Abstract: A polyester composition with improved hydrolytic stability is prepared by heating a molten mixture of: (A) a polyester resin; and (B) 0.05-10 wt %, based on the weight of the polyester resin, of a polymeric end-capping agent having an epoxy or amino functional group.

Abstract: Compositions based on high viscosity, high molecular weight polyesters are prepared by heating a molten mixture of: (A) a prepolymer of a polyester resin; and (B) 0.05-10 wt %, based one the weight of the polyester prepolymer, of a multifunctional polymeric chain extender having functional groups selected from the group consisting of epoxy and isocyanate.

Abstract: A composition suitable for use as a starting material for preparing a high molecular weight polyester through melt polymerization and solid state polymerization is disclosed. The composition comprises (a) a dicarboxylic acid or diester; (b) a glycol; (c) 0.1-5 mol %, relative to said component (a), of a multifunctional acid and/or a multifunctional alcohol; and (d) 0.05-5 wt %, based on the weight of the polyester, of a hindered phenolic aromatic phosphate. A process for preparing a high molecular weight polyester utilizing the above composition is also disclosed.