Biaxially oriented microporous membrane
AssigneeCelgard, LLC
InventorsXiangyun Wei, Charles Haire
Life of this patent
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Abstract
A microporous membrane is made by a dry-stretch process and has substantially round shaped pores and a ratio of machine direction tensile strength to transverse direction tensile strength in the range of 0.5 to 5.0. The method of making the foregoing microporous membrane includes the steps of: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching including a simultaneous controlled machine direction relax.
Claims19
A membrane comprising:
- a microporous polyolefin film made by a dry-stretch process and having substantially round shaped pores which have an aspect ratio in the range of 0.75 to 1.25.
A membrane comprising:
- a single ply microporous polymer film made by a dry-stretch process and having substantially round shaped pores with an aspect ratio in the range of 0.75 to 1.25, a ratio of machine direction tensile strength to transverse direction tensile strength in the range of 0.5 to 5.0, and an average pore size in the range of 0.03 to 0.30 microns,
- wherein said polymer is a polyolefin, and
- wherein the microporous polymer film is obtained by a dry-stretch process comprising the steps of
- extruding a nonporous precursor,
- biaxially stretching the nonporous precursor, wherein said biaxial stretching includes transverse direction stretch with simultaneous controlled machine direction relax and where pore formation results from said biaxially stretching the nonporous precursor.
Dependencies are inferred from the claim text.