A method for the preparation of polyether ether ketone

Abstract

This invention relates to the field of polyetheretherketone (PEEK) preparation and discloses a method for preparing PEEK. The method involves a polymerization reaction of hydroquinone, fluoroketone, and an alkali metal salt in a polymerization reactor, wherein the alkali metal salt is sodium carbonate and / or potassium carbonate. After the polymerization reaction, end-capping treatment is performed as follows: a first compound end-capping agent is added at a temperature of 310-330°C, and the polymerization end-capping reaction is carried out for at least 5 minutes. The first compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li₂SO₄) at a mass ratio of 1:0.2-0.8. A second compound end-capping agent is added at a temperature of 260-300°C, and the polymerization end-capping reaction is continued for at least 10 minutes. The second compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li₂SO₄) at a mass ratio of 1:1-6. The PEEK obtained in this application exhibits both excellent thermal stability and a narrow PDI distribution.

Description

Technical Field

[0001] This invention relates to the field of polyether ether ketone (PEEK), and more specifically to a method for preparing PEEK. Background Technology

[0002] The mainstream synthetic route for polyetheretherketone (PEEK) is mainly derived from the nucleophilic substitution condensation reaction developed by Vigers in the 1970s. It is widely used by various manufacturers. The main synthetic route is as follows: after melting diphenyl sulfone at high temperature, 4,4'-difluorobenzophenone, aromatic hydroquinone, and sodium / potassium carbonate are added to the reactor and polymerized under inert gas protection. Near the end of the reaction, a fluorinated end-capping agent is added to terminate the polymerization reaction, resulting in end-capped polyetheretherketone.

[0003] To improve the industrial application prospects of this preparation route, some technical solutions have been developed to improve the batch stability, molecular weight distribution (PDI), thermal stability, or color of this preparation route.

[0004] For example, patent application CN121045542A discloses a polyetheretherketone resin with an extremely narrow molecular weight distribution, its preparation method, and its application. The main method involves uniformly mixing 4,4'-difluorobenzophenone, phenolic monomers, a salt-forming agent, and a solvent under an inert atmosphere, followed by gradient heating and then end-capping. The gradient heating includes an initial stage (holding temperature 140-210℃), a transition stage (holding temperature 250-280℃), and a final stage (holding temperature 300-320℃). The resulting PEEK resin has a very narrow molecular weight distribution. In preferred embodiments, the molecular weight distribution index (PDI) of the polyetheretherketone resin can be controlled between 1.8 and 2.1. However, the thermal stability of the polyetheretherketone resin obtained by this process is still relatively poor, with its initial thermal decomposition temperature only reaching a maximum range of 560-570℃.

[0005] For example, patent application CN120157870A discloses a polyetheretherketone resin with a controllable molecular weight distribution, its synthesis method, and its application. The synthesis method includes preparing the polyetheretherketone resin in the presence of alkali metal carbonates and / or bicarbonates; wherein the alkali metal carbonates and / or bicarbonates include sodium carbonate and potassium carbonate, and wherein the sodium carbonate has a gradient particle size distribution, comprising: coarse particles with a particle size of 20-120 mesh, 30-40%; and fine particles with a particle size of 200-350 mesh, 50%... -60%; buffer particles with a particle size greater than 120 mesh and less than 200 mesh, 10-20%; by using sodium carbonate with a specific particle size distribution, the reaction rate is controlled to maintain stability, resulting in a narrow molecular weight distribution of the polymer; the proposed method of using sodium carbonate with a specific gradient particle size distribution as a raw material is not only difficult to implement in terms of process, but also the ether ether ketone resin prepared by it achieves a high level of thermal stability (its initial thermal decomposition temperature can reach 590℃), but its PDI distribution still significantly exceeds 3.

[0006] Currently, there is still no polyetheretherketone (PEEK) preparation process that can simultaneously possess excellent thermal stability and a narrow PDI distribution, making it difficult to meet the needs of mass applications in scenarios with high performance requirements. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method for preparing polyetheretherketone (PEEK). The PEEK obtained by this specific end-capping process has both excellent thermal stability and a narrow PDI distribution, making it particularly suitable for industrial applications in high-performance applications (such as high-end fields such as biomedicine, aerospace, semiconductors, and electrical engineering).

