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United States Patent 4255379
Douris , ê et al. March 10, 1981

Injection molding using screw for processing heat sensitive polymeric materials

Frankland, Jr. March 10, 1981

Abstract

An injection molding screw for use in processing heat sensitive polymeric materials and a process for plasticating such materials. The screw has an inlet end, a discharge end, means for mounting a backflow valve on the discharge end, and at least one section which applies high shear and high compression to the polymeric material and controls the material flow rate. A flighted screw section is disposed between the high shear and high compression section and the discharge end; that screw section includes means for decompressing the polymeric material and pumping it to the discharge end of the screw in the decompressed state at a rate at least equal to the pumping rate of the zone of high shear and high compression.