1281305 Stretching filaments SNIA VISCOSA SOC NAZIONALE INDUSTRIA APPLICAZIONI VISCOSA 3 Dec 1970 [4 Dec 1969] 57397/70 Heading B5B A method of continuously spinning and stretching synthetic filaments in a continuous operational sequence comprises the steps of extruding said filaments from a spinneret, cooling and conditioning the extruded filaments, and subjecting said filaments to at least one mechanical stretching operation between at least two drawing devices adapted to impart different linear speeds to said filaments, wherein after said cooling and conditioning steps and before said filaments are engaged by the first of said drawing devices, said filaments are bent at least once and given a preliminary stretch. . In apparatus as shown, filaments 14, of a synthetic thermoplastic material, especially polyester filaments, are extruded from spinneret 14 and passed through blowing box 16 and elongated chamber 18 wherein they are cooled and conditioned, and passed through thread guides 22, and sizing rollers 24 and 26, on their way to conventional feed and draw godets 28 and 30. Prior to stretching being effected by godets 28 and 30, the filaments are given a preliminary stretch by passage around device Z, comprising a pair of small cylinders 36 and 38, shown more clearly in Fig. 2. These cylinders are located in such a manner as to force the filaments to follow a path including a number of bends, in particular two oppositely directed bends as shown by dot and dash lines in Fig. 2, as well as to exert a frictional resistance on the running filaments in order to generate a tension slightly greater than the post-spinneret tension, at the small filament length S between the device Z and the upstream godet 28. Suitably, the tension in the filaments at point X is about 0À5 g.p.d. which is increased by passage through device Z so that the tension at point S is about 0À6 to 0À7 g.p.d. The small cylinders 36 and 38 may have their surfaces treated so as to provide the required frictional resistance. As shown, the filaments may be successively bent with decreasing radiiof curvature, and in general where the filaments are successively bent in opposite directions, the radii of curvature should have a ratio in the range of 1 : 2 to 2 : 1. Desirably, the filaments are bent at least once with a radius of curvature in the range of 10 to 21 mm. and with an angular amplitude in the range of 20 to 130 degrees. The use of the apparatus enables spinning speeds to be raised to 800 to 1000 metres per minute at take-up.
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