咪唑封端型水性聚氨酯固化剂的合成及其应用

以异佛尔酮二异氰酸酯(IPDI)和三羟甲基丙烷(TMP)为起始原料,经过加成反应,二羟甲基丙酸(DMPA)扩链,三乙胺(TEA)中和成盐及2-甲基咪唑(2-MI)封端等4步反应后,制得一种可在室温解封的水性聚氨酯固化剂。2-甲基咪唑封闭反应的较好条件为:2-MI与-NCO摩尔比为1.1~1.2;反应温度为60℃;反应时间2 h。实验结果表明,咪唑封闭型水性聚氨酯固化剂可明显降低异氰酸酯与水的副反应速度,凝胶时间由5 min增加到5.5 h。羟基水性树脂中加入5%咪唑封闭型水性聚氨酯固化剂后,成膜物的耐水性和力学性能均有明显改善。

Synthesis and application of waterborne imidazole-blocked polyisocyanates

Using isophorone diisocyanate(IPDI)and trimethylolpropane(TMP)as raw materials.a nbvel waterborne polyisocyanate,which can be used as the curing agent and deblocked at room temperature,was synthesized after four steps of chemical reactions.Those four steps of chemical reactions were additional reaction,chain extension with 2,2-bis(hydroxylmethyl)propionic acid(DMPA),neutralization with triethylamine(TEA)and blocking with 2-methylimidazole(2-MI),respectively.The optimum conditions for the synthesis of blocked-polyisocyanates were found as follows:the molar ratio of 2-MI/-OCN was from 1.1 to 1.2,the blocking reaction temperature was 60℃,and the blocking reaction time was 2 h.Results show that the velocity of side reactions between polyisocyanates and water was obviously retarded because of imidazole-based blocking of polyisocyanates,and the gelation time delayed from 5 min to 5.5 h as a result.The water resistance and mechanical property of water-borne polyol resins can be improved obviously after 5% imidazole-blocked polyisocyanate was used as the curing agent.