The Study On Synthesis Of 1,6-hexamethylenediisocyanate

1,6-hexamethylenediisocyanate(HDI) is widely used as a kind of chemical materials. At present, large industrial scale production of HDI has been accomplished by the phosgenation of the diamines, using phosgene. Phosgene is notoriously difficult to manage industrially due to its high toxicity, corrosivity and severely corrosive hydrochloric acid as a byproduct. The phosgene-free routes have been developed and become the focus because of the environment problem.We have developed a substitute phosgene-free route using CO₂ as the carbonylation regent. The technological process has many distinct advantages, such as economical, simple, and elimination the pollution in raw materials. The clean process of HDI synthesis mainly has two stages. As for the first stage, ammonium carbamate saltis prepared by reacting hexa- methylene diamine with CO₂ and triethylamine in the presence of acetonitrile. Ammonium carbamate saltis and SBA dehydrate .The process of ammonium carbamate salt preparation Firstly, the reaction equipment has been devised according to the results of the previous experiments. And then, the optimum conditions: reaction temperature -5℃, reaction time 30min, n(triethylamine):n(HDA)= 3:1. The influences of reaction temperature, reaction time and the proportion of the catalyst on the efficiency were discussed, and the temperature is major factor.The process of HDI preparation Firstly, the reaction equipment has been devised according to the results of the previous experiments. And then, the optimum conditions: reaction temperature -10℃, reaction time60min, n(SBA):n(HDA)= 2:1. The influences of reaction temperature,reaction time and the proportion of the catalyst on the efficiency were discussed, and the temperature is major factor.HDI, intermediate product and by-product was verified by IR, the refractive index and GC. This route has distinct advantages, such as moderate conditions, easy to operate and post-processing convenience.