Abstract: A polyurethane foam is obtainable from the reaction of a mixture comprising A) an isocyanate-reactive compound; B) a blowing agent selected from the group comprising linear, branched or cyclic C1-C6 hydrocarbons, linear, branched or cyclic C1-C6 (hydro)fluorocarbons, N2, O2, argon and/or CO2, wherein said blowing agent B) is in the supercritical or near-critical state; and C) a polyisocyanate. The isocyanate-reactive compound A) comprises a hydrophobic portion and a hydrophilic portion and has an average hydroxyl functionality of more than 1. The hydrophobic portion comprises a saturated or unsaturated hydrocarbonaceous chain having 6 or more carbon atoms and the hydrophilic portion comprises alkylene oxide units and/or ester units. Component A) is very preferably a sorbutan ester of the formula (II): where w+x+y+z=20.

Abstract: The invention relates to a method for increasing the efficiency of surfactants as well as to a method for suppressing lamellar mesophases in microemulsions. According to the invention, block copolymers having a water-soluble block A and a water-insoluble part B are admixed to the surfactants. The use of these substances as additives can considerably increase the efficiency of the surfactants. Moreover, the addition of the block copolymers suppresses the formation of undesired lamellar mesophases in microemulsions.