Microporous composite sheet material

Abstract

A moisture vapor permeable, water impermeable composite sheet material is provided which is suitable for use as a housewrap material, and is also useful for other applications such as tarpaulins, or as covers for automobile, boats, patio furniture or the like. The composite sheet material includes a nonwoven substrate and an extrusion-coated polyolefin film layer overlying one surface of the substrate. The nonwoven substrate is comprised of polymeric fibers randomly disposed and bonded to one another to form a high tenacity nonwoven web. The nonwoven substrate has a grab tensile strength of at least 178 Newtons (40 pounds) in at least one of the machine direction (MD) or the cross-machine direction (CD). The extrusion coated polyolefin film layer is intimately bonded to the nonwoven substrate. The film layer has micropores formed therein to impart to the composite sheet material a moisture vapor transmission rate (MVTR) of at least 35 g/m2/24 hr. at 50% relative humidity and 23° C. and a hydrostatic head of at least 55 cm. In one embodiment, the nonwoven substrate comprises a spunbonded nonwoven fabric formed of randomly disposed substantially continuous polypropylene filaments. The spunbonded nonwoven fabric is an area bonded fabric in which the filaments are bonded to one another throughout the fabric at locations where the randomly disposed filaments overlie or cross one another.

Dependencies are inferred from the claim text.