A method for preparing sulfonated polyetheretherketone

Abstract

The invention provides a method for preparing sulfonated polyetheretherketone, belonging to the technical field of condensation polymers of ketones and phenols. The preparation method comprises preparing modified polyetheretherketone, pretreatment, sulfonation, and post-treatment. The method for preparing the modified polyetheretherketone comprises the following steps: adding 4,4'-difluorobenzophenone, hydroquinone, and diphenyl sulfone to a reaction kettle under nitrogen protection; heating the kettle to 170-190°C; adding a catalyst; maintaining the temperature for 0.8-1.2 hours; then dropwise adding a PEG-400 solution at 260-290°C for 1.5-2.5 hours; reacting the mixture at 310-330°C for 1.5-3.5 hours after the dropwise addition is completed; cooling and crystallizing the mixture after the reaction is completed; and washing away the solvent and inorganic salts to obtain the modified polyetheretherketone. The sulfonated polyetheretherketone of the invention has a sulfonation degree of 69.6-75.1%, good sulfonation uniformity, and a deviation of 2.37-2.52%.

Description

Technical Field

[0001] The invention belongs to the technical field of condensation polymers of ketones and phenols, and particularly relates to a method for preparing sulfonated polyetheretherketone. Background Art

[0002] New energy sources such as photovoltaics and wind power are developing rapidly. However, clean energy sources such as solar energy and wind energy are subject to time, season, and space constraints, and their power generation process is intermittent and volatile. Large-scale grid connection will have a huge impact on the safety and stability of the power system. Large-scale energy storage technology is an effective way to solve the instability and intermittency of wind and solar power generation. Compared with other energy storage technologies, liquid flow batteries have become one of the current mainstream energy storage technologies due to their high energy efficiency, large energy storage scale, high safety performance, and long cycle life.

[0003] Among the key materials that make up liquid flow batteries, ion exchange membranes have always been the focus of research. They separate the positive and negative electrode solutions, maintain the transfer of conductive ions, and achieve selective passage and separation of ions, providing basic support for the efficient operation of liquid flow batteries. Sulfonated polyetheretherketone membranes have the advantages of good ion selectivity, low cost, simple preparation process, and avoidance of cross-contamination. Therefore, their research and application are becoming more and more extensive. Among them, improving the sulfonation uniformity of polyetheretherketone is crucial to improving the performance of sulfonated polyetheretherketone membranes.

[0004] At present, the most commonly used preparation method is the solution sulfonation method, the main principle of which is to use a strong sulfonating agent (such as concentrated sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, etc.) to carry out an electrophilic substitution reaction on polyetheretherketone in a solvent, introduce the sulfonic acid group (-SO3H) into the benzene ring structure, and obtain sulfonated polyetheretherketone.

[0005] However, the following problems will affect the uniformity of sulfonation of PEEK: 1. The entanglement of molecular chains in PEEK particles or solutions hinders the diffusion of the sulfonating agent, resulting in a higher degree of sulfonation on the surface than inside, or excessive sulfonation in local areas; 2. High-concentration sulfonating agents such as concentrated sulfuric acid react violently with PEEK, and local overheating leads to degradation or uneven sulfonation; 3. Due to the crystallinity of the PEEK molecular chain, the molecules in the crystalline area are closely arranged, making it difficult for the sulfonating agent to penetrate, resulting in a higher degree of sulfonation in the amorphous area than in the crystalline area. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a method for preparing sulfonated polyetheretherketone to achieve the following invention objectives: to provide a sulfonated polyetheretherketone with uniform sulfonation degree, and the prepared sulfonated polyetheretherketone membrane has high ion exchange capacity, good tensile strength and high thermal decomposition temperature.

[0007] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0008] A method for preparing sulfonated polyetheretherketone, comprising:

[0009] 1. Preparation of modified polyetheretherketone

[0010] Under nitrogen protection, 4,4'-difluorobenzophenone, hydroquinone and diphenyl sulfone were added to a reaction kettle, the temperature was raised to 170-190°C, a catalyst was added, and the temperature was kept for 0.8-1.2 hours. Then, a PEG-400 solution was added dropwise at 260-290°C, and the addition time was controlled to be 1.5-2.5 hours. After the addition was completed, the reaction was carried out at 310-330°C for 1.5-3.5 hours. After the reaction was completed, the solution was cooled and crystallized, and the solvent and inorganic salts were washed away with acetone and deionized water to obtain a modified polyetheretherketone.

