木材 - MMA蒸気相系の放射線重合 : 膨潤剤としてのメタノールの効果

Abstract

メタクリル酸メチルとメタノールの混合蒸気相下に木材を放置し, γ線を照射して, 蒸気相重合させた。蒸気相重合は液相法と異なり, 温度効果が顕著であった。また収着させたのち, 蒸気を送らない状態で照射し重合させると, 収着モノマーの40％が重合し, 残りの60％はモノマーのままで存在する。このことは木材の微細な空隙ではメタノール濃度が高く, モノマーが重合しえない状態にあることによると推定された。また重合過程での単位時間当りの収着モノマー量は付加ポリマーのそれよりも多く, モノマー収着が重合を律速する因子ではなかった。付加ポリマーのうち見かけのグラフトポリマーは細胞壁内で均一に存在し, 局所性はみられなかった。以上の結果を総合し, 木材内部での収着質および付加ポリマーの分布についての推定を試みた。

Wood specimens were placed under the vapour phase of MMA-methanol mixtures and polymerized with gamma ray irradiation. The rate of vapour phase polymerization was affected by the temperature. From this point of view vapour phase polymerization was different from liquid polymerization which has a small activation energy. About 40% of the sorbed monomer was polymerized but the other part remained unpolymerized. This phenomenon was thought to be caused by the high methanol content in the micro pores of wood and the fact that the monomer molecules were surrounded with methanol. In the polymerization process the rate of sorption was not a factor of rate-determining step, since the rate was higher than that of polymerization. Autoradiographic observation indicated that the apparent grafted polymer was distributed uniformly within the cell wall. Following these results the distributions of sorbed materials and additional polymer in wood were discussed.