Patent ID: 6090196
Filing Date: 2000-07-18
Classification: C09B

Abstract:
A process for the preparation of a beta quinacridone pigment having a 10/90 tint reflection spectrum at complete hide which is measured from 400 to 700 nm, having a peak at 420 nm.+-.10 nm, a negative slope from 420 nm to 580 nm, a positive slope from 580 to 660 nm followed by a shoulder from 660 to 700 nm, and wherein the reflection at 420 nm is above 35%, and at 580 nm about 14% comprising oxidation of 6,13-dihydroquinacridone with a m-nitrobenzene sulfonic acid salt in the presence of a particle growth inhibitor and a base in a liquid phase, wherein the particle growth inhibitor is from 1.1 to 1.3 parts by weight of quinacridone monosulfonic acid or an equivalent amount of a salt thereof, based on 100 parts by weight of 6,13-dihydroquinacridone.