Polyether ether ketone and method for producing the same

Abstract

This application belongs to the field of chemical synthesis technology and discloses polyetheretherketone and its preparation method. The preparation method includes: under a protective atmosphere, reacting hydroquinone and a salt-forming agent in a composite antioxidant system to obtain a first mixture containing hydroquinone salt; reacting the first mixture with 4,4'-difluorobenzophenone to obtain a second mixture; adding a capping agent to the second mixture to carry out a capping reaction to obtain polyetheretherketone; wherein the composite antioxidant system includes diphenyl sulfone, sodium lignosulfonate, sodium metabisulfite, and sodium hypophosphite. This preparation method has few side reactions, high yield, and the prepared polyetheretherketone exhibits excellent properties.

Description

Technical Field

[0001] This application belongs to the field of chemical synthesis technology, specifically relating to polyether ether ketone and its preparation method. Background Technology

[0002] Polyetheretherketone (PEEK) is a polymer containing one ketone bond and two ether bonds in its main chain. It is a semi-crystalline special polymer material with characteristics such as high temperature resistance and chemical corrosion resistance. It can be used as a high-temperature resistant material and an electrical insulator, or combined with glass fiber or carbon fiber to prepare reinforcing materials. This material has wide applications in aerospace, medical devices as artificial bone to repair bone defects, and in industrial fields.

[0003] In related technologies, PEEK is mostly obtained through the high-temperature polycondensation of hydroquinone and 4,4'-difluorobenzophenone (DFBP). However, in the above synthesis process, hydroquinone is easily oxidized to p-benzoquinone (BQ), which to some extent affects the polymerization reaction, resulting in a wider molecular weight distribution of the final polyether ether ketone, thus affecting other properties of PEEK. Currently, in order to control the oxidation of hydroquinone, the synthesis process of PEEK needs to be carried out in an inert atmosphere, or nitrogen vacuum circulation deoxygenation technology is used during the synthesis process. However, the above methods cannot eliminate residual oxygen in the dead corners of the equipment and dissolved oxygen entrained in the raw materials, which will still cause trace amounts of hydroquinone oxidation. At the same time, the residual metal ions carried in the salting agent will further promote the oxidation phenomenon. Therefore, how to ensure the efficient and smooth progress of the PEEK synthesis process is one of the current challenges.

[0004] Application content This application aims to at least partially address one of the technical problems in the related art. To this end, this application proposes a method for preparing PEEK with fewer side reactions and higher yield, and the PEEK prepared by this method.

[0005] The first aspect of this application discloses a method for preparing polyetheretherketone, comprising: Under a protective atmosphere, hydroquinone and a salt-forming agent undergo a salt-forming reaction in a composite antioxidant system to obtain a first mixture containing hydroquinone salt; The first mixture and 4,4'-difluorobenzophenone were subjected to a polymerization reaction to obtain a second mixture; The capping agent is added to the second mixture to carry out the capping reaction, and polyether ether ketone is obtained; The composite antioxidant system includes diphenyl sulfone, sodium lignosulfonate, sodium metabisulfite, and sodium hypophosphite.

[0006] The preparation method of the first aspect of this application has at least the following beneficial effects: fewer side reactions (by eliminating all oxygen sources in the reaction process through a composite antioxidant system, achieving antioxidant control over the entire temperature range, thereby preventing the occurrence of side reactions) and high yield.

[0007] In addition, the preparation method according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the salt-forming reaction of hydroquinone and a salt-forming agent in a composite antioxidant system includes: Preparation of a composite antioxidant system; The hydroquinone and the salt-forming agent are added to the composite antioxidant system.

[0008] In some embodiments of this application, the preparation of the composite antioxidant system includes: The diphenyl sulfone is melted to obtain the diphenyl sulfone in a molten state; Sodium lignosulfonate is added to the molten diphenyl sulfone to form a suspension; The sodium metabisulfite and sodium hypophosphite are added to the suspension to obtain the composite antioxidant system.

