Verfahren und Vorrichtung zur Herstellung von Stapelfasern aus thermoplastischen Kunststoffen

摘要

Staple fibre is produced by drawing stand(s) of polymer from jet orifices and immediately fibrillating them by a gas stream. The molten polymer is pre-oriented by at least 25% pref. at least 50% before drawing from the orifices. The strand is brought to a temp. at which the polymer viscosity is 102-106 pref. 103-105 cP. Its cross section has a hydraulic radius r of 0.05-1, pref. 0.1-0.5 mm. The strand surface under these conditions is subjected to a tension gamma in the flow direction of 104-109 pref. 105-108 kp/m2, corresponding to a shear speed and of 102-107, pref. 104-106 sec.-1. The strand is subjected to these conditions for a time t of 10-3-1, pref. 10-2-10-1 sec. corresponding to an orientation length of 1-100, pref. 2-30 min. The relations gamma.t.r/l = 1-103, pref. 10-100 kp. sec./m2, and gamma.l.r.2=10-10-4, pref. 1-10-3 m.kp, hold. The strand is fibrillated by a gas, vapour or fluid stream pref. outside the nozzle and is partly cooled by auxiliary gas. Fibrillation is at 5-100 mm from the jet end. The main gas stream acts on the strand at an angle of 5-85 degrees pref. 10-45 degrees, a speed 50-700, pref. 100-400 m/sec., and a temp. of 0-700 degrees C, pref. 20-200 degrees C.