PTFE Tube Continuous Etching Equipment, Continuous Etching Method

Abstract

The present invention discloses a PTFE tube continuous etching device and a continuous etching method, which relate to the field of surface treatment equipment for plastic pipes. The key technical points of its technical solution are as follows: it includes a conveying mechanism, an etching tank, a multi-stage sealing structure arranged at both ends of the inlet and outlet of the etching tank, a neutralization and cleaning unit, a drying unit, a tail gas treatment unit, and a control system. The etching tank is filled with a sodium-naphthalene etching solution, and an inert gas is introduced to maintain a positive pressure environment; the sealing structure includes at least three levels of sealing units arranged in series, and the gas chamber pressures of each level are positive pressure, neutral pressure, and negative pressure from inside to outside in sequence, effectively achieving the barrier of poisonous gas and isolating it from the outside. This device can significantly reduce the risk of leakage of poisonous gas during the etching process while realizing the continuous transportation of PTFE tubes, and improve the operation safety and process stability.

Description

Technical Field

[0001] The present invention relates to the field of surface treatment equipment for plastic pipes, and particularly to a PTFE pipe continuous etching device and a continuous etching method. Background Art

[0002] Due to its excellent chemical inertness and corrosion resistance, polytetrafluoroethylene (PTFE) is widely used as a sealing, insulating, and fluid transportation material in the fields of chemical engineering, electronics, medicine, etc. In order to improve the adhesion and activity of the PTFE surface, sodium-naphthalene complex solution is often used to chemically etch its surface in the prior art. This etching solution has extremely strong corrosiveness and forms a carbonized layer with rich active groups on the PTFE surface through defluorination, significantly improving the subsequent coating or bonding performance.

[0003] However, the sodium-naphthalene solution is extremely easy to react with oxygen or water during the preparation and use process: on the one hand, sodium metal will undergo a violent exothermic reaction when encountering water; on the other hand, the sodium-naphthalene complex will be rapidly oxidized and inactivated when encountering oxygen, resulting in unstable etching effects. At the same time, if the toxic gas generated during the etching process leaks, it poses a serious threat to the operating environment and personnel safety. For this reason, existing etching devices usually adopt a closed tank body and continuously introduce nitrogen to establish an overpressure environment in the tank, using nitrogen stamping to exclude oxygen and moisture and maintain the activity and stability of the etching solution. However, during the continuous transportation of the PTFE pipe, it is difficult to achieve complete airtight sealing at its inlet and outlet. When the pressure in the tank is greater than the outside, the toxic gas leaks out along the pipe end, not only reducing the safety of the system but also increasing the complexity of subsequent waste gas treatment. Summary of the Invention

[0004] The purpose of the present invention is to provide a PTFE pipe continuous etching device, which has the advantages of significantly improving the etching safety and the sealing performance of the device.

[0005] The above technical purpose of the present invention is achieved through the following technical solutions:

[0006] A PTFE pipe continuous etching device, comprising:

[0007] A conveying mechanism for continuously conveying the PTFE pipe to be processed;

[0008] A sealing structure provided at the inlet and outlet of the etching tank. Each sealing structure includes at least three levels of sealing units arranged in sequence from the inside to the outside along the PTFE pipe conveying direction. Each sealing unit includes a channel section and an air chamber communicated therewith. The air chamber is provided with a gas input channel, a tail gas discharge port, a pressure sensor, and a control valve. The air chamber pressures of each sealing unit are set to positive pressure, neutral pressure, and negative pressure in sequence;

[0009] A neutralization and cleaning unit, a drying unit, and a tail gas treatment unit, which are sequentially connected to the rear end of the etching tank;

[0010] A control system is used to coordinate the operation of each unit and regulate the air pressure in the etching tank and the working state of the sealing structure.

[0011] Further setting: At least one stage of the sealing unit adopts a magnetorheological fluid sealing structure. The magnetorheological fluid is composed of magnetic nanoparticles suspended in a carrier liquid. A circular magnetic field is formed by a magnetic ring arranged outside the channel section, driving the magnetorheological fluid to fit the surface of the PTFE tube to form a dynamic sealing band.

