A melt index controllable polyether ketone ketone and a preparation method and application thereof

Abstract

The application belongs to the technical field of polymer synthesis, and particularly relates to a polyether ketone ketone with controllable melt index, and a preparation method and application thereof. The method comprises the following steps: stirring, uniformly mixing and cooling treatment of anhydrous aluminum chloride, diphenyl ether, a first Lewis base and a first solvent to prepare a diphenyl ether dispersion; stirring and uniformly mixing of isophthaloyl chloride, terephthaloyl chloride, a second Lewis base and a second solvent to prepare an acyl chloride dispersion; adding the acyl chloride dispersion into the diphenyl ether dispersion, heat preservation, and reaction at room temperature; and after the reaction is completed, crushing, washing and drying to obtain the polyether ketone ketone. The application adjusts the adding mode of the Lewis base and the type and dosage of the reaction solvent in the polymerization process, so that the melt index is accurately controlled in a relatively simple way, and the mechanical properties and thermal properties of the polymerization product are also significantly improved, thereby providing a new idea and good control effect for the melt index control of the polyether ketone ketone product.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a polyether ketone with adjustable melt index, its preparation method, and its application. Background Technology

[0002] Polyetherketoneketone (PEKK), a key member of the polyaryletherketone (PAEK) family, possesses an alternating structure of ether and diketone bonds in its molecular chain, which endows the material with excellent thermal stability, high rigidity, and chemical corrosion resistance. It is widely used in aerospace and high-end manufacturing fields. In these applications, melt flow index (MFI) is the core parameter that determines its processing performance and molding process window.

[0003] In current industrial production, the molecular weight and distribution of polyether ketone ketone products are typically controlled by adjusting the ratio of para / meta-acyl chloride monomers, optimizing the catalyst system, or changing polymerization process parameters (such as temperature and time), thereby adjusting the melt index. However, for mature formulations, fine-tuning the monomer ratio or reaction conditions, while altering the melt index, often disrupts the original chemical structure and aggregation equilibrium, leading to uncontrollable fluctuations or even deterioration in the mechanical and thermal properties of the polymer. This severely impacts the consistency and reliability of polyether ketone ketone products in high-end applications.

[0004] Meanwhile, in polymerization reactions, the main role of the solvent is to provide a dispersion medium and transfer heat. In chain polymerization (such as free radical polymerization), the solvent can also adjust the molecular weight and structure of the polymer by influencing the activity of free radicals, chain transfer constants, and initiator decomposition. However, in step-growth polymerization (such as condensation polymerization), since there are no free radicals and initiators, it is more difficult for the solvent to control the molecular weight and regulate the product structure. Furthermore, simply adding or subtracting the amount of solvent can disrupt the equilibrium of the original reaction system, ultimately leading to a decrease in the mechanical and thermal properties of the product. Summary of the Invention

[0005] The purpose of this invention is to provide a polyether ketone ketone with adjustable melt index, its preparation method, and its application, thereby overcoming the shortcomings of the prior art. By adjusting the addition method of Lewis base and the type and amount of reaction solvent during the polymerization process, the melt index can be controlled more precisely. At the same time, the mechanical and thermal properties of the polymerized product are significantly improved, providing a new approach and good control effect for the melt index control of polyether ketone ketone products.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, a method for preparing polyether ketone ketone with adjustable melt index is provided, comprising the following steps: Anhydrous aluminum trichloride, diphenyl ether, a first Lewis base and a first solvent were stirred and mixed, and then cooled to obtain a diphenyl ether dispersion. Isophthaloyl chloride, terephthaloyl chloride, a second Lewis base, and a second solvent were stirred and mixed to obtain an acyl chloride dispersion. The acyl chloride dispersion was added to the diphenyl ether dispersion, kept warm, and then heated to room temperature to carry out the reaction. After the reaction was completed, the polyether ketone was obtained by crushing, washing, and drying. The melt index of polyether ketone ketone can be controlled by adjusting the type and amount of the reaction solvent and the method and amount of Lewis base addition.

