Anti-static PFA pipe and preparation method thereof

Abstract

The present application relates to the technical field of polytetrafluoroethylene, in particular to an anti-static PFA pipe and a preparation method thereof. The present application overcomes the problem that PFA cannot simultaneously have anti-static effect and mechanical properties. In terms of improving anti-static performance, the preparation process and composite formula of conductive metal particles are optimized to construct a conductive network through urea hydrolysis and parameter control, combined with anti-static agent premixing and surface modification to reduce volume resistivity and prevent static electricity accumulation; in terms of mechanical properties, the compatibility of the filler is enhanced by modifying the filler with a coupling agent, the dispersion of the filler and the orientation of the molecular chain are promoted by adjusting the extruder process, and the molecular chain is inhibited from excessive crosslinking by introducing a compatibilizer to significantly improve the tensile strength and elongation at break; in terms of element migration control, the release of metal and fluoride ions is inhibited by optimizing raw materials and improving the process with the synergistic effect of coupling agents and antioxidants. Through the above technical means, the anti-static PFA pipe has excellent anti-static performance, mechanical strength and safety.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polytetrafluoroethylene, in particular to an anti-static PFA pipe and a preparation method thereof. BACKGROUND

[0002] PFA (perfluoroalkoxy alkoxy) pipes are widely used in chemical industry, semiconductor manufacturing, pharmaceutical industry and other fields due to their excellent chemical stability, corrosion resistance, high temperature resistance and good processing performance. However, a prominent problem of existing PFA pipes in actual use is that static electricity is easily generated. In the semiconductor manufacturing, pharmaceutical and other industries sensitive to static electricity, the static electricity generated by the PFA pipe may attract dust and impurities, affecting product quality; static discharge may also damage electronic components, cause production equipment failure, and even cause fire, explosion and other serious safety accidents. In addition, the traditional PFA pipe has limited improvement measures in terms of anti-static performance, such as simply adding anti-static agents, which can reduce static electricity generation to a certain extent, but will affect the chemical stability and mechanical properties of the PFA pipe. In addition, when the chemical raw materials are heated at high temperature, the volume resistivity of the PFA pipe increases with the increase of temperature, and the anti-static effect becomes poor, thereby affecting the progress of the chemical reaction process; at the same time, the added anti-static inorganic materials have poor compatibility with the PFA pipe, which is easy to precipitate during high temperature and repeated use, thereby causing cracks in the PFA pipe and reducing its durability. In summary, the PFA pipe of the prior art cannot meet the demand for comprehensive performance of the PFA pipe in specific application scenarios.

[0003] Therefore, it is urgent to develop a technical solution that can effectively solve the static electricity problem of the PFA pipe while taking into account the mechanical properties and safety of the PFA pipe, which is also an important direction for the improvement of the PFA pipe technology. Therefore, an anti-static PFA pipe and a preparation method thereof are proposed. SUMMARY

[0004] The present application aims to provide an antistatic PFA pipe and a preparation method thereof. In terms of antistatic performance, a uniform alkaline environment is constructed by urea slow-release hydrolysis, and the reaction of metal salt and ligand is precisely controlled to generate iron-aluminum-oxygen composite conductive particles. Antistatic agent premixing and fluorinated imidazole ionic liquid are combined to inhibit molecular chain crosslinking, and an ion conductive layer is formed by plasma surface treatment to construct a continuous conductive network, effectively reducing volume resistivity and preventing static electricity accumulation. In terms of mechanical performance, the surface of the conductive filler is modified by a coupling agent to enhance the interfacial bonding force between the conductive filler and the PFA matrix. High-temperature shearing and bidirectional stretching directional arrangement of the twin-screw extrusion process are combined to optimize molecular chain orientation. At the same time, a perfluoropolyether compatibilizer is introduced to improve the interfacial strength, so that the pipe has high tensile strength and excellent ductility. In terms of safety, the chemical bonding of the coupling agent inhibits the dissolution of metal ions, and the antioxidant maintains the stability of the fluorocarbon chain. The pore structure and dispersion process are optimized to significantly reduce the migration of fluorine ions and metal elements, ensuring that the material meets the safety threshold during long-term use. Through systematic innovation of the process and formula, the antistatic performance, mechanical strength, and environmental safety of the PFA pipe are synergistically improved.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] The present application provides a preparation method of an antistatic PFA pipe, and the preparation method is as follows:

[0007] Mix 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix, and 0.7-1.5 parts of fluorinated imidazole ionic liquid, and extrude them through a twin-screw extruder with I zone 270-300℃, II zone 310-320℃, III zone 325-335℃, and die head 315-330℃, and then cool, stretch, and treat with mixed gas to obtain an antistatic PFA pipe;

[0008] The stretching conditions are as follows: preheat the antistatic PFA pipe precursor to 280℃, and perform bidirectional stretching at a speed of 1 m / min, with a longitudinal / transverse stretching 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 pipe after stretching is <5%. The screw rotation speed during extrusion is 80 r / min, and the melt pressure is 8-10 MPa;

[0009] The mixed gas is obtained by mixing argon and oxygen at 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 the coupling agent modified conductive metal particles, 1.5-3 parts of the coupling agent modified conductive carbon black, and 0.5-1.2 parts of the perfluoropolyether; the average particle size of the conductive carbon black used in the coupling agent modified conductive carbon black is 200 nm.

[0012] Preferably, the mass mixing ratio of the PFA resin and 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-methacryloyloxypropyltrimethoxysilane.

[0015] Preferably, the conductive metal particles are obtained by dissolving the ligand one and the ligand two in deionized water, adding urea, stirring at 55-65 DEG C, then heating to 85-95 DEG C, and performing uniform precipitation reaction for 7-9.5 h, washing and drying the obtained precipitate, then calcining at 450-600 DEG C, cooling at a rate of 5-10 DEG C / min, and then keeping warm and cooling to obtain the conductive metal particles.

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

[0017] The application also provides an antistatic PFA pipe prepared by any one of the preparation methods.

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

[0019] 1. By optimizing the conductive metal particle preparation process and the PFA pipe composite formula, the antistatic performance is significantly improved. The uniform alkaline environment is constructed by slow hydrolysis of urea, the metal salt, the ligand, and the reaction conditions are precisely controlled, the iron-aluminum-oxygen composite particles with appropriate particle size and specific surface area are generated, and a continuous conductive network is formed. At the same time, the antistatic agent is premixed, the fluorinated imidazole ionic liquid inhibits the crosslinking of molecular chains, and the surface of the pipe is modified by the mixed gas to promote the formation of the ion conductive layer. The multiple technologies work together to effectively reduce the volume resistivity of the PFA pipe, prevent static accumulation, and make the product have reliable antistatic ability.

[0020] 2, The surface of the conductive filler is modified by a coupling agent to form a chemical bond connection, enhance the compatibility of the filler with the PFA resin, and reduce interface defects; the temperature and shear force of the twin-screw extruder are controlled to ensure uniform dispersion of the filler, and the longitudinal and transverse stretching ratios are set to promote the ordered orientation of molecular chains; in addition, a perfluoropolyether compatibilizer is introduced to strengthen the interface bonding and inhibit excessive crosslinking of PFA molecular chains; the above conditions are synergistically improved to improve the tensile strength and elongation at break of the PFA pipe, and the product has excellent toughness and deformation resistance.

[0021] 3, Low element migration is achieved by dual optimization of raw materials and process. The coupling agent forms a stable barrier on the surface of the filler, effectively inhibiting the dissolution of metal ions; combined with antioxidants to inhibit high-temperature degradation and maintain the integrity of the fluorocarbon chain structure, reducing the release of fluoride ions; at the same time, the preparation method of conductive metal particles is optimized to improve the compatibility with the resin matrix, avoiding ion migration caused by pore structure defects or material agglomeration. By precisely controlling the parameters at each stage, the PFA pipe maintains good antistatic properties while the element migration is far below the safety threshold, providing high safety and reliability. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flow chart of the preparation method of the anti-static PFA pipe of the present application;