[0011] The mass ratio of the 4,4'-difluorobenzophenone, hydroquinone, diphenyl sulfone, catalyst, and PEG-400 solution is 59-63:21-23:125-137:46-50:22-26;

[0012] The mass fraction of the PEG-400 solution is 20-30%;

[0013] The catalyst is calcium carbonate.

[0014] 2. Preprocessing

[0015] The modified polyetheretherketone is placed in an oven to dry the water, and then ball-milled into a powder with a particle size of 8 to 12 μm, and then dissolved in N-methylpyrrolidone and allowed to stand for 20 to 40 minutes to obtain a modified polyetheretherketone solution;

[0016] The mass ratio of the modified polyetheretherketone to N-methylpyrrolidone is 0.8-1.2:12-14;

[0017] The drying temperature is 60-100° C., and the drying time is 6-8 hours.

[0018] 3. Sulfonation

[0019] Add concentrated sulfuric acid and dichloroethane to the reactor, start stirring, preheat to 40-60°C, add catalyst FeCl3, and then divide the modified polyetheretherketone solution into 6-10 parts and add them to the reactor in batches, with an interval of 30-50 minutes between each batch. After the addition is completed, heat to 70-80°C and continue to react for 6-10 hours. The reaction is completed;

[0020] The mass ratio of the concentrated sulfuric acid, ethylene dichloride, FeCl3, and modified polyetheretherketone solution is 2.5-3.5:0.8-1.2:0.005-0.007:4.1-4.3;

[0021] The initial stirring rate is 100-200 r / min. After the catalyst FeCl3 is added, the stirring rate is increased to 1000-1600 r / min.

[0022] 4. Post-processing

[0023] The reacted material is passed through the discharge port of the reactor and placed into a product barrel filled with constant temperature deionized water within 20 to 40 minutes. The deionized water temperature is 5 to 25°C and accounts for 30 to 40% of the total volume of the product barrel. After the discharge is completed, the sulfonated polyetheretherketone is washed with deionized water to a neutral state, and then placed in an oven for drying to obtain the sulfonated polyetheretherketone;

[0024] The oven temperature is 60-100° C., and the drying time is 12-16 hours.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The sulfonated polyetheretherketone of the present invention introduces a hydrophilic spacer group PEG-400 segment during the polyetheretherketone synthesis stage to improve the solubility of the prepolymer in the sulfonating agent concentrated sulfuric acid and make the sulfonic acid group more evenly distributed;

[0027] Add a pretreatment process. First, the polyetheretherketone is crushed to micron level by ball milling to increase the surface area and destroy part of the crystal structure, which promotes the penetration of the sulfonating agent concentrated sulfuric acid. Then the polyetheretherketone powder is dissolved in N-methylpyrrolidone to make the molecular chain stretch and swell, thereby improving the contact efficiency with the sulfonating agent concentrated sulfuric acid.

[0028] During the sulfonation process, a mixed system of concentrated sulfuric acid and inert solvent ethylene dichloride is used, and polyetheretherketone is added in batches to reduce the intensity of the reaction, slow down local overheating, and avoid local degradation at high temperatures;

[0029] By regulating in the above-mentioned multiple ways, the sulfonation uniformity of sulfonated polyetheretherketone is improved;

[0030] The sulfonated polyetheretherketone of the present invention has a sulfonation degree of 69.6-75.1%, good sulfonation uniformity, and a deviation of 2.37-2.52%. The prepared sulfonated polyetheretherketone membrane has an ion exchange capacity of 2.16-2.21 mmol / g, a tensile strength of 33.8-36.5 MPa, and a thermal decomposition temperature of 285-307°C. DETAILED DESCRIPTION

[0031] Example 1

[0032] A method for preparing sulfonated polyetheretherketone, comprising:

[0033] 1. Preparation of modified polyetheretherketone

[0034] Under nitrogen protection, 4,4'-difluorobenzophenone, hydroquinone and diphenyl sulfone were added to a reaction kettle, the temperature was raised to 180°C, a catalyst was added, and the temperature was kept for 1 hour. Then, PEG-400 solution was added dropwise at 275°C for 2 hours. After the addition was completed, the reaction was carried out at 320°C for 2.5 hours. After the reaction was completed, the solution was cooled and crystallized, and the solvent and inorganic salts were washed away with acetone and deionized water to obtain modified polyetheretherketone.

