The Synthesis And Application Of Non-Toxic Matte TDI Trimer Curing Agent

Toluene diisocyanate trimer is mainly used for two-component polyurethane coatings as a curing agent due to its excellent performance.There are many kinds of TDI trimer in the market,but there are various problems in domestic products,most of the products with good performance come from abroad and are expensive.Therefore,this research aims to develop a non-toxic matt TDI trimer with good performance,and research on catalysts,modifiers,synthetic formulations and processes,and paint properties.The specific work is as follows:Firstly,the simplest synthetic formula was used to explore catalytic activity in different catalyst types,catalyst dosage,and reaction temperature.It was found that the catalytic rate of DMP-30 was stable.the TDBA was the best in the first 5 hours and become weak in the latter stage.When DMP-30 was added at a concentration of 0.45wt% at 80°C and TDBA was added at a concentration of 0.30wt% at 70°C,the average molecular weight and free TDI monomer content of the product were lower.Dodecanol was found to have the highest tolerance of TDI trimer when it was added by the NCO to OH molar ratio of 18.Then,the synthetic formula was optimized,using DMP-30 and TDBA compound catalyst,control the temperature to 70°C at the first five hours then rise to 80°C,the dodecanol was added when the NCO content drop to 12%,and according to the orthogonal experiment,when added at a concentration of 0.23wt% of DMP-30 with 0.17 wt% of TDBA,the product has the best tolerance.Finally,the TDI trimer is synthesized with the optimized process.The non-toxic matte TDI trimer contain the following properties: 8.07% NCO value,51.25% solid content,2.56 tolerance,1260 cp viscosity,0.40% free TDI monomer content.The self-synthesized TDI trimer applying performance was compared with the same type of product Bayer L1351 and Mitsui D268.It was found that the basic physical and chemical indicators were basically consistent and had good storage stability.The effects of the three different TDI trimers with different dsage on the properties of the paint film were compared,and found they could significantly improve the film properties.Also,each indicator has the similar variation,the drying speed and hardness are quite the same.but the flexibility and glosss are not good enough.Moreover,when the TDI trimer is added in an amount of 30%,the performance of the self-synthesized TDI trimer is comparable to that of the L1351 andD268 paint films.In addition,the effects on the coating film properties of self-synthesis TDI trimer and external matting powder were also studied.It was found that the matting performance was slightly better than that of the matting powder,and the self-synthesis TDI trimer has achieved self-extinction.Except for the fullness of paint film,the overall performance are pretty good,Especially for the advantages in clarity and flexibility are obvious.