Novel Coated Membranes and Other Articles

Abstract

The present invention provides porous media or membranes having a surface coating that includes a cross-linked terpolymer which has a superior combination of properties, including heat stable biomolecule resistant adsorptive properties, resistance to strong alkaline solutions, and low levels of extractable matter. In some preferred embodiments, the porous media is a porous membrane.

1 - 31 . (canceled) 
   
   
       32 . A method for the preparation of a clean, caustic resistant porous membrane, said membrane comprising a porous membrane substrate and a heat stable biomolecule resistant surface coating, said method comprising the steps of:
 a. providing a porous membrane substrate;   b. optionally washing said porous membrane substrate with a wetting liquid to wet the surfaces thereof;   c. optionally washing said wet porous membrane substrate with a second wetting liquid to replace said first wetting liquid, leaving said porous membrane substrate wetted with said second liquid;   d. contacting the surfaces of said porous membrane substrate with a solution containing: (1) at least two monofunctional monomers selected from the group consisting of acrylamides, methacrylamides, and N-vinyl pyrrolidones; and (2) at least one polyfunctional monomer selected from the group consisting of polyfunctional acrylamides, polyfunctional methacrylamides and diacroyl piperazines; said solution optionally further comprising one or more polymerization initiators;   e. polymerizing said monomers to form said heat stable biomolecule resistant surface; and   f. washing said membrane.   
   
   
       33 . The method of  claim 32  wherein the sizes of the pores of the porous substrate prior to performing steps (a) through (e) are not significantly different from the sizes of said pores after performing steps (a) through (e). 
   
   
       34 . The method of  claim 32  wherein said porous membrane substrate is a microporous membrane. 
   
   
       35 . The method of  claim 34  wherein said microporous membrane is formed from one or more of the group consisting of aromatic sulfone polymers, polytetrafluoroethylene, perfluorinated thermoplastic polymers, polyolefin polymers, ultrahigh molecular weight polyethylene, and polyvinylidene difluoride. 
   
   
       36 . The method of  claim 35  wherein said porous membrane substrate is a microporous polyvinylidene difluoride membrane. 
   
   
       37 . The method of  claim 32  wherein one of said monofunctional monomers in said reactant solution is an acrylamide, wherein acrylamide nitrogen of said acrylamide is substituted with at least one gem dialkyl substituted carbon. 
   
   
       38 . The method of  claim 32  wherein said polyfunctional monomer is methylene-bis-acrylamide, and said monofunctional monomers are dimethylacrylamide and diacetone acrylamide. 
   
   
       39 . The method of  claim 32  wherein said polyfunctional monomer is methylene-bis-acrylamide, one of said monofunctional monomers is N-vinyl pyrrolidone, and the other of said monofunctional monomers is dimethylacrylamide or diacetone acrylamide. 
   
   
       40 . The method of  claim 38  wherein said porous membrane substrate is a microporous membrane formed from one or more of the group consisting of aromatic sulfone polymers, polytetrafluoroethylene, perfluorinated thermoplastic polymers, polyolefin polymers, ultrahigh molecular weight polyethylene, and polyvinylidene difluoride. 
   
   
       41 . The method of  claim 39  wherein said porous membrane substrate is a microporous membrane formed from one or more of the group consisting of aromatic sulfone polymers, polytetrafluoroethylene, perfluorinated thermoplastic polymers, polyolefin polymers, ultrahigh molecular weight polyethylene, and polyvinylidene difluoride. 
   
   
       42 . The method of  claim 38  wherein said porous membrane substrate is a polyvinylidene difluoride microporous membrane. 
   
   
       43 . The method of  claim 39  wherein said porous membrane substrate is a polyvinylidene difluoride microporous membrane. 
   
   
       44 . The method of  claim 32  wherein said reactant solution comprises: at least one polyfunctional monomer selected from the group consisting of polyfunctional acrylamide monomers, polyfunctional methacrylamide monomers, and diacroylpiperazines; and at least two different monofunctional monomers selected from the group of N-vinyl pyrrolidone monomers and monomers having the general formula: 
     
       
         
         
             
             
         
       
     
     wherein: R 1  is —H or CH 3 , R 2  is H or C 1 -C 6 , preferably C 1 -C 3  alkyl, either linear or branched, R 3  is H or C 1 -C 6 , preferably C 1 -C 3  alkyl, either linear or branched, or C(CH 3 ) 2 CH.sub.2C(═O)CH 3 , or (P═O)((NCH 3 ) 2 ) 2 , or C═ON(CH 3 ) 2 , or CH 2 —O—R 4 , where R 4  is C 1 -C 5  alkyl, either linear or branched, or (CH 2 —CH 2 —O) n —R 5 , where R 5  is —H or —CH 3 , and n=2 or 3; provided that R 2  and R 3  are not simultaneously H. 
   
   
       45 . The method of  claim 38  wherein the reactant solution further comprises a supplemental property modifying monomer. 
   
   
       46 . The method of  claim 39  wherein the reactant solution further comprises a supplemental property modifying monomer. 
   
