A polyether ketone ketone with adjustable molecular weight distribution and a preparation method thereof

Abstract

The application discloses a polyether ketone ketone with adjustable molecular weight distribution and a preparation method thereof. The polyether ketone ketone with adjustable molecular weight distribution comprises the following components in mass fraction: 4,4'-difluorobenzophenone 45-55 parts; isophthaloyl chloride 30-38 parts; end group active capping regulator 2.5-6.5 parts; gradient alkaline salt-forming catalyst 4-8 parts; aromatic ring steric copolymerization modifier 3-7 parts; polar aprotic solvent 120-180 parts; anhydrous lithium chloride 1-3 parts. The end group active capping regulator can accurately terminate the molecular chain growth by adding an amount, so as to realize the narrow molecular weight distribution regulation and control. The gradient alkaline salt-forming catalyst can realize uniform and slow release of the catalyst in the whole polymerization process, and avoid the disorder of the molecular chain growth rate. The aromatic ring steric copolymerization modifier can regulate the molecular chain stacking freedom and widen the distribution regulation interval. The three components can stably realize the continuous and accurate adjustment of the PDI of the PEKK in the range of 1.15-1.80.

Description

Technical Field

[0001] This invention belongs to the field of high-performance special engineering plastics synthesis technology, specifically a polyether ketone ketone with adjustable molecular weight distribution and its preparation method. Background Technology

[0002] Polyetherketoneketone (PEKK) is a semi-crystalline high-performance thermoplastic resin with alternating ether and ketone bonds in its main chain. It possesses excellent heat resistance, mechanical strength, fatigue resistance, chemical corrosion resistance, and biocompatibility, and is widely used in key fields such as aerospace structural components, precision electronic components, medical implants, and high-end new energy equipment.

[0003] In existing technologies, polyetherketoneketone (PEKK) is generally prepared using a traditional one-step high-temperature polycondensation process. The polymerization rate is uncontrollable, the molecular chains grow randomly, and the final product has a fixed and relatively wide molecular weight distribution, generally exhibiting a PDI greater than 1.9. Different molding processes have vastly different requirements for the molecular weight distribution of PEKK: narrow-distribution PEKK has a PDI range of 1.15–1.39, resulting in uniform melt flow and high molding precision, making it suitable for precision 3D printing and injection molding of micro-components; medium-wide-distribution PEKK has a PDI range of 1.40–1.80, balancing flowability and mechanical strength, making it suitable for conventional injection molding, thick-wall extrusion, and film molding.

[0004] Currently, there is no mature technology in the industry that can achieve continuously adjustable molecular weight distribution of PEKK within the same formulation system. Traditional modification methods can only improve mechanical or heat resistance properties in a single way. Some molecular weight control technologies rely on single additives, resulting in a narrow control range, low precision, and easy degradation of the resin's bulk properties. At the same time, traditional one-time feeding polymerization processes have defects such as rapid boiling in the early stage of the reaction, catalytic deactivation in the later stage, and large differences in molecular chain length, leading to poor batch stability and weak processing adaptability, which seriously limits the multi-scenario industrial application of PEKK.

[0005] Therefore, a polyether ketone with adjustable molecular weight distribution and its preparation method were designed. Summary of the Invention

[0006] In view of the above situation and to overcome the defects of the prior art, the present invention provides a polyether ketone with adjustable molecular weight distribution and a method for preparing the same, which effectively solves the problems mentioned in the background.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a polyether ketone ketone with adjustable molecular weight distribution, comprising the following components in parts by mass: 4,4'-Difluorobenzophenone 45-55 parts; 30-38 parts of isophthaloyl chloride; 2.5–6.5 parts of end-capping regulator with active end groups; Gradient alkaline salt-forming catalyst, 4-8 parts; 3-7 parts of sterically hindered aromatic copolymer modifier; 120–180 parts of polar aprotic solvent; 1-3 parts of anhydrous lithium chloride.

[0008] Preferably, the polar aprotic solvent is any one of N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

[0009] Preferably, the preparation method of the end-group active capping regulator includes the following steps: S1.1 Raw material ratio: Weigh 4-hydroxybenzaldehyde and cyclobutenone in a molar ratio of 1:1.2 to 1.5 and set aside; S1.2 Dissolution and dispersion: Dissolve 4-hydroxybenzaldehyde in anhydrous ethanol to prepare a solution with a mass concentration of 15% to 20%, and stir at room temperature at 250 to 350 r / min for 10 to 15 min until completely dissolved; S1.3 Addition condensation: Slowly add cyclobutenone dropwise over 30-40 minutes. After the addition is complete, raise the temperature to 55-65°C and reflux at 350-450 r / min for 4-6 hours. S1.4 Purification and Drying: After the reaction is completed, remove ethanol by vacuum distillation, cool to crystallize, wash with ice water 2-3 times, filter, and dry under vacuum at 80-90℃ for 6-8 hours to obtain high-purity hydroxyphenylcyclobutenone end-capping regulator.