[0008] The technical solution adopted in this invention is as follows: A method for preparing polyetheretherketone (PEEK) involves purging a high-purity inert gas to replace the air in a polymerization reactor. Hydroquinone, fluoroketone, and an alkali metal salt undergo a polymerization reaction in the reactor under a solvent atmosphere and gradient temperature conditions. The alkali metal salt is sodium carbonate and / or potassium carbonate. After the polymerization reaction, end-capping is performed according to the following process: Under a temperature of 310-330℃, a first compound end-capping agent is added, and a polymerization end-capping reaction is carried out for at least 5 minutes. The first compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li2SO4) in a mass ratio of 1:0.2-0.8. Under a temperature of 260-300℃, a second compound end-capping agent is added, and the polymerization end-capping reaction is continued for at least 10 minutes. The second compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate Li2SO4 in a mass ratio of 1:1-6. The obtained reaction product was post-processed to obtain polyether ether ketone.

[0009] Preferably, the initial thermal decomposition temperature of the polyether ether ketone is not lower than 580°C, and the PDI distribution value of the polyether ether ketone is controlled within 2.2, more preferably within 2.1.

[0010] Preferably, the initial thermal decomposition temperature range of the polyether ether ketone is 582-595℃, and the PDI distribution value of the polyether ether ketone is controlled within the range of 1.8-2.1.

[0011] Preferably, both the first compound end-capping agent and the second compound end-capping agent are added to the polymerization reactor in a molten state.

[0012] Preferably, when preparing the first compound capping agent or the second compound capping agent, the fluorine-containing capping agent is preheated to a molten state, and then the corresponding anhydrous lithium sulfate Li2SO4 is added to the molten fluorine-containing capping agent and mixed evenly.

[0013] Preferably, the molar ratio of the fluorinated end-capping agent to hydroquinone in the first compound end-capping agent is 1:60-100; and the molar ratio of the fluorinated end-capping agent to hydroquinone in the second compound end-capping agent is 1:150-200.

[0014] Preferably, the second compound end-capping agent is added 10-20 minutes after the first compound end-capping agent is added, and the end-capping treatment is completed 15-25 minutes later.

[0015] Preferably, the mass ratio of the solvent: alkali metal salt: hydroquinone: fluoroketone is 3-3.6:1-1.2:1-1.5:1; the alkali metal salt is a mixture of sodium carbonate and potassium carbonate, wherein the mass ratio of sodium carbonate to potassium carbonate is in the range of 1:0.1-0.5.

[0016] Preferably, while introducing high-purity inert gas to replace the air in the polymerization reactor, the reactor temperature is simultaneously controlled to 140-160°C. Then, the raw materials are added into the polymerization reactor, and the temperature inside the reactor is gradually increased to 310-330°C to carry out the polymerization reaction. The polymerization reaction takes 2.5-4 hours.

[0017] Preferably, the gas generated by the reaction in the polymerization reactor enters the polymerization reactor heat exchanger through a pipeline, and a small amount of raw materials and reaction products discharged with the gas are returned to the polymerization reactor through the heat exchange system. The tail gas is discharged through the exhaust port of the polymerization reactor heat exchanger. After the end-sealing treatment is completed, the discharge valve of the polymerization reactor is opened and the reaction products are discharged into the tablet press through a closed pipeline to obtain crude polyether ether ketone. The crude polyether ether ketone is pressed into thin sheets, and the thin sheets are crushed, washed and dried to obtain the polyether ether ketone.

[0018] It should be noted that the polymerization reactor raw materials involved in this application can refer to the continuous feeding scheme and continuous feeding device proposed in the prior Chinese patent CN122356462A, which can further improve the synthesis efficiency and ensure the batch stability of the final polyether ether ketone product. These are conventional technical choices for those skilled in the art.

[0019] It should also be noted that the "high-purity inert gas" involved in this application refers to an inert gas with a purity of ≥99.999%, and high-purity nitrogen is usually used in the implementation of this application.

