Patent ID: 8795810

Claim:
A laminate of thermoplastic film materials exhibiting throughgoing porosity and comprising: plies A and B, the ply A having an inner surface A 1 partly in contact with the ply B and an outer surface A 2 , and the ply B having an inner surface B 1 partly in contact with the ply A and an outer surface B 2 , where the ply A and the ply B comprise continuous material except for a multitude of perforations in each ply, whereby substantially no perforation in the ply A corresponds directly to a perforation in the ply B, where the lamination between the ply A and the ply B on surfaces A 1 and B 1 being: a) through a coextruded lower melting lamination layer on the ply A and/or the ply B and b) established in such a discontinuous manner that there is formed a channel system between the surfaces A 1 and B 1 connecting a majority of the perforations in the ply A each with at least one of the perforations in the ply B, and connecting a majority of the perforations in the ply B each with at least one of the perforations in the ply A, and characterized in that each channel includes a barrier part having a gap as measured from the surface A 1 to the surface B 1 limited to about 200 μm or less, where the gap being formed by surface irregularities in the surface A 1 and/or the surface B 1 and where the surface irregularities comprise protruding thicker bosses and thinner receding portions, where the channels and the barrier parts withstand hydrostatic pressure and dynamic water pressure, but allow passage of vapor and air.