[0023] Figure 2 The element migration result graph of the anti-static PFA pipe of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] Please refer to Figures 1 to 2 The present application provides an anti-static PFA pipe and a preparation method thereof, and the technical solutions are as follows:

[0026] Iron 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; Gamma-methacryloxypropyltrimethoxysilane (KH570) CAS: 2530-85-0; Fluorinated imidazolium ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) CAS: 174899-82-2; Irganox 1010 CAS: 6683-19-8; Antistatic agent purchased from Kano Trade (Shanghai) Co., Ltd., brand MV2080.

[0027] It should be noted that the parts of the present application are mass parts; the room temperature mentioned is 25°C.

[0028] Example 1

[0029] The preparation method of the conductive metal particles is as follows: 1 mol of iron 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 min, then heated to 95°C at a rate of 2°C / min, and heated for 8 h for uniform precipitation reaction, and the obtained precipitate is washed with ethanol and deionized water for 3 times respectively, and placed in an oven for drying, dried at 120°C for 4 h, to obtain a conductive metal particle intermediate; transferred to a muffle furnace, calcined at 500°C for 3 h, cooled to 80°C at a rate of 5°C / min, and kept at 80°C for 2 h to cool to room temperature naturally, to obtain the conductive metal particles.

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

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

[0032] 0.5 parts of antistatic agent was premixed with 150 parts of PFA resin, dried at 60°C for 2h 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 min 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 into a high-speed mixer, mixed at 800 r / min for 10 min to ensure uniform dispersion to obtain a mixture; the mixture was transferred into a twin-screw extruder with an L / D value of 52, and the temperatures set in different zones were as follows: 300°C in zone I, 320°C in zone II, 330°C in zone III, and 325°C at the die head; after extrusion, water cooling was performed at 15°C to obtain an antistatic PFA tube precursor.

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

[0034] The overall preparation method of Examples 2-5 was the same as that of Example 1, but the method of preparing the conductive metal particles was changed, as shown in Table 1. Among them, the mixed metal solution contained ligand one and ligand two, and ligand two was aluminum nitrate; temperature one was the reaction temperature after adding urea, and temperature two was the heating temperature.

[0035] Table 1 Preparation conditions of conductive metal particles

[0036]

[0037] Comparative Examples 1-8 had the same preparation method as Example 1 except for the differences listed below.

[0038] Comparative Example 1 only added 0.25 mol of aluminum nitrate without adding iron nitrate.

[0039] Comparative Example 2 only added 0.25 mol of iron nitrate without adding aluminum nitrate.

[0040] Comparative Example 3 replaced urea with an equimolar amount of sodium hydroxide.

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

[0042] Comparative Example 5 mixed aluminum nitrate, iron nitrate and urea at the same time.

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

[0044] The cooling rate of the calcined Comparative Example 7 is 30℃ / min.

[0045] Comparative Example 8 is directly cooled to room temperature at 5℃ / min after calcination.

[0046] Experimental Example 1

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

[0048] Table 2 Test results of particle size and specific surface area

[0049]

