RU2832614C2 - Method of producing (poly)diaminodiphenylmethane and method of producing (poly)diphenylmethane diisocyanate - Google Patents

Abstract

FIELD: chemical or physical processes.

SUBSTANCE: invention relates to the technology of producing (poly)diaminodiphenylmethane with an increased amount of trimeric oligomers of diaminodiphenylmethane, as well as a technology for producing (poly)diphenylmethane diisocyanate (pMDI) with an increased amount of trimeric components. (Poly)diaminodiphenylmethane is characterized by an oligomeric distribution with a tetramer/trimer weight ratio of not more than 0.48 with a weight ratio of trimer/dimer of not less than 0.45 and has viscosity of 50–150 mPa⋅s at 90 °C.

EFFECT: changing the molecular weight distribution and improving the quality of the polyisocyanate by reducing the content of heavy oligomers in the polyamine, reducing the content of phenylisocyanate in the desired pMDI and simplifying the technology of its production.

19 cl, 5 tbl, 10 ex

Description

Field of technology to which the invention relates

The invention relates to the field of producing (poly)diaminodiphenylmethane. In particular, the invention relates to a method for producing (poly)diaminodiphenylmethane with an increased amount of trimeric oligomers of diaminodiphenylmethane. The invention also relates to a method for producing (poly)diphenylmethane diisocyanate with an increased amount of trimeric components by reacting (poly)diaminodiphenylmethane and phosgene.

State of the art

Polyurethanes are used in many areas of industry. This is due to the possibility of varying their mechanical properties, which are ensured by using isocyanates of different structures as the raw material.

One of the most common isocyanates is diphenylmethane diisocyanate (methylene diphenyl diisocyanate, MDI). The starting component for the production of MDI is diaminodiphenylmethane, which is obtained by condensation of aniline and formaldehyde in the presence of a catalyst. As a result of the condensation of aniline and formaldehyde, a mixture of diaminodiphenylmethanes is obtained, including polydiaminodiphenylmethane (pMDA).

Polydiphenylmethane diisocyanate (pMDI) is obtained by phosgenation of pMDA. To isolate pure dimeric MDI, as well as to obtain the final pMDI with the required molecular weight distribution, the obtained MDI is distilled. In this case, a mixture of dimeric MDI and a bottoms product - pMDI - are isolated.

However, the demand for pMDI, as opposed to dimeric MDI, is showing an ever-increasing growth. Therefore, there is a need to develop methods for obtaining pMDI of the desired functionality and molecular weight without obtaining a second product - monomeric MDI.

A method is known for synthesizing polyamines and polyisocyanates of the required viscosity by adjusting the aniline-formaldehyde ratio, for example, as described in patent US 4792624 A (published 20.12.1988, DOW CHEMICAL CO [US]). The disadvantage of this method is the high content of heavy oligomers (the ratio of tetramer to trimer is more than 0.50).

At the same time, the corresponding isocyanates may have reduced reactivity. Thus, in the source [Thepolyurethanesbook, David Randall, Steve Lee, Eds., Wiley, 2002, Huntsman International LLC, Polyurethanes business] it is stated that the reactivity of internal isocyanate groups compared to terminal groups is 0.15-0.2. The share of terminal groups, for example, in the MDI trimer is 2/3 (67%), while in the MDI pentamer it is only 2/5 (40%). At the same time, heavy oligomers of pMDI may be more prone to resin formation and in increased concentrations may lead to a decrease in the shelf life of the pMDI product.

Document JP 4292560 B2 (published 08.07.2009, NIPPON POLYURETHANE IND CO LTD [JP]) describes a method for producing polyisocyanates enriched in tri- and tetrafunctional oligomers by extraction with supercritical CO ₂ . The disadvantage of this method is the need to utilize a side stream containing heavy oligomers and resins insoluble in CO ₂ .

In addition, the trimer/dimer ratio in the polyamine can be partially changed by distilling off 2,2'- and 2,4'-dimers from the polyamine (at least 80% of the sum of 2,2'- and 2,4'-) and returning them to the synthesis stage, as disclosed, for example, in document EP 1167343 A1 (published 02.01.2002, BASF AG [DE]). However, this method is not very effective in influencing the molecular weight distribution due to the low content of 2,2'- and 2,4'-dimers in the polyamine mixture (no more than 3-5%). Another disadvantage of this method is the need to use columns with a large number of separation stages (50 stages) to isolate a mixture of dimers that are virtually free of 4,4'-dimer.

A method for recycling dimers in a reaction with a reduced number of separation stages is known (WO 2017125302 A1, published 27.07.2017, BASF SE [DE]). This method is distinguished by the separation of a stream of impurities from the recycled dimers. Impurities can include aminobenzylamines, mono-methyl-MDA, formanilide, dihydroacridines. A disadvantage of this method is the need for expensive disposal of a stream containing impurities. Another disadvantage of this method is the relatively high number of separation stages (10-20), which is required to separate the purified mixture fed for recycling, containing no more than 20% of the 4,4'-dimer.

A method is known for obtaining at least 98% by weight of pure 4,4'-diisocyanatodiphenylmethane from the product of phosgenation of a mixture of polyamines obtained by condensation of aniline and formaldehyde. Pure 4,4'-diisocyanatodiphenylmethane is obtained by fractional separation of isocyanates. A disadvantage of this method is the lack of the ability to vary the composition of the isocyanate at the stage of obtaining polyamines.

An option for changing the molecular weight distribution of the polyisocyanate at the polyamine stage could be distillation of the 4,4'-dimer and its utilization in another production, for example, in the production of epoxy resins. However, this method requires the integration of two productions and is not always possible.

Thus, the development of a balanced method for obtaining PMDA and PMDI with improved oligomeric distribution remains a pressing task.

The essence of the invention

The objective of the present invention is to develop a method for producing (poly)diaminodiphenylmethane with a reduced amount of heavy oligomers and an increased amount of trimer, as well as producing (poly)diphenylmethane diisocyanate (pMDI) based on a new polyamine.

The technical result consists in changing the molecular weight distribution of the polyisocyanate at the polyamine stage, namely: in reducing the content of heavy oligomers in the polyamine (the weight ratio of the tetramer to the trimer is less than 0.48, while the weight ratio of the trimer to the sum of the dimers is 0.45 or more), while maintaining the viscosity of the polyamine of 50-150 mPa⋅s at 90°C and the resulting polyisocyanate of 150-250 mPa⋅s at 25°C, as well as in improving the quality of (poly)diphenylmethane diisocyanate.

