Surface cross-linked superabsorbent polymer particles and methods of making them

A method of surface cross-linking superabsorbent polymer particles which comprises the steps of

• a) providing discrete superabsorbent polymer particles selected from the group consisting of granules, flakes, spheres, powders, platelets, and beads, each of the particles comprising a surface and a core, wherein a plurality of aliphatic C—H groups are present at the surface, the particles comprising polymer chain segments;
• b) adding a surface cross-linking composition comprising cross-linking molecules having at least two C═C double bonds and further comprising radical former molecules wherein the radical former molecules when activated are configured to chemically react with the aliphatic C—H groups;
• and
• c) exposing said superabsorbent polymer particles and said surface cross-linking composition to electromagnetic irradiation capable of activating said radical former,
• whereby said cross-linking molecules and said radical former molecules react with at least some of said polymer chain segments comprised at surfaces of the superabsorbent polymer particles to form covalent cross-links between said polymer chain segments, wherein said cross-links comprise the reaction product of said cross-linking molecule, wherein said cross-links further comprise the reaction product of said radical former molecules, and wherein the method does not lead to any appreciable interparticulate bonds between the superabsorbent polymer particles.