In German Pat. No. 1,110,607, for example, it is proposed to carry out the coagulation of polyurethanes based on polyethers by exposing hygroscopic polyurethane solutions, using solvents such as dimethylformamide, for example, to the action of a stationary or circulating atmosphere which is charged with water vapor and has a relative humidity of 15% to 100% at a temperature of 10??? to 38??? C. me