Flexible polyurethane foams having improved air permeability

A process for producing flexible elastic polyurethane foams in which the following components are mixed to form a reaction mixture and converted into the flexible polyurethane foam:

• a) at least one polyisocyanate, wherein at least one of the polyisocyanates present is based on diphenylmethane diisocyanate,
• b) a mixture b comprising the following components:
• b1) at least one polyether polyol having a hydroxyl value of 10 to 60 mg KOH/g, an OH functionality of more than 2, and oxyalkylene units comprising oxyethylene units in a proportion of 50 to 100% by weight based on the content of oxyalkylene units,
• b2) at least one polyether polyol having a hydroxyl value of 10 to 100 mg KOH/g, an OH functionality of more than 2, oxyalkylene units comprising oxyethylene units in a proportion of 2 to 30% by weight based on the content of oxyalkylene units, and a proportion of primary OH groups of 40 to 100% based on the total number of OH groups in component b2)
• b3) at least one polyether polyol having a hydroxyl value of 10 to 100 mg KOH/g, an OH functionality of more than 2, oxyalkylene units comprising oxyethylene units in a proportion of 0 to 30% by weight based on the content of oxyalkylene units, and a proportion of primary OH groups of greater than 0 to 30% based on the total number of OH groups m component b3)
• wherein b1) is present in an amount of 75 to 94% by weight, b2) is present in an amount of 3 to 20% by weight, and b3) is present in an amount of 3 to 20% by weight, in each case based on the total amount by weight of components b1) to b3),
• optionally b4) at least one further polyether polyol that differs from components b1) to b3), and
• optionally b5) a graft polyol based on one or more of components b1) to b3);
• wherein the amount of b4) is from 0 to 10 parts by weight and the amount of b5) is from 0 to 30 parts by weight based on 100 parts by weight of components b1) to b3),
• c) optionally chain extenders and/or crosslinkers,
• d) at least one catalyst, and
• e) at least one blowing agent comprising water, and
• f) optionally one or more additives;
• where the elastic foam has a rebound resilience measured according to DIN EN ISO 8307 of not less than 30%, and
• wherein the elastic foam exhibits an air permeability according to DIN EN ISO 7231 of at least 3.0 dm3/s.