Process for the preparation of pigment preparations based on C.I. pigment violet 23

Claim 1

A process for the preparation of pigment preparations based on C.I. Pigment Violet 23 (No. 51 319) of the formula I ##STR5## which process comprises the process steps of a) wet milling the coarsely crystalline pigments of the above dioxazine compound in the presence of pigment dispersants of the formula II Q[-Y-X].sub.m (II) in which Q is an m-valent radical of the base structure in accordance with formula I, Y is a bridge-forming grouping selected from the series consisting of --CH 2 --, --CHR 1 --, --CR 1 R 2 --, phenylene, --CO--, --SO 2 --, or --NR 3 --, or a multiple sequence of alkylene or a combination of such bridging members of different types, which may be repeated, in which R 1 and R 2 are identical or different C 1 -C 4 -alkyl and R 3 is hydrogen or C 1 -C 4 -alkyl, X is the radical of an aliphatic or aromatic, five- or six-membered heterocyclic system bound to bridging member Y via a carbon atom and each containing 1 to 3 identical or different hetero atoms belonging to the ring and being selected from the series consisting of nitrogen, oxygen and sulfur, which can additionally contain a benzo-fused ring and be substituted by C 1 -C 4 -alkyl, C 2 -C 4 -alkenyl, C 1 -C 3 -hydroxyalkyl or phenyl, or is a phthalimido radical bound to bridging member Y via the imide nitrogen, which may be substituted on the benzenoid ring by chlorine, bromine, nitro, carboxyl, N-(C 1 -C 5 -alkyl)carbamyol, N-phenylcarbamoyl or benzoylamino, or is a radical having the structure ##STR6## in which R 4 and R 5 each individually and independently of one another are each hydrogen, substituted or unsubstituted C 1 -C 20 -alkyl or C 2 -C 20 -alkenyl, C 5 -C 6 -cycloalkyl, substituted or unsubstituted phenyl, benzyl or naphthyl, or in which R 4 and R 5 jointly or together with the adjacent N atom form an aliphatic or aromatic, five- or six-membered heterocyclic system each having 1 to 3 identical or different hetero atoms belonging to the ring and being selected from the series consisting of nitrogen, oxygen or sulfur, and m is a numerical value of between 0.1 and 4, in which in the case of the multiple presence (m>1) of components X and Y in the dispersants of the formula II the meaning of the symbols just mentioned does not have to be identical, whose addition can take place at any desired time during the course of the combination of the two treatment operations comminution and finish (with the exception of other processing stages) defined below in more detail, first in an inert liquid medium in a stirred ball mill, which is operated at a power density of >2.5 kW per liter of milling space and a peripheral speed of the stirrer of >12 m/s, under the action of a grinding medium having a diameter of ≦1 mm, until the X-ray index as a measure of crystallinity of the resulting prepigment particles is ≦9, b) subjecting this prepigment composition in the form of the suspension of the mill base thus obtained or, in the case of isolation of the intermediate after previous dispersion in an inert organic or inorganic liquid, to a solvent finish treatment at elevated temperature and c) then isolating the finished pigment preparation.