Continuous process for the preparation of bisazo pigment mixture

Details Continuous process for the preparation of bisazo pigment mixture Continuous process for the preparation of bisazo pigment mixture

1992-06-19

1993-03-02

Cintins, Marianne M.

Organic compounds -- part of the class 532-570 series

Organic compounds

Azo

534576, C09B 35037, C09C 712

Patent

active

051910705

ABSTRACT:
A continuous process for the preparation of a bisazo pigment mixture of at least two different bisazo pigments of the general formula ##STR1## wherein R.sub.1 and R.sub.2 each may be independent of themselves and are each independently of one another hydrogen, chloro, methyl or methoxy, which bisazo pigments differ from each other in at least one of the substituents R.sub.1 or R.sub.2, by simultaneously coupling a bisdiazotized diaminodiphenyl (A) of formula ##STR2## and a mixture (B) of two coupling components of formula ##STR3## wherein R.sub.1 and R.sub.2 are each independently of the other hydrogen, chloro, methyl or methoxy which coupling components differ from each other at least one of the substituents R.sub.1 or R.sub.2, which process comprises mixing continuously the aqueous acidic solution of at most pH 4 of the bisdiazotized diaminodiphenyl (A) with an aqueous alkaline solution of not lower than pH 12 of the mixture (B) of at least two coupling components of formula III which differ from each other as described above in a molar ratio A:B of 1:2.1 to 2.3, keeping the pH in the range from 5.5 to 6.5 by regulating the educt feed, reacting the educts for an average residence time of 1 to 5 minutes, and isolating the resultant pigment mixture by filtration.
The pigment mixtures obtained by this process are distinguished by excellent pigment properties and by surprisingly good rheological properties.

REFERENCES:
patent: 3529984 (1970-09-01), Bandel et al.
patent: 3533818 (1970-10-01), Bandel et al.
patent: 3759731 (1973-09-01), Kuhne et al.
patent: 4159264 (1979-06-01), Hamilton et al.
patent: 4454067 (1984-06-01), Behringer et al.
patent: 4720541 (1988-01-01), Rieper et al.
patent: 4920206 (1990-04-01), Behringer et al.

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