US4451524B1 - - Google Patents
Abstract
Abstract A polypropylene strap for use in packaging articles is manufactured by stretching a belt-like sheet (3) of polypropylene which has been extruded from a die, in the lengthwise direction thereof at a relatively high draw ratio for example, 4-9, heating the surfaces of the resulting sheet to put the molecular chains in the superficial layers (21) only thereof in a non-oriented state, and then stretching the sheet (3) at a relatively low draw ratio of, for example, 1.2-3. Such a polypropylene strap has a high tensile strength, a low elongation, a high rigidity, a high abrasion resistance, and flexible surfaces, and it is not easily split in the longitudinal direction.
Inventors
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Bibliographic Details
Claims Analysis
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-11-09 | 1991-05-11 | 1991-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-09 | 1995-05-11 | 1995-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-09 | 1999-05-11 | 1999-11-10 | $7700.00 | Window Closed / Lapsed |