Appeal No. 96-0359
Serial No. 08/083,866
BACKGROUND
The appellant's invention relates to an ethylene polymer blend for blown film production
consisting essentially of a high molecular weight (HMW) component and a relatively low molecular
weight (LMW) component wherein the blend and the individual components have defined properties.
According to appellants, films with good mechanical properties, e.g., Dart
Drop Impact Resistance and Elmendorf Tear, are obtainable if, in addition to the necessary properties
of density, flow index and melt flow index, the polymer blend used to make the film also has a relatively
low dynamic elasticity which, in turn, requires its HMW component to have a molecular weight
distribution, expressed as a flow ratio, of no greater than 15 (Brief pages 2-3).
Claim 14 is illustrative of the claimed subject matter and reads as follows:
14. A blend for blown film production, wherein the blend exhibits a density of
about 0.940 to 0.960 g/cc, an I of about 4 to 12 g/10 min., a MFR of about 75 to
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180, and a dynamic elasticity of about 0.45 to 0.65 at a corresponding complex
viscosity of about 6E5 to 14E5 poises, wherein the blend consists essentially of
at least about 0.5 weight fraction of a relatively high molecular weight (HMW)
component having a density of at least about 0.910 g/cc, a flow index or high load melt
index (I ) of no higher than about 0.8 g/10 min., a molecular weight distribution
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indicated by a flow ratio (FR) no higher than about 15, and a dynamic elasticity at 0.1
rad./sec., of no higher than about 0.75 at a corresponding complex viscosity at 0.1
rad./sec. of no higher than about 7E6.; and
a relatively low molecular weight (LMW) component having a density of at
least about 0.940 g/cc and a melt index (I ) of at least about 100 g/10 min
2
wherein each of said relatively high molecular weight (HMW) component and
said relatively low molecular weight (LMW) component is selected from the group
consisting of a homopolymer of ethylene and at least one copolymer of a
preponderance of ethylene with a minor amount of a 1-olefin containing 3 to about 10
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