Ion exchange membranes
View Patent ↗Highly energy efficient electrodialysis membranes having low operating costs and a novel process for their manufacture are described herein. The membranes are useful in the desalination of water and purification of waste water. They are effective in desalination of seawater due to their low electrical resistance and high permselectivity. These membranes are made by a novel process which results in membranes significantly thinner than prior art commercial electrodialysis membranes. The membranes are produced by polymerizing one or more monofunctional ionogenic monomers with at least one multifunctional monomer in the pores of a porous substrate.
1. An ion exchange membrane, comprising:
a microporous membrane support having a porous first side and a porous second side and a continuous porous structure extending from said first side to said second side; and
a crosslinked ion transferring polymer filling said continuous porous structure, said polymer formed in the continuous porous structure and comprising the polymerization product of one or more ionogenic monomers, a neutral monomer, and a multifunctional crosslinking monomer, wherein the continuous porous structure comprises pores having a size of about 0.05 microns to about 10 microns.
2. The ion exchange membrane of claim 1 wherein the thickness of the porous support is greater than about approximately 55 microns and less than about approximately 155 microns.
3. The ion exchange membrane of claim 1 wherein the thickness of the porous support is greater than about approximately 20 microns and less than about approximately 55 microns.
4. The ion exchange membrane of claim 1 wherein the microporous support comprises polypropylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene or polyvinylidene fluoride.
5. The ion exchange membrane of claim 1 wherein the ion transfer polymer is a cation transfer polymer.
6. The ion exchange membrane of claim 5 wherein the crosslinked ion transferring polymer is formed by polymerization of 2-sulfoethylmethacrylate (2-sem or 2-acrylamide-2-methyl propane sulfonic acid (AMPS) and a crosslinking monomer to form a cation exchange membrane.
7. The ion exchange membrane of claim 6 wherein the crosslinker is ethyleneglycoldimethacrylate.
8. The ion exchange membrane of claim 5 wherein the crosslinked ion transferring polymer is formed by polymerization of 2-sulfoethylmethacrylate (2-sem, 2-acrylamide-2-methyl propane sulfonic acid (AMPS), a neutral monomer, and a crosslinking monomer to form a cation exchange membrane.
9. The ion exchange membrane of claim 8 wherein the neutral monomer is hydroxyethylacrylate or hydroxymethacrylate.
10. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 0.5 ohm-cm 2 .
11. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 0.5 ohm-cm 2 and a permselectivity of greater than about approximately 95%.
12. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 0.5 ohm-cm 2 and a permselectivity of greater than about approximately 99%.
13. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 1.0 ohm-cm 2 .
14. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 1.0 ohm-cm 2 and a permselectivity of greater than about approximately 95%.
15. The ion exchange membrane of claim 5 wherein the membrane has a resistivity not greater than about approximately 0.5 ohm-cm 2 and a permselectivity of greater than about approximately 99%.
16. The ion exchange membrane of claim 1 wherein the continuous porous structure comprises pores having a size of about 0.1 microns to about 1.0 microns.
17. The ion exchange membrane of claim 1 wherein the microporous membrane support has a porosity of greater than about 45%.
18. The ion exchange membrane of claim 1 wherein the microporous membrane support has a porosity of greater than about 60%.