Patent ID: 8242231
Filing Date: 2012-08-14
Classification: C08G,Y02P

Abstract:
1. An interfacial process for producing a polycarbonate resin from a dihydric phenol, a carbonate precursor, and a monophenolic chain terminator using an amine coupling catalyst which process comprises the steps of: (a) reacting the carbonate precursor and the dihydric phenol using a two-phase reaction mixture to form carbonate oligomers; the reaction mixture comprising an aqueous, alkaline phase and an immiscible organic phase, with the carbonate precursor being dissolved in an organic phase and a salt of the dihydric phenol and a salt of the monophenolic chain terminator dissolved in the aqueous phase; (b) subsequently polymerizing the carbonate oligomers in the presence of a coupling catalyst to form a polycarbonate resin; (c) separating the aqueous and organic phases; wherein the organic phase comprises the coupling catalyst and polycarbonate resin; (d) treating the separated organic phase with an acidic wash water solution to remove amine coupling agent by forming a salt of the coupling catalyst which is soluble in the acidic wash water solution; (e) recovering the polycarbonate resin; wherein the improvement comprises (i) treating the acidic wash water solution comprising the salt of the coupling catalyst with a basic material to adjust the solution pH to at least 12 producing an alkaline wash water solution comprising the coupling catalyst; and (ii) recycling said alkaline wash water solution comprising the coupling catalyst back into the polymerization step (b).