the formula: R (alkylene-O) XH N- C H2) n--N H O -alkylene) z (alkylene-O) yH wherein n is a whole number from 1 to 10, alkylene means a divalent saturated aliphatic hydrocarbon radical containing 2 to 3 carbon atoms, x, y and z are whole numbers and the sum of x, y and z is from 3 to 12, at least two of the groups selected from the groups consisting of (alkylene-O) H, (alkylene-O) H and (alkyIen