摘要 |
Disclosed is an improved process for the preparation of high molecular weight linear polyesters. In the preparation of polyesters by formation of a bis-dihydroxy ester prepolymer by transesterifying dimethyl terephthalate with a glycol in the presence of a catalyst followed by polycondensing the prepolymer in the presence of certain phosphorous-containing compounds and a transition metal-containing catalyst which remains active in the presence of said phosphorous compound, an improved rate of polycondensation is achieved by introducing the phosphorous compounds after first polycondensing the prepolymer to a low molecular weight linear polyester having an average degree of polymerization of about 2 to about 10. The improved process further requires that the catalyst employed in the formation of the prepolymer be substantially inactive in the presence of said phosphorous compounds.
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