INVESTIGATION ON MODEL MOLECULES OF THE REACTIONS INDUCED BY TRIPHENYL PHOSPHITE ADDITION DURING POLYESTER PROCESSING

Reactions between model compounds were carried out at high temperature s (150-250 degrees C) in order to provide a correct simulation of the behavior of hydroxyl and carboxyl polyester chain ends in the presence of triphenyl phosphite (TPP). The reaction between TPP and alcohol (3 -phenyl-1-propanol) leads to phenoxy/alkoxy substitutions on the phosp hite. The elimination of phenol in open systems is considered as the d riving force of this reaction. The occurrence of multisubstitutions be tween alcohol and phosphite is confirmed. On the other hand, carboxyli c acid (4-tert-butylbenzoic acid) reacts with triphosphite to produce ester (or phenyl ester) and phosphonate. The driving force is the crea tion of a stable phosphoryl bond. NMR experiments lead furthermore to conclusive results concerning the higher velocity of the acid reaction with aliphatic phosphite than of the acid reaction with aromatic phos phite. In the reactions involving alcohol, acid, and phosphite, the co nditions favoring ester formation are explained: The presence of TPP i s seen to greatly promote the ester production.