Abstract: A process for the devolatilization of a thermoplastic polymer containing gaseous impurities in an apparatus having a melting zone, a mixing zone, and a reduced pressure zone, comprising:(a) (i) adding a granular blowing agent directly or via a masterbatch to the polymer prior to the introduction of the polymer into the melting zone, said blowing agent being added in an amount of about 1 to about 4 percent by weight based on the weight of the polymer or (ii) adding a gaseous blowing agent to the mixing zone;(b) melting the polymer in the melting zone;(c) mixing the molten polymer and blowing agent in the mixing zone under sufficient pressure to maintain the blowing agent in the mixture;(d) at a temperature sufficient for decomposition or expansion, (i) decomposing the granular blowing agent in the mixing zone and/or in the reduced pressure zone or (ii) expanding the gaseous blowing agent in the reduced pressure zone wherein the blowing agent in its decomposed or expanded state develops froth cells in the molte

Abstract: The present invention teaches a method for reducing the number and size of polymeric gels in a polypropylene blend by filtering the blend through multiple filter screens during the extrusion of the blend.