Integral composite membrane

Abstract

A composite membrane is provided which includes a base material and an ion exchange resin. The base material has a microstructure characterized by nodes interconnected by fibrils, or a microstructure characterized by fibrils with no nodes present. The ion exchange resin substantially impregnates the membrane such that the membrane is essentially air impermeable.

Having described the invention, what is claimed is:  
     
       1. A composite membrane comprising  n t least one expanded polytetrafluoroethylene membrane having a porous microstructure of polymeric fibrils and having a thickness of  80  microns or less; and 
       (b) an t least one ion exchange material impregnated throughout the porous microstructure of the expanded polytetraafluoroethylene membrane so as to render an interior volume of the expanded polytetrafluoroethylene membrane substantially occlusive, the impregnated expanded polytetrafluoroethylene membrane having a Gurley number of greater than 10,000 seconds, wherein the ion exchange material substantially impregnates the membrane so as to render an interior volume of the membrane substantially occlusive ; wherein optionally the at least one ion exchange material is complimented by powder, non- ionic polymer, or a combination thereof .  
     
     
       2. The composite membrane of  claim 1 , wherein the expanded polytetrafluoroethylene membrane comprises  consists essentially of a microstructure of nodes interconnected by the fibrils. 
     
     
       3. The composite membrane of  claim 1 , wherein the at least one ion exchange material is selected from a group consisting of: perfluorinated sulfonic acid resin, perfluorinated carboxylic acid resin, polyvinyl alcohol, divinyl benzene, styrene-based polymers, and metal salts. 
     
     
       4. The composite membrane of  claim 1 , wherein the at least one ion exchange material is comprised  complimented at least in part of a  by powder. 
     
     
       5. The composite membrane of  claim 4 , wherein the powder is at least in part carbon. 
     
     
       6. The composite membrane of  claim 4 , wherein the powder is at least in part a metal. 
     
     
       7. The composite membrane of  claim 4 , wherein the powder is at least in part a metal oxide. 
     
     
       8. The composite membrane of  claim 1 , wherein the ion exchange material is a perfluorosulfonic acid/tetrafluoroethylene copolymer resin derived from a solvent solution selected from a group consisting essentially  of water, ethanol, propanol, butanol, and methanol. 
     
     
       9. The composite membrane of  claim 1 , wherein the ion exchange material is at least in part a  complimented by non-ionic polymer. 
     
     
       10. The composite membrane of  claim 9 , wherein the non- ionic polymer is thermoplastic resin.   
     
     
       11. The composite membrane of  claim 9 , wherein the non- ionic polymer is a thermoset resin.   
     
     
       12. The composite membrane of  claim 9 , wherein the non- ionic polymer is polyolefin or fluoropolymer.   
     
     
       13. The composite membrane of  claim 4 , wherein the powder is finely divided. 
     
     
       14. The composite membrane of  claim 4 , wherein the powder is an organic powder. 
     
     
       15. The composite membrane of  claim 4 , wherein the powder is an inorganic powder. 
     
     
       16. The composite membrane of  claim 4 , wherein the powder is selected from the group consisting of carbon black, graphite, nickel, silica, titanium dioxide, and platinum black. 
     
     
       17. The composite membrane of  claim 4 , wherein the powder is carbon black. 
     
     
       18. The composite membrane of  claim 4 , wherein the powder is graphite. 
     
     
       19. The composite membrane of  claim 4 , wherein the powder is silica. 
     
     
       20. The composite membrane of  claim 4 , wherein the powder is titanium dioxide. 
     
     
       21. The composite membrane of  claim 4 , wherein the powder is platinum black. 
     
     
       22. The composite membrane of  claim 1 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  60  microns or less. 
     
     
       23. The composite membrane of  claim 1 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  40  microns or less. 
     
     
       24. The composite membrane of  claim 1 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  20  microns or less. 
     
     
       25. The composite membrane of  claim 1 , wherein the thickness of the expanded polytetrafluoroethylene membrane is at least  1 . 5  microns. 
     
