Method for producing polybenzimidazole

Abstract

The invention relates to the technical field of polybenzimidazole, and discloses a method for producing polybenzimidazole, which comprises the following steps: (1) under a polymerization reaction condition, in an inactive atmosphere, carrying out a reaction to obtain polybenzimidazole; polymerizing an aromatic component containing at least two groups of ortho-amino groups and an aromatic or aliphatic component containing at least two carboxyl groups to obtain a mixed solution containing a polymerization product; and (2) gradually contacting the mixed solution containing the polymerization product with a precipitant to obtain a waste liquid and a precipitate, and controlling the diameter of a single beam of the mixed solution containing the polymerization product to be 0.1-2.5 cm. By adopting the method disclosed by the invention, the polybenzimidazole product with high molecular weight and good solubility can be prepared on a large scale.

Description

Technical Field

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

[0002] Polybenzimidazole (PBI) is a type of aromatic heterocyclic polymer containing repeating structural units of benzimidazole in the main chain. It is a special engineering plastic with excellent comprehensive performance, excellent high temperature resistance, chemical stability and mechanical properties. It can be used at a temperature of 375°C for a long time, has excellent mechanical strength, and also has excellent flame retardancy, radiation stability, mechanical stability, electrical insulation, chemical stability, thermal stability, antioxidant stability, toughness, adhesion, hygroscopicity and other properties. It can be used in extremely high temperatures, harsh chemical and plasma environments, or in application environments that require high durability and wear resistance of the product. It can be used as structural engineering materials, thermal insulation materials, electrical insulation materials, structural adhesives, fibers, cloths, permeable membranes, fuel cell high-temperature proton exchange membranes, etc., and is widely used in aerospace (radar antenna covers, fairings and tail wings of supersonic aircraft, burn-resistant coatings, radiation-resistant materials for spacecraft, heat-resistant and fire-proof materials for aerospace sealed cabins, space suits, aircraft interior decoration materials, seat flame retardant layers, fighter parachutes), fire retardant (fire suits, fire retardant coatings), semiconductors (printed circuit boards, C-class electrical insulation materials and FPC substrates in the field of microelectronics, as well as semiconductor interlayer insulation materials, flat panel display manufacturing, next-generation connection plugs, switches), industrial fields (competent for bearings, sleeves, rollers, slide rails and high-temperature contacts of incandescent or fluorescent lamps, such as vacuum cups, push fingers and retainers, electrical contactors, etc.), high-temperature fuel cells (proton exchange membranes), gas-liquid separation (seawater purification, gas separation) and other fields.

[0003] The synthesis of polybenzimidazole materials mainly includes melt polymerization and solution polymerization. Among them, melt polycondensation requires a higher temperature, the reaction conditions are relatively harsh, and the product molecular weight is relatively low. In addition, side reactions are prone to gel formation at high temperatures, resulting in poor product solubility and difficulty in processing.

[0004] Solution polymerization is more conducive to the preparation of high molecular weight polybenzimidazole, and its applicable monomer range is also wider, which is conducive to the preparation of functional polybenzimidazole materials. However, solution polymerization usually uses acidic solvents such as polyphosphoric acid and methanesulfonic acid, which are highly corrosive at reaction temperatures. In addition, the solid content of solution polymerization is low, and the acidic solvent wrapped in the product is difficult to remove quickly during post-processing, and the residual temperature inside the product is difficult to drop quickly, resulting in the occurrence of side reactions, resulting in a decrease in product quality, reduced solubility, and difficulty in subsequent processing and utilization. Therefore, most solution polymerizations are currently in the laboratory research and development stage. Summary of the invention

[0005] In view of the problem that a large amount of solvent (reaction medium) is used in polybenzimidazole solution polymerization, the solvent is wrapped in the polymerization product during the post-treatment process and is difficult to be quickly removed, and the residual heat of reaction is difficult to quickly reduce, resulting in a high content of insoluble matter in the product and reduced product quality. The purpose of the present invention is to provide a method for producing polybenzimidazole, which is conducive to quickly removing the solvent in the polybenzimidazole and taking away the residual heat of reaction, so as to obtain a polybenzimidazole product with high molecular weight and good solubility. The use of this method is conducive to the industrialization of the polybenzimidazole solution polymerization process.

