Preparation Of Methylene Dipheyl Diisocyanate Trimerization

Some problems such as low crosslinking density, flexible film, slow rate of drying, lie in the methylene diphenyl diisocyanate (MDI) polyurethane coating. Preparation of MDI-based trimer was studied in order to solve the problems through using MDI-based trimer in this paper. The main research includes:to selecte auxiliaries for synthesis of MDI-50 trimer, to develop and optimize the synthesis process, to investigate MDI-50 trimerization kinetics and to modify MDI-50 trimer.The experiment that compared with other catalysts, selected complex catalyst P838 as trimerization catalyst. Through process optimization, the solvent was added in batches to prepare MDI-50 trimer, of which the tolerance of xylene was 0.7, the viscosity was 60mPa-s/25℃, the free MDI content was 10.55%. The reaction kinetics of the trimerization of MDI-50 was studied by FT-IR spectroscopy. The results showed that the trimerization of MDI-50 was first grade reaction, and the rate of the trimerization reaction (Ka) was 0.0076 at 60℃, the average energy of activation was 79.33 kJ/mol. In order to improve the compatibility of trimer and solvent, ethylene glycol monobutyl ether (BCS) and diethylene glycol monobutyl ether (DBG) were used to modified MDI trimer. The xylene tolerance of modified MDI-50 trimer could be above 1.0. Simple experiment with paint showed that MDI-based trimer could be consistent with alkyd resin each other and the rate of drying, and the hardness of film had been enhanced effective, which could be applied to wood coatings.