Solvent resistant asymmetric integrally skinned membranes

Abstract

There is provided an asymmetric integrally skinned membrane comprising a polyimide and another polymer selected from the group consisting of polyvinylpyrrolidone, sulfonated polyetheretherketones and mixtures thereof. The membrane which is substantially insoluble in an organic solvent and substantially defect-free can be useful as a separation membrane. Methods for preparing asymmetric integrally skinned polyimide membranes are also disclosed

1 - 36 . (canceled)  
     
     
         37 . A method for purifying natural gas, said method comprising contacting the natural gas with at least one substantially defect-free and substantially insoluble in an organic solvent asymmetric integrally skinned membrane comprising a polyimide and another polymer chosen from polyvinylpyrrolidone, sulfonated polyetheretherketones and mixtures thereof.  
     
     
         38 . The method of  claim 37 , wherein said at least one membrane is a tubular membrane comprising at least one capillary tube and wherein the natural gas is passed through said at least one capillary tube so as to at least partially remove water from said natural gas, thereby obtaining a retentate comprising said purified natural gas and a permeate comprising water.  
     
     
         39 . The method of  claim 38 , further comprising the step of passing the natural gas through another substantially defect-free and substantially insoluble in an organic solvent asymmetric integrally skinned membrane comprising a polyimide and another polymer chosen from polyvinylpyrrolidone, sulfonated polyetheretherketones and mixtures thereof in order to further remove water from said natural gas.  
     
     
         40 . The method of  claim 38 , wherein said other polymer is polyvinylpyrrolidone.  
     
     
         41 . The method of  claim 40 , wherein said polyvinylpyrrolidone has an average molecular weight of about 5,000 to about 500,000 g/mol.  
     
     
         42 . The method of  claim 38 , wherein said membrane has a permeance selectivity of at least 2500 for water/methane, at a temperature of about 50° C.  
     
     
         43 . The method of  claim 38 , wherein said membrane has a permeance selectivity of at least 5000 for water/methane, at a temperature of about 50° C.  
     
     
         44 . The method of  claim 38 , wherein said membrane has a permeance selectivity of at least 15000 for water/methane, at a temperature of about 50° C.  
     
     
         45 . The method of  claim 38 , wherein said organic solvent is N-methylpyrrolidone.  
     
     
         46 . The method of  claim 37 , wherein said polyimide is obtained by curing a polyamic acid, and wherein said polyamic acid is obtained by reacting a dianhydride monomer with a diamine monomer.  
     
     
         47 . The method of  claim 46 , wherein said dianhydride monomer is benzophenone tetracarboxylic dianhydride.  
     
     
         48 . The method of  claim 46 , wherein said diamine monomer is oxydianiline.  
     
     
         49 . The method of  claim 46 , wherein said diamine monomer is diaminodiphenyl sulfone.  
     
     
         50 . The method of  claim 46 , wherein said dianhydride monomer is benzophenone tetracarboxylic dianhydride and said diamine monomer is oxydianiline or diaminodiphenyl sulfone.  
     
     
         51 . The method of  claim 38 , further comprising the step of passing the natural gas through another substantially defect-free and substantially insoluble in an organic solvent asymmetric integrally skinned membrane comprising a polyimide and another polymer chosen from polyvinylpyrrolidone, sulfonated polyetheretherketones and mixtures thereof in order to at least partially remove H 2 S or CO 2  from said natural gas.  
     
     
         52 . A method for concentrating a composition comprising an organic compound and water, or a gas and water, said method comprising contacting the composition with at least one substantially defect-free and substantially insoluble in an organic solvent asymmetric integrally skinned membrane comprising a polyimide and another polymer chosen from polyvinylpyrrolidone, sulfonated polyetheretherketones and mixtures thereof, thereby at least partially removing water from said composition.  
     
     
         53 . The method of  claim 52 , wherein said at least one membrane is a tubular membrane comprising at least one capillary tube and wherein the composition is passed through said at least one capillary tube so as to at least partially remove water from said composition, thereby obtaining a retentate comprising a concentrated composition and a permeate comprising water.  
     
     
         54 . The method of  claim 53 , wherein said composition comprises an organic compound and water, said organic compound being chosen from methanol, ethanol, propanol, acetic acid, ethyl acetate, phenols, benzene, toluene, ethylbenzene, xylene, formaldehyde, formic acid, N-methylpyrrolidone, acetone, and hydrocarbons.  
     
     
         55 . The method of  claim 53 , wherein said composition comprises an organic compound and water, and wherein said organic compound is ethanol.  
     
     
         56 . The method of  claim 53 , wherein said composition comprises a gas and water, and wherein said gas is chosen from C 1 -C 4  hydrocarbons, N 2 , O 2 , CO 2 , and CO.