Patent attributes
The invention relates to a process for producing rigid polyurethane foams by reactinga) polyisocyanates withb) compounds having at least two hydrogen atoms which are reactive toward isocyanate groups in the presence ofc) blowing agentswherein a mixture ofb1) a polyether alcohol which has a functionality of 4 and a hydroxyl number of from 380 to 450 mg KOH/g and a viscosity of greater than 12 000 mPa·s and can be prepared by addition of ethylene oxide and/or propylene oxide onto TDA,b2) a polyether alcohol which has a functionality of from 5 to 7.5 and a hydroxyl number of from 380 to 480 mg KOH/g and can be prepared by addition of propylene oxide onto sucrose and/or sorbitol,b3) a polyether alcohol which has a functionality of from 2 to 4 and a hydroxyl number of from 140 to 250 mg KOH/g and can be prepared by addition of ethylene oxide and propylene oxide onto TDA or of propylene oxide onto 2-, 3- or 4-functional alcohols, amines other than TDA or castor oil derivatives,is used as compounds b) having at least two hydrogen atoms which are reactive toward isocyanate groups.
