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Abstract

Disclosed is a process for the production of polyethylene terephthalate (PET), comprising the steps of (i) reacting di(C.sub.1 -C.sub.4)alkyl terephthalate with ethylene glycol to yield bis-(2-hydroxyethyl) terephthalate, (ii) adding a sequestering agent based on phosphorus and (iii) polycondensing the bis-(2-hydroxyethyl) terephthalate to produce PET; wherein in step (i) a zinc catalyst is present and in step (iii) an antimony catalyst is additionally present, the amount of zinc being in the range of from 0.003 to 0.008% by weight (30 to 80 ppm), the amount of phosphorus being in the range of from 0.001 to 0.01% (10 to 100 ppm), and the amount of antimony being in the range of from 0.01 to 0.05% by weight (100 to 500 ppm), in each case such weights being relative to the weight of the di(C.sub.1 -C.sub.4)alkyl terephthalate; the molar ratio of the antimony to the zinc being in the range of from 1:0.95 to 1:0.1; and the value, obtained by multiplying the molar ratio of the phosphorus to the zinc by the molar amount of antimony, is 4 or less. The PET produced in the process according to the invention contains a low number of particles, generally less than 400 per microgram, and can be formed into articles having a very smooth surface with only a minimum number of protrusions.

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First Claim