Walter C Zukowski

US Patent:

52295150, Jul 20, 1993

Filed:

Jun 7, 1991

Appl. No.:

7/712016

Inventors:

Johannes Pfenninger - Rechthalten, CH
Walter C. Zukowski - Wilmington DE
Fridolin Babler - Hockessin DE
Edward E. Jaffe - Wilmington DE

Assignee:

Ciba-Geigy Corporation - Ardsley NY

International Classification:

C09B 4800

US Classification:

546 49

Abstract:

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.

US Patent:

52812693, Jan 25, 1994

Filed:

Sep 14, 1992

Appl. No.:

7/944591

Inventors:

James B. Ganci - Wilmington DE
Shivakumar B. Hendi - Newark DE
Walter C. Zukowski - Wilmington DE

Assignee:

Ciba-Geigy Corporation - Ardsley NY

International Classification:

C09B 4800

US Classification:

106497

Abstract:

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.