PURPOSE: To provide the titled composition having low viscosity and high dispersion stability even at a high concentration, and giving a polyurethane having high rigidity, by polymerizing glycidyl methacrylate and an ethylenic unsaturated monomer such as acrylonitrile in a polyol.

CONSTITUTION: The objective composition is composed of 20W75wt% polyol (preferably polyether polyol) and 25W80wt% ethylenic unsaturated monomer dispersed in said polyol, and is produced preferably by polymerizing a mixture of 5W95wt% glycidyl methacrylate, 5W95wt% acrylonitrile and 0W60wt% other ethlenic unsaturated monomer such as methyl methacrylate, sthyrene, etc. in said polyol. An expanded or non-expanded polyurethane can be produced by reacting the above composition with a polyisocyanate, if necessary in the presence of a foaming agent, catalyst, etc.