| 摘要 |
<p>Stable hydroxyl terminated urethane polymer gel dispersions adapted for use in the production of non-penetrating urethane polymer coatings are composed of a blend of (1) a dispersion of a hydroxyl-terminated urethane polymer gel of OH No. 30-40 and viscosity lower than D on the Gardner-Holdt scale at 20-25% non-volatiles, in a solvent free from active hydrogen containing groups and (2) a dispersion of a hydroxyl terminated urethane polymer gel of OH No. 30-40 and viscosity above H on the Gardner-Holdt scale at 20-25% non-volatiles, in a solvent free from active hydrogen-containing groups, the viscosity of the blend being within the range D to H. The urethane polymer may be the reaction product of an organic polyisocyanate with a polyol of M.W. 750-3000 which is the condensation product of an alkylene oxide of 2-5 C with an organic trihydroxy compound. Alternatively the polyol may be a vegetable oil, e.g. castor oil. The blend may be prepared by first forming the two polyurethane components one having a viscosity lower than D, the other a viscosity above H, in the presence of a catalyst and then blending the two dispersions to obtain a dispersion of viscosity in the range D to H.</p> |