[0010] Preferably, the preparation method of the gradient alkaline salt-forming catalyst includes the following steps: S2.1, Core preparation: Weigh anhydrous sodium carbonate and anhydrous potassium carbonate at a mass ratio of 2:1 to 1.5, mix them, ball mill at 300 to 400 r / min for 2 to 3 h, and pass them through a 200 to 300 mesh sieve to obtain alkaline core particles with a particle size of 5 to 10 μm. S2.2, Shell coating: Disperse the core particles in anhydrous ethanol to prepare a dispersion with a solid content of 8% to 12%, add 15% to 20% by weight of the core particles and 20 to 50 nm of nano-silica sol, and stir at room temperature at 400 to 500 r / min for 20 to 30 min. S2.3 Gradient activation: Heat to 70-80℃ and stir for 1.5-2.5h. After drying the solvent, calcine in a muffle furnace at 350-400℃ for 2-3h. Cool, pulverize, and pass through a 300-mesh sieve to obtain a core-shell structured gradient alkaline salt-forming catalyst.

[0011] Preferably, the preparation method of the sterically hindered aromatic copolymer modifier includes the following steps: S3.1, Friedel-Crafts acylation reaction: using 2-methylfluorobenzene and p-fluorobenzoyl chloride as raw materials, with a molar ratio of 1:1.05 to 1.1, anhydrous aluminum trichloride as catalyst, and dichloromethane as solvent, the reaction is carried out at room temperature with stirring at 300 to 400 r / min for 2.5 to 3.5 h. S3.2 Hydrolysis and purification: Quench the reaction with dilute hydrochloric acid, allow to stand and separate into layers, take the organic phase, wash with deionized water and saturated brine until neutral, remove the solvent by vacuum distillation to obtain the crude monomer product; S3.3 Recrystallization purification: The crude product is recrystallized with anhydrous ethanol, filtered, and then vacuum dried at 90-100℃ for 5-7 hours to obtain a high-purity sterically hindered comonomer of 2-methyl-4,4'-difluorobenzophenone.

[0012] A method for preparing a polyether ketone ketone with tunable molecular weight distribution, comprising the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, and purge the air with high-purity nitrogen 3 to 5 times to control the oxygen content in the reactor to ≤100ppm and the moisture content to ≤50ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the formulated amount of polar aprotic solvent and anhydrous lithium chloride to the reaction vessel, stir at 200-300 r / min for 15-25 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 15-25℃, and the mixture is stirred at a constant temperature of 300-400r / min for 30-40min to make the monomers uniformly dispersed. S4. Segmented gradient heating polymerization: Three-stage gradient heating polymerization is adopted, with a uniform heating rate of 3-5℃ / min; In the first stage, the temperature is raised to 80-90℃, half the mass of gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 400-500 r / min for 1.5-2.5 h. In the second stage, the temperature is raised to 120-130℃, the remaining gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 500-600 r / min for 2-3 hours. In the third stage, the temperature is raised to 160-170℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 600-700 r / min for 3.5-4.5 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 160-170℃ and add the end-group active capping agent dropwise at a uniform rate for 20-40 minutes. After the addition is completed, let it mature at a constant temperature for 1-2 hours. When the target PDI is 1.15-1.39, use a high dose of capping agent; when the target PDI is 1.40-1.80, use a low dose of capping agent. S6. Post-treatment purification: After the reaction is completed, allow the temperature to cool naturally to 60-80℃. Slowly pour the reaction solution into deionized water at 25-35℃ to precipitate the polymer. The stirring speed during precipitation is 150-250 r / min, and the precipitation time is 40-60 min. Filter and collect the solid. Wash with boiling ethanol 3-5 times and deionized water 2-3 times, each wash lasting 15-20 min. Finally, place it under vacuum drying at 120-140℃ and a vacuum degree ≤-0.09 MPa for 8-12 h to obtain a polyether ketone ketone product with adjustable molecular weight distribution.

[0013] Preferably, the heating rate of the three polymerization stages in step S4 is controlled at 3-5℃ / min.