[0050] The conductive metal particles prepared by the present application have an average particle size of 290-500nm and a specific surface area of 1.50-2.20m 2 2 / g under the conditions of Examples 1-5. 1 Under the conditions of Example 1, urea slowly hydrolyzes to generate NH3 and CO2 at a high temperature of 95℃, NH3 further hydrolyzes to NH4+ and OH-, and CO2 generates CO3 2 - to form a uniform alkaline environment, Fe 3 + and Al 3 + react with OH- and CO3 2 - to generate an alkaline carbonate precursor (Fe / Al-CO3-OH complex), the slow hydrolysis of urea avoids local supersaturation, making the size of the precipitated particles uniform; after high-temperature calcination, the precursor decomposes into a Fe-Al oxide, specifically a complex of Fe3O4 and Al2O3, CO2 and H2O are released during calcination, forming a mesoporous structure, slowly cooling at a suitable cooling rate, and holding for a certain period of time after cooling, thereby reducing thermal stress and preserving the pore structure; Examples 2-5 adjust the type of ligand one, the amount of ligand two 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 increase, 10℃ / min rapid cooling pore part collapse, specific surface area decreases; Example 3 calcination temperature is increased to 550℃, promotes part of the pore closure, but the particle size is small, the particle sintering is slight, the specific surface area is slightly reduced; Example 4 silver nitrate is replaced by ferric nitrate, Ag+ is reduced to generate metal silver, Ag particles are easy to agglomerate, and the particle coarsening; the specific surface area is the lowest after low-temperature calcination; Example 5 copper nitrate is too high calcination temperature, which leads to CuO grain coarsening, and pore collapse. Comparative Example 1 only Al 3 + precipitated Al2O3 agglomerates, dense structure, low specific surface area; Comparative Example 2 only Fe 3 + Fe2O3 large particles are generated, the particles are dense and have no pores, and the specific surface area is reduced; NaOH rapid precipitation of Comparative Example 3 leads to micron-level blocks, few pores, and low specific surface area; Comparative Example 4 ammonia water local pH wave generates coarse particles, pore distribution is uneven, and the specific surface area is slightly higher than that of Comparative Example 3; Comparative Example 5, urea and metal salt are not mixed fully, the particle size is uneven, and part of the micropore is left; Comparative Example 6, direct heating at room temperature leads to insufficient hydrolysis, the particle size is slightly small, and a small amount of mesopore is left; Comparative Example 7, rapid cooling leads to particle microcracks, but the pores are not effectively preserved, and the specific surface area is medium; Comparative Example 8, direct cooling to room temperature at a fixed rate, without holding, leads to particle internal pore collapse, particle agglomeration and coarsening due to thermal stress, and the specific surface area is significantly reduced.

[0051] Experimental Example 2

[0052] The antistatic PFA pipes obtained in the above examples and comparative examples are tested for volume resistivity, and the volume resistivity is ≤1×10 7 Ω·cm, which meets the requirements, and the test results are shown in Table 3.

[0053] Table 3 Volume resistivity test results

[0054]

[0055] The antistatic PFA pipes prepared by the present application have a volume resistivity of 2.75×10 6 to 5.89×10 6Ω·cm. By adjusting the preparation method of the conductive metal particles, the conductive metal particles have appropriate particle size and specific surface area, so that the PFA pipe has low volume resistivity, thereby improving the 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 material type of the ligand is replaced from iron nitrate to silver nitrate, the stirring temperature, the temperature rising temperature and the calcination conditions are adjusted, so that the volume resistivity is the lowest, and the static electricity is not easy to accumulate in the PFA pipe; under the conditions of example 5, the preparation method is adjusted, so that the PFA pipe also has good antistatic effect; although the volume resistivity of examples 4 and 5 is relatively small, considering the use cost problem, the conditions of examples 1-3 are selected for subsequent experiments. Overall, the conductive metal particles prepared in examples 1-5 have appropriate particle size and specific surface area, which improves the conductive effect of the PFA pipe and enhances the antistatic ability. In comparative example 1, only aluminum nitrate is added, only insulator Al2O3 is generated, there is no conductive phase, the resistance is greatly improved, and the antistatic effect is poor. In comparative example 2, only semiconductor Fe2O3 is formed, the conductivity is weaker than Fe3O4, the resistance is relatively high but still lower than that of comparative example 1. In comparative example 3, large particles of Fe2O3 are quickly precipitated under the action of NaOH, the conductive network is discontinuous, and the resistance is the highest. In comparative example 4, the use of ammonia water precipitates particles unevenly, which further causes the imbalance of the iron-aluminum ratio, the conductive network is sparse, and the volume resistivity is increased. In comparative example 5, the metal salt mixture is uneven, the conductive network is locally missing, but a small amount of Fe3O4 phase is left, and the volume resistivity is higher than that of example 1. In comparative example 6, after adding urea, no heating and stirring are performed, but the temperature is directly increased from room temperature to 95℃ at a speed of 2℃ / min, the conductive particles are small and residual mesoporous, the conductive network is relatively optimal, and the resistance is close to that of example 1. In comparative example 7, rapid cooling leads to microcracks, but part of the pores are preserved, and the resistance is moderate. In comparative example 8, no heat preservation leads to particle agglomeration, the conductive network is damaged, and the resistance is significantly increased. In summary, the conductive metal particles prepared by the present application have high specific surface area and appropriate average particle size, the density and continuity of the conductive network are regulated, the electronic transmission path is optimized, the specific calcination and cooling parameters of the preparation method are adjusted, the particle morphology is changed to further strengthen the electronic transmission, and the PFA pipe has good antistatic effect.

