Method of manufacturing discrete fiber reinforced, plastic tube and apparatus therefor

摘要

A method and apparatus for making multi-layered plastic tube reinforced with fibers by a co-extrusion process. The method and apparatus provide more specifically a multi-layered plastic tube with an intermediate layer thereof having discrete fibers where at least a major portion of the fibers is oriented to extend predominantly in a general direction lying between the circumferential and the longitudinal axis of the tube with the orientation of the fibers being generally the same throughout the thickness of the intermediate layer. In one embodiment, the method comprises (a) introducing a first plastic material in an upstream portion of an annular die channel; (b) introducing a second plastic material filled with fibers in the upstream portion and around the whole of the first material; (c) introducing a third plastic material in the upstream portion and around the whole of the second material; and co-extruding the materials through a downstream portion of the annular die channel which is divergent diametrically in the downstream direction.