Process for coloring thermosetting resins

A process for coloring thermosetting resins, made by the polyaddition reaction in a reaction mixture of a nucleophile with an electrophile, which comprises adding to the reaction mixture before or during the polyaddition reaction a polymeric liquid reactive coloring agent suitable for incorporation in the resin with the formation of covalent bonds, said coloring agent having the formula:

• R-(polymeric constituent-X).sub.n
• wherein R is an organic dyestuff radical;
• the polymeric constituent is selected from polyalkylene oxides and copolymers of polyalkylene oxides in which the alkylene moiety of the polymeric constituent contains 2 or more carbon atoms and such polymeric constituent has a molecular weight of from about 44 to about 1500;
• and .sub.n is an integer of from 1 to about 6;
• and X is selected from --OH, --NH.sub.2 and --SH, wherein the organic dyestuff radical and polymeric constituent are selected so as to provide said coloring agent in the liquid phase at ambient conditions of temperature and pressure;
• said coloring agent being added in an amount sufficient to provide coloration of said thermosetting resin.