The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 20, 2003
Filed:
Oct. 22, 2001
Mohan Gownder, Odessa, TX (US);
Jay Nguyen, Pasadena, TX (US);
Fina Technology, Inc., Houston, TX (US);
Abstract
The present invention relates to a method for the production of polypropylene fibers resulting in improved shrinkage percentages and to polypropylene fibers themselves having improved shrinkage percentages. The method includes providing a polypropylene polymer with a melt flow index of no more than about 25 grams per 10 minutes. This polymer should include isotactic polypropylene produced by the polymerization of propylene in the presence of an isospecific metallocene catalyst. The polymer is then heated to a molten state and extruded to form a fiber preform. The preform is spun and subsequently drawn at a take-away speed and a drawing speed providing a draw ratio of no more than about 3, and more preferably no more than about 2.5, to produce a continuous polypropylene fiber. The fiber based on metallocene catalyzed isotactic polypropylene demonstrates improved shrinkage properties of at least about 10% and at some draw ratios at least about 25% over the shrinkage properties of Ziegler-Natta catalyzed isotactic polypropylenes having similar melt-flow indices. In the same method, when the polymer is heated to a molten state, the polymer is preferably heated in a feeding zone to a temperature within the range of about 180° C. to about 225° C. followed by heating in an extrusion zone to a temperature within the range of about 215° C. to about 240° C. immediately prior to extruding the polymer.