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United States Patent 4280802
Douris , ê et al. July 28, 1981

Screw-type extruder for polyvinylidene fluoride filaments

Lang , Ê et al. July 28, 1981

Abstract

An apparatus for the continuous manufacture of filaments from polyvinylidene fluoride includes a screw extruder with a single-spindle screw surrounded by a coaxial barrel with a feed zone, a compression zone, a metering zone, and a mixing head zone for the plasticizing of the polyvinyldene fluoride and with a die outlet tool for shaping the filaments. The compression ratio of the screw is 1:1.2 to 1:2.5, and the screw is provided with single-flight and double-flight sections of identical pitch in alternating succession in the region of the compression zone. The mixing head zone is fashioned as alternatingly successive mixing zones and shear zones, of which there are provided, respectively, two to four zones and preferably three zones.