Asahi Glass Company, Limited

Shoziro Goto

Manabu Suhara

Yoshio Oda

Kiyotaka Arai

Toshikatsu Hamano

Koji Miura

Takashi Hukushima

A cation exchange membrane of a fluorinated polymer used for an electrolysis of an alkali metal chloride is obtained by treating a cation exchange membrane having ion exchange groups of --COOM (M is hydrogen atom or an alkali metal atom) or groups being convertible to said groups and having an ion exchange capacity (A.sub.R) of 0.5 to 2.0 meq/g dry polymer in a hydrolyzed form, to give a weight gain percent (.DELTA.W.sub.R) in the range of .DELTA.W.sub.R =1.6e.sup.1.7A R as the upper side; .DELTA.W.sub.R =0.8e.sup.1.7A R as the lower side; A.sub.R =0.5 as the left side and A.sub.R =2.0 as the right side shown in FIG. 1 (log scale on ordinate) in an aqueous medium of a base or a salt at a concentration of 1 to 20 wt. % at the temperature of 0.degree. to 60.degree. C. after the hydrolysis or at the time of the hydrolysis.

Cation exchange membrane of fluorinated polymer for electrolysis and

An electrolysis of an aqueous solution of sodium chloride is carried out by employing a fluorinated cation exchange membrane having an ion-exchange capacity of 0.8 to 2.0 meq/g dry polymer and having carboxylic acid groups as functional groups and maintaining a concentration of an aqueous solution of sodium hydroxide in a cathode compartment in a range of 20 to 45 wt. % and maintaining a calcium concentration in the aqueous solution of sodium chloride to lower than 0.08 mg/liter. The purification of the aqueous solution of sodium chloride to reduce the calcium concentration is carried out in a system comprising the first and second chelate ion-exchange towers which are connected through a detector for detecting impurities in the aqueous solution.

Electrolysis of aqueous solution of sodium chloride

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Yokohama, Japan

Shoziro Goto