Polyester resins having improved rheological properties

摘要

Polyster resins, particularly suitable for extrusion 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 from 0.002 and 0.1 % by weight.