A high thermal stability fluoropolymer processing aid and its preparation method

Abstract

This invention relates to the field of fluoropolymer processing aids, specifically a high thermal stability fluoropolymer processing aid and its preparation method, comprising the following components: modified vinylidene fluoride-hexafluoropropylene copolymer, modified SiO2, fluorophosphate-quaternary ammonium salt complex, polyethylene wax, and antioxidant. The fluorophosphate-quaternary ammonium salt complex coordinates with the aluminum or magnesium hydroxyl groups on the ATH / MDH surface through phosphate end groups, and the quaternary ammonium salt end groups are synergistically anchored through electrostatic interactions, actively sealing the competitive adsorption sites of the filler under high-temperature processing conditions. The modified vinylidene fluoride-hexafluoropropylene copolymer is anchored to the modified SiO2 surface through borate ester bonds, bypassing the competitive adsorption of ATH / MDH by utilizing the partial hydrophobicity of SiO2, achieving effective interface migration and film formation. This dual synergistic mechanism significantly improves the film-forming efficiency of the processing aid in a highly filled halogen-free flame-retardant system, effectively eliminating melt fracture defects.

Description

Technical Field

[0001] This invention belongs to the field of fluoropolymer processing aids technology, specifically a high thermal stability fluoropolymer processing aid and its preparation method. Background Technology

[0002] To achieve environmentally friendly flame retardancy, aluminum hydroxide (ATH) and magnesium hydroxide (MDH) are widely used as halogen-free flame retardant fillers in wire and cable sheathing materials. However, due to the limited flame retardant efficiency of ATH and MDH, their filler content is typically as high as 50 wt% or more to achieve high flame retardant ratings. Under these high filler conditions, the melt viscosity increases sharply, the extrusion die pressure increases significantly, and quality defects such as melt fracture and excessive surface roughness appear on the product surface.

[0003] Fluoropolymer processing aids (PPAs) are a common approach to addressing the aforementioned problems. During extrusion, PPA migrates to the outer layer of the melt and forms a low surface energy lubricating film on the die metal wall, converting adhesive friction into sliding friction, thereby eliminating melt fracture and improving surface quality. However, in highly filled ATH / MDH systems, the application of PPA faces serious challenges: ATH and MDH surfaces have a large number of hydroxyl groups and a large specific surface area, exhibiting strong physical adsorption of fluoropolymers. A large number of filler particles capture and anchor PPA molecules within the melt, severely inhibiting PPA migration and accumulation at the interface. This results in insufficient effective PPA concentration on the die wall, slower film formation, prolonged induction period, and even failure to form a complete lubricating film, significantly reducing the improvement effect. Current technologies mainly alleviate these problems by increasing the amount of PPA or using surface-treated fillers, but these methods suffer from drawbacks such as high cost, limited effectiveness, and complex filler modification processes. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a high thermal stability fluoropolymer processing aid and its preparation method, so as to solve the technical problem in the prior art that the fluoropolymer processing aid in the high-filled ATH / MDH system fails to form a film and has poor processing performance due to competitive adsorption by the filler.

[0006] (2) Technical solution

[0007] To achieve the above objectives, on the one hand, the present invention provides a high thermal stability fluoropolymer processing aid, comprising the following components in parts by weight: 60-80 parts of modified vinylidene fluoride-hexafluoropropylene copolymer, 5-15 parts of modified SiO2, 3-8 parts of fluorinated phosphate-quaternary ammonium salt complex, 1-3 parts of polyethylene wax, and 0.2-0.5 parts of antioxidant;

[0008] The modified vinylidene fluoride-hexafluoropropylene copolymer is a phenylboronic acid-grafted vinylidene fluoride-hexafluoropropylene copolymer;

[0009] The modified SiO2 is vicinal diol-functionalized partially hydrophobic SiO2;

[0010] The fluorinated phosphate-quaternary ammonium salt complex has an amphiphilic structure with a fluorinated alkyl phosphate end group and a hexadecyl dimethyl quaternary ammonium group.

[0011] Furthermore, the preparation method of the modified vinylidene fluoride-hexafluoropropylene copolymer includes the following steps:

[0012] S11. Vacuum dry the vinylidene fluoride-hexafluoropropylene copolymer to remove moisture, and mix maleic anhydride, dicumyl peroxide and the dried vinylidene fluoride-hexafluoropropylene copolymer in a high-speed mixer to obtain a premix.

