| 摘要 |
PURPOSE:To provide the titled catalyst capable of giving photochromic hydrophilic (meth)acrylic acid derivative polymer free from becoming opaque and from yellowing, made up of polytungstic acid and/or heterotungstic acid, etc. CONSTITUTION:The objective photopolymerization catalyst made up of compound(s) selected from polytungstic acid (e.g., decatungstic acid), heterotungstic acid (e.g., heterosilicotungstic acid) and derivatives therefrom [e.g., tetrakis (tetrabutyl ammonium) decatungstic acid]. The amount of this catalyst to be used is such as to be pref. 0.1-10wt.% based on a hydrophilic (meth)acrylic acid derivative monomer [e.g., 2-hydroxymethyl (meth)acrylate].
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