METHOD FOR PRODUCING RIGID POLYURETHANE FOAMS

摘要

The invention relates to a method for producing rigid polyurethane foams by reacting a) polyisocyanates with b) compounds with at least two hydrogen atoms that are reactive with isocyanate groups, in the presence of c) foaming agents. The inventive method is characterized by using, as the compounds with at least two hydrogen atoms that are reactive with isocyanate groups b), a mixture b1) from a polyether alcohol having a functionality of 4 and a hydroxyl number of 380 to 450 mg KOH/g and a viscosity of more than 12000 mPa s, producible by addition of ethylene oxide and/or propylene oxide to TDA, b2) a polyether alcohol having a functionality of 5 to 7.5 and a hydroxyl number of 380 to 480 mg KOH/g, producible by addition of propylene oxide to sucrose and/or sorbite, b3) a polyether alcohol having a functionality of 2 to 4 and a hydroxyl number of 140 to 250 mg KOH/g, producible by addition of ethylene oxide and propylene oxide to TDA or of propylene oxide to alcohols having a functionality of 2, 3 or 4, or to amines or castor oil derivatives different from TDA.