[0013] S12. Add the premix to a twin-screw extruder and set the temperature as follows: feed section 170℃, melting section 185℃, reaction section 200℃, discharge section 195℃, screw speed 200rpm, and water-cooled pellets to obtain maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer.

[0014] S13. Maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer was dissolved in N-methylpyrrolidone and heated and stirred under nitrogen protection. 3-aminophenylboronic acid was added in batches and stirred at 80°C. The temperature was then lowered to 50°C, and acetic anhydride and pyridine were added in sequence. The temperature was raised to 110°C and stirred. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was slowly poured into deionized water with stirring to precipitate the precipitate. The precipitate was filtered and washed in sequence with 5wt% sodium bicarbonate aqueous solution, deionized water, and ethanol. The precipitate was then dried under vacuum to obtain the modified vinylidene fluoride-hexafluoropropylene copolymer.

[0015] Furthermore, the preparation method of the modified SiO2 includes the following steps:

[0016] S21. SiO2 was dried under vacuum, anhydrous toluene was added, ultrasonically dispersed, and hexamethyldisilazane was slowly added dropwise under nitrogen protection. The mixture was heated and stirred to react, filtered, washed successively with toluene and ethanol, and dried under vacuum to obtain partially hydrophobically modified SiO2.

[0017] S22. Add some hydrophobically modified SiO2 to anhydrous toluene, disperse by ultrasonication, add γ-glycidyl ether propyltrimethoxysilane and triethylamine, heat and stir under nitrogen protection, filter, wash with toluene and ethanol successively, and dry under vacuum to obtain epoxy-SiO2.

[0018] S23. Add epoxy-SiO2 to anhydrous N,N-dimethylformamide, disperse by ultrasonication, add 3-amino-1,2-propanediol, heat and stir under nitrogen protection, filter after the reaction is complete, wash with N,N-dimethylformamide and ethanol in sequence, and dry under vacuum to obtain modified SiO2.

[0019] Furthermore, the preparation method of the fluorinated phosphate-quaternary ammonium salt complex includes the following steps:

[0020] S31. Dissolve perfluorodecyl alcohol in anhydrous diethyl ether, place in an ice bath at 0°C, slowly add P2O5 in portions under nitrogen protection, heat to room temperature and stir to react, after the reaction is complete, slowly add deionized water, stir, separate the liquid and liquid phases, wash the organic phase with saturated brine, dry with anhydrous magnesium sulfate, remove diethyl ether by vacuum distillation, separate the crude product by column chromatography, collect the monoester fraction, dry under vacuum to obtain the first compound;

[0021] S32. The first compound was dissolved in anhydrous dichloromethane and placed in an ice bath at 0°C under nitrogen protection. Oxaloyl chloride was slowly added dropwise, followed by N,N-dimethylformamide. The mixture was stirred at 0°C. Subsequently, a mixed solution of 3-dimethylamino-1-propanol and triethylamine was slowly added dropwise at 0°C. After the addition was complete, the mixture was brought to room temperature and the reaction was continued with stirring. After the reaction was complete, the mixture was filtered, and the solvent was removed by vacuum evaporation. The crude product was washed successively with saturated sodium bicarbonate aqueous solution and deionized water. The organic phase was dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum evaporation. The crude product was washed with n-hexane and dried under vacuum to obtain the second compound.

[0022] S33. The second compound was dissolved in anhydrous acetonitrile, and hexadecane bromo was added. The mixture was stirred and reacted. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The crude product was washed with anhydrous diethyl ether and dried under vacuum to obtain a fluorinated phosphate-quaternary ammonium salt complex.

[0023] Furthermore, the amount of ATH and / or MDH in the extrusion system of the application is 50 to 65 wt%, and within this range, the amount of the processing aid added is 0.1 to 0.5 wt% based on the total mass of the extrusion system.

[0024] On the other hand, based on the same inventive concept, the present invention also provides a method for preparing a high thermal stability fluoropolymer processing aid, applied to the aforementioned high thermal stability fluoropolymer processing aid, comprising the following steps:

[0025] S1. Weigh the modified vinylidene fluoride-hexafluoropropylene copolymer, modified SiO2, fluorinated phosphate-quaternary ammonium salt complex, polyethylene wax, and antioxidant, add them to a high-speed mixer and mix to fully pre-disperse each component to obtain a premix.