[0007] By precisely controlling the total molar amounts of the first and second solvents and the ratio of the total molar amounts of isophthaloyl chloride and terephthaloyl chloride, the mass and heat transfer efficiency of the reaction system was significantly improved. By preparing diphenyl ether dispersion and acyl chloride dispersion stepwise and mixing them at low temperature, the occurrence of side reactions was effectively suppressed, and the controllable growth of polymer molecular weight and molecular structure was achieved. Thus, while simplifying the process, the melt index of the polymer product was controlled and the mechanical and thermal properties of the polymer product were improved.

[0008] Secondly, the same polyetherketoneketone (PEKK) is provided, wherein the PEVKK has a melt index of 20 g / 10 min to 120 g / 10 min. Since the melt index is a core indicator that determines the melt flowability and processing applicability of PEVKK, this control method effectively solves the problem that the processing performance is difficult to match with specific molding requirements in traditional processes, ensuring the excellent quality and performance stability of the final product.

[0009] Thirdly, it provides applications of polyetherketoneketone (PEKK) in injection molding and extruded pipes. The melt index of the obtained PEVKK material can be controlled within a wide range, meeting more processing requirements. For example, materials with a higher melt index have excellent melt flowability, can quickly fill the mold cavity, and are specifically designed for efficient and precise injection molding; while materials with a lower melt index exhibit higher melt strength and heat creep resistance, and can maintain shape stability under high temperature and pressure, meeting the stringent requirements of extruded pipes for high load-bearing capacity.

[0010] Generally speaking, a high melt index of polyetherketoneketone (PEKK) indicates good polymer flowability, making it more suitable for processes such as injection molding that require rapid mold filling; a low melt index of PEVKK indicates poor polymer flowability, generally requiring higher processing temperatures and pressures, and is often used in applications such as extruded pipes where high melt strength is required.

[0011] The beneficial effects of this invention are: This invention provides a simple and efficient method for controlling the properties of polyether ketone ketone. By optimizing the feeding method of Lewis base and the solvent system, the process is simplified while achieving precise control of the polymer melt index. At the same time, it endows the material with excellent mechanical strength and thermal stability, solving the problem that the existing process of controlling the melt index of polyether ketone ketone also affects the key properties such as the mechanical and thermal properties of the polymer product.

[0012] Specifically, on the one hand, by screening solvent types and optimizing their dosage, the reaction kinetics and heat transfer efficiency can be precisely controlled by adjusting the solvent's ability to dissolve and disperse reactants and the solid content of the system. On the other hand, by utilizing the dual function of Lewis bases, which participate in the system construction as a reaction medium and dynamically adjust the concentration of catalyst active centers and steric hindrance through complexation with Lewis acids, the directional distribution of polymer chain growth rate and sequence structure can be achieved.

[0013] (2) The polyether ketone obtained by the present invention has a melt index of 20 g / 10 min to 120 g / 10 min and a number average molecular weight M. n The weight-average molecular weight is 50300-53000. v The polydispersity index (PDI) is 3.2-6.2, the tensile strength is 119-125 MPa, the elongation at break is 8-32%, and the melting temperature is 350-360 ℃.

[0014] (3) The product obtained by the present invention not only achieves precise adjustment of melt index over a wide range, meeting the different requirements of rheological properties for different processing scenarios such as injection molding and extrusion, but also significantly improves the mechanical strength and thermal stability of the polymer product. Attached Figure Description

[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0016] Figure 1 The results are the melt index results obtained by adjusting the amount and type of reaction solvent in different embodiments and comparative examples. Detailed Implementation

[0017] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0018] To address the issue that existing methods for controlling the melt index of polyether ketone ketone (PEKK) can negatively impact the mechanical and thermal properties of the polymerized product, this invention provides a simple method for independently and precisely controlling the melt index of PEKK without altering the core formulation, introducing new chemical modifiers, or disrupting the internal equilibrium of the reaction system. Specifically, by adjusting the addition method of the Lewis base and the type and amount of reaction solvent during polymerization, the reaction process is controlled by utilizing the solubility and amount of solvent. Furthermore, the structure of the polymer chain is controlled by leveraging the Lewis base as a solvent and its influence on the complexation of Lewis acids. This relatively simple method achieves precise control of the melt index while significantly improving the mechanical and thermal properties of the polymerized product, providing a new approach and excellent control effect for the melt index regulation of PEKK products.

