WO2025118188A1 - Method for preparing diphenylmethane-based diamine and polyamine - Google Patents

Abstract

A method for preparing a diphenylmethane-based diamine and polyamine. The method comprises the following steps: S1, subjecting aniline and hydrochloric acid to a salt formation reaction to obtain a mixed solution containing aniline hydrochloride; S2, subjecting the mixed solution containing aniline hydrochloride to a pre-condensation reaction and a transposition reaction with formaldehyde; and S3, neutralizing the reaction solution, which is obtained by means of the transposition reaction, and washing same with water to obtain a polyamine solution, and separating same to obtain a diphenylmethane-based diamine and polyamine, wherein the characteristic number A in the transposition reaction in step S2 is controlled to be 0.5-3, such that the transposition reaction can adapt to different degrees of protonation during the process of manufacturing MDA, the problem of non-uniform distribution of hydrochloric acid at a low degree of protonation during the conventional process is avoided, and the content of macrocyclic substances (having ten or more rings) in the system can also be reduced.

Description

A method for preparing diphenylmethane series diamines and polyamines Technical Field

The invention relates to the field of isocyanates, and in particular to a method for preparing diphenylmethane series diamines and polyamines.

Background Art

At present, the production process of diphenylmethane diisocyanate (MDI) mainly adopts phosgenation reaction. First, aniline and formaldehyde are condensed under the action of acid catalyst to generate polyamine (DAM). Then, DAM reacts with phosgene in solvent to generate crude MDI. At the same time, crude MDI is prepared into pure MDI and polymerized MDI by distillation. Finally, pure MDI is extracted according to a certain extraction ratio to obtain different MDI isomers or their mixtures. The reaction mechanism of MDI in industrial production can be expressed as follows:

Step 1: Salt formation reaction

Aniline + hydrochloric acid → aniline hydrochloride;

Step 2: Condensation and translocation reaction

Aniline hydrochloride + formaldehyde → polyamine (DAM);

Step 3: Reaction to generate crude MDI.

The second step condensation and transposition reaction is mainly a reaction of aniline and formaldehyde to generate DAM under the catalysis of hydrochloric acid, and its reaction mechanism is as follows:

In the acid-catalyzed reaction of aniline and formaldehyde, hydrochloric acid is usually used as a catalyst. The amount of hydrochloric acid used determines the change in the composition of the reaction product. At the same time, the addition of a large amount of hydrochloric acid enables aniline and formaldehyde to react in a homogeneous phase, ensuring the reaction quality. However, a large amount of hydrochloric acid needs to be neutralized by adding caustic soda after the transposition, resulting in a large amount of caustic soda consumption and increasing costs.

The main components of the transfer liquid are aniline, DAM (including incompletely transferred intermediates), HCl and water. When the molar ratio of hydrochloric acid to aniline is ≥0.20, the transfer liquid is homogeneous as a whole. When the molar ratio of hydrochloric acid to aniline is <0.20, the oil phase (aniline and DAM) and the water phase in the transfer liquid are separated, and most of the hydrochloric acid goes to the water phase, resulting in insufficient hydrochloric acid content in the oil phase, causing the transfer. The liquid cannot be completely transferred, affecting the product quality. At the same time, the stratification of the transferred liquid will lead to incomplete neutralization in the subsequent neutralization process, which will cause subsequent equipment corrosion and abnormal product quality. At the same time, after the hydrochloric acid ratio is reduced, the content of macrocyclic substances has increased significantly under the existing process. These substances will eventually form heavy-ring MDI after photochemical treatment, affecting the color number L* of PM.

Patent document DE1643449A describes a method for preparing high-content 4,4'-MDA by first reacting aniline with an acid and then with formaldehyde, wherein the degree of protonation is at least 25%, more preferably at least 50%, and even more preferably 75-100%. The patent proposes that a large amount of acid catalyst is added during the reaction so that all materials are in a uniform phase during the reaction and no stratification occurs. However, a large amount of alkali is required for neutralization in the later stage.

