Process for producing polyesters using a niobium compound as a catalyst.

摘要

A process for producing a linear polyester comprising a main structural unit of an aromatic dicarboxylic acid ester of an alkylene glycol, particularly, comprising a polyethylene terephthalate or polytetramethylene terephthalate unit, is provided. In the process of the invention, the polycondensation reaction is conducted in the presence of a niobic acid catalyst that is obtained by heat-treating a hydrated niobium compound at the temperature range between 80 DEG C and 400 DEG C. The process of the invention is also effectively applied to the manufacture of an elastomeric polyester comprising a polyalkylene terephthalate as a hard segment and a polyalkylene glycol as a soft segment.