[0019] In a first aspect, a method for preparing polyether ketone ketone with adjustable melt index is provided, comprising the following steps: Anhydrous aluminum trichloride, diphenyl ether, a first Lewis base and a first solvent were stirred and mixed, and then cooled to obtain a diphenyl ether dispersion. Isophthaloyl chloride, terephthaloyl chloride, a second Lewis base, and a second solvent were stirred and mixed to obtain an acyl chloride dispersion. The acyl chloride dispersion was added to the diphenyl ether dispersion, kept warm, and then heated to room temperature to carry out the reaction. After the reaction was completed, the polyether ketone was obtained by crushing, washing, and drying. The melt index of polyether ketone ketone can be controlled by adjusting the type and amount of the reaction solvent and the method and amount of Lewis base addition.

[0020] This invention employs a two-component "solvent-Lewis base" control strategy. By optimizing the addition method of the Lewis base and the type and amount of solvent, it achieves deep control over the polymerization kinetics and polymer chain conformation. This method, with a simplified process route, not only achieves precise control of the melt index over a wide range but also simultaneously and significantly improves the mechanical properties and thermal stability of the polymerized product.

[0021] In some other embodiments, the total molar ratio of the first solvent and the second solvent to the total molar ratio of isophthaloyl chloride and terephthaloyl chloride is (18-60):1.

[0022] In some other embodiments, the first solvent and / or the second solvent are each independently selected from one or more of dichloromethane, dichloroethane, o-dichlorobenzene, carbon disulfide, and nitrobenzene. The type of solvent mainly affects the solubility of the polymer chains in the active end groups and complexation system, thereby affecting the degree of molecular chain stacking and entanglement in the final polymer product.

[0023] In some other embodiments, the first Lewis base and / or the second Lewis base are each independently selected from one or more of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N,N-dimethylpyrrolidone, and triphenylphosphine oxide. The different types of Lewis bases primarily affect the strength of their interaction with Lewis acids, thereby influencing the reaction rate, the uniformity of the polymer chain, and ultimately the melt index. The Lewis base is used as a solvent and its complexation with Lewis acids to regulate the structure of the polymer chain.

[0024] In some other embodiments, the molar ratio of the first solvent to the second solvent is (2-7):1. Utilizing a high proportion of solvent as a highly efficient thermal buffer medium effectively absorbs and disperses the large amount of heat released by the condensation reaction, significantly reducing the system viscosity to prevent localized overheating or explosive polymerization. Simultaneously, the effective concentration of the monomer allows for precise control of the molecular chain growth rate and reaction termination.

[0025] In some other embodiments, the total molar ratio of the first Lewis base and the second Lewis base to the total molar ratio of isophthaloyl chloride and terephthaloyl chloride is (3.5-6.5):1. Within this range, after a portion of the Lewis base and Lewis acid form a complex system, the other Lewis bases are miscible with the solvent. This can increase the dispersibility of the polymer chain in the solvent during the growth process, reduce chain termination and side reactions, and make the preparation process thermodynamically and kinetically stable and controllable. This is the key to simultaneously achieving narrow distribution adjustment of the melt index of polyether ketone ketone, linear growth of high molecular weight, and excellent mechanical and thermal properties.

[0026] The molar ratio of terephthaloyl chloride to isophthaloyl chloride is (3.9-4.1):1; In some other embodiments, the molar ratio of the first Lewis base to the second Lewis base is (3.5-10.5):1.

[0027] In some other embodiments, the molar ratio of anhydrous aluminum trichloride to diphenyl ether is (5.1-5.3):1; The total molar ratio of terephthaloyl chloride and isophthaloyl chloride to the molar ratio of diphenyl ether is (1.05-1.15):1.