[0035] The mass ratio of the 4,4'-difluorobenzophenone, hydroquinone, diphenyl sulfone, catalyst, and PEG-400 solution is 61:22:131:48:24;

[0036] The mass fraction of the PEG-400 solution is 25%;

[0037] The catalyst is calcium carbonate.

[0038] 2. Preprocessing

[0039] The modified polyetheretherketone was placed in an oven to dry the water, and then ball-milled into a powder with a particle size of 10 μm, and then dissolved in N-methylpyrrolidone and allowed to stand for 30 minutes to obtain a modified polyetheretherketone solution;

[0040] The mass ratio of the modified polyetheretherketone to N-methylpyrrolidone is 1:13;

[0041] The drying temperature is 80° C. and the drying time is 7 h.

[0042] 3. Sulfonation

[0043] Concentrated sulfuric acid and dichloroethane were added to the reactor, stirred, and preheated to 50°C. The catalyst FeCl3 was then added. The modified polyetheretherketone solution was then divided into 8 equal parts and added to the reactor in batches, with each batch added at a time interval of 40 minutes. After the addition was completed, the temperature was raised to 75°C and the reaction was continued for 8 hours. The reaction was completed.

[0044] The mass ratio of the concentrated sulfuric acid, ethylene dichloride, FeCl3, and modified polyetheretherketone solution is 3:1:0.006:4.2;

[0045] The initial stirring rate was 150 r / min, and after the catalyst FeCl3 was added, the stirring rate was increased to 1300 r / min.

[0046] 4. Post-processing

[0047] The reacted material is passed through the discharge port of the reactor and placed into a product barrel filled with constant temperature deionized water within 30 minutes. The deionized water temperature is 15°C and accounts for 35% of the total volume of the product barrel. After the discharge is completed, the sulfonated polyetheretherketone is washed with deionized water to neutrality and then placed in an oven for drying to obtain sulfonated polyetheretherketone;

[0048] The oven temperature is 80° C. and the drying time is 14 h.

[0049] Example 2

[0050] A method for preparing sulfonated polyetheretherketone, comprising:

[0051] 1. Preparation of modified polyetheretherketone

[0052] Under nitrogen protection, 4,4'-difluorobenzophenone, hydroquinone and diphenyl sulfone were added to a reaction kettle, the temperature was raised to 170°C, a catalyst was added, and the temperature was kept for 0.8h. Then, PEG-400 solution was added dropwise at 260°C for 1.5h. After the addition was completed, the reaction was carried out at 310°C for 1.5h. After the reaction was completed, the mixture was cooled and crystallized, and the solvent and inorganic salts were washed away with acetone and deionized water to obtain modified polyetheretherketone.

[0053] The mass ratio of the 4,4'-difluorobenzophenone, hydroquinone, diphenyl sulfone, catalyst, and PEG-400 solution is 59:21:125:46:22;

[0054] The mass fraction of the PEG-400 solution is 20%;

[0055] The catalyst is calcium carbonate.

[0056] 2. Preprocessing

[0057] The modified polyetheretherketone was placed in an oven to dry the water, and then ball-milled into a powder with a particle size of 8 μm, and then dissolved in N-methylpyrrolidone and allowed to stand for 20 minutes to obtain a modified polyetheretherketone solution;

[0058] The mass ratio of the modified polyetheretherketone to N-methylpyrrolidone is 0.8:12;

[0059] The drying temperature is 60° C. and the drying time is 6 hours.

[0060] 3. Sulfonation

[0061] Concentrated sulfuric acid and dichloroethane were added to the reactor, stirred, and preheated to 40°C. The catalyst FeCl3 was then added. The modified polyetheretherketone solution was then divided into 6 equal parts and added to the reactor in batches, with each batch added 30 minutes apart. After the addition was complete, the temperature was raised to 70°C and the reaction was continued for 6 hours. The reaction was then completed.

[0062] The mass ratio of the concentrated sulfuric acid, ethylene dichloride, FeCl3, and modified polyetheretherketone solution is 2.5:0.8:0.005:4.1;

[0063] The initial stirring rate was 100 r / min, and after the catalyst FeCl3 was added, the stirring rate was increased to 1000 r / min.

[0064] 4. Post-processing

[0065] The reacted material is passed through the discharge port of the reactor and placed into a product barrel filled with constant temperature deionized water within 20 minutes. The deionized water temperature is 5°C and accounts for 30% of the total volume of the product barrel. After the discharge is completed, the sulfonated polyetheretherketone is washed with deionized water to neutrality and then placed in an oven for drying to obtain sulfonated polyetheretherketone;

[0066] The oven temperature is 60° C. and the drying time is 12 h.