[0026] S2. The mixture is added to a twin-screw extruder and extruded. The extruded strip is water-cooled and pelletized to obtain a high thermal stability fluoropolymer processing aid.

[0027] Furthermore, the extrusion setting temperature is: 160°C for the feeding section, 175°C for the melting section, 180°C for the mixing section, and 175°C for the discharge section, with a screw speed of 150 rpm.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. By grafting maleic anhydride onto the ethylene-hexafluoropropylene copolymer, an anhydride active group is introduced, which improves the interfacial compatibility between the fluoropolymer and the polyolefin matrix, prevents the premature precipitation of processing aids and causes "fish-eye" defects, and provides chemical reaction sites for the subsequent introduction of phenylboronic acid groups, so that the modified ethylene-hexafluoropropylene copolymer is anchored to the modified SiO2 surface through reversible borate ester bonds.

[0030] 2. After partial hydrophobization, modified SiO2 has a weak affinity for ATH / MDH, forming a passive avoidance barrier. The introduction of the vicinal diol structure forms a reversible borate bond with the phenylboronic acid of the modified vinylidene fluoride-hexafluoropropylene copolymer.

[0031] 3. The fluorinated phosphate-quaternary ammonium salt complex actively blocks the competitive adsorption sites of ATH / MDH through a dual synergistic effect: the phosphate ester end groups coordinate with the aluminum or magnesium hydroxyl groups on the filler surface, and the quaternary ammonium salt end groups interact electrostatically. This reduces the competitive trapping ability of the filler at the source. The modified vinylidene fluoride-hexafluoropropylene copolymer is anchored to the modified SiO2 surface via borate ester bonds. The modified SiO2 itself undergoes partial hydrophobic modification, resulting in weak affinity for ATH / MDH. This allows the loaded modified vinylidene fluoride-hexafluoropropylene copolymer to bypass the competitive adsorption traps of ATH / MDH, achieving effective interfacial migration and film formation. The three components synergistically segregate and enrich at the melt / die interface. The fluorine concentration on the die wall is significantly higher than that on the matrix, doubling the film formation efficiency and drastically shortening the induction period. Stable lubricating films can be formed even with an ATH / MDH loading of ≥50wt%. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0033] Example 1: This example discloses a high thermal stability fluoropolymer processing aid, comprising the following components in parts by weight: 80 parts of modified vinylidene fluoride-hexafluoropropylene copolymer, 15 parts of modified SiO2, 8 parts of fluorophosphate-quaternary ammonium salt complex, 3 parts of polyethylene wax, and 0.5 parts of antioxidant.

[0034] The preparation method of the modified vinylidene fluoride-hexafluoropropylene copolymer includes the following steps:

[0035] S11. 100g of vinylidene fluoride-hexafluoropropylene copolymer was vacuum dried at 80℃ for 4h to remove moisture. 6g of maleic anhydride, 0.3g of dicumyl peroxide and the dried vinylidene fluoride-hexafluoropropylene copolymer were mixed in a high-speed mixer for 5min to obtain a premix.

[0036] S12. Add the premix to a twin-screw extruder (length-to-diameter ratio 36:1), set the temperature as follows: feed section 170℃, melt section 185℃, reaction section 200℃, discharge section 195℃, screw speed 200rpm, and water-cool the extruded strip to obtain maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer.

[0037] S13. Dissolve 100g of maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer in 400mL of N-methylpyrrolidone. Under nitrogen protection, heat and stir at 80℃ to dissolve. Add 8g of 3-aminophenylboronic acid in batches and stir at 80℃ for 12h. Then cool to 50℃ and add 12mL of acetic anhydride and 6mL of pyridine in sequence. Heat to 110℃ and stir for 6h. After the reaction is completed, cool to room temperature. Slowly pour the reaction solution into 5L of deionized water with stirring to precipitate the precipitate. Filter and wash successively with 5wt% sodium bicarbonate aqueous solution, deionized water, and ethanol. Dry under vacuum at 60℃ for 24h to obtain the modified vinylidene fluoride-hexafluoropropylene copolymer.

