| abstract |
PURPOSE:To obtain a water-absorbing resin compsn. which can be directly sliced, has excellent water absorption properties and is useful as a water- absorbing and water-retentive material by polymerizing an aq. mixture of a partially neutralized acrylic acid wherein fine precipitates of sodium acrylate are dispersed with a polymn. initiator without stirring. CONSTITUTION:An aq. mixture wherein an acrylic acid, 60-90mol% of the COOH groups of which are neutralized into sodium salt group and a polymn. initiator are incorporated, wherein the concn. of acrylic acid is in the range of 45-60wt.% and wherein fine precipitates of sodium acrylate are dispersed, is cast on a flat plate and heated without stirring to initiate polymn. The polymn. rapidly proceeds accompanied with heat generation and the viscosity rapidly rises. Smooth foaming and water evaporation are observed and the precipitate is dissolved and converted to a polymer. By polymerizing a dense mixture exceeding a satd. concn., a polymer having a low water content and no self- adhesiveness is obtd. and is directly sliced to give a sheet, a cubic pellet, etc. A water-absorbing resin having an excellent water-absorption property is obtd. thereby. |