Improvements in the extrusion of organic thermoplastic materials

摘要

An extrusion apparatus has a screw 2 with a substantially uniform pitch and depth of flight from its feed end to at least the end of its melting zone and a passageway 4 in the screw, for the removal of volatile matter, the passageway being connected by an orifice or orifices to at least one of the spaces between the flights of the screw situated beyond the melting zone and before the zone at the delivery end of the screw, where the flow of plastic material along the screw is restricted. There may be more than one such screw, which may have cooling channels therein. The passageway 4 may be connected to a source of vacuum and the volatile matter may be condensed. The screw may have a notch in a flight (Fig. 2). The cylinder may be differentially heated. The apparatus is particularly useful for extruding thermoplastic materials containing water or organic solvents.