Superabsorbent polymers having radiation activatable surface cross-linkers and method of making them

Superabsorbent polymer particles comprising a water-absorbing resin and the reaction product of a radiation activatable surface cross-linker wherein the reaction product of the radiation activatable surface cross-linker is present at surfaces of the superabsorbent polymer particles, wherein said radiation activatable surface cross-linker comprises at least two radiation activatable groups R1 and R2, said at least two radiation activatable groups R being covalently bound to each other or to at least one spacer group S, wherein the spacer group S is a spacer group selected from the group consisting of an organic group with a molecular weight of up to about Mw=10,000, and a polymeric group with a molecular weight of up to about Mw=1,000,000, and wherein said radiation activatable groups R1 and R2 are the same or different and are selected from the group consisting of:

• a) acetophenone, benzophenone, anthraquinone, xanthone, thioxanthone, camphorquinone, terephthalophenone benzil, fluorenone, -ketocoumarin and acetophenone-, benzophenone-, anthraquinone-, xanthone-, thioxanthone-, camphorquinone-, terephthaiophenone-, benzil-, fluorenone-, and -ketocoumarin-derivatives, wherein acetophenone derivatives or benzophenone derivatives also comprise reaction products, such as condensation products of acetophenone derivatives or benzophenone derivatives, comprising at least two acetophenone or benzophenone groups, or
• b) a group comprising a first group selected from the group consisting of methyl, benzyl, aryl, preferably phenyl and substituted phenyl, and a second group selected from the group consisting of an aryl, an alkyl of 1 to 4 carbon atoms, cyclopropyl, cyclopentyl, cyclohexyl, α,α-dialkoxyalkyl, and α-hydroxyalkyl and wherein said first group is covalently bound to said second group via an additional carbonyl group, and wherein the second group is covalently bound to the spacer group S or to another radiation activatable group.