Extruder of the degassing and modification type

In an extruder of the degassing and modification type wherein two adjoining screws are mounted in a cylinder so that they are parallel to each other and rotate in opposite directions, the improvement comprises:

• said cylinder having at least one hopper orifice and at least one vent opening at its upper part in order from the rear end;
• each of said adjoining screws being formed with at least one feed section, a kneading section, at least one mixing section and a pressurizing section in order from the rear end, whereby said feed and mixing sections are located substantially below said hopper orifice and said vent opening of said cylinder, respectively;
• one of said adjoining screws being further formed with a metering section in series with said pressurizing section;
• said feed, mixing pressurizing and metering sections of said adjoining screws are formed respectively from a substantially continuous flight having the same outer diameter and the directions of said flights of said respective sections being different between said adjoining screws;
• and
• each of said kneading sections of said adjoining screws being formed by an adjusting ring and a gate ring secured thereto at the rear and front ends, respectively, with a distance being left therebetween and a kneading means provided on said screw between said rings, whereby the outer diameter of said adjusting ring being substantially the same as that of said flight and the outer diameter of said gate ring being somewhat larger than that of said adjusting ring, and said adjusting and gate rings of said adjoining screws being transversely aligned so as to be substantially circumscribed with each other respectively.