PURPOSE: To inhibit corrosion of apparatus by a mixture containing chlorine, hydrogen chloride and phosgene formed upon addition of water and to match the iodine color number of crude MDI to a level achievable by the addition of water or to reduce it.
CONSTITUTION: A crude DMA comprising diphenylmethane-diamine and polypheny-polymethylene-polyamine compound is reacted in a solvent under heating. After completion of phosgenation, the excess phosgene and the solvent are removed and further heated to give a mixture (crude MDI) of diphenylmethane-diisocyanate and polyphenyl-polymethylene-polyisocyanate. After the end of the phosgenation, a low molecular weight alkanol and/or a polyhydric alcohol are added to the phosgene-containing reaction mixture, thereby to inhibit dark coloration or discoloration.
ROORANTO MINGESU
BUERUNAA RANGAA
BERUNTO BURUFUMAN
BUORUFUGANGU HAIDAA
PEETAA KERAA
ARUNORUTO SHIYUMITSUTO
BUIRII BUAN PEE
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