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

[0057] Table 4 Raw material mixing and conditions

[0058]

[0059] Comparative Examples 9-17 are the same as Example 3 except for the differences listed below.

[0060] Comparative Example 9 does not use a coupling agent to modify the conductive metal particles; and does not use a coupling agent to modify the conductive carbon black.

[0061] Comparative Example 10 does not add a coupling agent to modify the conductive metal particles.

[0062] Comparative Example 11 does not add a coupling agent to modify the conductive carbon black.

[0063] Comparative Example 12 does not add a coupling agent to modify the conductive metal particles and a coupling agent to modify the conductive metal particles.

[0064] Comparative Example 13 does not pre-treat the PFA resin, i.e., the antistatic agent is added at the end when mixing the PFA resin.

[0065] Comparative Example 14 does not pre-mix the coupling agent to modify the conductive metal particles, the coupling agent to modify the conductive carbon black, and the perfluoropolyether.

[0066] Comparative Example 15 does not add the antistatic agent, the perfluoropolyether, and the fluorinated imidazole ionic liquid.

[0067] Comparative Example 16 uses a three-zone and die head temperature of the twin-screw extruder of 250, 290, 310, and 300°C, respectively.

[0068] Comparative Example 17 does not use a mixed gas for surface treatment.

[0069] Experimental Example 3

[0070] The PFA pipes obtained from Example 3, Examples 6-9, and Comparative Examples 9-17 are tested for volume resistivity and mechanical properties; the volume resistivity is tested according to the test method of Experimental Example 2; the mechanical properties are mainly tested for tensile strength and elongation at break according to GB / T 2567-2021, and the results of the tensile strength are ≥1.5 MPa, which meets the requirements, and the results of the elongation at break are ≥20%, which meets the requirements. The test results are shown in Table 5.

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

[0072]

[0073] The antistatic PFA pipe prepared by the present application has a volume resistivity of 4.57 x 10 6 -6.25 x 10 6Ω·cm, the tensile strength is 27.5-31.1 MPa, and the elongation at break is 280%-345%. The conductive metal particles and the conductive carbon black are modified using a coupling agent, respectively. The coupling agent is hydrolyzed on the surface of the filler to form silicon hydroxyl groups, which are then chemically bonded to the active hydroxyl groups on the surface of the conductive metal particles, thereby improving the compatibility of the conductive metal particles and the conductive carbon black with the PFA resin and improving the mechanical properties of the final PFA pipe. The modified filler is uniformly dispersed, reducing defects in the conductive network. By premixing the antistatic agent with the PFA, the antistatic performance is enhanced. The antistatic agent and the fluorinated imidazole ionic liquid inhibit the excessive crosslinking of the PFA molecular chain, maintaining the material toughness. At the same time, the perfluoropolyether acts as a compatibilizer, with its fluorocarbon segment co-crystallizing with the PFA and the carboxylic acid group bonding with the filler, further improving the interfacial strength. The temperature in different zones of the twin-screw extruder is adjusted, and suitable high temperature and high shear force ensure uniform dispersion of the filler. The longitudinal / transverse tensile ratio is 2:1, which helps to improve the molecular chain orientation and mechanical strength. The surface of the PFA pipe is treated with a mixed gas to generate active free radicals under vacuum, forming surface polar groups that adsorb moisture to form an ionic conductive layer, reducing the volume resistivity and improving the antistatic effect.

