. . "Another embodiment of the process according to the invention corresponds to the melt dispersion process\" disclosed in U.S. Pat. No. 3,756,992, in which isocyanate end groups of hydrophilically modified prepolymers are reacted with urea, ammonia or other suitable compounds under solvent free conditions to form acylated amines which in turn are converted into methylol groups by a reaction with form" . . .