[0012] Further setting: A micro magnetic array for adjusting the magnetic field distribution is arranged on the periphery of the magnetorheological fluid sealing structure. The magnetic array includes a plurality of magnet elements that can independently control the magnetic flux, and is used to dynamically adjust the sealing strength and distribution range of the magnetorheological fluid under different operating states.

[0013] Further setting: The magnetorheological fluid of the magnetorheological fluid sealing structure is composed of 5 - 15 wt% magnetic nanoparticles suspended in a carrier liquid, and the average particle size of the magnetic nanoparticles is 10 - 50 nm. The dynamic viscosity of the magnetorheological fluid at 20 °C is 50 - 200 mPa·s.

[0014] Further setting: At least one stage of the sealing unit adopts a nitrogen vortex diversion structure. The diversion structure includes a tangential air inlet hole and a spiral air guide groove. The tangential air inlet hole ejects nitrogen tangentially along the inner wall of the air chamber, and the spiral air guide groove guides the nitrogen to form an annular air curtain around the PTFE tube inside the air chamber.

[0015] Further setting: The tangential air inlet hole or the spiral air guide groove of the nitrogen vortex diversion structure is connected to a control valve through a pipeline. The control valve is controlled by the control system and is used to adjust the nitrogen flow rate in the range of 0.1 - 10 L / min to control the vortex intensity of the annular air curtain in real time.

[0016] Further setting: The third-stage sealing unit adopts an annular expansion type sealing layer. The annular expansion type sealing layer is composed of a polymer swelling material sensitive to oxygen or water vapor. The annular expansion type sealing layer expands in volume after absorbing oxygen or moisture, and then forms a fitting connection with the inner wall of the channel section of the sealing structure.

[0017] Another object of the present invention is to provide a method for continuously etching a PTFE tube. Using the above-mentioned PTFE tube continuous etching equipment, the method includes the following steps:

[0018] Transportation: The PTFE tube to be processed is transported to the etching tank at a constant speed of 0.5 - 2 m / min through a transportation mechanism.

[0019] Etching: Continuously immerse the PTFE tube in a sodium-naphthalene etching solution with a temperature of 20 - 30°C and a concentration of 5 - 10% in an etching tank. Nitrogen is introduced into the tank body to maintain a positive pressure environment. During the etching process, the PTFE tube passes through the sealing structures provided at the inlet and outlet of the etching tank successively. The sealing structures are used to block oxygen and moisture in stages, and the nitrogen flow rate is maintained at 0.1 - 10 L / min through a control valve.

[0020] Neutralization and cleaning: Pass the etched PTFE tube through a neutralization tank and a multi-stage ultrasonic cleaning tank successively to terminate the chemical reaction and remove the residual etching solution.

[0021] Drying: Dry the cleaned PTFE tube in a hot air drying unit at 80 - 120°C.

[0022] Tail gas treatment: Uniformly introduce the tail gases from all the sealing structures and the etching tank into a tail gas treatment unit. After treatment by activated carbon adsorption, pickling, or a condensation phase transfer adsorption layer, the tail gases are discharged up to the standard.

[0023] In summary, the present invention has the following beneficial effects:

[0024] In the present invention, by respectively arranging sealing structures at the inlet and outlet ends of the etching tank, and using a series arrangement of multiple air chambers with a gradual transition of air pressure, without affecting the continuous transportation of the PTFE tube, the leakage of toxic gases is greatly reduced, and at the same time, the entry of oxygen or moisture is prevented. There is an air chamber between each stage of the sealing unit of the sealing structure. The outermost first-stage sealing unit maintains a slightly negative pressure slightly lower than the atmospheric pressure for sucking in the leaked toxic gas; the second-stage sealing unit maintains a neutral or slightly positive pressure; the third-stage sealing unit closest to the etching tank maintains a positive pressure higher than the pressure in the etching tank to ensure that the gas in the tank cannot leak outwards. Through layer-by-layer isolation and multiple safeguards, the sealing level is improved to achieve a dynamic transition.

