Polyester resins having improved rheological properties

摘要

Polyester resins particularly suitable for extrusion and injection blow-molding contain from 20 to 1000 ppm of a dianhydride of an aromatic tetracarboxylic acid and show values of die swell less than 45%.The resins are obtained by solid state polycondensation of resin having intrinsic viscosity less than 0.7 dl/g, added with a dianhydride of an aromatic tetracarboxylic acid in amount between 0.02 and less than 0.05% by weight.