Method for continuously producing polybenzimidazole by utilizing solution polymerization method

Abstract

The invention relates to the field of polybenzimidazole, and discloses a method for continuously producing polybenzimidazole by utilizing a solution polymerization method, which comprises the following steps: (1) under a solution polymerization condition, adding a catalyst, the method comprises the following steps: polymerizing an aromatic hydrocarbon component containing at least four amino groups and an aromatic hydrocarbon or aliphatic component containing at least two carboxyl groups in a reactor to obtain a viscous reaction solution; (2) discharging the viscous reaction liquid in the reactor, and then flushing the reactor by using a flushing medium which is a polar solvent; the processes of the step (1) and the step (2) are cycled in this way, and the polymerization process and the washing process are alternately carried out. The method provided by the invention can avoid the problem of pipeline blockage, improve the yield, improve the solubility of the polymer, and improve the uniformity of the quality of products in each batch.

Description

Technical Field

[0001] The invention relates to the technical field of polybenzimidazole, and in particular to a method for continuously producing polybenzimidazole by solution polymerization. Background Art

[0002] Polybenzimidazole is a type of high molecular polymer containing benzimidazole groups in the repeating unit, and is also a type of special engineering plastic with excellent performance. It has excellent high temperature resistance, corrosion resistance, high mechanical strength, high hardness, and high wear resistance. It can be used in extremely high temperature, harsh chemical and plasma environments. It is currently widely used in high temperature proton exchange membranes, heat-resistant fibers, cut-resistant fibers, gas-liquid separation, fire retardant and aerospace fields. There are four main methods for the synthesis of polybenzimidazole: parent method, nucleophilic substitution method, melt polymerization method and solution polymerization method. However, the parent method and nucleophilic substitution method are limited by harsh experimental conditions, which limits their wide range of applications. The commonly used methods are melt polymerization method and solution polymerization method.

[0003] Compared with the melt polymerization method, the solution polymerization method has the advantages of mild reaction conditions, low energy consumption (low reaction temperature), green byproducts (the byproduct of solution polymerization is water, while the byproducts of melt polymer are mostly toxic substances such as phenol), etc., and has broad industrial application value. However, the preparation of polybenzimidazole using the solution polymerization method is mostly in the laboratory preparation stage and lacks large-scale industrial application.

[0004] The glass transition temperature of polybenzimidazole is relatively high, which affects its processing performance. Improving the solubility of polybenzimidazole in the solvent can improve its processing performance. During the solution polymerization production process, especially in continuous production, the material residue in the reactor affects the uniformity of the next batch of materials, which in turn affects the reaction process, resulting in reduced product solubility or yield, which seriously affects the quality of the product. Summary of the invention

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

[0006] In order to achieve the above object, the present invention provides a method for continuously producing polybenzimidazole by 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) discharging the viscous reaction liquid in the reactor, and then flushing the reactor with a flushing medium, wherein the flushing medium is a polar solvent;

[0009] The process of step (1) and step (2) is repeated in this way to realize the alternation of polymerization process and flushing process.

[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 problems, improve yield, improve the solubility of the polymer, and improve the uniformity of product quality in each batch;

[0012] (2) The preferred implementation method 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Figure 2 This is a photograph of the polybenzimidazole prepared by the second polymerization in Comparative Example 1 after dissolution. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The present invention provides a method for continuously producing polybenzimidazole by 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) discharging the viscous reaction liquid in the reactor, and then flushing the reactor with a flushing medium, wherein the flushing medium is a polar solvent;

[0019] The process of step (1) and step (2) is repeated in this way to realize the alternation of polymerization process and flushing process.

[0020] According to the present invention, the flushing medium can be a common polar solvent in the art. Preferably, the flushing medium includes at least one of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile and water. During the flushing process, a single solvent can be used for flushing, for example, water is used as a flushing medium to flush the reactor; multiple solvents can also be used for flushing, for example, an organic polar solvent and water are used as flushing media to flush the reactor. More preferably, the flushing medium includes water and at least one selected from methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone. According to the preferred embodiment of the present invention, at least one of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone is first used for flushing, and then water is used for flushing, which can not only reduce the amount of flushing medium water, but also reduce the flushing pressure.

[0021] According to a particularly preferred embodiment of the present invention, the flushing medium is N,N-dimethylacetamide and water, 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 sticking to the inner surface of the reactor, preferably, the flushing adopts a pressure flushing method, and the pressure of the pressure flushing is 0.1MPa-6MPa, and more preferably 1MPa-5MPa. In the present invention, the pressure flushing is carried out by a pressure cleaning device (such as a high-pressure water gun), and the pressure of the pressure flushing is the operating pressure set by the pressure cleaning device. In the present invention, unless otherwise specified, the pressure is a gauge pressure.

