氨基甲酸酯和脲生成反应的机理与动力学

REACTION MECHANISM AND KINETICS OF URETHANE AND UREA FORMATIONS

综述了氨基甲酸酯（ＵＴ）和脲（ＵＡ）的自发反应和叔胺催化、有机锡催化、锡－胺协同催化反应的机理与动力学，以及反应介质、有机酸、水解氯、活泼氢组分分子结构及反应体系相态对反应的影响。ＵＴ和ＵＡ的生成反应存在产物催化现象。反应机理不仅与催化剂的性质有关，而且与反应物的结构和溶剂的性质有关。近期对反应注射成型体系的研究表明，相分离在聚合过程的早期发生，此后反应转为扩散控制。ＵＡ生成反应的动力学行为受相态的影响更甚。总包反应动力学可总结为ｄ［Ｕ］／ｄｔ＝Ａ０［ＡＨ］ｍ［ＮＣＯ］·ｅｘｐ（－Ｅａ／ＲＴ）。式中指前因子Ａ０与反应条件有关，活化能Ｅａ与反应物结构有关。［ＮＣＯ］为异氰酸根的浓度，［ＡＨ］为活泼Ｈ物质如羟基或ＮＨ２基的浓度，ｍ为与ＡＨ有关的反应级数。对ＵＴ生成反应，ｍ＝０．５～１。对ＵＡ生成反应，ｍ＝１～２，ｍ越接近２，产物催化作用越大。

The reaction mechanism and kinetics of the'spontaneous' urethane(UT)and urea(UA)formations,as well as the formations catalyzed by tertiary amine,organotin compounds and organotin-tertiary amine catalytic systems were reviewed with 55 references.The factors which influenced the mechanism and kinetics were the nature of reaction mechanism,impurities such as carboxylic acid and hydrolysis chloride,molecular structure of reactants,3-D networks formation,and phase separation during the reactions.Product catalysis was remarkable especially in urea formation.Recent study of reaction injection moulding showed that the influnence of phase separation during polymetherization on reaction kinetics was very important.The kinetics was diffusion-controlled after phase separation took place.The overall reaction kinetics could be concluded as: d[ U] /dt = A0[ AH]m[NCO] .exp(-Ea /RT) .