Process for producing flexible polyurethane foams with high comfort value and low hysteresis losses

A process for producing flexible PUR foams having a DIN EN ISO 3386-1-98 apparent density in the range of ≧63 kg/m3 to <83 kg/m3 and a DIN EN ISO 2439-1-2009 hysteresis of ≦16 comprising reacting component A comprising

• A1 at least one polyether polyol having a functionality of 2 to 6, a DIN 53240 hydroxyl number (OH number) of 9 to 112 mg KOH/g, an ethylene oxide fraction of 5 to 40 wt %, based on the sum total of alkylene oxides used,
• A2 water and/or physical blowing agents,
• A3 optionally isocyanate-reactive hydrogen compounds having an OH number of 140 mg KOH/g to 1800 mg KOH/g,
• A4 auxiliary and added-substance materials such as
• a) catalysts,
• b) surface-active added-substance materials, and
• c) pigments or flame retardants,
• wherein component A is free of polyricinoleic esters,
• with
• component B comprising
• a mixture of di- and polyisocyanates of the diphenylmethane (MDI) series (B1), optionally one or more polyether polyols (B2) having a functionality of 2 to 8, preferably of 2 to 6, a DIN 53240 OH number of ≧9 mg KOH/g to ≦56 mg KOH/g, wherein the ratio of 4,4′-MDI to 2,4′-MDI is between 1.6 and 2.7 and total monomer content is 75 to 85 wt %, based on the sum total of isocyanates used,
• wherein the flexible PUR foam is produced at an isocyanate index of 75 to 110.