A process for the preparation of pigment forms of the iasierenden and of the chlorinated indanthrone

摘要

1. A process for the production of transparent pigmentary forms of indanthrone and of chlorinated indanthrone by oxidation, with air, of the appropriate leuco coumpounds in aqueous alkaline suspension in the presence of dithionite and 0.2 to 20% by weight, based on the leuco compound, of a surfactant, characterized in that the oxidation is carried out under the simultaneous action of shearing forces at temperatures of from 20 to 100 degrees C.