| abstract |
A process for the production of a blocked urea group-containing polyisocyanate from a partially blocked polyisocyanate and polyamine, comprising the steps of: (i) reacting a partially blocked polyisocyanate, said polyisocyanate being made substantially free of monomeric polyisocyanate, by vacuum thin layer evaporation with a primary polyamine, secondary polyamine, or mixtures thereof, in relative proportions such that the ratio of isocyanate groups to amino groups is in the range from about 1:1 to 1.3:1, and (ii) isolating said urea group-containing polyisocyanate by wherein the vacuum boiling point of said polyisocyanate is lower than the deblocking temperature of said urea group-containing polyisocyanate. |