| 摘要 |
<p>Films, made of polyethylenes, and articles made therefrom exhibit, for a given density, improved oxygen transmission. The polyethylenes are produced in a metallocene-catalyzed production process. The films may be made by a cast film process, and may be made under conditions that raise the birefringence and the oxygen transmission rate of the film, such as increasing strain rate decreasing melt temperature, increasing quench rates, or may be post-extrusion treated, for instance annealed or cold drawn. Combinations of both extrusion techniques and post-extrusion techniques may also be used. Polyethylenes utilized for making such films typically have a Composition Distribution Breadth Index above 50 %, a Mw/Mn below 3, and a Mz/Mw below 2. The permeability of the films so made will be 50 % or more above the permeability of the films based on similar resins based on previously used film formation techniques.</p> |
