Process for the continuous production of polybenzimidazole by solution polymerization

Abstract

This invention relates to the field of polybenzimidazole and discloses a method for the continuous production of polybenzimidazole using solution polymerization. The method includes the following steps: (1) under solution polymerization conditions, an aromatic component containing at least four amino groups and an aromatic or aliphatic component containing at least two carboxyl groups are polymerized in a reactor to obtain a viscous reaction solution; (2) the viscous reaction solution is discharged from the reactor, and then the reactor is rinsed using a rinsing medium, wherein the rinsing medium is a polar solvent; steps (1) and (2) are repeated in this manner, alternating between the polymerization and rinsing processes. The method of this invention can avoid pipeline blockage problems, improve yield, increase polymer solubility, and improve the uniformity of product quality across batches.

Description

Technical Field

[0001] This invention relates to the field of polybenzimidazole technology, and more specifically to a method for the continuous production of polybenzimidazole using solution polymerization. Background Technology

[0002] Polybenzimidazole (PB) is a class of high-molecular-weight polymers containing benzimidazole groups in their repeating units, and is also a class of high-performance special engineering plastics. It possesses excellent high-temperature resistance, corrosion resistance, high mechanical strength, high hardness, and high wear resistance, making it suitable for use in extreme high-temperature, harsh chemical, and plasma environments. Currently, it is widely used in high-temperature proton exchange membranes, heat-resistant fibers, cut-resistant fibers, gas-liquid separation, fire retardancy, and aerospace fields. There are four main methods for synthesizing PB: parent polymerization, nucleophilic substitution, melt polymerization, and solution polymerization. However, the parent polymerization and nucleophilic substitution methods are limited in their wide application range due to stringent experimental conditions. Currently, melt polymerization and solution polymerization are the most commonly used methods.

[0003] Compared with melt polymerization, solution polymerization has advantages such as milder reaction conditions, lower energy consumption (lower reaction temperature), and more environmentally friendly byproducts (solution polymerization byproducts are water, while melt polymerization byproducts are mostly toxic substances such as phenol), making it highly valuable for industrial applications. However, the preparation of polybenzimidazole using solution polymerization is currently mostly limited to laboratory preparation and lacks large-scale industrial applications.

[0004] Polybenzimidazole has a high glass transition temperature, which affects its processing performance. Improving the solubility of polybenzimidazole in solvents can improve its processing performance. In solution polymerization, especially in continuous production, material residue in the reactor affects the uniformity of the next batch, thus affecting the reaction process, leading to reduced product solubility or yield, and seriously impacting product quality. Summary of the Invention

[0005] The purpose of this invention is to overcome the influence of reactor residues on the quality of subsequent polymerization products in the continuous production process of solution polymerization in the prior art. It provides a method for the continuous production of polybenzimidazole using solution polymerization. This method can avoid the influence of reactor residues on the subsequent polymerization process, improve the solubility of the continuous polymerization product, and increase the product yield.

[0006] To achieve the above objectives, the present invention provides a method for the continuous production of polybenzimidazole using solution polymerization, the method comprising the following steps:

[0007] (1) Under solution polymerization conditions, an aromatic component containing at least four amino groups and an aromatic or aliphatic component containing at least two carboxyl groups are polymerized in a reactor to obtain a viscous reaction solution.

[0008] (2) Drain the viscous reaction liquid from the reactor and then rinse the reactor with a rinsing medium, wherein the rinsing medium is a polar solvent;

[0009] The process of repeating steps (1) and (2) alternates between polymerization and rinsing.

[0010] Through the above technical solution, the present invention achieves the following beneficial effects:

[0011] (1) The method of the present invention can avoid pipeline blockage, increase yield, improve polymer solubility, and improve the uniformity of product quality in each batch.

[0012] (2) The preferred embodiment of the present invention can reduce the operating pressure of the flushing device and the amount of flushing medium used, save time, shorten the product production cycle, and improve efficiency. Attached Figure Description

[0013] Figure 1 This is a photograph of the polybenzimidazole obtained from the second polymerization in Example 1 after dissolution;

[0014] Figure 2 This is a photograph of the polybenzimidazole obtained from the second polymerization of Comparative Example 1 after dissolution. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] This invention provides a method for the continuous production of polybenzimidazole using solution polymerization, the method comprising the following steps:

[0017] (1) Under solution polymerization conditions, an aromatic component containing at least four amino groups and an aromatic or aliphatic component containing at least two carboxyl groups are polymerized in a reactor to obtain a viscous reaction solution.

