Hans Kurz, Hans-Peter Kreutzer
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Abstract
4,4'-Dimethyl-6,6'-dichlorothioindigo is obtained in the stable crystal modification I, distinguished by the fraction angles (2 theta): lines of high intensity: 25.99; 27.26 lines of moderate intensity: 10.27; 12.48; 22.39; 23.91; 24.82; 28.87, by oxidizing 3-hydroxy-4-methyl-6-chlorothionaphthene having a mean particle size of at most 20 .mu.m.
Claims12
A process for the preparation of 4,4'-dimethyl-6,6'-dichlorothioindigo of the formula (I) ##STR6## in the stable crystal modification I, which, in the X-ray diffraction pattern measured with CuK.sub..alpha. -radiation, has lines at the following diffraction angles 2 .theta. (.degree.):
- lines of high intensity:
- 25.99;
- 27.26
- lines of moderate intensity:
- 10.27;
- 12.48;
- 22.39;
- 23.91;
- 24.82;
- 28.87,
- wherein 3-hydroxy-4-methyl-6-chlorothionaphthene of the formula (II) ##STR7## has a mean particle size D.sub.50 of at most 20 .mu.m and is oxidized using an oxidizing agent to give the pigment of the formula I.
Dependencies are inferred from the claim text.