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.)

1. A process for preparing methylene diphenylene diisocyanate and optionally a mixture of methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate, the process comprising the steps of:

a) providing a fraction (142) comprising methylene diphenylene diisocyanate and minor components, the mass proportion of which methylene diphenylene diisocyanate, based on its total mass and determined by gas chromatography, is greater than 98.0%, which is optionally carried out by a.1)

α.1) separating methylene diphenylene diisocyanate and minor components from a fraction (100) comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate to obtain

(i) Polymethylene polyphenylene polyisocyanate-rich mixture of methylenediphenylene diisocyanate and polymethylene polyphenylene polyisocyanate (141) and

(ii) a fraction (142) comprising methylene diphenylene diisocyanate and minor components, the mass proportion of methylene diphenylene diisocyanate being greater than 98.0% based on the total mass thereof and determined by gas chromatography;

beta) is purified by distillation and/or crystallization in two or more, preferably 3 to 10, more preferably 4 to 8, sub-steps (a, b, … …), including isomerizing the fraction (142) comprising methylenediphenylene diisocyanate and minor components to obtain at least

(i) Two or more, preferably 2 to 4, more preferably 2 to 3, pure methylene diphenylene diisocyanate fractions (140-1, 140-2, … …) each having a mass proportion of 99.9% or more, based on their total mass and determined by chromatography, and

(ii) a minor component fraction (150) having a mass proportion of methylene diphenylene diisocyanate, based on the total mass thereof and determined by chromatography, of from 20.0% to 98.0%,

the method is characterized in that: subjecting the minor fraction (150) obtained in step β)

Recycled to one or more of the substeps (a, b, … …) of step β), in which no fraction of pure methylene diphenylene diisocyanate (140-1, 140-2, … …) from step β) is obtained as distillate or crystals,

and/or, if step α.1) is carried out, recycled to step α.1).

2. The method of claim 1, comprising step α.1).

3. The process according to claim 2, wherein the fraction (100) comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate is obtained by:

A) reacting a mixture (2) of methylenediphenylenediamine and polymethylene polyphenylene polyamine with phosgene (3) in the presence of an organic solvent (4), wherein a stoichiometric excess of phosgene (3) based on all primary amino groups present is used, to obtain a liquid stream (60) comprising methylenediphenylene diisocyanate and polymethylene polyphenylene polyisocyanate and secondary components and a gaseous stream (70) comprising hydrogen chloride and phosgene;

B) post-treating at least the liquid stream (60) comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate and minor components, which comprises:

-prepurification to isolate a first portion of said secondary components to obtain a liquid fraction (100) depleted of said secondary components and comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate.

4. The process according to claim 3, wherein the organic solvent (4) used in step A) is selected from the group consisting of monochlorobenzene, dichlorobenzene, dioxane, toluene, xylene, dichloromethane, perchloroethylene, trichlorofluoromethane and butyl acetate.

5. The method of claim 3 or 4, wherein the pre-purification comprises:

(1) separating a gas stream (90) comprising hydrogen chloride and phosgene from a stream (60) comprising methylene diphenylene diisocyanate, polymethylene polyphenylene polyisocyanate and minor components;

(2) separating a gas stream (110) comprising the organic solvent (4) from the liquid phase remaining after the separation of the gas stream (90) comprising hydrogen chloride and phosgene in step (1) to obtain a liquid fraction (100) depleted of secondary components and comprising methylene diphenylene diisocyanate and polymethylene polyphenylene polyisocyanate;

and optionally

(3) The gas stream (110) comprising the organic solvent (4) is separated into a liquid stream (120) comprising the organic solvent (4) and a gas stream (130) comprising phosgene.

6. The process as claimed in any of claims 3 to 5, wherein in step B) the gaseous stream (70) comprising hydrogen chloride and phosgene is also subjected to a work-up, wherein the work-up comprises:

separating phosgene from a gaseous stream (70) comprising hydrogen chloride and phosgene, in particular after combining with a gas stream (90) comprising hydrogen chloride and phosgene, to obtain a gas stream (170) comprising hydrogen chloride, wherein the gas stream (130) comprising phosgene, if present, is also subjected to the phosgene separation step;

and optionally a further step

Separating hydrogen chloride from the gas stream (170) comprising hydrogen chloride.

