Preparation process of hexamethylene

Abstract

Hexamethylene diisocyanate (HDI) is prepared by introducing a hexamethylenediamine (HDA) solution and an equivalent amount or more of hydrogen chloride gas simultaneously into a turbulent zone in the vicinity of an agitating blade in an inert organic solvent held under agitation within a tank-shaped reactor and allowing them to undergo a successive salt-forming reaction so as to obtain a high-concentration slurry of hexamethylenediamine hydrochloride (HDA.multidot.HCl) and then reacting the slurry with phosgene. The phosgenation is effected by charging an HDA.multidot.HCl slurry of a high concentration, such as that obtained by the above process, into a tank-shaped reactor held under a pressure above the atmosphere pressure but below 5 kg/cm.sup.2 G and controlling the amount of phosgene, which is to be blown into the reactor, at a level 1-18 molar times per hour the total amount of HDA.multidot.HCl and HDI in the reaction mixture. In a preferred embodiment of the phosgenation, the phosgenation reaction is effected in a continuous two-step tank-shaped reactor while controlling the degree of conversion in the first step within 70-95%. This is a rationalized preparation process of hexamethylene diisocyanate since it requires a shorter overall phosgenation time.