Extruder apparatus and process for compounding thermoplastic resin and fibres

Apparatus for compounding reinforcing fibers with a thermoplastic resin comprising:

• a source of supply of thermoplastic resin pellets;
• a resin extruder having an inlet for receiving thermoplastic resin pellets from said source of supply, an outlet, an elongated, rotatable extruding screw extending between said inlet and said outlet;
• pellet handling means for conveying thermoplastic resin pellets from said source of supply thereof into said resin extruder inlet, whereby thermoplastic resin pellets are mechanically pumped by said resin extruder screw from said inlet to said outlet and are thereby heated and melted;
• a compounding extruder comprising a single, continuous, straight barrel and an elongated, rotatable, power screw extending continuously therein between an inlet end and a discharge end of said barrel, said barrel having first and second inlet ports on said inlet end communicating with said power screw, said second inlet port being continuously connected in fluid flow relation to said outlet of said resin extruder for receiving molten thermoplastic resin therefrom at a location along said elongated power screw downstream from said first inlet port, and between said first inlet port and said discharge end of said compounding extruder barrel, and said power screw having substantially continuous thread means of generally helical configuration;
• a converging, flow restricting passage at said discharge end of said barrel of substantially less diameter than the diameter of said barrel;
• a source of supply of discrete, predetermined lengths of reinforcing fibers connected to said first inlet port of said compounding extruder, and means for feeding said fibers into said first inlet port, whereby the fibers are heated and mechanically worked by said power screw of said compounding extruder before coming into mixing contact with molten, thermoplastic resin, and the fibers are continuously confined under pressure within said screw barrel by said thread means and advanced by said thread means of said power screw as a continuous mat past said second inlet port for thorough initial wetting by molten thermoplastic resin, and said fibers and said thermoplastic resin intermix in said power screw to form a homogeneous molten mass of thermoplastic resin having discrete, discontinuous lengths of reinforcing fibers randomly and homogeneously dispersed therein.