Bipolar membranes and method of making same
First Claim
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1. A method for preparing bipolar membranes which comprises:
- coating on (a) an ion exchange membrane, a fluid mixture of a dispersion of (b) particles of an ion exchange resin in (c) a matrix polymer where (b) has a charge opposite to the charge of (a); and
bonding said membrane and mixture to form a unitary bipolar membrane structure.
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Abstract
Stable bipolar membranes of high permselectivity and low potential drop are prepared using either an anion or cation preformed first layer upon which a second layer or coating of an ion exchange resin of the opposite charge carried in a matrix polymer is applied. The second layer may be suitably applied such as by casting as a slurry of the ion exchange resin in a solution or by laminating a layer comprising a dispersion of the resin in a solid or fused polymer. Optionally, the surface of the first layer may be treated to increase the resin concentration and/or bonding at the interface, such as by sanding, etching, etc.
116 Citations
17 Claims
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1. A method for preparing bipolar membranes which comprises:
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coating on (a) an ion exchange membrane, a fluid mixture of a dispersion of (b) particles of an ion exchange resin in (c) a matrix polymer where (b) has a charge opposite to the charge of (a); and bonding said membrane and mixture to form a unitary bipolar membrane structure. - View Dependent Claims (2, 3, 4, 15)
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- 5. A method for preparing bipolar membranes which comprises coating on a membrane which is comprised of an inert polymeric matrix and an anion exchange crosslinked polyelectrolyte, a dispersion of cation exchange resin particles having a particle size of less than one micron diameter in a solution of a matrix polymer, and evaporating the solvent from the cation exchange resin solution to form a unitary bipolar membrane structure.
- 10. A method for preparing bipolar membranes which comprises mixing a solution of polyvinylidene fluoride with a solution of polyvinylbenzyl chloride, generating quaternary ammonium groups by introducing into said mixture a multifunctional amine, casting the mixture as a film and evaporating the solvent to give an anion membrane, abrading the surface of said membrane, coating said abraded membrane with a dry cation exchange resin, and then with a suspension of cation exchange resin in a solution of polyvinylidene fluoride and evaporating the solvent to provide a unitary bipolar membrane structure.
- 11. A method for preparing bipolar membranes which comprises casting a solution of a copolymer which forms quaternary ammonium groups when reacted with a multifunctional amine and an amine or mixture of amines which is capable of forming quaternary ammonium groups by reaction with said copolymer, evaporating the solvent to give an anionic membrane, depositing on said membrane a dispersion of cation exchange resin in a solution of a matrix polymer and evaporating the solvent from the cationic resin solution to provide a unitary bipolar membrane structure.
Specification