Method and system for producing polybenzimidazole

Abstract

The present invention relates to the technical field of polybenzimidazole, and discloses a polybenzimidazole production method and system, the system comprises: a polymerization unit used for carrying out a polymerization reaction on a reaction monomer to obtain a polybenzimidazole-containing reaction liquid; the precipitation unit is used for enabling the reaction liquid containing the polybenzimidazole to be in contact with a precipitator to separate out the polybenzimidazole; wherein a discharging control device is arranged in the polymerization unit or a feeding control device is arranged in the precipitation unit, and the discharging control device or the feeding control device is used for controlling the diameter of reaction liquid containing polybenzimidazole entering the precipitation unit. By adopting the system and 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, and in particular to a method and system 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 in extremely high temperature, harsh chemical and plasma environments, or in application environments that require high durability and wear resistance of products. It can be used as structural engineering materials, thermal insulation materials, electrical insulation materials, structural adhesives, fibers, cloths, permeable membranes, high-temperature proton exchange membranes for fuel cells, etc., and is widely used in aerospace, fire retardant, semiconductor, industrial fields, and emerging high-temperature fuel cells (proton exchange membranes), gas-liquid separation (seawater purification, gas separation) 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, it is difficult to control the reaction conditions of solution polymerization, and most of them are currently in the laboratory research and development stage, without mature pilot or industrial scale-up equipment and processes. In addition, due to the low solubility of monomers and products, acidic solvents such as polyphosphoric acid and methanesulfonic acid are usually used, the reaction temperature is relatively high, the system viscosity is large at the end of the reaction, the acidic solvent is difficult to remove quickly, and the residual heat of the reaction is difficult to decrease rapidly, resulting in an increase in the number of insoluble by-products of the product, a long cleaning process, and affecting the product quality. Summary of the invention

[0005] There is a lack of mature processes and devices for the solution polycondensation of polybenzimidazole. Conventional solution polymerization processes and devices are not suitable for polybenzimidazole systems, which can easily lead to problems such as difficulty in removing solvents, difficulty in reducing reaction waste heat, increased side reactions, difficulty in cleaning the polymerization products, and reduced product solubility. The purpose of the present invention is to provide a system and method for preparing polybenzimidazole. The system and method of the present invention can quickly remove the solvent from the product and quickly reduce the reaction waste heat after the polymerization of polybenzimidazole, thereby obtaining polybenzimidazole with good solubility and high molecular weight.

[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 reduced, even if the polymer is crushed and then washed with a large amount of alkaline solution or water in the later stage, the content of insoluble products will still increase. The inventors of the present invention have found that by improving the discharging device of the polymerization unit or the feeding device of the precipitation unit, the diameter of the reaction liquid containing polybenzimidazole when entering the precipitant can be controlled, the solvent in the system can be quickly removed in the early stage of post-treatment, and the residual heat of the system reaction can be taken away, the occurrence of side reactions can be reduced, and a polybenzimidazole product with good solubility can be obtained. In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a system for preparing polybenzimidazole, which comprises:

[0007] A polymerization unit, used to polymerize the reaction monomers to obtain a reaction solution containing polybenzimidazole;

[0008] A precipitation unit, used for contacting the reaction solution containing polybenzimidazole with a precipitant to precipitate polybenzimidazole (crude product);

[0009] Wherein, a discharge control device is provided in the polymerization unit or a feed control device is provided in the precipitation unit, and the discharge control device or the feed control device is used to control the diameter of the reaction liquid containing polybenzimidazole entering the precipitation unit.

[0010] The second aspect of the present invention provides a method for preparing polybenzimidazole using the above-mentioned system, which comprises: feeding the reaction monomer into a polymerization unit for polymerization reaction to obtain a reaction liquid containing polybenzimidazole; then feeding the reaction liquid containing polybenzimidazole into a precipitation unit to contact with a precipitant to obtain polybenzimidazole (crude product) and waste liquid.

[0011] The reason why the system and method of the present invention can obtain a polybenzimidazole product with good solubility is speculated to be 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 in the center by the polymer. On the one hand, the acidic solvent and 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 mixed components are also likely to cause side reactions, produce insoluble matter, and cause the solubility of the product to decrease. The present invention improves the discharging device of the polymerization unit or the feeding device of the precipitation unit, thereby controlling the diameter of the reaction liquid containing polybenzimidazole when entering the precipitant, so that the polymer is precipitated more evenly, avoiding the accumulation of heat by the wrapped acidic solvent, so that the obtained polybenzimidazole product has good solubility.

