Mechanistic investigations of antimony‐catalyzed polycondensation in the synthesis of poly(ethylene terephthalate)

Abstract

The chemical aspects of poly(ethylene terephthalate) synthesis via the antimony‐catalyzed polycondensation of hydroxy ethylene terephthalate end groups were studied to elucidate its mechanism. A polycondensation mechanism was proposed in which activation occurs by the formation of a chelate ligand on antimony composed of the hydroxyl end group and alcoholic oxygen of the ester of the same end group. The rate‐determining step of the polycondensation reaction was concluded to be the coordination of a second chain end to antimony. The low activity of antimony at a high concentration of hydroxyl end groups was proposed to result from the competition between hydroxyl end groups and the chelate structure leading to the transition state. The high selectivity of antimony is probably due to its relatively low Lewis acidity. Moreover, antimony was found to stabilize hydroxyl end groups against degradation by preventing their complexation to carbonyl functionalities. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1049‐1059, 2006

Quantitative HPLC-ICP-MS analysis of antimonyredox speciation in complex sample matrices: new insights into the Sb-chemistry causing poor chromatographic recoveries

“…25 Sb(III) is extensively used as a polycondensation catalyst in the production of poly(ethylene terephthalate), where it promotes esterification and transesterification. 26 Thus, antimony both forms polymers with organic molecules and catalyses polymerisation reactions.…”

Migration of antimony from PET trays into food simulant and food: determination of Arrhenius parameters and comparison of predicted and measured migration data

“…the catalyst is soluble in the reaction medium. The reaction of an applied Sb compound with ethylene glycol leads to the formation of a glycolate complex, which is the pre-catalyst (Biros et al 2002; Duh 2002; El-Toufaili et al 2006). Thus, the predominant diffusible species are monodentate glycolate (—Sb—OCH 2 CH 2 OH) and chelate ligand (—OCH 2 CH 2 O—) Sb complexes.…”

Kinetics and Mechanistic Investigation of Hydrotalcite‐Catalyzed Melt Synthesis of Poly(ethylene terephthalate)

“…Hydrotalcite was shown to be more active than antimony in polycondensation of BHET. [4][5][6][8][9][10] In a previous paper, [11] the effects of HT properties on its activity as a BHET polycondensation catalyst were studied. It was found that the hydroxide groups of HT are necessary for its catalytic activity.…”

“…[8][9][10]12] When the polycondensation reaction starts, EG is set free as a condensate by-product and is carried away from the reaction medium by inert-gas purging. This leads to mass loss that is recorded as a function of time and temperature.…”