| 摘要 |
PROBLEM TO BE SOLVED: To provide: a polypropylene microporous film for a battery separator which is arranged to have high-temperature dimensional stability and low thermal shrinkage; and a method for manufacturing such a polypropylene microporous film.SOLUTION: A propylene porous film for a battery separator is arranged by the following steps of: molding, like a sheet, a resin composition including a blend of a resin component substantially consisting of a homopolypropylene resin and an inorganic microparticle filler, in which the content of the inorganic microparticle filler is 40-60 wt.%; (1)longitudinally drawing the resultant sheet with a drawing rate of 6-9 times at 84-114°C (drawing in MD direction); (2)subsequently, transversely drawing the sheet at 140-165°C with a drawing rate of 1.5-2.8 times in a transverse drawing machine 2 (drawing in TD direction); (3)subsequently, causing the sheet to shrink and reduce a stress in its widthwise direction by 0-25%; and (4) heat-fixing the belt-like sheet by heating at a temperature of 163-167°C, during which the belt-like sheet is secured by a heat-fixing machine 3 including heating rolls 31A to 31C and nip rolls 32A to 32C so as to prevent the change in size in a conveying direction (MD direction) of the resultant belt-like sheet and its widthwise direction (TD direction).SELECTED DRAWING: Figure 2 |
