Improved method of making media of controlled porosity and product thereof

A process for making a fibrous nonwoven media combining high vapor permeability and low liquid permeability, the method comprising the steps of: (A) providing a fabric meltblown nonwoven composed of fibers having small polymer crystals inside with low heats of fusion, and crystals of relatively larger polymer inside with heat relatively higher melting, the fibers being formed of a polymer drawn and crystallized after prematurely by premature cooling with a cold refrigerant stream air, immediately after stretching and before completing the fiber formation to form both small polymer crystals therein with low heats of fusion and relatively larger polymer crystals therein with relatively higher heats of fusion; and (B) calendering the fabric at a roller surface temperature of 25 to 110C, a force of linear nip 25 to 150 N / mm, and a roll speed of 200 meters / minute, cooperatively being chosen temperature , pressure and roll speed of the calendering operation to soften the small polymer crystals therein with low heats of fusion but not the relatively larger polymer crystals therein to heat relatively higher melting, retaining and high vapor permeability of at least 1,200 g / m2 24 h, while providing low liquid permeability, measured by a pressure head of at least 1 kPa, by compacting, shrinkage of the fibers and contraction in the fibrous medium.