Process and catalyst-inhibitor systems for preparing poly(ethylene terephthalate)

Process for producing polyesters comprising reacting dimethyl terephthalate with at least one glycol selected from ethylene glycol and combinations of ethylene glycol with up to about 10 mol % 1,4-cyclohexanedimethanol at a temperature sufficient to effect ester interchange and in the presence of a catalyst system comprising

• (a) manganese, zinc or calcium salts wherein the manganese, zinc or calcium is present in an amount of about 25-110 ppm,
• (b) cobalt salts wherein the cobalt is present in an amount of about 10-100 ppm,
• (c) an antimony compound wherein the antimony is present in an amount of about 150-350 ppm,
• (d) a phosphorus compound wherein the phosphorus is present in an amount of about 15-240 ppm, and
• (e) a complex of titanium alkoxide with an alkali or alkaline earth metal salt wherein the titanium is present in an amount of about 10-100 ppm titanium and wherein the metal:
• titanium atom ratio is at least 0.25:1,
• the ppm in (a) through (e) above being by weight based on the acid fraction of the polyester.