Process and apparatus for extruding plastic and similar materials

摘要

Extruding apparatus comprises a first screw extruder feeding into the inlet of a second screw extruder, such inlet being located at an intermediate position between the driving means and the discharge of the second extruder. Degassing means which applies a vacuum to the material fed into the second extruder tends to draw off particles of material entrained in the gas which is drawn off. The screw of the second extruder has a first screw portion which acts in a direction to propel the main mass of material from the inlet to the discharge of the second extruder and a second screw portion which acts in the opposite direction to propel the drawn off material from the inlet to an outlet which is located between the inlet and the driving means and which opens into a vacuum chamber. A third screw portion located between the outlet and the driving means acts in the same direction as the first portion and hence toward the outlet.