| abstract |
The invention relates to a method for producing polyurethane foams, wherein compositions comprising A) isocyanate-functional prepolymers which can be obtained by reacting A1) low-molecular diisocyanates with a molar mass of 140 to 278 g/mol with A2) polyalkylene oxides with an OH functionality of two or more and A3) optionally additional isocyanate-reactive components which do not fall under A2); B) water in a quantity of at least 2 wt.%, based on the total weight of the composition; C) optionally heterocyclic 4-ring or 6-ring oligomers of low-molecular diisocyanates with a molar mass of 140 to 278 g/mol; D) optionally catalysts; E) optionally salts of weak acids, the corresponding free acids of which have a pKS value of ≥ 3.0 and ≤ 14.0 in water at 25 °C; F) optionally surfactants; G) optionally mono- or multivalent alcohols or polyols, and H) optionally hydrophilic polyisocyanates which can be obtained by reacting H1) low-molecular diisocyanates with a molar mass of 140 to 278 g/mol and/or polyisocyanates which can be produced therefrom with an isocyanate functionality of 2 to 6 with H2) mono-functional polyalkylene oxides with an OH number of 10 to 250 and a proportion of ethylene oxide of 50 to 100 mol.%, based on the total quantity of the obtained oxyalkaline groups, are provided, foamed, and cured. The isocyanate-containing components, in particular the components A, C, and H as a whole have an isocyanate content ranging from 2 to 8 wt.% and a urethane group content of 1.0 to 3.5 mol/kg, in each case based on the total quantity of the isocyanate-containing components. The invention also relates to the foams produced in this manner and to the uses thereof. |