Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Patent
1996-05-24
1997-11-25
Thibodeau, Paul J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
428515, 428516, 428910, 428 349, 428 357, B32B 2732, B65B 5302
Patent
active
056910495
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a heat shrinkable polyolefin film, and more particularly to a heat shrinkable laminate film having an intermediate layer made of an ethylene resin composition consisting essentially of a linear low density polyethylene and a syndiotactic polypropylene and being excellent in transparency and low temperature shrinkability.
BACKGROUND ART
Polyvinyl chloride films, polyethylene films, polypropylene films and the like are hitherto known as heat shrinkable packaging materials. From the viewpoint of low price and easiness in disposal after use, heat shrinkable films of polyolefins such as polyethylene and polypropylene have been preferably used. However, among them, heat shrinkable polyethylene films have a feature of being excellent in impact resistance and the like, but they have the defect that because of lacking a film firmness, they are not satisfactory for use in high speed packaging. On the other hand, heat shrinkable polypropylene films have a film firmness and accordingly have an excellent packaging machine applicability, but have the defect that no shrinkage occurs unless the temperature is relatively high.
As a means to solve the above-mentioned defects, the present inventors proposed a heat shrinkable laminate film comprising a polyethylene resin layer and a polypropylene resin layer (Japanese Patent Publication Kokai No. 63-173641).
The proposed film is a good heat shrinkable film having both a low temperature shrinkability and a good film firmness, but it has a problem that the transparency is lowered if pieces of films generated in the manufacturing steps and films out of standard (hereinafter referred to as "recovered films") are recycled.
DISCLOSURE OF THE INVENTION
The present inventors have made intensive studies to obtain heat shrinkable films free of the above-mentioned defects, and as a result, they have arrived at the present invention.
That is to say, the present invention provides a heat shrinkable polyolefin laminate film, which is excellent in low temperature shrinkability and free of lowering of the transparency in case of recycling recovered films, comprising an intermediate layer and surface layers, said intermediate layer comprising an ethylene resin composition consisting essentially of (A) 80 to 50 parts by weight of a linear low density polyethylene comprising ethylene and an .alpha.-olefin and having a density of 0.91 to 0.93 g/cm.sup.3 at 25.degree. C. and a melt index of 0.2 to 3.0 g/10 minutes and (B) 20 to 50 parts by weight of a syndiotactic polypropylene, and said surface layers comprising a crystalline polypropylene resin, wherein the thickness of said intermediate layer is not less than 30% of the total thickness, the thickness of each of said surface layers is at least 1 .mu.m, and said film is stretched at least two times in both the machine and transverse directions.
The present invention is explained in detail below.
The linear low density polyethylene (A) comprising ethylene and an .alpha.-olefin and being used as one of the components of the intermediate layer has a density of 0.91 to 0.93 g/cm.sup.3 at 25.degree. C. and a melt index of 0.2 to 3.0 g/10 minutes. The polyethylene (A) having a density of less than 0.91 g/cm.sup.3 is not preferable because of a little effect of improving the film firmness and because the transparency is lowered when the recovered films are recycled. If the density is more than 0.93 g/cm.sup.3, it is not preferable because of insufficient low temperature shrinkability. Also, the polyethylene (A) having a melt index of less than 0.2 g/10 minutes is not preferable because of increase in a motor load at melt-extrusion. If the melt index is more than 3.0 g/10 minutes, it is not preferable since the stability in a stretching step is deteriorated. Also, as the .alpha.-olefin to be copolymerized with ethylene, perferred are one or more members selected from the group consisting of butene-1, pentene-1, hexene-1, heptene-1, octene-1, 4-methylpentene-1, decene-1, undecene-1 and dodecene-1. T
REFERENCES:
patent: 5252384 (1993-10-01), Bothe et al.
patent: 5478646 (1995-12-01), Asanuma et al.
Derwent Publication Ltd., vol. 18, No. 506, Patent Abstracts of Japan, AN 94-237636 and JP A 06 169 974.
European Search Report dated Aug. 28, 1996, Ref. No. L 59 758 listing above cited references.
Horita Fumio
Isozaki Hideo
Morita Shuichi
Oyama Toshikatsu
Sueoka Koji
Kohjin Co., Ltd.
Tarazano D. Lawrence
Thibodeau Paul J.
LandOfFree
Heat shrinkable polyolefin laminate film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat shrinkable polyolefin laminate film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat shrinkable polyolefin laminate film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2105171