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. 15, 1987
Filed:
Sep. 02, 1986
Tsuneo Kosaka, Kurashiki, JP;
Yukio Sakai, Kurashiki, JP;
Mitsubishi Gas Chemical Company, Inc., Tokyo, JP;
Abstract
A process for preparing pyromellitic dianhydride by dehydration of pyromellitic acid is disclosed. The dehydration is conducted in solid state by indirect heating. The characteristic feature of the process is that when the most part of pyromellitic acid was converted to the dianhydride, the remaining pyromellitic acid is dehydrated while regulating the temperature of the heating medium between 200.degree. C. and 235.degree. C. By this process, pyromellitic dianhydride with excellent quality, good color and free flowing property can be obtained easily, smoothly, and rapidly. A very simple apparatus can be used in the process and the apparatus can be constructed from cheap materials.