Process for biaxially stretching thermoplastic tubular film
Abstract
Abstract Process and apparatus wherein an extruded seamless thermoplastic tubular film is biaxially stretched by a longitudinal drawing accompanied by an inflation or blowing for transverse stretch. After first inflating the initially extruded film tube under a counterpressure of an externally applied cooling gas in a pressure chamber, the tubular film is necked down from the pressure chamber to pass through an elongated pipe having at least a first cooling section of reduced surface contact with the tubular film, after which the tubular film is reheated for further inflation and/or longitudinal stretching and may then be subsequently tempered to achieve uniform and/or stable dimensions. The resulting inflated and biaxially stretched tube is collapsed or flattened and collected on a take-up roll in the usual manner.
Inventors
- 👤 Alfred Ebert
- 👤 Ernst Pirot
- 👤 Fritz Holler
- 👤 Georg Steinhilber
Bibliographic Details
Claims Analysis
Total Claims: 0References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1973-11-30 | 1974-06-01 | 1974-12-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1977-11-30 | 1978-06-01 | 1978-12-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1981-11-30 | 1982-06-01 | 1982-12-01 | $7700.00 | Window Closed / Lapsed |