[0009] In some embodiments of this application, at least one of the following conditions is satisfied: The melting temperature of the diphenyl sulfone is 120℃~140℃; The mass ratio of diphenyl sulfone and sodium lignosulfonate in the composite antioxidant system is 100:(5~8). The mass ratio of the sodium metabisulfite, the sodium hypophosphite, and the hydroquinone is (0.8~2):(0.3~1):100.

[0010] In some embodiments of this application, at least one of the following conditions is satisfied: The temperature for the salt formation reaction is 180℃~200℃; The salt-forming reaction takes 1 to 2 hours. The salt-forming agent includes at least one of sodium carbonate and potassium carbonate; The molar ratio of the salt-forming agent to the hydroquinone is (1.01~1.5):1, preferably (1.05~1.1):1; The molar ratio of the 4,4'-difluorobenzophenone to the hydroquinone is (1~1.015):1, preferably (1.005~1.01):1; The mass ratio of the capping agent to the 4,4'-difluorobenzophenone is (1~2):100.

[0011] In some embodiments of this application, the polymerization reaction of the first mixture and 4,4'-difluorobenzophenone includes: After heating the first mixture to 220°C~240°C, the 4,4'-difluorobenzophenone was added to obtain the third mixture; The third mixture is heated to 270°C to 290°C at a rate of 1°C / min to 2°C / min and held for 1 to 2 hours to obtain the fourth mixture; The fourth mixture is heated to 300℃~320℃ at a rate of 1℃ / min~2℃ / min and held for 1.5h~2h to obtain the second mixture.

[0012] In some embodiments of this application, at least one of the following conditions is satisfied: The capping agent includes 4,4'-difluorobenzophenone; The capping reaction takes 0.5 h to 1 h; The end-capping reaction is carried out at a temperature of 340℃-360℃.

[0013] In some embodiments of this application, the protective atmosphere comprises nitrogen and carbon dioxide, and the volume ratio of nitrogen to carbon dioxide is 10:(1~2).

[0014] In some embodiments of this application, a post-processing step is further included after the end-capping reaction is completed. The post-processing step includes at least one of precipitation, pulverization, solvent removal, desalting, and drying.

[0015] In a second aspect of this application, a polyetheretherketone (PEEK) is provided, which is prepared by the aforementioned method. The prepared PEEK has a long and narrow molecular chain, high thermal stability, good color, and excellent properties. Detailed Implementation

[0016] The embodiments of this application are described in detail below and are intended to explain this application, but should not be construed as limiting this application.

[0017] This application is based on the inventor's following discoveries and understandings: As mentioned earlier, current deoxygenation methods in PEEK preparation cannot completely remove oxygen from the reaction equipment (such as the reactor). For example, oxygen remains in the reactor even after nitrogen-vacuum purging. Hydroquinone, after being fed into the reactor, generates phenoloxy anions in an alkaline environment. These phenoloxy anions are more easily oxidized and, after being oxidized to a quinone structure in a high-temperature alkaline environment, cannot continue to participate in the polycondensation reaction, leading to premature termination of the final PEEK polymer chain, thus affecting the product's molecular chain length and properties. On the other hand, the end-capping process after the polymerization reaction can target the residual hydroquinone and the phenolic hydroxyl groups at the polymer chain ends, preventing these active groups from affecting the thermal processing properties of PEEK. However, if the phenolic hydroxyl groups have already been oxidized during the reaction, end-capping cannot proceed, further reducing the product's performance. Furthermore, hydroquinone, as the main raw material for PEEK synthesis, is easily oxidized and degrades to BQ at room temperature, leading to an imbalance in the subsequent feed ratio, affecting the polycondensation reaction, and thus impacting the product's performance.

[0018] In view of this, the first aspect of this application proposes a method for preparing polyetheretherketone, comprising: S10: Under a protective atmosphere, hydroquinone and a salt-forming agent undergo a salt-forming reaction in a composite antioxidant system to obtain a first mixture containing hydroquinone salt.

