| abstract |
In a process for producing a polyurethane foam, a mixture is discharged from a mixing head through a discharge line with: A) an isocyanate-reactive component; B) a surfactant component; C) a blowing agent component selected from the group comprising linear, branched or cyclic C 1 to C 6 hydrocarbons, linear, branched or cyclic C 1 to C 6 fluorohydrocarbons, N 2 , O 2 , argon and / or CO 2 , wherein the blowing agent C) is in the supercritical or near-critical state; and D) a polyisocyanate component. Component A) has a hydroxyl number of ≥ 100 mg KOH / g to ≤ 1000 mg KOH / g. The blowing agent component C) is at least partially in the form of an emulsion and in the discharge line means are provided with an opening or more openings to increase the flow resistance during discharge of the mixture comprising A), B), C) and D) the cross-sectional area of the opening or the sum of the cross-sectional areas of all openings is ≥ 0.1% to ≤ 99.9% of the internal cross-sectional area of the discharge line. |