Appeal No. 2003-0029
Application No. 09/385,933
BACKGROUND
The invention generally relates to split resistant single layer or co-extruded
multilayered microporous membranes. The microporous membrane is made by a
process that includes preparing a film precursor by a blown film extrusion process at a
blow up ratio of at least 1.5, annealing the film precursor and stretching the resultant
annealed film to form the microporous membrane. (Specification, p. 2). According to
Appellants, the claimed invention has a tear resistance in the transverse direction of at
least 50 kgf/cm2. (Brief, p. 3). The claimed invention is useful in the formation of
battery separators. Claims 1 and 7, which are representative of the invention, are
reproduced below:
1. A microporous membrane comprising a microporous membrane having at
least 80% by weight of a polymer selected from the group consisting of
polypropylene, polyethylene, and a copolymer thereof, and having a tear
resistance in the transverse direction of at least about 50 kgf/cm2, said
membrane being a single layer or a co-extruded multi-layer membrane.
7. A microporous membrane which comprises at least 80% by weight of
a polymer selected from the group consisting of polypropylene,
polyethylene, and a copolymer thereof, said microporous membrane
being a single layer or a co-extruded multi-layer membrane and being
prepared by a process comprising:
extruding a film precursor by a blown film method at a blow-up ratio of
at least about 1.5;
annealing said film precursor; and
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