Method for manufacturing polycarbonate for optical use

• US 6,197,917 B1
• Filed: 08/18/1999
• Issued: 03/06/2001
• Est. Priority Date: 09/02/1998
• Status: Expired due to Term

• Current Assignee: SABIC Global Technologies BV (Government of Saudi Arabia)
• Original Assignee: General Electric Company
• Inventors: Omori, Satoru, Shimoda, Tomoaki, Sato, Ryozo, Kimura, Takato, Kanezawa, Akio
• Primary Examiner(s): Boykin, Terressa M.
• Application Number:
  US09/376,450
• Time in Patent Office: 566 Days
• Field of Search: 528/196, 528/198
• US Class Current: 528/196
• CPC Class Codes: C08G 64/307 and phenols

Abstract

The specification provides a method for the manufacture of a high-quality optical polycarbonate that contains few inorganic or organic impurities or other microparticles, and that has a superior hue. Specifically, the specification provides a method for the manufacture of a polycarbonate by the melt polycondensation of a bisphenol and a carbonic diester, wherein the molten mixture of a bisphenol and a carbonic diester is filtered with a membrane filter made of a fluororesin, after which melt polycondensation is conducted.

Claims

1. A method for manufacturing an optical polycarbonate, by the melt polycondensation of a bisphenol and a carbonic diester, wherein

a molten mixture of a bisphenol and a carbonic diester is first filtered through a membrane filter made of a fluororesin, and melt polycondensation is subsequently conducted.

2. A method for manufacturing an optical polycarbonate as defined in claim 1, wherein said membrane filter made of a fluororesin has an absolute filtration precision of 1.0 μ

m or less.

3. A method for manufacturing an optical polycarbonate as defined in claim 1 wherein molten mixture of a bisphenol and a carbonic diester is obtained by first separately filtering a bisphenol that is in a molten state and a carbonic diester that is in a molten state, and then mixing the bisphenol and the carbonic diester.

4. A method for manufacturing an optical polycarbonate as defined in claim 3, wherein the filtration of the bisphenol that is in a molten state and the carbonic diester that is in a molten state is carried out using a filter having an absolute filtration precision of 20 μ

m or less.

5. A method for manufacturing an optical polycarbonate as defined in claim 1, wherein the polycarbonate that is the reaction product of the melt polycondensation is further filtered while still in a molten state.

6. A method for manufacturing an optical polycarbonate as defined in claim 5, wherein the filtration of the polycarbonate reaction product is carried out using a filter having an absolute filtration precision of 50 μ

m or less.

7. A method for manufacturing an optical polycarbonate as defined in claim 1 wherein the bisphenol is bisphenol A.