[0006] A large amount of acidic solvent is used in the solution polymerization of polybenzimidazole. Compared with the precipitant, polybenzimidazole and the acidic solvent have better interaction force. Therefore, during post-treatment, the acidic solvent is very easy to remain, resulting in the quality of the polybenzimidazole product being reduced and the solubility being reduced. Especially in the mass production process, if the acidic solvent cannot be effectively removed in the early stage of post-treatment and the system temperature cannot be quickly lowered, even if the polymer is crushed and then washed with a large amount of alkaline solution or water in the later stage, it will still lead to an increase in the content of insoluble products. The inventors of the present invention have found that by controlling the diameter of a single bundle of mixed solution containing the polymerization product when it enters the precipitant, the solvent acid in the polybenzimidazole product can be quickly and effectively removed in the early stage of post-treatment to obtain a polybenzimidazole product with good solubility. In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for producing polybenzimidazole, which comprises the following steps:

[0007] (1) under polymerization reaction conditions, in an inert atmosphere, polymerizing an aromatic component containing at least two groups of vicinal amino groups and an aromatic or aliphatic component containing at least two carboxyl groups to obtain a mixed solution containing a polymerization product;

[0008] (2) The mixed solution containing the polymerization product is gradually contacted with a precipitant to obtain a waste liquid and a precipitate, wherein the diameter of a single beam of the mixed solution containing the polymerization product is controlled to be 0.1-2.5 cm, preferably 0.2-1.5 cm.

[0009] The reason why the method of the present invention can obtain a polybenzimidazole product with good solubility is presumably because the heat of the system increases after the polymerization reaction is amplified. If it is not controlled to enter the precipitant, the polybenzimidazole in the outer layer will quickly cool and harden, and the polybenzimidazole material has a large mechanical strength, which will cause the acidic solvent to be wrapped by the polymer in the center. On the one hand, the acidic solvent and the polybenzimidazole interact strongly, and the slowly infiltrating precipitant is difficult to effectively remove the acidic solvent; on the other hand, when the heat in the center cannot be effectively released, the high internal residual temperature and the mixed components are also likely to cause side reactions, produce insoluble matter, and cause the solubility of the product to decrease. However, the present invention controls the diameter of the single-bundle polymerization product mixed solution when it contacts the precipitant, so that the polymer is precipitated more evenly, and a large amount of solvent and heat can be quickly taken away by water during precipitation, avoiding the accumulation of heat in the acidic solvent wrapped by the product, so that the obtained polybenzimidazole product has good solubility.

[0010] The second aspect of the present invention provides polybenzimidazole prepared by the method described above.

[0011] The method of the present invention can be used to prepare polybenzimidazole products with high molecular weight and good solubility in large quantities. The method of the present invention is applicable to a wide range of monomers, the method is simple, and functional polybenzimidazole with high solubility can be prepared. DETAILED DESCRIPTION

[0012] 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.

[0013] In the present invention, unless otherwise specified, pressure is absolute pressure.

[0014] A first aspect of the present invention provides a method for producing polybenzimidazole, the method comprising the following steps:

[0015] (1) under polymerization reaction conditions, in an inert atmosphere, polymerizing an aromatic component containing at least two groups of vicinal amino groups and an aromatic or aliphatic component containing at least two carboxyl groups to obtain a mixed solution containing a polymerization product;

[0016] (2) The mixed solution containing the polymerization product is gradually contacted with a precipitant to obtain a waste liquid and a precipitate, wherein the diameter of a single beam of the mixed solution containing the polymerization product is controlled to be 0.1-2.5 cm, preferably 0.2-1.5 cm.