[0074] Comparative Example 9 does not use a coupling agent to modify the conductive metal particles and the conductive carbon black, reducing the interfacial bonding between the filler and the PFA, increasing the interfacial resistance, and causing the conductive components to migrate during actual use. Comparative Examples 10 and 11 do not add a coupling agent to modify the conductive metal particles and a coupling agent to modify the conductive carbon black, respectively, resulting in a discontinuous conductive network and an increase in volume resistivity. Comparative Example 12 does not add both substances, resulting in a significant increase in volume resistivity but an increase in tensile strength and elongation at break. The PFA resin in Comparative Example 13 is not pretreated, and the antistatic agent is not uniformly dispersed, leading to brittle fracture due to local stress concentration. Comparative Example 14 does not perform premixing, resulting in a decrease in the continuity of the filler and the bonding force with the PFA resin. Comparative Example 15 does not add an antistatic agent, a perfluoropolyether, and a fluorinated imidazole ionic liquid, resulting in a decrease in antistatic effect and interfacial compatibility. Comparative Example 16 is extruded at a low temperature, causing the PFA to melt insufficiently, the molecular chain to not stretch sufficiently, and the crystallinity to decrease. Comparative Example 17 is not surface treated, and surface defects cause crack propagation, resulting in a decrease in ductility, mechanical properties, and antistatic effect.

[0075] Experimental Example 4

[0076] The antistatic PFA pipes obtained in Example 3, Example 9, Comparative Example 6, Comparative Example 7, and Comparative Examples 9-14 were aged at a high temperature for 100 h at 200℃, and the volume resistivity was tested again. The volume resistivity was ≤1×10 7 Ω·cm, and the results are shown in Table 6.

[0077] Table 6 Volume resistivity after heat aging

[0078]

[0079]

[0080] The anti-static PFA pipe prepared by the present application has a volume resistivity meeting the requirements before and after heat aging, and has good anti-static effect. Under the conditions of Example 3 and Example 9, the volume resistivity slightly increases after heat aging, the coupling agent modified Fe3O4 / Al2O3 particles form chemical bonding with carbon black, the interface bonding force is strong at high temperature, and the conductive network is not significantly damaged; the PFA matrix has good heat resistance, the antioxidant Irganox 1010 inhibits thermal oxidative degradation, the molecular chain structure remains intact, and the resistance only slightly increases due to slight oxidation of the filler. The volume resistivity of Comparative Example 6 after heat aging does not meet the requirements, direct heating at room temperature leads to insufficient hydrolysis of the precursor, and after calcination, more mesopores are retained, and at high temperature, some pores are closed, thereby reducing the anti-static performance. The volume resistivity of Comparative Example 7 after calcination at 30℃ / min rapidly decreases, the particles have micro-cracks, the cracks are further expanded at high temperature aging, and the conductive network is broken. The volume resistivity of Comparative Example 9 increases after heat aging without using a coupling agent for modification. Comparative Examples 10-12 do not add one of the modified conductive fillers, which will cause the volume resistivity to significantly increase after heat aging, especially when neither of the two fillers is added, the anti-static effect is greatly reduced. In Comparative Example 13, the partial anti-static agent migrates, high temperature accelerates phase separation, and the resistance increases. In Comparative Example 14, the PFA does not melt sufficiently, the molecular chain is not fully stretched, the crystalline region is damaged at high temperature, and the filler is exposed to oxidation.

[0081] Experimental Example 4

[0082] Element migration tests were performed on the anti-static PFA pipes obtained from Example 3, Example 9, Comparative Example 6, Comparative Example 7, Comparative Example 9, Comparative Example 13 and Comparative Example 14, in which iron element, aluminum element and fluorine ion migration tests were performed, and the test results are shown in Table 7. The qualified migration amounts of the iron element, the aluminum element and the fluorine ion are ≤5 μg / m 2 , 5 μg / m 2 and 20000 μg / m 2 , respectively, indicating the μg content of the elements migrated per square meter of the PFA pipe. The results are shown in Table 7 and Figure 2 .

