PURPOSE: To facilitate direct functionalization by preparing a liquid cation exchange material with an emulsion of beads of a crosslinked copolymer having a spherical shape of 0.1 to 1.5 μ in diameter and having a cation exchange functional group of a specific group. CONSTITUTION: The crosslinked acrylate copolymer beads are formed by emulsion polymn. of the majority ratio of an acrylate monomer and a small ratio of an ethylenically unsatd. monomer. The ester bond of the beads is hydrolyzed by a strong acid to form the carboxylic acid cation exchange functional group of a free acid type and similarly to form the coagulum of the functionalized copolymer beads and thereafter, the coagulum is resuspended, by which the emulsion of the copolymer beads is prepd. The functionalized copolymer beads have the spherical shape having a diameter of 0.01 to 1.5 μm and have the cation exchange functional group in the free acid form of the weakly acidic functional group of 0.7 to 1.5 per monomer unit.
