Comparison between titanium tetrabutoxide and a new commercial titanium dioxide based catalyst used for the synthesis of poly(ethylene terephthalate).

Titanium-based catalysts for poly(alkylene terephthalate) synthesis were known for many years. Up to now, organotitanate compds. are used as catalysts on an industrial scale only for the synthesis of poly(butylene terephthalate) (PBT), poly(trimethylene terephthalate) (PTT), and related copolyesters; for poly(ethylene terephthalate) (PET), synthesis antimony-based catalysts are preferred. In fact, in this case, titanium is known to cause undesirable discoloration. In this article, a study of PET synthesis using different concns. of a new titanium dioxide based catalyst (C-94), com. available from Acordis Industrial Fibers GmbH, is carried out and compared with the results obtained with titanium tetrabutoxide (TBT) catalyst in the same exptl. conditions. The solid-state properties and compn. of C-94 was studied by thermogravimetric anal. (TGA) coupled with mass spectroscopy and by x-ray powder diffraction (x-ray diffraction). A characterization of the polymers prepd. with C-94 and TBT is also described. The results have shown that the use of C-94 leads to more hydrolytically stable polymers, whereas no evidence of difference in the catalytic activity, carboxyl end-groups concn., diethylene glycol content, and thermal properties were revealed.