[0025] Second, in the present invention, at least one stage of the sealing unit adopts a magnetic fluid sealing structure. The magnetic fluid can be used to replace the flexible sealing ring and is applied to the sliding sealing section of each stage in the multi-stage channel section structure. The magnetic control seal is introduced into a continuous micro-sealing occasion, and the sealing form is adjusted in combination with air pressure feedback. The magnetic fluid sealing belt can achieve non-contact high-pressure sealing without increasing mechanical friction. Further, an adjustable micro-magnetic array is arranged outside the sealing channel to automatically adjust the magnetic field intensity and distribution according to the operating state to control the sealing state. Realize dynamic adaptive adjustment of the sealing strength; the sealing layer can be automatically tightened or loosened according to air pressure feedback.

[0026] Third, in the present invention, at least one stage of the sealing unit adopts a nitrogen vortex diversion structure. On the basis of considering the pressure difference, the air flow pattern is intervened. A diversion cavity structure with a spiral or bevel cut angle is added to each stage of the air chamber, so that when nitrogen enters, a directional vortex flow is formed instead of a straight-line flow, creating an "air curtain" effect, enhancing the barrier effect, disturbing the gas path, increasing the flow resistance of the path through which the leaked gas passes, and further blocking the diffusion of the countercurrent gas.

[0027] The nitrogen vortex diversion structure changes the flow direction and pattern of nitrogen in the sealing structure, forms a spiral vortex air flow around the channel section or in the air chamber, and establishes a positive turbulence barrier in the micro-gap, so that any reverse-leaking gas faces the vortex "reaction zone", increasing the difficulty of leakage.

[0028] Fourth, in the present invention, the third-stage sealing unit adopts an annular expansion type sealing layer, which is composed of a polymer swelling material sensitive to oxygen or water vapor. When the system loses pressure, leaks, or encounters moisture, it quickly expands to form an emergency seal to prevent the leakage of toxic gases; it can be used as a passive safety protection layer in the multi-stage channel section sealing system. Enhance the fault tolerance and emergency response ability of the system; applicable to passive protection under extreme working conditions such as power failure and control failure. Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of a PTFE tube continuous etching device;

[0030] Figure 2 is a schematic structural diagram of the sealing unit;

[0031] Figure 3 is a schematic structural diagram of the magnetohydrodynamic sealing structure;

[0032] Figure 4 is a schematic structural diagram of the nitrogen vortex diversion structure;

[0033] Figure 5 is a schematic structural diagram of the annular expansion type sealing layer.

[0034] In the figure, 100, conveying mechanism; 200, etching tank; 300, neutralization and cleaning unit; 400, drying unit; 500, tail gas treatment unit;

[0035] 600, sealing structure; 601, channel section; 602, air chamber; 603, gas input channel; 604, tail gas discharge port; 605, control valve; 606, pressure sensor;

[0036] 700, magnetohydrodynamic sealing structure; 701, magnetohydrodynamic fluid; 702, magnetic ring; 703, micro magnetic array;

[0037] 800, Nitrogen Vortex Diversion Structure; 801, Tangential Inlet Hole; 802, Spiral Gas Guide Groove; 900, Ring-shaped Expanding Sealing Layer. Detailed Embodiment

[0038] The present invention will be further described in detail below with reference to the accompanying drawings.

[0039] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0040] A PTFE tube continuous etching device, as Figure 1 and Figure 2 shown, the device is sequentially provided with a conveying mechanism 100, an etching tank 200, a neutralization and cleaning unit 300, a drying unit 400, and an exhaust gas treatment unit 500 along a predetermined transmission path, and also includes a control system for adjusting and monitoring the operating states of the above-mentioned various units.

[0041] The conveying mechanism 100 is fixedly arranged at the front end of the device and is used to continuously convey the PTFE tube to be processed to the etching tank 200 at a constant speed; the etching tank 200 is arranged behind the conveying mechanism 100 along the conveying direction, and the tank is filled with sodium-naphthalene etching solution, and an inert gas is introduced to maintain a positive pressure environment, so as to ensure the stability of the etching solution and the etching effect.

[0042] As Figure 1 and Figure 2 shown, it also includes a sealing structure 600 arranged at both the inlet and outlet ends of the etching tank 200. The sealing structure 600 is arranged on the conveying path of the PTFE tube and is located on both sides of the etching tank 200 before and after, and is used to maintain the pressure difference between the inside and outside of the etching tank 200 during the continuous passing of the PTFE tube, and effectively isolate the etching solution from the external environment to prevent gas leakage and moisture infiltration.

