Removal Of Free TDI From Polyurethane Prepolymer By Stripping

Due to the excessive use of Polyisocyanate during the synthesis process,Polyurethane prepolymer contains some free2,4-tolylene diisocyanate (TDI). AndTDI is toxicity. It has great impact on human body and the environment. In this paperexperimental and simulative researches on removal of TDI from the Polyurethaneprepolymer using Nitrogen stripping were carried out in this work to prove thatNitrogen stripping can satisfy the separation requirement.Firstly, concentration of TDI-time curve has been obtained by single-stageNitrogen stripping experiments. Fit the data of TDI-time curve with polynomial.Through the weight difference before and after the experiment prove that the TDI wascompletely collected in the buffer tank. The gas comes out from the buffer tank ispure Nitrogen, which can be recycled. Thus, the stripping process can be economic.Next, experiments of Nitrogen stripping were carried out in different Nitrogenflow rate in Laboratory. The experiment results were compared by figure. Fit the datawith quadratic polynomial, obtain the relationship of concentration of TDI andgas-liquid ratio. Compare the minimum gas-liquid ratio obtained by experiment to thetheoretical calculation, the value of relative error is10.11%. Which proved thatseparating TDI from Polyurethane prepolymer by Nitrogen stripping is feasible.Finally, Aspen Plus software was used to simulate the Nitrogen strippingprocesses of separating TDI from Polyurethane prepolymer. Through Model AnalysisTools choose the betterl operation data, the simulation result of the concentration ofTDI in the tower bottom is0.3%, which meet the separation requirement. And thesimulation minimum gas-liquid ratio is1.7. Compared with experimental andtheoretical calculation values, the relative errors are4.7%and5.9%, both were lessthan10%. The simulation results matched well with the experimental and theoreticalcalculation.