| 摘要 |
Cyclodimerization of polyisocyanates is carried out in the presence of a super acid catalyst at specified temperature range. The catalyst is then inactivated or eliminated and unreacted monomers are removed. A process for the preparation of polyisocyanates by cyclodimerization of the isocyanate functions of isocyanate monomers comprises: (1) providing a reaction medium containing the isocyanate monomers, optionally in the present of a solvent; (2) adding to the medium a super acid (cyclo)dimerization catalyst, maintaining the reaction medium at a temperature of 0-300 deg C (preferably 20-200 deg C) until the desired degree of transformation (1-95%, preferably 5-50% of the initial isocyanate groups) is attained; (3) inactivating or eliminating the catalyst; and (4) eliminating the unreacted monomers. An Independent claim is included for an isocyanate composition containing polyisocyanate uretdiones, prepared by the above process. |