[0019] In this step, under the protection of an N2 / CO2 mixed gas, the salt-forming reaction between hydroquinone and the salt-forming agent is carried out in a composite antioxidant system to generate hydroquinone salt, yielding the first mixture. Specifically, this composite antioxidant system includes diphenyl sulfone, sodium lignosulfonate, sodium metabisulfite, and sodium hypophosphite. In this step, sodium metabisulfite in the composite antioxidant system preferentially reacts with residual oxygen in the reactor to generate sodium sulfate, while simultaneously reducing the oxide BQ (caused by the oxidation of hydroquinone before feeding) mixed in the hydroquinone raw material to hydroquinone. Meanwhile, sodium lignosulfonate acts as a dispersant here, preventing the hydroquinone salt obtained from the salt-forming reaction from agglomerating in the system.

[0020] For example, the above steps can involve adding hydroquinone and a salt-forming agent to a composite antioxidant system and reacting it at 180℃~200℃ (which can be 180℃, 185℃, 190℃, 195℃, 200℃ or any two thereof) for 1h~2h (which can be 1h, 1.5h, 2h or any two thereof). Within the above temperature and time range, the salt-forming reaction ensures the complete conversion of the phenolic hydroxyl groups to phenoxy anions (salt formation) without premature oxidation of hydroquinone due to excessively high temperatures. Simultaneously, the above time range ensures the salt-forming reaction proceeds sufficiently.

[0021] In some embodiments, the volume ratio of N2 to CO2 in the protective gas is 10:(1~2). Exemplarily, the volume ratio of N2 to CO2 can be 10:1, 10:1.5, 10:2, or any range between two of these. Nitrogen, as an inert gas, can quickly displace the air in the reactor, reducing the oxygen content. Carbon dioxide can further inhibit the activity of residual oxygen. The synergistic effect between the two is better than the deoxygenation and antioxidant protection effect of nitrogen alone.

[0022] In some embodiments, the preparation of the composite antioxidant system includes the following steps: 1. Melting diphenyl sulfone to obtain molten diphenyl sulfone; 2. Adding sodium lignosulfonate to the molten diphenyl sulfone to form a suspension; 3. Adding sodium metabisulfite and sodium hypophosphite to the suspension. Thus, the composite antioxidant system is prepared.

[0023] In the above text, diphenyl sulfone is heated to 120℃~140℃ (specifically, it can be 120℃, 125℃, 130℃, 135℃, 140℃, etc.) to obtain molten diphenyl sulfone. The melting point of diphenyl sulfone is approximately 125℃. To achieve a good dissolution and reaction environment, it is necessary to heat to the above temperature range (120℃~140℃) to form a stable homogeneous system, thereby ensuring the smooth progress of subsequent reactions.

[0024] In some embodiments, the mass ratio of diphenyl sulfone to sodium lignosulfonate in the composite antioxidant system is 100:(5~8). That is, the mass fraction of sodium lignosulfonate in the suspension is 5%~8%. Specifically, it can be 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any range between two of these. Sodium lignosulfonate is an anionic dispersant that can adsorb onto the surface of hydroquinone salt particles, forming charge repulsion and steric hindrance, preventing particle aggregation. A mass fraction of sodium lignosulfonate in the suspension within the above range ensures both the dispersion effect of sodium lignosulfonate, effectively preventing the aggregation of hydroquinone salt in the reaction system, and also prevents excessive residual sodium lignosulfonate in the system, which could lead to adsorption on the active sites of hydroquinone salt and affect the smooth progress of subsequent reactions.

[0025] In some embodiments, the amounts of sodium metabisulfite and sodium hypophosphite in the composite antioxidant system are related to the amount of hydroquinone added. Specifically, the mass ratio of sodium metabisulfite to hydroquinone in the reaction system is (0.8~2):100. Specifically, the mass ratio of the above substances can be 0.8:100, 1:100, 1.5:100, 2:100, or any range between two of these. The addition of sodium metabisulfite within the above-mentioned range can basically ensure the complete removal of residual oxygen in the system and the reduction of BQ in the raw materials to hydroquinone. Specifically, sodium metabisulfite dissolves in water to form sodium bisulfite, which can react with residual oxygen in the system to form sodium bisulfate, thereby achieving the removal of residual oxygen in the system. In addition, sodium metabisulfite can act as a reducing agent, reacting with trace amounts of BQ in the system to form hydroquinone, the chemical formula of which can be represented as: C6H4O2 (BQ) + Na2S2O5 (sodium metabisulfite) + H2O = C6H6O2 (hydroquinone) + Na2SO4 + SO2. At the same time, the amount of sodium metabisulfite added is extremely low, and it will basically not remain in the system, thus avoiding side reactions with salt-forming agents, hydroquinone salts, etc.

