Synthesis method of high-performance thermoplastic polyether-ether-ketone

Abstract

The invention belongs to the technical field of high polymer material synthesis, discloses a high-performance thermoplastic polyether-ether-ketone synthesis method, and aims to solve the problems that polymerization kinetics is out of control and a molecular structure is difficult to regulate and control due to a high-activity catalytic system in the prior art. The core of the method is that a homogeneous-phase dissolved organic base catalysis system is adopted, a proton shuttle equilibrium mechanism is introduced to buffer the reaction activity, and the polymerization process is precisely regulated and controlled through stoichiometric closed-loop control based on a process analysis technology. The method comprises the steps of homogeneous precursor construction, low-temperature oligomerization under the control of a process analysis technology, programmed heating chain extension, active chain termination and catalyst passivation, structured graded purification and the like. The polyether-ether-ketone prepared by the invention has narrow molecular weight distribution (PDI is lower than 1.8) and excellent batch consistency, and is suitable for the high-end fields of aerospace, medical treatment and the like.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis technology, and more specifically, relates to a high-performance thermoplastic polyether ether ketone synthesis method. Background Technology

[0002] Polyetheretherketone (PEEK), a semi-crystalline thermoplastic engineering plastic, possesses superior properties such as high temperature resistance, high mechanical strength, chemical corrosion resistance, self-lubrication, and biocompatibility due to the large number of aromatic rings, stable ether bonds, and carbonyl groups in its molecular backbone. It has become a key material in cutting-edge fields such as aerospace, advanced medical devices, and new energy vehicles, and its technological level is an important indicator of a nation's strength in high-end polymer materials. Current advanced industries are placing even higher demands on its molecular structure uniformity, batch stability, and overall performance.

[0003] Industrially, PEEK is mainly prepared by nucleophilic aromatic substitution polycondensation reaction, using 4,4'-difluorobenzophenone (DFBP) and hydroquinone (HQ) as core monomers. The reaction takes place in a high-temperature polar aprotic solvent such as diphenyl sulfone, with a weakly basic alkali metal carbonate as a catalyst and acid-binding agent. During the reaction, the hydroquinone hydroxyl group forms a phenoxy anion under alkaline conditions, which attacks the activated fluorine atom of DFBP, leading to nucleophilic substitution, ether bonding, and chain growth. Finally, through raw material pretreatment, high-temperature salt-forming polycondensation, and post-treatment such as cooling, purification, and drying, PEEK conforming to general standards can be stably produced, laying the foundation for its commercialization.

[0004] However, existing technologies are showing limitations in meeting higher performance demands. To improve efficiency, reduce energy consumption, and obtain higher molecular weight products, the industry has attempted to use highly active catalysts (such as cesium carbonate) and phase transfer catalysts, or to control molecular chain growth through staged polymerization. However, highly active catalytic systems significantly increase reaction rates, making the polymerization system much more sensitive to process parameters. In traditional heterogeneous systems, this can easily lead to runaway reactions: rapid local reactions in the early stages of polymerization broaden the molecular weight distribution, and an oligomer "passivation layer" forms on the surface of phenolic salt particles, resulting in uneven conversion and increased side reactions; the high-temperature chain extension stage further amplifies the heterogeneity, resulting in a wide or even bimodal molecular weight distribution of the final product, containing a large amount of oligomers and a small amount of ultra-high molecular weight components, leading to unstable batch performance of the product (such as fluctuations in glass transition temperature Tg and melting point Tm, and increased dispersion of mechanical properties), making it difficult to meet the stringent requirements for reliability and consistency in aerospace-grade components, implantable medical devices, and other applications.

