Anti-static PFA tube and preparation method thereof

Abstract

The invention relates to the technical field of polytetrafluoroethylene, in particular to an anti-static PFA tube and a preparation method thereof. The problem that the antistatic effect and the mechanical property of PFA cannot be simultaneously achieved is solved. On the aspect of improvement of the anti-static performance, a conductive network is constructed through urea hydrolysis and parameter regulation and control by optimizing a conductive metal particle preparation process and a composite formula, and premixing and surface modification of an antistatic agent are combined, so that the volume resistivity is reduced, and static accumulation is prevented; aiming at the mechanical property, the coupling agent is used for modifying the filler to enhance the compatibility, the extruder process is regulated and controlled to promote filler dispersion and molecular chain orientation, the compatibilizer is introduced to inhibit excessive crosslinking of molecular chains, and the tensile strength and the elongation at break are remarkably improved; in the aspect of element migration control, the release of metal and fluorine ions is inhibited by virtue of the synergistic effect of a coupling agent and an antioxidant through raw material optimization and process improvement. By means of the technical means, the anti-static PFA pipe has excellent anti-static performance, mechanical strength and safety.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene, in particular to an antistatic PFA tube and a preparation method thereof. Background Art

[0002] Due to its excellent chemical stability, corrosion resistance, high-temperature resistance, and good processing properties, PFA (soluble polytetrafluoroethylene) tubing has been widely used in many fields, including chemical, semiconductor, and pharmaceutical industries. However, existing PFA tubing has a prominent problem during practical use: static electricity. In static-sensitive industries such as semiconductor manufacturing and pharmaceuticals, static electricity generated by PFA tubing can attract dust and impurities, affecting product quality. Static discharge can also damage electronic components, leading to production equipment failures and even serious safety hazards such as fires and explosions. Furthermore, there are limited measures to improve the antistatic properties of conventional PFA tubing. For example, simply adding antistatic agents, while able to reduce static electricity generation to a certain extent, can affect the chemical stability and mechanical properties of the PFA tubing itself. Furthermore, when chemical raw materials are heated at high temperatures, the volume resistivity of PFA tubing increases, reducing its antistatic effect and thus hindering the chemical reaction process. Furthermore, added antistatic inorganic materials have poor compatibility with PFA tubing and are prone to precipitation at high temperatures and during repeated use, causing cracks in the PFA tubing and reducing its durability. In summary, the PFA tubes in the prior art cannot meet the requirements for comprehensive performance of PFA tubes in specific application scenarios.

[0003] Therefore, it is urgent to develop a technical solution that can effectively solve the static electricity problem of PFA tubes while taking into account the mechanical properties and safety of PFA tubes. This is also an important direction for the current improvement of PFA tube technology. To this end, an anti-static PFA tube and its preparation method are proposed. Summary of the Invention

[0004] The present invention aims to provide an antistatic PFA tube and its preparation method. In terms of antistatic performance, a uniform alkaline environment is created by using urea slow-release hydrolysis, and the reaction between metal salts and ligands is precisely controlled to generate iron-aluminum-oxygen composite conductive particles. The antistatic agent is pre-mixed with fluorinated imidazolium ionic liquid to inhibit molecular chain crosslinking. A plasma surface treatment forms an ion conductive layer, constructing a continuous conductive network, effectively reducing volume resistivity and preventing static electricity accumulation. In terms of mechanical performance, the conductive filler is surface modified by a coupling agent to enhance its interfacial bonding with the PFA matrix. The molecular chain orientation is optimized by combining the high-temperature shear and biaxial stretching directional arrangement of the twin-screw extrusion process. A perfluoropolyether compatibilizer is introduced to enhance the interfacial strength, resulting in the tube having both high tensile strength and excellent ductility. In terms of safety, the coupling agent chemical bonding inhibits the dissolution of metal ions, the antioxidant maintains the stability of the fluorocarbon chain, and the pore structure and dispersion process are optimized to significantly reduce the migration of fluoride ions and metal elements, ensuring that the material meets the safety threshold during long-term use. Through systematic innovation in process and formulation, the antistatic performance, mechanical strength, and environmental safety of the PFA tube are synergistically improved.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing an antistatic PFA tube, and the preparation method is as follows:

