Foams based on thermoplastic polyurethanes

A process for production of expanded thermoplastic polyurethane foam beads, comprising:

• (i) melting a thermoplastic polyurethane whose Shore hardness is from A 44 to A78, together with from 0.1 to 40% by weight, based on the total weight of pellets, of a blowing agent, if appropriate with additives, in an extruder, and (ii) pelletizing the melt without devices which inhibit foaming to produce expanded thermoplastic polyurethane foam beads;
• wherein
• the blowing agent is a volatile organic compound having a boiling point from −25 to 150° C. at 1013 mbar selected from the group consisting of hexane, heptane, octane, an alcohol, a ketone, an ester, an ether and a carbonate,
• the thermoplastic polyurethane comprises a polytetralhydrofuran of a molar mass of from 600 g/mol to 2500 g/mol, and
• the thermoplastic polyurethane exhibits a melting range, measured by DSC using a heating rate of 20 K/min, that starts below 130° C., and the thermoplastic polyurethane has at most a melt flow rate of 250 g/10 min at 100° C. with an applied weight of 21.6 kg to DIN EN ISO 1133.