[0043] Each sealing structure 600 is provided with at least three - stage sealing units in sequence along the conveying direction of the PTFE tube. Each sealing unit is arranged axially in order from the etching tank 200 outwards, namely the first - stage sealing unit, the second - stage sealing unit and the third - stage sealing unit. Each sealing unit includes a cylindrical channel section 601 and an air chamber 602 communicated therewith. Each air chamber 602 is respectively provided with a gas input channel 603, an exhaust gas outlet 604, a pressure sensor 606 and a control valve 605, which are used to control the gas flow and pressure state in different sealing units. In order to form a stable pressure gradient, the working air pressure of the air chamber 602 is set as positive pressure, neutral pressure and negative pressure in sequence from the side close to the etching tank 200 outwards. That is, the air chamber 602 corresponding to the first - stage sealing unit is set as positive pressure to prevent the etching gas from leaking; the second - stage is set as neutral pressure to slow down the pressure difference impact; the third - stage is set as negative pressure to adsorb the possibly escaping gas and guide it to the exhaust gas treatment system, so as to realize the multi - stage dynamic blocking and safe transition sealing of the gas. Through the setting of the above - mentioned hierarchical sealing structure 600, even when the PTFE tube is in a continuous moving state, an efficient sealing isolation between the etching area and the external environment can still be achieved.

[0044] The neutralization and cleaning unit 300 is connected to the rear end of the etching tank 200 and is used to remove the residual etching solution and acidic substances on the tube surface; the drying unit 400 is arranged after the neutralization and cleaning unit 300 and is used to blow dry the moisture on the surface of the cleaned PTFE tube; the exhaust gas treatment unit 500 is further connected after the drying unit 400 and is used to collect and purify the exhaust gas discharged from the above - mentioned units to meet the environmental protection requirements.

[0045] The control system is electrically connected to the driving device of the conveying mechanism 100, the inert gas supply system of the etching tank 200, the pressure sensors 606 and control valves 605 of each - level sealing structure, the neutralization and cleaning unit 300, the drying unit 400 and the exhaust gas treatment unit 500. It coordinates the start - stop sequence of each unit through a programmable logic controller and automatically adjusts the air pressure in the etching tank 200 and the pressure of each - level air chamber 602 of the sealing structure 600 according to the pressure and temperature parameters monitored in real time, so as to realize the stable, efficient and safe operation of the whole process.

[0046] In the sealing structure 600, the "positive - pressure level", "neutral - pressure level" and "negative - pressure level" of the three - stage sealing unit are all gauge pressures relative to the external ambient atmospheric pressure, and their specific numerical ranges are preferably as follows:

[0047] The positive pressure stage air chamber 602 preferably maintains the pressure inside the air chamber 602 within the range of (+50 Pa to +200 Pa) to form a pressure gradient pointing outward, preventing external air and moisture from entering the etching area. The neutral pressure stage air chamber 602 preferably controls the pressure inside the air chamber 602 within the range of (–10 Pa to +10 Pa) to make it basically balanced with the ambient pressure, thereby reducing the lateral pressure impact on the magnetic fluid 701 seal and the expansion seal layer. The negative pressure stage air chamber 602 preferably maintains the pressure inside the air chamber 602 within the range of (–50 Pa to –200 Pa) to generate a negative pressure gradient pointing inward, further attracting and exhausting the possibly overflowing gas to ensure that all leaked gases are safely directed to the tail gas treatment unit 500.

[0048] Based on the above embodiments, as a further limited embodiment, as Figure 2 and Figure 3 shown, at least one stage of the sealing unit adopts the magnetic fluid sealing structure 700 to achieve non-contact flexible sealing of the PTFE tube. The magnetic fluid sealing structure 700 is arranged in the channel section 601 of the sealing unit. The magnetic fluid 701 is composed of 5 to 15 wt% of magnetic nanoparticles suspended in a carrier liquid. The average particle size of the magnetic nanoparticles is 10 to 50 nm. The dynamic viscosity range of the magnetic fluid 701 at room temperature (20 °C) is 50 to 200 mPa·s, thus having both good fluidity and magnetic response performance.