[0005] In summary, the core challenge of existing PEEK synthesis technologies lies in the inherent conflict between high reactivity and precise control of polymer molecular structure (especially molecular weight distribution). Simply combining highly active catalysts with staged heating can actually exacerbate molecular structural inhomogeneity due to the increased sensitivity of the reaction system. Therefore, developing a high-performance PEEK with narrow molecular weight distribution, low impurities, and consistent batch-to-batch performance that can improve efficiency using highly active catalytic systems while fundamentally suppressing runaway polymerization kinetics and precisely controlling each stage of nucleation, oligomerization, and chain extension has become a critical technical challenge that urgently needs to be addressed. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned deficiencies in the prior art and provide a high-performance method for synthesizing thermoplastic polyetheretherketone (PEEK). This method aims to resolve the inherent contradiction between the runaway polymerization kinetics caused by highly active catalytic systems and the precise control of polymer molecular structure. By constructing a novel homogeneous polymerization environment with precise buffering and control over kinetics, and combining real-time process monitoring with stoichiometric closed-loop control, the entire process of polymer chain nucleation, growth, and termination can be precisely controlled. Ultimately, this method stably produces PEEK materials with extremely narrow molecular weight distribution, low structural defect density, minimal impurity residue, and highly consistent batch-to-batch performance.

[0007] To achieve the aforementioned objectives, this invention provides a high-performance method for synthesizing thermoplastic polyetheretherketone (PEEK). This method abandons the traditional heterogeneous reaction system that relies on solid-phase alkali metal salts as acid-binding agents and catalysts. Instead, it employs an organic-base catalytic system based on homogeneous dissolution and introduces a proton shuttle equilibrium mechanism to construct a kinetic environment where reactivity is precisely buffered. The core of this method lies in transforming the explosive nucleophilic substitution reaction at the solid-liquid interface, which is difficult to control in traditional processes, into a stable and controllable polymerization process that occurs uniformly throughout the entire liquid volume, with the reaction rate regulated by a reversible proton transfer equilibrium. By unifying the seemingly contradictory elements of high reactivity and process controllability within a synergistic, multi-level control framework, this method fundamentally suppresses the technical problems of widened molecular weight distribution, increased side reactions, and unstable macroscopic properties caused by excessively rapid local reaction rates.

