Patent ID: 8436064

Claim:
A predominantly open-cell rigid, stable polyurethane foam obtained from a predominantly open-cell rigid polyurethane foam-forming reaction medium which comprises: a) at least one polyol; b) at least one polyisocyanate; c) at least one catalyst; d) water; e) a predominantly open-cell rigid, stable polyurethane foam-forming amount of at least one surfactant which is a balanced, substantially linear polyether-polysiloxane ABA′ block copolymer represented by the general formula: wherein: each R 6 independently is alkyl or aryl of up to 18 carbon atoms; and, each R 7 independently is a non-hydrolyzable, hydroxyl-terminated polyether moiety of either random or blocked structure —CHR 1 CHR 2 CR 3 R 4 R 5 p O C 2 H 4 O) x (C y R 8 2y O) z H in which R 1 , R 2 , R 3 and R 4 each independently is hydrogen or a monovalent hydrocarbon group of up to 8 carbon atoms which is free of aliphatic carbon-to-carbon multiple bonds, R 5 is a divalent hydrocarbon group of up to 12 carbon atoms which is free of aliphatic carbon-to-carbon multiple bonds and p has a value of 0 or 1, each R 8 independently is hydrogen, alkyl of up to 18 carbon atoms, phenyl or alkyl-substituted phenyl in which the alkyl substituent(s) independently contain up to 4 carbon atoms, x is from 5 to 50, y is from 2 to 6, z is from 0 to 25, and x+z is from 5 to 50, and, m is from 10 to 40; and, f) optionally, at least one additional component selected from the group consisting of other polymer and/or copolymer, chain extender, crosslinker, non-aqueous blowing agent, filler, reinforcement, pigment, tint, dye, colorant, flame retardant, antioxidant, antiozonant, UV stabilizer, anti-static agent, biocide and biostat.