Polyurethane Microspheres

Free flowing polyurethane microspheres useful as components for blending in an extruder with other polymers, having a particle size distribution which ranges between about 1 to about 100 microns, said microspheres being produced by a process, which comprises:

• preparing a solution of a diol or a polyol having a molecular weight in the range of from about 200 to about 2000, a crosslinker and a catalyst selected from amino or organometallic compounds, dispersing this solution in a dilute solution of a stabilizer which comprises a block copolymer having the general formula ›A!.sub.n -›B!.sub.m where A and B are chemically and compositionally dissimilar segments and n and m segments are between about 30 to about 115 and about 10 to about 60 units, respectively, such that the sum of n and m does not exceed 175 units, in an aliphatic hydrocarbon;
• adding an isocyanate dropwise to this dispersion;
• agitating the mixture at a speed of about 100 to about 1200 revolutions per minute and at a temperature between about 30.degree. to about 55.degree. C. to permit the formation of polyurethane microspheres;
• separating these microspheres by filtration;
• washing with a lower aliphatic hydrocarbon;
• and, drying the microspheres under vacuum.