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:
Apr. 30, 1991
Filed:
Oct. 10, 1989
Konrad Opitz, Liederbach, DE;
Marcos Segal, Suzano, BR;
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
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,