Patent ID: 7297752
Filing Date: 2007-11-20
Classification: C08G

Abstract:
1. A method for preparing polyisocyanates by cyclodimerization of isocyanate functional groups (NCO) carried by starting monomeric isocyanates, comprising the steps of: a. providing a reaction medium comprising starting monomeric isocyanates, optionally in the presence of a solvent; b. adding to this reaction medium a (cyclo)dimerization catalyst of the superacid family having at least one highly labile hydrogen atom, the Hammett acid constant of which is less than −12; c. conducting the reaction at a temperature in the range between 0EC and 300EC, until the desired rate of conversion of between 1 and 95%, of the initial isocyanate functional groups is obtained; d. optionally inactivating or removing the reaction catalyst; e. optionally removing the unreacted monomers; and f. obtaining dimeric polyisocyanates containing at least one uretdione unit.