[0017] In the present invention, when the viscosity of the mixed solution containing the polymerization product is relatively low, the mixed solution containing the polymerization product can gradually contact the precipitant by gravity. When the viscosity of the mixed solution containing the polymerization product is relatively high, in order to enable the mixed solution containing the polymerization product to be discharged smoothly, preferably, a certain pressure (e.g., a pressure of 0.2-1 MPa) can be applied to the reaction kettle (polymerization kettle), for example, by pumping or ventilating to discharge the mixture at a certain pressure, so as to achieve the purpose of pressurization, thereby enabling the mixed solution containing the polymerization product to be discharged quickly.

[0018] According to the present invention, the discharge port of the reactor can be designed as a sieve plate or a showerhead type discharge port. Preferably, the number of beams of the mixed solution containing the polymerization product contacting the precipitant is 1-30.

[0019] According to the present invention, preferably, the precipitant is water and / or an alkaline aqueous solution. More preferably, the alkaline aqueous solution is at least one of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkaline earth metal hydroxide, an aqueous solution of an alkali metal salt, an aqueous solution of an alkaline earth metal salt, and aqueous ammonia; further preferably, it is at least one of aqueous ammonia, a saturated aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous sodium bicarbonate solution, an aqueous potassium bicarbonate solution, an aqueous magnesium carbonate solution, an aqueous sodium hydroxide solution, and an aqueous potassium hydroxide solution.

[0020] According to the present invention, preferably, the amount of the precipitant used is 0.1-10 kg, preferably 1-3 kg, per kg of the reaction medium.

[0021] According to the present invention, preferably, when the precipitant is an alkaline aqueous solution, the pH of the alkaline aqueous solution is ≤12.

[0022] According to the present invention, preferably, in order to better remove the solvent, the mixed solvent containing the polymer product is contacted with the precipitant under stirring conditions, and the stirring speed is 20-400 rpm, more preferably 40-200 rpm.

[0023] According to the present invention, preferably, the aromatic hydrocarbon component containing at least two groups of vicinal amino groups is an aromatic hydrocarbon tetraamine; more preferably, the aromatic hydrocarbon tetraamine contains 1-4 benzene rings; further preferably, the aromatic hydrocarbon tetraamine is selected from one or more of the following structures:

[0024]

[0025] Wherein, X is selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, substituted or unsubstituted alkylene group, for example, -O-, -S-,

[0026] According to the present invention, preferably, the aromatic or aliphatic component containing at least two carboxyl groups has a structure shown in formula (1):

[0027]

[0028] 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.); Y is hydrogen or an aryl group;

[0029] More preferably, the aromatic or aliphatic component containing at least two carboxyl groups is selected from one or more of the following structures:

[0030]

[0031] According to the present invention, preferably, the molar ratio of the aromatic component containing at least two groups of ortho-amino groups to the aromatic or aliphatic component containing at least two carboxyl groups is 1:0.8-1.2, more preferably 1:0.95-1.05.

[0032] According to the present invention, preferably, the polymerization reaction conditions include carrying out the polymerization reaction in the presence of a reaction medium, and the total molar amount of an aromatic component containing at least two groups of vicinal amino groups and an aromatic or aliphatic component containing at least two carboxyl groups is 1-160 mmol, preferably 2-100 mmol, per 100 g of the reaction medium.

[0033] According to the present invention, preferably, the reaction medium is a mixed solution of methanesulfonic acid and phosphorus pentoxide or polyphosphoric acid, wherein the mass ratio of methanesulfonic acid to phosphorus pentoxide is 6-16:1, more preferably 8-12:1.

[0034] According to the present invention, the polymerization conditions may be the conditions of solution polymerization commonly used in the art. Preferably, the polymerization conditions include: a temperature of 80-240° C. and a time of 0.25-72 h. More preferably, the polymerization conditions include: first reacting at 100-160° C. for 0.5-4 h, then heating to 120-220° C. for polymerization for 1-24 h. The above polymerization conditions can be used to obtain functional polybenzimidazole with higher molecular weight and less by-products.