[0038] The method for preparing the modified SiO2 includes the following steps:

[0039] S21. 100g of SiO2 was dried under vacuum at 120℃ for 6h, 600mL of anhydrous toluene was added, and the mixture was ultrasonically dispersed for 30min. Under nitrogen protection, 8g of hexamethyldisilazane was slowly added dropwise, the temperature was raised to 90℃ and the mixture was stirred for 3h. The mixture was filtered, washed with toluene and ethanol in sequence, and dried under vacuum at 60℃ for 12h to obtain partially hydrophobically modified SiO2.

[0040] S22. 100g of partially hydrophobically modified SiO2 was added to 500mL of anhydrous toluene and ultrasonically dispersed for 20min. Then, 15g of γ-glycidyl ether propyltrimethoxysilane and 1.5g of triethylamine were added. The mixture was heated to 90℃ under nitrogen protection and stirred for 8h. The mixture was then filtered, washed successively with toluene and ethanol, and dried under vacuum at 50℃ for 12h to obtain epoxy-SiO2.

[0041] S23. Add 100g of epoxy-SiO2 to 500mL of anhydrous N,N-dimethylformamide, sonicate for 20min, add 18.2g of 3-amino-1,2-propanediol, heat to 70℃ under nitrogen protection and stir for 16h. After the reaction is complete, filter, wash with N,N-dimethylformamide and ethanol in sequence, and dry under vacuum at 50℃ for 24h to obtain modified SiO2.

[0042] It should be noted that the mass of hexamethyldisilazane is measured based on approximately 60% of the surface hydroxyl groups of the blocked SiO2, resulting in partially hydrophobically modified SiO2 while retaining approximately 40% of the surface silanol groups for subsequent silane coupling agent grafting.

[0043] The preparation method of the fluorinated phosphate-quaternary ammonium salt complex includes the following steps:

[0044] S31. Dissolve 51.4 g of perfluorodecyl alcohol in 200 mL of anhydrous diethyl ether, place in an ice bath at 0 °C, and slowly add 7.1 g of P2O5 in portions under nitrogen protection. Heat to room temperature and stir for 12 h. After the reaction is complete, slowly add 20 mL of deionized water and stir for 1 h. Separate the liquid and liquid phases, wash the organic phase with saturated brine, dry with anhydrous magnesium sulfate, remove diethyl ether by vacuum distillation, separate the crude product by column chromatography, collect the monoester fraction, and dry under vacuum at 50 °C for 12 h to obtain the first compound.

[0045] S32. Dissolve 47.5g of the first compound in 200mL of anhydrous dichloromethane, place in an ice bath at 0℃ under nitrogen protection, slowly add 7.5mL of oxaloyl chloride, then add 2 drops of N,N-dimethylformamide as a catalyst, stir at 0℃ for 2h, then slowly add a mixed solution of 8.7g of 3-dimethylamino-1-propanol and 21.5mL of triethylamine at 0℃. After the addition is complete, raise the temperature to room temperature and continue stirring for 12h. After the reaction is complete, filter, remove the solvent by vacuum distillation, wash the crude product successively with saturated sodium bicarbonate aqueous solution and deionized water, dry the organic phase with anhydrous magnesium sulfate, remove the solvent by vacuum distillation, wash the crude product with n-hexane, and dry under vacuum at 50℃ for 12h to obtain the second compound;

[0046] S33. The second compound was dissolved in 150 mL of anhydrous acetonitrile, and 30.0 g of hexadecane bromo was added. The mixture was stirred at 60 °C for 48 h. After the reaction was completed, the acetonitrile was removed by vacuum distillation. The crude product was washed with anhydrous diethyl ether and dried under vacuum at 50 °C for 24 h to obtain the fluorinated phosphate-quaternary ammonium salt complex.

[0047] A method for preparing a high thermal stability fluoropolymer processing aid includes the following steps:

[0048] S1. Weigh the modified vinylidene fluoride-hexafluoropropylene copolymer, modified SiO2, fluorinated phosphate-quaternary ammonium salt complex, polyethylene wax, and antioxidant, add them to a high-speed mixer and mix at 60°C for 10 minutes to fully pre-disperse the components and obtain a premix.

[0049] S2. Add the mixture to a twin-screw extruder and set the temperature as follows: feed section 160℃, melting section 175℃, mixing section 180℃, discharge section 175℃, screw speed 150rpm. Water-cool the extruded strip and cut it into pellets to obtain a high thermal stability fluoropolymer processing aid.