[0008] The method includes the following steps: S1. Construction and activation of homogeneous reaction precursor systems: (1) In a reaction vessel that has been replaced and purged with an inert gas, the first monomer hydroquinone (HQ) and the polar aprotic solvent diphenyl sulfone that has been deeply dehydrated are added and stirred at 60-80°C to dissolve and form a homogeneous solution. (2) Add 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to the solution, wherein the molar ratio of DBU to HQ is 2.02:1.00-2.10:1.00, to generate hydroquinone divalent anion and protonated DBU cation (DBUH) in situ. + Ion-pair complexes of ) (3) Add 2,6-di-tert-butylphenol, a proton shuttle agent used to form a proton shuttle equilibrium with the divalent anion of hydroquinone to buffer the polymerization reaction activity, wherein the molar ratio of 2,6-di-tert-butylphenol to HQ is 0.05:1.00-0.15:1.00, to form a homogeneous reaction precursor system; The highly reactive hydroquinone divalent anion undergoes a proton exchange with 2,6-di-tert-butylphenol, generating a neutral hydroquinone molecule with significantly reduced reactivity and a relatively mild 2,6-di-tert-butylphenol anion. This equilibrium greatly reduces the steady-state concentration of the hydroquinone divalent anion, which is the main nucleophilic attacking species, present instantaneously in the system, maintaining it at an extremely low level determined by the equilibrium constant and the concentrations of each component. Therefore, the apparent reactivity of the entire system is "buffered" to a mild and stable state, laying the kinetic foundation for the orderly progress of subsequent polymerization reactions. S2. Low-temperature oligomerization reaction based on process analysis technology: (1) Heat the system in step S1 to 140~160℃ and monitor the changes in the characteristic absorption peaks of the hydroquinone hydroxyl group (3200-3400cm) and the carbonyl group of the second monomer 4,4'-difluorobenzophenone (1650cm) in real time by in-situ attenuated total reflection Fourier transform infrared spectroscopy. -1-1 (2) Based on the monitoring results, the dropping rate of 4,4'-difluorobenzophenone is dynamically adjusted by the proportional-integral-derivative control algorithm to maintain the instantaneous molar ratio of the two monomers at 1.000±0.005 until the total monomer conversion rate reaches 90-95% to obtain the oligomer. S3. High-temperature chain extension reaction under programmed temperature control: After confirming that the total molar ratio of the residual monomers in step S2 is 1.0000±0.0005, the system temperature is increased from 140-160℃ to 280-320℃ at a rate of 0.4-0.8℃ / min. At the same time, the viscosity of the system is monitored by an online rotational viscometer. When the viscosity reaches the preset viscosity value corresponding to the target molecular weight (e.g., 850±50 Pa·s corresponding to a number-average molecular weight of 35,000 g / mol), and the growth rate is less than 1% within 30 minutes near this viscosity value, the chain extension reaction is terminated. The preset viscosity value is a value corresponding to the target molecular weight, determined based on an empirical relationship curve between online viscosity and polymer number-average molecular weight (GPC method) established in advance under the same reaction conditions. S4. Precisely quantified active chain termination and catalyst passivation: (1) Add the monofunctional end-capping agent 4-fluorobenzophenone to the system in step S3 and react for 15-30 minutes until the characteristic peak of phenolic anion cannot be detected by the attenuated total reflectance Fourier transform infrared spectrum. (2) Chloromethane gas is introduced, wherein the molar amount of chloromethane is in excess of the DBU added in step S1, so that the residual DBU and protonated DBUH are... + A quaternization reaction occurs, generating a chemically stable N-methyl-DBU cation, thereby completely and permanently passivating the catalytic system and preventing any undesirable chemical changes during subsequent processing or product use. Specifically, chloromethane gas can be bubbled into the polymer melt at 280-320°C through a perforated annular pipe at the bottom of the reactor, while maintaining the pressure inside the reactor at 0.1-0.2 MPa and keeping it vigorously stirred to promote gas-liquid mass transfer until no chloromethane is detected in the tail gas. S5. Structured fractionation purification and post-processing: (1) The system in step S4 is thoroughly mixed with N-methyl-2-pyrrolidone (NMP) at a temperature maintained at 150°C using a static mixer in a countercurrent or cross-current manner to carry out the first stage of extraction, remove low molecular weight oligomers, and obtain the polymer-diphenyl sulfone concentrate after the first stage of thermal NMP extraction. (2) The polymer-diphenyl sulfone concentrate is contacted with acetone in a continuous stirred tank with a filter screen to precipitate the polymer and extract residual solvent and salt impurities; (3) After washing with deionized water, the polymer is dried to a volatile content of less than 0.1% by continuously crushing and turning it during the drying process at 160-180℃ and a vacuum degree of <100Pa. Then, it is melt-extruded and pelletized by a twin-screw extruder to obtain the polyether ether ketone product.

[0009] Furthermore, in step S1, the reactor is made of Hastelloy or lined with glass and equipped with an anchor or combined stirrer and a temperature control jacket system. The inert gas is argon with a purity of 99.999% by volume, and the number of displacement-purging cycles is ≥3.

[0010] Furthermore, in step S1, the purity of the hydroquinone is >99.95% as determined by high performance liquid chromatography, and it is dried in a vacuum oven at 120°C for ≥24 hours; The water content of the diphenyl sulfone was determined to be <5 ppm by the Karl Fischer coulometric method.

[0011] Furthermore, in step S1, the purity of the DBU is >99.5%; and the purity of the 2,6-di-tert-butylphenol is >99.0%.

[0012] Furthermore, in step S2, the purity of the 4,4'-difluorobenzophenone is >99.98% as determined by gas chromatography, and it is dried in a vacuum oven at 120°C for ≥24 hours. The 4,4'-difluorobenzophenone is pre-dissolved in deeply dehydrated diphenyl sulfone to form a standard concentration solution, which is then stored in a constant pressure dropping tank. The dropping tank is connected to the reaction vessel via a high-precision mass flow controller.