[0012] The system and 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 and can prepare functional polybenzimidazoles with high solubility. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a specific embodiment of a system for producing polybenzimidazole provided by the present invention.

[0014] Figure 2 It is a schematic diagram of a feed hole in a discharge control device or a feed control device provided by the present invention.

[0015] Description of Reference Numerals

[0016] V1 polymerization kettle V2 precipitation kettle V3 treatment kettle

[0017] V4 First waste liquid storage tank V5 Second waste liquid storage tank E1 crusher

[0018] E2 dryer S1 solvent and reaction monomer S2 reaction liquid containing polybenzimidazole

[0019] S3 precipitant S4 upper waste liquid after precipitation S5 alkaline washing liquid

[0020] S6 Alkaline washing waste liquid S7 Product to be crushed S8 Crushed product

[0021] S9 cleaning liquid S10 cleaning waste liquid S11 wet powder

[0022] S12 dried product DETAILED DESCRIPTION

[0023] 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.

[0024] In the present invention, unless otherwise specified, pressure is absolute pressure.

[0025] A first aspect of the present invention provides a system for preparing polybenzimidazole, the system comprising:

[0026] A polymerization unit, used to polymerize the reaction monomers to obtain a reaction solution containing polybenzimidazole;

[0027] A precipitation unit, used for contacting the reaction solution containing polybenzimidazole with a precipitant to precipitate polybenzimidazole (crude product);

[0028] Wherein, a discharge control device is provided in the polymerization unit or a feed control device is provided in the precipitation unit, and the discharge control device or the feed control device is used to control the diameter of the reaction liquid containing polybenzimidazole entering the precipitation unit.

[0029] In the present invention, usually, a feed control device is provided in the precipitation unit to control the diameter of the reaction liquid containing polybenzimidazole entering the precipitation unit. However, it can be understood that when the precipitation unit is located below the polymerization unit and the feed inlet of the precipitation unit is large (for example, the precipitation unit is an open precipitation tank), a discharge control device can be provided in the polymerization unit to control the diameter of the reaction liquid containing polybenzimidazole entering the precipitation unit.

[0030] According to the present invention, preferably, at least one discharge hole is provided in the discharge control device, and the diameter of the inscribed circle of the single discharge hole is 0.1-3 cm.

[0031] According to the present invention, preferably, at least one feed hole is provided in the feed control device, and the diameter of the inscribed circle of the single feed hole is 0.1-3 cm.

[0032] According to the present invention, preferably, 1-30 discharge holes are provided in the discharge control device.

[0033] According to the present invention, preferably, 1-30 feeding holes are provided in the feeding control device.

[0034] In the present invention, the discharge holes or the feed holes may be arranged in a matrix.

[0035] According to the present invention, in order to prevent the polybenzimidazole-containing reaction liquid from being entangled before entering the precipitant, preferably, the distance between two adjacent discharge holes in the discharge control device is 0.1-2 cm.

[0036] According to the present invention, in order to prevent the polybenzimidazole-containing reaction solution from being entangled before entering the precipitant, preferably, the distance between two adjacent feed ports in the feed control device is 0.1-2 cm.

[0037] In the present invention, the distance between two adjacent discharge holes or two adjacent feed ports refers to the shortest distance between the circumscribed circles of the two adjacent discharge holes or two adjacent feed ports.

[0038] In the present invention, the shape of the cross section of the discharge hole of the discharge control device or the feed hole of the feed control device is not particularly limited, and can be circular, triangular, rectangular, square, octagonal, cross-shaped, etc., preferably circular or elliptical.

[0039] According to the present invention, preferably, the polymerization unit comprises at least one polymerization kettle, preferably 1-2 polymerization kettles.

[0040] According to the present invention, preferably, the precipitation unit comprises at least one precipitation tank, preferably 1-2 precipitation tanks.

[0041] According to the present invention, preferably, a stirring device is provided in the precipitation tank.

