| 摘要 |
705,789. Extruding polyamide resin. DU PONT DE NEMOURS & CO., E. I. April 16, 1952 [May 16, 1951], No. 9566/52. Class 87 (2) Molten synthetic linear polyamide resin is forced through an elongated mould or die 1 having a length at least 25 times its crosssectional diameter, the cross-section of the die being substantially uniform throughout its length the shaping surfaces of the die being separated from the resin by a layer 3 of polytetrafluoroethylene. The die is cooled by a jacket 2; and the resin issues from the die as a solid rod 4 (or tube or wire coating). A braking force is applied on the rod as it issues, by means of brakes 5. whereby a moulding pressure is developed in the resin in the die. Each brake includes a brake pad 6 of polytetrafluoroethylene which is adjustable by means of a set screw 7. Alternatively. the brakes may be spring-loaded frictional resistanceplates or a hydraulically-operated plunger having a compensating metering device designed to maintain a 'constant pressure against the shape being extruded. The P.T.F.E. layer 3 may be a thin adherent coating on the die, or may be in the form of a film, tape or tube of P.T.F.E. which is inserted into the die as an interlayer or adhered to the die. The resin is forced through the die by means of a screw, and a heater may be placed at the entrance end of the die to keep the resin molten long enough to take the shape of the die. Specifications 461,236, 461,237 and 474,999, [all in Group IV], are referred to. ,
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