[0018] (2) Drain the viscous reaction liquid from the reactor and then rinse the reactor with a rinsing medium, wherein the rinsing medium is a polar solvent;

[0019] The process of repeating steps (1) and (2) alternates between polymerization and rinsing.

[0020] According to the present invention, the rinsing medium can be a polar solvent commonly used in the art. Preferably, the rinsing medium includes at least one of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, and water. A single solvent can be used for rinsing, for example, water can be used as the rinsing medium to rinse the reactor; alternatively, multiple solvents can be used, for example, an organic polar solvent and water can be used as rinsing media to rinse the reactor. More preferably, the rinsing medium includes water and at least one selected from methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone. Using a preferred embodiment of the present invention, rinsing is first performed using at least one of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone, and then rinsing is performed using water. This not only reduces the amount of water used as the rinsing medium but also reduces the rinsing pressure.

[0021] According to a particularly preferred embodiment of the present invention, the rinsing medium is N,N-dimethylacetamide and water, or dimethyl sulfoxide and water. The weight ratio of N,N-dimethylacetamide to water is 0.05-0.5:1; the weight ratio of dimethyl sulfoxide to water is 0.05-0.5:1.

[0022] According to the present invention, in order to better remove the polymer adhering to the inner surface of the reactor, preferably, the rinsing is performed under pressure, with a pressure of 0.1 MPa-6 MPa, more preferably 1 MPa-5 MPa. In this invention, the pressure rinsing is performed using a pressure cleaning device (e.g., a high-pressure water gun), and the pressure is the operating pressure set by the pressure cleaning device. Unless otherwise specified, the pressure in this invention is gauge pressure.

[0023] According to the present invention, the temperature of the rinsing medium is not particularly limited. Preferably, the temperature of the rinsing medium is 10-80°C, more preferably 10-50°C, and even more preferably 10-20°C.

[0024] According to the present invention, preferably, the amount of the flushing medium used is 0.4-3 kg, more preferably 0.6-1.5 kg, relative to a reactor with a volume of 2 L.

[0025] In this invention, the reactor for carrying out the polymerization reaction can be a commonly used polymerization reactor in the art, such as a batch reactor (reaction vessel), a tubular reactor (reaction tube), a tower reactor, etc., as long as the reactor can meet the requirements of the polymerization reaction. Typically, the reactor is equipped with a temperature monitoring device and a stirring device, etc.

[0026] According to the present invention, in order to avoid the influence of residual rinsing medium on subsequent polymerization reactions, step (2) preferably further includes drying the reactor. Drying can be achieved by hot nitrogen purging, hot air purging, dryer drying, or any other drying method. More preferably, the drying temperature is 80-150°C.

[0027] According to the present invention, in order to further improve the rinsing effect, preferably, after the viscous reaction liquid is discharged, the temperature inside the reactor is cooled to below 100°C (preferably 60-90°C), and then the reactor is immediately rinsed with a rinsing medium.

[0028] According to the present invention, preferably, the method further includes sequentially precipitating, pulverizing, washing and drying the viscous reaction solution to obtain the polybenzimidazole product.

[0029] According to the present invention, preferably, the precipitation process includes: transferring the viscous reaction solution to a processing vessel containing a precipitant (e.g., water), and causing the polymer in the viscous reaction solution to precipitate or precipitate in the precipitant under stirring. After precipitation, solid-liquid separation is performed to obtain the polymer, which is then sequentially pulverized, washed, and dried.

[0030] According to the present invention, preferably, the polymer obtained after precipitation is mixed with the polymer obtained by rinsing in step (2) and then crushed, washed and dried.

[0031] According to the present invention, preferably, the solvent used in the solution polymerization process is a mixed solvent of phosphorus pentoxide and methanesulfonic acid and / or polyphosphoric acid; more preferably, the weight ratio of methanesulfonic acid to phosphorus pentoxide is 10-50:1.

[0032] According to the present invention, when phosphorus pentoxide and methanesulfonic acid are used as solvents, the method may further include placing methanesulfonic acid and phosphorus pentoxide in a dissolving vessel and stirring at 40-140°C for 10 min-8 h.