     
       26. The composite membrane of  claim 1 , wherein the thickness of the expanded polytetrafluoroethylene membrane is at least  13  microns. 
     
     
       27. A composite membrane according to  claim 1 , wherein the impregnated membrane has an ionic conductance of at least  8 . 5  mhos/cm 2 . 
     
     
       28. A composite membrane according to  claim 1 , wherein the impregnated membrane has an ionic conductance of at least  22 . 7  mhos/cm 2 . 
     
     
       29. A composite membrane according to  claim 1 , wherein the impregnated membrane has been heated to a temperature of  60 ° C. to  200 ° C. 
     
     
       30. A composite membrane according to  claim 29 , wherein the impregnated membrane has an ionic conductance of at least  8 . 5  mhos/cm 2 . 
     
     
       31. A composite membrane according to  claim 30 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  20  microns or less and the ion exchange material is perfluorinated sulfonic acid resin. 
     
     
       32. A composite membrane according to  claim 31 , wherein the impregnated membrane is prepared by impregnation of at least two sides of the expanded polytetrafluoroethylene membrane with the ion exchange material. 
     
     
       33. A composite membrane according to  claim 32 , wherein the impregnation is carried out by multiple impregnations of the at least two sides of expanded polytetrafluoroethylene membrane. 
     
     
       34. A composite membrane according to  claim 29 , wherein the impregnated membrane has an ionic conductance of at least  22 . 7  mhos/cm 2 . 
     
     
       35. A composite membrane according to  claim 1 , wherein the impregnated membrane has been heated to a temperature of  120 ° C. to  200 ° C. 
     
     
       36. A composite membrane according to  claim 1 , wherein the impregnated membrane has been heated to a temperature of  140 ° C. to  200 ° C. 
     
     
       37. A laminate of composite membranes consisting essentially of at least two composite membranes laminated to each other, wherein the at least two composite membranes each consist essentially of: 
       ( a )  an expanded polytetrafluoroethylene membrane having a porous microstructure of polymeric fibrils and having a thickness of  80  microns or less; and    
       ( b )  an ion exchange material impregnated throughout the porous microstructure of the membrane so as to render an interior volume of the expanded polytetrafluoroethylene membrane substantially occlusive, the impregnated membrane having a Gurley number of greater than  10 , 000  seconds.   
     
     
       38. A laminate according to  claim 37 , wherein each of the impregnated polytetrafluoroethylene membranes have been heated to a temperature of at least  60 ° C. and each of the impregnated membranes have an ionic conductance of at least  22 . 7  mhos/cm 2   ; wherein the thickness of each of the impregnated membranes is  20  microns or less; wherein the ion exchange material is perfluorinated sulfonic acid resin; wherein each of the impregnated membranes are prepared by multiple impregnations of two sides of the expanded polytetrafluoroethylene membrane with ion exchange material.   
     
     
       39. A laminate according to  claim 38 , wherein the thickness of the laminate is  40  microns or less. 
     
     
       40. A laminate according to  claim 38 , wherein at least two of the impregnated membranes are impregnated with ion exchange material before lamination to form the laminate. 
     
     
       41. A laminate according to  claim 37 , wherein the thickness of the laminate is  40  microns or less. 
     
     
       42. A laminate according to  claim 37 , wherein at least two of the impregnated membranes are impregnated with ion exchange material before lamination to form the laminate. 
     
     
       43. A laminate according to  claim 37 , wherein the laminate is prepared by ( i )  impregnation of at least one first unimpregnated expanded polytetrafluoroethylene membrane with ion exchange material to form a first impregnated membrane,  ( ii )  lamination of the first impregnated membrane with a second unimpregnated expanded polytetrafluoroethylene membrane, and  ( iii )  impregnation of the second unimpregnated expanded polytetrafluoroethylene to form a second impregnated membrane which is laminated to the first impregnated membrane.   
     
