Aging-resistant polyurethane seal

A process for the production of polyurethane gaskets, the process comprising:

• mixing:
• (a) aliphatic polyisocyanate,
• (b) compounds having at least two groups reactive toward isocyanates,
• (c) catalysts, and
• at least one of antioxidants and light stabilizers
• to give a reaction mixture, and
• allowing completion of the reaction mixture to give the polyurethane,
• wherein the Shore A hardness of the polyurethane gasket is less than 90, the density of the polyurethane gasket is at least 850 g/L, and the compounds having at least two groups reactive toward isocyanate comprise b1) polyetherols with functionality from 2 to 4 and with hydroxy number from 20 to 100 mg KOH/g, b2) hydrophobic polyols with OH number smaller than 180 mg KOH/g and with functionality from greater than 2 to 3, b3) chain extenders, a compound b4) with molar mass smaller than 150 g/mol and with average functionality from 2 to 3 and, as groups having functionality toward isocyanate, functional groups selected from the group consisting of —NH2, —NH—, and —OH groups, wherein at least one of the functional groups is an —NH2 group or an —NH— group, and a compound b5) with molar mass from 800 to 6000 g/mol and with average functionality from 2 to 4 and, as groups having functionality toward isocyanate, functional groups selected from the group consisting of —NH2, —NH—, and —OH groups, wherein at least one of the functional group is an NH2 group.