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US 8,273,279 B2Granted
Microporous polyolefin membrane and manufacturing method
AssigneeToray Battery Separator Film Co., Ltd.
InventorsKotaro Takita, Shintaro Kikuchi
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AssigneeToray Battery Separator Film Co., Ltd.
InventorsKotaro Takita, Shintaro Kikuchi
Estimating the term…
A microporous membrane having a structure in which its pore size distribution curve obtained by mercury intrusion porosimetry has at least two peaks, which is produced by extruding a combination of a diluent or solvent and a polyolefin resin composition comprising from about 75 to about 99% of a polyethylene resin having a weight average molecular weight of from about 2.5×105 to about 5×105 and a molecular weight distribution of from about 10 to about 100, and from about 1 to about 25% polypropylene resin having a weight average molecular weight of from about 1×104 to about 4×106, a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1 to about 100, percentages based on the mass of the polyolefin composition; cooling the extrudate to form a high polyolefin content cooled extrudate; stretching the cooled extrudate at a high stretching temperature to form a stretched sheet; removing the diluent or solvent from the stretched sheet to form a membrane; stretching the membrane to a high magnification in at least one direction to form a stretched membrane; and heat-setting the stretched membrane to form the microporous membrane.
A microporous membrane comprising from about 75 to about 99% of a polyethylene having a weight average molecular weight of from about 2.5×105 to about 5×105 and a molecular weight distribution of from about 10 to about 100, and from about 1 to about 25% polypropylene having a weight average molecular weight of from about 1×104 to about 4×106, a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1 to about 100, percentages based on the mass of the membrane, wherein the membrane comprises pores characterized by a pore size distribution curve determined by mercury intrusion porosimetry, the curve representing a number of pores on a y-axis and pore size on an x-axis and having at least two peaks and contains dense domains corresponding to a main peak in a range of 0.01 μm to 0.08 μm in the pore size distribution curve and course domains corresponding to at least one sub-peak in a range of more than 0.08 μm to 1.5 μm or less in the pore size distribution curve such that the dense and coarse domains are irregularly entangled in any cross section of the membrane viewed in both longitudinal and transverse directions.
A battery separator comprising a microporous membrane comprising comprising from about 75 to about 99% of a polyethylene having a weight average molecular weight of from about 2.5×105 to about 5×105 and a molecular weight distribution of from about 10 to about 100, and from about 1 to about 25% polypropylene having a weight average molecular weight of from about 1×104 to about 4×106, a heat of fusion of 80 J/g or higher, and a molecular weight distribution of from about 1 to about 100, percentages based on the mass of the membrane, wherein the membrane comprises pores characterized by a pore size distribution curve determined by mercury intrusion porosimetry, the curve representing a number of pores on a y-axis and pore size on an x-axis and having at least two peaks and containing dense domains corresponding to a main peak in a range of 0.01 μm to 0.08 μm in the pore size distribution curve and course domains corresponding to at least one sub-peak in a range of more than 0.08 μm to 1.5 μm or less in the pore size distribution curve such that the dense and coarse domains are irregularly entangled in any cross section of the membrane viewed in both longitudinal and transverse directions.
Dependencies are inferred from the claim text.