[0014] Preferably, in step S6, the precipitation water temperature is 25-35℃, the precipitation stirring speed is 150-250 r / min, and the precipitation time is 40-60 min.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes three components—an end-group active capping regulator, a gradient alkaline salt-forming catalyst, and an aromatic ring steric hindrance copolymerizing modifier—to form a synergistic regulatory system, overcoming the shortcomings of traditional PEKK single modification which lacks regulatory capability. Specifically, the end-group active capping regulator can precisely terminate molecular chain growth through dosage, achieving narrow control of molecular weight distribution; the gradient alkaline salt-forming catalyst enables uniform and slow-release catalysis throughout the polymerization process, avoiding disordered molecular chain growth rates; and the aromatic ring steric hindrance copolymerizing modifier can regulate the degree of freedom in molecular chain stacking, broadening the distribution control range. The combination of these three components allows for stable and continuous precise adjustment of the PDI of PEKK within a wide range of 1.15–1.80. 2. This invention significantly improves batch stability of products through gradient catalysis and segmented polymerization processes. By utilizing the slow-release catalytic characteristics of the core-shell structured gradient alkaline salt-forming catalyst, combined with the step-by-step gradient temperature increase and batch-by-batch catalyst addition process of this invention, it effectively solves the defects of traditional one-time feeding and high-temperature polymerization, such as initial reaction boiling, rapid catalytic deactivation in the later stage, and uneven molecular chain lengths. The catalyst core layer continuously provides energy, and the shell layer slowly releases and controls the rate. Matching the temperature gradient design of segmented polymerization, the molecular chains grow at a uniform speed, in an orderly and controllable manner, greatly reducing the molecular weight deviation of batch products and significantly improving the batch consistency and production controllability of PEKK products. 3. This invention uses aromatic ring steric hindrance type copolymer modification monomers for copolymerization modification. The steric hindrance effect of the methyl side of the monomer can moderately optimize the resin molecular chain arrangement and crystal regularity, avoiding the problems of resin crystallization defects and decreased mechanical and heat resistance caused by traditional small molecule additives and single end-capping regulation. While achieving a wide range of adjustable molecular weight distribution, it effectively retains the excellent mechanical strength and heat resistance of PEKK body. The finished product has high tensile strength and high heat distortion temperature, fully retaining the performance advantages of high-end PEKK materials, and solving the industry pain point of being unable to balance regulation and performance. Detailed Implementation

[0016] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] This invention provides a polyether ketone with an adjustable molecular weight distribution, comprising the following components in parts by mass: 4,4'-Difluorobenzophenone 45-55 parts; 30-38 parts of isophthaloyl chloride; 2.5–6.5 parts of end-capping regulator with active end groups; Gradient alkaline salt-forming catalyst, 4-8 parts; 3-7 parts of sterically hindered aromatic copolymer modifier; 120–180 parts of polar aprotic solvent; 1-3 parts of anhydrous lithium chloride.

[0018] In this embodiment, the polar aprotic solvent is any one of N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

[0019] The preparation method of the end-group active capping regulator in this embodiment includes the following steps: S1.1 Raw material ratio: Weigh 4-hydroxybenzaldehyde and cyclobutenone in a molar ratio of 1:1.2 to 1.5 and set aside. S1.2 Dissolution and dispersion: Dissolve 4-hydroxybenzaldehyde in anhydrous ethanol to prepare a solution with a mass concentration of 15% to 20%, and stir at room temperature at 250 to 350 r / min for 10 to 15 min until completely dissolved; S1.3, Addition condensation: Slowly add cyclobutenone dropwise over 30-40 min. After the addition is complete, raise the temperature to 55-65℃ and reflux at 350-450 r / min for 4-6 h. S1.4 Purification and Drying: After the reaction is completed, remove ethanol by vacuum distillation, cool to crystallize, wash with ice water 2-3 times, filter, and dry under vacuum at 80-90℃ for 6-8 hours to obtain high-purity hydroxyphenylcyclobutenone end-capping regulator.

[0020] The preparation method of the gradient alkaline salt-forming catalyst in this embodiment includes the following steps: S2.1, Core preparation: Weigh anhydrous sodium carbonate and anhydrous potassium carbonate at a mass ratio of 2:1 to 1.5, mix them, ball mill at 300 to 400 r / min for 2 to 3 h, and pass them through a 200 to 300 mesh sieve to obtain alkaline core particles with a particle size of 5 to 10 μm. S2.2, Shell coating: Disperse the core particles in anhydrous ethanol to prepare a dispersion with a solid content of 8% to 12%, add 15% to 20% by weight of the core particles and 20 to 50 nm of nano-silica sol, and stir at room temperature at 400 to 500 r / min for 20 to 30 min. S2.3 Gradient activation: Heat to 70-80℃ and stir for 1.5-2.5h. After drying the solvent, calcine in a muffle furnace at 350-400℃ for 2-3h. Cool, pulverize, and pass through a 300-mesh sieve to obtain a core-shell structured gradient alkaline salt-forming catalyst.