[0020] This application proposes a capping process involving a specific first compound capping agent and a second compound capping agent in sequence. First, the polymer is capped at a relatively high temperature (310-330℃) using the first compound capping agent. While the fluorinated capping agent in the first compound capping agent undergoes a rapid capping polymerization reaction with the PEEK (polyether ether ketone) polymer, the Li2SO4 in the first compound capping agent assists in the capping effect of the polymerization reaction. Then, the polymer is capped a second time at a lower temperature (260-300℃) using the second compound capping agent, providing a gradient capping effect. After implementation and verification, the applicant found that the polyether ether ketone obtained through this specific capping process exhibits excellent thermal stability and a narrow PDI distribution (the initial thermal decomposition temperature of the obtained polyether ether ketone is not lower than 580℃, and its PDI distribution value is controlled within the range of 2.2), making it particularly suitable for industrial applications in high-performance demand scenarios (such as high-end fields such as biomedicine, aerospace, semiconductors, and electrical engineering). Attached Figure Description

[0021] Figure 1 This is the infrared spectrum characterization of the polyether ether ketone prepared in Example 1 of this application. Detailed Implementation

[0022] This embodiment proposes a method for preparing polyether ether ketone (PEEK). High-purity inert gas is introduced to replace the air in the polymerization reactor. Hydroquinone, fluoroketone, and alkali metal salts in the reactor undergo polymerization under a solvent atmosphere and gradient temperature conditions. The alkali metal salts used are sodium carbonate and / or potassium carbonate. Preferably, in this embodiment, while introducing high-purity inert gas to replace the air in the polymerization reactor, the reactor temperature is simultaneously controlled to 140-160°C. Then, the raw materials are added to the polymerization reactor, and the temperature inside the reactor is gradually increased to 310-330°C to carry out the polymerization reaction. The polymerization reaction time is 2.5-4 hours.

[0023] Preferably, in this embodiment, the mass ratio of solvent: alkali metal salt: hydroquinone: fluoroketone is 3-3.6:1-1.2:1-1.5:1, more preferably 3-3.4:1-1.1:1.1-1.3:1; preferably, in this embodiment, the fluoroketone is 4,4'-difluorobenzophenone; the solvent is diphenyl sulfone; preferably, in this embodiment, in order to further facilitate the stability of the polymerization reaction, the alkali metal salt is a mixture of sodium carbonate and potassium carbonate, wherein the mass ratio of sodium carbonate to potassium carbonate ranges from 1:0.1-0.5.

[0024] In this embodiment, the end-capping treatment is performed after the polymerization reaction is completed as follows: A first compound end-capping agent is added at a temperature of 310-330°C, and the polymerization end-capping reaction is carried out for at least 5 minutes. The first compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li₂SO₄) at a mass ratio of 1:0.2-0.8. A second compound end-capping agent is added at a temperature of 260-300°C, and the polymerization end-capping reaction is continued for at least 10 minutes. The second compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li₂SO₄) at a mass ratio of 1:1-6. The resulting reaction product is then post-treated to obtain polyetheretherketone (PEEK). Preferably, in this embodiment, the fluorinated end-capping agent is 4,4'-difluorobenzophenone.

[0025] To further improve the end-capping efficiency and the stability of the end-capping process, preferably, in this embodiment, both the first compound end-capping agent and the second compound end-capping agent are added to the polymerization reactor in a molten state; preferably, in this embodiment, when preparing the first compound end-capping agent or the second compound end-capping agent, the fluorinated end-capping agent is preheated to a molten state (it is recommended that the heating temperature be set within a range 1-10°C higher than the melting point of the fluorinated end-capping agent), and then the corresponding anhydrous lithium sulfate Li2SO4 is added to the molten fluorinated end-capping agent, mixed evenly, and kept in the molten state before being fed into the polymerization reactor.

[0026] Preferably, in this embodiment, the molar ratio of the fluorinated end-capping agent to hydroquinone in the first compound end-capping agent is 1:60-100; the molar ratio of the fluorinated end-capping agent to hydroquinone in the second compound end-capping agent is 1:150-200; preferably, in this embodiment, the second compound end-capping agent is added 10-20 minutes after the first compound end-capping agent is added, and the end-capping treatment is completed 15-25 minutes later.

[0027] Preferably, in this embodiment, the gas generated by the reaction in the polymerization reactor enters the polymerization reactor heat exchanger through a pipeline, and a small amount of raw materials and reaction products discharged with the gas are returned to the polymerization reactor through the heat exchange system, and the tail gas in the gas is discharged through the exhaust port of the polymerization reactor heat exchanger.