     
       44. A laminate according to  claim 37 , wherein lamination is carried out with heat. 
     
     
       45. A membrane comprising: 
       ( a )  at least one expanded polytetrafluoroethylene membrane having a porous microstructure of polymeric fibrils; and    
       ( b )  at least one ion exchange material impregnated throughout the porous microstructure of the membrane so as to render an interior volume of the expanded polytetrafluoroethylene membrane substantially occlusive, the impregnated expanded polytetrafluoroethylene membrane having a Gurley number of greater than  10 , 000  seconds, wherein powder is included with the at least one ion exchange material.   
     
     
       46. A membrane according to  claim 45 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  80  microns or less. 
     
     
       47. A membrane according to  claim 45 , wherein the thickness of the expanded polytetrafluoroethylene membrane is  20  microns or less. 
     
     
       48. A membrane according to  claim 47 , wherein the impregnated membrane has an ionic conductivity of at least  8 . 5  mhos/cm 2 . 
     
     
       49. A membrane according to  claim 47 , wherein the impregnated membrane has an ionic conductivity of at least  22 . 7  mhos/cm 2 . 
     
     
       50. A membrane according to  claim 45 , wherein the impregnated membrane has an ionic conductivity of at least  8 . 5  mhos/cm 2 . 
     
     
       51. A membrane according to  claim 45 , wherein the impregnated membrane has an ionic conductivity of at least  22 . 7  mhos/cm 2 . 
     
     
       52. A membrane consisting essentially of: 
       ( a )  at least one expanded base membrane having a porous microstructure of polymeric fibrils and having a thickness of  80  microns or less; and    
       ( b )  at least one ion exchange material impregnated throughout the porous microstructure of the expanded base membrane so as to render an interior volume of the base membrane substantially occlusive the impregnated expanded base membrane having a Gurley number of greater than  10 , 000  seconds.   
     
     
       53. A membrane according to  claim 52 , wherein the impregnated membrane has a thickness of  20  microns or less and an ionic conductivity of at least  8 . 5  mhos/cm 2 . 
     
     
       54. A membrane according to  claim 52 , wherein the impregnated membrane has an ionic conductivity of at least  22 . 7  mhos/cm 2 . 
     
     
       55. A membrane according to  claim 54 , wherein the impregnated membrane is heated to between  120 ° C. and  200 ° C. 
     
     
       56. A composite membrane consisting essentially of: 
       ( a )  at least one expanded polytetrafluoroethylene membrane having a porous microstructure of polymeric fibrils and having a thickness of  80  microns or less; and    
       ( b )  at least one ion exchange material impregnated throughout the porous microstructure of the expanded polytetrafluoroethylene membrane so as to render an interior volume of the expanded polytetrafluoroethylene membrane substantially occlusive, the impregnated membrane not allowing for fluid percolation.   
     
     
       57. A composite membrane according to  claim 56 , wherein the ionic conductivity of the impregnated membrane is at least  8 . 5  mhos/cm 2    and the impregnated membrane is heated to between  120 ° C. and  200 ° C.   
     
     
       58. A composite membrane according to  claim 56 , wherein the thickness of the composite membrane and the thickness of the impregnated expanded polytetrafluoroethylene membrane are substantially the same. 
     
     
       59. A composite membrane according to  claim 56 , wherein a side of the composite membrane is laminated to a support structure, and the ion exchange material is impregnated throughout the porous microstructure of the expanded polytetrafluoroethylene membrane from a side opposite to side laminated to the support structure. 
     
     
       60. A composite membrane according to  claim 56 , wherein the ion exchange material is impregnated throughout the porous microstructure of the expanded polytetrafluoroethylene membrane by simultaneous treatment of both sides of the expanded polytetrafluoroethylene membrane. 
     
     
       61. A composite membrane according to  claim 56 , wherein the ion exchange material is uniformly impregnated throughout the porous microstructure of the expanded polytetrafluoroethylene membrane, and the composite membrane has no porous surfaces exposed.