IMPROVED POLYESTERS FOR EXTRUSION APPLICATIONSAbstract of the DisclosureThere is disclosed a process for preparing polycarbodi-imide modified thermoplastic polyesters of increased meltstrength. These polycarbodiimide modified thermoplasticpolyesters are prepared by reacting at elevated temperaturesthermoplastic saturated polyesters which are in the molten statewith at least one polycarbodiimide such as poly(4,4'-diphenyl-methane carbodiimide) which both (a) is derived from at leastone aromatic diisocyanate which is either unsubstituted orcontains up to one methyl substituent on each aromatic ring,and (b) contains at least three carbodiimide units per polycarbo-diimide molecule.The resulting polycarbodiimide modified thermoplasticpolyester has increased melt strength and intrinsic viscosityand a decreased number of carboxylic acid end groups. Theseimproved melt strength polyesters also have improved die swellcharacteristics and are useful in extrusion applications suchas blow molding.-1-
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