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Polypropylene films
| Details |
Inventors: Crighton, Allan J.; Syme, Blair G. W.;
Assignee: Courtaulds Films & Packaging (Holdings) Ltd. (GB2)
Primary Examiner: Buffalow; Edith L.
Assistant Examiner:
Attorney, Agent or Firm: Bacon & Thomas
This invention concerns biaxially oriented polypropylene films containing from 1 to 40 percent by weight of a hydrocarbon resin, the resin being substantially miscible with the polypropylene, and the film having a crease retention of at least 50% as measured by ASTM D920-49. The hydrocarbon resin is preferably a terpene resin, a hydrogenated synthetic resin or a compatible rosin. Crease retention values in excess of 70% have been achieved in particular by orienting the films at a temperature of at least 10 Centigrade degrees below the crystalline melting point of the polypropylene. |
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DETAILED DESCRIPTION We claim: 1.
A biaxially oriented polypropylene film containing from 1 to 40 percent by weight of a hydrocarbon resin, the resin being substantially miscible with the polypropylene, and the film being sequentially biaxially oriented and having a cease retention of at least 50% as measured by ASTM D920-49.
2.
A biaxially oriented polypropylene film according to claim 1, wherein the film has a crease retention of at least 60% as measured by ASTM D920-49.
3.
A biaxially oriented polypropylene film according to claim 2, wherein the film has a crease retention of at least 70% as measured by ASTM D920-49.
4.
A biaxially oriented polypropylene film according to claim 1, wherein the film has a twist retention of at least 1.
0.
5.
A biaxially oriented polypropylene film according to claim 1, wherein the hydrocarbon resin is a terpene resin, a hydrogenated synthetic resin or a compatible rosin.
6.
A biaxially oriented polypropylene film according to claim 5, wherein the hydrocarbon resin is a synthetic hydrogenated resin.
7.
A biaxially oriented polypropylene film according to claim 1, having at least one further polymeric layer thereon.
8.
A biaxially oriented polypropylene film according to claim 1, wherein the polypropylene contains an organic or inorganic filler.
Description:
This invention concerns polymeric films and in particular oriented polypropylene films.
Biaxially oriented polypropylene homopolymer films have shown wide acceptance as packaging materials.
However, for certain applications such films do not exhibit satisfactory properties, in particular for twist wrap or other instances where crease retention or dead fold are required.
Thus for twist wrap polypropylene homopolymer films have been found to be inferior to films of regenerated cellulose, the polypropylene films tending to untwist to an unacceptable degree.
In some cases, untwisting can be sufficient that the wrapped article falls out of its wrapper.
It has been proposed in British Patent Specification 1231861 to produce biaxially oriented polypropylene films containing from 5 to 30% by weight of a terpene polymer, a compatible hydrogenated hydrocarbon resin, or a compatible rosin derivative, each having a softening point above 70
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Manufacturing Materials 
