To provide a method for producing a methylene-crosslinked polyphenylene polyisocyanate with simply and effectively suppressing discoloration of the same.
The method is to react a polyamine mixture generated by condensation reaction of aniline with formaldehyde in the presence of an acid catalyst with phosgene in the presence of an inactive solvent and produce the methylene-crosslinked polyphenylene polyisocyanate. In the method, (1) after the phosgenation reaction, remaining phosgene is removed from the obtained reaction mixture containing crude methylene-crosslinked polyphenylene polyisocyanate, subsequently (2) an OH-having aromatic compound having a carboxy group at the ortho-position and expressed by formula (I) (wherein R1, R2, R3 and R4 express each independently H or a 1-6C hydrocarbon group) is added to the crude methylene-crosslinked polyphenylene polyisocyanate and the mixture is treated by heating the same.
SHIMAMOTO MASASHI
SAEKI TAKUYA
IZUKAWA TSUKURU
JPH09100263A | 1997-04-15 | |||
JPH04253952A | 1992-09-09 | |||
JPH0782230A | 1995-03-28 | |||
JP2006057072A | 2006-03-02 |
Koji Makimura
Chihata Takahata
Toru Suzuki