Apparatus for melt extruding fiberforming thermoplastic polymers

1,004,914. Extruding thermoplastic materials; melt-spinning apparatus. E. I. DU PONT DE NEMOURS & CO. May 28, 1964 [May 28, 1963], No. 22169/64. Headings B5A and B5B] An apparatus for melt extruding films and fibres of thermoplastic synthetic polymers such as polyamides, polyesters and polyolefins, and copolymers and blends thereof comprises a casing 10 (not shown) having a smooth cylindrical bore containing an extrusion screw 11 wherein the trailing side of the leading flight of any two adjacent flights and the root of the screw between said flights merge to form a single quasi conical helical surface 113 which tapers rearwardly at an angle of 3 to 8 degrees with respect to the axis of the helix, the radius of the land 111 of the helical flight being constant throughout the helix and differing from the radius of the cylindrical bore so as to provide a total clearance volume between the screw and casing for the entire length of the apparatus, exclusive of a conical tip portion, equal to 5 to 10% of the volume of the empty casing. The leading face 112 of each flight may be flat as shown or concave. In the apparatus illustrated in Fig. 1 (not shown), the screw feeds the molten thermoplastic material through an insulated conduit to metering pumps which force it through filament forming spinning heads.