[0028] It should be noted that the post-processing steps for the reaction products obtained from the polymer are common knowledge in the field and are not specifically limited in this application. It is recommended that all post-processing steps be carried out in a high-purity inert gas atmosphere to further ensure the quality of the obtained products.

[0029] Preferably, in this embodiment, after the end-capping treatment is completed, the discharge valve of the polymerization reactor is opened to discharge the reaction product through a closed pipeline to the tablet press to obtain crude polyetheretherketone (PEEK); the crude PEEK is pressed into thin sheets, and the sheets are crushed, washed and dried to obtain PEEK; more preferably, in the washing process of this embodiment, the crushed granular crude product is pre-purified with an organic solvent (e.g., ethanol or acetone) to remove unreacted raw materials, impurities and solvents, and then further removed by water washing to remove water-soluble impurities from the product.

[0030] Preferably, the initial thermal decomposition temperature of the polyether ether ketone obtained in this embodiment is not lower than 580°C, and the PDI distribution value of the polyether ether ketone is controlled within 2.2, more preferably, within 2.1; even more preferably, the initial thermal decomposition temperature range of the polyether ether ketone obtained in this embodiment is 582-595°C, and the PDI distribution value range of the polyether ether ketone is controlled within 1.8-2.1.

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, based on the above implementation schemes, the following embodiments are proposed. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0032] It should be noted that the raw materials involved in the following embodiments of this application are all directly purchased from the market.

[0033] Example 1:

[0034] Prepare the first compound capping agent according to the following procedure: In the capping agent mixing tank A, 4,4'-difluorobenzophenone (i.e., the fluorinated capping agent) is heated to a molten state at a temperature of 125°C, and then Li2SO4 is added. The mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:0.5. The two are mixed evenly to obtain the first compound capping agent in a molten state, which is then set aside.

[0035] Prepare the second compound capping agent according to the following procedure: In the end-capping agent mixing tank B, 4,4'-difluorobenzophenone is heated to a molten state at a temperature of 125°C, and then Li2SO4 is added, wherein the mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:3. The two are mixed evenly to obtain a second compound end-capping agent in a molten state for later use. Preparation of alkali metal salts: Sodium carbonate and potassium carbonate in a mass ratio of 1:0.25 are stirred to mix them evenly to obtain a compound alkali metal salt for later use;

[0036] The synthesis of polyetheretherketone is carried out according to the following procedure: High-purity nitrogen gas was introduced to replace the air in the polymerization reactor, and the reactor temperature was simultaneously controlled to 150°C. Then, hydroquinone, fluoroketone (4,4'-difluorobenzophenone), alkali metal salt, and diphenyl sulfone were added to the polymerization reactor, and the temperature was slowly increased in a stepwise manner (in this embodiment, the stepwise heating conditions were specifically set as follows: first, the temperature was increased to 245°C at a rate of 15°C / min, and then increased to 320°C at a rate of 10°C / min) to 320°C for polymerization reaction (polymerization reaction time was 3 hours). During the polymerization reaction, the progress of the reactants in the polymerization reactor was monitored in real time by online monitoring equipment. At a temperature of 320℃, the first compound end-capping agent was added for a first end-capping treatment for 15 minutes. After cooling to 280℃, the second compound end-capping agent was added for a second end-capping treatment. The end-capping treatment was completed after 20 minutes. Open the discharge valve of the polymerization reactor and discharge the material through the pipeline to the tablet press to obtain crude PEEK resin (i.e., polyether ether ketone). Press the crude PEEK resin into thin sheets, and then refine the sheets (including crushing, washing and drying processes) to obtain polyether ether ketone products, which are white granules in appearance. In this Example 1, the feeding ratio of each material is set as follows: diphenyl sulfone: sodium carbonate: hydroquinone: fluoroketone = 3.1:1.02:1.15:1, wherein the feeding amount of fluoroketone is 698.24g (approximately 3.2mol); the molar ratio of fluorinated end-capping agent to hydroquinone in the first compound end-capping agent is 1:65; the molar ratio of fluorinated end-capping agent to hydroquinone in the second compound end-capping agent is 1:180.