[0033] According to the present invention, preferably, the total amount of the aromatic component containing at least four amino groups and the aromatic or aliphatic component containing at least two carboxyl groups is 1-160 mmol, more preferably 1.5-60 mmol, relative to each 100 g of the solvent.

[0034] According to the present invention, preferably, the aromatic component comprising at least four amino groups is an aromatic tetraamine; more preferably, the aromatic tetraamine comprises at least one benzene ring; even more preferably, the aromatic tetraamine is selected from one or more of the following structures:

[0035]

[0036] Wherein, X is selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, substituted or unsubstituted alkyl group, for example, -O-, -S-.

[0037] According to the present invention, preferably, the aromatic or aliphatic component containing at least two carboxyl groups has the structure shown in formula (1):

[0038] HOOC-R-COOH (Formula 1)

[0039] Wherein, R is selected from aromatic rings, aromatic heterocycles or hydrocarbon groups (e.g., alkane groups, cycloalkane groups, olefin groups, etc.); the number of carbon atoms in the structure shown in formula (1) is 6-22;

[0040] More preferably, the aromatic or aliphatic component containing at least two carboxyl groups is selected from one or more of the following structures:

[0041]

[0042] Where n = 4 - 8.

[0043] According to the present invention, preferably, the molar ratio of the aromatic component containing at least four amino groups to the aromatic or aliphatic component containing at least two carboxyl groups is 1:0.6-2; more preferably, it is 1:0.7-1.5.

[0044] According to the present invention, preferably, the solution polymerization conditions include reacting at 60-220°C for 2-56 h with an oxygen content not exceeding 20 ppm (more preferably not exceeding 8 ppm, for example, using a nitrogen atmosphere). More preferably, the solution polymerization conditions include adding an aromatic component containing at least four amino groups and an aromatic or aliphatic component containing at least two carboxyl groups to a reactor filled with solvent, and heating to 60-220°C for 2-48 h. The reactor is preferably heated by circulating heat transfer oil.

[0045] According to the present invention, preferably, the solution polymerization conditions further include adding the solvent to the reactor and keeping it at 40-140°C for 10 min-8 h before carrying out the polymerization reaction, provided that the oxygen content is not higher than 20 ppm.

[0046] According to the present invention, preferably, the entire polymerization reaction is carried out under stirring at a stirring rate of 20-120 rpm. The torque at the end of the polymerization reaction is 1.1-1.6 times that at the beginning of the polymerization reaction.

[0047] The present invention will be described in detail below through embodiments. In the following embodiments,

[0048] All raw materials used are commercially available products.

[0049] The solubility test method for polybenzimidazole products is as follows: 0.4 g of polybenzimidazole is added to 8 g of anhydrous N,N-dimethylacetamide (DMAc) solution, and the solution is heated in a metal bath at 80 °C for 4 h. After heating, the mixture is filtered, and the mass of the filter residue (insoluble matter) is weighed to calculate the solubility of polybenzimidazole.

[0050] Example 1

[0051] (1) Polymerization process: First, methanesulfonic acid and phosphorus pentoxide (weight ratio 12:1, total weight 1600g) were added to the dissolving vessel and heated and stirred at 80℃ for 4h. Then, the mixed solvent of methanesulfonic acid and phosphorus pentoxide was fed into the polymerization vessel (volume 2L) through a conveying pipe and heated to 120℃ under nitrogen purging. Then, 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid were added to the polymerization vessel; the temperature was raised to 140℃, and the torque was recorded. After 5h, the torque increased by 1.2 times, and the reaction was terminated to obtain a viscous reaction liquid. The stirring speed was maintained at 100rpm throughout the reaction, and the atmosphere in the polymerization vessel was nitrogen. The molar ratio of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 1:1; the total molar amount of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 43 mmol per 100 g of mixed solvent.

[0052] (2) Sedimentation process: 1 kg of water is placed in the treatment vessel and the stirring device is turned on. Then the viscous reaction liquid is transferred to the treatment vessel and the polymer in the viscous reaction liquid precipitates at the bottom of the treatment vessel.

