Membranes and methods of manufacture thereof

Abstract

A polymeric membrane system containing a polymeric membrane and a substrate with interstitial gaps. Polymeric membrane components reside within the interstitial gaps of the substrate and below the surface of the substrate. Also, the layer of polymeric membrane components is thinner than the cross-sectional thickness of the substrate.

1 . A polymeric membrane system comprising a substrate and a polymeric membrane, wherein the substrate comprises a plurality of interstitial gaps therein and wherein the polymeric membrane comprises polymeric membrane components spanning the interstitial gaps of the support, the polymeric membrane components being thinner than the substrate.  
     
     
         2 . A polymeric membrane system according to  claim 1  containing no detectable soluble entity.  
     
     
         3 . A polymeric membrane system according to  claim 2  containing no detectable water-soluble entities.  
     
     
         4 . A polymeric membrane system according to  claim 2  containing no detectable organic solvent soluble entities.  
     
     
         5 . A polymeric membrane system according to  claim 2  wherein the soluble entity is a monomer.  
     
     
         6 . A polymeric membrane system according to any one of the preceding claims wherein the thickness of the polymeric membrane components is in the range of about 0.01 to 0.5 mm.  
     
     
         7 . A polymeric membrane system according to  claim 4  wherein the thickness of the polymeric membrane is in the range of about 0.01 to 0.1 mm.  
     
     
         8 . A polymeric membrane system according to any one of the preceding claims wherein the polymer membrane is an ultrathin membrane.  
     
     
         9 . A polymeric membrane system according to any one of the preceding claims wherein the polymeric membrane is a hydrophilic polymer membrane.  
     
     
         10 . A polymeric membrane system according to any one of  claims 1  to  8  wherein the polymeric membrane is a hydrophobic polymer membrane.  
     
     
         11 . A polymeric membrane according to any one of the preceding claims, wherein the polymeric membrane is formed from a crosslinked polymer.  
     
     
         12 . A polymeric membrane system according to  claim 11  wherein the polymeric membrane is a polyacrylamide gel.  
     
     
         13 . A polymeric membrane system according to  claim 11  wherein the polymeric membrane is a gel of PolyHEMA crosslinked with EDGMA  
     
     
         14 . A polymeric membrane system according to  claim 12  wherein the polyacrylamide gel is formed from monomers having the formula H 2 C═CR 5 —CO—NR 3 R 4  where R 3 , R 4  and R 5  are each independently H or alkyl optionally monosubstituted by, for OH or C(O)CH 2 C(O) CH 3 .  
     
     
         15 . A polymeric membrane system according to  claim 12  or  claim 14  wherein the polyacrylamide gel wherein the crosslinking agent is selected from N,N′-methylene bisacrylamide (BIS), ethylene glycol diacrylate, dihydroxy ethylene-bisacrylamide (DHEBA), N,N′-propylenebisacrylamide, diacrylamide dimethylether, 1,2-diacrylamide ethyleneglycol, ethyleneureabisacrylamide, N,N′-bisacrylylcystamine and bisacrylamide methylether (BAME).  
     
     
         16 . A polymeric membrane system according to any one of  claims 14  to  15  wherein the polyacrylamide gel is produced by using AAm and the crosslinker monomer with the following formula:  
       
         
           
           
               
               
           
         
         wherein X and X′ are independently selected from the group consisting of —O—, —S—and —NR—, where R is H, alkyl or cycloalkyl,  
         R 1 ,R 2  is a C 1 -C 4  alkyl group,  
         Y is an optionally substituted non-aromatic divalent linking group, and  
         Z is O or S.  
       
     
     
         17 . A polymeric membrane system according to  claim 14  wherein the crosslinker is a combination of crosslinkers at least one of which has at least three crosslinkable functional groups, wherein at least one of the crosslinkable functional groups is the group CH 2 ═C(R)—CO—, where R is H or optionally substituted alkyl.  
     
