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:
Mar. 11, 1997
Filed:
Apr. 07, 1995
Tsutomu Yamato, Hyogo, JP;
Yasuhiro Oshino, Hyogo, JP;
Yutaka Fukuda, Hyogo, JP;
Tatsuya Kanno, Hyogo, JP;
Takaaki Kuwana, Hyogo, JP;
Daicel Chemical Industries, Ltd., Sakai, JP;
Abstract
In a process for producing a polycarbonate by subjecting a dihydroxy compound and a diester of carbonic acid to melt polycondensation through transesterification, after a polycarbonate prepolymer is prepared in the first-stage reaction, polycondensation is conducted as the second-stage reaction in a residence time in the range of from 15 to less than 60 min or through the use of at least one paddle-type self-cleaning twin-screw extruder This process enables a colorless, transparent polycarbonate having a high molecular weight to be produced at a high efficiency on an industrial scale.