Formation of new alkyl functionalized poly(ethylene terephthalate) oligomers through exchange reactions with titanium alkoxides in melt conditions

A new and original method to recycle the PET into low molar masses di-alkyl functionalized oligomers is proposed. Ti(OnBu)4 and Ti(OnPr)4 used through alkoxide ligand exchange reactions, with a vertical twin-screw micro-extruder laboratory process, allow in a very short range of time around 10 min at high temperature to shorten the PET chains length. In homogeneous-like considered conditions fast decreases of molecular chains length and melting temperatures were observed. The structures of these oligomers were identified by 1H NMR, MALDI-ToF and SEC methods, and then correlated with physical properties determined by DSC and TGA analyses. Very useful tools are proposed to control the chemical reaction in order to scale up this process to reactive extrusion at relatively low temperatures.