Vapor-permeable, water resistant multicomponent film structure

Claim 1

A multicomponent film structure comprising at least three layers bonded together, (A) wherein the outer layers of the structure are each a continuous layer of a hydrophobic elastomer, (1.3-20.3mm)×10 -3 thick and having a water vapor transmission rate of 400-2500 gm.mil/m 2 /24 hours according to ASTM E96-90 (Procedure BW), said hydrophobic elastomer being comprised of at least one copolyetherester elastomer having a multiplicity of recurring long-chain ester units and short-chain ester units joined head-to-tail through ester linkages, said long-chain ester units being represented by the formula ##STR3## and said short-chain ester units being represented by the formula ##STR4## where G is a divalent radical remaining after the removal of terminal hydroxyl groups from a poly(alkylene oxide) glycol having an average molecular weight of about 400-3500, and further, the amount of ethylene oxide groups incorporated in the copolyetherester or mixture of two or more copolyetheresters by the poly(alkylene oxide) glycol is not greater than about 20 weight percent based upon the total weight of the copolyetherester or mixture of two or more copolyetheresters; R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than 300, D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less then about 250; and said hydrophobic copolyetherester or mixture of two or more copolyetheresters has from about 20-80 weight percent short-chain ester units, and (B) wherein at least one inner layer is a continuous layer of a hydrophilic elastomer, (7.6-152mm)×10 -3 thick and having a water vapor transmission rate of at least 3500 gm.mil/m 2 /24 hours according to ASTM E96-90 (Procedure BW), said hydrophilic elastomer being comprised of at least one copolyetherester elastomer having a multiplicity of long-chain ester units and short-chain ester units joined head-to-tail through ester linkages represented by formulae (I) and (II) above and having the values given above, with the proviso that the amount of ethylene oxide groups incorporated in the copolyetherester or mixture of two or more copolyetheresters by the poly(alkylene oxide) glycol is from about 25-68 weight percent based on the total weight of the copolyetherester or mixture of two or more copolyetheresters, and the hydrophilic copolyetherester, or mixture of two or more copolyetheresters, contain about 20-80 weight percent short-chain ester units.