Process for preparing high-hiding gamma-modification of unsubstituted linear transquinacridone

Claim 1

In a process for preparing the high-hiding form of the γ-crystal modification of unsubstituted linear transquinacridone having improved tinctorial strength and producing a coating of higher gloss, which process includes (a) cyclizing 2,5-diphenylaminoterephthalic acid, in highly concentrated polyphosphoric acid or in acid polyphosphoric acid ester, to obtain essentially the quinacridone in its α-modification; (b) hydrolyzing the resulting quinacridone melt obtained in step (a); (c) extracting the quinacridone obtained in step (b) with aqueous alkali, and (d) finishing the thus-isolated quinacridone, the improvement which comprises the further step of providing the presence of 0.5 to 10 percent by weight, based on the weight of the quinacridone, of a surface-active agent component during at least one of said steps (a), (b), (c), and (d), said surface-active agent component being a cationic quaternary ammonium compound; a cationic quaternary phosphonium compound; a nonionic colphony derivative; or combinations of said cationic compounds and nonionic compounds; provided, that if a said surface active component is present during said step (d), the same or a different one of said surface active components is present during at least one other of the remaining three steps (a), (b) or (c).