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US 8,669,002 B2Granted
Microporous film
AssigneesJnc Corporation, Jnc Petrochemical Corporation
InventorsYasuhiro Yamamoto, Hitoshi Satou, Kazuyuki Fukudome
Life of this patent
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Abstract
To provide a thermoplastic resin microporous film being difficult in longitudinal tearing and excellent in tear resistance; a microporous film comprising a thermoplastic resin, wherein a melt flow rate of the thermoplastic resin in the microporous film is in the range of 0.1 to 2.0 g/10 min, tensile strength in a cross-machine direction is in the range of 5 to 10 MPa and tensile elongation in the cross-machine direction is 300% or more.
Claims4
A microporous film comprising a thermoplastic resin,
- which is manufactured by extruding a crystalline thermoplastic resin from a die, further applying heat treatment, and cold stretching and subsequent hot stretching in a machine direction to an extruded film, wherein the microporous film is manufactured according to a method in which a draft ratio during resin extrusion from the die is in the range of 20 to 150, a heat treatment temperature is in the range of a temperature lower by 10° C. than the melting point of the crystalline thermoplastic resin to a temperature less than the melting point, and a period of time of heat treatment is in the range of 3 to 15 minutes,
- wherein a melt flow rate of the thermoplastic resin in the microporous film is in the range of 0.1 to 2.0 g/10 min, tensile strength in a cross-machine direction is in the range of 5 to 10 MPa and tensile elongation in the cross-machine direction is 300% or more,
- wherein the crystalline thermoplastic resin used as a raw material of the microporous film is a polyolefin resin, weight average molecular weight/number average molecular weight of the polyolefin resin is in the range of 4 to 15, and an isothermal crystallization time at a temperature lower by 25° C. than the melting point is 200 seconds or less.
Dependencies are inferred from the claim text.