<；P>；PROBLEM TO BE SOLVED: To provide water absorbing resin particles which absorb water and can easily release water after a definite period of time. <；P>；SOLUTION: The water absorbing resin particles comprise as essential monomers a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and ketimine obtained from vinyl ketone and polyamine. It is preferable that the content of ketimine (b) unit should be 0.0005-3 mol% based on the number of moles of water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit. It is preferable that vinyl ketone should be isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl isopropyl ketone, isopropenyl isobutyl ketone, or isopropenyl t-butyl ketone. It is preferable that polyamine should be aliphatic diamine or aliphatic triamine. <；P>；COPYRIGHT: (C)2009,JPO&INPIT
