Method for preparing diphenylmethane-based diamines and polyamines

Abstract

The present application relates to a method for preparing diphenylmethane-based diamines and polyamines. By controlling the initial dispersion coefficient ω of the feeding of a raw material, i.e., an aqueous formaldehyde solution, the conversion rate of aniline is enabled to reach 70-99% of the ultimate conversion rate while diphenylmethane-based diamines and polyamines with the same quality are produced and prepared, thereby greatly reducing energy consumption during the recovery of unreacted aniline, and improving the production efficiency of a device. Moreover, the production process is stable, the content of N-methyl impurities in the prepared diphenylmethane-based diamines and polyamines is less than or equal to 0.25%, the distribution of MDAs having different rings meets the downstream production requirement, and there is no obvious blockage caused by macromolecular polymers during a reaction process.

Description

A method for preparing diphenylmethane series diamines and polyamines Technical Field

[0001] The present application belongs to the technical field of diamine and polyamine preparation, and specifically relates to a method for preparing diphenylmethane series diamines and polyamines. Background Art

[0002] Currently, diamines and polyamines of diphenylmethane are mainly prepared by reacting aniline with formaldehyde in the presence of an acidic catalyst. The mixture of diamines and polyamines (DAM for short) has been widely used in the production of the corresponding di- and polyisocyanates (MDI for short).

[0003] Downstream MDI products are generally divided into three categories: MDI-100, MDI-50, and PMDI. The main differences among these products lie in the content of 4,4-MDI, 2,4-MDI, and tricyclic or higher-ring MDI. To achieve flexible adjustment of the proportions of these three main product categories, the focus in the past has been solely on the content of the corresponding structure, 4,4'-diaminodiphenylmethane (MDA), in DAM. This involves simply adjusting the molar ratio of formaldehyde to hydrochloric acid relative to aniline. This results in a high level of aniline in the reaction liquid after the condensation reaction, impacting plant production efficiency. A large amount of unreacted aniline must be recovered in the DAM refining unit and reused as a raw material for DAM production, resulting in relatively high energy consumption. Therefore, how to maximize aniline conversion while producing the same quality DAM has become a key focus and demand in the industry.

[0004] CN 1610711A discloses a method for preparing MDI, particularly 2,4'-MDI, comprising the following steps: A) reacting aniline and formaldehyde in the presence of an acid to obtain methylenediphenyldiamine and polymethylenepolyphenylenepolyamines; B) reacting the mixture obtained in step A) with phosgene to obtain methylenediphenyldiisocyanate and polymethylenepolyphenylenepolyisocyanates; C) separating the mixture obtained in step B) into monomeric MDI and polymeric MDI; and D) separating the monomeric MDI obtained in step C) from 2,4'-MDI. However, this disclosure only addresses adjusting the isomeric MDA composition in DAM and does not address how to improve aniline conversion.

[0005] CN 107827756A discloses a method, apparatus, and catalyst for preparing diphenylmethane-series diamines and polyamines with low N-methyl impurity content. The method comprises the following steps: a) condensing aniline and formaldehyde in the presence of an acidic catalyst to obtain a reaction mixture containing a polyaminobenzylaniline salt; b) introducing the reaction mixture from a) into a catalyst-loaded fixed-bed reactor for a metathesis rearrangement reaction to obtain a mixture containing diphenylmethane-series diamine and polyamine salts. However, the disclosure focuses on reducing the N-methyl content in DAM and does not address how to increase aniline conversion.

[0006] CN 101279923A discloses a method for preparing polymethylene polyphenyl polyamines. The method uses a high-gravity rotating bed as a mixing reactor for formaldehyde and aniline hydrochloride. A mixture of aniline hydrochloride and circulating fluid, as well as formaldehyde, are fed into the high-gravity rotating bed reactor in proportion. Mixing and condensation reaction occur under high-gravity conditions. The materials leaving the high-gravity rotating bed reactor are fed into a stirred tank for further pre-condensation reaction to obtain a condensation liquid. The condensation liquid is then subjected to heating, molecular rearrangement reaction, neutralization, water washing, and polyamine purification to obtain refined DAM. However, the disclosure only focuses on controlling macromolecular blockages and N-methyl impurities during the reaction process.