[0035] According to the present invention, in order to make the reaction monomers contact more fully and improve the uniformity of the polymerization reaction, preferably, the polymerization is carried out under stirring, and the stirring speed is 20-400 rpm, more preferably 40-200 rpm.

[0036] According to the present invention, in order to further remove the acidic solvent and ions on the surface of the precipitate, preferably, the method further comprises washing the precipitate with an alkaline solution and / or water; more preferably, the alkaline solution is selected from at least one of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkaline earth metal hydroxide, an aqueous solution of an alkali metal salt, an aqueous solution of an alkaline earth metal salt and aqueous ammonia; further preferably, it is at least one of aqueous ammonia, an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous sodium bicarbonate solution, an aqueous potassium bicarbonate solution, an aqueous magnesium carbonate solution, an aqueous sodium hydroxide solution and an aqueous potassium hydroxide solution.

[0037] According to the present invention, preferably, the mass fraction of the alkaline solution used in the washing process is 0.1-60 wt %.

[0038] In the present invention, the number of washings is not particularly limited, and the number of washings with the alkaline solution can be multiple times, for example, 1-2 times. Preferably, the amount of the alkaline solution used during the washing process is such that the pH of the waste liquid generated by the last alkaline solution washing is 7-8.

[0039] In the present invention, the number of water washings can be 1 to 3. Preferably, the amount of water used during the washing process is such that the pH of the waste liquid generated by the last water washing is 7 to 8.

[0040] According to the present invention, in order to better remove the ions or acidic solvent adsorbed on the polymer surface, preferably, the method further comprises crushing the precipitate after washing with the alkaline solution and then washing with water. The crushing and then washing with water can further remove the residual acidic solvent.

[0041] According to the present invention, preferably, the method further comprises drying the washed precipitate at a temperature of 60-100° C.; more preferably, the drying is performed at 0.01-0.1 MPa and / or in an inert atmosphere.

[0042] In the present invention, the inert atmosphere during the polymerization and drying process is not particularly limited, and may be any inert atmosphere commonly used in the art. The inert atmosphere may be provided by an inert gas and / or nitrogen; the inert gas may be at least one of helium, neon, argon, krypton, xenon and radon.

[0043] The second aspect of the present invention provides polybenzimidazole prepared by the method described above.

[0044] The present invention will be described in detail below by way of examples. In the following examples,

[0045] The raw materials used are all commercially available.

[0046] Example 1

[0047] (1) The reaction medium (methanesulfonic acid and phosphorus pentoxide) and the reaction monomers 3,3-diaminobenzidine (0.2 mol) and 4,4-dicarboxydiphenyl ether (0.2 mol) are fed into a polymerization reactor through a feed pipeline. Under a nitrogen atmosphere, the stirring speed is 100 rpm, the mixture is stirred at 120° C. for 30 min, the temperature is raised to 140° C. and the reaction is continued for 4 h to obtain a viscous polymerization reaction solution; wherein the total weight of methanesulfonic acid and phosphorus pentoxide is 1.5 kg, and the weight ratio of methanesulfonic acid to phosphorus pentoxide is 10:1.

[0048] (2) Add precipitant (water, 2.4 kg) from the top of the precipitation kettle, and control the feed diameter and feed bundle number of the viscous polymerization reaction solution through the feed controller on the top. Under stirring, the stirring speed is 80 rpm, so that it gradually contacts with the precipitant to obtain precipitate and waste liquid; wherein, the N2 pressure in the polymerization kettle is adjusted to 0.2 MPa, the diameter of a single bundle of polymerization reaction solution when contacting water is controlled to be 0.4 cm-0.5 cm, and the number of feed bundles is 1. The upper waste liquid after precipitation is discharged from the side wall outlet of the precipitation kettle and enters the first waste liquid storage tank.

