Higher throughput in metallocene isotactic polypropylene fibers

In a method for the production of polypropylene fibers, the steps comprising

• a) providing a polypropylene polymer comprising isotactic polypropylene having a molecular weight distribution of no more than 4, 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 molten polymer to form a fiber preform;
• c) spinning said fiber preform with a spinning speed of at least about 200 meters per minute;
• d) quenching said spun fiber with a heat transfer rate of no more than 12 joules per second per filber;
• e) winding said spun continuous polypropylene fiber.

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 isotactic 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.