Abstract: An extruder of the degassing and modification type, comprising a cylinder having at least one hopper orifice and at least one vent opening, and two adjoining screws mounted in the cylinder to be rotated in opposite directions. Each of the screws are formed by at least one feed section to be disposed below the hopper orifice, a kneading section, at least one mixing section to be disposed below the vent opening and a pressurizing section, and one of the screws is further formed by a metering section in series with the pressurizing section. Respective sections except for the kneading sections are generally formed from continuous flights and the flight angles are made different between the adjoining screws. The kneading sections are respectively provided with an adjusting ring and a gate ring arranged at a distance and a number of pins secured to the screws between the rings. Water may be introduced into the kneading section.