[0067] Example 3

[0068] A method for preparing sulfonated polyetheretherketone, comprising:

[0069] 1. Preparation of modified polyetheretherketone

[0070] Under nitrogen protection, 4,4'-difluorobenzophenone, hydroquinone and diphenyl sulfone were added to a reactor, the temperature was raised to 190°C, a catalyst was added, and the temperature was kept for 1.2 hours. Then, PEG-400 solution was added dropwise at 290°C for 2.5 hours. After the addition was complete, the reaction was carried out at 330°C for 3.5 hours. After the reaction was completed, the mixture was cooled and crystallized, and the solvent and inorganic salts were washed away with acetone and deionized water to obtain modified polyetheretherketone.

[0071] The mass ratio of the 4,4'-difluorobenzophenone, hydroquinone, diphenyl sulfone, catalyst, and PEG-400 solution is 63:23:137:50:26;

[0072] The mass fraction of the PEG-400 solution is 30%;

[0073] The catalyst is calcium carbonate.

[0074] 2. Preprocessing

[0075] The modified polyetheretherketone was placed in an oven to dry out the moisture, and then ball-milled into a powder with a particle size of 12 μm, and then dissolved in N-methylpyrrolidone and allowed to stand for 40 minutes to obtain a modified polyetheretherketone solution;

[0076] The mass ratio of the modified polyetheretherketone to N-methylpyrrolidone is 1.2:14;

[0077] The drying temperature is 100° C. and the drying time is 8 hours.

[0078] 3. Sulfonation

[0079] Concentrated sulfuric acid and dichloroethane were added to the reactor, stirred, and preheated to 60°C. The catalyst FeCl3 was then added. The modified polyetheretherketone solution was then divided into 10 equal parts and added to the reactor in batches, with an interval of 50 minutes between each batch. After the addition was completed, the temperature was raised to 80°C and the reaction was continued for 10 hours. The reaction was then completed.

[0080] The mass ratio of the concentrated sulfuric acid, ethylene dichloride, FeCl3, and modified polyetheretherketone solution is 3.5:1.2:0.007:4.3;

[0081] The initial stirring rate was 200 r / min, and after the catalyst FeCl3 was added, the stirring rate was increased to 1600 r / min.

[0082] 4. Post-processing

[0083] The reacted material is passed through the discharge port of the reactor and placed into a product barrel filled with constant temperature deionized water within 40 minutes. The deionized water temperature is 25°C and accounts for 40% of the total volume of the product barrel. After the discharge is completed, the sulfonated polyetheretherketone is washed with deionized water to a neutral state and then placed in an oven for drying to obtain the sulfonated polyetheretherketone;

[0084] The oven temperature is 100° C., and the drying time is 16 h.

[0085] Example 4

[0086] A method for preparing sulfonated polyetheretherketone is provided. Based on Example 1, step 1 is deleted and the modified polyetheretherketone is replaced by polyetheretherketone.

[0087] Example 5

[0088] A method for preparing sulfonated polyetheretherketone, based on Example 1, omitting the process of dissolving and allowing the modified polyetheretherketone powder to stand in N-methylpyrrolidone in step 2, and replacing the modified polyetheretherketone solution with modified polyetheretherketone powder.

[0089] Example 6

[0090] A method for preparing sulfonated polyetheretherketone, based on Example 1, wherein the reaction time in step 3 is changed to 12 hours.

[0091] Example 7

[0092] A method for preparing sulfonated polyetheretherketone, based on Example 1, wherein the reaction time in step 3 is changed to 15 hours.

[0093] Test example

[0094] 1. The sulfonated polyetheretherketone prepared in Examples 1 to 7 was tested for sulfonation degree by potentiometric titration. Six groups of samples were randomly sampled for each example. The test results were statistically analyzed, and the average value and deviation were calculated. The larger the average value, the higher the sulfonation degree, and the closer the deviation is to 0, the better the sulfonation uniformity.

[0095] The test results are shown in Table 1:

[0096] Table 1

[0097]

[0098] 2. The sulfonated polyetheretherketone prepared in Examples 1 to 7 were respectively prepared into sulfonated polyetheretherketone membranes using the following methods, and the following properties were tested.

[0099] Sulfonated polyetheretherketone powder was dissolved in dimethyl sulfoxide at a concentration of 10% wt, heated to 70°C and stirred until completely dissolved, the solution was poured onto a clean glass substrate, and the film thickness was controlled to 80 μm with a scraper. The solvent was evaporated at room temperature for 24 hours, and then dried in an oven at 80°C for 12 hours to remove the residual solvent to obtain a sulfonated polyetheretherketone membrane.

