Modified membranes
View Patent ↗A porous polymeric membrane formed from a blend of a polymeric membrane forming material, such as polyvinylidene fluoride or polysulfone and a polymeric reactivity modifying agent adapted to modify the surface active properties of the porous polymeric membrane. The reactivity modifying agent is preferably a linear polymeric anhydride, such as poly(alkyl vinyl ether/maleic anhydride). The surface activity modifications include modification of the hydrophilicity/hydrophobicity balance of the membrane, or hydrolysis followed by reaction with a polyamine to form a crosslinked polyamide layer. Such modified membranes have use as reverse osmosis membranes.
1. A method of preparing a microporous polymeric membrane comprising the steps of:
blending a polymeric membrane forming material and a reactivity modifying agent comprising polymeric anhydride in an amount such that a combined precursor to the microporous polymeric membrane forms a single phase mixture and thereby obtaining a blended material having between 3.1% and 3.4% polymeric anhydride; and
casting the microporous polymeric membrane from the blended material.
2. The method according to claim 1 , wherein the reactivity modifying agent is blended with the polymeric membrane forming material in an unreacted form.
3. The method according to claim 1 , wherein the reactivity modifying agent is blended with the polymeric membrane forming material in a reacted form.
4. The method according to claim 1 , wherein the reactivity modifying agent blended with the polymeric porous membrane forming material is subjected to a chemical modification subsequent to the step of casting.
5. The method according to claim 4 , wherein the chemical modification comprises hydrolysis whereby the microporous polymeric membrane is rendered hydrophilic.
6. The method according to claim 4 , wherein the chemical modification comprises crosslinking.
7. The method according to claim 1 , wherein the microporous polymeric membrane comprises a hollow fibre membrane.
8. The method according to claim 1 , wherein the microporous polymeric membrane comprises a flat sheet membrane.
9. The method according to claim 1 , wherein the microporous polymeric membrane is cast from a dope solution comprising a polymer.
10. The method according to claim 9 , wherein the dope solution comprises at least one polymer selected from the group consisting of a polyvinylidene fluoride, a sulfone polymer, and a polyvinylpyrrolidone copolymer.
11. The method according to claim 10 , wherein the dope solution comprises about 16.8 to about 17.2% polyvinylidene fluoride.
12. The method according to claim 10 , wherein the dope solution comprises about 2.6 to about 2.7% polyvinylpyrrolidone/vinyl acetate copolymer.
13. The method according to claim 1 , wherein the microporous polymeric membrane is cast from a dope solution comprising an organic solvent.
14. The method according to claim 13 , wherein the organic solvent comprises N-methylpyrrolidone.
15. The method according to claim 14 , wherein dope solution comprises about 73.7 to about 77.3% N-methylpyrrolidone.
16. The method according to claim 1 , wherein the porous polymeric membrane is formed from a dope solution comprising a linear polymeric anhydride.
17. The method according to claim 16 , wherein the linear polymeric anhydride comprises poly(methyl vinyl ether/maleic anhydride).
18. The method according to claim 17 , wherein the dope solution comprises about 3.1% to about 3.4% poly(methyl vinyl ether/maleic anhydride).
19. The method according to claim 1 , wherein the porous polymeric membrane is cast from a dope solution comprising a salt.
20. The method according to claim 19 , wherein the salt comprises LiCl.
21. The method according to claim 20 , wherein the dope solution comprises about 3.0 to about 3.8% LiCl.
22. The method according to claim 1 , wherein the microporous polymeric membrane is cast from a dope solution comprising 17% polyvinylidene fluoride; 3.5% LiCl; 2.7% polyvinylpyrrolidone/vinyl acetate copolymer; 3.1% poly(methyl vinyl ether/maleic anhydride); and 73.7% N-methylpyrrolidone.
23. The method according to claim 1 , wherein the microporous polymeric membrane is formed from a dope solution comprising 16.8% polyvinylidene fluoride; 3.4% poly(methyl vinyl ether/maleic anhydride); 3.8% LiCl; and 76% N-methylpyrrolidone.
24. The method according to claim 1 , wherein the reactivity modifying agent and polymeric membrane forming material are selected such that a melt comprising the reactivity modifying agent and polymeric membrane forming material is thermodynamically stable and no demixing process occurs in the melt.
25. The method according to claim 1 , wherein the reactivity modifying agent, polymeric membrane forming material, and reaction conditions are selected such that no gelation occurs during casting the membrane.
26. The method according to claim 1 , further including a step of mixing the dope solution at about 50° C. overnight.
27. The method according to claim 26 , wherein the dope solution is formed by a diffusion induced phase separation procedure in a precipitation bath comprising water.
28. The method according to claim 26 , wherein the dope solution is formed by a diffusion induced phase separation procedure in a precipitation bath comprising polyethylene glycol.
29. The method according to claim 26 , wherein the dope solution is formed by a diffusion induced phase separation procedure in a precipitation bath comprising N-methyl pyrrolidone.
30. The method according to claim 26 , wherein the dope solution is formed by a diffusion induced phase separation procedure in a precipitation bath comprising 45% polyethylene glycol 200; 45% water; and 10% N-methylpyrrolidone.
31. A method of preparing a porous polymeric membrane, the method comprising the steps of:
blending a polymeric membrane forming material and a polymeric anhydride into a single phase blended material;
casting a porous polymeric membrane from the blended material; and
chemically modifying at least a portion of the polymeric anhydride blended into the polymeric porous membrane forming material with one or more substances selected from the group consisting of tetraethylenepentamine, tris-(hydroxymethyl) aminomethane, sulfuric acid, polyethylene glycol, and calcium carbonate.
32. The method according to claim 4 , wherein the chemical modification comprises treatment with a crosslinking amine to form amide linkages.
33. A method of modifying a surface of a microporous polymer membrane comprising the steps of:
blending a reactivity modifying agent comprising a poly (methyl vinyl ether/maleic anhydride) with a polymeric membrane forming material, wherein the reactivity modifying agent is blended in an amount such that a combined precursor to the porous polymeric membrane forms a single phase mixture; and
casting the microporous membrane.
34. The method according to claim 33 , further comprising the step of hydrolysing at least a surface portion of the reactivity modifying agent.
35. The method according to claim 34 , wherein the step of hydrolysing occurs in the presence of a sodium buffer.
36. The method according to claim 34 , wherein the surface portion of the reactivity modifying agent is partially hydrolysed.
37. The method according to claim 33 , further comprising the steps of first at least partially hydrolysing at least a surface portion of the reactivity modifying agent, and subsequently reacting resultant hydrolysed groups with a polyfunctional amine.
38. The method according to claim 37 , wherein the polyfunctional amine reacts to crosslink the resultant hydrolysed groups.
39. A method of preparing a microporous polymeric membrane, comprising acts of:
blending poly(methyl vinyl ether/maleic anhydride) and a polysulfone in an amount such that a combined precursor to the microporous polymeric membrane forms a single phase mixture and thereby obtaining a blended material; and
casting the microporous polymeric membrane from the blended material.
40. A method of preparing a microporous polymeric membrane, comprising acts of:
blending poly(methyl vinyl ether/maleic anhydride) and polyvinylidene fluoride in an amount such that a combined precursor to the microporous polymeric membrane forms a single phase mixture and thereby obtaining a blended material; and
casting the microporous polymeric membrane from the blended material.
41. The method of claim 40 , further comprising an act of preparing a dope solution comprising the blended material and a polyvinylpyrrolidone copolymer.
42. The method of claim 40 , wherein the act of blending comprises an act of adding a solvent comprising N-methylpyrrolidone to the single phase mixture.