# US 10,370,511 B2 · Cation exchange membrane and method for producing potassium hydroxide aqueous solution > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,370,511 B2 - Document ID: US10370511B2 - Status: Granted - Kind: B2 - Application number: 15/291,121 - Filed: 2016-10-12 - Published: 2017-02-02 - Granted: 2019-08-06 - Earliest claimed: 2014-04-21 - Assignees: AGC Inc. - Applicants: AGC Inc. - Inventors: Hiromitsu Kusano; Takayuki Kaneko; Yasushi Yamaki; Takayuki Endo - Web page: https://patentgrep.com/patent/US10370511B2 ## CPC - C08J 5/225: {containing fluorine} - B01J 39/04: Processes using organic exchangers - B01J 39/20: obtained by reactions only involving unsaturated carbon-to-carbon bonds - B01J 47/12: characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes (electrodialysis or electro-osmosis B01D61/42) - C01D 1/04: Hydroxides - C08F 8/44: Preparation of metal salts or ammonium salts - C08F 214/262: {with fluorinated vinyl ethers} - C25B 1/16: Hydroxides (by simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine C25B1/34) - C25B 9/19: with diaphragms - C25B 9/75: having bipolar electrodes - C25B 13/08: based on organic materials - C08J 2327/12: containing fluorine atoms - C08J 2327/14: Homopolymers or copolymers of vinyl fluoride - C08J 2329/10: Homopolymers or copolymers of unsaturated ethers (C08J2335/08 takes precedence) - C25B 9/77: having diaphragms - C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29) - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - C01D: COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides C01B17/22; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia and cyanogen, containing nitrogen and other non-metals C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; phosphides C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20) - C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS - C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B) ## Abstract To provide a cation exchange membrane which is less susceptible to swelling or elongation during electrolysis of a potassium chloride aqueous solution even without permitting water absorption or swelling immediately prior to mounting it in an electrolyzer, and a method whereby it possible to stably produce a potassium hydroxide aqueous solution without necessity to conduct an operation for water absorption or swelling immediately prior to mounting the membrane in the electrolyzer. A cation exchange membrane comprising a polymer having cation exchange groups, wherein in cations (100 mol %) contained in the cation exchange membrane, the total of potassium ions and sodium ions is at least 99 mol %, and in the total (100 mol %) of potassium ions and sodium ions contained in the cation exchange membrane, the potassium ions are 80-98 mol % and the sodium ions are 20-2 mol %. ## Claims ### Claim 1 A cation exchange membrane comprising at least one polymer having cation exchange groups, wherein in cations (100 mol %) contained in the cation exchange membrane, the total of potassium ions and sodium ions is at least 99 mol %, and in the total (100 mol %) of potassium ions and sodium ions contained in the cation exchange membrane, potassium ions are from 80 to 98 mol %, and sodium ions are from 20 to 2 mol %. ### Claim 2 (depends on 1) The cation exchange membrane according to claim 1, wherein the at least one polymer having cation exchange groups is either one or both of a perfluorocarbon polymer having alkali metal salt form carboxylic acid groups and a perfluorocarbon polymer having alkali metal salt form sulfonic acid groups. ### Claim 3 (depends on 2) The cation exchange membrane according to claim 2, which comprises a layer comprising the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups, and a layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups. ### Claim 4 (depends on 3) The cation exchange membrane according to claim 3, wherein the ion exchange capacity of the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups is from 0.7 to 1.1 meq/g dry resin, and the ion-exchange capacity of the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups is from 0.9 to 1.15 meq/g dry resin. ### Claim 5 (depends on 4) The cation exchange membrane according to claim 4, wherein the layer comprising the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups and the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups, are in contact with each other, and the difference in ion exchange capacity between the layer comprising the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups and the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid group, adjacent to each other, is from 0.1 to 0.45 meq/g dry resin. ### Claim 6 (depends on 3) The cation exchange membrane according to claim 3, wherein the thickness of the layer comprising the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups is from 5 to 50 μm, and the thickness of the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups is from 55 to 200 μm. ### Claim 7 (depends on 3) The cation exchange membrane according to claim 3, wherein a reinforcing material is embedded in the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups, and the ion exchange capacity of the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups on an anode side of the reinforcing material, is higher than the ion exchange capacity of the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups on a cathode side of the reinforcing material. ### Claim 8 (depends on 7) The cation exchange membrane according to claim 7, wherein the thickness of the layer comprising the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups on the anode side of the reinforcing material is from 10 to 60 μm. ### Claim 9 (depends on 1) The cation exchange membrane according to claim 1, which comprises a gas release layer on at least either one of an anode side surface and a cathode side surface. ### Claim 10 (depends on 2) The cation exchange membrane according to claim 2, wherein the perfluorocarbon polymer having alkali metal salt form carboxylic acid groups is one obtained by hydrolysis treatment of a copolymer having structural units derived from a monomer represented by formula (1), and structural units derived from a monomer represented by formula (2), and the perfluorocarbon polymer having alkali metal salt form sulfonic acid groups is one obtained by hydrolysis treatment of a copolymer having structural units derived from a monomer represented by formula (1), and structural units derived from a monomer represented by formula (3): CF2═CX1X2 (1) CF2═CF(OCF2CFX3)nO(CF2)mY (2) CF2═CF(OCF2CFX4)sO(CF2)tW (3) wherein X1 and X2 are each independently a fluorine atom, a chlorine atom or a trifluoromethyl group, X3 is a fluorine atom or a trifluoromethyl group, m is an integer of from 1 to 5, n is 0 or 1, Y is a precursor group which can be converted to a carboxylic acid group by hydrolysis, X4 is a fluorine atom or a trifluoromethyl group, s is an integer of from 1 to 3, t is an integer of from 0 to 2, and W is a precursor group which can be converted to a sulfonic acid group by hydrolysis. ### Claim 11 (depends on 7) The cation exchange membrane according to claim 7, wherein the material of the reinforcing material is polytetrafluoroethylene. ### Claim 12 (depends on 9) The cation exchange membrane according to claim 9, wherein the gas release layer is a layer comprising inorganic particles and a binder. ### Claim 13 (depends on 12) The cation exchange membrane according to claim 12, wherein the inorganic particles are SiO2, SiC, ZrO2 or ZrC, and the binder is methyl cellulose, or a fluoropolymer having carboxylic acid groups or sulfonic acid groups. ### Claim 14 (depends on 1) A method for producing a potassium hydroxide aqueous solution, the method comprising contacting a potassium chloride aqueous solution with the cation exchange membrane as defined in claim 1 to electrolyze the potassium chloride aqueous solution by an ion-exchange membrane method. ### Claim 15 (depends on 14) The method according to claim 14, wherein the concentration of potassium chloride in the potassium chloride aqueous solution is from 150 to 200 g/L, and the concentration of potassium hydroxide in the potassium hydroxide aqueous solution is from 20 to 40 mass %.