[0021] The method for preparing the sterically hindered aromatic copolymer modified monomer of this embodiment includes the following steps: S3.1, Friedel-Crafts acylation reaction: using 2-methylfluorobenzene and p-fluorobenzoyl chloride as raw materials, with a molar ratio of 1:1.05 to 1.1, anhydrous aluminum trichloride as catalyst, and dichloromethane as solvent, the reaction is carried out at room temperature with stirring at 300 to 400 r / min for 2.5 to 3.5 h. S3.2 Hydrolysis and purification: Quench the reaction with dilute hydrochloric acid, allow to stand and separate into layers, take the organic phase, wash with deionized water and saturated brine until neutral, remove the solvent by vacuum distillation to obtain the crude monomer product; S3.3 Recrystallization purification: The crude product is recrystallized with anhydrous ethanol, filtered, and then vacuum dried at 90-100℃ for 5-7 hours to obtain a high-purity sterically hindered comonomer of 2-methyl-4,4'-difluorobenzophenone.

[0022] A method for preparing polyetherketone ketone with adjustable molecular weight distribution includes the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, and purge the air with high-purity nitrogen 3 to 5 times to control the oxygen content in the reactor to ≤100ppm and the moisture content to ≤50ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the formulated amount of polar aprotic solvent and anhydrous lithium chloride to the reaction vessel, stir at 200-300 r / min for 15-25 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 15-25℃, and the mixture is stirred at a constant temperature of 300-400r / min for 30-40min to make the monomers uniformly dispersed. S4. Segmented gradient heating polymerization: Three-stage gradient heating polymerization is adopted, with a uniform heating rate of 3-5℃ / min; In the first stage, the temperature is raised to 80-90℃, half the mass of gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 400-500 r / min for 1.5-2.5 h. In the second stage, the temperature is raised to 120-130℃, the remaining gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 500-600 r / min for 2-3 h. In the third stage, the temperature is raised to 160-170℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 600-700 r / min for 3.5-4.5 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 160-170℃ and add the end-group active capping agent dropwise at a uniform rate for 20-40 minutes. After the addition is completed, let it mature at a constant temperature for 1-2 hours. When the target PDI is 1.15-1.39, use a high dose of capping agent; when the target PDI is 1.40-1.80, use a low dose of capping agent. S6. Post-processing purification: After the reaction is completed, allow the temperature to cool naturally to 60-80℃. Slowly pour the reaction solution into deionized water at 25-35℃ to precipitate the polymer. The stirring speed during precipitation is 150-250 r / min, and the precipitation time is 40-60 min. Filter and collect the solid. Wash with boiling ethanol 3-5 times and deionized water 2-3 times, each wash lasting 15-20 min. Finally, place it under vacuum drying at 120-140℃ and a vacuum degree ≤-0.09 MPa for 8-12 h to obtain a polyether ketone ketone product with adjustable molecular weight distribution.

[0023] In step S4 of this embodiment, the heating rate of the three-stage polymerization is controlled at 3-5℃ / min.

[0024] In step S6 of this embodiment, the precipitation water temperature is 25-35℃, the precipitation stirring speed is 150-250 r / min, and the precipitation time is 40-60 min.

[0025] Example 1 (Narrow Distribution Regulation) A polyether ketone with an adjustable molecular weight distribution comprises the following components in parts by mass: 50 parts of 4,4'-difluorobenzophenone; 35 parts of isophthaloyl chloride; 6 parts of end-capping regulator with active end group; Gradient alkaline salt-forming catalyst, 6 parts; Five parts of sterically hindered aromatic copolymer modifier; 150 parts of a polar aprotic solvent (N-methylpyrrolidone); Two parts of anhydrous lithium chloride.

[0026] Preparation of end-group active end-capping regulator: 4-hydroxybenzaldehyde and cyclobutenone were weighed at a molar ratio of 1:1.3; 4-hydroxybenzaldehyde was prepared into an 18% (w / w) anhydrous ethanol solution and stirred at 300 r / min for 12 min at room temperature until completely dissolved; cyclobutenone was added dropwise at a uniform rate for 35 min, and the mixture was heated to 60℃ and refluxed at 400 r / min for 5 h; the solution was removed under reduced pressure, crystallized at room temperature, washed twice with ice water, and dried under vacuum at 85℃ for 7 h to obtain a high-purity end-capping regulator.