[0007] 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix and 0.7-1.5 parts of fluorinated imidazolium ionic liquid are mixed, extruded through a twin-screw extruder at 270-300° C. in zone I, 310-320° C. in zone II, 325-335° C. in zone III and 315-330° C. in the die, cooled, stretched and treated with mixed gas to obtain an antistatic PFA tube;

[0008] The stretching conditions are as follows: the antistatic PFA tube precursor is preheated to 280°C and biaxially stretched at a rate of 1 m / min with a longitudinal / transverse stretch ratio of 2:1. The wall thickness before stretching is 2.0 mm, and the wall thickness after stretching is 0.475-0.525 mm. The wall thickness error of the tube after stretching is less than 5%. During the extrusion process, the screw speed is set at 80 r / min and the melt pressure is set at 8-10 MPa.

[0009] The mixed gas is obtained by mixing argon and oxygen in a volume ratio of 8:2;

[0010] The pretreated PFA resin is obtained by premixing PFA resin and antistatic agent;

[0011] The premix is obtained by mixing 7.5-9 parts of coupling agent modified conductive metal particles, 1.5-3 parts of coupling agent modified conductive carbon black and 0.5-1.2 parts of perfluoropolyether; the average particle size of the conductive carbon black used in the coupling agent modified conductive carbon black is 200nm.

[0012] Preferably, the mass mixing ratio of the PFA resin to the antistatic agent is 150:0.3-0.8.

[0013] Preferably, the flow rate of the mixed gas treatment is 50-80 sccm.

[0014] Preferably, the coupling agent modified conductive metal particles are obtained by immersing the conductive metal particles in a coupling agent ethanol solution; the coupling agent modified conductive carbon black is obtained by immersing the conductive carbon black in a coupling agent ethanol solution; and the coupling agent is γ-methacryloxypropyltrimethoxysilane.

[0015] Preferably, the conductive metal particles are prepared by dissolving ligand 1 and ligand 2 in deionized water, adding urea, stirring at 55-65°C, heating to 85-95°C, and heating for 7-9.5 hours to perform a uniform precipitation reaction. The obtained precipitate is washed and dried, calcined at 450-600°C, and then cooled at 5-10°C / min, kept warm, and cooled to obtain the conductive metal particles.

[0016] Preferably, the first ligand is one of ferric nitrate, silver nitrate and copper nitrate; the second ligand is aluminum nitrate; and the molar mass ratio of the first ligand, the second ligand and urea is 1:0.10-0.25:1.5-4 mol.

[0017] The present invention also provides an antistatic PFA tube, which is prepared by any of the above preparation methods. The raw materials for preparing the antistatic PFA tube include: 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix and 0.7-1.5 parts of fluorinated imidazolium ionic liquid; the raw materials for preparing coupling agent-modified conductive metal particles are coupling agent and conductive metal particles; the average particle size of the conductive metal particles is 290-500nm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. Antistatic performance is significantly improved by optimizing the conductive metal particle preparation process and the PFA tubing composite formula. By slowly hydrolyzing urea to create a uniform alkaline environment, and precisely controlling the metal salt, ligand, and reaction conditions, iron-aluminum-oxygen composite particles with an optimal particle size and specific surface area are generated, forming a continuous conductive network. Furthermore, by premixing an antistatic agent and using a fluorinated imidazolium ionic liquid to inhibit molecular chain crosslinking, and using a mixed gas to modify the tubing surface, the formation of an ionically conductive layer is promoted. These multiple technologies work synergistically to effectively reduce the volume resistivity of the PFA tubing, prevent static electricity accumulation, and ensure reliable antistatic performance.

[0020] 2. The surface of the conductive filler is modified by a coupling agent to form a chemical bond, thereby enhancing the compatibility between the filler and the PFA resin and reducing interface defects. The temperature and shear force of the twin-screw extruder are regulated to ensure uniform dispersion of the filler, and the longitudinal and transverse stretch ratios are set to promote orderly orientation of the molecular chains. In addition, a perfluoropolyether compatibilizer is introduced to strengthen interfacial bonding and inhibit excessive cross-linking of the PFA molecular chains. The above conditions synergistically improve the pipe structure, significantly increasing the tensile strength and elongation at break of the PFA pipe, giving the product both excellent toughness and deformation resistance.

