NUMERICAL MODELING FOR SIMULATION AND EXPERIMENTAL INVESTIGATION ON PURIFICATION PROCESS OF TDI BY ZONE MELTING

A method of zone melting was applied to measure the effective distribution coefficient of the impurity 2, 6-toluene diisocyanate under different conditions, using a purity of 80% toluene diisocyanate (i.e. TDI-80) as the raw material. The influence of zone melting rate, temperature difference between the molten zone, zone melting passes on the concentration distribution of impurity was analyzed, and the numerical model of the impurity 2,6-toluene diisocyanate distribution was established. The results show that the zone melting can effectively separate the two TDI isomers; zone melting rate and the temperature difference between the molten zone are the main parameters affecting the effective distribution coefficient of impurity; the numercial model can satisfy the experimental values well, through comparison of experimental and the calculated values, and it can be better to indicate the concentration distribution of 2,6-toluene diisocyanate after several zone melting passes; finally the model can provide a theoretical guidance on the purification process of TDI by zone melting.