Method for producing polycarbonate

Patent metadata

Field	Value
Publication number	US-9988490-B2
Application number	US-201515314406-A
Country	US
Kind code	B2
Filing date	May 28, 2015
Priority date	May 30, 2014
Publication date	Jun 5, 2018
Grant date	Jun 5, 2018

Abstract

Provided is a method of producing a polycarbonate that enables efficient drying of a polycarbonate powder and has no risk of deteriorating the quality of a polycarbonate molded article to be obtained. The method of producing a polycarbonate includes: a step of causing an alkali aqueous solution of a dihydric phenol and phosgene to react with each other in the presence of an organic solvent to produce an organic solvent solution containing a polycarbonate; a powdering step of powdering the organic solvent solution containing the polycarbonate to provide a polycarbonate powder; and a pre-drying step of drying the polycarbonate powder to remove the remaining organic solvent, in which a drying temperature in the pre-drying step is set to a temperature lower than the glass transition temperature of the polycarbonate containing 1.5 mass % of the organic solvent by from 5° C. to 15° C.

First claim

The invention claimed is:

1. A method of producing a polycarbonate, comprising:
a step of causing an alkali aqueous solution of a dihydric phenol and phosgene to react with each other in the presence of an organic solvent to produce an organic solvent solution containing a polycarbonate;
a powdering step of powdering the organic solvent solution containing the polycarbonate to provide a polycarbonate powder; and
a pre-drying step of drying the resultant polycarbonate powder to remove the remaining organic solvent,
wherein a drying temperature in the pre-drying step is set to a temperature lower than a glass transition temperature of the polycarbonate containing 1.5 mass % of the organic solvent by from 5° C. to 15° C.

2. The method of producing a polycarbonate according to claim 1 , wherein a content of the organic solvent in the polycarbonate powder obtained in the powdering step is from 10 mass % to 50 mass %.

3. The method of producing a polycarbonate according to claim 1 , wherein a content of the organic solvent in the polycarbonate powder after the pre-drying step is from 1 mass % to 3 mass %.

4. The method of producing a polycarbonate according to claim 1 , wherein the organic solvent is methylene chloride.

5. The method of producing a polycarbonate according to claim 1 , wherein the polycarbonate powder obtained in the powdering step has an average particle diameter of from 0.15 mm to 2.40 mm.

6. The method of producing a polycarbonate according to claim 1 , wherein the polycarbonate contained in the organic solvent solution has a viscosity-average molecular weight of from 8,000 to 35,000.

7. The method of producing a polycarbonate according to claim 1 , further comprising, after the pre-drying step, a post-drying step of drying the polycarbonate powder.

8. The method of producing a polycarbonate according to claim 7 , wherein a content of the organic solvent in the polycarbonate powder obtained after the post-drying step is set to 1,000 ppm by mass or less.

9. The method of producing a polycarbonate according to claim 7 , wherein a content of the organic solvent in the polycarbonate powder obtained after the post-drying step is set to 500 ppm by mass or less.

10. The method of producing a polycarbonate according to claim 7 , wherein a drying temperature in the post-drying step is set to a temperature lower than a glass transition temperature of the polycarbonate containing 1000 ppm by mass or less of the organic solvent by from 3° C. to 10° C.

11. The method of producing a polycarbonate according to claim 7 , wherein an average number of gels in a film measuring 10 cm by 30 cm, and having a thickness of 0.1 mm, the film being obtained by molding the polycarbonate powder obtained after the post-drying step, is 0.7 or less.

12. The method of producing a polycarbonate according to claim 1 , wherein the dihydric phenol is bisphenol A.

Assignees

• Idemitsu Kosan Co

Inventors

• Nagao Yukiko
• Takahashi Masayuki
• Mabuchi Kota

Classifications

• C08G64/24

  and phenols · CPC title

• C08J2369/00

  Characterised by the use of polycarbonates; Derivatives of polycarbonates · CPC title

• B29B9/12

  characterised by structure or composition · CPC title

• C08G64/406

  Purifying; Drying · CPC title

• B29B7/005

  for mixing in batches · CPC title