Reducing ionic impurities content in polycarbonate resins

摘要

An aromatic polycarbonate composition having less than 300 parts per billion each of ionic impurities, particularly sulfate and chloride ions is obtained by devolatilizing the ionic impurities from a polycarbonate composition employing an aqueous medium of about 1% by weight based on the weight of the polycarbonate composition. Preferably the devolatilizing is carried out in an extruder during compounding the polycarbonate composition and preferably under a vacuum. Also, the extruded strands of polycarbonate resin are quenched in a water bath having a sulfate and chloride ion content of less than 300 ppb each.