PREPARATION OF STABLE DISPERSION

There is described a process for the in situ preparation of stable dispersions of polyurea and/or polyhydrazodicarboxamides in hydroxyl-containing polyethers. These products are prepared by reacting (1) organic polyisocyanates with (2) primary and/or secondary amino group-containing polyamines and/or hydrazines and/or hydrazides, in a high molecular weight polyether which has at least one hydroxyl group with the components (1), (2) and (3) being passed continuously into a continuous mixer at such a rate that the average residence time (dwell time) in the mixer is less than 10 minutes. The equivalent ratio of components (1) and (2) is between 0.8 and 1.05. The dispersions thus prepared are non-sedimenting and combine a relatively high solids content with a relatively low viscosity. The size of the dispersed particles is usually below 1 mu . Owing to these properties, they are suitable for preparing polyurethane foams.