[0028] In some other embodiments, the cooling treatment temperature is -35℃ to -10℃, and the heat preservation time is 0.5 to 2 hours; this effectively suppresses the intense exothermic reaction in the early stage and avoids monomer decomposition caused by local overheating.

[0029] The reaction time is 10–30 h, which ensures that the condensation reaction proceeds fully to achieve efficient synthesis of high molecular weight polymers, while preventing molecular chain cross-linking or degradation that may be caused by excessive reaction.

[0030] Secondly, a method for controlling the melt index of polyether ketone ketone (PKK) is provided to obtain PKK with a melt index of 20 g / 10 min to 120 g / 10 min. This method enables control of the melt index of crude PKKK with similar molecular weights over a wide range (20-120 g / 10 min; MFR@380℃, 5 kg). While changing the melt index, the mechanical properties (tensile strength and elongation at break) and thermal properties (melting temperature) of the product remain at a good level with minimal fluctuation.

[0031] Thirdly, it provides information on the application of polyetherketoneketone (PEKK) in injection molding and extruded pipes. Generally, a high melt index indicates good polymer flowability, making it more suitable for processes such as injection molding that require rapid mold filling; a low melt index indicates poor polymer flowability, generally requiring higher processing temperatures and pressures, and is often used in applications such as extruded pipes where high melt strength is required.

[0032] Example 1 Reaction system assembly: Install a thermometer, stirrer, and gas delivery tube on the four-necked flask. Place the apparatus in a cryogenic constant temperature bath and set the temperature to -20°C. Connect the nitrogen flow meter to the nitrogen pipeline, turn on the nitrogen gas, and continuously introduce nitrogen through the gas delivery tube to keep the reaction system dry. Turn on the stirrer.

[0033] A polyether ketone with adjustable melt index and its preparation method, comprising the following steps: The order of adding raw materials is shown in Table 1. Weigh 995.2 g (7.46 mol) Lewis acid anhydrous aluminum trichloride, 244.2 g (1.43 mol) diphenyl ether, 4002.6 g (40.45 mol) dichloroethane (part 1), and 334.8 g (4.58 mol) Lewis base N,N-dimethylformamide (part 1) and add them sequentially to a four-necked flask (-20℃). Weigh 251.7 g (1.24 mol) terephthaloyl chloride, 62.9 g (0.31 mol) isophthaloyl chloride, 73.1 g (1.00 mol) Lewis base N,N-dimethylformamide (part 2), and 1000.0 g (10.11 mol) dichloroethane (part 2) to prepare an acyl chloride solution. Add the acyl chloride solution dropwise to the flask and keep it warm for 1 hour. Then heat the system to 25℃ and stop stirring after reacting for 20 hours. After the reaction was completed, 1000 mL of 5% dilute hydrochloric acid was added to decomplex the product. After rinsing with pure water until the pH of the aqueous solution was greater than 5, the product was dried, ground, pulverized, and sieved. After washing with deionized water, methanol, and 5% hydrochloric acid, respectively, crude PEKK product was obtained.

[0034] Example 2 The order of raw material addition is shown in Table 1. Unlike Example 1, the amount of dichloroethane added in the first addition was 1911.9 g (19.32 mol), and the amount of dichloroethane added in the second addition was 910.4 g (9.20 mol); the amount of Lewis base dimethyl sulfoxide added in the first addition was 446.9 g (5.72 mol), and the amount of Lewis base dimethyl sulfoxide added in the second addition was 85.8 g (1.10 mol); the reaction cooling temperature was -30°C, the holding time was 0.5 hours, and the reaction time was 25 hours; other steps remained unchanged.

[0035] Example 3 The order of raw material addition is shown in Table 1. Unlike Example 1, the amount of dichloroethane added in the first addition was 3543.8 g (35.81 mol), and the amount of dichloroethane added in the second addition was 520.5 g (5.26 mol); the amount of Lewis base N-methylpyrrolidone added in the first addition was 837.7 g (8.45 mol), and the amount of Lewis base N-methylpyrrolidone added in the second addition was 115.0 g (1.16 mol); the reaction cooling temperature was -12℃, the holding time was 1.5 hours, and the reaction time was 12 hours; other steps remained unchanged.

