| 摘要 |
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 (AR) of 0.5 to 2.0 meq/g dry polymer in a hydrolyzed form, to give a weight gain percent ( DELTA WR) in the range of DELTA WR=1.6e1.7AR as the upper side; DELTA WR=0.8e1.7AR as the lower side; AR=0.5 as the left side and AR=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 DEG to 60 DEG C. after the hydrolysis or at the time of the hydrolysis.
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