[0037] In this Example 1, the polyetheretherketone compound was purified and post-processed according to the following procedure: The thin sheet is fed into a pulverizer and then crushed into smaller particles. The pulverized particles are then washed with ethanol, washed with water, and dried in sequence. High-purity nitrogen is introduced into the ethanol washing tank, water washing tank, and dryer for atmosphere protection during operation.

[0038] Please see Figure 1As shown, the polyetheretherketone obtained in Example 1 was characterized by infrared spectroscopy. The characterization method used was the potassium bromide pellet method, and the specific process was as follows: The PEEK product (weighing 2 mg) was mixed and ground with dry potassium bromide at a mass ratio of 1:120, pressed into thin sheets, and then placed in an infrared spectrometer for transmittance testing. The spectral range of the infrared spectrometer was set to 4000-400 cm⁻¹. -1 ; from Figure 1 It can be seen that the polyether ether ketone obtained in Example 1 has high crystallinity and few impurities.

[0039] In this application, the glass transition temperature (Tg) of the polyether ether ketone obtained in Example 1 was tested, and the glass transition temperature (Tg) was 156.1°C.

[0040] To verify the target properties achieved in this embodiment, this application conducted initial thermal decomposition temperature and PDI distribution value tests on the polyether ether ketone product obtained in this embodiment 1. The initial thermal decomposition temperature of the polyether ether ketone obtained in this embodiment 1 was 585.3℃, and its PDI distribution value was 1.98.

[0041] It should be noted that the test standard for "initial thermal decomposition temperature of polyetheretherketone" mentioned in this application is ISO 11358-1-2022, and the test is conducted using a TGA thermogravimetric analyzer with oxygen and nitrogen in a volume ratio of 1:4. The test standard for "PDI distribution value" mentioned in this application is GB / T 36214.1-2018, and the test is conducted using a GPC gel permeation chromatograph. The test standard for "glass transition temperature (Tg)" mentioned in this application is YY / T 1707-2020, and the test is conducted using a DSC differential scanning calorimeter with the heating rate of the differential scanning calorimeter fixed at 20℃ / min during the test.

[0042] Example 2:

[0043] Prepare the first compound capping agent according to the following procedure: In the capping agent mixing tank A, 4,4'-difluorobenzophenone (i.e., the fluorinated capping agent) is heated to a molten state at a temperature of 125°C, and then Li2SO4 is added. The mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:0.2. The two are mixed evenly to obtain the first compound capping agent in a molten state, which is then set aside.

[0044] Prepare the second compound capping agent according to the following procedure: In the end-capping agent mixing tank B, 4,4'-difluorobenzophenone is heated to a molten state at a temperature of 125°C, and then Li2SO4 is added, wherein the mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:6. The two are mixed evenly to obtain a second compound end-capping agent in a molten state for later use. Preparation of alkali metal salts: Sodium carbonate and potassium carbonate in a mass ratio of 1:0.5 are stirred to mix them evenly to obtain a compound alkali metal salt for later use.

[0045] The synthesis of polyetheretherketone is carried out according to the following procedure: High-purity nitrogen gas was introduced to replace the air in the polymerization reactor, and the reactor temperature was simultaneously controlled to 150°C. Then, hydroquinone, fluoroketone (4,4'-difluorobenzophenone), alkali metal salt, and diphenyl sulfone were added to the polymerization reactor, and the temperature was slowly increased in a stepwise manner (in this embodiment, the stepwise heating conditions were specifically set as follows: first, the temperature was increased to 245°C at a rate of 15°C / min, and then increased to 320°C at a rate of 10°C / min) to 320°C for polymerization reaction (polymerization reaction time was 3 hours). During the polymerization reaction, the progress of the reactants in the polymerization reactor was monitored in real time by online monitoring equipment. Cool down to 310℃, add the first compound end-capping agent for a first end-capping treatment for 10 minutes, then cool down again to 260℃, add the second compound end-capping agent for a second end-capping treatment, and end the end-capping treatment after 15 minutes. The discharge valve of the polymerization reactor is opened and the material is discharged into the tablet press through a closed pipeline to obtain crude PEEK resin (i.e., polyether ether ketone). The crude PEEK resin is pressed into thin sheets, and the sheets are then refined and processed (including crushing, washing and drying processes) to obtain polyether ether ketone products. In this Example 2, the feeding ratio of each material is set as follows: diphenyl sulfone: sodium carbonate: hydroquinone: fluoroketone = 3.1:1.02:1.15:1, wherein the feeding amount of fluoroketone is 698.24g (approximately 3.2mol); the molar ratio of fluorinated end-capping agent to hydroquinone in the first compound end-capping agent is 1:60; the molar ratio of fluorinated end-capping agent to hydroquinone in the second compound end-capping agent is 1:200.