[0021] 3. Low element migration is achieved through dual optimization of raw materials and processes. A coupling agent forms a stable barrier on the filler surface, effectively inhibiting metal ion dissolution. Antioxidants are combined to inhibit high-temperature degradation, maintain the integrity of the fluorocarbon chain structure, and reduce fluoride ion release. Furthermore, the preparation method of the conductive metal particles is optimized to enhance compatibility with the resin matrix, avoiding ion migration caused by pore structure defects or material agglomeration. By precisely controlling parameters in each link, PFA tubing maintains excellent antistatic properties while keeping element migration levels far below the safety threshold, ensuring high safety and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of the method for preparing the antistatic PFA tube of the present invention;

[0023] Figure 2 This is a diagram showing the element migration results of the antistatic PFA tube of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] See also Figures 1 to 2 The present invention provides an antistatic PFA tube and a preparation method thereof, and the technical solution is as follows:

[0026] Ferric nitrate (Fe(NO3)3·9H2O) CAS: 7782-61-8; aluminum nitrate (Al(NO3)3·9H2O) CAS: 7784-27-2; urea CAS: 57-13-6; copper nitrate hexahydrate CAS: 13478-38-1; γ-methacryloyloxypropyltrimethoxysilane (KH570) CAS: 2530-85-0; fluorinated imidazolium ionic liquid (1-ethyl-3-methylimidazolinium bis(trifluoromethylsulfonyl)imide) CAS: 174899-82-2; Irganox 1010 CAS: 6683-19-8; antistatic agent purchased from Kenao Trading (Shanghai) Co., Ltd., brand MV2080.

[0027] It should be noted that all parts in the present invention are parts by mass; the room temperature mentioned is 25°C.

[0028] Example 1

[0029] The preparation method of conductive metal particles is as follows: 1 mol of ferric nitrate and 0.15 mol of aluminum nitrate are dissolved in 500 mL of deionized water to obtain a mixed metal solution; then 3 mol of urea is added, stirred at 60°C for 30 minutes, then raised to 95°C at a rate of 2°C / min, and heated for 8 hours for a uniform precipitation reaction. The obtained precipitate is washed with ethanol and deionized water three times each, placed in an oven to dry, and dried at 120°C for 4 hours to obtain a conductive metal particle intermediate; transferred to a muffle furnace, calcined at 500°C for 3 hours, reduced to 80°C at a rate of 5°C / min, kept warm for 2 hours, and naturally cooled to room temperature to obtain conductive metal particles.

[0030] The preparation method of coupling agent modified conductive metal particles is as follows: the conductive metal particles are immersed in 30wt% KH-570 ethanol solution with a solid-liquid ratio of 1:50, ultrasonically treated for 1 hour, filtered, and dried at 80°C to obtain coupling agent modified conductive metal particles.

[0031] The preparation method of the coupling agent modified conductive carbon black is consistent with the preparation method of the coupling agent modified conductive metal particles, except that the conductive metal particles are replaced by conductive carbon black, and other conditions remain unchanged.

[0032] 0.5 parts of antistatic agent were premixed with 150 parts of PFA resin and dried at 60°C for 2 hours to obtain pretreated PFA resin; 8 parts of coupling agent-modified conductive metal particles, 2 parts of coupling agent-modified conductive carbon black and 0.5 parts of perfluoropolyether (PFPE) were mixed at 500 r / min for 5 minutes to obtain a premix; 150.5 parts of pretreated PFA resin, 10.5 parts of premix, 1 part of fluorinated imidazole ionic liquid and 0.2 parts of Irganox 1010 antioxidant were added to a high-speed mixer and mixed at 800 r / min for 10 minutes to ensure uniform dispersion to obtain a mixture; the mixture was transferred to a twin-screw extruder with an L / D value of 52 and the temperatures set in different zones as follows: 300°C in zone I, 320°C in zone II, 330°C in zone III and 325°C in the die head. After extrusion, the mixture was water-cooled at 15°C to obtain an antistatic PFA tube precursor;

[0033] The antistatic PFA tube precursor was preheated to 280°C and biaxially stretched at a rate of 1 m / min to obtain an antistatic PFA tube intermediate. Finally, the surface of the antistatic PFA tube intermediate was treated with mixed gas for 10 minutes under the conditions of a vacuum degree of 1 Pa and a power of 100 W. The treatment flow rate of the mixed gas was 60 sccm to obtain an antistatic PFA tube.