[0049] (3) 2.67 kg of potassium carbonate solution (10 wt%) is added from the top of the precipitation kettle to wash the precipitate, and the generated waste liquid (pH 7.5) is discharged through the pipeline on the side wall of the precipitation kettle into the second waste liquid storage tank. The neutralized product enters the pulverizer from the bottom discharge port and is crushed, and then enters the treatment kettle. Water is added to the top feed port of the treatment kettle to continue washing until it is neutral. After washing, the waste liquid is discharged from the side wall to the second waste liquid storage tank. The washed product enters the dryer under a nitrogen atmosphere and is dried at 0.01 MPa and 80°C to obtain the product.

[0050] Example 2

[0051] The method of Example 1 is followed, except that in step (2), the diameter of the viscous mixed solution containing the polymerization product when entering the precipitant is controlled to be 1.0 cm-1.5 cm.

[0052] Example 3

[0053] The method of Example 1 is followed, except that in step (2), the diameter of the viscous mixed solution containing the polymerization product is controlled to be 0.25 cm-0.35 cm when entering the precipitant.

[0054] Example 4

[0055] The method of Example 1 is followed, except that in step (1), the reaction time is 2 h; and in step (2), the diameter of the viscous mixed solution containing the polymer product when entering the precipitant is controlled to be 0.7 cm-1.0 cm.

[0056] Example 5

[0057] The method of Example 4 was followed, except that in step (1), the reaction medium was 1.65 kg of polyphosphoric acid, the temperature was raised to 200° C. and the reaction was continued for 1.5 h; in step (3), the amount of potassium carbonate aqueous solution used was 3.34 kg.

[0058] Example 6

[0059] The polymerization reaction was carried out according to the method in Example 1, except that in step (1), when the viscous mixed solution containing the polymerization product entered the precipitation reactor, the diameter of a single beam of the polymer solution when entering the precipitant was controlled to be 2 cm-2.5 cm.

[0060] Comparative Example 1

[0061] The method of Example 1 is followed, except that in step (1), the diameter of the viscous mixed solution containing the polymerization product is controlled to be 2.5 cm-3.0 cm when entering the precipitant.

[0062] Comparative Example 2

[0063] The polymerization reaction was carried out according to the method in Example 4, except that in step (1), no control was performed when the viscous mixed solution containing the polymerization product entered the precipitation tank (the diameter of a single strand of the polymer solution when entering the precipitant was >3 cm). Due to the high density of the precipitate, a large amount of the mixed solution containing the polymerization product precipitated at the bottom of the precipitation tank in a short period of time. The high temperature caused the precipitates to aggregate to form large lumps, and the product could not be discharged from the bottom discharge port.

[0064] The product was physically crushed, taken out and cleaned, and then the intrinsic viscosity and insoluble content were tested. After the product was dissolved in sulfuric acid, there were still insolubles, and the Ubbelohde viscosity measurement method had a large error.

[0065] Test Case

[0066] (1) The intrinsic viscosity of polybenzimidazole (which can reflect the molecular weight) is obtained by the Ubbelohde viscosity method: PBI powder is dissolved in concentrated sulfuric acid (98wt%) to prepare a sulfuric acid solution with a concentration of 0.6g / dL. The sulfuric acid solution is added to an Ubbelohde viscometer with a capillary inner diameter of 1.0-1.1mm, and stabilized in a constant temperature water bath at 25°C for 30 minutes. The outflow time of the measured solution is recorded as t1, the outflow time of concentrated sulfuric acid is recorded as t0, and the concentration of the polymer solution is recorded as C. The intrinsic viscosity of PBI is calculated according to Formula 1 and Formula 2.

[0067] Increased viscosity

[0068] Intrinsic viscosity

[0069] (2) Insoluble matter content of polybenzimidazole solution: 0.2 g of polybenzimidazole product and 9.8 g of dimethyl sulfoxide (DMSO) were added to a flask, dissolved at 80°C for 12 hours and then centrifuged. After separating the upper clear solution, the mass of the residual filter residue was weighed. The percentage of the residual filter residue to the total mass of the solution was the insoluble matter content.