[0046] In this Example 2, the polyetheretherketone compound was purified and post-treated according to the following process: The thin sheet is fed into a pulverizer and then crushed into smaller particles. The pulverized particles are then washed with ethanol, washed with water, and dried in sequence. High-purity nitrogen is introduced into the ethanol washing tank, water washing tank, and dryer for atmosphere protection during operation.

[0047] The initial thermal decomposition temperature of the polyether ether ketone obtained in Example 2 was found to be 581.6℃, and its PDI distribution value was 2.02.

[0048] Example 3:

[0049] Prepare the first compound capping agent according to the following procedure: In the capping agent mixing tank A, 4,4'-difluorobenzophenone (i.e., the fluorinated capping agent) is heated to a molten state at a temperature of 125°C, and then Li2SO4 is added. The mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:0.8. The two are mixed evenly to obtain the first compound capping agent in a molten state, which is then set aside.

[0050] Prepare the second compound capping agent according to the following procedure: In the end-capping agent mixing tank B, 4,4'-difluorobenzophenone is heated to a molten state at 125°C, and then Li2SO4 is added, wherein the mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:1. The two are mixed evenly to obtain a second compound end-capping agent in a molten state, which is then set aside. Preparation of alkali metal salts: Sodium carbonate and potassium carbonate in a mass ratio of 1:0.5 are stirred to mix them evenly to obtain a compound alkali metal salt for later use.

[0051] The synthesis of polyetheretherketone is carried out according to the following procedure: High-purity nitrogen gas was introduced to replace the air in the polymerization reactor, and the reactor temperature was simultaneously controlled to 150°C. Then, hydroquinone, fluoroketone (4,4'-difluorobenzophenone), alkali metal salt, and diphenyl sulfone were added to the polymerization reactor, and the temperature was slowly increased in a stepwise manner (in this embodiment, the stepwise heating conditions were specifically set as follows: first, the temperature was increased to 245°C at a rate of 15°C / min, and then increased to 320°C at a rate of 10°C / min) to 320°C for polymerization reaction (polymerization reaction time was 3 hours). During the polymerization reaction, the progress of the reactants in the polymerization reactor was monitored in real time by online monitoring equipment. Heat to 330℃, add the first compound end-capping agent for a first end-capping treatment for 20 minutes, then cool to 300℃, add the second compound end-capping agent for a second end-capping treatment, and end the end-capping treatment after 25 minutes. The discharge valve of the polymerization reactor is opened and the material is discharged into the tablet press through a closed pipeline to obtain crude PEEK resin (i.e., polyether ether ketone). The crude PEEK resin is pressed into thin sheets, and the sheets are then refined and processed (including crushing, washing and drying processes) to obtain polyether ether ketone products. In this Example 3, the feeding ratio of each material is set as follows: diphenyl sulfone: sodium carbonate: hydroquinone: fluoroketone = 3.1:1.02:1.15:1, wherein the feeding amount of fluoroketone is 698.24g (approximately 3.2mol); the molar ratio of fluorinated end-capping agent to hydroquinone in the first compound end-capping agent is 1:100; the molar ratio of fluorinated end-capping agent to hydroquinone in the second compound end-capping agent is 1:150.

[0052] In this embodiment 3, the polyetheretherketone compound is purified and post-processed according to the following procedure: The thin sheet is fed into a pulverizer and then crushed into smaller particles. The pulverized particles are then washed with ethanol, washed with water, and dried in sequence. High-purity nitrogen is introduced into the ethanol washing tank, water washing tank, and dryer for atmosphere protection during operation.

[0053] The polyether ether ketone obtained in Example 3 was tested and found to have an initial thermal decomposition temperature of 583.9°C and a PDI distribution value of 1.99.