The technical result also consists in reducing the amount of aniline in the phosgenated polyamine to a level of less than 10-20 ppm, which leads to a reduction in the content of phenyl isocyanate in the pMDI isocyanate.

An additional technical result is the absence of the need to construct a unit for the extraction of dimeric methylene phenyl diisocyanate from PMDI.

This technical problem is solved and the technical result is achieved by carrying out the condensation of aniline and formaldehyde in the presence of HCl as a catalyst with the introduction of a mixture of recycled isomeric diaminodiphenylmethanes (MDA) into the reaction mass. In this case, in one of the embodiments of the invention, the molar ratio of chlorine from HCl to the total nitrogen in the composition of aniline and recycled MDA is Cl/N=(0.2-0.4)/1.

Without wishing to limit themselves to theory, the authors of the invention believe that the formation of polyamine (pMDA) occurs as a result of the polycondensation of formaldehyde ( _CH2O ) and aniline with the release of water and the production of a mixture of primary amines with the structure of poly(methylene-2,4-phenylene-1(5)-amine) (Scheme 1).

Scheme 1 - Polycondensation of aniline and formaldehyde to produce pMDA

The molecular weight distribution of polycondensation products, including pMDA, is dictated by the Flory-Schulz distribution (equation 1):

(1),

where P ( k ) is the mole fraction of the component with the degree of polymerization k , a is an empirical parameter. The molecular weight distribution of the polyamine, starting with the dimeric diamine (M2A, and further MkA), for different a are given in Table 1, converted to the mass fractions of the content of the corresponding components of the polyamine.

Table 1. Flory-Schulz mass distribution of polyamine for different a

A 0.74 0.75 0.76 0.77 0.80 0.82 M2A 49,00 50.63 52.29 53.98 59.21 62.84 M3A 28.99 28.81 28.56 28.25 26.95 25.74 M4A 13.48 12.88 12.26 11.62 9.64 8.29 M5A 5.49 5.05 4.61 4.19 3.02 2.34 M6A 2.06 1.82 1.60 1.39 0.87 0.607 M7A 0.73 0.62 0.52 0.44 0.24 0.15 M4/M3 0.465 0.447 0.429 0.411 0.358 0.322 M3/M2 0.592 0.569 0.546 0.523 0.455 0,410

On the other hand, to obtain pMDI of suitable viscosity, for example, in the range of 150-250 mPa⋅s at 25°C, the content of dimer components is required to be no more than 52% (US 4792624 A, published 20.12.1988, DOW CHEMICAL CO [US]). With the theoretical molecular weight distribution, according to the data in Table 1, with a decrease in the proportion of the dimer component to less than 52% in the polyamine, the theoretically and practically achievable tetramer/trimer ratio will be no less than 0.465 (a=0.74), with a trimer/dimer ratio greater than 0.592. However, these values of increased trimer yield, which are quite low in terms of the tetramer/trimer ratio and quite high in terms of the trimer/dimer ratio, are not easy to obtain in practice. Thus, in document US 4792624 A, typical tetramer/trimer weight ratios are above 0.50, and trimer to dimer MDA weight ratios are below 0.5. This leads to typical trimer content in polyMDA of 23-24% or less.

Therefore, lighter polyamines are often obtained at low formaldehyde-to-aniline ratios, for example with a=0.80 or 0.82, phosgenated and part of the dimeric distribution component is distilled off already at the isocyanate synthesis stage [PERP 2016-3 - Nitrobenzene/Aniline/MDI, Nexantreport].

Detailed description of the invention

The following is a description of various aspects of the implementation of the present invention.

Thus, in one aspect, the subject of the present invention is (poly)diaminodiphenylmethane with an oligomeric distribution characterized by a tetramer/trimer ratio of no more than 0.48 with a trimer/dimer ratio of no less than 0.45, having a viscosity at 90°C of 50-150 mPa⋅s. In particular, said polyamine can have a tetramer/trimer weight ratio of no more than 0.42 and/or a trimer/dimer weight ratio of no less than 0.53.

In another aspect, the subject of the present invention is a method for producing (poly)diaminodiphenylmethane, which comprises the following steps (variant 1).

1) Mixing HCl and aniline and a mixture of recycled dimeric isomers of diaminodiphenylmethanes (MDA);

2) Reaction of a mixture of aniline, dimeric isomers of diaminodiphenylmethanes and HCl with formaldehyde at a temperature not exceeding 70°C;

3) Increasing the temperature of the reaction mass obtained in stage 2 to a temperature below or equal to 140°C and maintaining it at this temperature;

4) Neutralization of acidic compounds in the mass obtained in stage 3;

5) Washing the mass obtained in stage 4 with water;

6) Distillation of low-boiling components and aniline from the mass obtained in stage 5;

7) Distillation of a mixture of dimeric isomers of diaminodiphenylmethanes (DMA) from the mass obtained in stage 6,

characterized in that the flow of recycled mixture of dimeric isomers of diaminodiphenylmethanes (DMA), obtained in stage 7, is directed to stage 1.

In another aspect, the invention also relates to a method for producing (poly)diaminodiphenylmethane comprising the following steps (variant 2).

1) Mixing HCl and aniline with the addition of a portion of the recycled mixture of dimeric isomers of diaminodiphenylmethanes (MDA), comprising from 0 to 25 wt.% of the total amount of the added recycled mixture;

2) The reaction of a mixture of aniline and HCl with the first part of an aqueous solution of formaldehyde at a temperature _T1 of no higher than 70°C, where the first part of the aqueous solution of formaldehyde constitutes from 50 to 100% of the total amount of formaldehyde introduced into the reaction;

3) Adding the remaining portion of the recycled mixture of dimeric isomers of diaminodiphenylmethanes until the total amount of MDA reaches no more than 25 wt.% of the initial mass of aniline;

4*) in the case where at stage 2 less than 100% of the total amount of formaldehyde introduced into the reaction is introduced into the reaction, adding a second portion of formaldehyde, comprising from more than 0 and up to 50% of the total amount of formaldehyde introduced into the reaction;

4) Maintaining the reaction mass obtained in stage 3 or, in the case of stage 4*, obtained in stage 4*, at a temperature _T2 not exceeding 80°C;

5) Increasing the temperature of the reaction mass obtained in stage 4) to a temperature below or equal to 140°C and maintaining it at this temperature;

6) Neutralization of acidic compounds in the mass obtained in stage 5;

7) Washing the mass obtained in stage 6 with water;

8) Distillation of low-boiling components and aniline from the mass obtained in stage 7;

9) Distillation of the mixture of dimeric isomers of diaminodiphenylmethanes (MDA) from the mass obtained in stage 8,

characterized in that the mixture of dimeric isomers of diaminodiphenylmethanes (MDA), obtained in stage 9, is sent to stage 1 and/or 3.

