The Synthesis Of Toluene Diisocyanate Trimer And Its Pilot Study

Toluene diisocyanate(TDI)trimer is widely used in two-component polyurethane coatings due to its excellent properties of multi-functionality,high hardness,good thermal stability and corrosion resistance.At present,the TDI trimer products in the domestic market generally have high viscosity,high free TDI content,and poor compatibility with resins.Although the foreign TDI trimer products have low content of free TDI and good in performance,they are expensive.Therefore,this paper is aim to prepare a low free monomer,low visocity and high compatibility TDI trimer on the basis of researching the synthesis of TDI trimer,and conduct the pilot study based on the maturity of the experiment.The specific experiment contents are as follows:Based on the empirical formula,the catalytic effect of the catalyst species and the catalytic effect at differernt reaction temperatures was explored.The results show that the catalytic effect of DMP-30 and self-made catalyst M-01 are better than others,and the M-01 has a nagetive temperature effect at high temperature;then the orthogonal experiment was carried out in the types of catalyst,the amount of catalyst and the reaction temperature to determine the best reaction conditions.Based on the above results,the types of modifiers and the amount of the modification were explored.When the modifier was n-octadecanol and the molar ratio of NCO and OH was 16,the compacilitiy of the product could reach 3.7.Through the above experiments,the TDI trimer was obtained in lab-scale experiment with solid content of 50.63%,NCO content of 7.05%,the compacilitity of 3.7,viscosity of 360 cp and free TDI content of 0.38%.In the process of pilot study,the viscosity of reaction system was too large that results mixing unevenly,the system temperatue fluctuated greatly,the reaction speed compared to lab-scale experiment was too fast and so on,these problems made the product of physical properties could not achieve the expected value,and the product performance was poor.In view of the above problems,we improved the equipment and process,the improvement of measures are as follows: choosed the better agitator and adjusted agitation speed;reduced the temperature of condensate water to rationalize the system temperature;adjusted the order of addition of modifiers to greatly reduce the viscosity of the reaction system;reduce the water of the entire reaction device and the reaction material,and pass nitrogen to protect the reaction system during the reaction.Through the above series of improvement measures,the pilot product was finally obatained which can basically achieve the expected target value.The basic physical,chemical properties,storage stability and application performance of self-made light TDI trimer were tested and compared with the same type of high quality products on the market.Experiments show that self-made TDI trimer has a good storage stability.In the preparation of two-component polyurethane coating,it was found that the performance of the paint films made with self-made TDI trimers was very close to that of the paint films made by Bayer L1451 and AC510;in addition,the paint films of self-made TDI trimers was superior to G07 B and W6856 F in terms of dry-surface time,finger-pressing dry time,and yellowing resistance.