     
         18 . A polymeric membrane system according to  claim 17  wherein the crosslinker having at least three crosslinkable functional groups is a compound of Formula I or Formula II  
       
         
           
           
               
               
           
         
         wherein, in Formula I:  
         C represents a ring structure of the crosslinker molecule which is connected with at least 3 functional groups —Y—CZC(R)═CH 2  which functional groups may be the same or different;  
         Y in each functional group is independently selected from single bond, N, O or S;  
         Z in each functional group is independently selected from O or S; or Z may be two hydrogens, a hydrogen an optionally substituted alkyl, or two optionally substituted alkyl groups, and  
         R in each functional group may be the same or different and selected from hydrogen or optionally substituted alkyl; and  
         In Formula II:  
         D represents a backbone chain of the crosslinker which is connected with at least three functional groups —Y—CZC(R)═CH 2  which functional groups are the same or different;  
         Y in each functional group is the same or different and selected from the group consisting of a single bond, N, O or S;  
         Z in each functional group may is the same or different and selected from O or S; and  
         R in each functional group is the same or different and selected from hydrogen or optionally substituted alkyl.  
       
     
     
         19 . A polymeric membrane system according to any one of the preceding claims, wherein the substrate is a woven or non-woven fabric or material.  
     
     
         20 . A polymeric membrane system according to any one of the preceding claims, wherein the substrate is formed from a material selected from the group consisting of polyvinyl alcohol, polyethyleneterapthalate, nylon and fiberglass.  
     
     
         21 . A crosslinked polymeric membrane system according to  claim 20 , wherein the substrate is a polyvinyl alcohol sheet.  
     
     
         22 . A crosslinked polymeric membrane system according to  claim 20 , wherein the substrate is formed from a non-woven polyethyleneterapthalate sheet, optionally treated with non-ionic surfactant.  
     
     
         23 . A method for production of a polymeric membrane system comprising a substrate and a polymeric membrane, wherein the substrate comprises a plurality of interstitial gaps therein and wherein the polymeric membrane comprises polymeric membrane components spanning the interstitial gaps of the support, the polymeric membrane components being thinner that the substrate, the method comprising contacting a substrate having a plurality of interstitial gaps therein with at least one membrane-forming monomer and at least one crosslinker and subjecting the at least one monomer to polymerization and thereafter subjecting the polymeric membrane system to at least one solvent wash.  
     
     
         24 . A method according to  claim 23  wherein the polymeric membrane contains no detectable soluble entity/entities.  
     
     
         25 . A method according to  claim 24  wherein the soluble entity/entities is/are water soluble and wherein the solvent is water.  
     
     
         26 . A method according to  claim 24  or  claim 25  wherein the soluble entity is a monomer.  
     
     
         27 . A method according to any one of  claims 23  to  26  wherein the thickness of the polymeric membrane components is in the range of about 0.01 to 0.5 mm.  
     
     
         28 . A method according to  claim 27  wherein the thickness of the polymeric membrane is in the range of about 0.01 to 0.1 mm.  
     
     
         29 . A method according to any one of  claims 23  to  28  wherein the polymer membrane is an ultrathin membrane.  
     
     
         30 . A method according to any one of  claims 23  to  29  wherein the substrate is subjected to degassing prior to being contacted with the monomer(s).  
     
     
         31 . A method according to any one of  claims 23  to  30  wherein polymerization of the monomer is initiated by a photo, redox or thermal method.  
     
     
         32 . A method according to  claim 31  wherein the polymerization is carried out using free-radical polymerization or photoinitiation.  
     
     
         33 . A method according to  claim 32  wherein, the polymerization is carried out in a substantially oxygen-free atmosphere.  
     
     
         34 . A method according to any one of  claims 23  to  33  wherein the polymeric membrane system is according to any one of  claims 9  to  22 .  
     
     
         35 . A method according to any one of  claims 23  to  34  wherein the process includes the step of monitoring the soluble entity/entities and, if necessary, repeating the solvent wash until the soluble entity/entities are undetectable.  
     
     
         36 . A method according to  claim 35  wherein said monitoring is carried out by an on-line detection system with feed back to the solvent wash step.