The present invention relates to a sulfonated polymer membrane and to a process
for the preparation thereof. According to the process, a polymer film is irradiated,
and the irradiated polymer film is sulfonated in order to link sulfonic acid groups
thereto. According to the invention, the sulfonation is continued until the total
concentration of sulfonic acid groups in the membrane is 0.4-3.0 meq/g and they
are homogeneously distributed in the membrane material in such a manner that their
concentration in the middle of the membrane is at minimum 0.2 meq/g. With the help
of the invention, it is possible by a rapid and simple process to prepare membranes
the chemical and mechanical properties of which can be regulated by means of the
selection of the initial film, by irradiation and by the sulfonation process.
