| 摘要 |
PROBLEM TO BE SOLVED: To provide a cell that has a long-term appreciable hydrophilic property, a low internal pressure when incorporated in a battery, and a long cycle life, because of the inclusion of a hydrophilic polyolefin-series fiber consisting of a polyolefin-series resin at least partly mixed with a hydrophilicity agent of a weight-average molecular weight of from 200 to 1000. SOLUTION: A polypropylene resin of a melt flow rate of about 30 g/10 min (230 deg.C) is mixed with such a hydrophilicity agent as sodium alkanesulfonate of a weight-average molecular weight of 314 in an amount of from 0.2 to 10% by weight. The obtained resin is then melted, spun, elongated, and supplied with a hydrophilic fiber-setting agent, prior to cut into elements of 10 mm length and 0.9 dtex. The obtained fiber in an amount of 60% by weight is mixed with such a thermo-adhesive fiber as a sheath-core conjugate fiber in an amount of 40% by weight comprising a polypropylene core and a polyethylene sheath, before subjected to the wet-type sheeting process. This sheet is in turn heat-treated and heat-calendered for thickness control to complete the cell separator.
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