[0026] In some embodiments, the mass ratio of sodium hypophosphite to hydroquinone in the composite antioxidant system is (0.3~1):100. Specifically, it can be 0.3:100, 0.5:100, 0.7:100, 1:100, or any range between two of these. Within the above ratio range, the dosage of the two antioxidants in the composite antioxidant system is well-matched, achieving both primary antioxidant activity at low temperatures (sodium metabisulfite plays a role in the salt formation process) and secondary antioxidant activity at high temperatures (sodium hypophosphite plays a role in the polymerization process), thereby maximizing oxygen removal during the PEEK preparation process.

[0027] In some embodiments, the salt-forming agent includes sodium carbonate, potassium carbonate, etc. The above-mentioned salt-forming agent exhibits high stability at 180-200°C, and can undergo an acid-base reaction with the phenolic hydroxyl groups of hydroquinone to efficiently generate hydroquinone salts (phenolic anions), providing active monomers for subsequent polycondensation reactions.

[0028] In some embodiments, the molar ratio of the salt-forming agent to the hydroquinone is (1.01~1.5):1, specifically (1.05~1.1):1. Exemplary ratios can be 1.01:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, or any range thereof. An excess of salt-forming agent helps to completely convert hydroquinone to hydroquinone salt, increasing the reaction yield. Simultaneously, ensuring the alkalinity of the system is within a suitable range helps to suppress the occurrence of hydroquinone side reactions to some extent.

[0029] S20: The first mixture and 4,4'-difluorobenzophenone are subjected to a polymerization reaction to obtain a second mixture.

[0030] In this step, the first mixture obtained above is heated to 220℃~240℃, 4,4'-difluorobenzophenone is added, and the mixture is mixed evenly to obtain a third mixture; then the third mixture is heated to 270℃~290℃ at a rate of 1℃ / min~2℃ / min and held for 1h~2h to obtain a fourth mixture; the fourth mixture is heated to 300℃~320℃ at a rate of 1℃ / min~2℃ / min and held for 1.5h~2.5h to obtain the second mixture.

[0031] The following is a detailed explanation of the polymerization process described above: 4,4'-Difluorobenzophenone (DFBP) has a melting point of approximately 100°C. However, in a diphenyl sulfone solvent system, only temperatures reaching 220°C to 240°C (specifically, 220°C, 225°C, 230°C, 235°C, 240°C, etc.) can allow DFBP to completely dissolve and uniformly disperse in the system. This ensures that DFBP forms a homogeneous reaction environment with the hydroquinone salt in the reaction system, resulting in a homogeneous third mixture.

[0032] Furthermore, the third mixture is heated to 270℃~290℃ (specifically, 270℃, 275℃, 280℃, 285℃, 290℃, etc.) at a rate of 1℃ / min~2℃ / min (specifically, 1℃ / min, 1.5℃ / min, 2℃ / min, etc.) and held for 1h~2h (specifically, 1h, 1.5h, 2h, etc.). At this time, sodium hypophosphite in the antioxidant composite system begins to play a role, reducing trace amounts of BQ in the system and preventing BQ from affecting the polymerization reaction. Specifically, sodium hypophosphite has excellent reducing properties and can maintain good reducing ability at high temperatures. It continues to reduce and protect the reaction system in the 270℃~290℃ range. As a reducing agent, sodium hypophosphite can reduce BQ to hydroquinone and is itself oxidized to phosphoric acid or phosphate. The chemical formula can be represented as: C6H4O2 + NaH2PO2 (sodium hypophosphite) + H2O = C6H6O2 + NaH2PO3. Thus, a fourth mixture without BQ was obtained.

