Patent ID: 7931964

Claim:
A microporous layer comprising a microporous xerogel comprising pores that are substantially continuously interconnected from a first outermost surface of the microporous xerogel through to a second outermost surface of the microporous xerogel; and a crosslinked polymer binder comprising a polymer and a crosslinking agent, the crosslinked polymer binder having a glass transition temperature of about 50° C. or higher, wherein the polymer binder is water soluble prior to crosslinking; wherein the crosslinking agent comprises an aldehyde or thermosetting polymer and wherein the crosslinking agent in the polymer is present in an amount of about 40 to about 80 mole percent; wherein the crosslinked polymer binder is present in an amount of 5 to 70 wt. % by weight of the sol in the xerogel-forming composition and wherein the xerogel-forming composition comprises about 10 to 30 percent solids; wherein the microporous xerogel comprises a pseudo-boehmite, zirconium oxide, titanium oxide, barium oxide, silicon oxide, aluminum oxide, tin oxide, or a combination comprising at least one of the foregoing oxides; wherein the polymer is a polyvinyl alcohol, a copolymer of a polyvinyl acetate and a polyvinyl pyrrolidone, a copolymer of polyvinyl alcohol and a polyvinyl pyrrolidone, or a combinations comprising at least one of the foregoing polymers; wherein the glass transition temperature of the polymer changes by less than about 25% after exposure to water; and wherein the microporous xerogel has a porosity of 40 to 80%.