[0100] The test results are shown in Table 2:

[0101] Table 2

[0102]

[0103] From the above results, it can be seen that Example 4 did not modify the polyetheretherketone and had poor solubility. The sulfonated polyetheretherketone of Example 5 did not dissolve in N-methylpyrrolidone, the molecular chain did not stretch and swell, and the contact efficiency with the high sulfonating agent concentrated sulfuric acid was poor, which led to low sulfonation degree and poor sulfonation uniformity in Examples 4 and 5, and low ion exchange capacity of the prepared sulfonated polyetheretherketone membrane.

[0104] Compared with Example 1, Examples 6 and 7 have a long sulfonation reaction time, and thus a high degree of sulfonation. However, long-term sulfonation at high temperature will lead to molecular chain degradation, affecting the uniformity of sulfonation. At the same time, the higher the degree of sulfonation, the higher the ion exchange capacity obtained, but the tensile strength and thermal decomposition temperature will decrease.

Claims

1. A method for preparing sulfonated polyetheretherketone, characterized in that: The preparation method includes preparing modified polyetheretherketone, pretreatment, sulfonation, and post-treatment; The method for preparing the modified polyetheretherketone comprises: adding 4,4'-difluorobenzophenone, hydroquinone and diphenyl sulfone to a reaction kettle under nitrogen protection, heating the temperature to 170-190°C, adding a catalyst, and keeping the temperature for 0.8-1.2 hours, then dropwise adding a PEG-400 solution at 260-290°C, reacting at 310-330°C for 1.5-3.5 hours after the dropwise addition is complete, and then cooling, crystallizing and washing to obtain the modified polyetheretherketone; The pretreatment method comprises drying the modified polyetheretherketone, ball-milling the powder, dissolving the powder in N-methylpyrrolidone and standing the powder for 20 to 40 minutes to obtain a modified polyetheretherketone solution; The sulfonation method comprises adding concentrated sulfuric acid and ethylene dichloride into a reaction kettle, starting stirring, preheating to 40-60° C., adding a catalyst FeCl 3, and then adding a modified polyetheretherketone solution in batches, then heating to 70-80° C., reacting for 6-10 hours, and completing the reaction; The post-treatment method is to discharge the reaction product through the discharge port of the reactor into a product barrel, wash it to neutrality, and dry it to obtain sulfonated polyetheretherketone; The mass ratio of the modified polyetheretherketone to N-methylpyrrolidone is 0.8-1.2:12-14; the drying temperature is 60-100° C., the drying time is 6-8 hours, and the particle size of the ball-milled powder is 8-12 μm.

2. The method for preparing sulfonated polyetheretherketone according to claim 1, wherein: In the method for preparing modified polyetheretherketone, the mass ratio of 4,4'-difluorobenzophenone, hydroquinone, diphenyl sulfone, catalyst, and PEG-400 solution is 59-63:21-23:125-137:46-50:22-26; the mass fraction of the PEG-400 solution is 20-30%; and the time for dripping the PEG-400 solution is 1.5-2.5 hours. The catalyst is calcium carbonate.

3. The method for preparing sulfonated polyetheretherketone according to claim 1, wherein: In the sulfonation method, the modified polyetheretherketone solution is added in batches by dividing the modified polyetheretherketone solution into 6 to 10 portions on average, and adding one portion to the reactor every 30 to 50 minutes.

4. The method for preparing sulfonated polyetheretherketone according to claim 1, wherein: In the sulfonation method, the mass ratio of concentrated sulfuric acid, ethylene dichloride, FeCl3, and modified polyetheretherketone solution is 2.5-3.5:0.8-1.2:0.005-0.007:4.1-4.3; The initial stirring rate is 100-200 r / min. After the catalyst FeCl3 is added, the stirring rate is increased to 1000-1600 r / min.

5. The method for preparing sulfonated polyetheretherketone according to claim 1, wherein: In the post-treatment method, the discharge time is controlled within 20 to 40 minutes, the product barrel is pre-filled with deionized water, the deionized water temperature is 5 to 25° C., and accounts for 30 to 40% of the total volume of the product barrel.

6. The method for preparing sulfonated polyetheretherketone according to claim 1, wherein: In the post-treatment method, the oven temperature is 60-100° C., and the drying time is 12-16 hours.

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