| 摘要 |
PROBLEM TO BE SOLVED: To provide a polyolefin resin porous film which has a function suitable for cell separators, separating films, air-permeable waterproofing materials and the like having an excellent function as a porous film and, simultaneously, is at a low cost. SOLUTION: The polyolefin resin porous film is prepared by melt-extruding a resin composition comprising a polyolefin resin (C), as a main component, comprising 30-90 wt.% of a crystalline polypropylene (A) and 10-70 wt.% of a propylene-α-olefin copolymer (B) dispersed in the crystalline polypropylene (A) in which the ratio MFR<SB>PP</SB>/MFR<SB>RC</SB>between the melt flow rate of the crystalline polypropylene (A) MFR<SB>PP</SB>, and the melt flow rate of the propylene-α-olefin copolymer (B) MFR<SB>RC</SB>, is≤10, and obtained by a multi-stage polymerization method including a first stage of producing the crystalline polypropylene (A) and continuously a second stage of producing the propylene-α-olefin copolymer (B); molding the melt-extruded resin composition into a film-like formed product at a draft ratio of 1-10; and stretching the film-like formed product at least in one direction at a temperature of≤100°C, whereby open cell pores are formed by cleavage generated in a region occupied by the copolymer (B) per se. COPYRIGHT: (C)2008,JPO&INPIT |
