| 摘要 |
Improvements in polymer/polyol compositions which are convertible by reaction with polyisocyanates to polyurethanes which are pigmented to a medium to dark color and which inherently chalk upon exposure to weather and wherein the polymer of the polymer/polyol composition is dispersed in the polyol thereof and is formed from one or more polymerizable ethylenically unsaturated monomers. The improvement provides to said polyurethanes resistance to chalking on exposure to weather and in one embodiment comprises the presence, in the polymer/polylol compositions used to make the polyurethanes, of a metallocene from the class consisting of ferrocene, ferrocene derivatives, cobaltocene and nickelocene in an amount effective to provide chalk resistance. Optionally, the metallocene can be present in the polyisocyanate composition instead of the polymer/polyol composition. Improved dark colored polyurethanes are made by reacting a mixture comprising (a) a polymer/polyol composition and (b) an organic polyisocyanate in the presence of (c) a catalyst for the reaction of (a) and (b), (d) a metallocene, preferably ferrocene, or a ferrocene polymer and (a) a medium to dark pigment to produce the polyurethane. |