[0042] According to the present invention, preferably, the system further comprises a pulverizing unit, and the pulverizing unit is used to pulverize the polybenzimidazole (crude product).

[0043] According to the present invention, preferably, the system further comprises a washing unit, and the washing unit is used to wash the crushed polybenzimidazole.

[0044] According to the present invention, preferably, the system further comprises a drying unit, and the drying unit is used to dry the washed polybenzimidazole.

[0045] According to the present invention, preferably, the waste liquid treatment unit comprises at least one waste liquid storage tank and / or buffer tank.

[0046] The second aspect of the present invention provides a method for preparing polybenzimidazole using the above-mentioned system, which comprises: feeding the reaction monomer into a polymerization unit for polymerization reaction to obtain a reaction liquid containing polybenzimidazole; then feeding the reaction liquid containing polybenzimidazole into a precipitation unit to contact with a precipitant to obtain polybenzimidazole (crude product) and waste liquid.

[0047] In the present invention, when the viscosity of the reaction solution containing polybenzimidazole is relatively low, the reaction solution containing polybenzimidazole can gradually contact with the precipitant by gravity. When the viscosity of the reaction solution containing polybenzimidazole is relatively high, in order to enable the reaction solution containing polybenzimidazole to be discharged smoothly, preferably, a certain pressure (for example, a pressure of 0.2-1 MPa) can be applied to the polymerization unit (polymerization kettle), for example, by pumping or ventilating to discharge the reaction solution under a certain pressure, so as to achieve the purpose of pressurization, thereby enabling the reaction solution containing polybenzimidazole to be discharged quickly.

[0048] 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.

[0049] 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.

[0050] According to the present invention, preferably, when the precipitant is an alkaline aqueous solution, the pH of the alkaline aqueous solution is ≤12.

[0051] According to the present invention, preferably, the precipitation is carried out under stirring conditions, and the stirring linear speed in the precipitation tank is 0.05-1 m / s, more preferably 0.1-0.5 m / s.

[0052] According to the present invention, in order to remove the acidic solvent and ions on the surface of the crude polybenzimidazole product 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.

[0053] According to the present invention, preferably, the mass fraction of the alkaline solution used in the washing process is 0.1-60 wt %.

[0054] In the present invention, the number of washings is not particularly limited, and the number of washings with the alkaline solution may be 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.

[0055] 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.

[0056] 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.

[0057] 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 0.001-0.1 MPa and / or in an inert atmosphere.

[0058] According to the present invention, the waste liquid is sent to the waste liquid storage tank of the waste liquid treatment unit for storage.

[0059] In the present invention, the method for obtaining the reaction solution containing polybenzimidazole may include: 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.

[0060] 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:

[0061]

[0062] Wherein, X is selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, substituted or unsubstituted alkylene group, for example,

[0063] According to the present invention, preferably, the aromatic or aliphatic component containing at least two carboxyl groups has a structure shown in formula (1):

[0064]

[0065] 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;

[0066] More preferably, the aromatic or aliphatic component containing at least two carboxyl groups is selected from one or more of the following structures:

[0067]

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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: temperature of 80-240°C and time of 0.25-72h. More preferably, the polymerization reaction includes a first stage and a second stage. The first stage: reaction at 100-160°C for 0.5-4h; the second stage: heating to 120-220°C for polymerization for 1-24h. The above polymerization conditions can be used to obtain functional polybenzimidazole with higher molecular weight and less by-products.

[0072] 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 linear speed is 0.05-1 m / s, more preferably 0.1-0.5 m / s.

[0073] 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.

[0074] The present invention will be described in detail below by way of examples. In the following examples,

[0075] The raw materials used are all commercially available products.

