Solvent resistant polyamide nanofiltration membranes

Abstract

The present invention relates to a composite membrane for nanofiltration of a feed stream solution comprising a solvent and dissolved solutes and showing preferential rejection of the solutes. The composite membrane comprises a thin polymeric film formed by interfacial polymerisation on a support membrane. The support membrane is further impregnated with a conditioning agent and is stable in polar aprotic solvents. The composite membrane is optionally treated in a quenching medium, where the interfacial polymerisation reaction can be quenched and, in certain embodiments, membrane chemistry can be modified. Finally the composite membrane is treated with an activating solvent prior to nanofiltration.

What is claimed is: 
     
         1 . A composite membrane for nanofiltration of a feed stream solution comprising a solvent and dissolved solutes and showing preferential rejection of the solutes, wherein the composite membrane comprises a thin polymeric film formed by interfacial polymerisation on a support membrane, wherein the support membrane is impregnated with a conditioning agent and is stable in polar aprotic solvents; and wherein the composite membrane is treated with an activating solvent prior to use in nanofiltration. 
     
     
         2 . A membrane according to  claim 1  in which the support membrane is formed from crosslinked polyimide, crosslinked polybenzimidazole, crosslinked polyacrylonitrile, Teflon, polypropylene, or polyether ether ketone (PEEK), or sulfonated polyether ether ketone (S-PEEK). 
     
     
         3 . A membrane according to  claim 2 , where the polyimide used to form the crosslinked polyimide support membrane is at least one copolymer derived from (a) the co-condensation of benzophenone 3,3′,4,4′-tetracarboxylic acid dianhydride and a mixture of (i) di(4-aminophenyl)methane and toluene diamine, or (ii) a mixture of 4,4′-methylenebis(phenyl isocyanate) and toluene diisocyanate; or (b) the condensation of 1H,3H-Benzo[1,2-c:4,5-c′]difuran-1,3,5,7-tetrone with 5,5′-carbonylbis[1,3-isobenzofurandione], 1,3-diisocyanato-2-methylbenzene and 2,4-diisocyanato-1-methylbenzene. 
     
     
         4 . The membrane according to  claim 2 , wherein the polyimide is a polyimide copolymer comprising from 10 to 90% of 
       
         
           
           
               
               
           
         
       
     
     
         5 . A membrane according to  claim 1 , in which the support membrane comprises crosslinks formed from the reaction of aliphatic amines, aliphatic-aromatic amines and aromatic amines with a polyimide polymer. 
     
     
         6 . A membrane according to preceding claims  claim 1  in which the conditioning agent is a non-volatile liquid. 
     
     
         7 .- 15 . (canceled) 
     
     
         16 . Use of the membrane of  claim 1  for nanofiltration of a feed stream solution comprising a solvent and dissolved solutes. 
     
     
         17 . (canceled) 
     
     
         18 . An interfacial polymerisation process for forming a composite membrane for solvent nanofiltration as defined herein, said process comprising the steps of:
 (a) impregnating a porous support membrane comprising a first conditioning agent, with a first reactive monomer solution comprising:   (i) a first solvent for the said first reactive monomer; (ii) a first reactive monomer; (iii) optionally, an activating solvent; and (iv) optionally, additives including alcohols, ketones, ethers, esters, halogenated hydrocarbons, nitrogen-containing compounds and sulphur-containing compounds, monohydric aromatic compounds;   wherein said support membrane is stable in polar aprotic solvents;   (b) contacting the impregnated support membrane with a second reactive monomer solution comprising:   (i) a second solvent for the second reactive monomer; (ii) a second reactive monomer; (iii) optionally, additives including alcohols, ketones, ethers, esters, halogenated hydrocarbons, nitrogen-containing compounds and sulphur-containing compounds, monohydric aromatic compounds;   wherein the first solvent and the second solvent form a two phase system;   (c) after a reaction period, immersing resulting composite membrane into a quench medium;   (d) treating the resulting asymmetric membrane with an activating solvent, and:   (e) optionally, impregnating the resulting composite membrane with a second conditioning agent.   
     
     
         19 . A process according to  claim 18 , wherein the support membrane is formed from crosslinked polyimide, crosslinked polybenzimidazole, crosslinked polyacrylonitrile, Teflon, polypropylene, or polyether ether ketone (PEEK), or sulfonated polyether ether ketone (S-PEEK). 
     
     
         20 . (canceled) 
     
     
         21 . A process according to  claim 18 , wherein the first reactive monomer solution comprises an aqueous solution of a polyamine. 
     
     
         22 . A process according to  claim 18 , wherein the first reactive monomer solution comprises an aqueous solution of a 1,6 hexenediamine or poly(ethyleneimine). 
     
     
         23 . A process according to  claim 18 , wherein the first reactive monomer solution contains one or more of ethylene glycol, propylene glycol, glycerine, polyethylene glycol, polypropylene glycol, and copolymers of ethylene glycol and propylene glycol, and polar aprotic solvents. 
     
     
         24 . A process according to  claim 18 , wherein the second reactive monomer solution optionally contains mono-acyl chlorides, polyacyl chlorides or a mixture thereof, or other monomers. 
     
     
         25 . (canceled) 
     
     
         26 . A process according to  claim 18 , wherein the composite membrane is treated in step (d) with an activating solvent by immersion or by washing in the activating solvent. 
     
     
         27 . A process according to  claim 18 , wherein the composite membrane is treated in step (d) with an activating solvent by filtration through the membrane using the activating solvent. 
     
     
         28 . A process according to  claim 18 , wherein the composite membrane is treated in step (d) with an activating solvent comprising DMF, NMP, DMSO, DMAc, or a mixture thereof. 
     
     
         29 . A process according to  claim 18  in which the contacting time in step (b) is performed in a time between about 5 seconds and about 5 hours. 
     
     
         30 . A process according to  claim 18  in which the temperature of the solution in step (b) is held between about 10° C. and about 100° C. 
     
     
         31 . A process according to  claim 18  in which the second conditioning agent in step (e) is a non-volatile liquid. 
     
     
         32 . A process according to  claim 18  in which the second conditioning agent in step (e) is selected from one or more of synthetic oils mineral oils vegetable fats and oils, higher alcohols glycerols, and glycols. 
     
     
         33 . (canceled)