Method of making single film, high performance bipolar membrane
First Claim
1. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polymeric matrix film derived from monomers selected from the group consisting of ##STR6## wherein R1 to R7 are substituents selected from the group consisting of hydrogen, chlorine, fluorine, alkyl radicals of 1 to 5 carbon atoms and phenyl radicals and copolymers thereof, and chlorinated and fluorinated polymers and copolymers thereof;
- uniformly with an aromatic nuclei containing monomer selected from those having the formula ##STR7## wherein R8, R9 and R10 are substituents from the group consisting of hydrogen, alkyl radicals of 1 to 4 carbon atoms, phenyl substituted alkyl radicals of 2-4 carbon atoms, phenyl, phenoxy-, thiophenoxy, and naphthyl radicals and the hydroxyl, alkoxyl, and halo substituted phenyl, phenoxy, thiophenoxy, and naphthyl radicals and wherein at least one substituent is an aromatic radical, and polymerizing and cross-linking said impregnated film to an extent equivalent to that obtained by cross-linking a 2 to 20 percent mixture of a 55 percent divinyl benzene in styrene, to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked aromatic nuclei containing polymer within the film;
removing essentially all excess aromatic polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a solvent system supplying cationic functional groups for a period of time sufficient to render the aromatic nuclei readily accessible thereto thereafter chemically bonding highly dissociable cation exchange groups to the aromatic nuclei from one side of said film to a depth of not more than about 98% of the films thickness and thereafter chemically bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both the anionic and cationic functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin.
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Accused Products
Abstract
Novel single film bipolar membranes, of substantially improved efficiency and durability, i.e. having an ion selectivity above 80% in an electrolyte medium of about one mole, are prepared from pre-swollen films containing a relatively high amount, i.e. at least 15% of an insoluble cross-linked aromatic polymer. Under controlled conditions, highly dissociable cationic-exchange groups are chemically bonded to the aromatic nuclei to a desired depth of the film from one side only; subsequently, highly dissociable anion-exchange groups are chemically bonded to the unreacted aromatic nuclei on the other side of the film. The functionalized, densely structured single film ion exchange membrane undergoes negligible degradation, is blister free, and is uniquely suited for electrodialysis particularly water-splitting operations due to its low electrical resistance and low salt leakage. The membrane operates with improved current efficiencies at both high electrolyte concentrations and high current densities, for time periods not previously achievable.
20 Citations
23 Claims
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1. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polymeric matrix film derived from monomers selected from the group consisting of ##STR6## wherein R1 to R7 are substituents selected from the group consisting of hydrogen, chlorine, fluorine, alkyl radicals of 1 to 5 carbon atoms and phenyl radicals and copolymers thereof, and chlorinated and fluorinated polymers and copolymers thereof;
- uniformly with an aromatic nuclei containing monomer selected from those having the formula ##STR7## wherein R8, R9 and R10 are substituents from the group consisting of hydrogen, alkyl radicals of 1 to 4 carbon atoms, phenyl substituted alkyl radicals of 2-4 carbon atoms, phenyl, phenoxy-, thiophenoxy, and naphthyl radicals and the hydroxyl, alkoxyl, and halo substituted phenyl, phenoxy, thiophenoxy, and naphthyl radicals and wherein at least one substituent is an aromatic radical, and polymerizing and cross-linking said impregnated film to an extent equivalent to that obtained by cross-linking a 2 to 20 percent mixture of a 55 percent divinyl benzene in styrene, to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked aromatic nuclei containing polymer within the film;
removing essentially all excess aromatic polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a solvent system supplying cationic functional groups for a period of time sufficient to render the aromatic nuclei readily accessible thereto thereafter chemically bonding highly dissociable cation exchange groups to the aromatic nuclei from one side of said film to a depth of not more than about 98% of the films thickness and thereafter chemically bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both the anionic and cationic functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
- uniformly with an aromatic nuclei containing monomer selected from those having the formula ##STR7## wherein R8, R9 and R10 are substituents from the group consisting of hydrogen, alkyl radicals of 1 to 4 carbon atoms, phenyl substituted alkyl radicals of 2-4 carbon atoms, phenyl, phenoxy-, thiophenoxy, and naphthyl radicals and the hydroxyl, alkoxyl, and halo substituted phenyl, phenoxy, thiophenoxy, and naphthyl radicals and wherein at least one substituent is an aromatic radical, and polymerizing and cross-linking said impregnated film to an extent equivalent to that obtained by cross-linking a 2 to 20 percent mixture of a 55 percent divinyl benzene in styrene, to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked aromatic nuclei containing polymer within the film;
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20. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polyethylene film uniformly with a mixture of styrene monomer and a di- or poly-functional cross-linking agent, subsequently polymerizing said impregnated mixture to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked polystyrene within the film;
- removng essentially all excess polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a cationic functional group sulfonation reagent, for a period of time sufficient to render the aromatic nuclei of the polystyrene readily accessible to the sulfonating reagent, thereafter chemically bonding highly dissociable sulfonic groups to the aromatic nuclei from one side of said film to a depth of from about 50% to about 98% of the films thickness and thereafter chemically bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin.
- removng essentially all excess polymerizate from the surface of said film;
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21. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polypropylene film uniformly with a mixture of styrene monomer and a di- or poly-functional cross-linking agent, subsequently polymerizing said impregnated mixture to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked polystyrene within the film;
- removing essentially all excess polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a cationic functional group sulfonation reagent, for a period of time sufficient to render the aromatic nuclei of the polystyrene readily accessible to the sulfonating reagent, thereafter chemically bonding highly dissociable sulfonic groups to the aromatic nuclei from one side of said film to a depth of from about 50% to about 98% of the films thickness and thereafter chemically bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin.
- removing essentially all excess polymerizate from the surface of said film;
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22. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polytrifluoro chloroethylene film uniformly with a mixture of styrene monomer and a di- or poly-functional cross-linking agent, subsequently polymerizing said impregnated mixture to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked polystyrene within the film;
- removing essentially all excess polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a cationic functional group sulfonation reagent, for a period of time sufficient to render the aromatic nuclei of the polystyrene readily accessible to the sulfonating reagent, thereafter chemically bonding highly dissociable sulfonic groups to the aromatic nuclei from one side of said film to a depth of from about 50% to about 98% of the films thickness and thereafter chemically bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin.
- removing essentially all excess polymerizate from the surface of said film;
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23. A process for the manufacture of a durable, high performance, single film bipolar membrane comprising impregnating a polyethylene-polypropylene copolymer film uniformly with a mixture of styrene monomer and a di- or poly-functional cross-linking agent, subsequently polymerizing said impregnated mixture to obtain at least 15 percent by weight based on the total weight of the film, of the cross-linked polystyrene within the film;
- removing essentially all excess polymerizate from the surface of said film;
preswelling without substantially dissolving said cross-linked film in a solvent substantially inert to but miscible with a cationic functional group sulfonation reagent, for a period of time sufficient to render the aromatic nuclei of the polystyrene readily accessible to the sulfonating reagent, thereafter chemically bonding highly dissociable sulfonic groups to the aromatic nuclei from one side of said film to a depth of from about 50% to about 98% of the films thickness and thereafter chemically-bonding highly dissociable anionic exchange groups to the remaining aromatic nuclei on the opposite side of said film, and wherein the concentration of both functional groups is at least substantially equal and greater than 1.4 meg/g. of dry resin.
- removing essentially all excess polymerizate from the surface of said film;
Specification