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Filled, biaxially oriented, thermoplastic film having preferential shrinkage and method of making such film |
| T981003 |
Filled, biaxially oriented, thermoplastic film having preferential shrinkage and method of making such film
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| Patent Drawings: | |
| Inventor: |
Bartron, et al. |
| Date Issued: |
April 3, 1979 |
| Application: |
05/923,569 |
| Filed: |
July 11, 1978 |
| Inventors: |
Anderson; Samuel P. (Wilmington, DE)
Bartron; Lester R. (Wilmington, DE)
Michel; Rudolph H. (Wilmington, DE)
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| Assignee: |
E. I. Du Pont de Nemours and Company (Wilmington, DE) |
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| U.S. Class: |
264/154; 264/210.6; 264/290.2; 521/134; 521/143; 521/144; 521/79; 524/921 |
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| Abstract: |
a filled, biaxially oriented, void-containing thermoplastic film suitable for making heat-shrinkable bands is provided having shrinkage on heating to 100.degree. C. of greater than 5%, which shrinkage in turn is at least 5% greater than the shrinkage in a direction perpendicular thereto.A process for preparing this film with its preferential shrinkage is provided including the steps of:(a) melt-blending a C.sub.2 -C.sub.10 .alpha.-monoolefin polymer and at least 20 weight percent inert filler, based on the total weight of polymer and filler;(b) forming a film from the melt blend;(c) cooling the film to a temperature below the melting point;(d) biaxially stretching the film at least about twice its original forming dimensions in mutually perpendicular directions while the film temperature is above the line-drawing temperature and below the polymer melting temperature, until the film has at least about 30% voids;(e) cooling the film to room temperature; and(f) post-stretching the biaxially stretched film in a selected direction at a temperature below 100.degree. C. to an extent that provides the above-mentioned preferential shrinkage in the filled film. |
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