KINETIC AND CATALYTIC ASPECTS OF THE FORMATION OF POLY(ETHYLENE-TEREPHTHALATE) (PET) INVESTIGATED WITH MODEL MOLECULES

Kinetic and catalytic aspects of the formation of poly( ethylene terep hthalate) (PET) have been studied in this work using model molecules s uch as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB),and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), syn thesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on som e catalysts under different operative conditions to evaluate the effec t of catalyst concentration and temperature on the reaction rate. We h ave observed that a second-order kinetic law is suitable for both cond ensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst con centration in a different way for each type of catalyst. Bivalent meta ls activity is affected by the presence of a substituent in the aromat ic ring, unlike tri- and tetravalent metals. Suggestions on the reacti on mechanisms conclude the work. (C) 1998 John Wiley & Sons, Inc.