Method for preparing biuret-structure polyisocyanates

摘要

A method for preparing biuret-structure polyisocyanates which comprises reacting 1,6-hexamethylenediisocyanate with water which is introduced into the reaction zone in the form of vapors in a mixture with air or an inert gas at a moisture content of said mixture of from 0.1 to 2.0 kg/kg and temperature of from 110 DEG to 130 DEG C. The reaction is carried out at a temperature ranging from 150 DEG to 170 DEG C. The polyisocyanates having biuret structure as produced by the method according to the present invention have a molecular mass of about 800, the content of isocyanate groups is as high as 23.59%. No polyurea is formed in the reaction. The process is single-staged, technologically simple and can be performed continuously.