In one aspect, the invention relates to (poly)diaminodiphenylmethane obtained by any of the above-described methods. The polyamine obtained by this method is characterized by an improved oligomer distribution, in particular, a tetramer/trimer weight ratio of no more than 0.48 with a trimer/dimer weight ratio of no less than 0.45, and a viscosity at 90°C of 50-150 mPa⋅s. In particular, said polyamine can have a tetramer/trimer weight ratio of no more than 0.42 and/or a trimer/dimer weight ratio of no less than 0.53.

In another aspect, the present invention relates to a method for producing (poly)diphenylmethane diisocyanate comprising the following steps:

Obtaining (poly)diaminodiphenylmethane using any of the above methods;

Phosgenation of (poly)diaminodiphenylmethane obtained in step a) to obtain (poly)diphenylmethane diisocyanate.

Below, the main aspects of the implementation of the method for producing (poly)diaminodiphenylmethane according to variant 1 are disclosed in more detail.

Step (1): Mixing aniline, MDA and HCl (preparation of a solution of partially neutralized hydrochloric amines)

The aniline fed to stage 1) is pure or recycled aniline, which may contain, among other things, up to 7% water.

Recycled MDA fed to stage 1) can be fed either as a solid, a concentrated solution in aniline, or a melt. MDA can contain aniline and different proportions of 4,4'-, 2,2'- and 2,4'- isomers, as well as impurities and homologues. Preferably, a mixture of dimeric diaminodiphenylmethanes containing at least 50% 4,4'-MDA is used as MDA.

The ratio of aniline to recycled MDA can be any convenient, but for economic reasons it usually does not exceed the mass ratio of 50% MDA to 50% aniline.

HCl is used in the form of an aqueous solution, i.e. hydrochloric acid, or gaseous hydrogen chloride. Hydrochloric acid with a concentration of 20 to 40% can be added separately or mixed with aniline and/or MDA in any suitable reaction vessel. Gaseous hydrogen chloride can be used as a dry or wet gas. Preferably, hydrochloric acid is used, preferably hydrochloric acid with a concentration of 31-38%. In a preferred embodiment of the invention, hydrochloric acid or gaseous hydrogen chloride is taken so that the molar ratio Cl/N is from 0.2 to 0.4.

Preferably, the resulting mixture of water, hydrochloric amines and neutral amines is a homogeneous solution. Also, less preferably, the resulting mixture can be used in the form of a suspension of hydrochlorides.

Step (2): reaction of a mixture of aniline, MDA and HCl with formaldehyde

Formaldehyde is used in the form of an aqueous or aqueous-methanol solution, in gaseous form or in the form of solid paraformaldehyde, preferably in the form of a 30-50% aqueous-methanol solution.

According to one embodiment of the invention, formaldehyde is used in an amount of from 0.4 to 0.7 mol per mol of starting aniline, preferably from 0.45 to 0.55 mol per mol of starting aniline.

The reaction of aniline, MDA and formaldehyde in the presence of HCl is carried out by any method known from the prior art. Examples of such methods include, but are not limited to, the methods described in: US 5053539 A (published 01.10.1991, MITSUI TOATSU CHEMICALS [JP]), US 9701617 B2 (published 11.07.2017, COVESTRO DEUTSCHLAND AG [DE]). The reaction is carried out at a temperature of no higher than 70°C, preferably at a temperature of from 20 to 70°C, for example from 30 or 40°C to 60°C.

The reaction of aniline, MDA, HCl and formaldehyde is carried out in any apparatus known from the state of the art. For example, such a reaction can be carried out in a reactor with a stirrer.

Stage (3): increasing the temperature and maintaining the reaction mass obtained in stage 2

The reaction mass obtained in stage 2 is directed to holding at elevated temperatures. The temperature increase is preferably carried out smoothly. "Smoothly" here and below means a temperature increase at a rate of no more than 5°C per minute, preferably no more than 1 degree per minute. Holding is carried out in a temperature range below or equal to 140°C, preferably in a temperature range of 80-140°C, for example 90-130°C, for the completeness of the reaction of rearrangement of the initial reaction mass containing aminals and benzylamines into a mixture of primary amines. Preferably, the rearrangement should proceed to a degree of conversion of benzylamines of 99.9% or more, according to NMR spectroscopy data. Holding can be carried out in a reactor with a stirrer, a capacitive apparatus or a tubular displacement reactor.

Stage (4): neutralization of acidic compounds

The hydrochloric acid neutralization step is generally carried out at a temperature of 60 to 140°C, preferably 90 to 130°C. Carrying out the neutralization step at a temperature below 60°C generally contributes to an increase in viscosity, while carrying out the step at a temperature above 140°C may lead to undesirable dissolution of the organic phase in the aqueous phase. In one embodiment of the invention, the neutralization step (4) may be carried out in the presence of aniline. In the case of using aniline, its amount is preferably more than 0 and up to 50%, more preferably more than 0 and up to 30% of the amount of (poly)diaminodiphenylmethane.

The neutralization stage can be carried out in any apparatus known from the prior art that ensures effective mixing and subsequent separation of the phases. Thus, according to one embodiment of the invention, neutralization is carried out in a separator or dynamic extractor, simultaneously feeding acidic (poly)diaminodiphenylmethane, a neutralizing agent and, optionally, aniline or a pre-prepared mixture of aniline and acidic (poly)diaminodiphenylmethane. According to another embodiment of the invention, flows of acidic (poly)diaminodiphenylmethane and a neutralizing agent are mixed in a mixer, sent to a capacitive apparatus (settler), and then sent for separation.

