The Synthesis And Application Of High Compatibility And Low Monomer Content Toluene Diisocyanate Trimer Curing Agent

Toluene diisocyanate(TDI) trimer is a kind of 2K polyurethane coating hardener, which can promote the performance of the film’s drying rate and hardness. There’re many TDI trimer products in the market, but almost all the high-grade TDI trimers are imported abroad. To prepare a high compatibility and low free monomer TDI trimer was the main aim of this research while the regularity of TDI self-polymerization, synthetic formula, technology and the performance was researched. The research includes the following parts:The influences including the kind and amount of catalyst, synthetic temperature and the amount of TDI initial addition on the TDI self-polymerization were discussed. The regularity of TDI molecular reaction was researched by following the contents of the isomers in free monomer. After the compatibility promotion from the additional modified primary alcohol was researched, the final formula and technology was determined. 60wt% TDI-80 with 40wt% butyl acetate were catalyzed by 0.3wt% DMP-30 under 80℃. Then, the equal amount of TDI-100 to the TDI-80 was dropwise added into the system. Dodecanol was used to enhance the TDI trimer’s compatibility while the optimal molar rate of NCO and OH is 20. The high compatibility and low free monomer TDI trimer was obtained with solid content of 50.43wt%, NCO content of 7.03wt%, viscosity of 320 cp, free monomer of 0.44wt% and compatibility of 3.5.Index, storage stability and performances were compared between self-made and other kinds of TDI trimers. The results show that self-made TDI trimer has good storage stability, after six months at room temperature or four weeks at 50℃ storage, the index of NCO content and viscosity had small changes. TDI trimers were mixed with TDI adduct in the application test. The performances of drying rate and hardness correlated with the amount of TDI trimer in mixed hardener. Meanwhile, performance of gloss and fullness decreased little by mixed with self-made TDI trimer. All the results show that self-made TDI trimer reach the standard of high compatibility and low free monomer TDI trimer.