Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Reexamination Certificate
2007-06-26
2007-06-26
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
C264S288800, C264S290200
Reexamination Certificate
active
10468005
ABSTRACT:
Disclosed is a successively biaxially stretched film obtained by successive biaxial stretching method comprising extruding a melt of a β-crystal nucleating agent-containing polypropylene-based resin composition from a T-die, cooling the extruded resin on a chill roll, and stretching the resulting web sheet longitudinally and then transversely, wherein the longitudinally stretched sheet is made to have a degree of β-crystal orientation of less than 0.3 by the following method (I) and/or (II), optionally subjected to annealing treatment, and transversely stretched:method (I): melting the polypropylene-based resin composition containing needle crystals of a specific β-crystal nucleating agent at a temperature not lower than m.p. of the polypropylene-based resin and lower than dissolution temperature of the β-crystal nucleating agent in the polypropylene-based resin melt, and extruding the melt from the T-die at the same temperature,method (II): adjusting neck-in ratio during longitudinal stretching to 25 to 55%.The porous polypropylene film has good breakage resistance during manufacture, excellent thickness uniformity, high porosity and air-permeability, and is useful for battery separators.
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Hoki Manabu
Ikeda Naoki
Nagata Kenichiro
Ogino Koichi
Sadamitsu Kiyoshi
Armstrong, Kratz, Quintos Hanson & Brooks, LLP.
Kuhns Allan R.
New Japan Chemical Co. Ltd.
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