Reduced shrinkage in metallocene isotactic polypropylene fibers
US6416699B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 9, 1999 |
| Grant date | Jul 9, 2002 |
| Priority date | — |
| Expiry date | Jun 9, 2019 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/2967
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
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 te…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.