Polyurethane elastomers which exhibit improved stability to hydrolysis

Polyurethane elastomers comprising the product of the reaction of

• a) at least one diisocyanate and/or polyisocyanate with
• b) at least one polyester polyol having an OH number of 20 to 280 and a functionality of 1 to 3, and optionally with
• c) one or more polyether polyol or polyether ester polyol each having an OH number of 10 to 149 and a functionality of 2 to 8, and optionally with
• d) one or more members selected from the group consisting of chain extenders having molecular weights lower than 800 and crosslinking agents with having OH numbers of 150 to 1870. in the presence of
• e) at least one amine catalyst,
• f) at least one esters of monobasic carboxylic acid or polybasic carboxylic acids, the (first) dissociation constant (pK) of which is 0.5 to 4, and optionally
• g) a foaming agent, and optionally
• h) one or more conventional additives,
• wherein the maximum ratio of the number of ester groups in said f) to the number of amino groups in e) is 1.0.