[0007] Existing technologies have not yet managed to coordinate the control of the MDA isomer content in DAM, N-methyl impurities, and macromolecular blockages during the reaction with aniline conversion to achieve efficient, high-quality, and low-carbon production of DAM. Therefore, to address the shortcomings of existing technologies, there is a need for a DAM production method that achieves high aniline conversion, a satisfactory distribution of MDA rings in DAM, low N-methyl impurities, and no significant blockage issues.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The purpose of the present application is to provide a method for preparing diphenylmethane series diamines and polyamines, which significantly improves the conversion rate of raw material aniline and greatly reduces the energy consumption of unreacted aniline recovery by controlling the initial dispersion coefficient ω of the raw material formaldehyde aqueous solution feed within a reasonable range. In addition, the prepared diphenylmethane series diamines and polyamines have a low N-methyl impurity content, and the distribution of each ring MDA meets downstream production requirements.

[0011] To achieve this goal, this application adopts the following technical solutions:

[0012] The present application provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0013] (1) Aniline and an acidic compound undergo a first reaction to obtain an aniline salt;

[0014] (2) the formaldehyde aqueous solution and the aniline salt obtained in step (1) are passed into a premixer for a second reaction to obtain a pre-reaction liquid;

[0015] (3) the pre-reaction solution obtained in step (2) is subjected to a third reaction to obtain the diphenylmethane series diamines and polyamines;

[0016] The initial dispersion coefficient ω of the formaldehyde aqueous solution feed is controlled to be ≥ 0.45; the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is calculated by the following formula:

[0017] Where Re is the Reynolds number from the time the formaldehyde aqueous solution is introduced into the premixer to the 5th second, dimensionless; C is the mass concentration of formaldehyde in the formaldehyde aqueous solution; T is the temperature of the second reaction, °C; m is the H + The molar ratio of aniline.

[0018] The preparation method provided in the present application systematically achieves optimal balance from multiple dimensions, including the isomer composition of diphenylmethane series diamines and polyamines, control of N-methyl impurity content, control of blockages in the reaction process, and aniline conversion rate during the production of diphenylmethane series diamines and polyamines. By controlling the initial dispersion coefficient ω of the raw formaldehyde aqueous solution feed, the aniline conversion rate is increased to near the limit conversion rate while producing diphenylmethane series diamines and polyamines of the same quality, significantly reducing the energy consumption of recovering unreacted aniline. In addition, the prepared diphenylmethane series diamines and polyamines have a low N-methyl impurity content, and the distribution of each ring MDA meets downstream production needs.

[0019] In one embodiment, the acidic compound in step (1) comprises any one or a combination of at least two of hydrochloric acid, sulfuric acid, phosphoric acid or methanesulfonic acid. Typical but non-limiting combinations include a combination of hydrochloric acid and sulfuric acid, a combination of sulfuric acid, phosphoric acid and methanesulfonic acid, or a combination of hydrochloric acid, sulfuric acid, phosphoric acid and methanesulfonic acid, preferably hydrochloric acid.

[0020] In one embodiment, the acidic compound in step (1) contains H + The molar ratio of aniline to aniline is (0.04-0.5):1, for example, 0.04:1, 0.15:1, 0.2:1, 0.35:1 or 0.5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] In one embodiment, the mass percentage of the acidic solute in the acidic compound in step (1) is 20-37wt%, for example, it can be 20wt%, 25wt%, 30wt%, 33wt% or 37wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] In one embodiment, the mass concentration of formaldehyde in the formaldehyde aqueous solution in step (2) is 20-55 wt%, for example, 20 wt%, 35 wt%, 40 wt%, 50 wt% or 55 wt%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] In one embodiment, the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution in step (2) is (0.3-0.75):1, for example, it can be 0.3:1, 0.35:1, 0.5:1, 0.65:1 or 0.75:1, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0024] It should be noted that the "limiting conversion rate" in this application means that due to the need for the distribution of isomers and tricyclic and higher-ring MDA in the diphenylmethane series of diamines and polyamines, aniline is not an excessive reactant in the preparation method described in this application. The limiting conversion rate of aniline is greatly affected by the molar ratio of formaldehyde to aniline. The limiting conversion rate of aniline will only occur under the ideal condition that formaldehyde is preferentially converted into low-ring MDA in the reaction products of two-ring or higher-ring MDA. Therefore, when the molar ratio of formaldehyde to aniline does not exceed 0.5, the limiting conversion rate of aniline is twice this molar ratio; however, when this molar ratio is higher than 0.5, the limiting conversion rate of aniline is a fixed value of 100%. In the preparation method described in the present application, it is only necessary to control the initial dispersion coefficient ω of the formaldehyde aqueous solution feed to be ≥ 0.45, so that the aniline conversion rate can reach 70-99% of its limit conversion rate within any ratio range of the formaldehyde to aniline molar ratio in the formaldehyde aqueous solution. The larger the initial dispersion coefficient ω of the formaldehyde aqueous solution feed, the closer the aniline conversion rate is to its limit conversion rate of 99%.

