(Cyclo)condensation of isocyanate compounds
View Patent ↗The use of a compound comprising a nitrogenous heterocyclic group with five cyclic members including, at least two nitrogen atoms, one of the nitrogen atoms bearing a hydrogen atom to promote the opening/closing reaction of uretidione cycles in the presence of a nucleophile compound provided that, when the nitrogenous heterocyclic group is imidazole, the opening/closing reaction is not the closing reaction of the uretidione cycle in the presence of a quaternary ammonium salt.
1. A process for the preparation of a polyisocyanate composition comprising polyisocyanate trimers, and polyisocyanate dimers, in which the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.5, comprising polycondensing isocyanate monomers in the presence of a cyclotrimerization catalyst and of a nitrogenous compound composed of a five-membered heterocyclic compound having at least two nitrogen atoms in a nitrogenous cyclic compound/cyclotrimerization catalyst molar ratio of between 0.1:1 and 10:1, wherein the (cyclo)trimerization catalyst is a rare earth metal alkoxide.
2. A process for the preparation of a polyisocyanate composition comprising polyisocyanate trimers, and polyisocyanate dimers, in which the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.5, comprising polycondensing isocyanate monomers in the presence of a cyclotrimerization catalyst and of a nitrogenous compound composed of a five-membered heterocyclic compound having at least two nitrogen atoms in a nitrogenous cyclic compound/cyclotrimerization catalyst molar ratio of between 0.1:1 and 10:1, wherein the (cyclo)trimerization catalyst is a silazane salt of alkali metals, alkaline earth metals, transition metals and rare earth metals.
3. The process as claimed in claim 1 , wherein the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.6.
4. The process as claimed in claim 3 , wherein the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.75.
5. The process as claimed in claim 1 , wherein the nitrogenous cyclic compound/cyclotrimerization catalyst molar ratio is between 0.2:1 and 8:1.
6. The process as claimed in claim 2 , wherein the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.6.
7. The process as claimed in claim 6 , wherein the polyisocyanate dimers/polyisocyanate trimers molar ratio is greater than 0.75.
8. The process as claimed in claim 2 , wherein the nitrogenous cyclic compound/cyclotrimerization catalyst molar ratio is between 0.2:1 and 8:1.