Process of preparing polyetherurethane foams

Claim 1

In a process wherein a polyetherurethane foam is prepared by foaming polyether polyols and polyiosocyanate in the presence of water of low-boiling propellant and a polyalkyleneglycol-polysiloxane mixed block polymer foam stabilizer, the improvement which comprises that the mixed block polymer foam stabilizer has the general formula ##STR25## wherein the mixed block polymer comprises dimethylpolysiloxane units wherein m has a value between 4 and 7, provided the number of units wherein m = 5 or 6 is at least twice the number of units wherein m = 4 and 7; n ≧ 2, R 1 is saturated alkyl of 1 - 8 carbon atoms, R 2 is saturated alkyl of 1 - 8 carbon atoms, the group POA or R 3 1 Si--, M is a divalent group which links the adjacent silicone atoms to POA, Poa corresponds to the formula (C r H 2r O) s R 3 and is composed of polyoxyethylene and polyoxypropylene units in the weight ratio of from 50 : 50 to 30 : 70, r is an integer whose specific value or range is a corollary function of the specific value of said weight ratio and R 3 is saturated alkyl of 1 - 8 carbon atoms or phenyl, and s is an integer whose specific value or range is a corollary function of the POA block mole weight, Poa has a block mole weight of from 1400 - 3000, said stabilizer prepared by adding a polydimethylsiloxanediol having the formula ##STR26## with a tertiary amine to a compound having the formula ##STR27## wherein X is a group which is reactive towards SiOH and then removing any residue of the X groups by adding compounds having the formula R 2 OH to the reaction mixture.