Process for preparing copper phthalocyanine pigments of the α-modification

Claim 1

A process for the preparation of highly pure, unsubstituted α-copperphthalocyanine which comprises: forming an aqueous suspension of α-copperphthalocyanine by regenerating α-copperphthalocyanine from its sulfate; finely distributing said α-copperphthalocyanine in said aqueous suspension; adding to said aqueous suspension a polar compound having up to 8 carbon atoms which is water-soluble or liquid under the aftertreating conditions recited below, said polar compound being an alcohol, a ketone, an ether, a carboxylic acid or a functional derivative of a carboxylic acid selected from the group consisting of esters, nitriles, amides, lactones and lactams and further being aliphatic, cycloaliphatic or saturated heterocyclic compound containing one or two identical or different hetero atoms selected from oxygen, sulfur and nitrogen; finely distributing said α-copperphthalocyanine in said aqueous medium containing said polar compound at a temperature of 15° to 80° C and continuing said fine distribution until the difference in the intensity between the maxima at 12.1 and 13 A and the minimum at 12.6 A in the Xray diagram of the product is from 1:10 to 10:4.