Composite Membrane and Moisture Adjustment Module Using Same

1 . A composite membrane wherein:

a moisture-permeable resin layer is interposed between porous membranes that constitute a pair; and

the mean thickness of the moisture-permeable resin layer is 5 μm or less.

2 . The composite membrane according to claim 1 , wherein said moisture-permeable resin comprises a water-resistant, moisture-permeable resin.

3 . The composite membrane according to claim 2 , wherein the degree of swelling of said water-resistant, moisture-permeable resin, is 20 times or less.

4 . The composite membrane according to claim 2 wherein said water-resistant, moisture-permeable resin comprises a crosslinked polyvinyl alcohol.

5 . The composite membrane according to claim 2 , wherein said water-resistant, moisture-permeable resin comprises an ion-exchange fluororesin.

6 . The composite membrane according to claim 5 , wherein said water-resistant, moisture-permeable resin comprises a perfluorosulfonic acid polymer.

7 . The composite membrane according to claim 3 wherein said water-resistant, moisture-permeable resin comprises a crosslinked polyvinyl alcohol.

8 . The composite membrane according to claim 1 wherein at least part of said moisture-permeable resin is embedded in the porous membrane.

9 . The composite membrane according claim 4 wherein at least part of said moisture-permeable resin is embedded in the porous membrane.

10 . The composite membrane according claim 6 wherein at least part of said moisture-permeable resin is embedded in the porous membrane.

11 . The composite membrane according claims 1 wherein:

the mean pore diameter of the said porous membranes is 0.05 μm or greater; and

the maximum pore diameter is 15 μm or less.

12 . The composite membrane according claims 4 wherein:

the mean pore diameter of said porous membranes is 0.05 μm or greater; and the maximum pore diameter is 15 μm or less.

13 . The composite membrane according claims 6 wherein:

the mean pore diameter of said porous membranes is 0.05 μm or greater; and the maximum pore diameter is 15 μm or less.

14 . The composite membrane according to claim 1 wherein the void content of the said porous membranes is 40% or greater.

15 . The composite membrane according to claim 4 wherein the void content of the said porous membranes is 40% or greater.

16 . The composite membrane according to claim 6 wherein the void content of the said porous membranes is 40% or greater.

17 . The composite membrane according to claim 1 wherein the mean thickness of said porous membranes is 1 to 200 μm.

18 . The composite membrane according to claim 4 wherein the mean thickness of said porous membranes is 1 to 200 μm.

19 . The composite membrane according to claim 6 wherein the mean thickness of said porous membranes is 1 to 200 μm.

20 . The composite membrane according to any of claims 1 wherein at least one of said porous membranes comprises a expanded polytetrafluoroethylene membrane.

21 . The composite membrane according to any of claims 4 wherein at least one of said porous membranes comprises a expanded polytetrafluoroethylene membrane.

22 . The composite membrane according to any of claims 6 wherein at least one of said porous membranes comprises a expanded polytetrafluoroethylene membrane.

23 . The composite membrane according to claims 1 wherein a gas-permeable reinforcing element is layered on at least one of the porous membranes.

24 . The composite membrane according to claims 4 wherein a gas-permeable reinforcing element is layered on at least one of the porous membranes.

25 . The composite membrane according to claims 6 wherein a gas-permeable reinforcing element is layered on at least one of the porous membranes.

26 . A moisture adjustment module, obtained by superposing the composite membrane of claims 1 while open spaces are left therebetween.

27 . A moisture adjustment module, obtained by superposing the composite membrane of claims 4 while open spaces are left therebetween.

28 . A moisture adjustment module, obtained by superposing the composite membrane of claim 6 while open spaces are left therebetween.

29 . A composite membrane wherein an air-impermeable layer comprising a perfluorosulfonic acid polymer is interposed between a first and second micro-porous membrane.

30 . A composite membrane of claim 29 wherein at least one of said first and second micro-porous membranes is hydrophobic.

31 . A composite membrane of claim 29 wherein at least one of said first and second micro-porous membranes is hydrophilic.

32 . A composite membrane of claim 29 wherein said perfluorosulfonic acid polymer further comprises a reinforcement.

33 . A composite membrane of claim 29 wherein said air impermeable layer has a mean thickness less than 20 um.

34 . The composite membrane according to claim 29 wherein at least part of said impermeable layer is embedded in the micro-porous membrane.