[0025] In one embodiment, the premixer in step (2) is in the form of any one of a static mixer, a liquid-liquid jet mixer, a stirred tank or a homogenizing pump mixer.

[0026] In one embodiment, the Reynolds number Re from the start of the introduction of the formaldehyde aqueous solution into the premixer to the 5th second in step (2) is ≥10,000, for example, it can be 10,000, 50,000, 100,000, 500,000 or 1,000,000, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 100,000-1,000,000.

[0027] The Reynolds number is preferably within a reasonable range based on the consideration of the operating cost of large-scale industrial energy input equipment and the formaldehyde pre-dispersion effect.

[0028] In one embodiment, the temperature of the second reaction in step (2) is 30-100°C, for example, 30°C, 50°C, 60°C, 80°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 50-80°C.

[0029] In one embodiment, the time for the second reaction in step (2) is 5-40 s, for example, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s or 40 s, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] In one embodiment, the third reaction in step (3) includes a condensation reaction and a transposition reaction.

[0031] In one embodiment, the temperature of the condensation reaction is 50-100°C, for example, 50°C, 60°C, 70°C, 80°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In one embodiment, the condensation reaction time is 10-50 min, for example, 10 min, 20 min, 30 min, 40 min or 50 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] In one embodiment, the temperature of the metathesis reaction is 80-130°C, for example, 80°C, 100°C, 110°C, 120°C or 130°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In one embodiment, the transposition reaction time is 1.5-4 h, for example, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h or 4 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In one embodiment, after the third reaction in step (3) is completed, a post-treatment step is also included.

[0036] In one embodiment, the post-treatment includes neutralization, water washing and refining.

[0037] In one embodiment, the refining includes the steps of removing aniline and water.

[0038] Compared with the prior art, this application has the following beneficial effects:

[0039] The preparation method provided in the present application systematically achieves optimal balance from multiple dimensions, including the isomer composition of diphenylmethane series diamines and polyamines, N-methyl impurity content control, reaction blockage control, and aniline conversion rate during the production of diphenylmethane series diamines and polyamines. By controlling the initial dispersion coefficient ω of the raw formaldehyde aqueous solution feed, the aniline conversion rate reaches 70-99% of its limit conversion rate while producing the same quality diphenylmethane series diamines and polyamines. This significantly reduces the energy consumption of unreacted aniline recovery, improves the production efficiency of the device, and stabilizes the production process. The N-methyl impurities in the prepared diphenylmethane series diamines and polyamines are ≤0.25%, the distribution of each ring MDA meets downstream production requirements, and no obvious blockage caused by large molecular polymers is observed during the reaction process.

[0040] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0041] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0042] Sources of raw materials in the following examples:

[0043] Aniline: provided by Wanhua Yantai Industrial Park, with a mass concentration of 99.9wt%; hydrochloric acid: provided by Wanhua Yantai Industrial Park, with a mass concentration of 33wt%; formaldehyde: provided by Wanhua Yantai Industrial Park, with a mass concentration of 37wt%; sodium hydroxide solution: provided by Wanhua Yantai Industrial Park, with a mass concentration of 50wt%; the above four raw materials can also be commercially available products that meet national standards and the above concentrations.

