| Abstract: | The influence of different types of catalysts on the polycondensation reaction has been studied in a model system. It has been found that two kinds of catalysts are to be distinguished. “Transesterification” catalysts (Mn, Pb, Zn) are very active in media having both a high and a low hydroxyl content. However, they are easily poisoned by very small amounts of carboxylic endgroups. This restricts their activity to the period of transesterification. The “polycondensation” catalyst antimony is insensitive to the presence of acidic endgroups. However, its activity is inversely proportional to the hydroxyl group concentration For this reason antimony is hardly effective during transesterification. During polycondensation it becomes gradually more active. |
