Clariant Corporation

Martin Boehmer

Manfred Urban

Dieter Schnaitmann

Joachim Weber

Hans-Tobias Macholdt

Ruediger Baur

Margit Haberlick

Quinacridone mixed-crystal pigments of the gamma phase

Use of mixed-crystal pigments of the quinacridone series in electrophotographic toners and developers, powder coatings and inkjet inks

Linear unsubstituted and substituted quinacridone pigments and quinacridone mixed-crystal pigments are obtained by cyclizing dianilinoterephthalic acid with polyphosphoric acid and then hydrolyzing the ring closure mixture, said mixture being metered into an amount of water or orthophosphoric acid which is such that the final orthophosphoric acid concentration is greater than or equal to 50% by weight in the hedrolysis mixture.

Process for preparing quinacridone pigments

The invention relates to a process for preparing N,N&prime;-dimethylperylene-3,4,9,10-tetracarboxylic diimide, utilizing the reaction of perylene-3,4,9,10-tetracarboxylic dianhydride with monomethylamine, which comprises employing at least 2 times the molar amount of monomethylamine per mole of perylene-3,4,9,10-tetracarboxylic dianhydride and at least 3 times the amount by weight of water based on the weight of the dianhydride, conducting the reaction at a temperature from 50 to 200&deg; C., removing unreacted monomethylamine by distillation, subjecting the resulting crude pigment to wet grinding in a liquid, aqueous or aqueous-organic medium in a stirred ballmill which is operated with a power density of more than 1.5 kW per liter of milling space and a stirrer tip speed of more than 12 m/s under the action of grinding media having a diameter of less than or equal to 0.9 mm, and isolating the pigment obtained, with the proviso that at any desired point during the process, but no later than during wet grinding, one or more additives from the group consisting of pigment dispersants and surfactants are added.

Process for preparing N,N&prime;-dimethylperylene-3,4,9,10-tetracarboxylic diimide in transparent pigment form

Mixed crystal pigments of the quinacridone series New quinacridone mixed crystal pigments consisting of

Mixed crystal pigments of the quinacridone series

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Neu-Anspach, Germany

Martin Boehmer