| abstract |
The invention relates to a method for producing a polyurethane foam having a density of 70 to 300 g / dm 3 and 1 to 20 cells / cm, in which a) Polyisocyanatprepolymere, obtainable by reaction of a1) Diisocyanates selected from methane diisocyanates (MDI), naphthalene diisocyanates (NDI) and mixtures thereof, with a2) apolar polyetherols, which are obtainable by alkoxylation of dihydric to tetrahydric alcohols with propylene oxide and / or butylene oxide, and / or polytetrahydrofuran, and a3) polar polyetherols which are obtainable by alkoxylation of dihydric to tetrahydric alcohols with ethylene oxide and optionally propylene oxide, the proportion of oxyethylene units, based on all oxyalkylene units, being at least 15% by weight, wherein the NCO content of the polyisocyanate prepolymer is 3 to 14%, b) propellant, containing water, and optionally c) chain extenders, d) catalyst, as well e) other auxiliaries and / or additives, mixed into a reaction mixture and allowed to react to the polyurethane foam. |