Hoechst Aktiengesellschaft

Martin Bohmer

Manfred Urban

Dieter Schnaitmann

Process for the preparation of pigment preparations, which comprises wet milling the crude pigments which are present in coarsely crystalline state, or prepigments or pigments which are present in a form in which they are difficult to disperse, in a concentration of from 20 to 60% by weight based on the total weight of the pigment preparation, in a flocculation-stable liquid medium and in a stirred ball mill which is operated with a peripheral stirrer speed of more than 12 m/s, under the action of nonmetallic grinding media with a diameter of less than or equal to 1.0 mm, until the desired degree of fine division is reached, and then isolating the pigment preparation.

Process for the preparation of liquid pigment preparations

A process for preparing quinacridone pigments A process for preparing pigments, mixed crystal pigments and pigment preparations based on linear unsubstituted or substituted quinacridones of the formula (I) ##STR1## in which the substituents R.sup.1 and R.sup.2 are identical or different and are hydrogen, chlorine, bromine or fluorine atoms or are C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy or carboxamido groups which may be substituted by C.sub.1 -C.sub.6 -alkyl groups; or are phenoxy or C.sub.6 -C.sub.10 -aryl rings onto which further aromatic, aliphatic or heterocyclic rings can be fused, which process comprises hydrolyzing the reaction mixture resulting from cyclization of the respective dianilinoterephthalic acid with polyphosphoric acid or polyphosphate at a temperature of or above 110.degree. C. with water or an aqueous mineral acid solution and then isolating the pigments thus obtained directly; or subjecting the resulting prepigments, if desired after addition of organic solvents, to a finishing treatment and isolating the pigments; or subjecting the resulting coarsely crystalline crude pigments to fine dispersion and then isolating the pigments; or subjecting the prepigments obtained after fine dispersion, if desired after addition of solvents, to a finishing treatment and isolating the pigments. This gives quinacridone pigments having excellent coloristic and rheological properties.

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Neu-Anspach, Germany

Martin Bohmer