Process and apparatus for producing sheet film from tubular thermoplastic resin film
US4003973A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1972 |
| Grant date | Jan 18, 1977 |
| Priority date | — |
| Expiry date | Jun 23, 1992 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29C2793/0063
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A sheet film is produced from a tubular thermoplastic resin film by cooling a molten tubular film of crystalline thermoplastic resin, for example, polypropylene, extruded downward from an annular die in direct contact simultaneously with cooling liquids on the outside and inside of the film, the cooling liquid on the outside being in an outside cooling liquid tank and in contact with the outside of the film and the cooling liquid on the inside flowing down along the surface of a mandrel provided through the outside cooling liquid tank and in contact with the inside of the film, a liquid level of the cooling liquid on the inside being kept higher by 5-15 mm than that of the cooling liquid on the outside; cutting open length wise one or two side ends of the film just before being flattened and folded by nip rolls thereby to discharge the cooling liquid from the inside; and removing the liquid attached to the surfaces of the resulting sheet films withdrawn by the nip rolls promptly. The sheet films having a good transparency, good flatness and less uneveness in thickness can be thereby produced at a high speed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.