| 摘要 |
In an improved process for preparing high molecular weight polyester polymers, such as poly(butylene terephthalate), an alkylene glycol and a di- or tricarboxylic acid or its alkyl ester are reacted in a first step to prepare a pre-polymer in the form of uniform solid particles having an intrinsic viscosity of from 0.1 to about 0.3 dL/gm and a chemical composition which contains greater than a 1 % stoichiometric excess of the alkylene glycol above the amount required to produce a high molecular weight polymer, and then polymerizing the pre-polymer in the solid state. This process avoids the usual melt-polycondensation step at reduced pressure and very high temperature.
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