Method for preparing diphenylmethane-based diamine and polyamine

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

[0001] The present invention relates to the field of isocyanates, and in particular to a method for preparing diphenylmethane series diamines and polyamines. Background Art

[0002] Currently, the production process of diphenylmethane diisocyanate (MDI) mainly uses phosgenation reaction. First, aniline and formaldehyde undergo condensation reaction under the action of acid catalyst to produce polyamine (DAM). Then, DAM reacts with phosgene in a solvent to produce crude MDI. At the same time, crude MDI is prepared into pure MDI and polymerized MDI through 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 the industrial production process can be expressed as follows:

[0003] Step 1: Salt formation reaction

[0004] Aniline + hydrochloric acid → aniline hydrochloride;

[0005] Step 2: Condensation and translocation reaction

[0006] Aniline hydrochloride + formaldehyde → polyamine (DAM);

[0007] Step 3: Reaction to generate crude MDI.

[0008] The second step condensation and transposition reaction is mainly a reaction in which aniline and formaldehyde react under the catalysis of hydrochloric acid to form DAM. The reaction mechanism is as follows:

[0009] In the acid-catalyzed reaction of aniline and formaldehyde, hydrochloric acid is typically used as a catalyst. The amount of hydrochloric acid used determines the composition of the reaction products. The addition of large amounts of hydrochloric acid allows the aniline and formaldehyde to react in a homogeneous phase, ensuring reaction quality. However, the large amount of hydrochloric acid requires the addition of caustic soda to neutralize it after the translocation, resulting in significant caustic soda consumption and increased costs.

[0010] 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. However, when the molar ratio of hydrochloric acid to aniline is <0.20, the oil phase (aniline and DAM) and the aqueous phase in the transfer liquid separate, with most of the hydrochloric acid entering the aqueous phase. This results in insufficient hydrochloric acid in the oil phase, preventing the transfer liquid from fully transferring, and thus affecting product quality. Furthermore, this stratification of the transfer liquid can easily lead to incomplete neutralization during the subsequent neutralization process, which can cause subsequent equipment corrosion and product quality abnormalities. Furthermore, when the hydrochloric acid ratio is reduced, the content of macrocyclic substances increases significantly under the existing process. These substances ultimately form heavy-ring MDI after photochemical reaction, affecting the PM color number L*.

[0011] Patent document DE1643449A describes a method for producing high-content 4,4'-MDA by first reacting aniline with an acid and then with formaldehyde. The degree of protonation is at least 25%, preferably at least 50%, and even more preferably 75-100%. The patent proposes adding a large amount of acid catalyst during the reaction to maintain a homogeneous phase and prevent separation. However, a large amount of base is required for neutralization at a later stage.

[0012] Patent document CN1721389B discloses a method for producing MDA at a low protonation level. However, this patent requires the removal of some water during the reaction, and a large amount of HCl is lost with the water, resulting in a low HCl content in the residual oil phase. This requires further increasing the reaction temperature to 110-250°C. Furthermore, this process requires the addition of an oil-water separation device, and excessively high translocation temperatures can lead to changes in product composition, significantly reducing the desired dicyclic content.

[0013] From an economic perspective, reducing hydrochloric acid usage, and thus caustic soda usage, is highly valuable. Furthermore, transposition reactors utilize expensive specialty materials, and adding significant equipment or significantly increasing reaction temperatures would inevitably result in significant investment. Therefore, a cost-effective modification solution to reduce the hydrochloric acid ratio was needed.

[0014] How to reduce the hydrochloric acid content while avoiding stratification of the oil phase and the water phase, improve the efficiency of the transposition reaction, and improve product quality has a very positive significance in the industry.

[0015] Summary of the Invention

[0016] To address the above-mentioned problems, the present invention provides a method for preparing diphenylmethane series diamines and polyamines. The inventors have discovered 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 overall, which does not affect the transposition of the transposition liquid, thereby avoiding the problems of incomplete transposition reaction caused by oil-water stratification and incomplete neutralization in the subsequent neutralization process. This method enables the preparation of different protonation degrees during the MDA manufacturing process and can also reduce the content of macrocyclic substances (more than ten rings) in the system.

