High impact strength molding compositions based on polyalkylene terephthalates

Claim 1

A process for substantially increasing the impact strength of molding compositions of a synthetic resin mixture containing predominantly a polyalkylene terephthalate with a minor amount of an impact strength modifier, the synthetic resin mixture containing: A. 70-95% or 60-97% by weight of a polyethylene terephthalate, polypropylene terephthalate or polybutylene terephthalate having a viscosity number (J) of about 55-100 cc/g and B. when A is 70-95%, 5-30% by weight of an elasticizing acrylate graft copolymer, an α-olefin copolymer or polyether amide, or when A is 60-97%, 3-40% of a polyether ester amide, the latter being obtained by condensation of at least one omega-aminocarboxylic acid or lactam of at least 10 carbon atoms with a polyalkylene glycol having a number average molecular weight of 400-6,000 and at least one dicarboxylic acid, said process comprising maintaining the synthetic resin mixture in the solid form at temperatures of 15°-60° C. below the melting point of the pure component A in an inert gas atmosphere for a time sufficient to effect recondensation of the synthetic resin mixture and to achieve a substantially higher impact strength than the non-recondensed synthetic resin mixture.