Removal of volatile material from screw feed extruder - by injecting gas into high press. zone of plastic melt and removing it from low press. zone

摘要

Plastic melt (e.g. polyolefine, polystyrene, polypropylene) is fed by a feed screw through a barrel to an extrusion plate through which the melt is extruded, and the barrel has pref. two sepd. seals which delimit a purifying region in which the melt in the upstream zone in at a low press. and the melt in the downstream zone is at a low press. A gas (e.g. a vapour) is fed into the high press. zone and flows through the melt to the low press. zone where it is removed, the gas absorbing the volatile material (e.G. solvent) during its passage through the melt. Pref. water is injected into the barrel through an inlet downstream of the purifying zone and is removed as steam through an outlet downstream of the inlet. Removal of almost all of the volatile material is achieved.