[0053] (3) Reactor cleaning process: The viscous reaction liquid is discharged from the polymerization reactor, and the temperature inside the reactor is cooled to below 100℃. Then, the polymerization reactor is immediately rinsed with a rinsing medium. The specific process is as follows: The polymerization reactor is cooled to 80℃, and the polymer adhering to the inner surface of the polymerization reactor is rinsed using a cleaning device. The operating pressure of the cleaning device is set to 4MPa, the rinsing medium is 10℃ water, and the amount of rinsing medium used is 1kg. After cleaning, the cleaning liquid containing polymer is discharged from the polymerization reactor, and the polymerization reactor is purged with a hot air blower at a temperature of 120℃. After 1 hour, the inside of the polymerization reactor is dry.

[0054] (4) Crushing, washing and drying process: The precipitate obtained in step (2) precipitation process is mixed with the polymer obtained in step (3) washing process and then crushed. Then it is washed with water until the washing liquid is neutral. Then it is dried with hot nitrogen at 80℃ for 8 hours to obtain dried polybenzimidazole.

[0055] Steps (1)-(4) were repeated three times. The weight and solubility of the polybenzimidazole product obtained each time are shown in Table 1. A photograph of the polybenzimidazole obtained from the second polymerization in Example 1 after dissolution is shown below. Figure 1 As shown. By Figure 1 It can be seen that the polybenzimidazole is almost completely dissolved and has a darker color.

[0056] Example 2

[0057] (1) Polymerization process: First, methanesulfonic acid and phosphorus pentoxide (weight ratio 15:1, total weight 1600g) were added to the dissolving vessel and heated and stirred at 100℃ for 2h. Then, the mixed solvent of methanesulfonic acid and phosphorus pentoxide was fed into the polymerization vessel (volume 2L) through a conveying pipe and heated to 130℃ under nitrogen purging. Then, 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid were added to the polymerization vessel; the temperature was raised to 150℃, and the torque was recorded. After 4h, the torque increased by 1.2 times, and the reaction was terminated to obtain a viscous reaction liquid. The stirring speed was maintained at 80rpm throughout the reaction, and the atmosphere in the polymerization vessel was nitrogen. The molar ratio of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 1:1.2; the total molar amount of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 28 mmol per 100 g of mixed solvent.

[0058] (2) Sedimentation process: 1 kg of water is placed in the treatment vessel and the stirring device is turned on. Then the viscous reaction liquid is transferred to the treatment vessel and the polymer in the viscous reaction liquid precipitates at the bottom of the treatment vessel.

[0059] (3) Reactor cleaning process: The viscous reaction liquid is discharged from the polymerization reactor, and the temperature inside the polymerization reactor is cooled to below 100℃. Then, the polymerization reactor is immediately rinsed with rinsing medium. The specific process is as follows: The polymerization reactor is cooled to 70℃, and the polymer adhering to the inner surface of the polymerization reactor is rinsed using a cleaning device. The operating pressure of the cleaning device is set to 3MPa, the rinsing medium is water at 20℃, and the amount of rinsing medium used is 1.1kg. After cleaning, the cleaning liquid containing polymer is discharged from the polymerization reactor, and the polymerization reactor is purged with a hot air blower at 120℃. After 1 hour, the inside of the polymerization reactor is dry.

[0060] (4) Crushing, washing and drying process: The precipitate obtained in step (2) precipitation process is mixed with the polymer obtained in step (3) washing process and then crushed. Then it is washed with water until the washing liquid is neutral. Then it is dried with hot nitrogen at 80℃ for 8 hours to obtain dried polybenzimidazole.

[0061] Repeat steps (1)-(4) three times. The weight and solubility of the polybenzimidazole product obtained each time are shown in Table 1.

[0062] Example 3

[0063] The method was carried out according to Example 1, except that N,N-dimethylacetamide and water were used sequentially as rinsing media for cleaning; the amount of N,N-dimethylacetamide used was 0.1 kg, and the amount of water used was 0.6 kg; the operating pressure of the cleaning device was set to 1 MPa.

[0064] Example 4

[0065] The procedure was carried out according to Example 3, except that N,N-dimethylacetamide was replaced with an equal weight of dimethyl sulfoxide.

[0066] Example 5

[0067] The method was carried out according to Example 3, except that after the polymerization reactor was cooled to 70°C, N,N-dimethylacetamide was replaced with 0.6 kg of acetonitrile, and the operating pressure of the cleaning device was set to 4 MPa.

