POLYETHYLENE TEREPHTHALATE AND PRODUCTION THEREOF

PURPOSE: To obtain a resin little in oligomer formation causative of mold staining during molding by adding a specific metallic element in the step of esterification to the step of liq. phase polycondensation in preparation of polyethylene terephthalate and treating the product with water after solid phase polycondensation. CONSTITUTION: In the production of polyethylene terephthalate(PET) comprising step I of esterification of terephthalic acid (deriv.) with ethylene glycol (deriv.), step II of liq. phase polycondensation of the resulting ester, step III of solid phase polycondensation of the resulting polycondensate, and step IV of contact of the resulting polycondensate with water; at least 1 element (contg. compd.) among Ti, Zn, Mg, Mn, Ca, Co, Cu and Ni is added in step I or II to produce PET having a molar ratio M2 /M1 of 0.01 to 50 (wherein M1 is a metal originating from a polycondensation catalyst in PET, and M2 is the added element) and satisfying the relationship: W1 -W0