Sodium chloride soln. electrolysis using cation exchange membrane - of fluorinated polymer with carboxyl gps. and limited water permeability

摘要

In the electrolysis of aq. NaCl soln. to NaOH and chlorine using a fluorinated cation exchange membrane of a fluorinated polymer with COOH gps. as ion exchange gps., this membrane has a water permeability of 2.0-3.5 mole/faraday (F) in electrolysis. It pref. has an ion exchange capacity of 0.5-4.0 milli equiv./g dry polymer and a Tg >20 degrees C below the electrolysis temp. A high current efficiency is obtd. In an example, using a membrane obtd. by hydrolysis of a copolymer of C2F4 and CF2=CHO(CH2)3COOMe with a permeability of 2.5 mole/F, the current efficiency for NaOH was 94.8%, cf only 62.4% for a similar membrane with a permeability of 6.23 mole/F.