Polymer composition comprising a thermoplastic polyester

A process for improving the physical or chemical properties of a polymer, comprising the following steps of:

• provision of a polymer chosen from aromatic polyesters, aliphatic polyesters, polyester ethers, polyamides, polycarbonates, polyether block amides and polyurethanes,
• blending of said polymer with a thermoplastic polyester comprising at least one 1,4:3,6-dianhydrohexitol unit (A), at least one alicyclic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), at least one terephthalic acid unit (C), wherein the (A)/[(A)+(B)] ratio is at least 0.05 and at most 0.75, said polyester not containing any aliphatic non-cyclic diol units or comprising a molar amount of aliphatic non-cyclic diol units, relative to all the monomer units of the polyester, of less than 5%, and the reduced solution viscosity (25° C.;
• phenol (50% m):ortho-dichlorobenzene (50% m);
• 5 g/l of polyester) of said polyester is greater than 70 ml/g, and
• recovery of said blend.