Polyurethanes for "Two-Dimensional" Applications

Abstract

The unsurpassed versatility of polyurethanes is remarkably evident in the areas of two-dimensional applications. Polyurethanes are tailor-made for the wide range of rigid surface coatings, e.g., for metal, concrete and wood; for flexi ble surface coatings, e.g., for textile substrates and leather; and for a wide vari ety of adhesives. Polyurethanes give unexcelled performance in almost all of these applications. In many cases this superiority is achieved by the fact that polyurethanes are generally reactive processing polymers which can be intrin sically cross-linked to the optimal degree. This key fact can be acounted for by the versatility of the NCO group, an "energy package" of unique quality. Two- component polyurethane coatings based on aliphatic polyisocyanates are the ultimate performance standard of the industry. Special oligomers of aliphatic diisocyanates have paved the way for the ecologically most desirable high solids coatings. New aliphatic diisocyanates and their potential for coatings are dis cussed. Recently, blocked polyisocyanates have experienced significant break throughs in automotive applications and for powder coatings. Aqueous polyurethane dispersions can also be tailor-made for the whole range of two- dimensional applications. They complement the high solids and the powder polyurethane coatings, as well as the solvent-free polyurethane adhesives in the fulfillment of ecological and industrial hygiene requirements.