Removal of volatile substances from thermoplastic resins

摘要

A thermoplastic resin such as a styrene/maleic anhydride copolymer is treated to remove volatile impurities such as unreacted styrene by admixing with a chemical blowing agent and extruding under a vacuum. The chemical blowing agent is converted into an inert gas such as carbon dioxide during extrusion; the gas evolved is removed, together with the volatile impurities, through one or more vents in the extruder. The use of a chemical blowing agent, rather than the inert gas itself, permits the facile distribution of the CO2 stripping agent throughout the molten thermoplastic resin using commonly available extruders without the need for elaborate gas injection means.