A process for the processing of an undried particulate polymer or polymer mixture by means of a single- or multiscrew extruder comprising a barrel comprising one or more screws, a feed section intended for the polymer and provided on the barrel and, provided on the barrel, a melting region in which the polymer or polymer mixture melts, where the undried polymer or polymer mixture introduced by way of the feed section into the barrel is devolatilized in at least one vacuum devolatilization region downstream of the feed section and upstream of the melting region in the barrel.

An extruder configured to extrude a solid raw material containing moisture includes a barrel, a hopper coupled to one side of the barrel, a discharge port, a screw, vent disposed between the hopper and the discharge port to discharge vapor generated within the barrel; and a heater mounted on the barrel to heat the raw material. Raw material introduced into the barrel through the hopper is heated by the heater while being transferred within the barrel through the screw. A kneading zone, in which raw materials transferred by the screw threads are compressed, is formed on the screw. Since the raw material is melted within the barrel, a heating temperature of the heater and an axial rotation speed of the screw are controlled so that a sealing membrane that shields an inner transverse section of the barrel is formed from the liquid raw material in the kneading zone.

An extruder is provided with: a screw rotationally driven about the axis by a first motor; a barrel having a screw hole into which the screw is inserted and a de-airing port configured to discharge air inside the screw hole; a filter configured such that a part thereof faces the de-airing port of the barrel; and a filter-driving mechanism configured to move the filter to shift the part of the filter facing the de-airing port.