Preparation of linear, unsubstituted quinacridone pigments of the ଲ-phase Patent #: 5591258
ApplicationNo. 834725 filed on 04/01/1997
US Classes:106/497, Quinacridone pigment or derivative106/495, Quinacridone pigment or derivative546/49, Two ring nitrogens in the pentacyclo ring system (e.g., quinacridones, etc.)546/56Three or more ring carbons of the pentacyclo ring system are substituted (e.g., substituted quinacridones, etc.)
ExaminersPrimary: Bell, Mark L.
Assistant: Hertzog, Scott L.
Attorney, Agent or Firm
Foreign Patent References
International ClassC09B 048/00
Foreign Application Priority Data1996-04-02 DE
AbstractProcess for preparing linear unsubstituted ଲ-phase quinacridone pigments A process for preparing linear unsubstituted ଲ-phase quinacridone pigments or pigment preparations, which comprisesa) cyclizing 2,5-dianilinoterephthalic acid in polyphosphoric acid or polyphosphoric ester with a phosphorus pentoxide content of at least 84% by weight to form the quinacridone,b) subsequently hydrolyzing this quinacridone with water or with an aqueous mineral acid solution, preferably orthophosphoric acid solution, at a temperature of at least 40° C., preferably from 60° to 105° C., to form the crude quinacridone pigment which is predominantly in the -phase,c) then heating the crude -phase quinacridone pigment to a temperature between 120° and 200° C. in the presence of a from 0.1 to 3% strength by weight, preferably from 0.2 to 2% strength by weight, inorganic base in water and alkali-stable organic solvents, for the change of phase into coarsely crystalline crude ଲ-phase pigment, andd) subjecting the coarsely crystalline crude ଲ-phase quinacridone pigment, for the fine division to form a pigment or prepigment, to dry or wet milling; and then isolating the resulting finely divided ଲ-phase pigment;e) or subjecting the finely divided ଲ-phase prepigment obtained in d) to a finish treatment in the presence of solvents, and then isolating the pigment.