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. 10, 1991
Filed:
Mar. 09, 1990
Applicant:
Inventors:
Fusaji Shoji, Yokohama, JP;
Nobuo Aoki, Gunma, JP;
Jun Kurita, Shibukawa, JP;
Tsuyoshi Aoyama, Shibukawa, JP;
Toshiyuki Kiriyu, Gunma, JP;
Yoshinori Matsuzaki, Yokohama, JP;
Assignees:
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
C07D / ; C07C / ;
U.S. Cl.
CPC ...
549241 ; 562480 ; 562483 ; 562485 ; 562488 ;
Abstract
Highly pure 3,3',4,4'-biphenyltetracarboxylic acid (BPTA) and dianhydride thereof (BPDA) are produced by heating crude BPTA to give BPDA, treating the BPDA with hot water to give highly pure BPTA, and in the case of highly pure BPDA, heat treating the pure BPTA to give highly pure BPDA.