Vapor-permeable liquid-impermeable fabric
AssigneeE. I. Du Pont de Nemours and Company
InventorGene W. Lou
Life of this patent
Estimating the term…
Abstract
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.
Claims6
A process for preparing a vapor-permeable, liquid-water-impermeable fabric which consists essentially of the steps of applying a continuous coating of polypropylene to a surface of a vapor-and-liquid-permeable, fibrous base sheet and then calendering the coated surface, the polypropylene coating having a melt flow rate of at least 30 and amounting to a unit weight in the range of 5 to 15 g/m.sup.2, and the calendering being performed at a sufficient temperature and under a sufficient load to increase the moisture vapor transmission of the coated fabric to at least 200 g/m.sup.2 /day while obtaining a hydrostatic head of at least 20 cm.
A vapor-permeable, liquid-water-impermeable fabric which consists essentially of
- a coated fibrous base sheet of polypropylene or polyester filaments weighing in the range of 50 to 125 g/m.sup.2, the filaments having a dtex per filament in the range of 1 to 20,
- and at least one flat surface of the fibrous base sheet having a calendered coating layer of polypropylene which has a melt flow rate in the range of 30 to 150, the coating layer having a unit weight in the range of 5 to 15 g/m.sup.2 and containing a multiplicity of small pores which permit substantial flow of gas, but prevent substantial flow of liquid water,
- the fabric having a moisture vapor transmission of at least 200 g/m.sup.2 /day and a hydrostatic head of at least 20 cm.
Dependencies are inferred from the claim text.