. "A preferred polyaddition reaction system utilizing such an admixture involves the reaction of a polyisocyanate with a mixture of oligomeric di-(aminobenzoate) esters having the formulae ##STR28## wherein each R is an alkylene radical of from two to ten, and preferably, two to four carbon atoms; and each a is an integer such that the molecular weight of the polyalkyleneeether glycols from which the" . . .