[0033] Next, the fourth mixture is heated to 300℃~320℃ (specifically, 300℃, 305℃, 310℃, 315℃, 320℃, etc.) at a rate of 1℃ / min~2℃ / min (specifically, 1℃ / min, 1.5℃ / min, 2℃ / min, etc.). At this point, the polymerization reaction of DFBP and hydroquinone salt begins. The above temperatures ensure high reactivity of both monomers, contributing to stable chain growth. This avoids the potential for slow reaction rates and insufficient molecular weight due to excessively low temperatures, and also prevents chain degradation and side reactions (such as chain breakage and polymer discoloration) due to excessively high temperatures.

[0034] In some embodiments, the molar ratio of 4,4'-difluorobenzophenone to hydroquinone is (1~1.015):1, specifically (1.005~1.01):1. Exemplary ratios include 1:1, 1.015:1, 1.01:1, etc. This ensures sufficient monomers for polymerization, resulting in a polyetheretherketone product with uniform molecular weight distribution and excellent performance.

[0035] In some embodiments, the polymerization reaction time is 1.5 h to 2.5 h. For example, it can be 1.5 h, 2 h, 2.5 h, etc. This ensures that the polymerization reaction proceeds sufficiently, so that the viscosity of the final product reaches the target value, while also ensuring a uniform molecular weight distribution of PEEK. A polymerization reaction time that is too short may lead to incomplete reaction and a low molecular weight product, while a polymerization reaction time that is too long may lead to overpolymerization, resulting in cross-linking, increased product brittleness, and other problems.

[0036] S30: Add the capping agent to the second mixture to carry out the capping reaction and obtain polyether ether ketone.

[0037] In this step, when the viscosity of the second mixture reaches 2000cp~4000cp, a capping agent is added to the system to cap any residual hydroquinone and the phenolic hydroxyl groups at the ends of the polymer chain (PEEK chain).

[0038] In some embodiments, the end-capping agent includes 4,4'-difluorobenzophenone. It reacts with the phenolic hydroxyl groups at the ends of the PEEK chains, blocking the active end groups and preventing degradation and cross-linking caused by the end groups during subsequent thermal processing, thereby improving the thermal stability of PEEK. Simultaneously, DFBP, as one of the monomers in the polymerization reaction, matches the chemical properties of the polymerization system, does not introduce new impurities, and does not undergo side reactions with the already formed PEEK chains.

[0039] Furthermore, the mass ratio between the added capping agent and the initial DFBP raw material (i.e., the DFBP raw material added in S10) is (1~2):100. For example, it can be 1:100, 1.5:100, 2:100, or any range between two of these. A mass ratio between the capping agent and the initial DFBP raw material within the above range can substantially ensure complete closure of the phenolic hydroxyl groups at the PEEK chain ends.

[0040] In some embodiments, the capping reaction time is 0.5 h to 1 h. Specifically, the capping reaction time can be 0.5 h, 0.8 h, 1 h, etc. The above time range ensures that the capping agent reacts fully with the active end groups without causing side reactions due to excessively long reaction time.

[0041] In some embodiments, the end-capping reaction temperature is 340°C to 360°C. Specifically, the end-capping reaction temperature can be 340°C, 345°C, 350°C, 355°C, 360°C, etc. Within the above temperature range, the end-capping agent has higher reactivity with the active groups at the end of the PEEK molecular chain, which can quickly complete the end-group sealing and avoid the residue of unreacted active end groups.

[0042] In some embodiments, a post-processing step is further included after the end-capping reaction. The post-processing step includes precipitation, pulverization, solvent removal, desalting, and drying. For example, after the end-capping reaction, the product is placed on a stainless steel plate for precipitation to obtain crude PEEK. The obtained crude PEEK is then compressed into tablets using a tablet press, and the tablets are pulverized into granules using a pulverizer. The PEEK powder is then washed 4-6 times with 75°C ethanol (ethanol to PEEK mass ratio of 6-8:1), followed by 4-6 times with 90°C deionized water (deionized water to PEEK mass ratio of 8-10:1), and finally vacuum dried at 150°C for 10 hours to obtain the final product.

[0043] In a second aspect of this application, a polyetheretherketone (PEEK) is provided, which is prepared by the aforementioned preparation process. As a result, this PEEK has a long and narrow molecular chain, high thermal stability, good color, and excellent properties.