Patent document CN1721389B discloses a method for producing MDA at a low protonation degree, but the patent requires the removal of a portion of water during the reaction, and a large amount of HCl will be lost with the water, resulting in a low HCl content in the residual oil phase, and the temperature needs to be further increased to 110-250°C to carry out the reaction. In addition, the process requires the addition of a set of oil-water separation equipment, and too high a translocation temperature will cause changes in the product composition, greatly reducing the desired dicyclic content.

From an economic point of view, reducing the amount of hydrochloric acid to further reduce the amount of caustic soda has great value. Moreover, the transposition reactor uses expensive special materials. Adding a large number of equipment or significantly increasing the reaction temperature will inevitably lead to a large investment. Therefore, we need to develop a low-cost modification plan to reduce the hydrochloric acid ratio.

How to reduce the hydrochloric acid content while avoiding the stratification of the oil phase and the water phase, improve the efficiency of the transposition reaction, and improve the product quality has a very positive significance in the industry.

Summary of the invention

In order to solve the above problems, the present invention provides a method for preparing diphenylmethane series diamines and polyamines. The inventors have found through research that the reaction state of the transposition liquid system can be controlled by the characteristic number A in the process. When the value of A is ≥0.5, the hydrochloric acid in the transposition liquid is evenly distributed as a whole, which will not affect the transposition of the transposition liquid, thereby avoiding the incomplete transposition reaction caused by oil-water stratification and the problem of incomplete neutralization in the subsequent neutralization process. The method can adapt to different protonation degrees in the MDA manufacturing process and can reduce the content of macrocyclic substances (more than ten rings) in the system.

In order to solve the above problems, the present invention provides a diphenylmethane series of diamines and polyamines The preparation method comprises the following steps:

S1: Aniline and hydrochloric acid undergo a salt-forming reaction to obtain a mixed solution containing aniline hydrochloride;

S2: a mixed solution containing aniline hydrochloride and formaldehyde undergoes a pre-condensation reaction and a transposition reaction;

S3: The reaction solution obtained by the transposition reaction is neutralized and washed with water to obtain a polyamine solution, and then separated to obtain diphenylmethane series diamines and polyamines (DAM);

Wherein, in step S2, the characteristic number A in the control translocation reaction is 0.5 to 3 (e.g., 0.55, 0.6, 0.85, 0.9, 1.0, 1.2, 1.4, 1.5, 1.8, 2.2, 2.5, 2.8), preferably 0.8 to 2;

Among them, the characteristic number A = v*p/[(1.75-5*n _HCl )*μ], wherein v is the flow rate of the transposition liquid during the transposition reaction, in m/s; p is the density of the transposition liquid during the transposition reaction, in g/ml; n _HCl is the molar ratio of solute HCl to aniline in hydrochloric acid; μ is the viscosity of the transposition liquid, in cp.

The process of reacting the DAM obtained in the present invention with phosgene in a solvent to generate crude MDI can be achieved by conventional operations in the art, which will not be described in detail here.

By controlling the characteristic number A of the transposition reaction stage within the scope of the present invention, the MDA manufacturing process can adapt to different protonation degrees, avoiding the problem of uneven distribution of hydrochloric acid at a low protonation degree (n _HCl ≤0.2) in the conventional process, and at the same time reducing the content of macrocyclic substances (more than ten rings) in the system.

In some embodiments, in step S1, the molar ratio of the solute HCl to aniline in the hydrochloric acid is 0.02 to 0.2; for example, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.15, 0.18.

It can be seen from the formula of the characteristic number A that those skilled in the art can control the value of A within the range required by the present invention by reducing viscosity, increasing flow rate, increasing density, etc. according to common means in the art.

In some embodiments, the existing reactor may be modified during step S2, such as by increasing injection to control the characteristic number A.

In some embodiments, the reaction temperature of the pre-condensation reaction stage in step S2 is 35-95°C (for example, 40°C, 50°C, 55°C, 65°C, 70°C, 75°C, 85°C), preferably 60-80°C; the addition of formaldehyde can be carried out in one or more stages, preferably in four stages, and the residence time of each stage is 3-60 min (for example, 4 min, 5 min, 8 min, 12 min, 15 min, 20 min, 25 min, 32 min, 35 min, 40 min, 50 min, 55 min), preferably 10-30 min.