[0044] Example 1

[0045] This embodiment provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0046] (1) hydrochloric acid with a mass concentration of 33 wt% reacts with 99.9 wt% aniline to obtain aniline hydrochloride; + The molar ratio of aniline is 0.35:1;

[0047] (2) a formaldehyde aqueous solution having a formaldehyde mass concentration of 35 wt% and the aniline hydrochloride obtained in step (1) are passed into a homogenizing pump mixer for a second reaction at a temperature of 60° C., a reaction time of 5 s, and a Reynolds number (Re) of 680,000 to obtain a pre-reaction solution; the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution is 0.65:1;

[0048] (3) The pre-reaction liquid obtained in step (2) was condensed at 60° C. for 20 min and then transferred at 110° C. for 1.5 h, and then neutralized by adding a sodium hydroxide solution with a mass concentration of 50 wt % at a molar excess ratio of 1.1 with hydrochloric acid. After phase separation, the mixture was washed with water and refined to remove aniline and water to obtain the diphenylmethane series diamines and polyamines.

[0049] Example 2

[0050] This embodiment provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0051] (1) hydrochloric acid with a mass concentration of 33 wt% reacts with 99.9 wt% aniline to obtain aniline hydrochloride; + The molar ratio with aniline is 0.04:1;

[0052] (2) a formaldehyde aqueous solution having a formaldehyde mass concentration of 20 wt% and the aniline hydrochloride obtained in step (1) are introduced into a stirred tank for a second reaction at a temperature of 50° C., a reaction time of 40 s, and a Reynolds number (Re) of 100,000 to obtain a pre-reaction solution; the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution is 0.3:1;

[0053] (3) The pre-reaction liquid obtained in step (2) was condensed at 50° C. for 50 min and then transferred at 80° C. for 4 h, and then neutralized by adding a 50 wt% sodium hydroxide solution at a molar excess ratio of 1.1 to hydrochloric acid. After phase separation, the mixture was washed with water and refined to remove aniline and water to obtain the diphenylmethane series diamines and polyamines.

[0054] Example 3

[0055] This embodiment provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0056] (1) hydrochloric acid with a mass concentration of 33 wt% reacts with 99.9 wt% aniline to obtain aniline hydrochloride; + The molar ratio with aniline is 0.5:1;

[0057] (2) introducing a formaldehyde aqueous solution having a formaldehyde mass concentration of 55 wt% and the aniline hydrochloride obtained in step (1) into a static mixer for a second reaction at a temperature of 80° C., a reaction time of 15 s, and a Reynolds number (Re) of 1,000,000 to obtain a pre-reaction solution; the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution is 0.75:1;

[0058] (3) The pre-reaction liquid obtained in step (2) is sequentially condensed at 100° C. for 10 min and transferred at 130° C. for 2 h, and then neutralized by adding a sodium hydroxide solution with a mass concentration of 50 wt % at a molar excess ratio of 1.1 with hydrochloric acid. After phase separation, the mixture is washed with water and refined to remove aniline and water to obtain the diphenylmethane series diamines and polyamines.

[0059] Example 4

[0060] This embodiment provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0061] (1) hydrochloric acid with a mass concentration of 33 wt% reacts with 99.9 wt% aniline to obtain aniline hydrochloride; + The molar ratio with aniline is 0.15:1;

[0062] (2) a formaldehyde aqueous solution having a formaldehyde mass concentration of 45 wt% and the aniline hydrochloride obtained in step (1) are passed into a homogenizing pump mixer for a second reaction at a temperature of 40° C., a time of 10 s, and a Reynolds number (Re) of 250,000 to obtain a pre-reaction solution; the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution is 0.4:1;

[0063] (3) The pre-reaction liquid obtained in step (2) was condensed at 50° C. for 30 min and then transferred at 90° C. for 3.5 h, and then neutralized by adding a sodium hydroxide solution with a mass concentration of 50 wt % at a molar excess ratio of 1.1 with hydrochloric acid. After phase separation, the mixture was washed with water and refined to remove aniline and water to obtain the diphenylmethane series diamines and polyamines.

[0064] Example 5

[0065] This embodiment provides a method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps:

[0066] (1) hydrochloric acid with a mass concentration of 33 wt% reacts with 99.9 wt% aniline to obtain aniline hydrochloride; + The molar ratio with aniline is 0.25:1;

[0067] (2) introducing a formaldehyde aqueous solution having a formaldehyde mass concentration of 30 wt% and the aniline hydrochloride obtained in step (1) into a stirred tank for a second reaction at a temperature of 55° C., a reaction time of 25 s, and a Reynolds number (Re) of 20,000 to obtain a pre-reaction solution; the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution is 0.5:1;

[0068] (3) The pre-reaction liquid obtained in step (2) is sequentially condensed at 60° C. for 40 min and transferred at 100° C. for 2.5 h, and then neutralized by adding a sodium hydroxide solution with a mass concentration of 50 wt % at a molar excess ratio of 1.1 with hydrochloric acid. After phase separation, the mixture is washed with water and refined to remove aniline and water to obtain the diphenylmethane series diamines and polyamines.

