Process for preparing linear unsubstituted ଲ-phase quinacridone pigments
Patent 5755874 Issued on May 26, 1998. Estimated Expiration Date: 
April 1, 2017. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
April 1, 2017. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2844485 2969366 Agitator mill Preparation of linear, unsubstituted quinacridone pigments of the ଲ-phase Patent #: 5591258 InventorsAssigneeApplicationNo. 834725 filed on 04/01/1997US 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 FirmForeign Patent References
International ClassC09B 048/00Foreign Application Priority Data1996-04-02 DEAbstractProcess 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. |
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