Process for improving the flow of properties of polymer melts

A process for improving the flow properties of a melt containing a thermoplastic polymer, which comprises:

• incorporating 0.005% to 0.5% by weight, relative to the weight of the thermoplastic polymer, of one or more comb or comb block copolymers into said thermoplastic polymer prior to or during melt processing and
• melt processing the resultant mixture, thereby
• postponing an appearance of melt fracture to higher shear rates,
• wherein the one or more comb or comb block copolymers are prepared in a first step, which comprises:
• a) free radical polymerizing a C1-C10 alkyl ester of acrylic or methacrylic acid and optionally one or more monomers without an ester bond;
• and in a second step
• b) modifying in a polymer analogous transesterification reaction with a primary or secondary alcohol to form the comb or comb block copolymer.