In some embodiments, in step S2, the molar ratio of formaldehyde to aniline is 0.25-0.55 (e.g., 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.4, 0.42, 0.48, 0.5, 0.54), preferably 0.35-0.45.

In some embodiments, the reaction temperature of the transposition reaction stage in step S2 is 95-180°C (e.g., 105°C, 120°C, 140°C, 155°C, 160°C, 175°C), preferably 100-150°C, and the residence time is controlled at 60-180 min (e.g., 70 min, 80 min, 100 min, 120 min, 140 min, 160 min, 175 min), preferably 90-150 min.

In some embodiments, an alkaline solution is used for neutralization in step S3;

In some embodiments, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 32-50%, for example, 34%, 35%, 38%, 40%, 42%, 45%, 48%.

Preferably, the molar amount of the alkali solution added for neutralization (based on the solute alkali in the alkali solution) is 1.05 to 1.3 times (e.g., 1.1, 1.15, 1.2, 1.22, 1.25, 1.28 times) the molar amount of hydrochloric acid (based on the solute HCl in the hydrochloric acid).

The present invention provides a method for preparing diphenylmethane series diamines and polyamines with a low protonation degree, thereby realizing a method for preparing diphenylmethane diisocyanate (MDI) with a low protonation degree. By studying the process, the characteristic number A is within a specific range, and the demand for a transposition liquid with a low protonation degree can be met. The transposition liquid will not be stratified during the transposition reaction stage, and will not cause a drastic change in component content due to high temperature, which is conducive to later neutralization.

In addition, the method of the present invention can also reduce the content of macrocyclic products (more than ten rings). In some preferred embodiments of the present invention, the content of macrocyclic products can reach 10 to 500 ppm, for example, 15 ppm, 20 ppm, 40 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 410 ppm.

DETAILED DESCRIPTION

In order to understand the technical features and contents of the present invention in more detail, the contents of the present invention are further explained below in conjunction with implementation cases. Although preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein.

Raw material information:

Aniline material: Wanhua Chemical;

Formaldehyde material: Wanhua Chemical.

Hydrochloric acid: Wanhua Chemical.

Detection method:

The determination method of each component in DAM was carried out by liquid chromatography, the analytical instrument was Agilent 1260; waters C18 chromatographic column, acetonitrile and water gradient elution, and detection at UV 254nm.

In the following examples and comparative examples, the "bicyclic substance" in the DAM product refers to a primary amine with two benzene rings generated after two molecules of aniline react with one molecule of formaldehyde; the "bicyclic untransposed substance" refers to a secondary amine first generated by aniline and formaldehyde under the action of hydrochloric acid in the process of generating the bicyclic substance, most of which undergoes a transposition reaction to generate a primary amine, and the untransposed part is the untransposed substance; the "macrocyclic substance (ten rings or more)" refers to a polyphenylmethane polyamine produced by the polymerization of aniline and formaldehyde, which contains ten or more benzene rings.

Example 1

Hydrochloric acid and aniline materials (mass concentration is 94%) are mixed in a pre-condensation reactor to react, and the molar ratio of solute HCl to aniline in the hydrochloric acid is 0.11:1;

Then, the mixed solution containing aniline hydrochloride obtained by the reaction is reacted with a formaldehyde material (formaldehyde mass concentration is 37%), the molar ratio of formaldehyde to aniline is 0.40:1, the formaldehyde material is added in 3 stages, the residence time of each stage is 20 minutes (the residence time is 60 minutes in total), the reaction temperature is 55°C, and a reaction mixture containing polyaminobenzylaniline salt is generated; the system is heated to 120°C, and the materials enter 3 tank reactors connected in series for transposition reaction, and each reactor increases the injection cycle to control the overall flow rate v of the transposition liquid in the pipeline to 1m/s, and the reaction is continued for 90min; wherein, the characteristic number A value in the transposition reaction is 1, and the calculation method of the A value is as follows:

A=v*p/[(1.75-5*n _HCl )*μ], v=1m/s, p=1.06g/ml, n _HCl =0.11, μ=0.88cp, A=1.