[0034] The overall preparation methods for Examples 2-5 were the same as those for Example 1, except that the method for preparing the conductive metal particles was modified, as shown in Table 1. The mixed metal solution contained ligand 1 and ligand 2, with ligand 2 being aluminum nitrate. Temperature 1 was the reaction temperature after the addition of urea, and Temperature 2 was the heating temperature.

[0035] Table 1 Preparation conditions of conductive metal particles

[0036]

[0037] Comparative Examples 1-8 were prepared in the same manner as in Example 1 except for the differences listed below.

[0038] In Comparative Example 1, only 0.25 mol of aluminum nitrate was added, and no iron nitrate was added.

[0039] In Comparative Example 2, only 0.25 mol of ferric nitrate was added, and no aluminum nitrate was added.

[0040] Comparative Example 3: Urea was replaced by an equimolar amount of sodium hydroxide.

[0041] In Comparative Example 4, urea was replaced by 3% wt ammonia water, and the molar amount of ammonia was 3 mol.

[0042] Comparative Example 5 Aluminum nitrate, ferric nitrate and urea were mixed simultaneously.

[0043] In Comparative Example 6, after adding urea, the temperature was directly raised from room temperature to 95°C at a rate of 2°C / min.

[0044] The cooling rate after calcination in Comparative Example 7 was 30°C / min.

[0045] Comparative Example 8 was calcined and then cooled to room temperature at a rate of 5°C / min.

[0046] Experimental Example 1

[0047] The particle size and specific surface area of the conductive metal particles obtained in Examples 1-5 and Comparative Examples 1-8 were measured. The particle size of the conductive metal particles was measured according to GB / T 1480-2025, and the specific surface area was measured using the BET method. The test results are shown in Table 2.

[0048] Table 2 Particle size and specific surface area test results

[0049]

[0050] The conductive metal particles prepared by the present invention have an average particle size of 290-500 nm and a specific surface area of 1.50-2.20 m 2 ·g- 1 Under the conditions of Example 1, urea is slowly hydrolyzed at a high temperature of 95°C to produce NH3 and CO2. NH3 is further hydrolyzed to NH4+ and OH-, and CO2 to CO3. 2 -, forming a uniform alkaline environment, Fe 3 + and Al 3 + and OH-, CO3 2 -reaction to generate a basic carbonate precursor (Fe / Al-CO3-OH complex), and local oversaturation is avoided by slow hydrolysis of urea, so that the precipitated particles are uniform in size; then, after high-temperature calcination, the precursor decomposes into Fe-Al oxide, specifically decomposes into a complex of Fe3O4 and Al2O3, and releases CO2 and H2O during the calcination process to form a mesoporous structure. The temperature is slowly cooled at an appropriate cooling rate, and the temperature is kept for a certain period of time after cooling, thereby reducing thermal stress and retaining the pore structure; Examples 2-5 adjust the type of ligand 1, the amount of ligand 2 and urea, and the reaction conditions, so that the prepared conductive metal particles have a suitable particle size and specific surface area; Example 2 increases the amount of aluminum nitrate, Al 3 +Inhibits Fe 3+ lattice growth, particle size increase, 10 ℃ / min rapid cooling pores partially collapsed, the specific surface area decreased; Example 3 calcination temperature increased to 550 ℃, promote the closure of some pores, but the particle size is small, the particles sintering is slight, the specific surface area is slightly reduced; Example 4 silver nitrate replaces ferric nitrate, Ag + reduction generates metallic silver, Ag particles are easy to agglomerate, the particles are coarsened; the specific surface area is the lowest after low temperature calcination; Example 5 copper nitrate calcination temperature is too high resulting in CuO grain coarsening, pore collapse. Comparative Example 1 only Al 3 + precipitation to form Al2O3 agglomerates with dense structure and low specific surface area; in comparative example 2, only Fe 3 + Large Fe2O3 particles are generated, which are dense and pore-free, and the specific surface area is reduced; the rapid precipitation of NaOH in comparative example 3 leads to micron-sized blocks with very few pores and a reduced specific surface area; the local pH fluctuation of ammonia water in comparative example 4 generates coarse particles with uneven pore distribution and a slightly higher specific surface area than comparative example 3; in comparative example 5, urea and metal salt are not fully mixed, the particle size is uneven, and micropores remain in some areas; in comparative example 6, direct heating at room temperature leads to insufficient hydrolysis, slightly smaller particle size, and a small amount of residual mesopores; in comparative example 7, rapid cooling leads to micro-cracks in the particles, but the pores are not effectively retained, and the specific surface area is medium; in comparative example 8, the temperature is directly cooled to room temperature at a fixed rate without insulation, resulting in collapse of the pores inside the particles, and the particles agglomerate and coarsen due to thermal stress, with a significantly reduced specific surface area.

