New rigid polyurethane foams (I), having a flame height of less than 15 cm according to EN-ISO 11925-2, are obtained by reaction of (a) polyisocyanates, (b) compounds containing hydrogen atoms reactive with isocyanate groups, containing at least one amine-initiated polyether polyol, (c) a hydrocarbon-containing blowing agent, (d) silicone-free foam stabilizers and (e) flame retardants in an amount of 12-35% based on the total weight of (b) to (e). Independent claims are included for: (a) the preparation of (I) by reacting components (a) to (e); and (b) the use of (d) for the preparation of rigid polyurethane foams, having a flame height of less than 15 cm according to EN-ISO 11925-2 and containing 12-35% flame retardant based on the overall weight of the polyol component (preferably prepared using a hydrocarbon blowing agent).
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