Process for preparing a stabilized composition of a lithium azo

Details Process for preparing a stabilized composition of a lithium azo Process for preparing a stabilized composition of a lithium azo

1989-10-10

1991-04-30

Higel, Floyd D.

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

Organic compounds

Azo

534581, 534582, 534642, 8549, C09B 6251, C09B 62507, C09B 6726, D06P 1384

Patent

active

050119176

ABSTRACT:
A process for the preparation of a pH-stabilized, liquid, aqueous dyestuff composition of the lithium azo dyestuff of formula (1) ##STR1## which composition has an Na-content of less than 0.2% b.w., based on the lithium azo compound of formula (1), in which process the lithium salt of 4-(.beta.-sulfatoethylsulfonyl)-aniline is diazotized in a mineral acid aqueous solution or in a mineral acidic solution containing a watermiscible organic solvent by means of an essentially sodium-free derivative of nitrous acid as the diazotizing agent, such as nitrosyl sulfuric acid, and the diazotized aniline is coupled in said solution with the lithium salt of 1-hydroxy-7-acetylamino-naphthalene-3-sulfonic acid and a buffering substance for adjusting and maintaining the pH of the composition at a value between 3 and 6.5 is added to that solution subsequent to the above-mentioned diazotizing step or preferably during said or subsequent to said coupling step, the amount of the buffering substance added is from 0.5 to 5% b.w. of said composition,

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