PREPARATION METHOD OF DIPHENYL METHANE-BASED DIISOCYANATE (MDI) FRACTION CONTAINING 95 OR MORE OF BINUCLEAR METHYLENE DIPHENYL DIISOCYANATE, PREPARATION METHOD OF DIPHENYL METHANE DIISOCYANATE BLEND, AND PREPARATION METHOD OF POLYMER USING THE FRACTION AND THE BLEND

摘要

PURPOSE: Provided are a method for preparing a diphenyl methane-based diisocyanate (MDI) fraction containing 95 wt% or more of binuclear methylene diphenyl diisocyanate, a method for preparing a diphenyl methane diisocyanate blend by using the fraction, and a method for preparing a polymer by using the fraction and/or the blend, to reduce the content of 2,2'-MDI in blend, thereby improving reactivity and reducing the content of residual monomers and to reduce the content of solvents, phenyl isocyanate and phosgene remarkably. CONSTITUTION: The diphenyl methane-based diisocyanate fraction containing 95 wt% or more of binuclear methylene diphenyl diisocyanate is prepared by reacting aniline and formaldehyde in the presence of an acid catalyst to prepare diphenyl methane-based diamine containing binuclear methylene diphenyl diamine and polyamine; phosgenating the diphenyl methane-based diamine containing binuclear methylene diphenyl diamine and polyamine to prepare coarse diisocyanate and polyisocyanate; and separating a fraction containing 90 wt% or more of binuclear methylene diphenyl diisocyanate containing at least 60 wt% of 4,4'-MDI, 4-35 wt% of 2,4'-MDI and 0.01-10 wt% of 2,2'-MDI and 20 ppm or less of phenyl isocyanate from the coarse diisocyanate and polyisocyanate.