Asymmetric membranes for use in nanofiltration

Patent metadata

Field	Value
Publication number	US-10328396-B2
Application number	US-201615342424-A
Country	US
Kind code	B2
Filing date	Nov 3, 2016
Priority date	Jul 19, 2010
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

Improved integrally skinned asymmetric membranes for organic solvent nanofiltration, and their methods of preparation and use are disclosed. Membranes are formed from polybenzimidazoles by phase inversion and are then crosslinked by addition of crosslinking agents. These stabilize the membranes and allow solvent nanofiltration to be maintained even in the solvents from which the membranes were formed by phase inversion, and in strongly acidic and strongly basic solvents.

First claim

The invention claimed is:

1. A membrane suitable for nanofiltration of a feed stream solution comprising N,N-dimethylformamide and dissolved solutes and having a molecular weight cut off of 200-2000 g/mol at ambient temperature, comprising an integrally skinned asymmetric crosslinked polybenzimidazole cast film membrane, wherein the membrane is impregnated with a conditioning agent, and wherein the conditioning agent maintains the pore structure of the membrane prior to its use for nanofiltration.

2. The membrane according to claim 1 , wherein the polybenzimidazole membrane comprises a polybenzimidazole polymer that is poly(2,2′-[m-phenylene])-5,5′-bis-benzimidazole.

3. A membrane according to claim 1 , wherein the membrane comprises crosslinks formed from the reaction of polybenzimidazole with dibromobutane, tribromopropane, trichloropropane, pentaerythrityl tetrabromide, pentaerythrityl tetrachloride, divinyl sulfones, perfluoroglutaric acid, benzene hexacarboxylic acid, benzene pentacarboxylic acid, 1,2,3,4-benzenetetracarboxylic acid, 1,2,3,5-benzenetetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-benzenetricarboxylic acid, dibromosuccinic acid, polyacrylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,6-naphthalenedisulfonic acid, aryl-sulfonic acids, aryl-sulfinic acids, aryl-phosphinic acids, and aryl-phosphonic acids.

4. A method of separating dissolved solutes from a feed stream by nanofiltration, said method comprising the step of passing the feed stream through a polybenzimidazole membrane as claimed in claim 1 .

5. A process for forming the integrally skinned asymmetric crosslinked polybenzimidazole cast film membrane of claim 1 , said process comprising the steps of:
(a) preparing a polybenzimidazole dope solution comprising:
(i) a polybenzimidazole polymer, and (ii) a solvent system for said polybenzimidazole which is water miscible;
(b) casting a film of said dope solution onto a supporting substrate;
(c) allowing the dope solution to evaporate for an evaporation period, and then immersing the film cast on the supporting substrate into a coagulating medium;
(d) treating the resulting asymmetric membrane with a solvent comprising one or more cross-linking agents for polybenzimidazole; and
(e) treating the asymmetric membrane with a conditioning agent, wherein the polybenzimidazole dope solution in step (a) comprises about 14% to about 18% by weight of the polybenzimidazole polymer; and
step (d) is conducted at a temperature of about 50° C. to about 120° C.

6. A process according to claim 5 , further comprising step (f) drying the membrane.

7. A process according to claim 5 , wherein the process further comprises a step of heating the membrane to about 150° C. or higher.

8. A process according to claim 5 , wherein the polybenzimidazole is poly(2,2′-[m-phenylene])-5,5′-bis-benzimidazole.

9. A process according to claim 5 , wherein the polybenzimidazole dope solution further comprises a viscosity enhancer in amounts of up to 10% by weight of said dope solution.

10. A process according to claim 5 , wherein the polybenzimidazole dope solution further comprises a void suppressor used in amounts up to 5% of the weight of said polybenzimidazole dope solution.

11. A process according to claim 5 , wherein the conditioning agent is selected from one or more of synthetic oils, mineral oils, vegetable fats and oils, higher alcohols, glycerols, and glycols.

12. A process according to claim 5 in which the crosslinking agent is chosen from multifunctional alkyl halides, divinyl sulfones, perfluoroglutaric acid, benzene hexacarboxylic acid, benzene pentacarboxylic acid, 1,2,3,4-benzenetetracarboxylic acid, 1,2,3,5-benzenetetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, 1,3,5-benzenetricarboxylic acid, dibromosuccinic acid, polyacrylic acid, 1,4,5,8-naphthalenetetracarboxylic acid, 2,6-naphthalenedisulfonic acid, aryl-sulfonic acids, aryl-sulfinic acids, aryl-phosphinic acids, and aryl-phosphonic acids.

13. A process according to claim 12 , wherein the multifunctional alkyl halide is a di- or tri-functional alkyl halide.

14. A process according to claim 5 , wherein the crosslinking agent is dissolved in a solvent selected from the group consisting of ketones, ethers, carboxylic acids and alcohols.

15. A process according to claim 5 , wherein the quantity of crosslinking agent used to treat the polybenzimidazole membrane is adjusted so that the reactive groups in the crosslinking agent and polybenzimidazole amine hydrogen groups in the membrane treated is in the range between 0.1 to 10.

16. A process according to claim 5 , wherein the polybenzimidazole dope solution comprises one or more solvents chosen from N-methyl-2-pyrrolidone, tetrahydrofuran, N,N-dimethylformamide, dimethylsulfoxide, N,N-dimethylacetamide, 1,4 dioxane and gamma-butyrolactone.

17. A membrane according to claim 1 , wherein the conditioning agent is selected from one or more of synthetic oils, mineral oils, vegetable fats and oils, higher alcohols, glycerols, and glycols.

Assignees

• Ip2Ipo Innovations Ltd

Inventors

• Livingston Andrew Guy
• Bhole Yogesh Suresh

Classifications

• B01D71/62 Primary

  Polycondensates having nitrogen-containing heterocyclic rings in the main chain · CPC title

• B01D61/027

  Nanofiltration · CPC title

• B01D67/0097

  Storing or preservation · CPC title

• B01D2323/30

  Cross-linking · CPC title

• B01D69/02

  characterised by their properties · CPC title