Preparation Of TDI-100 By Falling Film Crystallization

Toluene diisocyanate?C₉H₆N₂O₂ TDI?is a widely used organic chemical raw material,mainly used in the production of polyurethane foam,plastic,rubber,insulating paint,adhesive,paint,elastomer and single component or two component coating composition.According to the position of isocyanate group on benzene ring,2,4-toluene diisocyanate?2,4-TDI?and 2,6-toluene diisocyanate?2,6-TDI?are two isomers.TDI is a mixture of two isomers in most industrial applications.However,compared with polyurethanes synthesized from these isomer mixtures,polyurethanes synthesized from pure 2,4-toluene diisocyanate?TDI-100?have particularly beneficial properties.The production methods of TDI-100 include pressure crystallization,atmospheric crystallization,catalytic polymerization,adsorption separation and static crystallization.However,the above methods have some shortcomings,such as high cost,complex process and difficulty in industrialization.Falling film crystallization is a crystallization technology developed in recent 30 years.This technology not only has the advantages of energy saving and low operating temperature of traditional crystallization technology,but also has the advantages of less time consuming and easy industrialization of equipment.In this paper,the physical and chemical properties of TDI-100 prepared by falling film crystallization method were measured at different temperatures and purities,and the phase diagrams of TDI were drawn.Based on this data,the experimental scheme of TDI falling film crystallization was designed,and the influence rule of crystallization effect under each parameter was studied.Through integrated analysis and design of optimized parameters,the experimental scheme of TDI falling film crystallization was designed.The falling film crystallization process was developed.Specifically as follows:?1?Densitometer and viscometer were used to measure the density and viscosity of TDI melt at different temperatures and purities,and empirical equation was used to fit them,and the fitting relationship was obtained.Supercooling data of TDI with different purity were determined by cooling curve method at cooling rates of 1 h,2 h,4 h,6 h and stirring rates of 200 R / min,300 R / min,400 R / min and 500 R / min.Based on the above experimental data,TDI phase equilibrium diagram was drawn.From the phase diagram,it can be seen that the feasible temperature range of TDI-100 crystallization separation process is 282K-289 K.Wilson equation,NRTL model and UNIFAC group method are used to fit it.It is concluded that UNIFAC group method has the highest fitting accuracy.?2?Densitometer and viscometer were used to measure the density and viscosity of TDI melt at different temperatures and purities,and empirical equation was used to fit them,and the fitting relationship was obtained.Supercooling data of TDI with different purity were determined by cooling curve method at cooling rates of 1 h,2 h,4 h,6 h and stirring rates of 200 R / min,300 R / min,400 R / min and 500 R / min.Based on the above experimental data,TDI phase equilibrium diagram was drawn.From the phase diagram,it can be seen that the feasible temperature range of TDI-100 crystallization separation process is 282K-289 K.Wilson equation,NRTL model and UNIFAC group method are used to fit it.It is concluded that UNIFAC group method has the highest fitting accuracy.?3?The falling film crystallization process with a total time of 8 hours was designed,and the economic evaluation index system of the crystallization process was established.By comparing the existing crystallization process,it was concluded that the advantages of the new design crystallization process lie in reducing the cost and increasing the daily output.