In a process for producing ion exchange resin capable of hydraulic segregation into discrete zones of resin having different ion exchange functionalities, the resins are produced by differently functionalizing fractions of a single batch or lot of precursor copolymer which have been classified on the basis of differing hydraulic densities of the different sized particles. Ion exchange processes comprise contacting a fluid containing exchangeable ions with resin produced by this process and deionisation by this technique is of particular interest.
