| 摘要 |
Provided is a porous polypropylene film having both air permeability properties and puncture strength. A porous polypropylene film which has an air permeability of 700 seconds/100 ml or less and a puncture strength of 1.5 N or greater, and has ² activity can be obtained when the porous polypropylene film is made to have a tensile strength in the machine direction of the film, E MD , of 100 MPa or greater, a tensile strength in the transverse direction to the machine direction, E TD , of less than 100 MPa, and a ratio of E MD and E TD , E MD /E TD , of 1.5 to 10.
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