[0050] Example 2: This example is based on Example 1, but differs from Example 1 in that it discloses a high thermal stability fluoropolymer processing aid, comprising the following components in parts by weight: 70 parts of modified vinylidene fluoride-hexafluoropropylene copolymer, 10 parts of modified SiO2, 6 parts of fluorophosphate-quaternary ammonium salt complex, 2 parts of polyethylene wax, and 0.4 parts of antioxidant.

[0051] The other components and preparation methods are the same as in Example 1.

[0052] Example 3: This example is based on Example 1, but differs from Example 1 in that it discloses a high thermal stability fluoropolymer processing aid, comprising the following components in parts by weight: 60 parts of modified vinylidene fluoride-hexafluoropropylene copolymer, 5 parts of modified SiO2, 3 parts of fluorophosphate-quaternary ammonium salt complex, 1 part of polyethylene wax, and 0.2 parts of antioxidant.

[0053] The other components and preparation methods are the same as in Example 1.

[0054] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that an equal mass of unmodified vinylidene fluoride-hexafluoropropylene copolymer (raw material VDF-HFP copolymer, without grafted MAH and phenylboronic acid) is used instead of modified vinylidene fluoride-hexafluoropropylene copolymer.

[0055] The other components and preparation methods are the same as in Example 1.

[0056] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified SiO2 in this comparative example is not hydrophobically modified, but directly modified with vicinal diol.

[0057] The other components and preparation methods are the same as in Example 1.

[0058] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that the modified SiO2 described in this comparative example does not undergo vicinal diol functionalization modification, that is, it only undergoes partial hydrophobic modification.

[0059] The other components and preparation methods are the same as in Example 1.

[0060] Comparative Example 4: This comparative example is based on Example 1, but differs from Example 1 in that it uses an equal mass of fluorinated phosphate monoester (S31 product) containing only phosphate ester end groups and no quaternary ammonium salt end groups to replace the fluorinated phosphate ester-quaternary ammonium salt complex.

[0061] The other components and preparation methods are the same as in Example 1.

[0062] Comparative Example 5: This comparative example is based on Example 1, but differs from Example 1 in that it uses an equal mass of perfluorodecyl alcohol to replace the fluorinated phosphate-quaternary ammonium salt complex, i.e., it does not contain phosphate ester end groups and quaternary ammonium salt end groups.

[0063] The other components and preparation methods are the same as in Example 1.

[0064] Comparative Example 6: This comparative example is based on Example 1, but differs from Example 1 in that it is prepared by directly mixing 70 parts of commercially available vinylidene fluoride-hexafluoropropylene copolymer, 3 parts of polyethylene wax, and 0.5 parts of antioxidant, without adding modified SiO2 and fluorinated phosphate-quaternary ammonium salt complex, and serves as a blank control for traditional processing aids.

[0065] Experimental verification:

[0066] Experiment 1:

[0067] (1) Thermogravimetric analysis (TGA): Thermogravimetric analyzer was used to heat the temperature from room temperature to 600℃ at a rate of 10℃ / min under nitrogen atmosphere. The 5% thermogravimetric temperature and the maximum thermal decomposition rate temperature were recorded to evaluate the thermal stability of the processing aid.

[0068] (2) Melting point and melt viscosity: The melting point was determined using a differential scanning calorimeter (DSC) at a heating rate of 10℃ / min; the melt viscosity was determined using a capillary rheometer at 190℃ and a shear rate of 100 s⁻¹. -1 Melt viscosity was determined under the specified conditions.

[0069] Table 1: Test results of basic performance of processing aids:

[0070]

[0071] The basic performance test results of the processing aid are shown in Table 1. The 5% thermogravimetric temperature and maximum thermal decomposition rate temperature of Examples 1-3 are significantly higher than those of the comparative examples, indicating that the processing aid of the present invention has excellent thermal stability and can meet the requirements of high-temperature extrusion processing conditions. Compared with Comparative Example 6 (conventional commercial grade PPA), Example 1 has a lower melt viscosity, which is beneficial for migration to the die wall and film formation during processing. The introduction of modified SiO2 and fluorinated phosphate-quaternary ammonium salt complex both contribute to the improvement of the thermal stability of the processing aid itself.

