Resins

In the process of preparing hard, crosslinked discrete ion exchange copolymer beads by the thermally induced free-radical polymerization in an aqueous dispersion of a monomer mixture comprised of a major proportion of a monovinyl aromatic monomer and a minor proportion of a crosslinking monomer having at least two active vinyl groups, the improvement which comprises conducting the polymerization reaction in the presence of a peroxy catalyst of the formula:

• ##STR5## wherein R.sub.1 is a branched alkyl of 3 to 12 carbon atoms and having a secondary or tertiary carbon linked to the carbonyl group and X is a positive integer having a value of either 1 or 2 and when X is 1, R.sub.2 is a branched alkyl radical containing a tertiary carbon attached to the oxygen, and when X is 2, R.sub.2 is an alkylene or aralkylene, in either case terminating in tertiary carbons attached to the oxygen, or of the formula:
• ##STR6## wherein Y and Z are independently selected from lower alkyl, cycloalkyl, alkyl-substituted cycloalkyl and aralkyl, and thereafter functionalizing the copolymer bead to form ion exchange sites therein.