Vapor-permeable liquid-impermeable fabric

摘要

A process is provided for making a water-impermeable, vapor-permeable fabric. A lightweight continuous coating of polypropylene resin is applied to the surface of a fibrous sheet to make the sheet impermeable to water and vapor. Subsequent calendering provides vapor permeability to the sheet while maintaining liquid water impermeability. The resultant product is particularly suited for use as a roofing-tile underlayment or as an air-infiltration barrier.