[0076] Example 1

[0077] Use Figure 1The system shown produces polybenzimidazole, and the system includes a polymerization kettle V1, a precipitation kettle V2, a crusher E1, a treatment kettle V3, and a dryer E2 connected in sequence. Under N2 atmosphere, the reaction medium and the reaction monomer S1 are fed into the polymerization kettle V1 through a feed pipeline for polymerization. The polymerization kettle V1 is provided with a stirring device and a temperature control probe. A feed control device is provided at the top of the precipitation kettle V2. The feed control device is provided with 5 circular feed holes. The inscribed circle diameter of a single feed hole is 0.5 cm, and the distance between two adjacent feed ports is 0.375 cm. The bottom outlet of the polymerization kettle V1 is connected to the feed control device at the top of the precipitation kettle V2, so that the mixed solution (viscous solution) containing the polymerization product and the precipitant gradually contact in the precipitation kettle V2. The bottom discharge port of the precipitation kettle V2 is connected to the crusher E1, and the precipitate is crushed by the crusher E1 and enters the treatment kettle V3. A feed port is provided at the top of the treatment kettle V3, and a discharge port provided at the bottom is connected to the dryer E2. The system is also provided with a first waste liquid storage tank V4 and a second waste liquid storage tank V5. The first waste liquid storage tank V4 is connected to the liquid outlet pipeline of the side wall of the precipitation tank V2, and is used to recover the waste acid liquid discharged from the precipitation tank V2; the second waste liquid storage tank V5 is connected to the liquid outlet pipeline of the side wall of the precipitation tank V2 and the treatment tank V3, and is used to recover the waste salt solution discharged from the precipitation tank V2 and the treatment tank V3.

[0078] (1) The reaction medium (methanesulfonic acid and phosphorus pentoxide) and the reaction monomers 3,3-diaminobenzidine (0.2 mol), 4,4-dicarboxydiphenyl ether (0.15 mol) and cyclohexanedicarboxylic acid (0.05 mol) are fed into a polymerization reactor V1 through a feed pipeline. Under a nitrogen atmosphere, the stirring line speed is 0.31 m / s, and the mixture is stirred at 100° C. for 30 min. The mixture is heated to 120° C. and the reaction is continued for 4 h to obtain a viscous polymerization reaction solution (S2); wherein the total weight of methanesulfonic acid and phosphorus pentoxide is 1.6 kg, and the weight ratio of methanesulfonic acid to phosphorus pentoxide is 11:1.

[0079] (2) A precipitant (water S3, 2.5 kg) is added from the top of the precipitation reactor V2, and the feed diameter of the viscous polymerization reaction solution is controlled by the feed control device on the top (the inscribed circle diameter of a single feed hole is 0.5 cm) and the number of feed beams is 5 (the number of circular feed holes is 5). The schematic diagram of the feed hole design is shown in FIG. Figure 2 (1). The N2 pressure in the polymerization reactor was adjusted to 0.5 MPa, and the stirring speed in the precipitation reactor was adjusted to 0.20 m / s, so that the reaction liquid gradually contacted with the precipitant to obtain precipitate and waste liquid. The upper waste liquid S4 after precipitation was discharged from the side wall outlet of the precipitation reactor V2 and entered the first waste liquid storage tank V4.

[0080] (3) 2.25 kg potassium carbonate solution (12 wt%) S5 is added from the top of the precipitation kettle V2 to clean the precipitate, and the generated waste liquid S6 (pH 7-8) is discharged through the pipeline on the side wall of the precipitation kettle into the second waste liquid storage tank V5. The neutralized product S7 enters the pulverizer E1 from the bottom discharge port and is crushed, and then enters the treatment kettle V3. Water S9 is added to the top feed port of the treatment kettle V3 to continue cleaning until it is neutral. After cleaning, the waste liquid S10 is discharged from the side wall to the second waste liquid storage tank V5. The cleaned product S11 enters the dryer E2 and is dried at 0.01 MPa and 80°C under a nitrogen atmosphere to obtain the product S12.

[0081] Example 2

[0082] The system and method of Example 1 are used, except that three circular feed holes are provided in the feed control device. The schematic diagram of the feed hole design is as shown in FIG. Figure 2 (2) As shown; the diameter of the inscribed circle of a single feed hole is 1 cm, and the distance between two adjacent feed holes is 0.5 cm.

[0083] Example 3

[0084] The system and method of Example 1 are used, except that the feed control device is provided with 5 circular feed holes of different sizes. The feed hole design schematic diagram is shown in FIG. Figure 2 (3) as shown; the inscribed circle diameter of the middle feed hole is 1 cm, the inscribed circle diameter of the four surrounding feed holes is 0.4 cm, and the distance between the surrounding small feed holes and the middle large feed hole is 0.3 cm.

[0085] Example 4

[0086] The system and method of Example 1 are followed, except that a circular feed hole is provided in the feed control device, and the diameter of the inscribed circle of the feed hole is 1.5 cm.