[0013] Furthermore, in step S2, the monitoring frequency of the attenuated total reflection Fourier transform infrared spectrum is ≥ 1 time / minute; The objective of the proportional-integral-derivative control is to maintain the integrated area of ​​the infrared absorption peak of the unreacted hydroquinone hydroxyl group at a preset constant value. The proportional-integral-derivative (PID) control algorithm is implemented as follows: the controller compares the integral area of ​​the characteristic absorption peak of the hydroquinone hydroxyl group, which is monitored in real time by in-situ attenuated total reflection Fourier transform infrared spectroscopy, with a constant threshold preset according to the target oligomer chain length and reaction rate, and generates a deviation signal; the PID controller calculates the output adjustment amount of the mass flow controller for 4,4'-difluorobenzophenone dropping according to the deviation signal and preset proportional, integral, and derivative parameters, thereby dynamically adjusting the dropping speed to minimize the deviation between the real-time value and the set value of the characteristic peak integral area.

[0014] Furthermore, in step S3, the stirrer speed is increased simultaneously during the heating process to accommodate the increase in system viscosity.

[0015] Further, in step S4, the amount of 4-fluorobenzophenone added is determined based on the initial total monomer molar amount and the target molecular weight, and is pre-dissolved in deeply dehydrated diphenyl sulfone.

[0016] The beneficial effects of this invention are: This invention creatively designs a novel synthetic framework based on homogeneous organic base activation, proton shuttle equilibrium buffering, closed-loop control of process analysis techniques, and multi-stage structural purification, successfully resolving the fundamental contradiction between high reactivity and precise molecular structure control in existing technologies. The polyether ether ketone (PEEK) prepared by this method exhibits unprecedented narrow molecular weight distribution (polydispersity index PDI value below 1.8), extremely low oligomer content, and excellent batch-to-batch reproducibility due to precise kinetic and stoichiometric control throughout the polymerization process. This meets the stringent requirements for extreme material performance and reliability in the most demanding applications such as aerospace and implantable medical devices. Attached Figure Description

[0017] Figure 1 This is a schematic flowchart of a high-performance thermoplastic polyether ether ketone synthesis method provided by the present invention.

[0018] Figure 2 This is a schematic diagram of the chemometric closed-loop control system based on process analysis technology in the method of this invention. Detailed Implementation

[0019] This invention discloses a high-performance method for synthesizing thermoplastic polyether ether ketone (PEEK). The core of this method lies in constructing a homogeneous polymerization environment with precise buffering and regulation of kinetics, and integrating process analysis techniques to achieve closed-loop stoichiometry control, thereby precisely controlling the entire process of polymer chain nucleation, growth, and termination. Figure 1 , Figure 2 The implementation of this method fundamentally overcomes the technical challenges in traditional heterogeneous polymerization processes, such as the widening of molecular weight distribution, increased side reactions, and inconsistent batch performance caused by the uncontrollability of solid-liquid interface reactions.

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the present application will be further described in detail below with reference to the embodiments.

[0021] Example 1 This embodiment fully follows the method described in this invention to synthesize high-performance polyetheretherketone. Specific feed amounts and key process parameters are as follows: (1) Polymerization reactor: 200-liter Hastelloy C-276 alloy reactor, equipped with anchor stirrer (speed adjustable from 0 to 300 rpm) and jacketed temperature control system (temperature control accuracy ±1℃), and purged 5 times with 99.999% pure argon gas.

[0022] (2) Raw material pretreatment: The first monomer, hydroquinone (HQ), with a purity of 99.98%, weighed 33.04 kg (300.0 mol) and dried in a vacuum oven at 120°C for 24 hours, had a moisture content of 8 ppm.