In one embodiment of the invention, the neutralization is carried out in parts, with the main part of the alkali (more than 100% of the molar equivalent of HCl) being introduced in the first part of the neutralization.

Some alkali may be added at subsequent stages to more completely neutralize the formic acid, which is chemically bound in (poly)diaminodiphenylmethane as formamides [Henri Ulrich, Chemistry and Technology of Isocyanates, John Wiley and Sons, Chichester, 1996].

Stage (5): washing the mass obtained in stage 4 with water

After neutralization, (poly)diaminodiphenylmethane is washed with water.

In the context of the present invention, the water used for washing may be, but is not limited to, distilled, deionized, demineralized, osmotic, bidistilled water or other fresh water purified from iron ions and other ionic and molecular impurities. The amount of water may be from 10 to 500 wt.%, preferably from 20 to 200 wt.% of the mixture of the neutralized mass and aniline.

The washing temperature may range from 60 to 100°C. The preferred washing temperature should be high enough to avoid emulsion formation and low enough to reduce the solubility of the polyamine components.

Stage (6): distillation of low-boiling components and aniline

The distillation of low-boiling components, which include, among others, methanol, water and aniline-water azeotrope, can be carried out in suitable equipment, such as a rectification column, a separator, at suitable temperature and pressure, with the supply of sufficient heat for evaporation. For example, the distillation temperature can be from 90 to 180 °C, and the pressure can be from atmospheric pressure to 50 mbar.

Aniline distillation is carried out after distillation of low-boiling components. For aniline distillation, the temperature of the column bottom is usually raised to a value of 180 to 250°C at a pressure in the column head of 1 to 50 mbar.

Stage (7): distillation of the mixture of dimers - diaminodiphenylmethanes

This step can be carried out in suitable equipment, such as a distillation column, typically at a column bottom temperature of 180 to 250°C and a column head pressure of 1 to 50 mbar.

The main aspects of the implementation of the method for producing (poly)diaminodiphenylmethane according to variant 2 are disclosed in more detail below.

Stage (1) of variant 2 is similar to stage (1) of variant 1 except that recycled isomeric diaminodiphenylmethanes are not added or are added in an amount from more than 0 to 25 wt.% of the total amount of recycled mixture added.

Stage (2) of variant 2 is similar to stage (2) of variant 1, except that formaldehyde can be introduced completely, i.e. in an amount of 100% of the total amount of formaldehyde introduced into the reaction, or in the form of a first part in an amount of from 50 to less than 100% of the total amount of formaldehyde introduced into the reaction.

Step (3): Addition of the remaining portion of the recycled mixture of isomeric diaminodiphenylmethanes (in case of non-addition or addition of part of the MDA in the first step)

The remaining portion of the recycled mixture of isomeric diaminodiphenylmethanes (MDA), comprising from 75 to 100 wt.%, is added to the reaction mass obtained in stage 2, such that the total amount of MDA added to the mixture reaches a value of no more than 25 wt.% of the initial mass of aniline, for example, reaches a value in an amount of from 5, or from 10, or from 15 wt.% and up to 25 or up to 20 wt.% of the initial mass of aniline.

Recycled MDA fed to stage (1) can be fed as a solid, or a concentrated solution in aniline, or a melt. MDA can contain aniline and different proportions of 4,4'-, 2,2'- and 2,4'- isomers, as well as impurities and homologues. Preferably, a mixture of dimeric diaminodiphenylmethanes containing at least 50% 4,4'-MDA is used as MDA.

Stage (4*): adding the second part of the aqueous formaldehyde solution

In the case where part of the formaldehyde is used in stage 2, i.e. less than 100% of the formaldehyde, after stage (3) the second part of the formaldehyde is added. The second part of the formaldehyde is more than 0% and up to 50% of the total amount of formaldehyde introduced into the reaction.

The addition is usually carried out at a temperature of 30 to 80°C, preferably 40 to 80°C.

Stage (4): increasing the temperature and maintaining the reaction mass obtained in stage 3 or (4*)

The reaction mass obtained in stage 3, or, in the case of stage (4*), the reaction mass obtained in stage (4*), is directed to holding at elevated temperatures. The temperature increase is preferably carried out smoothly. "Smoothly" here and below means a temperature increase of no more than 5°C per minute, preferably no more than 1 degree per minute. Holding is usually carried out at a temperature not exceeding 80°C, for example, in the temperature range from 30 to 80°C, preferably at a temperature from 40 to 70°C.

Stages (5)-(9) of option 2 are similar to stages (3)-(7) of option 1.

The (poly)diaminodiphenylmethane obtained according to the steps described above is used to produce (poly)diphenylmethane diisocyanate.

The present invention also relates to a method for producing (poly)diphenylmethane diisocyanate, comprising reacting (poly)diaminodiphenylmethane, obtained according to the present invention, and phosgene to produce (poly)diphenylmethane diisocyanate, as well as to (poly)diphenylmethane diisocyanate obtained by the described method.

(Poly)diphenylmethane diisocyanate is obtained by the interaction of (poly)diaminodiphenylmethane and phosgene in the phosgenation reaction.

According to one embodiment of the invention, phosgene is used in gaseous form. According to another embodiment of the invention, phosgene is used in dissolved form, where the solvent used is known from the prior art, specific examples of which will be described below.

According to another embodiment of the invention, phosgenation is carried out in the gas phase as described, for example, in documents EP 1509496 A1 (published 02.03.2003 BASF AG [DE]), RU 2487115 C2 (published 10.07.2013, BAYER [DE]), RU 2361856 C2 (published 20.07.2009 BAYER [DE]).

According to another embodiment of the invention, phosgenation is carried out in the presence of an inert solvent, as described, for example, in: US 5925783 A (published 20.07.1999, BAYER [DE]), WO 2010149544 A2 (published 29.12.2010, BASF SE [DE]). Hereinafter, the term "inert solvent" means a solvent that does not react with the starting and intermediate compounds, as well as with the reaction products. Examples of such solvents include, but are not limited to: chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, dioxane, dimethyl sulfoxide, xylenes, chloroethylbenzene, monochlorobiphenyl, naphthyl chloride, dialkyl phthalates or mixtures thereof. Preferably, chlorobenzene and dichlorobenzene are used as the solvent. The concentration of the polyamine in the solvent, if used, is generally from 10 to 40 wt.%, preferably from 15 to 25 wt.%.

