A molding composition of at least 50% by weight of a polyamine-polyamide copolymer obtained from 0.05 to 2.5% by weight of a polyamine having at least 4 nitrogen atoms and having a viscosity of at least 5 000 Pa•s at 250° C. and at a shear rate of 0.1 l/s, and having a viscosity ratio of at least 7 at 250° C., when the melt viscosities at shear rates of 0.1 l/s and 100 l/s are compared with one another, has high melt stiffness and is easy to cut, and performs well in blow molding.