Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work – To degas or prevent gas entrapment
Patent
1974-06-07
1976-11-16
Roberts, Edward L.
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
To degas or prevent gas entrapment
264349, 425203, 259191, B29B 104, B29B 106
Patent
active
039925005
ABSTRACT:
A rotary screw extruder and a method are provided to both devolatilize and dry plasticized resinous hygroscopic materials during extrusion thereof into a finished product of indefinite length. The extruder includes a screw having three successive pumping sections and a pair of vent sections. Each vent section separates two of the successive pumping sections. The first pumping section meters plasticized material throughflow. The intermediate pumping section has partially full channels that permit a continuous, helical passage to interconnect the two vent sections. The partially full channels establish a free surface which promotes devolatilization and drying. The third pumping section pressurizes the devolatilized and dried plasticized material for extrusion through a conventional die orifice. The devolatilizing and drying method begins by controlling the flow rate of plasticized material into a gas removal zone. The gas removal zone is provided with a flow capacity exceeding the controlled flow rate of plasticized material so that a helical, free surface exists throughout the gas removal zone. Each end of the gas removal zone is connected to a reduced pressure source. The plasticized material is worked as it goes through the gas removal zone to heat the material, to promote drying and devolatilization thereof, and to maintain a uniform flow rate.
REFERENCES:
patent: 3023456 (1962-03-01), Palfey
patent: 3367635 (1968-02-01), Gresch
patent: 3376603 (1968-04-01), Colombo
Kruder George A.
Nichols Russell J.
Cantor Alan
Koehring Company
Roberts Edward L.
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