Patent ID: 8026387

Claim:
A process for the preparation of a di- or polyisocyanate, comprising: reacting at least one di- or poly-amine with urea to form a di- or poly-urea and ammonia; removing the ammonia formed in the reaction of the at least one di- or polyamine with urea; separating off excess urea and minor components formed in the reaction from the formed di- or poly-urea; and thermally decomposing the di- or poly-urea from which ammonia, excess urea and minor components have been separated in a disintegrator to form a crude di- or polyisocyanate and ammonia to obtain vapors containing di- or poly-urea and ammonia; and cooling the obtained vapors to separate the di- or poly-urea from the ammonia; wherein a residence time in the thermal disintegrator for the thermal decomposition is from 0.01 to 20 seconds.