Method of post-polymerization stabilization of high activity catalysts in continuous polyethylene terephthalate production

In a continuous process for making polyethylene terephthalate polyester that includes the steps of:

• reacting ethylene glycol and terephthalic acid in a heated esterification reaction to form an oligomer of terephthalic acid and ethylene glycol and water;
• removing the water as it is formed in the reacting step to enable the esterification reaction to essentially go to completion;
• heating the oligomer and adding a polymerization catalyst system that includes a first component of at least one of cobalt, zinc, magnesium, manganese, and calcium, and a second component of antimony to polymerize the oligomer in a polycondensation reaction thereby forming a polymer melt containing polyethylene terephthalate polyester and ethylene glycol;
• and
• removing the ethylene glycol as it is formed in the heating step to allow the oligomer to enable the polycondensation reaction to essentially go to completion;
• the improvement in the continuous process comprising:
• adding a phosphorous-containing stabilizer to the substantially entirely polymerized polyester melt after the polycondensation reaction in the heating step, prior to processing the polymerized polyester, and in an amount sufficient to deactivate the polymerization catalyst to thereby permit the polymerization catalyst to increase the throughput of the polyethylene terephthalate polyester during the majority of the polymerization while preventing the polymerization catalyst from degrading and discoloring the resulting polyethylene terephthalate polyester.