| abstract |
The present invention provides a polyolefin multilayer microporous membrane having an excellent balance of permeability, mechanical strength, meltdown characteristics, electrolyte solution absorbability and electrolyte solution retention, a method for producing the same, a battery separator, and a battery. A first microporous layer forming at least both surface layers and at least one second microporous layer provided between both surface layers, wherein the first layer has a weight average molecular weight. Includes a first polyethylene-based resin in which the ratio of ultrahigh molecular weight polyethylene of 1 × 10 6 or more is 8% by mass or more, and the second layer is a second layer in which the ratio of ultrahigh molecular weight polyethylene is 7% by mass or less. The pore size distribution curve obtained by mercury porosimetry has a structure having at least two peaks, and the total thickness of the first and second layers is 100%, and the first layer Polyolefin multilayer microporous membrane with a total thickness of 15-60%. [Selection figure] None |