In another embodiment of the invention, an isocyanate is used as a solvent. Such methods are described, for example, in WO 96/16028 A1 (published 30.05.1996, BAYER AG [DE]), WO 02/102763 A1 (published 27.12.2002 BASF AG [DE]).

Phosgenation is carried out in any equipment known from the prior art. Examples of such equipment include, but are not limited to: static mixers described, for example, in US 5117048 A (published 26.05.1992, BAYER AG [DE]), US 6576788 B1 (published 10.06.2003, BASF AG [DE]); dynamic mixers described, for example, in EP 2486975 B1 (published 23.09.2015, WANHUA CHEMICAL GROUP CO [CN]), US 10112892 B2 (published 30.10.2018, COVESTRO DEUTSCHLAND AG [DE]); reactors having two or more zones, described, for example, in US7851648B2 (published 14.12.2010, BASF AG [DE]), RU 2446151 C2 (published 27.03.2012, BAYER MATERIAL SCIENCE AG [DE]), WO 2012049158 A1 (published 19.04.2012, BASF SE [DE]).

The (poly)diphenylmethane diisocyanate obtained using (poly)diaminodiphenylmethane according to the invention is characterized by a viscosity of 150-250 mPa⋅s at 25°C.

Examples of the invention

Example 1. Obtaining dimer for recycling

A commercially available sample of (poly)diaminodiphenylmethane was distilled under vacuum to remove the dimeric components. The composition of the mixed dimers is given in Table 2.

Table 2
Mass concentrations of components in %* Compound Content 2,2'-MDA 0.15 2,4'-MDA 9.9 4,4'-MDA 84.4 Impurities Rest

*- according to GC-FID data

Example 2. Dosing of dimeric components for mixing with aniline. Formaldehyde/aniline molar ratio F/A 0.465. Rearrangement at 95°C (variant 1 of the method according to the present invention)

In a three-necked flask equipped with a mechanical stirrer, dropping funnel, thermocouple, and reflux condenser, create an inert atmosphere by blowing nitrogen (throughout the entire process) and load the flask with aniline (200 g). Then add 53.5 g of dimeric MDA (composition according to Table 2) to aniline and stir until the dimer is completely dissolved. Add 37.8% hydrochloric acid (77.82 g, 0.807 mol) dropwise to the resulting mixture, and the reaction mass heats up to Tр.м. = 50 °C and acquires a yellow color. Heat the reaction mass to 60 °C, then add 34.4% formalin (87.3 g, 1.076 mol) over 1 hour, preventing the reaction mass from heating above 70 °C. The mass is intensively mixed (500 rpm) with an overhead mechanical mixer.

The temperature of the reaction mass is brought to 70°C and maintained at this temperature for 1 hour. Then the reaction mass is heated to 95-98°C and stirred for 20 hours. Then 50 ml of aniline are added for better separation of the condensation products. After this, the reaction mass is neutralized with sodium hydroxide. The alkali is taken with an excess of 5 wt.% in relation to hydrochloric acid. After this, the reaction mass is transferred to a separatory funnel at 90°C and the brine phase is drained. The reaction mass is washed three times with 200 ml portions of hot water (60-80°C).

Then, the azeotropic mixture of water and aniline (fraction 1) and aniline (fraction 2) are distilled from the product in a vacuum distillation system. Then, about 53.5 g of the return fraction of dimers are distilled. 188.5 g of residual polyamine are obtained.

The synthesis conditions and properties of the distillation products for the examples are given in Table 4.

Example 3. Dosing of dimeric components after the stage of adding formaldehyde and rearrangement at 95°C. F/A 0.5 (option 2) method of the present invention)

In a four-necked flask equipped with a mechanical stirrer, thermocouple, reflux condenser, two-flow mixer, and a circulation loop with a direct condenser, an inert atmosphere is created by blowing nitrogen (throughout the entire process) and aniline (200 g) is loaded into the flask. 35.6% hydrochloric acid (82.72 g) is added dropwise to the aniline using a peristaltic pump, during which the reaction mass is heated to Tр.м. = 50 °C and acquires a yellow color. The reaction mass is cooled to 43 °C by circulation under the action of a peristaltic pump through a flexible loop with a condenser with circulating water, then 36.9% formalin (87.509 g) is added over the course of 1 hour using a second peristaltic pump, not allowing the reaction mass to heat up above 43 °C. At the same time, a flow of cooled circulating reaction mixture is fed into the central nozzle of the mixer through the circulation circuit. The circulating reaction mixture is taken from the bottom of the flask, cooled in a refrigerator and returned to the flask from above through the mixer. Both counter flows are partially mixed in the mixer. Additionally, intensive mixing with an overhead mechanical stirrer occurs. Immediately after the end of formaldehyde dosing, while maintaining a temperature of 43°C, a mixture of MDA dimers (53.76 g) is added in the form of a melt with a temperature of 100°C.

The temperature of the reaction mass is brought to 53°C and maintained at this temperature for 1 hour. The reaction mass is heated to 95-98°C and stirred for 20 hours. Then 25 ml of aniline are added for better separation of the condensation products. After this, the reaction mass is neutralized with sodium hydroxide. The alkali is taken with an excess of 5 wt.% in relation to hydrochloric acid for complete neutralization of hydrochloric acid and hydrolysis of formamides. After this, the reaction mass is transferred to a separatory funnel at 90°C and the brine phase is drained. The reaction mass is washed three times with 200 ml portions of hot water (60-80°C).

Then, the azeotropic mixture of water and aniline (1st fraction) and aniline (2nd fraction) are distilled from the product in a vacuum distillation system. Distillation is carried out in a vacuum of a membrane pump on an oil bath. At the second stage, a “trap to trap distillation” unit is assembled. The unit consists of a magnetic stirrer with heating and a thermocouple, a bath with Wood’s alloy, a 500 ml round-bottomed flask, a Wurtz packing, and a 500 ml round-bottomed two-necked receiving flask. The vapor temperature is controlled using a thermocouple. The vacuum is created using an oil vacuum pump. The residual aniline, other volatile components, and about 55 g of the return fraction of dimers are distilled. The composition of the combined fraction of dimers of Examples 2 and 3 is given in Table 3:

Table 3. Mass concentrations of components in %

Compound Content Aniline 0.16 2,2'-MDA 0.15 2,4'-MDA 5.97 4,4'-MDA 92.17 Impurities Rest

A cubic polyamine is obtained, the properties of the product are given in Table 4.

