PREPARATION METHOD OF POLYISOCYANATE HAVING DIPHENYLMETHANE GROUP HAVING REDUCED COLOR VALUE

摘要

PURPOSE: A method for preparing a diphenylmethane-based polyamine and a method for preparing a diphenylmethane-based polyisocyanate by using the polyamine prepared by the method are provided, to product a diphenylmethane-based polyisocyanate having a low color value by simple process. CONSTITUTION: The diphenylmethane-based polyamine is prepared by reacting aniline and formaldehyde in the presence of an acid catalyst to prepare a polyamine; and neutralizing the polyamine with a base, wherein at least one kind of alcohol is present during and/or after the neutralization and the molar ratio of the alcohol to the formaldehyde is 0.02:1 or more. Preferably the base is a sodium hydroxide aqueous solution. The diphenylmethane-based polyisocyanate is prepared by phosgenation of the polyamine.