The diphenylmethane series diamine and polyamine solution is obtained by reaction, and then placed in a mixer and neutralized by adding a NaOH solution (mass concentration of 50%), wherein the amount of sodium hydroxide added is 110% of the molar amount of HCl in the hydrochloric acid added for neutralization, and the mixture obtained after neutralization enters a separator and is separated into an organic phase containing the diphenylmethane series diamine and polyamine and an aqueous phase, wherein the organic phase is fully contacted with water in a stirring tank and fully mixed with the organic phase of the diphenylmethane series diamine and polyamine under stirring; after washing, the mixture enters a separator for separation, and the separated oil phase (crude DAM) is subsequently evaporated at 210° C. and stripped at 190° C. to remove light components such as aniline and water therein, and finally refined DAM is obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 50.6%, the content of dicyclic untransposed substances is 2 ppm, and the content of macrocyclic substances (ten rings and above) is 100 ppm.

Example 2

The same method as in Example 1 was used, with the main difference that the overall flow rate v of the transposition liquid during the transposition reaction was 2 m/s, and at this time, the A value was 2; finally, the refined DAM was obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 51.6%, the content of dicyclic untransposed substances is 1.8 ppm, and the content of macrocyclic substances (ten rings and above) is 93 ppm.

Example 3

The same method as in Example 1 was used, with the main differences being that the molar ratio of the solute HCl to aniline in the hydrochloric acid was 0.05:1; and during the transposition reaction, the viscosity of the transposition liquid was μ=0.76 cp, p=1.05 g/ml, and at this time, the A value was 0.92; and finally, the refined DAM was obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 42.6%, the content of dicyclic untransposed substances is 0.9 ppm, and the content of macrocyclic substances (ten rings and above) is 121 ppm.

Example 4

The same method as in Example 1 was used, with the main difference that during the transposition reaction, the viscosity of the transposition liquid was μ=1.5 cp, p=1.1 g/ml, and the A value was 0.6; finally, the refined DAM was obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 43.8%, the content of dicyclic untransposed substances is 1.0 ppm, and the content of macrocyclic substances (ten rings and above) is 152 ppm.

Example 5

The same method as in Example 1 was used, with the main difference that during the transposition reaction, the density of the transposition liquid was p=1.15 g/ml, the viscosity of the transposition liquid was μ=0.5 cp, and the A value was 1.9; finally, the refined DAM was obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 45.8%, the content of dicyclic untransposed substances is 1.1 ppm, and the content of macrocyclic substances (ten rings and above) is 95 ppm.

Example 6

The same method as in Example 1 was adopted, with the main difference that the molar ratio of the solute HCl to aniline in the hydrochloric acid was 0.06:1; and during the transposition reaction, the transposition liquid density p=1.15, the transposition liquid viscosity μ=0.9 cp, the overall flow rate v was 0.8 m/s, and the A value was 0.7 at this time; finally, the refined DAM was obtained.

According to the above process, the transposition liquid is always in a uniform phase during the transposition reaction, and no stratification occurs, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine. The content of dicyclic substances in the produced DAM is 47.2%, the content of dicyclic untransposed substances is 2.2ppm, and the content of macrocyclic substances (ten rings and above) is 143ppm.

Comparative Example 1

The same method as in Example 1 was used, with the main difference that the overall flow rate v of the transposition liquid during the transposition reaction was controlled at 0.25 m/s, at which time the A value was 0.025; and finally, refined DAM was obtained.

When produced according to the above process, the transposition liquid shows obvious stratification during the transposition reaction, especially in the tank reactor, where the oil-water two-phase stratification interface is obvious and the discharge components are unstable, resulting in obvious fluctuations in neutralization and inability to completely carry out neutralization; in the produced DAM, the content of two-ring substances is 32.6%, the content of two-ring untransposed substances is 15%, the content of macrocyclic substances (ten rings and above) is 430ppm, and the content of hydrochloride (unneutralized substance) is 10%.

