Abstract: The invention provides a method for producing polyester comprising: a step for preparing an oligomer comprising a dicarboxylic acid diester by an esterification reaction or a transesterification reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, and then a step for subjecting the oligomer to melt-polycondensation to provide polyester as melt-polycondensate, wherein at least in the step of subjecting the oligomer to melt-polycondensation of the two steps, the oligomer is subjected to melt-polycondensation in the presence of titanium nitride and, as a polycondensation catalyst, particles of a solid base having a coating layer of titanic acid on the surfaces, thereby to provide polyester as melt-polycondensate.

Abstract: The invention provides a polycondensation catalyst for producing polyester by an esterification reaction or a transesterification reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, wherein the polycondensation catalyst comprises particles of a solid base having on the surfaces an inner coating layer of titanic acid in an amount of from 0.1 to 50 parts by weight in terms of TiO2 per 100 parts by weight of the solid base, and an outer coating layer either of an oxide of at least one element selected from aluminum, zirconium and silicon, or of a composite oxide of at least two elements selected from aluminum, zirconium and silicon on the surface of the inner coating layer in an amount of from 1 to 50 parts by weight per 100 parts by weight of the solid base.

Abstract: The invention provides a polycondensation catalyst for producing polyester by an esterification reaction or a transesterification reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, the polycondensation catalyst being obtained by hydrolyzing a water soluble titanium compound in the absence of a water soluble alkali in an aqueous slurry in which particles of a solid base are dispersed thereby to form on the surface of the particles of the solid base a coat layer of titanic acid in a content of from 0.1 to 50 parts by weight in terms of TiO2 per 100 parts by weight of the solid base. The invention further provides a method for producing the polycondensation catalyst, and polyester obtained using the polycondensation catalyst.

Abstract: The invention provides a polycondensation catalyst for producing polyester by an esterification reaction or a transesterification reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, wherein the polycondensation catalyst comprises particles of a solid base having on the surfaces an inner coating layer of titanic acid in an amount of from 0.1 to 50 parts by weight in terms of TiO2 per 100 parts by weight of the solid base, and an outer coating layer either of an oxide of at least one element selected from aluminum, zirconium and silicon, or of a composite oxide of at least two elements selected from aluminum, zirconium and silicon on the surface of the inner coating layer in an amount of from 1 to 50 parts by weight per 100 parts by weight of the solid base.

Abstract: The invention provides a polycondensation catalyst for producing polyester by an esterification reaction or a transesterification reaction between a dicarboxylic acid or an ester-forming derivative thereof and a glycol, the polycondensation catalyst being obtained by hydrolyzing a water soluble titanium compound in the absence of a water soluble alkali in an aqueous slurry in which particles of a solid base are dispersed thereby to form on the surface of the particles of the solid base a coat layer of titanic acid in a content of from 0.1 to 50 parts by weight in terms of TiO2 per 100 parts by weight of the solid base. The invention further provides a method for producing such a polycondensation catalyst, and polyester obtained using such a polycondensation catalyst.