Three-layered polypropylene films
US4235365A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 1, 1979 |
| Grant date | Nov 25, 1980 |
| Priority date | — |
| Expiry date | Oct 1, 1999 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T428/31913
- WIPO fieldSurface technology, coating
- WIPO sectorChemistry
Abstract
This invention relates to a three-layered polypropylene film consisting of a core layer of biaxially oriented polypropylene sandwiched between ethylene-propylene copolymer layers having a different degree of molecular orientation, shown by birefringence, i.e., birefringence of one copolymer layer is different from that of the other copolymer layer. The film thus prepared has not only a good heat sealing property but also a good resistance against "hot-tack", "blocking", and "scratches". The film can be provided by a process wherein one copolymer layer is biaxially stretched, while the other copolymer layer is uniaxially stretched. Three-layered films of this invention are particularly suited for making bags with lap sealed parts, where lap sealing is a heat sealing method characterized by heat sealing one side of a film with the other side of the film.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.