7. The process according to any one of claims 3 to 6, wherein step β) is carried out by distillation.

8. The process as claimed in claim 7, wherein step β) comprises 4 to 8 substeps, wherein each substep corresponds to a distillation in a distillation column without dividing walls, wherein the first pure methylene diphenylene diisocyanate fraction (140-1) and the second pure methylene diphenylene diisocyanate fraction (140-2) are each obtained as distillate in different distillation columns, wherein the minor component fraction (150) is obtained as distillate in a distillation column different from the distillation column used for obtaining the first and second pure methylene diphenylene diisocyanate fractions, wherein the third pure methylene diphenylene diisocyanate fraction (140-3) is obtained as bottom product in this distillation column.

9. The process as claimed in claim 8, wherein the minor component fraction (150) is fed to a feed of a distillation column in which the minor component fraction (150) has been obtained.

10. The process of claim 7, wherein step β) comprises two or more substeps, wherein at least one substep is carried out in a divided wall column.

11. The process as claimed in claim 10, wherein in step β), the stream (142) obtained in step α.1) comprising methylene diphenylene diisocyanate and minor components is introduced into a dividing wall column, two prepurified methylene diphenylene diisocyanate fractions (140-11, 140-22) are taken off from the dividing wall column in liquid form as side streams, and an overhead stream comprising minor components and methylene diphenylene diisocyanate is taken off from the dividing wall column,

wherein the prepurified methylene diphenylene diisocyanate fraction (140-11, 140-22, … …) is subjected to a fine purification in a further distillation stage to produce a first and a second pure methylene diphenylene diisocyanate fraction (140-1, 140-2),

wherein an overhead stream comprising the minor components and methylene diphenylene diisocyanate from a dividing wall column is distilled in a distillation column, which may optionally be designed as a side draw column with or without dividing walls, to obtain a minor component fraction (150) as an overhead stream, a third pure methylene diphenylene diisocyanate fraction (140-3) as a bottom stream and optionally a fourth pure methylene diphenylene diisocyanate fraction (140-4) as a side stream,

wherein the minor component fraction (150) is recycled to step α.1) or to the dividing wall column from step β).

12. A process as claimed in any of claims 1 to 6, wherein step β) comprises at least one substep in which crystallization is carried out, wherein the crystals obtained in the crystallization are a fraction of pure methylene diphenylene diisocyanate or can be converted into a fraction of pure methylene diphenylene diisocyanate by further purification.

13. The process as claimed in claim 12, wherein the mother liquor obtained in the at least one sub-step in which the crystallization is carried out is distilled in at least two further sub-steps, wherein at least one further fraction of pure methylene diphenylene diisocyanate and a fraction of minor components (150) are obtained.

14. The process of claim 13, wherein the mother liquor is distilled in three further substeps, wherein two pure methylene diphenylene diisocyanate fractions are obtained.

Example (b):

the analysis method comprises the following steps:

viscosity: measured by a falling ball viscometer or a Brookfield viscometer (rotational viscometer).

NCO value: reacted with dibutylamine and back titrated with standard HCl solution for unconverted dibutylamine.

Consists of the following components: gas chromatography.

In examples 1-4, steps a) and b.i) (where the amount of MDA converted may be different) are performed as described in WO2017/050776 a1, page 35, line 2 to page 36, line 10). In example 5, the corresponding conditions were used as the basis for the process simulation.

In examples 1 to 3, the crude MDI obtained in this way as the bottom product was subjected to "polymer separation" according to step b.ii) as follows (see also fig. 2):

the crude MDI (corresponding to stream 100 in FIG. 2, flow rate 5.4t/h) was separated in a distillation column (2410) into a fraction containing MMDI and minor components (separation of minor components such as phenyl isocyanate and solvent in the previous step was not 100% successful) (crude MMDI; stream 142, 1.8t/h) and a PMDI-rich mixture of MMDI and PMDI (MDI; stream 141, 3.6 t/h). The distillation column (2410) is operated at 8 mbar_(Absolute)The operation was carried out under pressure and at a bottom temperature of 220 ℃.

In example 4, step b.ii) was carried out in a side draw column (without dividing wall; feed 63t/h) at 10 mbar_(Absolute)Pressure and a bottom temperature of 225 ℃, whereby crude MMDI (142) is withdrawn as a side stream. In example 5, the correspondingAs a basis for process simulation.

The fractions (142) containing MMDI and minor components obtained in each of examples 1-4 in this way were pumped into a storage tank (not shown in fig. 2). The fraction (142) was removed from the tank as starting material for the following examples.