Patent ID: 6878327

Claim:
In a method for the production of polypropylene fibers, the steps comprising: (a) providing a propylene polymer comprising isotactic polypropylene produced by the polymerization of propylene in the presence of an isospecific metallocene catalyst; (b) heating said polymer to a molten state and extruding said polymer at a temperature within the range of about 170°-210° C. to produce a fiber preform; (c) spinning said fiber preform with a spinning speed of at least 200 meters per minute; (d) cooling said fiber preform; and (e) drawing said fiber preform to produce a fiber at a draw ratio within the range of 1.5-4.0 within which the shrinkage of said fiber over said range of draw ratio remains within a variance range of no more than ±25% of the median of said shrinkage factor over said draw ratio range.