Effect of Phosphoric Acid on the Polycondensation of Bis(2-hydroxyethyl) Terephthalate Catalyzed by Sb(III) Compounds

Abstract

The influence of phosphoric acid on the activity of Sb(III) catalyst was studied in the catalytic polycondensation of bis(2-hydroxyethyl) terephthalate (BHET). Although the rate of polycondensation in the initial stage was depressed by the addition of phosphoric acid to the Sb(III) catalyst, subsequent polycondensation was accelerated to give a higher-molecular-weight poly(ethylene terephthalate) as compared with that obtained in the absence of phosphoric acid. The yield of by-products in the polycondensation was also affected by the addition of phosphoric acid; the formation of acetaldehyde decreased, and that of the diethylene glycol unit increased. It was made clear from studies of 31 P NMR that the phosphoric acid was converted into phosphate (0= P(OC2H4 0R)3) in the early stage of the polycondensation by reaction with BHET or ethylene glycol which was generated in the polycondensation ofBHET. It is assumed that the modification of the polycondensation reaction caused by the addition of phosphoric acid is due to the complexation of Sb(III) catalyst with the phosphate. The mechanism for the polycondensation of BHET catalyzed by Sb(III) compounds in the presence of phosphoric acid was proposed on the basis of these findings. KEY WORDS Bis(2-hydroxyethyl) Terephthalate I Poly(ethylene !erephthalate) I Polycondensation I Sb(III) Catalyst I Phosphoric Acid I 31p NMR I

Investigation of alkaline hydrolysis of polyethylene terephthalate by differential scanning calorimetry and thermogravimetric analysis

“…The IV value of 0.60 dL/g corresponding to the average molecular weight (M) of 17,000 was calculated from the equation of M ϭ 3.61 ϫ 10 4 IV 1.46. 17 The melting of this PET material yielded an endotherm about 40 J/g over the temperature range of 245 to 260°C, as determined by DSC at a scanning rate of 10°C/min.…”

Degradation and Recyclability of Poly (Ethylene Terephthalate)

“…The loss of carbon in the samples were seen by EDX analysis in our earlier studies also confirms this mechanism. This also accounts for the loss of pentaerithritol [34]. IV decreases with time reaches an asymptotic behavior because of the result of equilibrium established in the molten polymer.…”

“…This process gets more easily facilitated in presence of alkali. In this process loss of two formaldehyde molecules and a ketene take place resulting in loss of pentaerithritol [34].…”

The kinetics of diethylene glycol formation from bis-hydroxyethyl terephthalate with antimony catalyst in the preparation of PET

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