[0023] The second monomer, 4,4'-difluorobenzophenone, with a purity of 99.99%, weighed 65.47 kg (300.0 mol), and was dried in a vacuum oven at 120°C for 24 hours. It was then dissolved in 45.0 kg of diphenyl sulfone and stored in a constant pressure dropping tank equipped with a high-precision mass flow controller.

[0024] The polymerization solvent, diphenyl sulfone, has a water content of 4 ppm and is weighed in a quantity of 150.0 kg, of which 105.0 kg is used to dissolve HQ and 45.0 kg is used to dissolve 4,4'-difluorobenzophenone.

[0025] Organic base catalyst: DBU, purity 99.99%, 94.11 kg (618 mol), molar ratio with HQ 2.06:1.00, deeply dehydrated by molecular sieve.

[0026] The proton shuttle 2,6-di-tert-butylphenol, with a purity of 99.5%, weighs 6.22 kg (30 mol) and has a molar ratio of 0.10:1.00 with HQ.

[0027] (3) Reaction steps: Preparation of homogeneous precursor: HQ and diphenyl sulfone were dissolved by stirring at 60℃, DBU was added and stirred for 30 minutes to form an ion-pair complex, then a proton shuttle was added and kept at 80℃ for 10 minutes to form a homogeneous system (transmittance >95%).

[0028] Low-temperature polymerization: The temperature was raised to 150℃, and the changes of the 3200-3400cm (phenolic hydroxyl) and 1650cm (carbonyl) peaks were monitored every 30 seconds using in-situ attenuated total reflectance Fourier transform infrared spectroscopy. The dropping rate of the second monomer was adjusted by a proportional-integral-differential algorithm to maintain an instantaneous molar ratio of 1.000±0.005. After 3.5 hours, the conversion rate reached 93%. -1-1 High-temperature chain extension: After confirming the residual monomer molar ratio of 1.0000±0.0005, the polymerization temperature was increased from 150℃ to 300℃ at a rate of 0.6℃ / min, while the stirring speed was increased to 250rpm. The viscosity was monitored at 850Pa・s by an online rotational viscometer and stabilized for 30 minutes before termination.

[0029] End-capping and passivation: Add 1.52 kg of 4-fluorobenzophenone (dissolved in 5 kg of diphenyl sulfone), react for 20 minutes until the phenol oxide anion peak disappears; introduce 620 mol of chloromethane, react at 120 °C for 40 minutes to complete quaternization.

[0030] Post-purification treatment: remove oligomers by hot NMP countercurrent extraction at 150℃, precipitate polymers with acetone, wash with deionized water until conductivity <10μS / cm; vacuum dry at 170℃ and 50Pa for 6 hours (with crushing function), volatile matter 0.08%; pelletized by twin-screw extrusion (3mm×3mm).

[0031] The final product was tested, and its performance parameters are shown in Table 1 below.

[0032] Example 2 Polymerization reactor: 200-liter glass-lined reactor, equipped with an anchor stirrer (speed adjustable from 0-300 rpm) and a jacketed temperature control system (temperature control accuracy ±1℃), and purged 5 times with 99.999% pure argon gas.

[0033] The total amount of raw materials was the same as in Example 1: DBU purity 99.99%, 92.28 kg (606 mol), with a molar ratio of 2.02:1.00 to HQ; 2,6-di-tert-butylphenol purity 99.5%, 3.11 kg (15 mol), with a molar ratio of 0.05:1.00 to HQ; oligomerization temperature 140°C, chain extension heating rate 0.4°C / min (final temperature 280°C).

[0034] The remaining operating steps are the same as in Example 1.

[0035] Example 3 The polymerization reactor and total amount of raw materials were the same as in Example 1. DBU purity was 99.99%, 95.94 kg (630 mol), with a molar ratio of 2.10:1.00 to HQ; 2,6-di-tert-butylphenol purity was 99.5%, 9.33 kg (45 mol), with a molar ratio of 0.15:1.00 to HQ; the oligomerization temperature was 160℃, and the chain extension heating rate was 0.8℃ / min (final temperature 320℃).

