| 摘要 |
The ion exchange resin beads have functional groups of formula I wherein R1, R2, R3, R4, m, r and q have the meanings stated in Claim 1 and which have a matrix of a cross-linked polymer wherein the level of cross-linkages is decreased in the shell area as compared to the core area. These ion exchange resin beads are prepared by reacting resin beads which have primary or secondary amino groups and the mentioned matrix of a cross-linked polymer with a1) a hypophosphite salt in the presence of an acid, or a2) a hypophosphorous acid and b) formaldehyde or a formaldehyde releasing compound.
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