| 摘要 |
PURPOSE:To obtain a resin, having excellent water absorbing property and providing a gel extremely stable even when exposed to light, by carrying out a water-in-oil type reversed phase suspension polymerization method in the presence of a benzophenone based ultraviolet ray absorber in polymerizing an acrylic acid monomer. CONSTITUTION:An acrylic acid monomer consisting essentially of (meth)acrylic acid and alkali metal or ammonium salts thereof is polymerized by using a water-soluble radical initiator, e.g. hydrogen peroxide, tert-butyl hydroperoxide, etc., in an amount of normally 0.1-2wt.% based on the acrylic monomer. In the process, polymerization is carried out in the presence of a benzophenone based ultraviolet ray absorber, e.g. 2,4-dihydroxybenzophenone, etc., by a water- in-oil type reversed phase suspension polymerizaion method to afford the aimed resin. The above-mentioned resin absorbs a large amount of water to swell, but is insoluble in water.
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