US Patent 7270881 Coated water-swellable material

This invention is directed to coated water-swellable materials, typically solid, particulate, water-swellable materials, i.e. materials that comprise hydrogel-forming polymers, whereof at least a part is coated with a coating, which substantially does not break when the polymers swell, as set out in the method herein. Said coating is present at a level of at least 1% by weight of the water-swellable material.