酸性环境下脲醛树脂结构形成特征

The Structure Formation of UF Resins Under Acidic Condition

使用１３ ＣＮＭＲ研究酸性环境下脲醛树脂结构形成特征，结果表明：酸性条件下所合成的脲醛树脂与传统脲醛树脂结构差异显著．在强酸条件下，由于亚甲基化速度高于羟甲基化速度，尿素的加入以形成亚甲基桥键为主，或者说形成的羟甲基迅速转化为亚甲基桥键．强酸条件下合成的脲醛树脂结构中存在Ｕｒｏｎ 环，其分子链交联点较多．在弱酸条件下，由于亚甲基化速度和羟甲基化速度基本相近，产物结构特征介于强酸与传统合成工艺之间．

Structure formation of UF resins under strong and weak acidic conditions were investigated with high resolution 13 CNMR (DRX-500).The structures of resins prepared under acidic conditions was difference greatly with typical UF resin.The crucial factor seems to be the different reaction rate of methlolation and methylene bond formation.Under strong acidic condition,methylene bond formation is fast than methlolation,so the main constituents of UF resins are contents with much high methylene.Strong acid catalyzed UF resin characters as Uron and high cross linkages contain.Under weakly acidic conditions,since methlolation and methylene bond formation go with almost equivalent rate,the structure constituents of resin seem to be average of typical resin and strong acidic catalyzed resin.