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

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

[0025] In the present invention, the reactor for carrying out the polymerization reaction can be a commonly used polymerization reactor in the art, for example, a kettle reactor (reactor), a tubular reactor (reaction tube), a tower reactor, etc., as long as the reactor can meet the requirements of the polymerization reaction. Usually, the reactor is provided with a temperature monitoring device and a stirring device, etc.

[0026] According to the present invention, in order to avoid the influence of the residual flushing medium on the subsequent polymerization reaction, preferably, step (2) also includes drying the reactor. The drying can be hot nitrogen purge drying, hot air purge drying, 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 flushing effect, preferably, after the viscous reaction liquid is discharged, the temperature in the reactor is cooled to below 100° C. (preferably 60-90° C.), and then the reactor is immediately flushed with a flushing medium.

[0028] According to the present invention, preferably, the method further comprises sequentially precipitating, crushing, washing and drying the viscous reaction liquid to obtain the polybenzimidazole product.

[0029] According to the present invention, preferably, the precipitation process comprises: transferring the viscous reaction liquid to a treatment kettle containing a precipitant (e.g., water), and allowing the polymer in the viscous reaction liquid to precipitate or separate out in the precipitant under stirring. After precipitation, solid-liquid separation is performed to obtain a polymer, and then the polymer is crushed, washed, and dried in sequence.

[0030] According to the present invention, preferably, the polymer obtained after precipitation is mixed with the polymer obtained by washing 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 kettle 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, per 100 g of the solvent.

[0034] According to the present invention, preferably, the aromatic hydrocarbon component containing at least four amino groups is an aromatic hydrocarbon tetraamine; more preferably, the aromatic hydrocarbon tetraamine contains no less than 1 benzene ring; further preferably, the aromatic hydrocarbon 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 a structure shown in formula (1):

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

[0039] Wherein, R is selected from an aromatic hydrocarbon ring, an aromatic heterocyclic ring or a hydrocarbon group (e.g., a chain alkane group, a cycloalkane group, an alkene group, 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] Among them, 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; preferably 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 hours at an oxygen content of no more than 20 ppm (more preferably, the oxygen content is no more than 8 ppm, for example, in 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 a solvent, heating to 60-220° C. for 2-48 hours. The reactor heating method is preferably heat transfer oil circulation heating.

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

[0046] According to the present invention, preferably, the entire polymerization reaction is carried out under stirring at a 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 by way of examples. In the following examples,

[0048] The raw materials used are all commercially available products.

[0049] The solubility test method of the polybenzimidazole product is to add 0.4g of polybenzimidazole to 8g of anhydrous N,N-dimethylacetamide (DMAc) solution, and heat the solution in a metal bath at 80°C for 4 hours. After heating, filter and weigh the residue, i.e., the mass of insoluble matter, to calculate the solubility of the polybenzimidazole.

[0050] Example 1

[0051] (1) Polymerization process: First, add methanesulfonic acid and phosphorus pentoxide (weight ratio of 12:1, total weight of 1600g) to the dissolving kettle, and heat and stir at 80℃ for 4h. Then, the mixed solvent of methanesulfonic acid and phosphorus pentoxide is sent to the polymerization kettle (volume of 2L) through the delivery pipeline, and the temperature is raised to 120℃ under nitrogen purge. Then, 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid are added to the polymerization kettle; the temperature is raised to 140℃, and the torque is recorded. After 5h, the torque increases by 1.2 times, and the reaction is terminated to obtain a viscous reaction liquid. The stirring speed is kept at 100rpm throughout the reaction, and the atmosphere of the polymerization kettle is nitrogen atmosphere. The molar ratio of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 1:1; and the total molar number of 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid is 43 mmol per 100 g of the mixed solvent.

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

[0053] (3) Tank washing process: the viscous reaction liquid is discharged from the polymerization kettle, the temperature inside the polymerization kettle is cooled to below 100°C, and then the polymerization kettle is immediately washed with a washing medium. The specific process is as follows: the polymerization kettle is cooled to 80°C, and the polymer sticking to the inner surface of the polymerization kettle is washed with a washing device. The operating pressure of the washing device is set to 4MPa, the washing medium is 10°C water, and the amount of the washing medium is 1kg. After the washing is completed, the washing liquid containing the polymer is discharged from the polymerization kettle, and the polymerization kettle is purged with a hot air blower at a temperature of 120°C. After 1 hour, the polymerization kettle is in a dry state.