[0069] Comparative Example 1

[0070] This comparative example provides a method for preparing diphenylmethane series diamines and polyamines. The difference from Example 5 is that the Reynolds number Re in step (2) is adjusted to 12000, and the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is adaptively obtained to be 0.430. The rest is the same as Example 5.

[0071] Comparative Example 2

[0072] This comparative example provides a method for preparing diphenylmethane series diamines and polyamines, which is different from Example 5 in that the H + The molar ratio of aniline to formaldehyde was adjusted to 0.05:1, and the initial dispersion coefficient ω of the formaldehyde aqueous solution feed was adapted to be 0.402. The rest was the same as in Example 5.

[0073] Comparative Example 3

[0074] This comparative example provides a method for preparing diphenylmethane series diamines and polyamines. The difference from Example 5 is that the formaldehyde mass concentration in the formaldehyde aqueous solution in step (2) is adjusted to 50wt%, and the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is adaptively obtained to be 0.408. The rest is the same as Example 5.

[0075] Comparative Example 4

[0076] This comparative example provides a method for preparing diphenylmethane series diamines and polyamines. The difference from Example 5 is that the temperature of the second reaction in step (2) is adjusted to 80°C, and the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is adaptively obtained to be 0.436. The rest is the same as Example 5.

[0077] Comparative Example 5

[0078] This comparative example provides a method for preparing diphenylmethane series diamines and polyamines. The difference from Example 5 is that the Reynolds number Re in step (2) is adjusted to 8000, and the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is adaptively obtained to be 0.412. The rest is the same as Example 5.

[0079] The diphenylmethane series diamines and polyamines were prepared using the preparation methods provided in Examples 1-5 and Comparative Examples 1-5. The components in the diphenylmethane series diamines and polyamines were determined by liquid chromatography using an Agilent 1200 analytical instrument. The bicyclic MDA content and N-methyl content in the obtained diphenylmethane series diamines and polyamines are shown in Table 1.

[0080] The method for determining the unreacted aniline content in the pre-reaction liquid includes: neutralizing the pre-reaction liquid with an excess of sodium hydroxide solution, then dissolving it with methanol to form a homogeneous phase, and then analyzing it by liquid chromatography using an Agilent 1200 analyzer. The degree to which the aniline conversion rate reaches the limit conversion rate is calculated by a formula. The results are shown in Table 1.

[0081] The initial dispersion coefficient ω of the formaldehyde aqueous solution feed was calculated using the formula, and the results are shown in Table 1. The pressure drop change of the reaction heat transfer device was monitored for 30 days, and the results are shown in Table 1.

[0082] Table 1

[0083] It can be concluded from Examples 1-5 in Table 1 that the preparation method provided by the present application can significantly improve the conversion rate of the raw material aniline to 70-99% of its limit conversion rate, regardless of how the parameters in reaction steps (1) and (2) are changed, as long as the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is controlled to be ≥ 0.45. At the same time, the diphenylmethane series diamines and polyamines prepared have a high content of bicyclic MDA and a low content of N-methyl, and there is no increase in the pressure drop of the reaction heat transfer device.

[0084] From the comparison between Example 5 and Comparative Examples 1-4, it can be seen that although the Reynolds number and H + The molar ratio of aniline to formaldehyde, the mass concentration of the aqueous formaldehyde solution, the temperature of the second reaction, and other parameters in the preparation method are all within the specified ranges. However, if the initial dispersion coefficient ω of the aqueous formaldehyde feed is less than 0.45, the conversion rate of the raw material aniline will drop significantly to below 70% of its limit conversion rate.

[0085] Comparison of Comparative Example 1 and Comparative Example 5 shows that when the Reynolds number exceeds the specified range, the initial dispersion coefficient ω of the formaldehyde aqueous solution feed decreases to below 0.45. At this time, the conversion rate of the raw material aniline continues to decrease, and the dicyclic MDA content and N-methyl content in the obtained diphenylmethane series diamines and polyamines further deteriorate in an unexpected direction. More seriously, the blockage of the reaction heat transfer device rapidly intensifies, and the operation is stopped due to blockage after 5 days.