[0051] Experimental Example 2

[0052] The antistatic PFA tubes obtained in the above examples and comparative examples were tested for volume resistivity. According to GB / T1410-2006, the volume resistivity was ≤1×10 7 The results of Ω·cm meet the requirements. The test results are shown in Table 3.

[0053] Table 3 Volume resistivity test results

[0054]

[0055] The volume resistivity of the antistatic PFA tube prepared by the present invention under the conditions of Examples 1-5 is 2.75×10 6 to 5.89×10 6Ω·cm. By adjusting the preparation method of the conductive metal particles, the conductive metal particles are made to have a suitable particle size and specific surface area, so that the PFA tube has a lower volume resistivity, thereby improving its antistatic effect. In Examples 1-3, uniform iron-aluminum-oxygen composite particles are generated under urea hydrolysis, the conductive network is dense and continuous, and the resistance is relatively low; in Example 4, the amount of aluminum nitrate is reduced, but the substance type of ligand one is replaced by silver nitrate from iron nitrate, and the stirring temperature, heating temperature and calcination conditions are adjusted to minimize the volume resistivity, and static electricity is not easily accumulated in the PFA tube; under the conditions of Example 5, the preparation method is adjusted, and the PFA tube also has a good antistatic effect; although the volume resistivity of Examples 4 and 5 is relatively small, considering the cost of use, the conditions of Examples 1-3 are selected for subsequent experiments. Overall, the conductive metal particles prepared in Examples 1-5 have a suitable particle size and specific surface area, which improves the conductive effect of the PFA tube and enhances the antistatic ability. Comparative Example 1, in which only aluminum nitrate was added, produced only the insulating Al2O3 phase, with no conductive phase. This significantly increased resistance and reduced antistatic effectiveness. Comparative Example 2, in which only the semiconductor Fe2O3 was formed, exhibited weaker conductivity than Fe3O4 and a slightly higher resistance, but still lower than Comparative Example 1. Comparative Example 3, in which NaOH was used for rapid precipitation, produced large Fe2O3 particles, resulting in a discontinuous conductive network and the highest resistance. Comparative Example 4, in which ammonia was used for precipitation, produced uneven particles, leading to an imbalance in the iron-aluminum ratio, a sparse conductive network, and increased volume resistivity. Comparative Example 5, in which the metal salts were unevenly mixed, exhibited partial loss of the conductive network, but a small amount of Fe3O4 phase remained. The volume resistivity was improved compared to Example 1. Comparative Example 6, in which urea was added without heating and stirring, but the temperature was directly raised from room temperature to 95°C at a rate of 2°C / min. This produced smaller conductive particles with residual mesopores, a superior conductive network, and a resistance close to that of Example 1. Comparative Example 7, in which rapid cooling resulted in microcracks, but some pores were retained, resulting in moderate resistance. Comparative Example 8, in which no heat preservation was performed, resulted in particle agglomeration, a breakdown of the conductive network, and a significant increase in resistance. In summary, the conductive metal particles prepared by the present invention have a high specific surface area and a suitable average particle size, regulate the density and continuity of the conductive network, and synergistically optimize the electron transmission path. By adjusting the specific calcination and cooling parameters of the preparation method and changing the particle morphology, electron transmission is further enhanced, thereby making the PFA tube have a good antistatic effect.

