Process for preparing linear unsubstituted .beta.-phase quinacri

Details Process for preparing linear unsubstituted .beta.-phase quinacri Process for preparing linear unsubstituted .beta.-phase quinacri

1997-04-01

1998-05-26

Bell, Mark L.

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

106495, 546 49, 546 56, C09B 4800

Patent

active

057558744

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.

REFERENCES:
patent: 2844485 (1958-07-01), Struve
patent: 2969366 (1961-01-01), Griswold et al.
patent: 5062577 (1991-11-01), Schmitt et al.
patent: 5591258 (1997-01-01), Urban et al.

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