Abstract: Provided herein is a process for producing viscoelastic polyurethane foams having a density of from 100 g/dm3 to 300 g/dm3, in which (a) polyisocyanate is mixed with (b) polymeric compounds having groups that are reactive toward isocyanates, (d) a catalyst, and (e) a blowing agent including water at an isocyanate index of from 50 to 95 to give a reaction mixture. The reaction mixture is placed in a mold and reacted to give the flexible polyurethane foam, wherein the polyisocyanate (a) is obtainable by mixing 4,4?-MDI and oligomers of propylene oxide having from 2 to 8 propylene oxide units. The polymeric compounds (b) include at least one polyalkylene oxide having a hydroxyl number of from 20 to 50 mg KOH/g derived from a trifunctional starter molecule and a proportion of ethylene oxide, based on the content of alkylene oxide, of from 0 to 10% by weight.

Abstract: Provided herein is a process for producing viscoelastic polyurethane foams having a density of from 100 g/dm3 to 300 g/dm3, in which (a) polyisocyanate is mixed with (b) polymeric compounds having groups that are reactive toward isocyanates, (d) a catalyst, and (e) a blowing agent including water at an isocyanate index of from 50 to 95 to give a reaction mixture. The reaction mixture is placed in a mold and reacted to give the flexible polyurethane foam, wherein the polyisocyanate (a) is obtainable by mixing 4,4?-MDI and oligomers of propylene oxide having from 2 to 8 propylene oxide units. The polymeric compounds (b) include at least one polyalkylene oxide having a hydroxyl number of from 20 to 50 mg KOH/g derived from a trifunctional starter molecule and a proportion of ethylene oxide, based on the content of alkylene oxide, of from 0 to 10%.

Abstract: The present invention relates to a concrete mold liner and to molds for concrete production which produce patterned or very smooth concrete surfaces.