Anion exchange membranes and process for making
View Patent ↗Embodiments of the present invention provide for anion exchange membranes and processes for their manufacture. The anion exchange membranes described herein are made the polymerization product of at least one functional monomer comprising a tertiary amine which is reacted with a quaternizing agent in the polymerization process.
1. A process of producing an ion exchange membrane, comprising:
saturating porous regions of a porous substrate having a porosity of at least about 45% with a first solution comprising vinylbenzyl chloride, benzyl chloride, and a tertiary amine monomer selected from the group consisting of vinylimidazole and vinylcarbazole, the porous substrate having a thickness of greater than about 20 microns and less than about 55 microns; and
heating the saturated porous substrate to forma crosslinked ion exchange polymer in the porous regions; and
conditioning the porous substrate having the crosslinked ion exchange polymer in a second solution comprising sodium chloride for at least thirty minutes.
2. The process of claim 1 , wherein the first solution further comprises at least one polymerization initiator selected from the group consisting of organic peroxides, 2,2′-azobis[2,(2-imidazolin-2-yl)-propane] dihydrochloride, a,a′-azoisobutyronitrile, 2,2′-azobis(2-methylpropioaminidine) dihydrochloride, 2,2′-azobis[2,(2-imidazolin-2-yl)-propane], and dimethyl 2,2′-azobis(2-methylpropionate).
3. The process of claim 2 , wherein the first solution further comprises at least one polymerization inhibitor selected from the group consisting of 4-methoxyphenol and 4-tert-butyl catechol.
4. The process of claim 1 , wherein the porous substrate is comprised of polypropylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene or polyvinylidene fluoride.
5. The process of claim 1 , wherein the first solution further comprises a solvent selected from the group consisting of butanol, propanol, dipropylene glycol, dimethylacetamide, and N methylpyrrolidone.
6. The process of claim 1 , wherein heating the porous substrate having porous regions saturated with the first solution comprises heating the porous substrate in the absence of oxygen.