Abstract:

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 eharacterized hy means of Ff-IR. It is found that there are some unreacted hydroxyl groups (-OH) in polyurethane prepolymer under normal conditions , hut 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, hy analyzing the synthesis mechanism , it is revealed that the spatial steric hindrance and the indefinahle 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 he obtained and the TDI residual in reaction system can be separated hy a thin-film evaporator.

Key words: polyurethane, thin-film evaporation, toluene diisocyanate, curing agent, trihydroxymethyl propane, synthesis, polyurethane prepolymer