| 摘要 |
PURPOSE:To provide the subject film having a high inhibiting rate and a high permeation rate, suitable for sterile packaging, etc., and comprising two different porous layers by melt-coextruding two specific polymers and stretching the coextruded film under a cold condition and subsequently under a heated condition to form a porous film. CONSTITUTION:Two different kinds of polymers selected from crystallizable polymers having melt indexes of 0.1-15 or two same polymers having different melt indexes are supplied into an apparatus for producing films and subsequently coextruded in a laminated state at a temperature higher by 10-80 deg.C than the melting point of the polymer having the higher melting point in an extrusion ratio of both the polymers of 50/1-1/50 (pts.wt.). After taken off under cooling, the produced film is cold-stretched at a temperature of <=60 deg.C and subsequently hot-stretched at a temperature lower by 50-10 deg.C than the melting point of the polymer having the lower melting point to provide the objective film. |
