聚氨酯固化剂的合成与反应机理

采用FT-IR分析技术对甲苯二异氰酸酯-三羟甲基丙烷(TDI-TMP)固化剂合成反应体系在不同反应条件下得到的聚氨酯预聚物进行表征,发现在通常的工业合成条件下得到的聚氨酯预聚物有未反应的OH存在,而在高温合成条件下OH完全反应.结果表明TMP的实际官能度与反应条件有关.从反应机理的角度,分析并发现空间位阻和反应的不确定性是导致较低温度下羟基反应不完全和国产合成固化剂储存时间短的原因.最后提出了合成聚氨酯预聚物的工艺,采用该工艺所合成的聚氨酯预聚物分子结构较理想,且合成体系中残留的TDI可用薄膜蒸发器进行分离回收.

Synthesis and Corresponding Mechanism of Polyurethane Curing Agent

The reaction systems of toluene diisocyanate-trihydroxymethyl propane(TDI-TMP) were studied under different conditions for the preparation of polyurethane curing agent,and the products were characterized by means of FT-IR.It is found that there are some unreacted hydroxyl groups(OH) in polyurethane prepolymer under normal conditions,but the hydroxyl groups thoroughly join the reaction at a higher temperature.This means that the functionality of TMP is related to the reaction conditions.Moreover,by analyzing the synthesis mechanism,it is revealed that the spatial steric hindrance and the indefinable reaction of hydroxyl groups are the reasons for the incomplete reaction of OH and the short storage period of the curing agent made in China.The authors finally present a technology to synthesize polyurethane prepolymer,from which ideal molecular structure can be obtained and the TDI residual in reaction system can be separated by a thin-film evaporator.