Breathable clothlike barrier having controlled structure defensive composite

摘要

A breathable clothlike barrier which includes a defensive composite having at least two layers: A. a first layer which is a clothlike porous substrate having a first side and a second side, in which: the first layer has a nominal basis weight of at least about 10 g/m2; the fibers comprising the first layer have an average fiber diameter in the range of from about 0.01 to about 10 microns; and each of substantially all of the pores at the surface of the first side of the first layer has a cross-sectional area of from about 6x10-16 m2 to about 2x10-9 m2; and B. a second layer joined to the first side of the first layer, which second layer is a continuous film of a poly(vinyl alcohol), in which: the film is not microporous in that it is substantially free of voids which connect the two surfaces of the film; and the film has an average thickness of (a) from about 3 to about 25 microns when the basis weight of the first layer is at least about 20 g/m2 or (b) from about 8 to about 25 microns when the basis weight of the first layer is from about 10 to less than about 20 g/m2; in which the first layer side of the second layer is intimately comingled with at least some of the fibers at the surface of the first side of the first layer, and the defensive composite has a water vapor transmission rate at 37 degrees C. and about 50 percent relative humidity of from about 100 to about 5,000 g/m2/24 hours and is impermeable to 0.9 percent by weight saline solution at about 21 degrees C. for a period of at least about one hour at a hydrostatic head of at least about 11.4 cm.