| abstract |
The invention relates to a method for producing viscoelastic polyurethane foams having a density of 100 g/dm3 to 300 g/dm3, wherein (a) polyisocyanate is mixed with (b) polymeric compounds having groups reactive toward isocyanates, (c) optionally chain-extending and/or cross-linking agent, (d) catalyst, (e) blowing agent, containing water, and optionally (f) additives at an isocyanate index of 50 to 95 to form a reaction mixture, the reaction mixture is introduced into a mold and reacted to form soft polyurethane foam, wherein the polyisocyanate (a) can be obtained by mixing 4,4'-MDI and oligomers of propylene oxide having 2 to 8 propylene oxide units, optionally carbodiimide of 4,4'-MDI and optionally higher-ring homologs of MDI and wherein the polymeric compounds having groups reactive toward isocyanates (b) contain at least one polyalkylene oxide having a hydroxyl value of 20 to 50 mg KOH/g, proceeding from a 3-functional starter molecule and an ethylene oxide fraction, with respect to the content of alkylene oxide, of 0 to 10 wt%, at least one polyalkylene oxide having a hydroxyl value of 20 to 50 mg KOH/g, proceeding from a difunctional starter molecule and an ethylene oxide fraction, with respect to the content of alkylene oxide, of 0 to 10 wt%, at least one polyalkylene oxide having a hydroxyl value of 400 to 800 mg KOH/g, proceeding from a 2- to 4-functional starter molecule and an ethylene oxide fraction, with respect to the content of alkylene oxide, of 80 to 100 wt% and 0 to 30 wt% of a further polyalkylene oxide. The invention further relates to a polyurethane foam that can be obtained in accordance with such a method and to the use of such a polyurethane foam in the production of mattresses or paddings for furniture or as insulation, for example in the environment of motors, such as internal combustion engines. |