| 摘要 |
1,098,556. Polyimide films. E. 1. DU PONT DE NEMOURS & CO. March 31, 1966 [March 31, 1965], No. 14370/66. Heading B5B. A polyimide or polyimide precursor film is stretched in at least one planar dimension by at least 5% at 20-550‹ C. while preventing substantial shrinkage in any planar dimension, the film having an I.V. of at least 0À1 containing a volatile material the content of which is reduced in the stretching process, and having not been previously shrunk in any planar dimension by more than 25%. A polyimide from bis(4- aminophenyl)ether and pyromellitic acid is specified; suitable precursors are polyamideacids, -acid salts, -amides or -esters. The product suitably has an I.V. of at least 0À5, and an " orientation angle " (as defined in the Specification) of less than 75 degrees in at least one direction; it may also be heat shrinkable, and flat or tubular. The usual optional additives may be present. Conventional apparatus is used. |