[0027] Preparation of gradient alkaline salt-forming catalyst: Anhydrous sodium carbonate and anhydrous potassium carbonate were mixed at a mass ratio of 2:1.2, ball-milled at 350 r / min for 2.5 h, and passed through a 250 mesh sieve to obtain a 5-10 μm core; a 10% solid content core ethanol dispersion was prepared, and 18% by weight of nano-silica sol was added, and stirred at 450 r / min at room temperature for 25 min; coated at 75℃ for 2 h, dried at 105℃, calcined at 380℃ for 2.5 h, cooled and pulverized through a 300 mesh sieve to obtain the gradient catalyst.

[0028] Preparation of sterically hindered aromatic copolymerized monomers: 2-methylfluorobenzene and p-fluorobenzoyl chloride were fed at a molar ratio of 1:1.08, and the reaction was carried out in a dichloromethane system at room temperature at 350 r / min for 3 h, catalyzed by anhydrous aluminum trichloride. The mixture was then quenched with dilute hydrochloric acid, allowed to stand for 12 min to separate into layers, and the organic phase was washed with water and salt until neutral. The solution was removed under reduced pressure. The mixture was recrystallized from anhydrous ethanol and dried under vacuum at 95 °C for 6 h to obtain high-purity sterically hindered monomers.

[0029] A method for preparing polyetherketone ketone with adjustable molecular weight distribution includes the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, purge the air with high-purity nitrogen 4 times, control the oxygen content in the reactor to ≤80ppm and the moisture content to ≤40ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the prescribed amount of N-methylpyrrolidone and anhydrous lithium chloride to the reaction vessel, stir at 250 r / min for 20 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 20℃, and the mixture is stirred at 350r / min for 35min to make the monomers uniformly dispersed. S4. Segmented gradient temperature polymerization: A three-stage gradient temperature polymerization method is adopted, with a uniform heating rate of 4℃ / min. In the first stage, the temperature is raised to 85℃, half of the mass of gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 450 r / min for 2 h. In the second stage, the temperature is raised to 125℃, the remaining gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 550 r / min for 2.5 h. In the third stage, the temperature is raised to 165℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 650 r / min for 4 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 165℃ and add the end-group active end-capping regulator at a uniform rate for 30 minutes. After the addition is completed, keep the temperature constant for 1.5 hours to adjust the distribution within a narrow range of 1.15 to 1.39. S6. Post-treatment purification: After the reaction is completed, the temperature is naturally cooled to 70℃. The reaction solution is slowly poured into 30℃ deionized water to precipitate the polymer. The stirring speed during precipitation is 200r / min, and the precipitation time is 50min. The solid is collected by filtration and washed 4 times with boiling ethanol and 2 times with deionized water, each time for 18min. Finally, it is placed in a vacuum dryer at 130℃ and a vacuum degree ≤-0.09MPa for 10h to obtain the narrow distribution polyether ketone ketone product.

[0030] Example 2 (Medium Distribution Regulation) A polyether ketone with an adjustable molecular weight distribution comprises the following components in parts by mass: 48 parts of 4,4'-difluorobenzophenone; 36 parts of isophthaloyl chloride; 4 parts of end-capping regulator; Five parts of gradient alkaline salt-forming catalyst; Four parts of sterically hindered aromatic copolymer modifiers; 160 parts of a polar aprotic solvent (dimethylacetamide); Two parts of anhydrous lithium chloride.

[0031] Preparation of end-group active end-capping regulator: 4-hydroxybenzaldehyde and cyclobutenone were weighed at a molar ratio of 1:1.3; 4-hydroxybenzaldehyde was prepared into an 18% (w / w) anhydrous ethanol solution and stirred at 300 r / min for 12 min at room temperature until completely dissolved; cyclobutenone was added dropwise at a uniform rate for 35 min, and the mixture was heated to 60℃ and refluxed at 400 r / min for 5 h; the solution was removed under reduced pressure, crystallized at room temperature, washed twice with ice water, and dried under vacuum at 85℃ for 7 h to obtain a high-purity end-capping regulator.

[0032] Preparation of gradient alkaline salt-forming catalyst: Anhydrous sodium carbonate and anhydrous potassium carbonate were mixed at a mass ratio of 2:1.2, ball-milled at 350 r / min for 2.5 h, and passed through a 250 mesh sieve to obtain a 5-10 μm core; a 10% solid content core ethanol dispersion was prepared, and 18% by weight of nano-silica sol was added, and stirred at 450 r / min at room temperature for 25 min; coated at 75℃ for 2 h, dried at 105℃, calcined at 380℃ for 2.5 h, cooled and pulverized through a 300 mesh sieve to obtain the gradient catalyst.

