Abstract: Cellulose derivatives such as cellulose nitrate, cellulose acetate, cellulose acetate butyrate or ethyl cellulose may be cross-linked with a synthetic film-forming resin such as acrylic resin, alkyd resin, epoxy resin, aminoplast resin or mixtures of these resins by first reacting said cellulose derivative with a polyisocyanate compound to give an addition-reaction product containing free isocyanate groups, then reacting the resulting product with said film-forming resin. The resulting cross-linked hybrid polymers exhibit remarkably advantageous properties as a film-forming component for use in lacquer type coating compositions.