[0068] Comparative Example 1

[0069] The process was carried out according to the method of Example 1, except that the washing step (3) was not included. A photograph of the polybenzimidazole obtained from the second polymerization of Comparative Example 1 after dissolution is shown below. Figure 2 As shown. By Figure 2 It can be seen that there is a large amount of undissolved polybenzimidazole at the bottom of the flask, and the color is relatively light.

[0070] Table 1

[0071]

[0072]

[0073] As can be seen from Table 1, compared with Comparative Example 1, Examples 1-5 of this application ensured the solubility of polybenzimidazole produced in different batches by adding a washing tank process, and obtained polybenzimidazole with uniform performance and high solubility.

[0074] Table 2 shows the total amount of rinsing medium used in a single washing vessel and the operating pressure of the cleaning device in Examples 1-5 and Comparative Example 1.

[0075] Table 2

[0076]

[0077]

[0078] As shown in Table 2, compared with Examples 1-2, Examples 3-4 use N,N-dimethylacetamide and water or dimethyl sulfoxide and water as rinsing media, which can save solvent consumption in the washing vessel and reduce the operating pressure of the cleaning device without affecting the solubility of the product. In Example 5, acetonitrile and water are used as rinsing media. Although this also reduces the loss of polybenzimidazole without affecting its solubility, Example 5 requires a larger amount of rinsing media.

[0079] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for the continuous production of polybenzimidazole using solution polymerization, characterized in that, The method includes the following steps: (1) Under solution polymerization conditions, an aromatic component containing at least four amino groups and an aromatic or aliphatic component containing at least two carboxyl groups are polymerized in a reactor to obtain a viscous reaction solution; (2) Discharge the viscous reaction liquid from the reactor, and then rinse the reactor with a rinsing medium. The rinsing medium is first N,N-dimethylacetamide or dimethyl sulfoxide, and then water. The weight ratio of N,N-dimethylacetamide to water is 0.05-0.5:1; the weight ratio of dimethyl sulfoxide to water is 0.05-0.5:

1. The process of repeating steps (1) and (2) alternates between polymerization and rinsing. The flushing is carried out under pressure, with a pressure of 0.1 MPa-6 MPa. The amount of the flushing medium used is 0.4-3 kg relative to a reactor with a volume of 2 L.

2. The method according to claim 1, wherein, The rinsing is carried out under pressure, with a pressure of 1MPa-5MPa.

3. The method according to claim 1, wherein, The temperature of the rinsing medium is 10-80℃.

4. The method according to claim 1, wherein, The temperature of the rinsing medium is 10-50℃.

5. The method according to claim 1, wherein, The amount of the flushing medium used is 0.6-1.5 kg relative to a reactor with a volume of 2 L.

6. The method according to claim 1, wherein, Step (2) also includes drying the reactor.

7. The method according to claim 6, wherein, The drying method is at least one of hot nitrogen purging drying, hot air purging drying, and dryer drying.

8. The method according to claim 1, wherein, The method further includes sequentially precipitating, pulverizing, washing and drying the viscous reaction solution to obtain the polybenzimidazole product.

9. The method according to claim 8, wherein, The polymer obtained after precipitation is mixed with the polymer obtained from rinsing in step (2) and then crushed, washed and dried.

10. The method according to claim 1, wherein, The solvent used in the solution polymerization process is a mixture of phosphorus pentoxide and methanesulfonic acid and / or polyphosphoric acid.

11. The method according to claim 10, wherein, The weight ratio of methanesulfonic acid to phosphorus pentoxide is 10-50:

1.

12. The method according to claim 10, wherein, The total amount of the aromatic component containing at least four amino groups and the aromatic or aliphatic component containing at least two carboxyl groups per 100g of the solvent is 1-160 mmol.

13. The method according to claim 12, wherein, The total amount of the aromatic component containing at least four amino groups and the aromatic or aliphatic component containing at least two carboxyl groups per 100g of the solvent is 1.5-60 mmol.

14. The method according to claim 1, wherein, The molar ratio of an aromatic component containing at least four amino groups to an aromatic or aliphatic component containing at least two carboxyl groups is 1:0.6-2.

15. The method according to claim 14, wherein, The molar ratio of an aromatic component containing at least four amino groups to an aromatic or aliphatic component containing at least two carboxyl groups is 1:0.7-1.5.

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