| abstract |
Disclosed is a polyolefin multilayer microporous membrane having an excellent balance of shutdown characteristics, meltdown characteristics, permeability, and puncture strength. A first porous layer mainly comprising a polyethylene resin, a polyethylene resin, and (1) a weight average molecular weight of 6 × 10 5 or more, and (2) a heat of fusion measured by a scanning differential calorimeter. And a second porous layer containing polypropylene having a molecular weight of 5 × 10 4 or less (3) having a molecular weight of 5 × 10 4 or less, and a meltdown temperature (however, The down temperature is 5 cm x 5 cm of polyolefin multilayer microporous membrane sandwiched between blocks having a circular opening of 12 mm in diameter, and a tungsten carbide ball of 10 mm in diameter is placed on the polyolefin multilayer microporous membrane in the circular opening, A multilayer microporous membrane having a temperature at which the polyolefin multilayer microporous membrane melts and breaks when heated at a temperature rising rate of 5 ° C / min) of 170 ° C or higher. [Selection] Figure 1 |