[0044] In some embodiments, the polyetheretherketone (PEEK) prepared above can be applied in the aerospace field. It can replace conventional aluminum or titanium alloy aircraft components (such as engine impellers and cabin seat frames), achieving weight reduction of aircraft components (by 30% to 50%). Simultaneously, it meets requirements for high temperature resistance (around 260°C), flame retardancy, and radiation resistance.

[0045] In some embodiments, polyetheretherketone (PEEK) can be used in the medical and health fields. It exhibits excellent biocompatibility and can be used as a material for spinal fusion devices, artificial joints, and dental implant abutments.

[0046] The method for preparing PEEK in this application has at least the following beneficial effects: 1. Breaking away from traditional deoxygenation processes, this method further eliminates residual oxygen sources within the system through redox reactions. 2. Through a composite antioxidant system, it achieves antioxidant control across the entire temperature range during the reaction process (primary antioxidant at low temperatures, secondary antioxidant at high temperatures). Specifically, in the low-temperature salt formation stage, sodium metabisulfite acts as a reducing agent, reducing trace amounts of phenolic oxalate (BQ) in the system to hydroquinone, thus minimizing the impact of BQ on subsequent polymerization reactions. In the high-temperature polymerization stage, sodium hypophosphite acts as a reducing agent, further reducing BQ in the system to hydroquinone. Therefore, the phenolic oxalate anion is protected during the reaction process, ensuring stable polymerization and a narrower molecular weight distribution of the product. 3. By reducing, the oxidized color-developing substances (BQ) in the reaction system are eliminated, thus improving the product color; 4. By protecting the phenolic hydroxyl groups, the end-capping effect is maximized, further improving the thermal stability of the product.

[0047] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0048] The embodiments of this application are described in detail below.

[0049] Example 1: 100g of diphenyl sulfone was added to a 500mL four-necked flask (with a protective gas continuously introduced in a volume ratio of N2 to CO2 of 10:1), and heated to 130℃ to fully melt it. 7g of sodium lignosulfonate was added to the molten diphenyl sulfone to obtain a suspension. 0.22g of sodium metabisulfite and 0.11g of sodium hypophosphite were added to the above suspension and mixed evenly to obtain a composite antioxidant system. Hydroquinone (11.01 g, 0.1 mol) and sodium carbonate (11.66 g, 0.11 mol) were added to a three-necked flask, and the temperature was raised to 190 °C and maintained for 1.5 h to obtain the first mixture. After heating the first mixture to 230°C, DFBP (21.82 g, 0.1 mol) was added to a four-necked flask, and the temperature was increased to 280°C at a rate of 1°C / min and held for 1.5 h; then the temperature was increased to 310°C at a rate of 1°C / min and held for 2.5 h to complete the polymerization reaction and obtain the second mixture. Add DFBP (0.327 g, 0.0015 mol) and raise the temperature to 350 °C to carry out the end-capping reaction. Maintain this temperature for 0.5 h to complete the reaction. The end-capped product was poured onto a stainless steel plate to cool and solidify, and then pulverized to obtain crude PEEK powder. The crude PEEK powder was washed five times with 75°C ethanol and then five times with 90°C deionized water. After drying at 150°C, 28.3g of PEEK powder was obtained, with a yield of 98.3%.

[0050] Examples 2-29 Same as Example 1, with specific differences shown in Tables 1 and 2.

[0051] Comparative Example 1 The traditional diphenyl sulfone solvent method for preparing polyether ether ketone involves the following specific steps.

[0052] Add DFBP (21.82 g, 0.1 mol), hydroquinone (11.01 g, 0.1 mol), and 100 g diphenyl sulfone to a 500 mL four-necked flask and stir until homogeneous; Under nitrogen protection, the temperature was raised to 150℃, Na2CO3 (11.66g, 0.11mol) was added, the temperature was raised to 190℃ and the reaction was maintained for 1.5h, then the temperature was raised to 280℃ and the reaction was maintained for 1.5h, then the temperature was raised to 310℃ and maintained for 2.5h to complete the polymerization reaction. Add DFBP (0.327 g, 0.0015 mol) and raise the temperature to 350 °C to carry out the end-capping reaction. Maintain this temperature for 0.5 h to complete the reaction. The end-capped product was poured onto a stainless steel plate to cool and solidify, and then pulverized to obtain crude PEEK powder. The crude PEEK powder was washed five times with 75°C ethanol and then five times with 90°C deionized water. After drying at 150°C, 26.4g of PEEK powder was obtained, with a yield of 91.5%.