[0033] Preparation of sterically hindered aromatic copolymerized monomers: 2-methylfluorobenzene and p-fluorobenzoyl chloride were fed at a molar ratio of 1:1.08, and the reaction was carried out in a dichloromethane system at room temperature at 350 r / min for 3 h, catalyzed by anhydrous aluminum trichloride. The mixture was then quenched with dilute hydrochloric acid, allowed to stand for 12 min to separate into layers, and the organic phase was washed with water and salt until neutral. The solution was removed under reduced pressure. The mixture was recrystallized from anhydrous ethanol and dried under vacuum at 95 °C for 6 h to obtain high-purity sterically hindered monomers.

[0034] A method for preparing polyetherketone ketone with adjustable molecular weight distribution includes the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, purge the air with high-purity nitrogen 4 times, control the oxygen content in the reactor to ≤80ppm and the moisture content to ≤40ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the prescribed amount of dimethylacetamide and anhydrous lithium chloride to the reaction vessel, stir at 250 r / min for 20 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 20℃, and the mixture is stirred at 350r / min for 35min to make the monomers uniformly dispersed. S4. Segmented gradient temperature polymerization: A three-stage gradient temperature polymerization method is adopted, with a uniform heating rate of 4℃ / min. In the first stage, the temperature is raised to 85℃, half of the mass of gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 450 r / min for 2 h. In the second stage, the temperature is raised to 125℃, the remaining gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 550 r / min for 2.5 h. In the third stage, the temperature is raised to 165℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 650 r / min for 4 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 165℃ and add the end-group active end-capping regulator at a uniform rate for 30 minutes. After the addition is completed, keep it at a constant temperature for 1.5 hours to adjust the distribution range to a medium-wide range of 1.40 to 1.80. S6. Post-processing purification: After the reaction is completed, the temperature is naturally cooled to 70℃. The reaction solution is slowly poured into 30℃ deionized water to precipitate the polymer. The stirring speed during precipitation is 200r / min, and the precipitation time is 50min. The solid is collected by filtration and washed 4 times with boiling ethanol and 2 times with deionized water, each time for 18min. Finally, it is placed in a vacuum dryer at 130℃ and a vacuum degree ≤-0.09MPa for 10h to obtain the medium-distribution polyether ketone ketone product.

[0035] Example 3 (Wide Distribution Regulation) A polyether ketone with an adjustable molecular weight distribution comprises the following components in parts by mass: 52 parts of 4,4'-difluorobenzophenone; 32 parts of isophthaloyl chloride; Three parts of end-capping regulator; Gradient alkaline salt-forming catalyst (7 parts); Six parts of sterically hindered aromatic copolymer modifiers; 140 parts of a polar aprotic solvent (dimethylformamide); 1.5 parts of anhydrous lithium chloride.

[0036] Preparation of end-group active end-capping regulator: 4-hydroxybenzaldehyde and cyclobutenone were weighed at a molar ratio of 1:1.4; a 20% (w / w) ethanol solution of 4-hydroxybenzaldehyde was prepared and dissolved by stirring at 350 r / min for 15 min at room temperature; cyclobutenone was added dropwise over 40 min, and the mixture was refluxed at 65℃ and 450 r / min for 6 h; the solution was removed under reduced pressure, washed three times with ice water, and dried under vacuum at 90℃ for 8 h to obtain a high-purity end-capping regulator.

[0037] Preparation of gradient alkaline salt-forming catalyst: Mix carbonates at a mass ratio of 2:1.5, ball mill at 400 r / min for 3 h, and pass through a 300 mesh sieve; prepare a 12% solid content ethanol dispersion, add 20% nano silica sol by mass of the core, stir at 500 r / min for 30 min; coat at 80℃ for 2.5 h, dry at 110℃, calcine at 400℃ for 3 h, pulverize and pass through a 300 mesh sieve for later use.

[0038] Preparation of sterically hindered aromatic copolymer modified monomer: The raw material molar ratio is 1:1.1, and the reaction is carried out at room temperature and 400 r / min for 3.5 h; the reaction is quenched and separated by dilute hydrochloric acid, washed until neutral and desolventized; recrystallized with ethanol and dried under vacuum at 100℃ for 7 h to obtain high-purity monomer.