[0036] The remaining operating steps are the same as in Example 1.

[0037] Comparative Example 1 This comparative example uses a traditional, inorganic base-based heterogeneous polymerization method to synthesize polyether ether ketone.

[0038] Raw materials and equipment: The amounts of HQ, 4,4'-difluorobenzophenone, and diphenyl sulfone, as well as the reaction vessel, are the same as in Example 1, except that the catalyst is replaced with anhydrous potassium carbonate.

[0039] Catalyst: 43.75 kg (315.0 mol) of anhydrous potassium carbonate (purity 99.5%), vacuum dried at 200℃ for 4 hours, and ground to a particle size <100 μm.

[0040] Reaction steps: (1) Add HQ, 4,4'-difluorobenzophenone and 150.0 kg of diphenyl sulfone, stir and dissolve at 160°C (200 rpm), and add potassium carbonate powder.

[0041] (2) Stepwise heating reaction: 180℃ / 1h→220℃ / 1h→280℃ / 1h→310℃ / 2h. The reaction ends by measuring the stirring torque (end point 80 N·m).

[0042] (3) Post-processing: After natural cooling, the powder was crushed, extracted with acetone at 80℃ for 24 hours, washed with deionized water 5 times, and vacuum dried at 175℃ for 12 hours (no breakage, agglomerated particle size >20mm).

[0043] The final product was tested, and its performance parameters are shown in Table 1 below.

[0044] Comparative Example 2 This comparative example uses a traditional method of synthesizing polyether ether ketone based on a highly active catalyst.

[0045] The total amount of raw materials was the same as in Example 1, except that the catalyst was replaced with 49.85 kg of cesium carbonate (153 mol, molar ratio 0.51:1.00), and the rest was the same as in Comparative Example 1.

[0046] Comparative Example 3 The same synthesis method as in this invention is used, but the proton shuttle is omitted.

[0047] The total amount of raw materials is the same as in Example 1, except that 2,6-di-tert-butylphenol is removed, and the rest of the process is the same.

[0048] The comparative data in Table 1 clearly show that the polyetheretherketone (PEEK) prepared by the homogeneous, buffered, and closed-loop controlled synthesis method described in this invention (Examples 1-3) exhibits significant superiority in several key performance indicators compared to products prepared by traditional heterogeneous methods (Comparative Example 1), traditional highly active catalysts (Comparative Example 2), and the method of this invention omitting the proton shuttle (Comparative Example 3). Specifically, the method of this invention enables precise control of molecular weight, yielding products with higher number-average molecular weights (35,200 g / mol in Example 1, 34,900 g / mol in Example 2, and 34,200 g / mol in Example 3) and extremely narrow molecular weight distribution (PDI values ​​as low as 1.75-1.77). In contrast, the comparative examples exhibit significantly wider molecular weight distributions (2.80 in Comparative Example 1, 3.50 in Comparative Example 2, and 2.31 in Comparative Example 3), directly reflecting the high controllability of the polymerization process in this invention.

[0049] Furthermore, the glass transition temperature (144.5-145.1℃) and melting temperature (343.5-344.2℃) of the products in Examples 1-3 are higher than those of the comparative products (Comparative Example 1: Tg 143.5℃, Tm 341.8℃; Comparative Example 2: Tg 142.8℃, Tm 340.5℃; Comparative Example 3: Tg 144.0℃, Tm 342.5℃), indicating that their crystallization is more complete and their chain structure is more regular.

[0050] Regarding thermal stability, the product of this invention exhibits a significantly higher 5% thermogravimetric temperature (581-585℃) than the comparative products (552℃ for Comparative Example 1, 540℃ for Comparative Example 2, and 565℃ for Comparative Example 3) due to effective end-capping and catalyst passivation / removal. Furthermore, the residual catalyst ion content is extremely low (<1ppm), far lower than 85ppm for Comparative Example 1 and 120ppm for Comparative Example 2. This is crucial for applications requiring long-term high-temperature stability.

