Process for the preparation of flexible polyurethane foams with improved resistance to hydrolysis and good die cutability

The invention concerns a process for the preparation of flexible polyurethane foams by reacting organic polyisocyanates, liquid polyester polyols having hydroxyl numbers of 40 to 80 and molecular weights of 1500 to 5000, which are produced by the polycondensation of organic dicarboxylic acids with either polyol mixture A, based on the overall polyol weight consisting of: 5 to 50 percent by weight of 1,4-butanediol, 20 to 60 percent by weight of 1,5-pentanediol, 8 to 35 percent by weight of 1,6-hexanediol, 2 to 15 percent by weight of at least one triol, and 0 to 65 percent by weight of diethylene glycol, or polyol mixture B, based on the overall polyol weight consisting of: 10 to 50 percent by weight of 1,4-butanediol, 15 to 45 percent by weight of 1,6-hexanediol, 15 to 65 percent by weight of diethylene glycol, and 2 to 15 percent by weight of at least one triol, in the presence of catalysts and blowing agents as well as optionally chain extenders, auxiliaries and additives.