The invention relates to a process for preparing polyurethanes, which comprises reacting a) polyisocyanates with b) compounds having at least two hydrogen atoms reactive with isocyanate groups, wherein said compounds having at least two hydrogen atoms reactive with isocyanate groups b) comprise at least one polyether alcohol b1) having a functionality of 2-8 and a hydroxyl number of 200-600 mgKOH/g, obtained by addition of an alkylene oxide b1b) onto a compound having at least two hydrogen atoms reactive with alkylene oxides by using an amine b1c) as catalyst.