[0054] Example 4: The remaining technical solutions of Example 4 are the same as those of Example 1, except that in Example 4:

[0055] Prepare the first compound capping agent according to the following procedure: In the capping agent mixing tank A, 4,4'-difluorobenzophenone and Li2SO4 are mixed evenly at room temperature (about 26°C), wherein the mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:0.5, to obtain the first compound capping agent (in solid phase), which is then set aside.

[0056] Prepare the second compound capping agent according to the following procedure: In the end-capping agent mixing vessel B, 4,4'-difluorobenzophenone and Li2SO4 are mixed evenly at room temperature (approximately 26°C), wherein the mass ratio of 4,4'-difluorobenzophenone to anhydrous lithium sulfate Li2SO4 is 1:3, to obtain the second compound end-capping agent (in solid phase), which is then set aside.

[0057] The polyether ether ketone obtained in Example 4 was tested and found to have an initial thermal decomposition temperature of 580.8°C and a PDI distribution value of 2.13.

[0058] Example 5: The remaining technical solutions of Example 5 are the same as those of Example 1, except that in Example 5: Prepare alkali metal salts: Sodium carbonate is used as the alkali metal salt and is prepared for later use.

[0059] The polyether ether ketone obtained in Example 5 was tested and found to have an initial thermal decomposition temperature of 582.7°C and a PDI distribution value of 2.07.

[0060] Comparative Example 1: The rest of the technical solutions of Comparative Example 1 are the same as those of Example 1, except that in Comparative Example 1, the second compound capping agent added in Example 1 is replaced with the first compound capping agent.

[0061] The initial thermal decomposition temperature of the polyetheretherketone obtained in Comparative Example 1 was found to be 580.5℃, and its PDI distribution value was 2.32.

[0062] Comparative Example 2: The rest of the technical solutions of Comparative Example 2 are the same as those of Example 1, except that the first compound capping agent added in Example 1 is replaced with the second compound capping agent in Comparative Example 2.

[0063] The initial thermal decomposition temperature of the polyether ether ketone obtained in Comparative Example 2 was found to be 575.3℃, and its PDI distribution value was 2.43.

[0064] Comparative Example 3: The rest of the technical solutions of Comparative Example 3 are the same as those of Example 1, except that the order of adding the first compound capping agent and the second compound capping agent in Example 1 is changed in Comparative Example 3. That is, in Comparative Example 3, the second compound capping agent is added for a first capping treatment at a temperature of 320°C for 15 minutes, then the temperature is lowered to 280°C, the first compound capping agent is added for a second capping treatment, and the capping treatment is completed after 20 minutes.

[0065] The initial thermal decomposition temperature of the polyetheretherketone obtained in Comparative Example 3 was found to be 571.3℃, and its PDI distribution value was 2.67.

[0066] Comparative Example 4: The remaining technical solutions of Comparative Example 4 are the same as those of Example 1, except that the anhydrous lithium sulfate Li2SO4 in the first compound capping agent and the second compound capping agent is removed in Comparative Example 4.

[0067] The initial thermal decomposition temperature of the polyetheretherketone obtained in Comparative Example 4 was found to be 568.4℃, and its PDI distribution value was 3.05.

[0068] Comparative Example 5: The remaining technical solutions of Comparative Example 5 are the same as those of Example 1, except that the fluorinated end-capping agent in the first compound end-capping agent and the second compound end-capping agent is removed in Comparative Example 5.

[0069] The initial thermal decomposition temperature of the polyether ether ketone obtained in Comparative Example 5 was found to be below 560°C. Because its thermal stability clearly did not meet the requirements, its PDI distribution value was not tested (it is expected to have a wide distribution).

[0070] Comparative Example 6: The remaining technical solutions of Comparative Example 6 are the same as those of Example 1, except that in Comparative Example 6, the anhydrous lithium sulfate (Li2SO4) in the first compound capping agent and the second compound capping agent are replaced with anhydrous sodium sulfate.

[0071] The initial thermal decomposition temperature of the polyether ether ketone obtained in Comparative Example 6 was found to be 567.7℃, and its PDI distribution value was 2.92.