[0017] To solve the above problems, the present invention provides a method for preparing diphenylmethane series diamines and polyamines, comprising the following steps:

[0018] S1: Aniline and hydrochloric acid undergo salt-forming reaction to obtain a mixed solution containing aniline hydrochloride;

[0019] S2: a mixed solution containing aniline hydrochloride and formaldehyde undergoes a pre-condensation reaction and a transposition reaction;

[0020] S3: The reaction solution obtained from the metathesis reaction is neutralized and washed with water to obtain a polyamine solution, which is then separated to obtain diphenylmethane series diamines and polyamines (DAM);

[0021] 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;

[0022] Among them, the characteristic number A=v*p / [(1.75-5*n HCl )*μ], where 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 transfer liquid, unit is cp.

[0023] 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 and will not be described in detail here.

[0024] By controlling the characteristic number A of the transposition reaction stage within the scope of the present invention, it can adapt to different protonation degrees in the MDA manufacturing process, avoiding the low protonation degree (n HCl ≤0.2) can solve the problem of uneven distribution of hydrochloric acid and reduce the content of macrocyclic substances (more than ten rings) in the system.

[0025] In some embodiments, in step S1, the molar ratio of solute HCl to aniline in hydrochloric acid is 0.02-0.2; for example, 0.03, 0.04, 0.05, 0.06, 0.08, 0.1, 0.12, 0.14, 0.15, 0.18.

[0026] It can be seen from the formula of the characteristic number A that those skilled in the art can control the value of A to be within the range required by the present invention by reducing viscosity, increasing flow rate, increasing density, etc. according to common means in the field.

[0027] In some embodiments, the existing reactor may be modified during step S2, such as by increasing injection to control the characteristic number A.

[0028] 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 4 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.

[0029] 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.

[0030] In some embodiments, the reaction temperature of the metathesis reaction stage in step S2 is 95-180°C (for example, 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 (for example, 70 min, 80 min, 100 min, 120 min, 140 min, 160 min, 175 min), preferably 90-150 min.

[0031] In some embodiments, in step S3, an alkaline solution is used for neutralization;

[0032] 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%, or 48%.

[0033] Preferably, the molar amount of the alkali solution added for neutralization (calculated as 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 (calculated as the solute HCl in the hydrochloric acid).

[0034] 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 satisfied to be within a specific range, which can meet the requirements of a transposition liquid with a low protonation degree. The transposition liquid will not stratify during the transposition reaction stage, and will not cause drastic changes in component content due to high temperature, which is conducive to subsequent neutralization.

[0035] 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

[0036] 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.

[0037] Raw material information:

[0038] Aniline material: Wanhua Chemical;

[0039] Formaldehyde material: Wanhua Chemical.

[0040] Hydrochloric acid: Wanhua Chemical.

[0041] Detection method:

[0042] The components in DAM were determined by liquid chromatography using an Agilent 1260 waters C18 column, gradient elution with acetonitrile and water, and detection at UV 254 nm.

[0043] In the following examples and comparative examples, the "bicyclic substance" in the DAM product refers to a primary amine with two benzene rings formed by the reaction of two molecules of aniline with one molecule of formaldehyde; the "bicyclic untransposed substance" refers to a secondary amine initially formed by aniline and formaldehyde under the action of hydrochloric acid in the process of forming the bicyclic substance, most of which undergoes a transposition reaction to form a primary amine, and the portion that does not undergo transposition is the untransposed substance; the "macrocyclic substance (ten rings or more)" refers to a polyphenylmethane polyamine produced by the polymerization of aniline and formaldehyde, wherein the polyphenylmethane polyamine contains ten or more benzene rings.

