Models for Polyesterification Kinetics. III. Preliminary Studies on the Catalysis by Titanium(IV) Tetraalkoxides

The catalytic behavior of tetrabutoxytitanium in polyesterification between diacids and diols is studied with the help of two model reactions. One is the esterification between two mono-functional oligomers. The second is the reaction of 1-octa-decanol with octadecanoic acid either in octadecanyl octadecano-ate or in an excess of octadecanol. The behavior of this catalyst is complex since it depends on the reaction medium. A decrease of the vacuum and an increase of the acid concentration lead to poor catalytic efficiency which is also observed when the reaction is carried out in a hydrophilic medium such as polyoxy-ethylene. When the alcohol is in excess, the catalyst is much more efficient and experimental results fit with a zero overall order, although deviations are observed at the highest conversions. The existence of a complex between carboxyl groups and titanium is postulated.