[0036] Example 4 The order of raw material addition is shown in Table 1. Unlike Example 1, the amount of dichloroethane added in the first addition was 7015.0 g (70.89 mol), and the amount of dichloroethane added in the second addition was 1420.8 g (14.36 mol); the amount of Lewis base dimethylacetamide added in the first addition was 676.1 g (7.76 mol), and the amount of Lewis base dimethylacetamide added in the second addition was 67.1 g (0.77 mol); the reaction cooling temperature was -23°C, the holding time was 2 hours, and the reaction time was 16 hours; other steps remained unchanged.

[0037] Example 5 The order of raw material addition is shown in Table 1. Unlike Example 1, the amount of dichloromethane added in the first addition was 4537.8 g (53.43 mol), and the amount of dichloroethane added in the second addition was 1783.2 g (18.02 mol); the amount of Lewis base triphenylphosphine oxide added in the first addition was 1425.4 g (5.12 mol), and the amount of Lewis base triphenylphosphine oxide added in the second addition was 160.0 g (0.57 mol); the reaction cooling temperature was -26℃, the holding time was 0.8 hours, and the reaction time was 12 hours; other steps remained unchanged.

[0038] Example 6 The order of raw material addition is shown in Table 1. Unlike Example 1, the amount of o-dichlorobenzene solvent added in the first addition was 2669.5 g (18.16 mol), carbon disulfide was 706.6 g (9.28 mol), and the amount of nitrobenzene solvent added in the second addition was 582.3 g (4.73 mol). The amount of Lewis base dimethyl sulfoxide added in the first addition was 540.7 g (6.92 mol), and the amount of Lewis base dimethyl sulfoxide added in the second addition was 89.1 g (1.14 mol). The reaction cooling temperature was -19°C, the holding time was 1.2 hours, and the reaction time was 19 hours. Other steps remained unchanged.

[0039] Comparative Example 1 The order of raw material addition is shown in Table 1. Unlike Example 1, 407.9 g (5.58 mol) Lewis base N,N-dimethylformamide was added to the reaction apparatus only along with the first portion of dichloroethane solvent; the other steps remained unchanged.

[0040] Comparative Example 2 The order of raw material addition is shown in Table 1. Unlike Example 1, 407.9 g (5.58 mol) Lewis base N,N-dimethylformamide was added to the reaction apparatus only along with the second part of dichloroethane solvent; the other steps remained unchanged.

[0041] Comparative Example 3 The order of adding raw materials is shown in Table 1. Unlike Example 1, anhydrous aluminum trichloride was added in two parts: 895.7g (6.72mol) of anhydrous aluminum trichloride was added with the addition of the first part of dichloroethane solvent and the first part of Lewis base, and 99.5g (0.75mol) of anhydrous aluminum trichloride was added with the addition of the second part of dichloroethane solvent and the second part of Lewis base; other steps remained unchanged.

[0042] Table 1 Feeding sequence

[0043] Performance testing 1. Polydispersity index test: The number-average molecular weight (Mn) of the obtained crude PEKK was determined by gel permeation chromatography (GPC). n ) and weight-average molecular weight (M v ), and calculate the corresponding polydispersity coefficient (PDI).

[0044] 2. Melt Flow Index Test: The obtained crude PEKK product was tested for melt flow index (MFR@380℃, 5kg) using a melt flow indexer. The test standard was based on ISO 1133, and the specific test conditions were a temperature of 380℃ and a load of 5kg.

[0045] 3. Tensile strength and elongation at break test: The obtained PEKK crude product was tested for tensile strength and elongation at break using a universal tensile testing machine, according to ASTM D638.

[0046] 4. Melting temperature test: The melting temperature of the obtained crude PEKK was tested using a differential scanning calorimeter (DSC) at a heating rate of 20℃ / min, with two heating cycles performed.

[0047] The properties of different crude polyether ketones are shown in Table 2 and Figure 1 As shown in the (melt index).