[0072] Experiment 2:

[0073] The following halogen-free flame-retardant polyolefin formulation was used as the base extrusion system: 100 parts linear low-density polyethylene (LLDPE), 100 parts ATH, 50 parts MDH, 2 parts silane coupling agent, and 0.5 parts antioxidant 1010. The addition amount of each processing aid was 0.3 wt% of the total mass of the extrusion system. Extrusion was performed using a single-screw extruder (screw diameter 45 mm, L / D ratio 25:1), with a die diameter of 3 mm. The extrusion temperatures were: feeding section 160℃, compression section 175℃, homogenization section 185℃, and die section 190℃; screw speed 60 rpm; and traction speed 10 m / min.

[0074] The evaluation indicators are as follows: (1) Melt fracture elimination induction period: the time (min) required from the start of extrusion to the complete elimination of surface defects of the extrudate;

[0075] (2) Surface roughness Ra of extruded material: measured using a contact roughness tester;

[0076] (3) Die pressure drop (MPa): Record the die inlet pressure during steady-state extrusion;

[0077] (4) Mechanical properties of extruded materials: Tensile strength (MPa) was determined according to GB / T 1040 standard, and the effect of processing aids on the mechanical properties of the matrix was evaluated.

[0078] The control group without added processing aids was used as a blank control group.

[0079] Table 2: Application performance test results of halogen-free flame-retardant polyolefin extrusion system:

[0080]

[0081] The performance test results of the halogen-free flame-retardant polyolefin extrusion system are shown in Table 2. As can be seen from the table, in Examples 1-3, under high-fill conditions of ATH / MDH, the melt fracture elimination induction period was significantly shorter than that of the comparative examples. Specifically, the induction period of Example 1 was only 7-9 min, while the induction period of traditional commercial PPA (Comparative Example 6) was 38-43 min. The surface roughness Ra of the extrudates from Examples 1-3 was all below 0.6 μm, and the die pressure drop was significantly lower than that of the blank group, indicating that the processing aid of this invention has excellent lubrication and film-forming efficiency in the high-fill halogen-free flame-retardant system. The tensile strength of the extrudates from Examples 1-3 was superior to that of the comparative examples, indicating that the compatibility of the modified VDF-HFP copolymer with the polyolefin matrix was effectively improved, and the processing aid did not affect the mechanical properties of the product.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high thermal stability fluoropolymer processing aid, characterized in that, The product comprises the following components in parts by weight: 60-80 parts of modified vinylidene fluoride-hexafluoropropylene copolymer, 5-15 parts of modified SiO2, 3-8 parts of fluorinated phosphate-quaternary ammonium salt complex, 1-3 parts of polyethylene wax, and 0.2-0.5 parts of antioxidant. The modified vinylidene fluoride-hexafluoropropylene copolymer is a phenylboronic acid-grafted vinylidene fluoride-hexafluoropropylene copolymer; The modified SiO2 is vicinal diol-functionalized partially hydrophobic SiO2; The fluorinated phosphate-quaternary ammonium salt complex has an amphiphilic structure with a fluorinated alkyl phosphate end group and a hexadecyl dimethyl quaternary ammonium group.

2. The high thermal stability fluoropolymer processing aid according to claim 1, characterized in that, The preparation method of the modified vinylidene fluoride-hexafluoropropylene copolymer includes the following steps: S11. Vacuum dry the vinylidene fluoride-hexafluoropropylene copolymer to remove moisture, and mix maleic anhydride, dicumyl peroxide and the dried vinylidene fluoride-hexafluoropropylene copolymer in a high-speed mixer to obtain a premix. S12. Add the premix to a twin-screw extruder and set the temperature as follows: feed section 170℃, melting section 185℃, reaction section 200℃, discharge section 195℃, screw speed 200rpm, and water-cooled pellets to obtain maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer. S13. Maleic anhydride-grafted vinylidene fluoride-hexafluoropropylene copolymer was dissolved in N-methylpyrrolidone and heated and stirred under nitrogen protection. 3-aminophenylboronic acid was added in batches and stirred at 80°C. The temperature was then lowered to 50°C, and acetic anhydride and pyridine were added in sequence. The temperature was raised to 110°C and stirred. After the reaction was completed, the mixture was cooled to room temperature. The reaction solution was slowly poured into deionized water with stirring to precipitate the precipitate. The precipitate was filtered and washed in sequence with 5wt% sodium bicarbonate aqueous solution, deionized water, and ethanol. The precipitate was then dried under vacuum to obtain the modified vinylidene fluoride-hexafluoropropylene copolymer.

