The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 27, 1999
Filed:
Feb. 19, 1998
Kathleen L Trojan, Greenville, SC (US);
Hoechst Diafoil Company, Greer, SC (US);
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.