The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 26, 1998
Filed:
Apr. 01, 1997
Manfred Urban, Wiesbaden, DE;
Dieter Schnaitmann, Eppstein, DE;
Hoechst Aktiengesellschaft, Frankfurt, DE;
Abstract
Process for preparing linear unsubstituted .beta.-phase quinacridone pigments A process for preparing linear unsubstituted .beta.-phase quinacridone pigments or pigment preparations, which comprises a) 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.degree. C., preferably from 60.degree. to 105.degree. C., to form the crude quinacridone pigment which is predominantly in the .alpha.-phase, c) then heating the crude .alpha.-phase quinacridone pigment to a temperature between 120.degree. and 200.degree. 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 .beta.-phase pigment, and d) subjecting the coarsely crystalline crude .beta.-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 .beta.-phase pigment; e) or subjecting the finely divided .beta.-phase prepigment obtained in d) to a finish treatment in the presence of solvents, and then isolating the pigment.