Method for preparing biuret polyisocyanate

A method for continuously preparing biuret polyisocyanate, comprising the following steps:

• a) a mixed solution of a diisocyanate and a catalyst, and water vapour, in an aerosol form, are continuously reacted in a first reactor;
• wherein the continuous phase of the aerosol is the water vapour, the dispersed phase is the mixed solution of the diisocyanate and the catalyst, and the droplet size of the dispersed phase in the aerosol in step a) is 0.01-50 μm;
• b) the product obtained in step a) is brought into a second reactor for a further reaction;
• a tail gas from the second reactor is condensed and refluxed, and the non-condensable gas is brought into a tail gas treatment system;
• c) the reaction liquid obtained in step b) is further reacted in a third reactor;
• and
• d) a separation of the reaction liquid obtained in step c) is performed for removing monomers, so as to obtain biuret polyisocyanate.