[0044] Example 1

[0045] Hydrochloric acid and aniline (mass concentration of 94%) were mixed in a pre-condensation reactor to react, and the molar ratio of solute HCl to aniline in the hydrochloric acid was 0.11:1;

[0046] The resulting aniline hydrochloride mixture was then reacted with formaldehyde (formaldehyde concentration of 37%) at a molar ratio of formaldehyde to aniline of 0.40:1. The formaldehyde was added in three stages, each with a residence time of 20 minutes (for a total of 60 minutes). The reaction temperature was 55° C. to generate a reaction mixture containing polyaminobenzylaniline salt. The system was heated to 120° C., and the materials were introduced into three series-connected tank reactors for a transposition reaction. Each reactor was subjected to a jet cycle to control the overall flow velocity v of the transposition liquid in the pipeline to 1 m / s. The reaction was continued for 90 minutes. The characteristic number A in the transposition reaction was 1, and the A value was calculated as follows:

[0047] 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.

[0048] The reaction produces a diphenylmethane series diamine and polyamine solution, which is then placed in a mixer and neutralized by adding a NaOH solution (mass concentration of 50%). The amount of sodium hydroxide added is 110% of the molar amount of HCl in the hydrochloric acid added for neutralization. The neutralized mixture enters a separator and is separated into an organic phase containing the diphenylmethane series diamine and polyamine and an aqueous phase. 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. The separated oil phase (crude DAM) is then evaporated at 210° C. and stripped at 190° C. to remove light components such as aniline and water, thereby obtaining refined DAM.

[0049] According to the above process, the transposition liquid is always in a homogeneous 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 to 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.

[0050] Example 2

[0051] The same method as in Example 1 was used, with the main difference being 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; and finally, refined DAM was obtained.

[0052] According to the above process, the transposition liquid is always in a homogeneous phase during the transposition reaction, without stratification, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, no hydrochloric acid residue is left in the polyamine, and 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.

[0053] Example 3

[0054] The same method as in Example 1 was used, except 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, purified DAM was obtained.

[0055] According to the above process, the transposition liquid is always in a homogeneous phase during the transposition reaction, without stratification, etc., which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, no hydrochloric acid residue is left in the polyamine, and 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.

[0056] Example 4

[0057] The same method as in Example 1 was used, with the main difference being 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, refined DAM was obtained.

[0058] According to the above process, the transposition liquid is always in a homogeneous phase during the transposition reaction, without stratification, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, no hydrochloric acid residue is left in the polyamine, and 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.

[0059] Example 5

[0060] The same method as Example 1 was used, with the main difference being that during the transposition reaction, the density of the transposition liquid p = 1.15 g / ml, the viscosity of the transposition liquid μ = 0.5 cp, and at this time, the A value was 1.9; finally, refined DAM was obtained.

[0061] According to the above process, the transposition liquid is always in a homogeneous phase during the transposition reaction, without stratification, which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, no hydrochloric acid residue is left in the polyamine, and 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.

[0062] Example 6

[0063] The same method as in Example 1 was used, except that the molar ratio of the solute HCl to aniline in the hydrochloric acid was 0.06:1; and during the transposition reaction, the density of the transposition liquid p was 1.15, the viscosity of the transposition liquid μ was 0.9 cp, the overall flow velocity v was 0.8 m / s, and the A value was 0.7; finally, refined DAM was obtained.

[0064] According to the above process, the transposition liquid is always in a homogeneous phase during the transposition reaction, without stratification, etc., which does not affect the neutralization reaction; the pH of the brine after neutralization is stable at 12-14, no hydrochloric acid residue is left in the polyamine, and the content of dicyclic substances in the produced DAM is 47.2%, the content of dicyclic untransposed substances is 2.2 ppm, and the content of macrocyclic substances (ten rings and above) is 143 ppm.

[0065] Comparative Example 1

[0066] The same method as in Example 1 was used, with the main difference being that the overall flow velocity 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.

