Substituted morpholine catalyst for polyurethane foam

In a method of making a polyurethane foam wherein a polyurethane-forming long chain polyol and a polyurethane-forming organic polyisocyanate are reacted in the presence of a catalyst and a blowing agent for the polyurethane foam, the improvement comprising using as the catalyst, at least in part, an effective amount of a compound of the formula ##STR4## wherein R.sub.1 and R.sub.2 are alkyl radicals having 1 to 4 carbon atoms.