Compositions of highly absorbent composite material, absorbent sheets provided with the compositions and process for the production thereof

A highly absorbent composite material comprising thin, hydrofibrile-shaped fine fibers that are obtained from cellulose or a derivative thereof, and swellable solid particles in water, at least part of the surface of each of the swellable solid particles in water covered with certain hydratable fine fibers in the form of microfibrils, or said solid particles swellable in water bonded together by said fine hydratable fibers in the form of microfibrils.