| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a light-colored isocyanate as a raw material for a light-colored or uncolored polyisocyanate. <P>SOLUTION: The method for producing the light-colored isocyanate is regulated as follows. The PRI (polarographically reducible impurity) value of a start amine is regulated so as to be <60 mpm (mol per million mol) in a reaction of the amine with phosgene in vapor phase. The reaction in a reaction zone is carried out at a temperature of >200°C and ≤570°C under an absolute pressure of 0.8-3 bar. The pressure in an amine- or phosgene-feeding line is regulated so as to be 20-2,000 mbar higher than the pressure in the reaction zone, and the pressure in a downstream zone of the reaction zone is regulated so as to be 10-500 mbar lower than the pressure in the reaction zone. <P>COPYRIGHT: (C)2009,JPO&INPIT |
