Vapor-permeable, waterproof bicomponent structure

A bicomponent film of a hydrophobic layer and a hydrophilic layer of copolyetherester elastomers bonded together which permits differential transfer of water vapor to prevent buildup of moisture comprising:

• (A) a continuous layer of a hydrophobic elastomer 0.05-0.8 mil thick and having a water vapor transmission rate of 400-2500 gm.mil/m.sup.2 /24 hrs. according to ASTM E96-66 (Procedure BW), said hydrophobic elastomer is a 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 ##STR7## and said short-chain ester units being represented by the formula:
• ##STR8## 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 by the poly(alkylene oxide)glycol is not greater than about 20 weight percent based upon the total weight of the elastomer;
• 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 than about 250;
• and said hydrophobic copolyetherester has from about 25-80 weight percent short-chain ester units;
• (B) a continuous layer of a hydrophilic elastomer 0.3-6 mil thick and having a water vapor transmission rate of at least 3500 gm.mil/m.sup.2 /24 hrs. according to ASTM E96-66 (Procedure BW), said hydrophilic elastomer is a 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 by the poly(alkylene oxide)glycol is from about 25-68 weight percent based on the total weight of the copolyetherester, and the hydrophilic copolyetherester contains about 25-80 weight percent short-chain ester units;
• and
• said bicomponent film of the hydrophobic and hydrophilic layers has a separation ratio for water vapor of at least 1.4 as determined by ASTM E96-66 (Procedure BW).

A flexible layered product comprising:

• (1) a textile material,
• (2) a bicomponent film of a hydrophobic layer and a hydrophilic layer of copolyetherester elastomers bonded together which permits differential transfer of water vapor to prevent buildup of moisture which comprises,
• (A) a continuous layer of a hydrophobic elastomer 0.05-0.3 mil thick adhered to the textile material and having a water vapor transmission rate of about 800-1200 gm.mil/m.sup.2 /24 hrs., according to ASTM E96-66 (Procedure BW), said hydrophobic elastomer is a 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 ##STR9## and said short-chain ester units being represented by the formula:
• ##STR10## where G is a divalent radical remaining after the removal of terminal hydroxyl groups from a poly(alkylene oxide)glycol having a molecular weight of about 400-3500, and further, the amount of ethylene oxide groups incorporated in the copolyetherester by the poly(alkylene oxide)glycol is not greater than about 20 weight percent based upon the total weight of the elastomer;
• R is a divalent radical remaining after removal of carboxyl groups from an aromatic dicarboxylic acid having a molecular weight less than 300;
• and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250;
• said hydrophobic elastomer has about 30-60 weight percent short-chain ester units;
• (B) a continuous layer of hydrophilic elastomer 0.3-6 mils thick adhered to the hydrophobic layer and having a water vapor transmission rate of about 3500-20,000 gm.mil/m.sup.2 /24 hrs., according to ASTM E96-66 (Procedure BW), said hydrophilic elastomer is a copolyetherester elastomer having a multiplicity of long-chain 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 elastomer by the poly(alkylene oxide)glycol is from about 25-68 weight percent based on the total weight of the elastomer, and the copolyetherester elastomer contains about 40-60 weight percent short-chain ester units;
• and
• said bicomponent film of the hydrophobic and hydrophilic layers has a separation ratio for water vapor of at least about 1.6 as determined by ASTM E96-66 (Procedure BW).