| 摘要 |
<p>METHODS OF FORMING POLYURETHANE PREPOLYMERS AND THE RESULTING PREPOLYMERS methods of forming liquid, low viscosity, low molecular weight, cross-linkable, stable polyurethane prepolymers which comprise: reacting polyisocyanates, and preferably aliphatic and cycloaliphatic diisocyanates, with polyhydroxy compounds or polyols, and preferably diols, triols, tetrols, and mixtures thereof: the polyols having a molecular weight of from about 62 to about 3000: the polyisocyanates and the polyols being added to the reaction mixture in an NCO/OH ratio in the range of from about 0.7:1 to about 6:1, and preferably from about 1.6.1 to about 4:15 the reaction taking place preferably in an inert, nonreactive organic solvent such as xylene; in the absence of any reaction catalysts, or in the presence of a relatively very low concentration of reaction catalysts of from about 0.00005% by weight to about 0.8% by weight, based on the total weight of the reaction mixture: at a reaction temperature of from about 0.degree. C. to about 70.degree. C., and preferably from about 0.degree. C. to about 40.degree. C., for a reaction time of from about 1/2 hour to about 12 hours: and terminating the reaction short of completion at a percent completion of reaction of from about 2% to about 95%, and preferably from about 30% to about 80%. The resulting liquid, low viscosity, low molecular weight, cross-linkable, stable polyurethane prepolymers are also included in the inventive concept.</p> |