[0056] Examples 6-9 were consistent with Example 3 except for the changes in the amounts and conditions of raw material mixing, as shown in Table 4. It should be noted that the amounts of pretreated PFA resin and premix varied with the amounts of antistatic agent, coupling agent-modified conductive metal particles, coupling agent-modified conductive carbon black, and perfluoropolyether. For example, under the conditions of Example 6, the amount of pretreated PFA resin was 150.3 parts and the amount of premix was 12.3 parts.

[0057] Table 4 Raw material mixing and conditions

[0058]

[0059] Comparative Examples 9-17 were prepared in the same manner as in Example 3 except for the differences listed below.

[0060] In Comparative Example 9, no coupling agent was used to modify the conductive metal particles; and no coupling agent was used to modify the conductive carbon black.

[0061] In Comparative Example 10, no coupling agent was added to modify the conductive metal particles.

[0062] In Comparative Example 11, no coupling agent was added to modify the conductive carbon black.

[0063] Comparative Example 12: No coupling agent was added to modify the conductive metal particles, and the conductive metal particles were modified with a coupling agent.

[0064] In Comparative Example 13, the PFA resin was not pretreated, that is, the antistatic agent was added to the PFA resin during the final mixing.

[0065] In Comparative Example 14, the coupling agent-modified conductive metal particles, the coupling agent-modified conductive carbon black, and the perfluoropolyether were not premixed in advance.

[0066] In Comparative Example 15, no antistatic agent, perfluoropolyether, or fluorinated imidazolium ionic liquid was added.

[0067] The temperatures of the three zones and the die head of the twin-screw extruder of Comparative Example 16 are 250, 290, 310 and 300°C, respectively.

[0068] In Comparative Example 17, no mixed gas was used for surface treatment.

[0069] Experimental Example 3

[0070] The PFA tubes obtained in Example 3, Examples 6-9, and Comparative Examples 9-17 were subjected to volume resistivity and mechanical property testing. Volume resistivity was measured using the same testing method as in Experimental Example 2. Mechanical properties were tested primarily for tensile strength and elongation at break according to GB / T 2567-2021. Tensile strength results of ≥1.5 MPa met the requirements, and elongation at break of ≥20% met the requirements. The test results are shown in Table 5.

[0071] Table 5 Volume resistivity test and mechanical properties test results

[0072]

[0073] The antistatic PFA tube prepared by the present invention has a volume resistivity of 4.57×10 6 -6.25×10 6Ω·cm, tensile strength is 27.5-31.1MPa, and elongation at break is 280%-345%. Conductive metal particles and conductive carbon black are modified using a coupling agent. The coupling agent hydrolyzes on the filler surface to form silanol groups, which then form chemical bonds with active hydroxyl groups on the surface of the conductive metal particles. This improves the compatibility of the conductive metal particles and conductive carbon black with the PFA resin, enhancing the mechanical properties of the final PFA tubing. The modified filler is evenly dispersed, reducing defects in the conductive network. Antistatic properties are enhanced by premixing an antistatic agent with PFA. The antistatic agent and fluorinated imidazolium ionic liquid inhibit excessive crosslinking of the PFA molecular chains, maintaining material toughness. Perfluoropolyether acts as a compatibilizer, with its fluorocarbon segments co-crystallizing with PFA and carboxylic acid groups bonding with the filler, further enhancing interfacial strength. Temperatures in different zones of the twin-screw extruder are adjusted to achieve optimal high temperatures and high shear forces to ensure uniform filler dispersion. A longitudinal / transverse stretch ratio of 2:1 helps improve molecular chain orientation and mechanical strength. Finally, the PFA tubing surface is treated with a mixed gas to generate active free radicals under vacuum, forming surface polar groups that absorb water to form an ionically conductive layer, reducing volume resistivity and enhancing antistatic effectiveness.