[0053] Comparative Examples 2-4 Same as Example 1, the main differences are shown in Tables 1 and 2.

[0054] The performance of polyetheretherketone (PEEK) products was tested using the following methods: (1) Molecular weight distribution test: An Agilent PL-GPC220 high-temperature gel permeation chromatography system was used, with α-chloronaphthalene as solvent and 1,2,4-trichlorobenzene as diluent. The column temperature was 125℃, and the mobile phase was a mixture of α-chloronaphthalene and 1,2,4-trichlorobenzene, with a mass ratio of α-chloronaphthalene to 1,2,4-trichlorobenzene of 1:2.2. The test parameters were K=14.2 and α=0.72. The test results are shown in Table 3 below.

[0055] (2) Colorimetric test: The L value, a value, and b value of the sample were measured using a colorimeter. The L value represents the lightness or darkness; the higher the value, the lighter the product color, and the lower the value, the darker the product color. The a value represents the degree of red-green hue bias; the higher the value, the more reddish the product color, and the lower the value, the more greenish the product color. The b value represents the degree of yellow-blue hue bias; the higher the value, the more yellow the product color, and the lower the value, the more blue the product color. The test results are shown in Table 3 below.

[0056] (3) Thermal stability: Thermogravimetric analysis (TGA) was used to characterize the thermal stability of polyetheretherketone (PEEK) resin. The 5% thermal decomposition temperature determined by TGA was used as the initial thermogravimetric temperature for characterizing the thermal stability of PEEK resin. The specific test conditions were as follows: Atmosphere: 20% oxygen + 80% nitrogen; Heating range: 40℃-800℃; Heating rate: 20℃ / min. The test results are shown in Table 3 below.

[0057]

[0058] Conclusion: As can be seen from Examples 1-29 and Comparative Examples 1-4 above, the preparation method of this application has a high yield, and the prepared polyether ether ketone has excellent product performance (the molecular weight distribution, color and thermal stability of the product are all excellent).

[0059] Specifically, as can be seen from Example 1 and Comparative Example 1, this application introduces a composite antioxidant system. The different activity temperature ranges of the two reducing agents in the composite antioxidant system protect the entire temperature range of the PEEK production process. At the same time, the dispersing effect of sodium lignosulfonate is used to maximize the antioxidant effect by ensuring good dispersibility of the two reducing agents in the organic phase, thus avoiding the negative impact of raw material oxidation and discoloration on the product. In addition, the high-purity raw materials result in a narrow molecular weight distribution in the product, which in turn gives the product better thermal processing performance and makes it less prone to molecular chain breakage that would cause the color to darken. Therefore, the L value of Example 1 is higher than that of Comparative Example 1, and the product color is lighter. The a and b values ​​are lower than those of Comparative Example 1, and the product does not shift towards the red or yellow phase due to oxidative degradation.

[0060] Furthermore, under the same testing conditions, the conventional process (i.e., Comparative Example 1) exhibits a lower thermogravimetric temperature, indicating poorer thermal stability. As shown in Table 3, molecular weight distribution affects the thermal stability of the product. Additionally, the residual active monomer hydroquinone and its oxidation products in the conventional process of Comparative Example 1 also impact thermal stability. In contrast, in Example 1, the narrower molecular weight distribution and higher purity both improved the product's thermal stability. This is because the end-capping process of the conventional process can only inertize and block the terminal phenolic groups of the molecular chain and the residual active monomer hydroquinone, but it is ineffective against quinone structures that have undergone oxidation. The establishment of the antioxidant system not only prevents oxidation but also reduces existing oxidation, resulting in an ideal end-capping effect and improved product performance.

