| 摘要 |
PURPOSE:To obtain easily a polymer having a large particle diameter by freezing a water-cotg. water-absorbing resin and then performing a freeze vacuum drying treatment thereof. CONSTITUTION:After a water-contg. water-absorbing resin is frozen at -10 deg.C or below, a freeze vacuum drying treatment thereof is performed under a pressure condition of 10Torr or below. As the applied water-absorbing resins, crosslinked polymers of salts of (meth)acrylic acid, saponified products of crosslinked (meth)acrylate-vinyl acetate copolymers, crosslinked starch-salt of acrylic graft copolymers, crosslinked maleic acid anhydride-grafted polyvinyl alcohol, etc., can be cited. When the temp. of the freezing operation is higher than -10 deg.C, too long a time is required for freezing and it is therefore not economical for an industrial operation. When the pressure condition is higher than 10Torr, too long a time is required for drying and it is therefore not economical for an industrial operation. |
