Two-component water reducible polyurethane coatings

Historically, polyurethane coatings have been formulated as two-component organic solvent based systems. These polyurethane coatings provide room temperature cure characteristics as well as an excellent combination of abrasion resistance, flexibility, adhesion, chemical resistance and appearance. However, the coatings industry is under increasing pressure to reduce the environmentally undesirable emission of volatile organic compounds (VOC). One way of doing this is to replace some or all of the organic solvent with water. However, in the case of isocyanate crosslinked polyurethane coatings this is not a straightforward matter due to the fact that unmodified isocyanates are not only reactive with water, but are hydrophobic and non-dispersible.