| 摘要 |
The invention concerns a method for making a multilayer polyolefin film liquid impermeable but gas permeable by co-extruding and drawing at least three polyolefin layers, in at least a structure of the type "A", "B", "C" or "A", "B", "A" or "C", "B", "C", wherein "A" is a skin layer, "B" a central layer, "C" a skin/adhesion layer, wherein: the skin layer "A" contains at least a thermoplastic polyolefin copolymer and/or a grafted polyolefin polymer, having a modulus E less than 50 mPa (ASTM n<o> 882), a flow ranging between 1.5 and 10 g/min (ASTM D 1238 at 190 DEG C and 230 DEG C) and a water vapour transmission rate of at least 100 g/m<2>/24h at 38 DEG C and 90 DEG C of relative humidity; the central layer "B" contains at least a homopolymer and/or a thermoplastic polyolefin copolymer, at least a particulate filler and optionally one or several elastomers; the skin/adhesion layer "C" contains at least an adhesive binding agent and/or a homopolymer and/or a thermoplastic polyolefin copolymer and at least a particulate filler. |
