Kinetics of polyesterification of adipic acid with 1,3‐butanediol

The kinetics of non-catalyzed, acid catalyzed and alkyltin catalyzed polyesterification of adipic acid with 1, 3-butanediol as a model for polymeric ester synthesis was followed at 180°C and 215°C by monitoring of carboxyl, hydroxyl, and water content of the reaction system. The rate constants of the three processes were calculated using a simulation method. The process is kinetically controlled during the first 4–10 h (down to AV ≅ 20 mg KOH/g, conversion 95%) and then thermodynamically controlled by elimination of water from the system. Methyltin derivatives, especially trichloride, are more active catalysts but dibutyltin oxide can be used with good results. The model study suggests that addition of the catalyst at the beginning of the process and applying a vacuum (pressure 60 Torr) will reduce the reaction time in half, compared with adding catalyst at AV ≅ 20 mg KOH/g and using no vacuum.