Adipic Acid → Hexane-1,6-diol adipate

Participants

Reaction Steps

A hot solution at 110° C. of 730.7 g (5 mol) of adipic acid in 650 g (5.5 mol) if hexane-1,6-diol was placed into the first reactor of a reactor cascade comprising acid-resistant material, which consisted of three series-connected reactors having a volume of 5 l each and each fitted with a rapid stirring system of customary construction (turbine stirrer, rotary speed: from 800 to 1200/min) and a distillation column (10 theoretical plates), the solution was quickly heated with stirring to a reaction temperature of from 140° to 150° C., and the water of reaction which formed was distilled off under atmospheric pressure. After a residence time of 1.5 hours, the reaction mixture was transferred to the adjacent second reactor, in which a further portion of the water of reaction was distilled off under atmospheric pressure with stirring at a reaction temperature of from 150° to 180° C. Finally, after a further residence time of 1.5 hours, the reaction mixture was transferred to the adjacent third reactor, where the remainder of the water of reaction was removed under a pressure of 400 mbar and at a reaction temperature of from 180° to 190° C. After a residence time of 1.5 hours more (4.5 hours in all), the desired degree of esterification had been reached. The oligomeric hexane-1,6-diol adipate obtained (1,290 g) had an average degree of oligoesterification (=number of molecules of adipic acid in the oligo ester) of n=4 (measured by gel permeability chromatography) and an acid number of 25 mg of KOH/g of reaction mixture. After partial or complete emptying of the first reactor, it was possible to continue the esterification process in a quasi-continuous manner by adding new quantities of reaction mixture.

Provenance & Evidence