Example 4. Addition of dimers after dosing with 100% formaldehyde and rearrangement under pressure (option 2)

In a four-necked flask equipped with a magnetic stirrer, thermocouple, reflux condenser, reaction mass circulation nozzle and formalin supply system, an inert atmosphere is created by purging with nitrogen (throughout the entire process) and 200 g (2.151 mol) of pure aniline are loaded into the flask. 61.260 g (0.634 mol) of 35.6% hydrochloric acid are added dropwise to the resulting mixture using a peristaltic pump, whereupon the reaction mass is heated to T _r.m. = 50°C and acquires a yellow color.

The temperature of the reaction mass is controlled so that it is about 43 ^° C, then 91.008 g (1.118 mol) of a 36.9% aqueous-methanol solution of formaldehyde are carefully dropped over 2.5 hours using a peristaltic pump, not allowing the reaction mass to heat up above 43 °C. At the same time, a flow of the circulating reaction mixture is fed using a second peristaltic pump. Both counter flows are partially mixed in the nozzle. Then 38.057 g of MDA dimer (composition according to Table 3) are added as a melt immediately after the end of formaldehyde dosing at 43 °C. The temperature of the reaction mass is raised to 80 ^° C stepwise (in 5 °C increments) over 1 hour.

Next, the reaction mass is loaded into a BÜCHI reactor in a nitrogen atmosphere, where the reaction mixture is heated to 120°C and maintained for 2 hours after reaching this temperature.

Then 61.260 g (0.643 mol) of 42.0% NaOH solution are loaded into the reactor and neutralization is carried out at 120°C for 30 min, then the lower inorganic layer is drained. Next, the reaction mass is washed three times with 200 ml portions of hot distilled water at 90°C.

Then the recycled aniline and MDA are distilled off similarly to examples 1 and 2. The properties of the still product are given in Table 4.

Example 5. Rearrangement at 130°C (option 2)

The synthesis is carried out similarly to example 4, but the final holding of the reaction mixture is carried out at 130°C.

Example 6. Addition of dimers after dosing with 100% formaldehyde and rearrangement under pressure. F/A 0.526 (option 2)

In a four-necked flask equipped with a magnetic stirrer, thermocouple, reflux condenser, nozzle for circulating the reaction mass and a formalin supply system, an inert atmosphere is created by blowing nitrogen (throughout the entire process) and 400 g (4.295 mol) of pure aniline are loaded into the flask. 129.763 g (1.267 mol) of 35.6% hydrochloric acid are added dropwise to the resulting mixture using a peristaltic pump, while the reaction mass is heated to T _r.m. = 50°C and acquires a yellow color.

The temperature of the reaction mass is controlled so that it is about 43 ^° C, then 184.116 g (2.262 mol) of a 36.9% aqueous-methanol solution of formaldehyde are carefully dropped over 3 hours using a peristaltic pump, not allowing the reaction mass to heat up above 43 °C. At the same time, a flow of the circulating reaction mixture is fed using a second peristaltic pump. Both counter flows are partially mixed in the nozzle. Then 76.178 g of MDA dimer (composition according to Table 3) are added as a melt immediately after the end of formaldehyde dosing at 43 °C. The temperature of the reaction mass is raised to 80 °C stepwise (in 5 °C increments) over 1 hour.

Next, the reaction mass is loaded into a BÜCHI reactor in a nitrogen atmosphere, where the reaction mixture is heated to 120°C and maintained for 1 hour after reaching this temperature.

Then 131.659 g (1.356 mol) of 41.2% alkali solution are loaded into the reactor and neutralization is carried out at 120°C for 30 min, then the lower inorganic layer is drained. Next, the reaction mass is washed three times with 200 ml portions of hot distilled water.

Then the recycled aniline and MDA are distilled off similarly to examples 1 and 2. The properties of the bottom product are given in Table 4.

Example 7. Addition of dimers after dosing with 80% formaldehyde and rearrangement under pressure (option 2)

In a four-necked flask equipped with a magnetic stirrer, thermocouple, reflux condenser, formalin mixer attachment and a circuit for circulation of the reaction mass, an inert atmosphere is created by blowing nitrogen (throughout the entire process) and 400 g (4.295 mol) of aniline are loaded into the flask. 129.763 g (1.267 mol) of 35.6% hydrochloric acid are added dropwise to the resulting mixture using a peristaltic pump, whereupon the reaction mass is heated to T _r.m. = 50°C and acquires a yellow color.

By circulating through the cooling circuit, maintain the temperature of the reaction mass so that it is approximately 43°C, then carefully dose 147.293 g (1.810 mol) of 36.9% formalin (over 3 hours) using a peristaltic pump, not allowing the reaction mass to heat up above 43°C. Simultaneously, feed a flow of the circulating reaction mixture using a second peristaltic pump. Both counter flows are partially mixed in the nozzle. Then 76.178 g of MDA dimer (composition according to Table 3) are added as a melt immediately after the end of dosing the first portion of formaldehyde, at 43°C. Raise the temperature to 53°C, maintain at this temperature for 30 min and then add the remaining formalin - 36.823 g (0.452 mol).

The temperature of the reaction mass is raised to 80°C in steps (5°C step) over 1 hour, recording the heating time.

Next, the reaction mass is loaded into a BÜCHI reactor in a nitrogen atmosphere, where the reaction mixture is heated to 120°C and held for 1 hour.

Then 131.659 g (1.356 mol) of 41.2% alkali solution are loaded into the reactor and neutralization is carried out at 120°C for 30 min, then the lower inorganic layer is drained. Next, the reaction mass is washed three times with 200 ml portions of hot distilled water at 90°C.

Then the recycled aniline and MDA are distilled off similarly to examples 2 and 3. The properties of the still product are given in Table 4.

