Study On Harmfulless Polyurethane Curing Agent

This dissertation has summarized that around how to produce proper polyurethane(PU) curing agent which consists of toluene diisocyanate(TDI) and trimethylolpropane(TMP) product and how to reduce the content of dissociative TDI in it below 0.5% to carry on the research. The contents of dissertation mainly includes synthesizing the TDI-TMP PU curing agent, separating unreacted TDI from the agent, establishing of the mass and heat transfer model to describe the separation process, designing and fitting the pilot plant. The final target of the research is to produce qualified product of curing agent and industrialize.In order to distil TDI from the curing agent and obtain a qualification agent with a short-path distillation equipment, we first put forward a suggestion that a suitable agent should be a small molecular weight and react thoroughly so that before all others we study synthetic technology of the TDI-TMP curing agent with small molecular weight. We have studied the influence of the pH value of reactive system on the synthetic curing agent. The experimental results show that the reactive system happens some subsidiary reactions when the system appears mild alkali or strong acidity. The study results also show that the viscosity of the curing agent should be as possible as low. We got some measures to reduce the viscosity of the reactive system such as adding some phosphoric acid, adopting the feeding method of once loading, raising the temperature of the reactive system step by step, increasing the mole ratio of TDI/TMP as possible as large but in order to reduce the burden of distillation, the mole ratio was chosen 4.6 '. 1. Water which is danger to reactive system was investigated so that TMP should been dehydrated before it was been loading.Fourier transform infrared (FTIR) was used to characterize PU curing agent. The FTIR analysis shows that hydroxyl group still exists in despite of TDI is excessive. It illuminated that three hydroxymethyl group is not stretch in space because of steric hindrance although three of them are carbinol. The characterizing results show curing agent without hydroxyl group because it had reacted thoroughly when the curing agent places amid high temperature in distillation equipment.Based on the experimental research above, the curing agent with small molecular weight and low viscosity has been made.The separation TDI from PU curing agent was carried on with model MD-S80 short-path distillation equipment. The research method of considering both technology...