[0087] Example 5

[0088] The system and method of Example 1 are followed, except that a circular feed hole is provided in the feed control device, and the diameter of the inscribed circle of the feed hole is 2.5 cm.

[0089] Example 6

[0090] The system and method of Example 1 are used, except that 29 circular feed holes are provided in the feed control device. The feed hole design schematic diagram is shown in FIG. Figure 2 (4) As shown; the diameter of the inscribed circle of a single feed hole is 0.25 cm, and the distance between two adjacent feed holes is 0.2 cm.

[0091] Example 7

[0092] The system and method of Example 1 are used, except that 29 circular feed holes are provided in the feed control device. The feed hole design schematic diagram is shown in FIG. Figure 2 (4) as shown; the inscribed circle diameter of a single feed hole is 0.25 cm, and the distance between two adjacent feed ports is 0.2 cm; in addition, in step (1), "heat to 120 ° C and continue to react for 4 hours" is replaced by "reaction time at 120 ° C is 2 hours".

[0093] Comparative Example 1

[0094] The polymerization reaction was carried out according to the system and method in Example 1, except that in step (1), no control was performed when the viscous mixed solution containing the polymerization product entered the precipitation tank V2 (the feed hole diameter in the feed control device was greater than 3 cm, and the diameter of a single strand of the polymer solution when entering the precipitant was greater than 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.

[0095] 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 (the test result was smaller).

[0096] Test Case

[0097] (1) The intrinsic viscosity of polybenzimidazole (which can reflect the molecular weight) is measured 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 30min. 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.

[0098] Increased viscosity

[0099] Intrinsic viscosity

[0100] (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.

[0101] The test results of the intrinsic viscosity and insoluble content of the final product S12 are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] It can be seen from the results in Table 1 that Examples 1-7, in which the feed device of the present invention is used to set the number of feed holes and the feed hole diameter to control the slow contact between the viscous mixed solution containing the polymerization product and the precipitant, have a lower insoluble matter content (within 10%), the solubility of the polybenzimidazole product is better, and the quality of the product is significantly better.

[0106] 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 system for preparing polybenzimidazole, It is characterized in that The system includes: A polymerization unit, used to polymerize the reaction monomers to obtain a reaction solution containing polybenzimidazole; A precipitation unit, used for contacting the reaction solution containing polybenzimidazole with a precipitant to precipitate polybenzimidazole; Wherein, a discharge control device is provided in the polymerization unit or a feed control device is provided in the precipitation unit, and the discharge control device or the feed control device is used to control the diameter of the reaction liquid containing polybenzimidazole entering the precipitation unit.

2. A system according to claim 1, in, The discharge control device is provided with at least one discharge hole, and the diameter of the inscribed circle of the single discharge hole is 0.1-3 cm; And / or, the feed control device is provided with at least one feed hole, and the diameter of the inscribed circle of the single feed hole is 0.1-3 cm.

3. A system according to claim 2, in, The discharge control device is provided with 1-30 discharge holes; And / or, the feed control device is provided with 1-30 feed holes.

4. The system according to claim 2, in, The distance between two adjacent discharge holes in the discharge control device is 0.1-2 cm; And / or, the distance between two adjacent feed ports in the feed control device is 0.1-2 cm.

5. The system according to claim 1, in, The polymerization unit comprises at least one polymerization kettle, preferably 1 to 2 polymerization kettles.

6. The system according to claim 1, in, The precipitation unit comprises at least one precipitation tank.

7. The system according to claim 1, in, The system further comprises a pulverizing unit, which is used for pulverizing the polybenzimidazole.

8. The system according to claim 7, in, The system further comprises a washing unit, which is used for washing the crushed polybenzimidazole.

9. The system according to claim 8, in, The system further comprises a drying unit, which is used for drying the washed polybenzimidazole.

10. A method for preparing polybenzimidazole using the system according to any one of claims 1 to 9, It is characterized in that The method comprises: sending reaction monomers into a polymerization unit for polymerization reaction to obtain a reaction liquid containing polybenzimidazole; and then sending the reaction liquid containing polybenzimidazole into a precipitation unit to contact with a precipitant to obtain polybenzimidazole and waste liquid.

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