Patent ID: 7858008

Claim:
A method of making a fiber-reinforced poly(vinyl chloride)-containing article, comprising the steps of: (a) feeding granules of poly(vinyl chloride) reinforced with fibers into a two-stage, single-screw extrusion apparatus that has mixing pins at the end of the first stage and a vent only at the beginning of the second stage for devolatilization of outgasses during extrusion; and (b) extruding the fiber-reinforced poly(vinyl chloride) through a profile extrusion die, wherein the granules contain fibers in an amount up to about 30 percent by weight of the article, wherein between step (a) and step (b) the following steps occur in rapid succession: (1) compression of the fed granules in a transition zone of the first stage of the screw along with melting of the compressed material at a barrel/material interface, (2) continued melting without decompression or devolatilization along with dispersive mixing in a metering/mixing zone in the first stage of the screw, (3) decompression for the first time of compressed and melted/partially melted material at the beginning of the second stage of the screw, (4) devolatilization of the decompressed material for the first time through the only vent to remove volatiles including moisture, and (5) build-up of melt pressure and conveying of the devolatilized melt to the die, and wherein the fiber-reinforced poly(vinyl chloride) extruded through the profile die has a ratio of actual specific gravity to theoretical specific gravity that ranges from about 0.90 to about 0.99.