Eo/po block copolymers useful as stabilizers for pur foams

A polyurethane foam comprising an EO/PO block copolymer as stabilizer, wherein said polyurethane foam is obtained from an aqueous, anionically hydrophilicized polyurethane dispersion (I) by mechanical frothing and physical drying,

• wherein said EO/PO block copolymer comprises 40% to 85% by weight of ethylene oxide units based on the sum total of all ethylene oxide and propylene oxide units and has a number-average molecular weight of 1,000 to 10,000 g/mol,
• and wherein said aqueous, anionically hydrophilicized polyurethane dispersion (I) is obtained by
• A) producing isocyanate-functional prepolymers from at least
• A1) organic polyisocyanates;
• A2) polymeric polyols having number-average molecular weights in the range of from 400 to 8,000 g/mol and OH functionalities in the range of from 1.5 to 6;
• A3) optionally hydroxyl-functional compounds having molecular weights in the range of from 62 to 399 g/mol;
• and
• A4) optionally isocyanate-reactive, anionic, or potentially anionic and/or optionally nonionic hydrophilicizing agents;
• and
• B) wholly or partially reacting the free NCO groups of said isocyanate-functional prepolymers via chain extension with
• B1) amino-functional compounds having molecular weights in the range from 32 to 400 g/mol;
• and/or
• B2) with isocyanate-reactive, preferably amino-functional, anionic or potentially anionic hydrophilicizing agents,
• wherein said prepolymers are dispersed in water after B) and any potential ionic groups present are converted into their ionic form by partial or complete reaction with a neutralizing agent.