Comparative Example 2

The same method as in Example 1 is used, the main difference being that the molar ratio of the solute HCl to aniline in the hydrochloric acid is 0.05; during the transposition reaction, the overall flow rate v of the transposition liquid is controlled at 5 m/s, the density p is 1.08 g/ml, the viscosity μ is 0.8 cp, and at this time, the A value is 4.5; and finally The purified DAM was obtained.

According to the above process, the transposition liquid has no obvious stratification during the transposition reaction, but the pressure drop of the transposition liquid is too large, and the system load is reduced; the pH of the brine after neutralization is stable at 12-14, and there is no hydrochloric acid residue in the polyamine; the content of dicyclic substances in the produced DAM is 51.3%, the content of dicyclic untransposed substances is 416ppm, and the content of macrocyclic substances (ten rings and above) is 67ppm. However, the excessively fast flow rate causes the pressure drop in the transposition stage to be too high, and the content of untransposed substances increases, which limits the system load.

Comparative Example 3

The same method as in Example 1 was adopted, the main difference being that the molar ratio of the solute HCl to aniline in the hydrochloric acid was 0.08; and during the transposition process, the density p of the transposition liquid was 1.2 g/ml, and the viscosity μ was 2 cp, at which time the A value was 0.44; and finally, the refined DAM was obtained.

When produced according to the above process, the transposition liquid shows obvious stratification during the transposition reaction, especially in the tank reactor where the oil-water two-phase stratification interface is obvious and the discharge components are unstable, resulting in obvious fluctuations in neutralization and inability to completely carry out neutralization; in the produced DAM, the content of two-ring substances is 26.9%, the content of two-ring untransposed substances is 25%, the content of macrocyclic substances (ten rings and above) is 329 ppm, and the content of hydrochloride (unneutralized substance) is 4%.

The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims (6)

A method for preparing diphenylmethane series diamines and polyamines, characterized in that it comprises the following steps: S1: Aniline and hydrochloric acid undergo a salt-forming reaction to obtain a mixed solution containing aniline hydrochloride; S2: a mixed solution containing aniline hydrochloride and formaldehyde undergoes a pre-condensation reaction and a transposition reaction; S3: The reaction liquid obtained by the transposition reaction is neutralized and washed with water to obtain a polyamine solution, and then separated to obtain diphenylmethane series diamines and polyamines; Wherein, the characteristic number A in the control translocation reaction in step S2 is 0.5 to 3, preferably 0.8 to 2; Among them, the characteristic number A = v*p/[(1.75-5*n _HCl )*μ], wherein v is the flow rate of the transposition liquid during the transposition reaction, in m/s; p is the density of the transposition liquid during the transposition reaction, in g/ml; n _HCl is the molar ratio of solute HCl to aniline in hydrochloric acid; μ is the viscosity of the transposition liquid, in cp. The preparation method according to claim 1, characterized in that in step S1, the molar ratio of the solute HCl to aniline in the hydrochloric acid is 0.02 to 0.2. The preparation method according to claim 1 or 2, characterized in that the reaction temperature in the pre-condensation reaction stage in step S2 is 35 to 95° C., preferably 60 to 80° C.; The addition of formaldehyde can be carried out in one or more stages, preferably four stages, and the residence time of each stage is 3 to 60 minutes, preferably 10 to 30 minutes. The preparation method according to any one of claims 1 to 3 is characterized in that the reaction temperature in the metathesis reaction stage in step S2 is 95 to 180° C., preferably 100 to 150° C., and the residence time is controlled at 60 to 180 min, preferably 90 to 150 min. The preparation method according to any one of claims 1 to 4, characterized in that an alkaline solution is used for neutralization in step S3; Preferably, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution with a concentration of 32-50%. The preparation method according to claim 5, characterized in that the molar amount of the alkali solution (calculated as the solute alkali in the alkali solution) added for neutralization is hydrochloric acid (calculated as the solute HCl in the hydrochloric acid) 1.05 to 1.3 times the molar amount.