Process for the continuous production of multiaxially stretched tubular films of linear polyesters
Abstract
Abstract This invention relates to a process for the continuous production of a multiaxially stretched tubular film of a thermoplastic linear polyester having a low melt viscosity by extruding a melt of the polyester in a substantially vertically downward direction from an annular die at a speed v0 onto an interior calibrating core of a diameter smaller than that of the die while stretching the melt in the longitudinal direction, cooling the melt to form a substantially unoriented tube which engages the core in a gas-tight manner, conveying the tube at a speed v1 > v0 to a heated stretching zone in which the tube is heated to stretching temperature, stretching the tube by means of a further increase in linear speed v2 > v1 and by increasing the pressure in the tube, and cooling the tube.
Inventors
- 👤 W Seifried
- 👤 L Klenk
Bibliographic Details
Claims Analysis
Total Claims: 4References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |