| abstract |
The invention relates to a method for producing a polyurethane foam having bimodal cell size distribution, comprising the steps of: providing a mixture in a mixing head, wherein the mixture comprises: A) a component reactive in the presence of isocyanates; B) a surfactant component; C) a propellant component selected from the group comprising linear, branched, or cyclic C 1 - to C 6 -Alkane, linear, branched, or cyclical C 1 - to C 6 fluoralkane, N 2 , O 2 , Argon and/or CO 2 , wherein the propellant component C) is present in the supercritical or near-critical state; and D) a polyisocyanate component; and discharging the mixture comprising the components A, B, C, D from the mixing head, wherein the pressure present in the mixture is lowered to atmospheric pressure when discharging the mixture. |