[0074] Comparative Example 9 did not use a coupling agent to modify the conductive metal particles and conductive carbon black, which reduced the interfacial bonding between the filler and PFA, enhanced the interfacial resistance, and caused the conductive component to migrate during actual use. Comparative Examples 10 and 11 did not add a coupling agent to modify the conductive metal particles and the conductive carbon black, respectively. The conductive network was missing and discontinuous, and the volume resistivity increased. Comparative Example 12 did not add both substances at the same time, and the volume resistivity increased significantly, but the tensile strength and elongation at break were improved. The PFA resin in Comparative Example 13 was not pretreated, resulting in uneven dispersion of the antistatic agent, local stress concentration, and brittle fracture. Comparative Example 14 did not pre-mix the filler, resulting in reduced continuity and bonding with the PFA resin. Comparative Example 15 did not add an antistatic agent, perfluoropolyether, and fluorinated imidazolium ionic liquid, resulting in reduced antistatic effect and interfacial compatibility. Comparative Example 16, due to low-temperature extrusion, the PFA was not fully melted, the molecular chains were not fully extended, and the crystallinity was reduced. Comparative Example 17 was not surface treated, and surface defects caused crack propagation, decreased ductility, and decreased mechanical properties and antistatic effects.

[0075] Experimental Example 4

[0076] The antistatic PFA tubes obtained in Example 3, Example 9, Comparative Example 6, Comparative Example 7, and Comparative Examples 9-14 were subjected to high temperature aging at 200°C for 100 h, and then the volume resistivity was tested again. The volume resistivity was ≤1×10 7 The results of Ω·cm meet the requirements, as shown in Table 6.

[0077] Table 6 Volume resistivity after thermal aging

[0078]

[0079]

[0080] The antistatic PFA tube prepared by the present invention meets the required volume resistivity before and after thermal aging, demonstrating excellent antistatic performance. Under the conditions of Examples 3 and 9, the volume resistivity increased slightly after thermal aging. The coupling agent-modified Fe₃O₄ / Al₂O₃ particles form chemical bonds with the carbon black, resulting in strong interfacial bonding at high temperatures and no significant disruption of the conductive network. The PFA matrix exhibits excellent heat resistance, and the antioxidant Irganox 1010 inhibits thermal oxidative degradation, maintaining the integrity of the molecular chain structure. The resistance only increases slightly due to minor filler oxidation. The volume resistivity of Comparative Example 6 after thermal aging does not meet the required volume resistivity. Direct heating from room temperature results in insufficient precursor hydrolysis, resulting in a significant retention of mesopores after calcination and partial closure of these pores at high temperatures, thus reducing antistatic performance. Rapid cooling at 30°C / min after calcination in Comparative Example 7 leads to microcracks in the particles, which are further expanded by high-temperature aging, resulting in a decrease in the conductive network's scission performance. Comparative Example 9, which does not use a coupling agent for modification, shows an increase in volume resistivity after thermal aging. In Comparative Examples 10-12, omitting one of the modified conductive fillers resulted in a significant increase in volume resistivity after thermal aging, particularly when neither filler was added, significantly reducing the antistatic effect. In Comparative Example 13, local antistatic agent migration accelerated phase separation at high temperatures, leading to increased resistance. In Comparative Example 14, PFA was not fully melted, resulting in incomplete molecular chain extension. Crystallized regions were destroyed at high temperatures, exposing the filler to oxidation.

[0081] Experimental Example 4

[0082] The antistatic PFA tubes obtained in Example 3, Example 9, Comparative Example 6, Comparative Example 7, Comparative Example 9, Comparative Example 13 and Comparative Example 14 were subjected to element migration tests, wherein the migration tests of iron, aluminum and fluoride ions were conducted. The test results are shown in Table 7. The qualified migration amounts of iron, aluminum and fluoride ions were ≤5 μg / m 2 , 5μg / m 2 and 20,000 μg / m 2 ; represents the μg content of elements migrated per square meter of PFA tube. The results are shown in Table 7 and Figure 2 shown.

