Inert separator beads for separating cation exchange resins from anion exchange resins during regeneration of mixed-bed ion exchange resins are copolymers of 60 to 90 weight percent methyl methacrylate, 5 to 15 weight percent styrene and 2 to 10 weight percent hydrophilic monomer containing amide functionality, and 1 to 6 weight percent crosslinkiner. They may be made by suspension polymerisation or expanded seed polymerisation processes.
