Patent ID: 6998081

Claim:
A method of producing polypropylene tape fibers comprising the sequential steps of (a) extruding a heated formulation of polypropylene comprising at most about 2000 ppm, preferably at most about 1500 ppm, more preferably at most about 1000 ppm, and most preferably below about 800 ppm, of a nucleator compound into a film or tube; (b) immediately quenching the film or tube of step “a” to a temperature which prevents orientation of polypropylene crystals therein; (c) slitting said film or tube with cutting means oriented longitudinally to said film or tube thereby to produce individual tape fibers therefrom; (d) mechanically drawing said individual tape fibers at a draw ratio of at least 5:1 while exposing said fibers to a temperature of at between about 250 and about 360° F.; (e) heat setting said tape fibers at a temperature in excess of the drawing temperature.