POROUS FILM AND MANUFACTURING METHOD OF POROUS FILM

摘要

PROBLEM TO BE SOLVED: To provide a porous film which is excellent in penetrativity at a working temperature and which can be immediately shut down at a temperature higher than a working temperature in low temperatures. SOLUTION: This porous film is formed from a polyolefinic resin comprising (A) an ethylene-α-olefin copolymer which comprises a constitutional unit derived from ethylene and a constitutional unit derived from one or more monomers selected fromα-olefins having a carbon number of 4 to 8 and which satisfies all of the following requirements (I) to (IV): (I) the limiting viscosity number [η] is 9.0 to 15.0 dl/g; (II) the melting point (Tm) is 115°C or higher and lower than 130°C; (III) the content of a cold xylene soluble part (CXS) contained in (A) an ethylene-α-olefin copolymer is 3 wt.% or less; and (IV) Tm≤0.54×[η]+114. COPYRIGHT: (C)2007,JPO&INPIT