To provide a method for producing a methylene-crosslinked polyphenyl polyisocyanate which achieves sufficient hue improvement while suppressing an amount of hydrogen chloride used.
The method for producing a methylene-crosslinked polyphenyl polyisocyanate includes a phosgenation reaction process for reacting a polymethylene polyphenyl polyamine with phosgene in the presence of an inert solvent; a solvent removal process for removing the inert solvent from the reaction solution obtained by the phosgenation reaction process until the concentration of the inert solvent reaches 5-35 mass%; and a hydrogen chloride introduction process for introducing hydrogen chloride to the reaction solution after the solvent removal process. The reaction temperature is kept at 60-130C in the phosgenation reaction process, the solvent removal process and the hydrogen chloride introduction process. Consequently, a sufficient hue improvement is achieved while suppressing the amount of hydrogen chloride used.
YAMADA SUSUMU
MASUDA TAKAHIRO
| JPH06234724A | 1994-08-23 | |||
| JP2004155685A | 2004-06-03 | |||
| JPS50157346A | 1975-12-19 |
Makoto Suhara
Toru Kimura
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