ES302373A1 - Process for the stretching of polyamidic fibres - Google Patents

Abstract

A polycaproamide polymer having an intrinsic viscosity not less than 1À20, as determined in solution in m-cresol, is spun at a speed of at least 350 m./min., and the extruded filaments, which have a birefringence of at least 0À015, and preferably of from 0À015 to 0À035, are drawn in two or more steps, the draw ratio of the first stretching step for filaments having a birefringence of 0À015 being from 3À5 to 4, and that for filaments having a birefringence of 0À035 and above being from 2À5 to 3À5, the draw ratio of the first stretching step for filaments having a birefringence of 0À015 to 0À035 being obtained by interpolation from the accompanying diagram (Fig. 1). The starting yarn may be obtained by spinning a polymer having an intrinsic viscosity of 1À20 to 1À50 at a speed of 400 m./min. to 800 m./min., Figs. 2 and 3 (not shown), illustrate stretching apparatus. In Fig. 2, the first stage stretching is effected between rolls 11 and 19, suitably heated to 150 to 200 C. and especially to 170-185 C., and second stage stretching between rolls 19 and 21, roll 19 being heated. In Fig. 3, roll 19 is not heated but the threadline is heated by passage through heater 20, suitably heated to the same temperature as roll 19 in Fig. 2. Snubbing pins may be inserted between rolls 11 and 19, or rolls 19 and 21, if desired, and said pins may be held at room temperature or heated to 40-75 C. and preferably to above 60 C. Peripheral speeds of rolls 19 are between 80 and 400 m./min. and preferably 150 to 300 m /min for the apparatus of Fig. 2 and between 90 and 175 m./min. for the apparatus of Fig. 3. Filaments so made have enhanced tenacity and limited elongation and are especially suitable as tyre cord.