| 摘要 |
PROBLEM TO BE SOLVED: To efficiently obtain a microporous polyolefin film which is easy to handle by extruding and quenching a soln. contg. an ultrahigh-mol.-wt. polyolefin and a polyolefin having a specified density, stretching the resultant molded gel, and removing a solvent from the gel. SOLUTION: A soln. is prepd. which comprises 90-50wt.% solvent and 10-50wt.% polyolefin compsn. comprising 1wt.% or higher ultrahigh-mol.-wt. polyolefin having a wt.-average mol.wt. of 5×10<5> or higher and another polyolefin having a wt.-average mol.wt. of 1×10<4> or higher but lower than 1×10<5> and a density of 0.945g/cc or higher. The soln. is extruded through a die and quenched to form a gel compsn., which is stretched at or below the temp. 10 deg.C higher than the m.p. of the polyolefin compsn. and freed of the remaining solvent, thus giving a microporous polyolefin film. Since the gel compsn. in this process has high hardness and scratch resistance, does not cause film breaking due to notches, and sags little, it can be easily held by a fastener of a stretching machine and enables an efficient production of the microporous film.
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