Supported water vapor transport membrane comprising polyethylene oxide copolymer

Abstract

An air-impermeable water vapor transport membrane comprises an active layer on a microporous polymeric substrate. The active layer comprises a polyethylene-oxide containing copolymer and a polar protic solvent in an amount of about 3% to about 100% of copolymer weight in the active layer. Molecules of the protic solvent are bonded to the copolymer. The polar protic solvent reduces temperature-dependent variability in the water-vapor permeability of the membrane.

1 . (canceled) 
     
     
         2 . A water vapor transport membrane comprising a microporous polymeric substrate and an air-impermeable active layer disposed on the substrate, wherein the active layer comprises a polymer film having portions that are crystalline below a transition temperature, wherein the water vapor permeability of the water vapor transport membrane changes by a factor of at least 2 over a temperature range of 10 degrees Celsius, the transition temperature being within the temperature range. 
     
     
         3 . A water vapor transport membrane according to  claim 2  wherein the water vapor permeability of the water vapor transport membrane changes by a factor of at least 4 over the temperature range of 10 degrees Celsius. 
     
     
         4 . A water vapor transport membrane according to  claim 2  wherein the polymer film comprises a polyethylene-oxide-containing (PEO-containing) copolymer. 
     
     
         5 . A water vapor transport membrane according to  claim 2  wherein the polymer film comprises a cross-linked polyethylene-oxide-containing (PEO-containing) polyurethane copolymer. 
     
     
         6 . A water vapor transport membrane according to  claim 5 , wherein the water vapor transport membrane exhibits FTIR peaks at about 1359 cm −1  and about 1343 cm −1  at a temperature below the transition temperature. 
     
     
         7 . A water vapor transport membrane according to  claim 5 , wherein the water vapor transport membrane exhibits an FTIR peak at about 1349 cm −1  at a temperature above the transition temperature. 
     
     
         8 . A water vapor transport membrane according to  claim 5  wherein about 10% to about 50% by weight of a total weight of the polyurethane copolymer in the active layer is made up by PEO-containing main chains and/or PEO-containing side chains. 
     
     
         9 . A water vapor transport membrane according to  claim 5  wherein the polyurethane copolymer comprises one or both of:
 PEO-containing main chains that have melting point temperatures that are below the transition temperature; and 
 PEO-containing side chains that have melting point temperatures that are below the transition temperature. 
 
     
     
         10 . A water vapor transport membrane according to  claim 9 , wherein the melting point temperatures of the PEO-containing main chains and/or the PEO-containing side chains are in the range of about −15° C. to about 50° C. 
     
     
         11 . A water vapor transport membrane according to  claim 2 , wherein the transition temperature is above 25° C. and below 50° C. 
     
     
         12 . A water vapor transport membrane according to  claim 2 , wherein the substrate comprises a microporous polyolefin. 
     
     
         13 . A water vapor transport membrane according to  claim 12 , wherein the polyolefin is polyethylene (PE) or polypropylene (PP), and the substrate has a thickness of less than about 50 microns and a porosity of at least 30% by volume. 
     
     
         14 . A water vapor transport membrane according to  claim 2  wherein the active layer forms a substantially continuous and dense film on at least a first surface of the substrate, and wherein the loading of the active layer on the substrate is in the range of about 0.5 g/m 2  to about 10 g/m 2 . 
     
     
         15 . A water vapor transport membrane according to  claim 2 , wherein a surface of the substrate contacted by the active layer is substantially free of materials that inhibit crystallization within the polymer film. 
     
     
         16 . A heat and humidity transfer device comprising a water vapor transport membrane, the water vapor transport membrane comprising a microporous polymeric substrate and an air impermeable active layer, wherein the active layer comprises a polymer film having portions that are crystalline below a transition temperature, wherein the water vapor permeability of the water vapor transport membrane changes by a factor of at least 2 over a temperature range of 10 degrees Celsius, the transition temperature being within the temperature range. 
     
     
         17 . A heat and humidity transfer device according to  claim 16  wherein the water vapor permeability of the water vapor transport membrane changes by a factor of at least 4 over a temperature range of 10 degrees Celsius. 
     
     
         18 . A heat and humidity transfer device according to  claim 16  wherein the polymer film comprises a cross-linked polyethylene-oxide-containing (PEO-containing) polyurethane copolymer. 
     
     
         19 . A heat and humidity transfer device according to  claim 18  wherein the polyurethane copolymer comprises one or both of:
 PEO-containing main chains that have melting point temperatures that are below the transition temperature; and 
 PEO-containing side chains that have melting point temperatures that are below the transition temperature. 
 
     
     
         20 . A heat and humidity transfer device according to  claim 18 , wherein the transition temperature is above 25° C. and below 50° C. 
     
     
         21 . A heat and humidity transfer device according to  claim 18 , wherein the substrate comprises a microporous polyolefin having a thickness of less than about 50 microns and a porosity of at least 30% by volume, and wherein the active layer forms a substantially continuous and dense film on at least a first surface of the substrate, and wherein the loading of the active layer on the substrate is in the range of about 0.5 g/m 2  to about 10 g/m 2 . 
     
     
         22 . A method for operating a heat and humidity transfer device, the heat and humidity transfer device comprising a water vapor transport membrane, the water vapor transport membrane comprising a microporous polymeric substrate and an air impermeable active layer, the active layer comprising a polymer film having portions that are crystalline below a transition temperature, wherein the water vapor permeability of the water vapor transport membrane changes by a factor of at least 2 over a temperature range of 10 degrees Celsius, the transition temperature being within the temperature range,
 the method comprising flowing first and second gas streams on opposite sides of the water vapor transport membrane at a temperature above the transition temperature.