[0067] According to the above process, the transposition liquid showed obvious stratification during the transposition reaction, especially in the tank reactor, where the oil-water two-phase stratification interface was obvious and the discharge components were unstable, resulting in obvious fluctuations in neutralization and inability to completely carry out neutralization; the content of dicyclic substances in the produced DAM was 32.6%, the content of dicyclic untransposed substances was 15%, the content of macrocyclic substances (ten rings and above) was 430 ppm, and the content of hydrochloride (unneutralized substance) was 10%.

[0068] Comparative Example 2

[0069] The same method as in Example 1 was used, except that the molar ratio of the solute HCl to aniline in the hydrochloric acid was 0.05; during the transposition reaction, the overall flow velocity v of the transposition liquid was controlled at 5 m / s, the density p was 1.08 g / ml, the viscosity μ was 0.8 cp, and at this time, the A value was 4.5; and finally, refined DAM was obtained.

[0070] According to the above process, the transposition liquid showed no obvious stratification during the transposition reaction, but the pressure drop during the transposition liquid feed was too high, reducing the system load. The pH of the neutralized brine remained stable at 12-14, and no hydrochloric acid residue was present in the polyamine. The resulting DAM contained 51.3% dicyclic substances, 416 ppm dicyclic untransposed substances, and 67 ppm macrocyclic substances (ten rings and above). However, the excessively fast flow rate caused an excessively high pressure drop during the transposition stage, and the content of untransposed substances increased, limiting the system load.

[0071] Comparative Example 3

[0072] The same method as in Example 1 was used, except 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 this time, the A value was 0.44; and finally, refined DAM was obtained.

[0073] According to the above process, the transposition liquid showed obvious stratification during the transposition reaction, especially in the tank reactor, where the oil-water two-phase stratification interface was obvious and the discharge components were unstable, resulting in obvious fluctuations in neutralization and inability to completely carry out neutralization; the content of dicyclic substances in the produced DAM was 26.9%, the content of dicyclic untransposed substances was 25%, the content of macrocyclic substances (ten rings and above) was 329 ppm, and the content of hydrochloride (unneutralized substance) was 4%.

[0074] 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 considered within the scope of protection of the present invention.

Claims

1. 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: The mixed solution containing aniline hydrochloride and formaldehyde undergo a pre-condensation reaction and a rearrangement reaction; S3: The reaction solution obtained from the rearrangement reaction is neutralized and washed with water to obtain a polyamine solution, and then separated to obtain diphenylmethane series diamines and polyamines; wherein, in step S2, the characteristic number A in the rearrangement reaction is controlled to be 0.5 to 3, preferably 0.8 to 2; Among them, the number of characteristics A = v * p / [(1.75 - 5 * n HCl ) * μ], where v is the flow rate of the translocation liquid during the translocation reaction, in m / s; p is the density of the translocation liquid during the translocation reaction, in g / ml; n HCl is the molar ratio of the solute HCl in hydrochloric acid to aniline; μ is the viscosity of the translocation liquid, in cp.

2. The preparation method according to claim 1, characterized in that, in step S1, the molar ratio of the solute HCl in hydrochloric acid to aniline is 0.02 to 0.

2.

3. The preparation method according to claim 1 or 2, characterized in that, in step S2, the reaction temperature in the pre-condensation reaction stage is 35 to 95 °C, preferably 60 to 80 °C; The addition of formaldehyde can be carried out in one stage or multiple stages, preferably 4 stages, and the residence time for each stage is 3 to 60 min, preferably 10 to 30 min.

4. The preparation method according to any one of claims 1-3, characterized in that, in step S2, the reaction temperature in the rearrangement reaction stage is 95 to 180 °C, preferably 100 to 150 °C, and the residence time is controlled to be 60 to 180 min, preferably 90 to 150 min.

5. The preparation method according to any one of claims 1-4, characterized in that, in step S3, an alkali solution is used for neutralization; Preferably, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration is 32 to 50%.

6. The preparation method according to claim 5, characterized in that, the molar amount of the added alkali solution (calculated as the solute alkali in the alkali solution) is 1.05 to 1.3 times the molar amount of hydrochloric acid (calculated as the solute HCl in hydrochloric acid).

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