[0048] Table 2 Properties of different crude polyetherketone ketones

[0049] The results in Table 2 show that by controlling the amount and ratio of solvent during the reaction, the aggregation state and interaction of polymer chains can be altered, thus achieving a wide range of variations in the melt index of crude polyether ketone ketone products with similar molecular weights (e.g., Figure 1 As shown, by adjusting the melt index (20-120g / 10min; MFR@380℃, 5kg), the mechanical properties (tensile strength and elongation at break) and thermal properties (melting temperature) of the product are at a good level and the fluctuation is small. Thus, the melt index of polyether ketone ketone products can be easily and effectively adjusted in mature formulations.

[0050] This is because, in the intrinsic structure of materials that affect the melt index of polyether ketone, molecular weight and its distribution, and the degree of branching of the molecular chains are two important factors. In the regulation of polymerization, it is necessary to control these influencing factors while maintaining the good properties of the polymer. Therefore, the polymerization process is comprehensively regulated by adjusting the amount and type of solvent and Lewis base.

[0051] As the polymerization principle shows, in the preparation of polyether ketone ketones using the Lewis acid-Lewis base co-catalysis method, the polymerization system, through the combined action of the Lewis base and Lewis acid, causes the polymer to form a complex system with aluminum trichloride in solution, thus initiating chain growth. The concentration of active end groups in the complex system affects the rate and length of polymer chain growth. Therefore, by adjusting the ratio of Mol (total reaction solvent): Mol (reacting acyl chloride), the concentration of active end groups during the reaction can be controlled. Thus, under similar degrees of polymerization, the final melt index (e.g., [missing information]) can be influenced by adjusting the polydispersity index of the polymer chain. Figure 1 (As shown).

[0052] Specifically, as shown in Examples 4 and 5, a large ratio of Mol (total reaction solvent) to Mol (reacting acyl chloride) indicates a large amount of solvent. Consequently, the concentration of active end groups in the complexation system is low, the growth of polymer chains is relatively dispersed, and the proportion of linear structures and short branches in the polymer is high. Therefore, the polydispersity index of the product is large, and the corresponding melt index value is also high.

[0053] The ratio of Lewis base to acyl chloride directly determines the activity and selectivity of the catalytic system. In Example 6, after some Lewis bases and Lewis acids form a complex system, the other Lewis bases are miscible with the solvent, which can increase the dispersibility of the polymer chain in the solvent during the growth process, reduce chain termination and side reactions, and thus prepare polyether ketone ketone samples with high molecular weight and uniform distribution. Therefore, the main properties of the polymer material will not be affected during the process of controlling the melt index.

[0054] In addition, a key factor in regulation is the two additions of the Lewis base, as shown in Comparative Examples 1 and 2. If the Lewis base is added only once, the polymerization process maintains its reactivity, but the fluctuation of the acyl chloride concentration leads to polymer chain aggregation or uncontrolled reaction, resulting in a decrease in the molecular weight of the product. This leads to a decrease in mechanical properties (tensile strength and elongation at break) and thermal properties (melting temperature), and it is not possible to change the melt index without reducing the product's performance.

[0055] It is worth noting that during the second addition of the Lewis base, it acts as a solvent to ensure an appropriate concentration of acyl chloride. Furthermore, its combination with the Lewis acid allows the polymer to form a stable complex system with aluminum trichloride in solution, ensuring that the polymerization performance does not fluctuate significantly due to changes in solvent concentration. Ultimately, this achieves control of the melt index during the stable polymerization process. Additionally, as shown in Comparative Example 3, the two separate additions of the Lewis acid and anhydrous aluminum trichloride did not significantly improve the final properties of the product; instead, they reduced the tensile strength and melting temperature of the polymer. This is because the single addition of anhydrous aluminum trichloride allows for more uniform dispersion in the system, and the low-temperature maintenance controls the reactivity, ultimately leading to a more suitable complex system for uniform polymer chain growth after the second addition of the Lewis base.

