Method of making media of controlled porosity and product thereof

A method of making a laminate including a non-woven fibrous media combining high vapor permeability and low liquid permeability, the method comprising the steps of:

• (A) providing a non-woven meltblown fabric formed of fibers that have small polymer crystals therein of low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion, the fibers being formed of a polymer drawn and then prematurely crystallized by premature quenching with a stream of cold quench air immediately after drawing prior to completion of fiber formation to form both small polymer crystals therein of low heats of fusion and relatively larger polymer crystals therein of relatively higher heats of fusion, and then collected during fiber collection to form the fabric;
• (B) calendering the fabric at a roll surface temperature of 25-110° C., a nip linear force of about 25-150 Newtons/mm, and a roll speed of up to about 200 meters/minute, the temperature, pressure and roll speed of the calendering operation being cooperatively selected to soften the small polymer crystals therein of low heats of fusion, but not the relatively larger polymer crystals therein of relatively higher heats of fusion, thereby to retain a high vapor permeability, of at least about 1200 g/m2 @24 h, while providing a low liquid permeability as measured by a hydrohead of at least about 10 millibars, through compaction, fiber shrinkage and contraction in the fibrous media;
• (C) forming a laminate of the calendered fabric and a second material;
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• (D) passing the laminate through an embossing station to impose a pattern of depressions and projections on the calendered fabric whereby the second material enters the depressions of the embossed calendered fabric.