KINETICS OF POLYESTERIFICATION OF ADIPIC ACID WITH 1,3-BUTANEDIOL

The kinetics of non-catalyzed, acid catalyzed and alkyltin catalyzed p olyesterification of adipic acid with 1, 3-butanediol as a model for p olymeric ester synthesis was followed at 180 degrees C and 215 degrees C by monitoring of carboxyl, hydroxyl, and water content of the react ion system. The rate constants of the three processes were calculated using a simulation method. The process is kinetically controlled durin g the first 4-10 h (down to AV congruent to 20 mg KOH/g conversion 95% ) and then thermodynamically controlled by elimination of water from t he system. Methyltin derivatives, especially trichloride, are more act ive 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 congruent t o 20 mg KOH/g and using no vacuum.