Process for making water-swellable material comprising coated water-swellable polymers

A process for making a water-swellable material, comprising coated superabsorbent polymer particles and a flow aid, the process comprising the steps of:

• a) obtaining superabsorbent polymer particles, wherein the superabsorbent polymer is selected from the group consisting of polymers formed from monomers of acrylic acid, methacrylic acid, α-chloroacrylic acid, a-cyanoacrylic acid, β-methylacrylic acid (crotonic acid), α-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid, α-chlorosorbic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-stearylacrylic acid, itaconic acid, citroconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene, maleic anhydride, and combinations thereof;
• and
• b) applying a coating agent to at least part of the superabsorbent polymer particles, said coating agent being applied in an amount of at least 1% by weight of the water-swellable material, wherein said coating agent comprises a polyurethane, is wet- extensible, and has a tensile stress at break in the wet state of at least 1 Mpa;
• c) adding a flow aid and heat treating the resulting coated water-swellable polymers of step b) to obtain the water-swellable material comprising coated superabsorbent polymer particles.