Foamable polyurethanes

In a process for producing urethane-groups-contng. materials based on alkoxylation products of polyol cpds. polyisocyanates and (opt.) auxiliary materials, the polyol component is a propxylation product and/or ethoxylation product of polyglycerol e.g one that is obtained in technical distillation of glycerol and still contains 3 to 10 wt.% glycerol. The polyglycerol may be admixed, before alkoxylation, with polyhydric aliphatic alcohols. The propoxylation (or ethoxylation) products may have OH- number 300 to 500. 1 to 2 pbw propylene-oxide and/or ethylene oxide may be used for 1 pbw combine high dimensional stability and compressive strength with low vol. density.