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:
Sep. 19, 1995
Filed:
Apr. 06, 1994
Otto Arndt, Hofheim, DE;
Hoechst AG, Frankfurt, DE;
Abstract
The present invention relates to a process for the preparation of crystalline, salt-free, chlorine-substituted 3-nitrobenzenesulfonic acid hydrates from sulfonation mixtures containing chlorine-substituted 3-nitrobenzenesulfonic acid, in which the sulfonation mixture is mixed with from 8 to 25% strength by weight aqueous sulfuric acid at from 40.degree. C. to 100.degree. C., the resulting suspension is cooled to from 5.degree. C. to 20.degree. C., the precipitate is filtered off and dissolved with water at from 30.degree. C. to 100.degree. C., filtration is carried out if desired, the solution is cooled to from 5.degree. to 40.degree. C. and filtered, and the sulfuric acid-containing filtrate is recycled if desired.