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:
Jul. 08, 1986
Filed:
Jul. 05, 1984
Applicant:
Inventors:
Siegfried Schiessler, Bad Soden am Taunus, DE;
Ernst Spietschka, Idstein, DE;
Assignee:
Hoechst Aktiengesellschaft, Frankfurt am Main, DE;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
C07D / ;
U.S. Cl.
CPC ...
549232 ; 562480 ; 562485 ; 562486 ;
Abstract
Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid (called 'NTC' below) and its 1,8-monoanhydride in a high degree of purity, which comprises dissolving impure NTC or impure NTC-1,8-monoanhydride as the tetra-alkali metal salt of NTC in water in known manner, removing any insoluble impurities present, bringing the clarified solution to a pH value of 4-5 below 45.degree. C., separating off the di-alkali metal salt of NTC which thereby crystallizes out and converting the latter into free NTC or into free NTC-1,8-monoanhydride by treatment with a strong acid at 20.degree. to 100.degree. C.