[0039] A method for preparing polyetherketone ketone with adjustable molecular weight distribution includes the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, purge the air with high-purity nitrogen 5 times, control the oxygen content in the reactor to ≤70ppm and the moisture content to ≤35ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the prescribed amount of dimethylformamide and anhydrous lithium chloride to the reaction vessel, stir at 300 r / min for 25 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 15℃, and the mixture is stirred at 400r / min for 40min to make the monomers uniformly dispersed. S4. Segmented gradient temperature polymerization: A three-stage gradient temperature polymerization method is adopted, with a uniform heating rate of 5℃ / min. In the first stage, the temperature is raised to 90℃, half of the mass of gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 500 r / min for 1.5 h. In the second stage, the temperature is raised to 130℃, the remaining gradient basic salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 600 r / min for 2 h. In the third stage, the temperature is raised to 170℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 700 r / min for 3.5 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 170℃ and add the end-group active end-capping regulator at a uniform rate for 40 minutes. After the addition is completed, keep the temperature constant for 1 hour to adjust the wide distribution range of 1.40 to 1.80. S6. Post-processing purification: After the reaction is completed, the temperature is naturally cooled to 60℃. The reaction solution is slowly poured into 35℃ deionized water to precipitate the polymer. The stirring speed during precipitation is 250r / min, and the precipitation time is 60min. The solid is collected by filtration and washed 5 times with boiling ethanol and 3 times with deionized water, each time for 20min. Finally, it is placed in a vacuum dryer at 140℃ and a vacuum degree ≤-0.09MPa for 8h to obtain the wide-distribution polyether ketone ketone product.

[0040] Product Performance Comparison Test Table The three sets of products were tested using a unified national standard testing method. The key performance parameters and applicable scenarios are shown in the table below: Example 1 (Narrow Distribution) 1.22 98 326 Precision 3D printing, precision injection molding of micro-components Example 2 (Medium Distribution) 1.51 97 323 Conventional injection molding, general structural component molding processing Example 3 (Wide Distribution) 1.76 96 321 Extrusion of thick-walled products, functional film molding As shown in the table above, this invention can precisely achieve a continuously adjustable PEKK molecular weight distribution within the range of 1.15 to 1.80. The measured PDI values ​​for the three sets of examples are 1.22, 1.51, and 1.76. All products maintain ultra-high mechanical and heat resistance properties without significant performance degradation. Products with corresponding molecular weight distributions can be precisely matched according to different processing techniques, completely solving the technical problem of poor mold adaptability of traditional PEKK, and demonstrating significant technical advantages.

[0041] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0042] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A polyether ketone with an adjustable molecular weight distribution, characterized in that, The components include the following parts by mass: 4,4'-Difluorobenzophenone 45-55 parts; 30-38 parts of isophthaloyl chloride; 2.5–6.5 parts of end-capping regulator with active end groups; Gradient alkaline salt-forming catalyst, 4-8 parts; 3-7 parts of sterically hindered aromatic copolymer modifier; 120–180 parts of polar aprotic solvent; 1-3 parts of anhydrous lithium chloride.

2. The polyetherketone ketone with adjustable molecular weight distribution according to claim 1, characterized in that, The polar aprotic solvent is any one of N-methylpyrrolidone, dimethylformamide, and dimethylacetamide.

3. A polyether ketone ketone with adjustable molecular weight distribution according to claim 1, characterized in that, The preparation method of the terminal active end-capping regulator includes the following steps: S1.1 Raw material ratio: Weigh 4-hydroxybenzaldehyde and cyclobutenone in a molar ratio of 1:1.2 to 1.5 and set aside; S1.2 Dissolution and dispersion: Dissolve 4-hydroxybenzaldehyde in anhydrous ethanol to prepare a solution with a mass concentration of 15% to 20%, and stir at room temperature at 250 to 350 r / min for 10 to 15 min until completely dissolved; S1.3 Addition condensation: Slowly add cyclobutenone dropwise over 30-40 minutes. After the addition is complete, raise the temperature to 55-65°C and reflux at 350-450 r / min for 4-6 hours. S1.4 Purification and Drying: After the reaction is completed, remove ethanol by vacuum distillation, cool to crystallize, wash with ice water 2-3 times, filter, and dry under vacuum at 80-90℃ for 6-8 hours to obtain high-purity hydroxyphenylcyclobutenone end-capping regulator.

4. A polyetherketone ketone with adjustable molecular weight distribution according to claim 1, characterized in that, The preparation method of the gradient alkaline salt-forming catalyst includes the following steps: S2.1, Core preparation: Weigh anhydrous sodium carbonate and anhydrous potassium carbonate at a mass ratio of 2:1 to 1.5, mix them, ball mill at 300 to 400 r / min for 2 to 3 h, and pass them through a 200 to 300 mesh sieve to obtain alkaline core particles with a particle size of 5 to 10 μm. S2.2, Shell coating: Disperse the core particles in anhydrous ethanol to prepare a dispersion with a solid content of 8% to 12%, add 15% to 20% by weight of the core particles and 20 to 50 nm of nano-silica sol, and stir at room temperature at 400 to 500 r / min for 20 to 30 min. S2.3 Gradient activation: Heat to 70-80℃ and stir for 1.5-2.5h. After drying the solvent, calcine in a muffle furnace at 350-400℃ for 2-3h. Cool, pulverize, and pass through a 300-mesh sieve to obtain a core-shell structured gradient alkaline salt-forming catalyst.