[0061] By comparing Examples 1-3, Examples 26-27 and Comparative Example 2, it can be seen that the amount of sodium lignosulfonate added affects the molecular weight distribution, color and thermal stability of polyether ether ketone.

[0062] By comparing Examples 1, 4-6, 26-27 and Comparative Examples 3-4, it can be seen that the amount of the two reducing agents added affects the molecular weight distribution, color and thermal stability of polyether ether ketone.

[0063] Based on the product performance comparison in Table 3, this invention protects the entire PEEK production process by establishing a composite antioxidant system, thereby enabling the synthesis of polyether ether ketone. This results in a final product with a narrower molecular weight distribution, lighter color, better thermal stability, and higher purity, thus broadening the product's market applications.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0065] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing polyetheretherketone, characterized in that, include: Under a protective atmosphere, hydroquinone and a salt-forming agent undergo a salt-forming reaction in a composite antioxidant system to obtain a first mixture containing hydroquinone salt; The first mixture and 4,4'-difluorobenzophenone were subjected to a polymerization reaction to obtain a second mixture; The capping agent is added to the second mixture to carry out the capping reaction, and polyether ether ketone is obtained; The composite antioxidant system includes diphenyl sulfone, sodium lignosulfonate, sodium metabisulfite, and sodium hypophosphite.

2. The method according to claim 1, characterized in that, The process of causing hydroquinone and the salt-forming agent to undergo a salt-forming reaction in the composite antioxidant system includes: Preparation of a composite antioxidant system; The hydroquinone and the salt-forming agent are added to the composite antioxidant system.

3. The method according to claim 2, characterized in that, The preparation of the composite antioxidant system includes: The diphenyl sulfone is melted to obtain the diphenyl sulfone in a molten state; Sodium lignosulfonate is added to the molten diphenyl sulfone to form a suspension; The sodium metabisulfite and sodium hypophosphite are added to the suspension to obtain the composite antioxidant system.

4. The method according to claim 3, characterized in that, At least one of the following conditions must be met: The melting temperature of the diphenyl sulfone is 120℃~140℃; In the composite antioxidant system, the mass ratio of diphenyl sulfone to sodium lignosulfonate is 100:(5~8); The mass ratio of the sodium metabisulfite, the sodium hypophosphite, and the hydroquinone is (0.8~2):(0.3~1):

100.

5. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The temperature for the salt formation reaction is 180℃~200℃; The salt-forming reaction takes 1 to 2 hours. The salt-forming agent includes at least one of sodium carbonate and potassium carbonate; The molar ratio of the salt-forming agent to the hydroquinone is (1.01~1.5):1, preferably (1.05~1.1):1; The molar ratio of the 4,4'-difluorobenzophenone to the hydroquinone is (1~1.015):1, preferably (1.005~1.01):1; The mass ratio of the capping agent to the 4,4'-difluorobenzophenone is (1~2):

100.

6. The method according to claim 1, characterized in that, The polymerization reaction between the first mixture and 4,4'-difluorobenzophenone includes: After heating the first mixture to 220°C~240°C, the 4,4'-difluorobenzophenone was added to obtain the third mixture; The third mixture is heated to 270°C to 290°C at a rate of 1°C / min to 2°C / min and held for 1 to 2 hours to obtain the fourth mixture; The fourth mixture is heated to 300℃~320℃ at a rate of 1℃ / min~2℃ / min and held for 1.5h~2.5h to obtain the second mixture.

7. The method according to claim 1, characterized in that, At least one of the following conditions must be met: The capping agent includes 4,4'-difluorobenzophenone; The capping reaction time is 0.5 h to 1 h; The end-capping reaction is carried out at a temperature of 340℃~360℃.

8. The method according to claim 1, characterized in that, The protective atmosphere comprises nitrogen and carbon dioxide, and the volume ratio of nitrogen to carbon dioxide is 10:(1~2).

9. The method according to claim 1, characterized in that, After the end-capping reaction is completed, a post-processing step is also included, which includes at least one of precipitation, pulverization, solvent removal, desalting, and drying.

10. A polyetheretherketone, characterized in that, It is prepared by the method described in any one of claims 1 to 9.

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