Weak acid ion exchange membranes

Weak acid ion exchange membranes were prepared by pressing methyl acrylate/methyl methacrylate and methyl acrylate/butyl methacrylate copolymers into the film form. Before shaping, the copolymers were hydrolysed in an alkaline solution (heterogeneous system). The following optimal hydrolysis parameters were established: temperature: 90°C; hydrolyzing agent potassium hydroxide/methylacrylate ratio: 5 mol/mol; concentrations: copolymer: 5 wt.‐%, emulsifier (Hostapal CV): 0.5 wt.‐%. Products insoluble in water or alkaline solutions, yet containing enough carboxylic groups to provide an ion exchange selectivity, were obtained by hydrolysis of copolymers containing less than 30 wt.‐% of methyl acrylate units. The ion exchange and transport properties (in the system 0.5 M NaOH//membrane//H2O) were found to be the best for the membranes obtained from hydrolysed poly(methyl acrylate‐co‐methyl methacrylate).