[0083] Table 7 Element migration test results

[0084] Group Eligibility Example 3 All standards met Example 9 All standards met Comparative Example 6 Iron and fluorine exceed the standard Comparative Example 7 Iron and fluorine exceed the standard Comparative Example 9 All exceeded the standard Comparative Example 13 Iron and fluorine exceed the standard Comparative Example 14 Iron and fluorine exceed the standard

[0085] As shown in Table 7 and Figure 2As shown, under the conditions of Examples 3 and 9 of the present invention, the element migration amounts are all qualified. While maintaining a good antistatic effect, the element migration amount is low and will not affect the substances added to the PFA tube. The coupling agent forms a chemical bond on the filler surface, inhibiting the dissolution of metal ions. The coupling agent-modified conductive metal particles and the coupling agent-modified carbon black are uniformly dispersed in the PFA matrix, reducing interface defects and ion migration channels. The antioxidant inhibits high-temperature degradation, and the above conditions work together to make the fluorocarbon chain structure complete and the fluoride ion release less. Comparative Example 6 Direct heating at room temperature leads to insufficient hydrolysis, uneven precursor particles, loose pore structure after calcination, and easy dissolution of iron ions. Low-temperature extrusion leads to insufficient PFA melting, and local crystallization defects increase fluoride ion release. Comparative Example 7 Rapid cooling leads to microcracks in the particles, rapid cooling leads to cracking on the filler surface, and aggravated iron ion migration; surface cracks accelerate PFA chain breakage and increase fluoride ion migration. In Comparative Example 9, the unmodified iron and aluminum particles resulted in poor interfacial bonding, significant iron and aluminum migration, and unmodified carbon black adsorbed moisture, promoting PFA hydrolysis and increasing fluoride ion migration. In Comparative Example 13, the antistatic agent was not premixed, leading to antistatic agent migration and localized antistatic agent accumulation, which triggered PFA phase separation and exceeded the specified fluoride ion release. In Comparative Example 14, the lack of premixed filler resulted in uneven filler dispersion, conductive particle aggregation, and interfacial stress concentration. Fluoride ion and iron migration exceeded the specified limit, and aluminum migration increased slightly compared to Example 3, but still met the migration requirements.

[0086] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an antistatic PFA tube, characterized in that: The preparation method is as follows: 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix and 0.7-1.5 parts of fluorinated imidazolium ionic liquid are mixed, extruded through a twin-screw extruder at 270-300° C. in zone I, 310-320° C. in zone II, 325-335° C. in zone III and 315-330° C. in the die, cooled, stretched and treated with mixed gas to obtain the antistatic PFA tube; The pretreated PFA resin is obtained by premixing PFA resin and antistatic agent; The premix is obtained by mixing 7.5-9 parts of coupling agent-modified conductive metal particles, 1.5-3 parts of coupling agent-modified conductive carbon black, and 0.5-1.2 parts of perfluoropolyether.

2. The method for preparing an antistatic PFA tube according to claim 1, wherein: The mass mixing ratio of the PFA resin to the antistatic agent is 150:0.3-0.

8.

3. The method for preparing an antistatic PFA tube according to claim 1, wherein: The flow rate of the mixed gas treatment is 50-80 sccm.

4. The method for preparing an antistatic PFA tube according to claim 1, wherein: The coupling agent modified conductive metal particles are obtained by immersing the conductive metal particles in a coupling agent ethanol solution; the coupling agent modified conductive carbon black is obtained by immersing the conductive carbon black in the coupling agent ethanol solution; the coupling agent is γ-methacryloxypropyltrimethoxysilane.

5. The method for preparing an antistatic PFA tube according to claim 4, characterized in that: The conductive metal particles are prepared by dissolving ligand 1 and ligand 2 in deionized water, adding urea, stirring at 55-65°C, heating to 85-95°C, and heating for 7-9.5 hours to perform a uniform precipitation reaction. The obtained precipitate is washed and dried, calcined at 450-600°C, cooled at 5-10°C / min, and kept warm and cooled to obtain the conductive metal particles.

6. The method for preparing an antistatic PFA tube according to claim 5, characterized in that: The first ligand is one of ferric nitrate, silver nitrate and copper nitrate; the second ligand is aluminum nitrate; and the molar mass ratio of the first ligand, the second ligand and the urea is 1:0.10-0.25:1.5-4 mol.

7. An antistatic PFA tube obtained by the preparation method according to any one of claims 1 to 6, characterized in that: The raw materials for preparing the antistatic PFA tube include: 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix and 0.7-1.5 parts of fluorinated imidazolium ionic liquid; the premix includes coupling agent-modified conductive metal particles; the raw materials for preparing the coupling agent-modified conductive metal particles are coupling agent and conductive metal particles; the average particle size of the conductive metal particles is 290-500nm.

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