Polyalkylene oxide-polysiloxane block copolymers and process for preparing same

A mixture of block copolymers having the average general formula wherein each R is a lower alkyl or phenyl radical, each R1 is a lower alkyl, vinyl or phenyl radical, a has a value from 3 to 10, b has a value from 1 to 14, and Y is derived from a mixture composed of 60 to 95 OH-equivalent per cent of (b1) a polyalkylene-glycol monoether consisting of ethylene-oxide and propylene-oxide units and having a content of 40 to 70% by wt. of oxypropylene units and a mol. wt. of from 1000 to 3000, and 5 to 40 OH-equivalent per cent of (b2) a monohydric alcohol and/or phenol, can be made by reacting together a siloxane of the above formula, except that 10 to 30 mol. per cent of the Y radicals are sulphate radicals and the remainder are Cl atoms, a polyalkyleneglycolmonoether containing 40 to 70% (wt.) of oxypropylene units, the remainder being oxyethylene units and having a mol. wt. of 1000 to 3000, and a monohydric alcohol (e.g. isopropanol or lauryl alcohol) and/or phenol. Examples describe the above preparation of the mixed copolymers. Uses.-For stabilizing polyurethane foams. In Example 1 a stabilized polyurethane foam is made by mixing together a polypropyleneoxide triol, tin octoate, water, triethylenediamine, and the siloxane-polyether stabilizer, and adding thereto trichlorofluoromethane and finally tolylene diisocyanate, and after agitation pouring the mixture into a carton.