| abstract |
Provided are a manufacturing method of water absorbing resin particle agglomerates capable of producing water absorbing resin particles having a sufficiently high water retention property and a large particle size without using a special material, which process has steps of (1) a polymerization step for producing primary particles of a water absorbing resin comprising suspending an aqueous monomer solution containing an unsaturated carboxylate in an organic solvent containing a nonionic surfactant therein, and subjecting the resulting suspension to reverse-phase suspension polymerization, and (2) an agglomeration step of agglomerating the primary particles by using a water soluble solvent; and water absorbing resin particle agglomerates stably showing a high water retention property and satisfying the following requirements: (a) 50 mol % or greater of repeating units of the polymer molecular chain of the water absorbing resin constituting the primary particles are carboxyl group-containing units and at least a portion of carboxyl groups of the carboxyl group-containing units is neutralized with at least one base selected from alkali metals, amines, and ammonia, and (b) the water absorbing resin particle agglomerates comprise, on the outer surface thereof, a portion having a neutralization ratio of carboxyl groups of not greater than 40 mol % and, inside of the water absorbing resin particle agglomerates, a portion having a neutralization ratio of carboxyl groups of 50 mol % or greater. |