[0051] The comparison of mechanical properties also confirmed the structural advantages of the product of the present invention. Its tensile strength (100.8-102.5MPa) and elongation at break (42-45%) are significantly better than those of the comparative products (Comparative Example 1: tensile strength 88.6MPa, elongation at break 28%; Comparative Example 2: tensile strength 76.3MPa, elongation at break 22%; Comparative Example 3: tensile strength 90.2MPa, elongation at break 35%).

[0052] Most importantly, the method of this invention demonstrates excellent batch-to-batch repeatability, with a batch-to-batch coefficient of variation for molecular weight (1.2-1.5%) significantly lower than that of traditional methods (8.5% for Comparative Example 1, 12.8% for Comparative Example 2, and 5.8% for Comparative Example 3). This is of decisive significance for the large-scale industrial production of high-quality, stable polyetheretherketone (PEEK) materials. These data objectively and quantitatively confirm the advanced nature and practical value of the technical solution of this invention.

[0053] Table 1. Performance comparison of polyetheretherketone synthesized in the examples and comparative examples.

Claims

1. A method for synthesizing high-performance polyetheretherketone, characterized in that, Includes the following steps: S1. Construction and activation of homogeneous reaction precursor systems: (1) In a reaction vessel that has been replaced and purged with an inert gas, the first monomer hydroquinone and the polar aprotic solvent diphenyl sulfone that has been deeply dehydrated are added and stirred at 60-80°C to dissolve and form a homogeneous solution. (2) Add 1,8-diazabicyclo[5.4.0]undec-7-ene to the solution, wherein the molar ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene to hydroquinone is 2.02:1.00-2.10:1.00, thereby generating an ion-pair complex of hydroquinone divalent anion and protonated 1,8-diazabicyclo[5.4.0]undec-7-ene cation in situ; (3) Add 2,6-di-tert-butylphenol, a proton shuttle agent used to form a proton shuttle equilibrium with the divalent anion of hydroquinone to buffer the polymerization reaction activity, wherein the molar ratio of 2,6-di-tert-butylphenol to hydroquinone is 0.05:1.00-0.15:1.00, to form a homogeneous reaction precursor system; S2. Low-temperature oligomerization reaction based on process analysis technology: (1) Heat the system in step S1 to 140~160℃ and monitor the changes in the characteristic absorption peaks of the hydroquinone hydroxyl group (3200-3400cm) and the carbonyl group of the second monomer 4,4'-difluorobenzophenone (1650cm) in real time by in-situ attenuated total reflection Fourier transform infrared spectroscopy. -1-1 (2) Based on the monitoring results, the dropping rate of 4,4'-difluorobenzophenone is dynamically adjusted by the proportional-integral-derivative control algorithm to maintain the infrared absorption peak integral area of ​​the unreacted hydroquinone hydroxyl group at a preset constant value, and to maintain the instantaneous molar ratio of the two monomers at 1.000±0.005 until the total monomer conversion rate reaches 90-95% to obtain the oligomer; S3. High-temperature chain extension reaction under programmed temperature control: After confirming that the total molar ratio of the residual monomers in step S2 is 1.0000±0.0005, the system temperature is increased from 140-160℃ to 280-320℃ at a rate of 0.4-0.8℃ / min. At the same time, the viscosity of the system is monitored by an online rotational viscometer. When the viscosity reaches the preset viscosity value corresponding to the target molecular weight, and the growth rate is less than 1% within 30 minutes near this viscosity value, the chain extension reaction is terminated. The preset viscosity value is a value corresponding to the target molecular weight, determined based on an empirical relationship curve between online viscosity and polymer number-average molecular weight established in advance under the same reaction conditions. S4. Precisely quantified active chain termination and catalyst passivation: (1) Add the monofunctional end-capping agent 4-fluorobenzophenone to the system in step S3 and react for 15-30 minutes until the characteristic peak of phenolic anion cannot be detected by the attenuated total reflectance Fourier transform infrared spectrum. (2) Chloromethane gas is introduced, wherein the molar amount of chloromethane is in excess of the 1,8-diazabicyclo[5.4.0]undec-7-ene added in step S1, causing the residual 1,8-diazabicyclo[5.4.0]undec-7-ene and the protonated 1,8-diazabicyclo[5.4.0]undec-7-ene cation to undergo a quaternization reaction, thereby permanently passivating the catalytic system; S5. Structured fractionation purification and post-processing: (1) The system in step S4 is thoroughly mixed with N-methyl-2-pyrrolidone at a temperature maintained at 150°C using a static mixer in a countercurrent or cross-current manner to carry out the first stage of extraction, remove low molecular weight oligomers, and obtain a polymer-diphenyl sulfone concentrate after the first stage of thermal N-methyl-2-pyrrolidone extraction. (2) The polymer-diphenyl sulfone concentrate is contacted with acetone in a continuous stirred tank with a filter screen to precipitate the polymer and extract residual solvent and salt impurities; (3) After washing with deionized water, the polymer is dried to a volatile content of less than 0.1% by continuously crushing and turning it during the drying process at 160-180℃ and a vacuum degree of <100Pa. Then, it is melt-extruded and pelletized by a twin-screw extruder to obtain the polyether ether ketone product.