[0083] Table 7 Element Migration Test Results

[0084] Group Eligibility Example 3 All met the criteria Example 9 All met the criteria Comparative Example 6 Iron, fluorine exceeded the criteria Comparative Example 7 Iron, fluorine exceeded the criteria Comparative Example 9 All exceeded the criteria Comparative Example 13 Iron, fluorine exceeded the criteria Comparative Example 14 Iron, fluorine exceeded the criteria

[0085] As shown in Table 7 and Figure 2As shown, under the conditions of Example 3 and Example 9 of the present application, the element migration amount is all qualified, the element migration amount is low under the condition of maintaining good antistatic effect, and will not affect the substances added in the PFA tube; the coupling agent forms a chemical bond on the surface of the filler, inhibits the dissolution of metal ions, the coupling agent modifies the conductive metal particles and the coupling agent modifies the carbon black uniformly dispersed in the PFA matrix, reduces the interface defects and ion migration channels; and the antioxidant inhibits high temperature degradation, which cooperates with the above conditions to make the fluorocarbon chain structure complete and the fluorine ion release less. Comparative Example 6 directly heats at room temperature, which 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 increased local crystalline defects increase fluorine ion release. Comparative Example 7 rapid cooling leads to particle microcracks, rapid cooling leads to filler surface cracking, and iron ion migration is intensified; surface cracks accelerate PFA chain rupture, and fluorine ion migration increases. The iron and aluminum particles in Comparative Example 9 are not modified, the interface bonding is poor, iron and aluminum migration is significant, and in addition, unmodified carbon black adsorbs moisture, promotes PFA hydrolysis, and increases fluorine ion migration. Comparative Example 13 does not pre-mix the antistatic agent, the antistatic agent migrates, the local antistatic agent is enriched, which causes PFA phase separation, and the fluorine ion release amount exceeds the standard. The non-pre-mixed filler in Comparative Example 14 leads to uneven dispersion of the filler, and the aggregation of conductive particles leads to interface stress concentration, the fluorine ion and iron element migration amount exceeds the standard, and the aluminum migration amount is higher than that of Example 3, but still meets the migration requirements.

[0086] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of making an antistatic PFA tube, characterized by: The preparation method is as follows: The anti-static PFA pipe is prepared by mixing 150.3-150.8 parts of pretreated PFA resin, 9.5-13.1 parts of premix and 0.7-1.5 parts of fluorinated imidazole ionic liquid, extruding through a double screw extruder with I zone 270-300℃, II zone 310-320℃, III zone 325-335℃ and die head 315-330℃, cooling, stretching and mixing gas treatment; the mixing gas is obtained by mixing argon and oxygen at a volume ratio of 8:2; 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; the coupling agent modified conductive metal particles are obtained by immersing conductive metal particles in a coupling agent ethanol solution; the coupling agent modified conductive carbon black is obtained by immersing conductive carbon black in the coupling agent ethanol solution; the coupling agent is γ-methacryloyloxypropyltrimethoxysilane; The conductive metal particles are obtained by dissolving ligand one and ligand two in deionized water, adding urea, stirring at 55-65℃, then heating to 85-95℃, and performing uniform precipitation reaction for 7-9.5h, washing and drying the obtained precipitate, calcining at 450-600℃, then cooling at a rate of 5-10℃ / min, and keeping and cooling to obtain the conductive metal particles; The ligand one is one of ferric nitrate, silver nitrate and copper nitrate; the ligand two is aluminum nitrate; the molar mass ratio of the ligand one, the ligand two and the urea is 1:0.10-0.25:1.5-4mol.

2. The method of claim 1, wherein: The mass mixing ratio of the PFA resin and the antistatic agent is 150:0.3-0.

8.

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

4. The anti-static PFA tube according to any one of claims 1 to 3, wherein: The preparation raw materials of the anti-static PFA pipe 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 imidazole ionic liquid; the premix includes coupling agent modified conductive metal particles; the preparation raw materials of 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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