disappearance of a peak at about 2275 cm u2212 1 nco and the appearance or increase in magnitude of peaks at about 1740 1680 cm u2212 1 and about 1540 1530 cm u2212 1 corresponding to urethane frequencies was used to confirm this the product had a color value of 15 5 at the u03bb max of 569 153 parts of the polymeric violet colorant of example 3 were charged into a 3 neck flask added to this formulation was 59 parts of octadecylisocyanate and 4 parts of dibutyltin dilaurate catalyst the entire mixture was then heated to 70 80 u00b0 c for 2 6 hours or until the reaction was complete the absence disappearance of a peak at about 2275 cm u2212 1 nco and the appearance or increase in magnitude of peaks at about 1740 1680 cm u2212 1 and about 1540 1530 cm u2212 1 corresponding to urethane frequencies was used to confirm this the product had a color value of 20 at the u03bb max of 569 100 parts of the polymeric violet colorant of example 3 were charged into a 3 neck flask added to this formulation was 20 parts of tmxdi diisocyanate and 18 parts of isophorone diisocyanate available from bayer and 1 5 parts of dibutyltin dilaurate catalyst in 1 methyl 2 pyrrolidinone the entire mixture was then heated to 70 80 u00b0 c for 2 6 hours or until all the hydroxyl groups reacted completely leaving an isocyanate terminated molecule the absence disappearance of a peak at about 3600 cm u2212 1 oh and the appearance or increase in magnitude of peaks at about 2275 2235 cm u2212 1 corresponds to isocyanate frequencies was used.