Synthesis of Low Freeness TDI Trimer

Synthesis of low-free TDI trimers

Toluene diisocyanate (TDI) can undergo a trimerization reaction under catalysis to form a trimer containing an isocyanurate ring. TDI trimer has the advantages of low volatility, low toxicity, high functionality, good thermal stability and good corrosion resistance, and is often widely used as a polyurethane curing agent in coatings and adhesives. In the 70s of the 20th century, many foreign companies began to industrialize the production and application of such products, such as Bayer, BASF, Dow, etc. At present, TDI trimers with high performance and low free monomers still need to rely heavily on imports.

In this study, the catalyst NT CAT P100 was used to synthesize TDI trimer polyurethane curing agent, and the experimental results showed that the catalyst had the advantages of fast catalytic rate, high activity and low reaction temperature. At 40 °C, the reaction was catalyzed by dropwise addition, and the reaction end point could be reached in 8 h, and TDI trimers with low free monomer content were obtained .

Raw materials and reagents

Toluene diisocyanate monomer TDI (80/20): industrial product, BASF; Butyl acetate: analytically pure, Guangzhou Panyu Force Strengthening Factory; NT CAT DMP-30: Industrial Products, New Chemicals NT CAT K-15: Industrial Products, New Dictionary Chemical; NT CAT P100: Codex Chemistry;

Synthesis process

100 g of TDI(80/20) monomer and 100 g of butyl acetate were added to a dry four-mouth round-bottom flask with stirring, thermometer and reflux condenser tube under nitrogen protection. Stir for 5 ~10 min, heat to 40 °C, add 0. 5 gCatalyst butyl acetate solution (butyl acetate 10 mL). After the dropwise addition is completed, the temperature is controlled between 40 ~80 °C, and the heat preservation reaction is about 8 h, every 1 hThe —NCO value of the primary reaction solution was determined, and when the —NCO content was reduced to 8.5% ~ 9%, 1 g was addedBenzoyl chloride, the reaction was continued for 0.5 h, the heating and stirring were stopped, and the material was cooled to obtain a light yellow transparent liquid.

On the basis of the above process, the preset amount of alcohol was added dropwise, and the TDI trimer was modified by holding the reaction for 30 ~60 min.

The influence of catalyst type, dosage and dropping method

The choice of catalyst is key to the TDI trimerization reaction. Commonly used TDI trimer catalysts include tertiary amines, organometallic compounds, organophosphine compounds, alkali metal carboxylates, etc. DMP-30, K-15 and P100 were selected for TDI with 50% butyl acetateThe solutions catalyzed the reaction separately, and the results are shown in Table 1 and Figure 2.

Table 1 TDI effects of different catalysts (0.5% addition).Effect of trimerization reaction

As can be seen from Table 1 and Figure 2, the trimerization reaction of TDI does not occur without catalyst; The catalytic trimerization effect of K-15 is poor, the temperature is high, the reaction time is long, and it is easy to produce more multimer structures. DMP-30 and P100, both tertiary amine catalysts, have better catalytic effect, while P100 has stronger catalytic performance and can react rapidly and reduce in a short time—NCO value, and experiments also show that it still has high catalytic activity at 40 °C. Therefore, P100 was chosen as the catalyst. Figure 3 is the P100