[0056] Examples 2, 3, and 6 also demonstrate that the type of solvent and Lewis base added affects the final melt index, which is key to the wide controllability of the melt index. The type of solvent primarily affects the solubility of the active end groups and polymer chains in the complexation system, thus influencing the degree of molecular chain stacking and entanglement in the final polymer product. Different types of Lewis bases mainly affect the strength of the interaction with Lewis acids, thereby affecting the reaction rate and the uniformity of the polymer chains, ultimately impacting the melt index.

[0057] The reaction solvents used in Examples 2 and 6 are different. Compared to dichloroethane, o-dichlorobenzene contains a benzene ring and has lower polarity, resulting in a tighter polymer chain bond in the complexation system. Consequently, when the molecular weight and molecular weight distribution are similar, the melt index of the polymer product using o-dichlorobenzene solvent is lower. The Lewis bases used in Examples 2 and 3 are different. The Lewis basicity of dimethyl sulfoxide mainly comes from the lone pair electrons on the sulfur atom, which can act as a σ-donor to coordinate with the metal center. The Lewis basicity of N-methylpyrrolidone mainly comes from the lone pair electrons on the carbonyl oxygen atom. The Lewis basicity of dimethyl sulfoxide is slightly stronger than that of N-methylpyrrolidone, and the solvent's greater solubility leads to a greater degree of molecular chain dispersion. Therefore, the molecular chain entanglement of the product catalyzed by using dimethyl sulfoxide as a Lewis base is slightly weaker, resulting in a larger melt index of the prepared product.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing polyetherketone ketone with adjustable melt index, characterized in that, Includes the following steps: Anhydrous aluminum trichloride, diphenyl ether, a first Lewis base and a first solvent were stirred and mixed, and then cooled to obtain a diphenyl ether dispersion. Isophthaloyl chloride, terephthaloyl chloride, a second Lewis base, and a second solvent were stirred and mixed to obtain an acyl chloride dispersion. The acyl chloride dispersion was added to the diphenyl ether dispersion, kept warm, and then heated to room temperature to carry out the reaction. After the reaction was completed, the polyether ketone was obtained by crushing, washing, and drying. The melt index of polyether ketone ketone can be controlled by adjusting the type and amount of the reaction solvent and the method and amount of Lewis base addition.

2. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The first solvent and / or the second solvent are each independently selected from one or more of dichloromethane, dichloroethane, o-dichlorobenzene, carbon disulfide and nitrobenzene.

3. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The first Lewis base and / or the second Lewis base are each independently selected from one or more of N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N,N-dimethylpyrrolidone, and triphenylphosphine oxide.

4. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The ratio of the total molar ratio of the first solvent and the second solvent to the total molar ratio of isophthaloyl chloride and terephthaloyl chloride is (18-60):1; The molar ratio of the first solvent to the second solvent is (2-7):

1.

5. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The ratio of the total molar ratio of the first Lewis base and the second Lewis base to the total molar ratio of the isophthaloyl chloride and terephthaloyl chloride is (3.5-6.5):1; The molar ratio of terephthaloyl chloride and isophthaloyl chloride is (3.9-4.1):

1.

6. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The molar ratio of the first Lewis base to the second Lewis base is (3.5-10.5):

1.

7. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The molar ratio of anhydrous aluminum trichloride to diphenyl ether is (5.1-5.3):1; The total molar ratio of terephthaloyl chloride and isophthaloyl chloride to the molar ratio of diphenyl ether is (1.05-1.15):

1.

8. The method for preparing polyetherketone ketone with adjustable melt index as described in claim 1, characterized in that, The cooling treatment temperature is -35℃ to -10℃, the heat preservation time is 0.5 to 2 hours, and the reaction time is 10 to 30 hours.

9. A polyetherketone ketone prepared by the method for preparing polyetherketone ketone with adjustable melt index as described in any one of claims 1-8, characterized in that, The melt index of the polyether ketone is 20 g / 10 min to 120 g / 10 min.

10. The use of the polyether ketone ketone according to claim 9 in injection molding and extrusion of pipes.

Images