[0070] The test results of the intrinsic viscosity and insoluble content of the final product S12 are shown in Table 1.

[0071] Table 1

[0072]

[0073]

[0074] From the results in Table 1, it can be seen that Examples 1-6, which use the present invention to control the viscous mixed solution containing the polymer product to slowly contact with the precipitant, have lower insoluble matter content (within 10%), better solubility of the polybenzimidazole product, and significantly better product quality.

[0075] 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 producing polybenzimidazole, characterized in that: The method comprises the following steps: (1) under polymerization reaction conditions, in an inert atmosphere, polymerizing an aromatic component containing at least two groups of vicinal amino groups and an aromatic or aliphatic component containing at least two carboxyl groups to obtain a mixed solution containing a polymerization product; (2) The mixed solution containing the polymerization product is gradually contacted with a precipitant to obtain a waste liquid and a precipitate, wherein the diameter of a single beam of the mixed solution containing the polymerization product is controlled to be 0.1-2.5 cm, preferably 0.2-1.5 cm.

2. The method according to claim 1, wherein: The precipitant is water and / or an alkaline aqueous solution; And / or, the mixed solution containing the polymerization product is divided into 1-30 bundles and then gradually contacted with the precipitant.

3. The method according to claim 1, wherein: The aromatic hydrocarbon component containing at least two groups of adjacent amino groups is an aromatic hydrocarbon tetraamine; Preferably, the aromatic tetraamine contains 1 to 4 benzene rings; More preferably, the aromatic tetraamine is selected from one or more of the following structures: Wherein, X is selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, and a substituted or unsubstituted alkylene group.

4. The method according to claim 1, wherein: The aromatic or aliphatic component containing at least two carboxyl groups has a structure shown in formula (1): Wherein, R is selected from an aromatic hydrocarbon ring, an aromatic heterocycle or a hydrocarbon group; and Y is hydrogen or an aromatic group.

5. The method according to claim 1, wherein: The molar ratio of the aromatic component containing at least two groups of vicinal amino groups to the aromatic or aliphatic component containing at least two carboxyl groups is 1:0.8-1.2; The polymerization reaction conditions include carrying out the polymerization reaction in the presence of a reaction medium, wherein the total molar amount of an aromatic component containing at least four amine groups and an aromatic or aliphatic component containing at least two carboxyl groups is 1-160 mmol, preferably 2-100 mmol, per 100 g of the reaction medium.

6. The method according to claim 5, wherein: The reaction medium is a mixed solution of methanesulfonic acid and phosphorus pentoxide or polyphosphoric acid, wherein the mass ratio of methanesulfonic acid to phosphorus pentoxide is 6-16:1, preferably 8-12:

1.

7. The method according to claim 1, wherein: The polymerization temperature is 80-240° C., and the polymerization time is 0.25-72 h; And / or, the polymerization is carried out under stirring, and the stirring speed is 50-300 rpm, preferably 80-200 rpm.

8. The method according to claim 1, wherein: The method further comprises washing the precipitate with an alkaline solution and / or water; Preferably, the alkaline solution is selected from at least one of aqueous ammonia, aqueous sodium carbonate solution, aqueous potassium carbonate solution, aqueous sodium bicarbonate solution, aqueous potassium bicarbonate solution, aqueous magnesium carbonate solution, aqueous sodium hydroxide solution and aqueous potassium hydroxide solution.

9. The method according to claim 8, wherein: The method further comprises crushing the precipitate after washing with the alkaline solution and then washing with water; And / or, the method further comprises drying the washed precipitate at a temperature of 60-100° C.; Preferably, the drying is performed at 0.01-0.1 MPa and / or in an inert atmosphere.

10. The polybenzimidazole prepared by the method according to any one of claims 1 to 9.

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