Example 8. Fractional addition of dimers and formaldehyde, and rearrangement under pressure (option 2)

A 60 l DeDietrich enamelled reactor with a coolant jacket and a stirrer is loaded with a solution of 0.762 kg MDA with the component content given in Table 5 in 20.00 kg aniline. 6.39 kg 36.1% hydrochloric acid are loaded into the reactor and the mixture is cooled to 35°C. 8.122 kg 35.5% aqueous methanol formalin are dosed, maintaining the temperature at 35°C. After this, 3.046 kg of MDA melt are dosed into the reactor. Then the reaction mass is heated to 51°C and maintained at this temperature for 1 h. After this, 1.433 kg 35.5% aqueous methanol formalin are dosed, maintaining the temperature at 51°C. Then the mixture is heated to 120°C and maintained at this temperature for 15 min. Then 3.0 kg of aniline are added to the mixture for dilution. Then 7.14 kg of 42% NaOH solution are added to the reactor and stirred at 110°C for 2 h. Then the mixture is cooled to 90°C, settled for 45 min and the lower phase is separated. The pMDA phase is washed twice with 20 kg of H ₂ O. The washed pMDA is subjected to stepwise distillation in a series of columns for distilling off water, aniline and dimeric MDA. The polyamine still has a viscosity of 103 mPa⋅s at 90°C.

Table 4. Results of product analysis by examples

Parameter Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Mass of MDA/mass of aniline 0.2675 0.2688 0,1903 0,1903 0,1904 0,1904 0,1904 Formaldehyde/aniline molar ratio 0.465 0.5 0,520 0.521 0.527 0.527 0.526 Cl/N molar ratio 0.3 0.3 0.25 0.25 0.25 0.25 0.25 Mass fractions of main products, % wt. Norm. per 100%* 4,4-MDA 47.79 54.78 50.24 49.73 52.98 44.79 44.73 2,4-MDA 3.38 3.03 2.81 3.19 2.40 2.20 2.28 M3A 27.14 25.84 26.65 27.39 24.49 27.59 27.58 M4A 12.29 9.81 11.54 11.64 10.55 13.07 12.26 M5A 5.94 4.65 5.43 5.50 5.26 6.86 6.35 M6A 2.40 1.26 2.31 1.95 2.94 3.49 5.31 M7A 0.80 0.48 0.84 0.60 1.04 1.46 1.03 M8A 0.26 0.16 0.18 0,00 0.34 0.54 0.46 Ratio of mass fractions of tetramer and trimer M4A/M3A 0.453 0.380 0.433 0.425 0.431 0.474 0.444 Ratio of mass fractions of trimer and sum of dimers M3A/M2A 0,530 0.447 0.502 0.517 0.442 0.587 0.587 Viscosity at 90°C, mPa⋅s 84.6 59.5 77.3 90.7 86.4 115 103 Aniline content, ppm 10 20 10 10 10 10 10 Mass fraction of NH groups of secondary amines,** % 0.05 0.06 0.04 0.04 0.05 0.03 0.03

* - According to HPLC data;

** - According to NMR data

When comparing the results of different examples, it can be seen that despite the lower formaldehyde-aniline ratio in Example 2 (0.465) than in Example 3 (0.5), a "lighter" amine product with a low tetramer-trimer ratio (0.38 compared to 0.45) is obtained in Example 3. The inventors believe that this is due to the method of introducing the recycled dimer in Example 3 after dosing the formaldehyde, which reduces the likelihood of the formation of heavy oligomers at the initial stages of the reaction.

In Examples 4 and 5, the formaldehyde-aniline ratio is increased to 0.52, while the mass ratio of recycled MDA to feed aniline is reduced to 0.19 compared to 0.27 in Examples 2 and 3.

In this case, the tetramer-trimer ratio increases slightly to 0.43, and the trimer-dimer ratio to 0.50-0.52.

The highest formaldehyde-to-aniline ratio is used in Examples 6-8. The tetramer-to-trimer ratio increases relatively strongly (up to 0.474) only in Example 7, with the method of dosing 80% formaldehyde before adding recycled dimers and 20% formaldehyde after dosing recycled dimers and a short soak. In this case, Example 7 yields the most viscous polyamine of the series (115 mPa⋅s at 90°C) with a dimer content of 47%. In Example 8, with dosing 20% dimers at stage 1, the M4/M3 ratio is 0.44 and the viscosity is 103 mPa⋅s at 90°C.

Example 9. Phosgenation

Phosgene (68 g, 0.68 mol) as a 20% solution in toluene (340 g of solution) is poured into a 2000 ml three-necked round-bottomed flask cooled with an ice-salt bath under slight nitrogen breathing. To the stirred solution at -2°C, a solution of the polyamine obtained according to the corresponding example (15.5 g, about 0.02 mol of amino groups) in 250 g of chlorobenzene is added dropwise over 30 min. The rate of addition is regulated so that the temperature of the reaction mass does not exceed 0-5°C, for 15 min. Then the dropping funnel is washed with another 200 g of chlorobenzene. The resulting suspension is slowly, stepwise, heated to 98°C over 2.5-3 h to separate the hydrogen chloride. The exhaust gases (hydrogen chloride, phosgene) are captured in a trap system with a 10% NaOH solution, while the solvent vapors are condensed in a reflux condenser. After the precipitate has dissolved, the system is purged with a stream of nitrogen into the solution mass at 122°C for 30 min with a reflux condenser. The solution is evaporated in a vacuum to a volume of 20 ml and the residue is heated in an oil bath in a vacuum of 0.23 mbar at 180°C for 30 min.

The product is analyzed. The results of the product analysis are presented in Table 5.

Table 5. Results of analyses of pMDI products

Source of polyamine Example 2 Example 6 Example 7 Isocyanate, viscosity, mPa⋅s at 25°C 163.5 132.6 182.3 Isocyanate, hydrol. chlorine, % 0.17 0.14 0.10 Isocyanate, NCO, % 32.5 33.2 30.9 Phenyl isocyanate, ppm 29 20 14

Example 10. Comparative

The polyamine is synthesized according to patent US 4792624 with recycling of the final polyamine. Polyamine products with a tetramer/trimer ratio of 0.52 and a trimer/dimer ratio of 0.46 are obtained.

It follows from the presented examples that the use of the recycle of diaminodiphenylmethane dimers according to the present invention instead of the recycle of the final polyamine according to the known prior art (US 4,792,624) makes it possible to significantly reduce the tetramer/trimer weight ratio from 0.52 to approximately 0.38-0.48, and also to maintain the trimer/dimer weight ratio at a level above 0.45, i.e. to significantly increase the proportion of the most valuable trimer oligomers in the final polyamine. In turn, the use of such polyamines enriched with trimer oligomers for the synthesis of polyisocyanates by phosgenation makes it possible to obtain polyisocyanates with controlled viscosity, as well as a reduced content of phenyl isocyanate, which is illustrated by example 9.