[0086] In summary, the preparation method provided in the present application systematically achieves optimal balance from multiple dimensions, including the isomer composition of diphenylmethane series diamines and polyamines, N-methyl impurity content control, reaction process blockage control, and aniline conversion rate in the production process of diphenylmethane series diamines and polyamines. By controlling the initial dispersion coefficient ω of the raw formaldehyde aqueous solution feed, the aniline conversion rate reaches 70-99% of its limit conversion rate while producing the same quality diphenylmethane series diamines and polyamines. This significantly reduces the energy consumption of recovering unreacted aniline, improves the production efficiency of the device, and stabilizes the production process. The N-methyl impurities in the prepared diphenylmethane series diamines and polyamines are ≤0.25%, the distribution of each ring MDA meets downstream production requirements, and no obvious blockage problem caused by large molecular polymers is observed during the reaction process.

[0087] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing diphenylmethane series diamines and polyamines, the preparation method comprising the following steps: (1) Aniline and an acidic compound undergo a first reaction to obtain an aniline salt; (2) passing the formaldehyde aqueous solution and the aniline salt obtained in step (1) into a premixer for a second reaction to obtain a pre-reaction liquid; (3) the pre-reaction liquid obtained in step (2) is subjected to a third reaction to obtain the diphenylmethane series diamines and polyamines; The initial dispersion coefficient ω of the formaldehyde aqueous solution feed is controlled to be ≥ 0.45; the initial dispersion coefficient ω of the formaldehyde aqueous solution feed is calculated by the following formula: in, Re is the Reynolds number from the time the formaldehyde aqueous solution is introduced into the premixer to the 5th second, dimensionless; C is the mass concentration of formaldehyde in the formaldehyde aqueous solution; T is the temperature of the second reaction, °C; m is the H + The molar ratio of aniline.

2. The preparation method according to claim 1, wherein The acidic compound in step (1) includes any one of hydrochloric acid, sulfuric acid, phosphoric acid or methanesulfonic acid or a combination of at least two thereof, preferably hydrochloric acid.

3. The preparation method according to claim 1 or 2, wherein: In step (1), the acidic compound H + The molar ratio with aniline is (0.04-0.5):1; Optionally, the mass percentage of the acidic solute in the acidic compound in step (1) is 20-37wt%.

4. The preparation method according to any one of claims 1 to 3, wherein: The mass concentration of formaldehyde in the formaldehyde aqueous solution in step (2) is 20-55wt%; Optionally, the molar ratio of formaldehyde to aniline in the formaldehyde aqueous solution in step (2) is (0.3-0.75):

1.

5. The preparation method according to any one of claims 1 to 4, wherein: The premixer in step (2) may be any one of a static mixer, a liquid-liquid jet mixer, a stirred tank or a homogenizing pump mixer.

6. The preparation method according to any one of claims 1 to 5, wherein: The Reynolds number Re≥10000 from the time the formaldehyde aqueous solution is introduced into the premixer to the 5th second.

7. The preparation method according to any one of claims 1 to 6, wherein: In step (2), the Reynolds number Re from the beginning of the formaldehyde aqueous solution being introduced into the premixer to the 5th second is 100,000-1,000,000.

8. The preparation method according to any one of claims 1 to 7, wherein: Step (2) The temperature of the second reaction is 30-100° C.; Optionally, the time of the second reaction in step (2) is 5-40s.

9. The preparation method according to claim 8, wherein: The temperature of the second reaction in step (2) is 50-80°C.

10. The preparation method according to any one of claims 1 to 9, wherein: The third reaction in step (3) includes a condensation reaction and a transposition reaction.

11. The preparation method according to claim 10, wherein: The temperature of the condensation reaction is 50-100°C; Optionally, the condensation reaction time is 10-50 min; Optionally, the temperature of the metathesis reaction is 80-130°C; Optionally, the translocation reaction time is 1.5-4h.

12. The preparation method according to any one of claims 1 to 11, wherein: After the third reaction in step (3) is completed, a post-treatment step is also included; Optionally, the post-treatment includes neutralization, washing and refining; Optionally, the refining includes a step of removing aniline and water.

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