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:
Dec. 24, 1991
Filed:
Oct. 26, 1989
Erwin Dietz, Kelkheim, DE;
Gustav Kapaun, Bad Soden am Taunus, DE;
Siegfried Schiessler, Bad Soden am Taunus, DE;
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Abstract
The conventional condensation of naphthalene-1,4,5,8-tetracarboxylic acid with 1,2-diaminobenzene gives the resulting naphthoylenebisbenzimidazole isomers together in the cis and trans form. It is desirable to shift the isomer ratio of the mixture obtained toward the desirable trans product and to reduce the amount of cis product obtained. It is also desirable to develop a process of preparation which optimizes the yield and improves the waste water situation. This object is achieved according to the invention by subjecting virtually stoichiometric amounts of the starting compounds to a precondensation at 60.degree. to 110.degree. C. in an aqueous medium and then completing the condensation in the aqueous medium in a second stage at 130.degree. to 180.degree. C.