阅读说明：本技术 制备亚甲基二亚苯基二异氰酸酯和多亚甲基多亚苯基多异氰酸酯的方法 (Process for preparing methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate ) 是由 T.克瑙夫 P.普拉滕 D.曼策尔 S.韦斯霍芬 于 2019-01-02 设计创作，主要内容包括：本发明涉及用于制备亚甲基二亚苯基二异氰酸酯和任选的亚甲基二亚苯基二异氰酸酯与多亚甲基多亚苯基多异氰酸酯的混合物的方法,其中在步骤α)中提供包含亚甲基二亚苯基二异氰酸酯和次要组分的级分(142),这任选地通过步骤α.1)进行：从包含亚甲基二亚苯基二异氰酸酯和多亚甲基多亚苯基多异氰酸酯的级分(100)中分离出亚甲基二亚苯基二异氰酸酯和次要组分,并且其中在步骤β)中在两个或更多个子步骤(a、b、……)中通过蒸馏和/或结晶使包含亚甲基二亚苯基二异氰酸酯和次要组分的级分(142)经历包括异构体分离的纯化,以获得两个或更多个纯亚甲基二亚苯基二异氰酸酯级分(140-1、140-2、……)和次要组分级分(150),其中将在步骤β)中获得的次要组分级分(150)再循环到步骤β)的子步骤中的一个或多个,在该子步骤中没有作为馏出物或结晶物获得任何来自步骤β)的纯亚甲基二亚苯基二异氰酸酯级分(140-1、140-2、……),和/或,如果进行步骤α.1)的话,再循环到步骤α.1)。(The invention relates to a method for producing methylene diphenylene diisocyanate and optionally mixtures of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanates, wherein in step a) a fraction (142) comprising methylene diphenylene diisocyanate and minor components is provided, which is optionally carried out by step a.1): separating methylene diphenylene diisocyanate and minor components from a fraction (100) comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, and wherein in step β) the fraction (142) comprising methylene diphenylene diisocyanate and minor components is subjected to a purification comprising isomer separation in two or more sub-steps (a, b, … …) by distillation and/or crystallization to obtain two or more pure methylene diphenylene diisocyanate fractions (140-1, 140-2, … …) and a minor component fraction (150), wherein the minor component fraction (150) obtained in step β) is recycled to one or more of the sub-steps of step β) in which no pure methylene diphenylene diisocyanate fraction (140-1) from step β) is obtained as distillate or crystal, 140-2, … …), and/or recycled to step α.1) if step α.1) is performed.)