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

[0055] The process of steps (1) to (4) was repeated 3 times. The weight and solubility of the polybenzimidazole product obtained each time are shown in Table 1. Figure 1 As shown. 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, add methanesulfonic acid and phosphorus pentoxide (weight ratio of 15:1, total weight of 1600g) to the dissolving kettle, and heat and stir at 100℃ for 2h. Then, the mixed solvent of methanesulfonic acid and phosphorus pentoxide is sent to the polymerization kettle (volume of 2L) through the delivery pipeline, and the temperature is raised to 130℃ under nitrogen purge. Then, 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid are added to the polymerization kettle; the temperature is raised to 150℃, and the torque is recorded. After 4h, the torque increases by 1.2 times, and the reaction is terminated to obtain a viscous reaction liquid. The stirring speed is kept at 80rpm throughout the reaction, and the atmosphere of the polymerization kettle is nitrogen atmosphere. The molar ratio of 3,3′,4,4′-tetraaminobiphenyl to 4,4′-diphenyl ether dicarboxylic acid is 1:1.2; and the total molar number of 3,3′,4,4′-tetraaminobiphenyl and 4,4′-diphenyl ether dicarboxylic acid is 28 mmol per 100 g of the mixed solvent.

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

[0059] (3) Tank washing process: the viscous reaction liquid is discharged from the polymerization kettle, the temperature inside the polymerization kettle is cooled to below 100°C, and then the polymerization kettle is immediately washed with a flushing medium. The specific process is as follows: the polymerization kettle is cooled to 70°C, and the polymer sticking to the inner surface of the polymerization kettle is washed with a cleaning device. The operating pressure of the cleaning device is set to 3MPa, the flushing medium is 20°C water, and the amount of flushing medium is 1.1kg. After the cleaning is completed, the cleaning liquid containing the polymer is discharged from the polymerization kettle, and the polymerization kettle is purged with a hot air blower at a temperature of 120°C. After 1 hour, the polymerization kettle is in a dry state.

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

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

[0062] Example 3

[0063] The method of Example 1 was followed, except that N,N-dimethylacetamide and water were used as flushing media in sequence 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 method of Example 3 was followed, except that N,N-dimethylacetamide was replaced with an equal weight of dimethyl sulfoxide.

[0066] Example 5

[0067] The method of Example 3 was followed, except that after the polymerization kettle 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 method of Example 1 was followed, except that the kettle washing step (3) was not included. The photo of the polybenzimidazole prepared by the second polymerization in Comparative Example 1 after dissolution is shown in FIG. Figure 2 As shown. 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 lighter.

[0070] Table 1

[0071]

[0072]

[0073] It can be seen from Table 1 that, compared with Comparative Example 1, Examples 1-5 of the present application ensure the solubility of polybenzimidazole produced in different batches by adding a kettle washing process, thereby obtaining polybenzimidazole with uniform performance and high solubility.

[0074] The total amount of flushing medium used in a single kettle wash and the operating pressure of the cleaning device in Examples 1-5 and Comparative Example 1 are shown in Table 2.

[0075] Table 2

[0076]

[0077]

[0078] As can be seen from Table 2, compared with Examples 1-2, Examples 3-4 use N,N-dimethylacetamide and water or dimethyl sulfoxide and water as flushing media, which can save the amount of washing solvent 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 flushing media, which can also achieve the purpose of reducing the loss of polybenzimidazole without affecting its solubility, but Example 5 needs to consume a large amount of flushing medium.

[0079] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for continuously producing polybenzimidazole by solution polymerization, characterized in that: The method comprises 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) discharging the viscous reaction liquid in the reactor, and then flushing the reactor with a flushing medium, wherein the flushing medium is a polar solvent; The process of step (1) and step (2) is repeated in this way to realize the alternation of polymerization process and flushing process.

2. The method according to claim 1, wherein: The flushing medium comprises at least one of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile and water; Preferably, the flushing medium comprises water and at least one selected from the group consisting of methanesulfonic acid, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone and acetonitrile.

3. The method according to claim 1 or 2, wherein: The flushing is carried out by pressure flushing, and the pressure of the pressure flushing is 0.1MPa-6MPa, preferably 1MPa-5MPa.

4. The method according to claim 1 or 2, wherein: The temperature of the flushing medium is 10-80°C, preferably 10-50°C.

5. The method according to claim 1 or 2, wherein: Relative to a reactor with a volume of 2 L, the amount of the flushing medium used is 0.4-3 kg, preferably 0.6-1.5 kg.

6. The method according to claim 1 or 2, wherein: Step (2) also includes drying the reactor; Preferably, the drying method is at least one of hot nitrogen purge drying, hot air purge drying and dryer drying.

7. The method according to claim 1 or 2, wherein: The method further comprises sequentially precipitating, crushing, washing and drying the viscous reaction liquid to obtain a polybenzimidazole product.

8. The method according to claim 7, wherein: The polymer obtained after precipitation is mixed with the polymer obtained by washing in step (2) and then crushed, washed and dried.

9. The method according to claim 1 or 2, wherein: The solvent used in the solution polymerization process is a mixed solvent of phosphorus pentoxide and methanesulfonic acid and / or polyphosphoric acid; Preferably, the weight ratio of methanesulfonic acid to phosphorus pentoxide is 10-50:1; 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, per 100 g of the solvent.

10. The method according to claim 1 or 2, wherein: 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; preferably 1:0.7-1.5.

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