Ciba-geigy Corporation

Walter C Zukowski

Fridolin Babler

Edward E Jaffe

Shivakumar Basalingappa Hendi

Johannes Pfenninger

James B Ganci

Aqueous processes for the preparation of a new beta quinacridone modification possessing a magenta color having C.I.E. color space values in masstone of L=33-36, A=34-40 and B=8-15 starting with the crude pigment and comprising several milling and alternative deaggregation and recrystallization steps, the latter being facilitated at elevated temperatures aided by the presence of base and minor amounts of crystal growth auxiliaries, and the beta quinacridone modification having the indicated C.I.E. color space values.

Aqueous process for preparation of modified beta quinacridone

A process for preparing a modified beta quinacridone polytype having identified color space values which comprises the steps of dry pre-milling beta phase quinacridone, deaggregating the pre-milled product in an alcohol-base medium and ripening the deaggregated product in the presence of an oxidizing agent.

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Wilmington, DE, United States of America

Walter C Zukowski