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:
May. 19, 1992
Filed:
Dec. 03, 1990
Mituhiko Masumoto, Osaka, JP;
Mitsubishi Gas Chemical Co., Inc., Tokyo, JP;
Abstract
A process for producing a dichloroformate of a tetrahalogenated bisphenol by an interfacial process in a high yield and a high content and a process for producing an aromatic copolycarbonate oligomer by a solution process using the resulting dichloroformate monomer are disclosed. The first process comprises adding a catalyst for chloroformate formation to a tetrahalogenated bisphenol in an amount of from 1.times.10.sup.-4 to 1.times.10.sup.-1 mol per mol of the bisphenol and consecutively adding a halogenated carbonyl to effect reaction while controlling the pH of the reaction system between 10 and 12 by consecutive addition of a basic inorganic compound to the reaction system. The copolycarbonate oligomer obtained using the dichloroformate monomer has high alternating regularity.