3. The high thermal stability fluoropolymer processing aid according to claim 1, characterized in that, The method for preparing the modified SiO2 includes the following steps: S21. SiO2 was dried under vacuum, anhydrous toluene was added, ultrasonically dispersed, and hexamethyldisilazane was slowly added dropwise under nitrogen protection. The mixture was heated and stirred to react, filtered, washed successively with toluene and ethanol, and dried under vacuum to obtain partially hydrophobically modified SiO2. S22. Add some hydrophobically modified SiO2 to anhydrous toluene, disperse by ultrasonication, add γ-glycidyl ether propyltrimethoxysilane and triethylamine, heat and stir under nitrogen protection, filter, wash with toluene and ethanol successively, and dry under vacuum to obtain epoxy-SiO2. S23. Add epoxy-SiO2 to anhydrous N,N-dimethylformamide, disperse by ultrasonication, add 3-amino-1,2-propanediol, heat and stir under nitrogen protection, filter after the reaction is complete, wash with N,N-dimethylformamide and ethanol in sequence, and dry under vacuum to obtain modified SiO2.

4. The high thermal stability fluoropolymer processing aid according to claim 1, characterized in that, The preparation method of the fluorinated phosphate-quaternary ammonium salt complex includes the following steps: S31. Dissolve perfluorodecyl alcohol in anhydrous diethyl ether, place in an ice bath at 0°C, slowly add P2O5 in portions under nitrogen protection, heat to room temperature and stir to react, after the reaction is complete, slowly add deionized water, stir, separate the liquid and liquid phases, wash the organic phase with saturated brine, dry with anhydrous magnesium sulfate, remove diethyl ether by vacuum distillation, separate the crude product by column chromatography, collect the monoester fraction, dry under vacuum to obtain the first compound; S32. The first compound was dissolved in anhydrous dichloromethane and placed in an ice bath at 0°C under nitrogen protection. Oxaloyl chloride was slowly added dropwise, followed by N,N-dimethylformamide. The mixture was stirred at 0°C. Subsequently, a mixed solution of 3-dimethylamino-1-propanol and triethylamine was slowly added dropwise at 0°C. After the addition was complete, the mixture was brought to room temperature and the reaction was continued with stirring. After the reaction was complete, the mixture was filtered, and the solvent was removed by vacuum evaporation. The crude product was washed successively with saturated sodium bicarbonate aqueous solution and deionized water. The organic phase was dried over anhydrous magnesium sulfate, and the solvent was removed by vacuum evaporation. The crude product was washed with n-hexane and dried under vacuum to obtain the second compound. S33. The second compound was dissolved in anhydrous acetonitrile, and hexadecane bromo was added. The mixture was stirred and reacted. After the reaction was complete, the acetonitrile was removed by vacuum distillation. The crude product was washed with anhydrous diethyl ether and dried under vacuum to obtain a fluorinated phosphate-quaternary ammonium salt complex.

5. The application of the high thermal stability fluoropolymer processing aid as described in claim 1 in the extrusion of halogen-free flame-retardant polyolefin wire and cable sheaths, characterized in that, The amount of ATH and / or MDH in the extrusion system of the application is 50 to 65 wt%, and within this range, the amount of the processing aid added is 0.1 to 0.5 wt% based on the total mass of the extrusion system.

6. A method for preparing a high thermal stability fluoropolymer processing aid, applied to the preparation of a high thermal stability fluoropolymer processing aid as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: S1. Weigh the modified vinylidene fluoride-hexafluoropropylene copolymer, modified SiO2, fluorinated phosphate-quaternary ammonium salt complex, polyethylene wax, and antioxidant, add them to a high-speed mixer and mix to fully pre-disperse each component to obtain a premix. S2. The mixture is added to a twin-screw extruder and extruded. The extruded strip is water-cooled and pelletized to obtain a high thermal stability fluoropolymer processing aid.

7. The method for preparing a high thermal stability fluoropolymer processing aid according to claim 6, characterized in that, The extrusion settings are: 160°C for the feeding section, 175°C for the melting section, 180°C for the mixing section, and 175°C for the discharge section; the screw speed is 150 rpm.

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