| 摘要 |
PROBLEM TO BE SOLVED: To industrially obtain the subject high-purity compound y simultaneous ly distilling out an organic solvent and p-phenylene diisocyanate obtained by cold two-stage phosgenation process under reduced pressures followed by concen trating the distillate to effect crystallization. SOLUTION: First, p-phenylenediamine (pref. <=200μm in average particle diameter) is reacted with phosgene in an organic solvent (pref. <=100-200 deg.C in boiling point such as toluene) by cold two-stage phosgenation process. Subsequently, the resultant p-phenylene diisocyanante (PPDI) and the solvent are simultaneously distilled out under reduced pressures to remove distillation residues. Finally, the distillate is concentrated pref. under reduced pressures to effect crystallization of the PPDI, which is then collected through filtration. It is preferable that, when the PPDI and the solvent are to be distilled out simultaneously, 1-10wt.% of a thermally and chemically stable compound of low volatility such as liquid paraffin be added to the PPDI and a thin film distillation is conducted using a continuous thin film evaporator. The distillation of the distilled out soluent be conducted under a reduced pressure.
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