2. The method for synthesizing high-performance polyether ether ketone according to claim 1, characterized in that, In step S1, the reactor is made of Hastelloy or lined with glass and is equipped with an anchor or combined stirrer and a temperature control jacket system. The inert gas is argon with a purity of 99.999% by volume, and the number of displacement-purging cycles is ≥3.

3. The method for synthesizing high-performance polyetheretherketone according to claim 1, characterized in that, In step S1, the purity of the hydroquinone is >99.95% as determined by high performance liquid chromatography, and it is dried in a vacuum oven at 120°C for ≥24 hours. The water content of the diphenyl sulfone was determined to be <5 ppm by the Karl Fischer coulometric method.

4. The method for synthesizing high-performance polyether ether ketone according to claim 1, characterized in that, In step S1, the purity of the 1,8-diazabicyclo[5.4.0]undec-7-ene is >99.5%; the purity of the 2,6-di-tert-butylphenol is >99.0%.

5. The method for synthesizing a high-performance polyether ether ketone according to claim 1, characterized in that, In step S2, the purity of the 4,4'-difluorobenzophenone is >99.98% as determined by gas chromatography, and it is dried in a vacuum oven at 120°C for ≥24 hours. The 4,4'-difluorobenzophenone is pre-dissolved in deeply dehydrated diphenyl sulfone to form a standard concentration solution, which is then stored in a constant pressure dropping tank. The dropping tank is connected to the reaction vessel via a high-precision mass flow controller.

6. The method for synthesizing a high-performance polyether ether ketone according to claim 1, characterized in that, In step S2, the monitoring frequency of the attenuated total reflection Fourier transform infrared spectrum is ≥ 1 time / minute; The objective of the proportional-integral-derivative control is to maintain the integral area of ​​the infrared absorption peak of the unreacted hydroquinone hydroxyl group at a preset constant value.

7. The method for synthesizing high-performance polyether ether ketone according to claim 1, characterized in that, In step S3, the stirring speed is increased simultaneously during the heating process to accommodate the increase in system viscosity.

8. The method for synthesizing high-performance polyether ether ketone according to claim 1, characterized in that, In step S4, the amount of 4-fluorobenzophenone added is determined based on the initial total monomer molar amount and the target molecular weight, and is pre-dissolved in deeply dehydrated diphenyl sulfone.

Images