[0072] Comparative Example 7: The remaining technical solutions of Comparative Example 7 are the same as those of Example 1, except that in Comparative Example 7, the anhydrous lithium sulfate Li2SO4 in the first compound capping agent and the second compound capping agent are replaced with lithium chloride LiCl.

[0073] The initial thermal decomposition temperature of the polyether ether ketone obtained in Comparative Example 7 was 572.5℃, and its PDI distribution value was 2.69.

[0074] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0075] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing polyetheretherketone, characterized in that, High-purity inert gas is introduced to replace the air in the polymerization reactor. Hydroquinone, fluoroketone, and alkali metal salt undergo polymerization under solvent atmosphere and gradient temperature conditions. The alkali metal salt used is sodium carbonate and / or potassium carbonate. After the polymerization reaction, end-capping treatment is performed as follows: Under a temperature of 310-330℃, a first compound end-capping agent is added, and a polymerization end-capping reaction is carried out for at least 5 minutes. The first compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate (Li2SO4) in a mass ratio of 1:0.2-0.

8. Under a temperature of 260-300℃, a second compound end-capping agent is added, and the polymerization end-capping reaction is continued for at least 10 minutes. The second compound end-capping agent is a mixture of a fluorinated end-capping agent and anhydrous lithium sulfate Li2SO4 in a mass ratio of 1:1-6. The obtained reaction product was post-processed to obtain polyether ether ketone.

2. The method for preparing polyetheretherketone according to claim 1, characterized in that, The initial thermal decomposition temperature of the polyether ether ketone is not lower than 580°C, and the PDI distribution value of the polyether ether ketone is controlled within the range of 2.

2.

3. The method for preparing polyetheretherketone according to claim 2, characterized in that, The initial thermal decomposition temperature range of the polyether ether ketone is 582-595℃, and the PDI distribution value of the polyether ether ketone is controlled within the range of 1.8-2.

1.

4. The method for preparing polyetheretherketone according to claim 1, characterized in that, Both the first compound end-capping agent and the second compound end-capping agent are added to the polymerization reactor in a molten state.

5. The method for preparing polyetheretherketone according to claim 4, characterized in that, In preparing the first or second compound capping agent, the fluorine-containing capping agent is preheated to a molten state, and then its corresponding anhydrous lithium sulfate (Li2SO4) is added to the molten fluorine-containing capping agent and mixed evenly.

6. The method for preparing polyetheretherketone according to claim 1, characterized in that, The molar ratio of the fluorinated capping agent to hydroquinone in the first compound capping agent is 1:60-100; the molar ratio of the fluorinated capping agent to hydroquinone in the second compound capping agent is 1:150-200.

7. The method for preparing polyetheretherketone according to claim 1, characterized in that, Add the second compound end-capping agent 10-20 minutes after adding the first compound end-capping agent, and end the end-capping treatment 15-25 minutes later.

8. The method for preparing polyetheretherketone according to claim 1, characterized in that, The mass ratio of the solvent, alkali metal salt, hydroquinone, and fluoroketone is 3-3.6:1-1.2:1-1.5:1; the alkali metal salt is a mixture of sodium carbonate and potassium carbonate, wherein the mass ratio of sodium carbonate to potassium carbonate is in the range of 1:0.1-0.

5.

9. The method for preparing polyetheretherketone according to claim 1, characterized in that, While purging the air in the polymerization reactor with high-purity inert gas, the reactor temperature is simultaneously controlled to 140-160℃. Then, the raw materials are added into the polymerization reactor, and the temperature inside the reactor is gradually increased to 310-330℃ to carry out the polymerization reaction. The polymerization reaction takes 2.5-4 hours.

10. The method for preparing polyetheretherketone according to claim 1, characterized in that, The gas generated by the reaction in the polymerization reactor enters the polymerization reactor heat exchanger through a pipeline. A small amount of raw materials and reaction products discharged with the gas are returned to the polymerization reactor through the heat exchange system. The tail gas is discharged through the exhaust port of the polymerization reactor heat exchanger. After the end-sealing process is completed, the discharge valve of the polymerization reactor is opened and the reaction products are discharged into the tablet press through a closed pipeline to obtain crude polyether ether ketone. The crude polyether ether ketone is pressed into thin sheets, and the thin sheets are crushed, washed and dried to obtain the polyether ether ketone.

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