Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Patent
1994-07-01
2000-04-04
Chen, Vivian
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
428 357, 428 364, 428338, 428339, 428357, 428401, 428402, 428515, 428516, 428517, 428519, 428521, 428523, 264572, 2641711, 2641761, 2642884, 525 88, 525 98, 525208, 525241, 525221, 525222, 525239, 525240, B32B 310, B32B 2708, B32B 2718, B32B 2732
Patent
active
060459026
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an easy tearable film useful as a packaging material and to a method of producing the same.
BACKGROUND ART
As packaging materials, there are generally used biaxially-stretched films such as polypropylene film and polyethylene terephthalate film. These films, however, are poor in tear properties.
There is also known scored films to improve the tear properties of the films. Still, when a pouch is formed with a scored film, an article is affected adversely by the exterior atmosphere, or the exterior atmosphere is adversely affected by an article, in some cases, depending on the species of the content article.
On the other hand, in order to provide a readily openable packaging bag, there are also known films which are subjected to stretching in one direction to afford tear properties thereto. For example, Japanese Patent Application Laid-open Nos. 125844/1986 (61-125844), 208349/1987 (62-208349), 242746/1990 (2-242746) and 258342/1990 (2-258342) disclose a packaging material wherein a film extensively stretched in one direction is laminated on a paper or film as a base material.
Japanese Patent Application Laid-open No. 22537/1989 (64-22537) discloses a method of producing an easy tearable film which comprises mixing or blending olefinic polymers such as a low-density polyethylene or a high-density polyethylene in a predetermined proportion, extrusion-molding the mixture and stretching the resulting film in the radial direction to provide a flexible film having an islands-sea structure. This film, however, not only is poor in heat resistance and mechanical strength but also has a large tear resistance when torn by hand.
Japanese Patent Application Laid-open No. 180976/1990 (2-180976) also discloses an easy tearable film. However, a copolymer of ethylene component and a cyclic olefin of a specific structure is required to produce such a film and the film is poor in heat resistance.
Japanese Patent Publication Nos. 17632/1978 (53-17632) and 35832/1978 (53-35832) disclose a directly tearable film comprising polypropylene and an ethylene-.alpha.-olefin copolymer or others.
As thus described, when tear properties are imparted to a film by means of stretching treatment, a stretching step for stretching the film in one direction is required, thus the resultant film is high-costed and can be torn only in one direction. Further, even when the film is subjected to the stretching treatment, it is occasionally hard to tear without forming notches, and whiskers or palpi are branched from the film with tearing operation and thus the film cannot be torn sharply in one direction. Additionally, such stretching treatment may cause the formation of wrinkles or rumples by heat-sealing.
Japanese Patent Application Laid-open No. 93351/1989 (1-93351), Japanese Patent Application Laid-open No. 43047/1990 (2-43047) and Japanese Patent Application Laid-open No. 47038/1990 (2-47038) disclose a readily-cuttable polyester film having a tear propagation resistance of 300 g/mm or less in one direction. In this film, however, there is still required a copolyester having a specified structure.
Japanese Patent Application Laid-open No. 299831/1989 (1-299831) discloses a non-stretched or uniaxially-stretched film having oriented or directional tear properties which contains a polyolefin principally comprising an olefin having 4 carbon atoms or less, and polymethylpentene. Yet such an unstretched film is poor in tear properties, and stretching treatment is needed to improve the tear properties. Further, the specified polymer is still required to insure improved tear properties and, since all the above-mentioned polymers are olefinic polymers, the resulting film is still poor in, for example, heat resistance.
Japanese Patent Application Laid-open No. 19137/1992 (4-19137) discloses a method of producing an easy tearable multi-layer film which comprises extrusion-molding a resin compositions comprising two or more different and incompatible resins having largely different melting points each othe
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Imanishi Shinichiro
Sumida Katsuhiko
Ueda Kenji
Chen Vivian
Daicel Chemical Industries Ltd.
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