Claims (38)

1. (Poly)diaminodiphenylmethane with an oligomeric distribution, characterized by a tetramer/trimer weight ratio of no more than 0.48 with a trimer/dimer weight ratio of at least 0.45, having a viscosity at 90°C of 50-150 mPa⋅s. 2. (Poly)diaminodiphenylmethane according to claim 1, having an oligomeric distribution, characterized by a tetramer/trimer weight ratio of no more than 0.42. 3. (Poly)diaminodiphenylmethane according to claim 1, having an oligomeric distribution characterized by a trimer/dimer weight ratio of at least 0.53. 4. A method for producing (poly)diaminodiphenylmethane according to claim 1, comprising the following stages: 1) mixing HCl and aniline and a mixture of recycled dimeric isomers of diaminodiphenylmethanes (MDA); 2) reaction of a mixture of aniline, dimeric isomers of diaminodiphenylmethanes and HCl with an aqueous solution of formaldehyde at a temperature not exceeding 70°C; 3) increasing the temperature of the reaction mass obtained in stage 2 to a temperature below or equal to 140°C and maintaining it at this temperature; 4) neutralization of acidic compounds in the mass obtained in stage 3; 5) washing the mass obtained in stage 4 with water; 6) distillation of low-boiling components and aniline from the mass obtained in stage 5; 7) distillation of the mixture of dimeric isomers of diaminodiphenylmethanes from the mass obtained in stage 6, characterized in that the flow of recycled mixture of dimeric isomers of diaminodiphenylmethanes obtained in stage 7 is directed to stage 1. 5. The method according to claim 4, wherein the mixture of recycled dimers is a mixture of dimeric diaminodiphenylmethanes containing at least 50% 4,4'-MDA. 6. The method according to claim 5, wherein HCl is hydrochloric acid or gaseous hydrogen chloride, preferably hydrochloric acid, more preferably 31-38% hydrochloric acid. 7. The method according to claim 4 or 5, wherein the preferred temperature in step 2) is from 20 to 70°C. 8. The method according to any one of paragraphs 4-7, in which the temperature increase in stage 3 is carried out to values in the range of 80-140°C. 9. A method for producing (poly)diaminodiphenylmethane according to claim 1, comprising the following stages: 1) mixing HCl and aniline with the addition of a portion of the recycled mixture of dimeric isomers of diaminodiphenylmethanes (MDA), comprising from 0 to 25 wt.% of the total amount of the added recycled mixture; 2) the reaction of a mixture of aniline and HCl with the first part of an aqueous solution of formaldehyde at a temperature _T1 of no higher than 70°C, where the said first part of an aqueous solution of formaldehyde constitutes from 50 to 100% of the total amount of formaldehyde introduced into the reaction; 3) adding the remaining portion of the recycled mixture of dimeric isomers of diaminodiphenylmethanes (MDA) until the total amount of MDA reaches no more than 25 wt.% of the initial mass of aniline; 4) * in the case where at stage 2) less than 100% of the total amount of formaldehyde introduced into the reaction is introduced into the reaction, adding the remaining part of the formaldehyde, amounting to from more than 0 and up to 50% of the total amount of formaldehyde introduced into the reaction; 4) maintaining the reaction mass obtained in stage 3 or, in the case of stage 4*, obtained in stage 4*, at a temperature _T2 not exceeding 80°C; 5) increasing the temperature of the reaction mass obtained in stage 4 to a temperature below or equal to 140°C and maintaining it at this temperature; 6) neutralization of acidic compounds in the mass obtained in stage 5; 7) washing the mass obtained in stage 6 with water; 8) distillation of low-boiling components and aniline from the mass obtained in stage 7; 9) distillation of the mixture of dimeric isomers of diaminodiphenylmethanes from the mass obtained in stage 8, characterized in that the mixture of dimeric isomers of diaminodiphenylmethanes obtained in step 9 is sent to step (1) and/or step (3). 10. The method according to claim 9, wherein HCl is hydrochloric acid or gaseous hydrogen chloride, preferably hydrochloric acid, more preferably 31-38% hydrochloric acid. 11. The method according to claim 9, wherein at stage 3 the addition of the remaining portion of the recycled mixture of dimeric isomers of diaminodiphenylmethanes (MDA) is carried out until the total amount of MDA is reached, which is from 5 wt.% to 25 wt.% of the initial mass of aniline. 12. The method according to any one of paragraphs 9-11, in which stage 4* is carried out at a temperature from 30 to 80°C. 13. The method according to any one of paragraphs 9-12, wherein the holding in stage 4 is carried out at a temperature from 30 to 80°C. 14. The method according to any one of paragraphs 9-13, in which the temperature increase in stage 5 is carried out to values in the range from 90 to 140°C. 15. The method according to any one of paragraphs 9-14, wherein the mixture of recycled dimeric isomers of diaminodiphenylmethanes is a mixture of dimeric diaminodiphenylmethanes containing at least 50% 4,4'-MDA. 16. The method according to any one of paragraphs. 4-15, in which the mixing in stage 1 is carried out at a molar ratio of chlorine from HCl and total nitrogen from aniline and recycled MDA C1/N, equal to (0.2-0.4)/1. 17. (Poly)diaminodiphenylmethane according to any one of claims 1-3, obtained by the method according to any one of claims 4-16. 18. A method for producing (poly)diphenylmethane diisocyanate, comprising phosgenating (poly)diaminodiphenylmethane according to any one of claims 1-3 or (poly)diaminodiphenylmethane obtained by the method according to any one of claims 4-16, to obtain (poly)diphenylmethane diisocyanate, characterized in that (poly)diaminodiphenylmethane has an oligomeric distribution characterized by a tetramer/trimer weight ratio of no more than 0.48 with a trimer/dimer weight ratio of at least 0.45 and a viscosity at 90°C of 50-150 mPa⋅s. 19. (Poly) diphenylmethane diisocyanate obtained by the method according to claim 18, characterized by a viscosity of 150-250 mPa⋅s at 25°C.