Extrusion method for making polycarbonate
US6420512B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 2001 |
| Grant date | Jul 16, 2002 |
| Priority date | — |
| Expiry date | Jul 24, 2021 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC08G64/307
- WIPO fieldMacromolecular chemistry, polymers
- WIPO sectorChemistry
Abstract
Extrusion of a mixture of an ester-substituted diaryl carbonate, such as bis-methyl salicyl carbonate, a dihydroxy aromatic compound such as bisphenol A and a transesterification catalyst such as tetrabutyl phosphonium acetate (TBPA) affords polycarbonate having a weight average molecular weight of greater than 20,000 Daltons. The extruder is equipped with one or more vacuum vents to remove by-product ester-substituted phenol. Similarly, a precursor polycarbonate having ester-substituted phenoxy endgroups, for example methyl salicyl endgroups, when subjected to extrusion affords a polycarbonate having a significantly increased molecular weight relative to the precursor polycarbonate. The reaction to form a higher molecular weight polycarbonate may be catalyzed by residual transesterification catalyst present in the precursor polycarbonate, or by a combination of any residual catalyst and an additional catalyst such as TBPA introduced in the extrusion step. Fries rearrangement products are not observed in the product polycarbonates.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.