5. A polyether ketone ketone with adjustable molecular weight distribution according to claim 1, characterized in that, The preparation method of the sterically hindered aromatic copolymer modifier includes the following steps: S3.1, Friedel-Crafts acylation reaction: using 2-methylfluorobenzene and p-fluorobenzoyl chloride as raw materials, with a molar ratio of 1:1.05 to 1.1, anhydrous aluminum trichloride as catalyst, and dichloromethane as solvent, the reaction is carried out at room temperature with stirring at 300 to 400 r / min for 2.5 to 3.5 h. S3.2 Hydrolysis and purification: Quench the reaction with dilute hydrochloric acid, allow to stand and separate into layers, take the organic phase, wash with deionized water and saturated brine until neutral, remove the solvent by vacuum distillation to obtain the crude monomer product; S3.3 Recrystallization purification: The crude product is recrystallized with anhydrous ethanol, filtered, and then vacuum dried at 90-100℃ for 5-7 hours to obtain a high-purity sterically hindered comonomer of 2-methyl-4,4'-difluorobenzophenone.

6. A method for preparing a polyether ketone ketone with adjustable molecular weight distribution, used to prepare the polyether ketone ketone with adjustable molecular weight distribution as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Inert atmosphere pretreatment: Take a dry and sealed polymerization reactor, and purge the air with high-purity nitrogen 3 to 5 times to control the oxygen content in the reactor to ≤100ppm and the moisture content to ≤50ppm, and maintain nitrogen micro-positive pressure protection throughout the process. S2. Preparation of base solution: Add the formulated amount of polar aprotic solvent and anhydrous lithium chloride to the reaction vessel, stir at 200-300 r / min for 15-25 min at room temperature until completely dissolved, and obtain a uniform and transparent base solution. S3. Low-temperature monomer premixing: 4,4'-difluorobenzophenone and aromatic ring hindered copolymer modified monomers are added to the base solution in sequence, the temperature is lowered to 15-25℃, and the mixture is stirred at a constant temperature of 300-400r / min for 30-40min to make the monomers uniformly dispersed. S4. Segmented gradient heating polymerization: Three-stage gradient heating polymerization is adopted, with a uniform heating rate of 3-5℃ / min; In the first stage, the temperature is raised to 80-90℃, half the mass of gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 400-500 r / min for 1.5-2.5 h. In the second stage, the temperature is raised to 120-130℃, the remaining gradient alkaline salt-forming catalyst is added, and the reaction is carried out at a constant temperature of 500-600 r / min for 2-3 h. In the third stage, the temperature is raised to 160-170℃, isophthaloyl chloride is added, and the polycondensation reaction is carried out at a constant temperature of 600-700 r / min for 3.5-4.5 h. S5. Precise control of molecular weight distribution: At the end of the polycondensation reaction, maintain the temperature at 160-170℃ and add the end-group active capping agent dropwise at a uniform rate for 20-40 minutes. After the addition is completed, let it mature at a constant temperature for 1-2 hours. When the target PDI is 1.15-1.39, use a high dose of capping agent; when the target PDI is 1.40-1.80, use a low dose of capping agent. S6. Post-treatment purification: After the reaction is completed, allow the temperature to cool naturally to 60-80℃. Slowly pour the reaction solution into deionized water at 25-35℃ to precipitate the polymer. The stirring speed during precipitation is 150-250 r / min, and the precipitation time is 40-60 min. Filter and collect the solid. Wash with boiling ethanol 3-5 times and deionized water 2-3 times, each wash lasting 15-20 min. Finally, place it under vacuum drying at 120-140℃ and a vacuum degree ≤-0.09 MPa for 8-12 h to obtain a polyether ketone ketone product with adjustable molecular weight distribution.

7. The method for preparing polyetherketone ketone with adjustable molecular weight distribution according to claim 6, characterized in that: In step S4, the heating rate of the three-stage polymerization is controlled at 3-5℃ / min.

8. The method for preparing polyetherketone ketone with adjustable molecular weight distribution according to claim 6, characterized in that: In step S6, the temperature of the precipitated water is 25-35℃, the stirring speed is 150-250 r / min, and the precipitation time is 40-60 min.