| 摘要 |
A fractionation process of a methylene bridged polyphenylene polyisocyanate mixture obtained by phosgenating condensation product of aniline and formaldehyde is disclosed. In order to apply the above mixture to a variety of uses, the process separates the mixture into fractions by giving primary attention to the content of 4,4'- and 2,4'-isomer of diphenylmethane diisocyanate and at the same time reduces the content of impurities having acidity and hydrolyzable chlorine. |
