Package making – Methods – Conforming by stretching or shrinking of cover over contents
Patent
1997-05-21
1999-06-01
Johnson, Linda
Package making
Methods
Conforming by stretching or shrinking of cover over contents
B65B 5300
Patent
active
059079428
ABSTRACT:
A method of stretch wrapping an item with a multilayer, thermoplastic stretch wrap film. The stretch wrap film containing at least three polymeric film layers and comprised of a first layer and a second layer. The first and second layers may comprise a polymer of two or more monomers, wherein a first monomer is ethylene, in a major amount by weight, and a second monomer is an alpha olefin of from about 3 to about 12 carbon atoms, in a minor amount by weight. If the first and second layers are outer layers, they have a cling force to each other of at least about 140 grams/inch. The stretch wrap film also has at least one inner polymeric layer, located between the first and second layers. The inner polymeric layer comprises a low polydispersity polymer having a polydispersity of from about 1 to about 4, a melt index (I.sub.2) of from about 0.5 to about 10 g/10 min, and a melt flow ratio (I.sub.20 /I.sub.2) of from about 12 to about 22. The inner layer(s) comprise(s) from about 5 wt. % to about 40 wt. % of the stretch wrap film so as to produce a film having a maximum stretch of at least 340%, a F-50 dart drop value of at least about 130 g/mil, a machine directional tear resistance of at least about 125 g/mil and a transverse directional tear resistance of at least about 500 g/mil. It is contemplated that additional outer layers may be added such an outer high cling layer or an outer slip layer, as well as additional inner layers.
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Johnson Linda
Tenneco Packaging
LandOfFree
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