| 摘要 |
PROBLEM TO BE SOLVED: To obtain a porous film having a good balance between strength and moisture permeability and excellent flexibility and elasticity by molding a composition containing a specified lowly crystalline thermoplastic resin and having a specified composition into a film and stretching this film. SOLUTION: A composition prepared by mixing 100 pts.wt. lowly crystalline (crystallinity of below 20%) or amorphous thermoplastic resin with 25-400 pts.wt. filler is molded into a film. This film is stretched. The stretched film has the following properties: the porosity is 5-60%, the initial modulus of elasticity is at most 4.5kg/mm<2> , the stress after 20% elongation is at most 0.4 time that at break, and the residual strain is 5% or below when the sample is kept in a state of 50% elongation for 10min and then released from this state. The thermoplastic resin used is at least one member selected from the group consisting of ethylene/α-olefin copolymers, 1,2-polybutadienes, high-pressure process low-density polyethylenes and linear low-density polyethylenes or a mixture of at least two types of these members.
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