35 . The composite membrane according to claim 29 wherein at least one of said first and second micro-porous layers comprises expanded polytetrafluoroethylene.

36 . A composite membrane of claim 32 wherein said reinforcement comprises particulates.

37 . A composite membrane of claim 32 wherein said reinforcement comprises a third micro-porous membrane.

38 . A composite membrane of claim 37 wherein said third micro-porous membrane comprises expanded polytetrafluoroethylene.

39 . A composite membrane of claim 29 wherein at least one of said first and second micro-porous membranes has a reinforcing member attached to it.

40 . A moisture-permselective membrane of claim 39 wherein said reinforcing member is a non-woven material.

41 . A moisture-permselective membrane of claim 39 wherein said reinforcing member is a woven material.

42 . A moisture adjustment module, obtained by superposing the composite membrane of claims 29 while open spaces are left therebetween.

43 . A moisture adjustment module, obtained by superposing the composite membrane of claims 32 while open spaces are left therebetween.

44 . A method of preparing a composite membrane comprising the steps of

a. Casting a solution comprising a moisture permselective resin on a first micro-porous membrane to form a film on the surface of said micro-porous membrane;

b. Stretching a second micro-porous membrane over said film before it is dry to form a composite structure;

c. Drying said composite structure to remove residual liquid from said solution.

45 . A method of claim 44 wherein said film is between 0.5 and 10 um thick after step c.

46 . A method of claim 44 wherein an additional step of heat-treating said composite membrane after step (c) is performed.

47 . The method of claim 44 wherein a reinforcing member is laminated to at least one side of said composite membrane after step c.

48 . A method of claim 46 wherein said heat treatment comprises holding said composite membrane at a temperature between 100 and 180 C for a period of time between 1 and 15 minutes.

49 . A method of preparing a composite membrane comprising the steps of:

a. Preparing a membrane having two sides, said membrane comprising a moisture permselective resin;

b. Laminating one side of said membrane to a first micro-porous membrane;

c. Laminating a second micro-porous membrane to the second side of said membrane.

50 . The method of claim 49 wherein at least one of the first micro-porous membrane and the second micro-porous membrane comprise expanded polytetrafluoroethylene.

51 . The method of claim 49 wherein said membrane comprising moisture permselective resin further comprises expanded polytetrafluoroethylene.

52 . The method of claim 49 wherein said membrane comprising moisture permselective resin comprises a perfluorosulfonic acid polymer.

53 . The method of claim 49 wherein a reinforcing member is laminated to at least one side of said composite membrane after step c.

54 . The method of claim 49 wherein said membrane comprising moisture permselective resin in step (a) has a mean thickness of less than 15 μm.

55 . The method of claim 49 wherein said membrane comprising moisture permselective resin in step (a) has a mean thickness of less than 6 μm.

56 . A composite membrane wherein an air-impermeable layer comprising an ionomeric polymer is interposed between a first and second micro-porous membrane.

57 . A composite membrane of claim 56 wherein at least one of said first and second micro-porous membranes is hydrophobic.

58 . A composite membrane of claim 56 wherein at least one of said first and second micro-porous membranes is hydrophilic.

59 . A composite membrane of claim 56 wherein said perfluorosulfonic acid polymer further comprises a reinforcement.

60 . A composite membrane of claim 56 wherein said air impermeable layer has a mean thickness less than 20 um.

61 . The composite membrane according to claim 56 wherein at least part of said impermeable layer is embedded in the micro-porous membrane.

62 . The composite membrane according to claim 56 wherein at least one of said first and second micro-porous layers comprises expanded polytetrafluoroethylene.

63 . A composite membrane of claim 59 wherein said reinforcement comprises particulates.

64 . A composite membrane of claim 59 wherein said reinforcement comprises a third micro-porous membrane.

65 . A composite membrane of claim 64 wherein said third micro-porous membrane comprises expanded polytetrafluoroethylene.

66 . A composite membrane of claim 56 wherein at least one of said first and second micro-porous membranes has a reinforcing member attached to it.

67 . A moisture-permselective membrane of claim 66 wherein said reinforcing member is a non-woven material.

68 . A moisture-permselective membrane of claim 66 wherein said reinforcing member is a woven material.

69 . A moisture adjustment module, obtained by superposing the composite membrane of claims 56 while open spaces are left therebetween.

70 . A moisture adjustment module, obtained by superposing the composite membrane of claims 59 while open spaces are left therebetween.