Polyisocyanate production method and polyisocyanate production system

Abstract

A polyisocyanate production method that can allow effective use of hydrogen chloride produced secondarily in a polyisocyanate production process, while allowing reduction of environmental burdens, and a polyisocyanate production system for performing the polyisocyanate production method. After chlorine is allowed to react with carbon monoxide to produce carbonyl chloride in a carbonyl chloride producing reactor, the carbonyl chloride produced in the carbonyl chloride producing reactor is allowed to react with polyamine in an isocyanate producing reactor to produce polyisocyanate. Then, after hydrochloric gas produced secondarily in the isocyanate producing reactor is purified in a hydrogen chloride purifying column, the purified hydrochloric gas is oxidized in a hydrogen chloride oxidizing reactor to produce chlorine. Thereafter, the chlorine thus produced is supplied to the carbonyl chloride producing reactor from a chlorine resupply line, so that it is allowed to react with carbon monoxide to produce carbonyl chloride.

1 . A polyisocyanate production system comprising,
 a carbonyl chloride production unit for producing carbonyl chloride by allowing chlorine to react with carbon monoxide,   a polyisocyanate production unit for producing polyisocyanate by allowing the carbonyl chloride produced in the carbonyl chloride production unit to react with polyamine,   a chlorine production unit for producing chlorine by oxidizing hydrogen chloride produced secondarily in the polyisocyanate production unit, and   a chlorine resupply unit for supplying the chlorine produced in the chlorine production unit to the carbonyl chloride production unit, to allow the chlorine to react with carbon monoxide in the carbonyl chloride production unit to produce carbonyl chloride.   
     
     
         2 . A polyisocyanate production system comprising,
 a polyamine production unit for producing polymethylene polyphenylene polyamine by allowing aniline to react with formaldehyde, using an acid catalyst containing hydrochloric acid,   a carbonyl chloride production unit for producing carbonyl chloride by allowing chlorine to react with carbon monoxide,   a polyisocyanate production unit for producing polymethylene polyphenylene polyisocyanate by allowing the carbonyl chloride produced in the carbonyl chloride production unit to react with polymethylene polyphenylene polyamine produced in the polyamine production unit,   a chlorine production unit for producing chlorine by oxidizing hydrogen chloride produced secondarily in the polyisocyanate production unit,   a hydrochloric acid production unit for producing hydrochloric acid by allowing at least a part of the hydrogen chloride produced secondarily in the polyisocyanate production unit and/or unoxidized hydrogen chloride in the chlorine production unit to be absorbed or mixed in water,   a chlorine resupply unit for supplying the chlorine produced in the chlorine production unit to the carbonyl chloride production unit, to allow the chlorine to react with carbon monoxide in the carbonyl chloride production unit to produce carbonyl chloride, and   a hydrochloric acid resupply unit for supplying the hydrochloric acid produced in the hydrochloric acid production unit to the polyamine production unit, to use the hydrochloric acid as the acid catalyst in the polyamine production unit.   
     
     
         3 . A polyisocyanate production system comprising,
 a carbonyl chloride production unit for producing carbonyl chloride by allowing chlorine to react with carbon monoxide,   a polyisocyanate production unit for producing tolylene diisocyanate by allowing the carbonyl chloride produced in the carbonyl chloride production unit to react with tolylene diamine,   a chlorine production unit for producing chlorine by oxidizing hydrogen chloride produced secondarily in the polyisocyanate production unit,   a hydrochloric acid production unit for producing hydrochloric acid by allowing at least a part of the hydrogen chloride produced secondarily in the polyisocyanate production unit and/or unoxidized hydrogen chloride in the chlorine production unit to be absorbed or mixed in water, and   a chlorine resupply unit for supplying the chlorine produced in the chlorine production unit to the carbonyl chloride production unit, to allow the chlorine to react with carbon monoxide in the carbonyl chloride production unit to produce carbonyl chloride.   
     
     
         4 . A polyisocyanate production system comprising,
 a nitration reactor for nitrating an aromatic raw material, using sulfuric acid and nitric acid, to introduce a nitro group in an aromatic ring of the aromatic raw material,   a polyamine producing reactor for producing polyamine by reducing the nitro group introduced in the aromatic ring of the aromatic raw material in the nitration reactor to an amino group,
 a carbonyl chloride producing reactor for producing carbonyl chloride by allowing chlorine to react with carbon monoxide, 
 a polyisocyanate producing reactor for producing polyisocyanate by allowing the carbonyl chloride produced in the carbonyl chloride producing reactor to react with the polyamine produced in the polyamine producing reactor, 
 a hydrogen chloride oxidizing reactor for oxidizing hydrogen chloride produced secondarily in the polyisocyanate producing reactor to produce a mixture of chlorine and water, 
 a dehydration column for dehydrating the mixture produced in the hydrogen chloride oxidizing reactor by putting the mixture into contact with, sulfuric acid, thereby to produce chlorine, and 
 a sulfuric acid supply line for supplying the sulfuric acid used in the dehydration column from the dehydration column to the nitration reactor so that the sulfuric acid can be reused in the nitration process. 
   
     
     
         5 . The polyisocyanate production system according to  claim 4 , which further comprises a chlorine supply line for supplying the chlorine produced in the dehydration column from the dehydration column to the carbonyl chloride producing reactor so that the chlorine is allowed to react with carbon monoxide to produce carbonyl chloride in the carbonyl chloride producing reactor.