Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2002-11-05
2004-04-20
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S516000, C428S520000, C428S528000, C525S240000
Reexamination Certificate
active
06723446
ABSTRACT:
TECHNICAL FIELD
The present invention relates to films, in details, a wrap film for commercial or household use, and to a shrink film employed for packaging and other purposes. More particularly, the invention relates to a wrap film which contains no chlorine, which is environmentally friendly, which exhibits excellent safety, and which exhibits characteristics required of wrap film, such as wrapping-ability, transparency, and restoration from deformation; and to a shrink film which contains no chlorine, which is environmentally friendly, which exhibits excellent safety, transparency, glossiness, and low-temperature shrink-packaging characteristics, and which enables packaging of a product having relatively low strength while providing the product with good appearance, without involving deformation of the product.
BACKGROUND ART
Conventionally, vegetables and fruits, meats, fishes, processed foods made from these, and cooked foods such as delicatessen items—which are sold in department stores, supermarkets, and grocery stores—have been placed on lightweight trays formed from foaming resin, and wrapped with film. In the home, when a grocery item is stored in a freezer or a refrigerator, or heated in a microwave oven, the item is placed in a container and wrapped with film.
Such wrapping film is required to exhibit excellent characteristics in terms of, for example, transparency, finishing appearance, wrapping efficiency, resistance to poking, and restoration from deformation when being pushed with a finger. In general, a polyvinyl-chloride-based resin such as polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC) is widely employed for producing a film satisfactorily exhibiting such wrapping characteristics.
However, since a polyvinyl-chloride-based resin such as polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC) contains chlorine in the molecule, when a film formed from such a resin is incinerated after being used and disposed of, a toxic substance such as hydrogen chloride gas or dioxin is generated, thereby raising environmental problems. Further, elution of a plasticizer, which is incorporated into a wrap film in large amount for softening the film, is problematic from the viewpoint of safety.
In order to solve such problems, attempts to employ a polyethylene film or a polypropylene film have been made, and such a film has been put into practice. Although a polyethylene film exhibits good low-temperature characteristics, it exhibits poor heat resistance, whereas a polypropylene film exhibits poor low-temperature characteristics and high heat resistance. In addition, a polyethylene film or a polypropylene film exhibits unsatisfactory adhesion to, for example, a tray, and adhesion between polyethylene films or between polypropylene films is unsatisfactory.
Therefore, there have been proposed various techniques for incorporating, into a propylene-based resin, ethylene-propylene rubber, a styrene-ethylene-butylene-styrene block copolymer, modified polyolefin, polybutene, a hydrocarbon resin, an adhesion-imparting aid, etc. However, such an additive does not necessarily exhibit sufficient miscibility with a polypropylene-based resin, and raises problems including roughing of a surface, lowering of transparency, lowering of film forming-ability, and bleeding of a low molecular weight compound serving as an adhesion-imparting aid.
Japanese Patent Application Laid-Open (kokai) No. 11-29667 discloses a wrap film formed from a resin composition containing (A) (50 to 98 parts by weight) of a polypropylene-based resin and (B) (2 to 50 parts by weight) of an ethylene-&agr;-olefin copolymer having a density of 0.900 g/cm
3
or less; and Japanese Patent Application Laid-Open (kokai) No. 11-29668 discloses a wrap film formed from a resin composition containing (A) (100 parts by weight) of a polypropylene-based resin and (B) (1 to 15 parts by weight)of oil and fat. However, like the cases of the aforementioned conventional techniques, a low-molecular-weight compound such as polybutene or oil and fat must be incorporated into such a wrap film in order to secure adhesion of the wrap film.
Japanese Patent Application Laid-Open (kokai) 2000-44742 discloses a wrap film containing a soft polypropylene-based resin containing (A) 20 to 60 wt. % of a polypropylene having an isotactic index of at least 80; and (B) 40 to 80 wt. % of a copolymer component consisting of (I) 25 to 95 wt. % of a crystalline component which is a copolymer component of ethylene and an olefin having at least four carbon atoms, contains 50 to 95 wt. % of ethylene and has crystalline polyethylene which is insoluble in xylene at 25° C., and (II) 5 to 75 wt. % of an amorphous component which is soluble in xylene at 25° C. When characteristics of the wrap film are evaluated, instead of a single-layer film consisting of the wrap film, a multi-layer film including the wrap film and outer layers formed from a propylene-ethylene-butene-1 copolymer and an ethylene-vinyl acetate copolymer is employed. Therefore, characteristics of the polypropylene-based resin are not reflected in characteristics of the multi-layer film. Furthermore, transparency of the wrap film is not satisfactory.
Although a wrap film formed from a polyolefin-based resin containing no chlorine can solve environmental problems, characteristics of the wrap film are inferior to those of a wrap film formed from a polyvinyl-chloride-based resin. Therefore, in actuality, wrap films formed from a polyvinyl-chloride-based resin are widely used.
Heat shrink packaging employing a heat-shrinkable film (shrink film)—in which an object is wrapped with a shrink film, and the object is caused to pass through a heating furnace so as to shrink the film, whereby the film adheres to the object; or a plurality of objects are bound together with a shrink film—is widely carried out for packaging of cup noodle products or for lamination packaging of, for example, notebooks or tissue paper.
At present, a stretched film formed from, for example, a polyvinyl-chloride-based resin such as polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC), a polyethylene-based resin, or a polypropylene resin is employed as a shrink film in heat shrink packaging. A shrink film is required to exhibit excellent characteristics in terms of, for example, heat shrinking-ability during packaging, melting-breakage resistance, side welding property, hot slip property, transparency after packaging, high glossiness, mechanical strength, and appearance after packaging (i.e., the edge of the film adheres to an object without forming wrinkles). Generally, a shrink film formed from a polyvinyl-chloride-based resin, which satisfactorily exhibits such characteristics, is employed.
However, since a polyvinyl-chloride-based resin such as polyvinyl chloride (PVC) or polyvinylidene chloride (PVDC) contains chlorine in the molecule, when a film formed from such a resin is incinerated after being used and disposed of, a toxic substance derived from chlorine, such as hydrogen chloride gas or dioxin, generates, thereby raising environmental problems. Furthermore, elution of a plasticizer, which is incorporated into a shrink film in large amount for softening the film, is problematic from the viewpoint of safety. In addition, when a shrink film formed from a polyvinyl-chloride-based resin is heated during heat shrink packaging, the resin issues a foul odor. Therefore, from the environmental viewpoint during packaging, demand has arisen for further improvements to such a shrink film.
In order to solve such problems, attempts to employ a polyethylene film or a polypropylene film have been made, and such a film have been put into practice. Although a polyethylene film exhibits good low-temperature characteristics, it exhibits poor heat resistance and melting-breakage resistance, whereas a polypropylene film exhibits poor low-temperature characteristics and high heat resistance. When heating temperature is increased during shrink packaging of a product by use of such a film, the packaged product is deformed due to heat
Endoh Masahiko
Seta Yasushi
Idemitsu Petrochemical Co. Ltd.
Tarazano D. Lawrence
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