Abstract: Polyesters are prepared by the reaction of a dicarboxylic acid, preferably an aromatic acid such as terephthalic acid, or an ester or ester-forming derivative thereof with a dihydroxy compound such as 1,4-butanediol in the presence of a catalyst composition comprising the combination of a titanium-based compound such as tetra-n-butyl titanate, a zirconium-based compound such as zirconium tetrakis(2,4-pentanedionate) and a phosphate-forming compound such as sodium dihydrogen phosphate. This catalyst composition affords polyesters having relatively low melt viscosities in short reaction times and does not produce an excessive level of undesirable reaction by-products.

Abstract: A catalyst composition for use in the preparation of a polyester or copolyester is disclosed. The catalyst composition comprises the combination of (a) a titanium-based compound or zirconium-based compound, and (b) a lanthanide series compound or hafnium. Various titanium-based compounds and lanthanide-based compounds are described. Moreover, in some embodiments, the catalyst composition may further comprise a phosphate-forming compound. Another aspect of this invention is an improved method for preparing a polyester, based, for example, on the two-stage process of ester interchange and polycondensation. The method is carried out in the presence of the catalyst composition described above.

Abstract: Thermoplastic polyester compositions comprising polyester resin modified by introducing perfluoropolyether blocks in the polymeric chain characterized by high crystallization rate of the melted mass and therefore by an improved processability. In particular the use of such compositions in a process for preparing molded thermoplastic articles allows working at lower temperatures of the mold and with shorter molding times. Process for preparing modified resins.