   
       47 . The method of  claim 45  wherein said supplemental property modifying monomer is selected from the group consisting of (3-(methacryloylamino)propyl)trimethylammonium chloride, (3-acrylamidopropyl)trimethylammonium chloride, 2-acrylamido-2-methyl-1-propanesulfonic acid and aminopropylmethacrylamide. 
   
   
       48 . The method of  claim 46  wherein said supplemental property modifying monomer is selected from the group consisting of (3-(methacryloylamino)propyl)trimethylammonium chloride, (3-acrylamidopropyl)trimethylammonium chloride, 2-acrylamido-2-methyl-1-propanesulfonic acid and aminopropylmethacrylamide. 
   
   
       49 . The method of  claim 32  wherein two of said monofunctional monomers are present in the ratio of about 1 to about 5 by weight. 
   
   
       50 . The method of  claim 32  wherein two of said monofunctional monomers are present in the ratio of about 1 to about 2 by weight. 
   
   
       51 . The method of  claim 32  wherein the total amount of said monofunctional monomers present is from about 0.5% to about 20% by weight. 
   
   
       52 . The method of  claim 32  wherein the total amount of said monofunctional monomers present is from about 2% to about 10% by weight. 
   
   
       53 . The method of  claim 32  wherein the total amount of said monofunctional monomers present is from about 4% to about 8% by weight. 
   
   
       54 . The method of  claim 32  wherein the ratio of the total amount of monofunctional comonomers to polyfunctional crosslinker monomer is about 2 to about 10 by weight. 
   
   
       55 . The method of  claim 32  wherein the ratio of the total amount of monofunctional comonomers to polyfunctional crosslinker monomer is about 2 to about 6 by weight. 
   
   
       56 . The method of  claim 32  wherein the heat stable biomolecule resistant surface is hydrophilic. 
   
   
       57 . The membrane of  claim 32 , wherein said membrane has a biomolecule binding of less than about 30 microgram per square centimeter measured by the IgG binding test. 
   
   
       58 . The membrane of  claim 32 , wherein the membrane has TOC extractables of less than about 1 microgram of extractable matter per square centimeter of membrane as measured by the TOC Extractables test. 
   
   
       59 . The membrane of  claim 32 , wherein the membrane has TOC extractables of less than about 2 micrograms of extractable matter per square centimeter of membrane as measured by the NVR Extractables test. 
   
   
       60 . The membrane of  claim 32 , wherein the membrane has caustic resistance of less than about 1.3 as measured by the Flow Time Measurement test. 
   
   
       61 . A method for removing cells from a solution comprising the steps of: providing a solution comprising having undesired cells; and filtering said solution through a clean, caustic resistant, porous membrane comprising a polyvinylidene difluoride microporous membrane substrate and a heat stable biomolecule resistant surface, wherein said heat stable biomolecule resistant surface is a separately formed surface coating which comprises a crosslinked terpolymer, said crosslinked terpolymer being a copolymer formed from either: (a) methylene-bis-acrylamide, dimethylacrylamide, and diacetone acrylamide; or (b) methylene-bis-acrylamide, N-vinyl pyrrolidone, and either of dimethylacrylamide or diacetone acrylamide. 
   
   
       62 . A method for sterilizing a solution comprising the steps of: providing a nonsterile solution; and filtering said solution through a clean, caustic resistant, porous membrane comprising a polyvinylidene difluoride microporous membrane substrate and a heat stable biomolecule resistant surface, wherein said heat stable biomolecule resistant surface is a separately formed surface coating which comprises a crosslinked terpolymer, said crosslinked terpolymer being a copolymer formed from either: (a) methylene-bis-acrylamide, dimethylacrylamide, and diacetone acrylamide; or (b) methylene-bis-acrylamide, N-vinyl pyrrolidone, and either of dimethylacrylamide or diacetone acrylamide. 
   
   
       63 . A polymer membrane having a surface coating comprising at least one hydroxymethyldiacetoneacrylamide (HMDAA) monomer of formula: 
     
       
         
         
             
             
         
       
     
     wherein R 1  and R 2  are each independently H or CH 2 OH. 
   
   
       64 . The membrane of  claim 63  wherein R 1  and R 2  are each CH 2 OH. 
   
   
       65 . A method of preparing a coated polymer membrane comprising the steps of:
 a. providing a porous membrane substrate;   b. optionally washing said porous membrane substrate with a wetting liquid to wet the surfaces thereof;   c. optionally washing said wet porous membrane substrate with a second wetting liquid to replace said first wetting liquid, leaving said porous membrane substrate wetted with said second liquid;   d. contacting the surfaces of said porous membrane substrate with a solution containing: one or more monofunctional monomers, and at least one monomer hydroxymethyldiacetoneacrylamide (HMDAA) monomer of formula:   
     
       
         
         
             
             
         
       
       wherein R 1  and R 2  are each independently H or CH 2 OH; and 
       e. polymerizing said monomers to form said coated membrane. 
     
   
   
       66 . The method of  claim 64  wherein R 1  and R 2  are each CH 2 OH.