| 摘要 |
<p>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 no 882), a flow ranging between 1.5 and 10 g/min (ASTM D 1238 at 190 °C and 230°C) and a water vapour transmission rate of at least 100 g/m2/24h at 38 °C and 90 °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.</p> |
