| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyolefin-based porous film composed of a polyolefin composition in which calcium carbonate and acidic kaolin particles are dispersed, having a moisture permeability of a specific value or above and having property which is impermeable to liquid. SOLUTION: This film is composed of a polyolefin composition in which calcium carbonate and acidic kaolin particles are dispersed and has >=1,500 g/m2.24 hr moisture permeability and has property which is impermeable to liquid. The above polyolefin is preferably polyethylene, polypropylene or propylene-ethylene copolymer obtained by middle or low pressure method, especially preferably a linear low-density polyethylene. Particles of heavy calcium carbonate obtained from calcite type crystalline limestone, precipitated calcium carbonate, etc., produced by wet method according to various chemical reactions can be used as the calcium carbonate particles. The film is produced by mixing calcium carbonate particles with acidic kaolin particles, usually at (1:1) to (1:3) weight ratio and packing the mixture into the polyolefin.
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