| 摘要 |
A process for the polymerization of polytrimethylene terephthalate by esterification of terephthalic acid or dimethylterephthalate with 1,3-propane diol, precondensation of the esterification product to produce a precondensation product, and polycondensation of the precondensation product to produce polytrimethylene terephthalate and, as a byproduct, the cyclic dimer of terephthalic acid or dimethyl terephthalate and 1,3-propane diol, comprising: (a) recovering the cyclic dimer from the polymerization, (b) reacting from 0.5 to 25 percent by weight of the cyclic dimer in 1,3-propane diol in the presence of from 0.1 to 10 percent by weight of the cyclic dimer of a basic catalyst for five minutes to 24 hours at 50 to 210 <o_>C, (c) optionally neutralizing the basic catalyst in the reaction product of (b), and (d) recycling the reaction product into the polymerization process. |
