| 摘要 |
The present invention provides a fluorinated cation exchange membrane comprising at least two layers, a first layer made of a fluoropolymer having sulfonic acid groups and a second layer made of a fluoropolymer having carboxylic acid groups on the cathode side thereof, wherein when an electrolytic soda process is conducted using the cation exchange membrane as a diaphragm between an anode compartment and a cathode compartment, the water transport number through the cation exchange membrane is at least 4.8 mol/F (F: Faraday) under operating conditions such that the brine concentration in the anode compartment is 200 g/L, the sodium hydroxide concentration in the cathode compartment is 32 mass %, the current density is 5 kA/m<SUP>2</SUP>, and the temperature is 90° C. The fluorinated cation exchange membrane of the present invention gives an excellent effect such that a uniform catholyte concentration can be maintained even when installed in an electrolytic cell having no special circulating means.
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