[0049] A magnetic ring 702 is arranged on the periphery of the magnetic fluid sealing structure 700. The magnetic ring 702 is arranged around the outer wall of the channel section 601 to form a stable ring-shaped magnetic field. This magnetic field acts on the magnetic fluid 701, making it closely fit the outer surface of the PTFE tube under the drive of the magnetic force, thereby forming a continuous dynamic sealing band along its circumference to effectively block the leakage of gas and liquid inside the etching tank 200.

[0050] To further improve the sealing effect of the magnetic fluid 701 and adapt to the sealing requirements under different operating states, a micro magnetic array 703 for adjusting the magnetic field distribution is also arranged outside the magnetic ring 702. The magnetic array includes a plurality of magnetic element components arranged at intervals along the sealing direction, and each magnetic element component can independently adjust its magnetic flux intensity. Through the fine control of each magnetic element component, the magnetic field distribution of the magnetic fluid sealing structure 700 can be dynamically adjusted under different working conditions, thereby realizing the precise regulation of the sealing strength and the sealing area range, and further improving the adaptability of the sealing unit to the PTFE tube and the stability of the sealing performance.

[0051] In this embodiment, the magnetic fluid sealing structure 700 is located in the first-stage sealing unit. As an alternative embodiment, the magnetic fluid sealing structure 700 is located in the second-stage sealing unit.

[0052] Based on the above embodiments, as a further limited embodiment, asFigure 2 and Figure 4 As shown in Figure 4 , at least the first-stage sealing unit adopts a nitrogen vortex diversion structure 800. This diversion structure is arranged in coordination in the radial and circumferential directions: a tangential air inlet hole 801 is opened on the side wall of the air chamber 602, and its nozzle is tangentially directed towards the inner wall of the air chamber 602, which is used to eject the introduced nitrogen at a high speed in the tangential direction; a spiral air guiding groove 802 extends spirally along the inner wall of the air chamber 602, and its opening faces the center of the air chamber 602, which is used to receive and guide the tangentially ejected nitrogen, so that the nitrogen forms a continuous annular air curtain along the outer surface of the PTFE tube inside the air chamber 602, thereby enhancing the gas isolation effect on the circumference of the pipeline under the action of the vortex.

[0053] The tangential air inlet hole 801 and the spiral air guiding groove 802 are respectively communicated with a control valve 605 located outside the sealing structure through pipelines. The control valve 605 is controlled by a control system and is connected to the control system through electrical or signal lines. The control system adjusts the control valve 605 according to the pressure and flow parameters of the air chamber 602 monitored in real time to stably adjust the nitrogen flow rate within the range of 0.1 - 10 L / min, thereby precisely controlling the vortex intensity and distribution range of the annular air curtain to meet the sealing requirements of the sealing structure for gas and liquid leakage under different working conditions.

[0054] In this embodiment, the nitrogen vortex diversion structure 800 is located in the first-stage sealing unit. As an alternative embodiment, the nitrogen vortex diversion structure 800 is located in the second-stage sealing unit.

[0055] On the basis of the above embodiment, as a further limited embodiment, as shown in Figure 2 and Figure 5 , the third-stage sealing unit adopts an annular expansion type sealing layer 900. The annular expansion type sealing layer 900 is continuously arranged circumferentially along the outer wall of the outer sealing unit and is fixedly connected by directly fitting with the outer surface of the outer sealing unit. The expansion type sealing layer is composed of a polymer swelling material that is highly sensitive to oxygen or water vapor; when it absorbs oxygen or water vapor in the external environment, the volume of the material expands rapidly, prompting the sealing layer to tightly press inward against the outer wall of the outer sealing unit, forming a tight fitting connection interface, thereby further improving the barrier performance of the sealing structure against gas and liquid leakage.

[0056] Furthermore, the polymer swelling material used in the annular expansion type sealing layer 900 preferably has the following characteristics: at normal temperature of 20-25 °C and relative humidity of about 50%, the water absorption or oxygen absorption rate is less than 5 min, the swelling ratio can reach 10-100 times, and it can still maintain a certain mechanical strength and chemical corrosion resistance in the saturated state. The polymer swelling material can preferably be: sodium polyacrylate-acrylamide copolymer superabsorbent resin: copolymerized from sodium acrylate and acrylamide in a molar ratio of 1:0.1-1 and cross-linked with N,N'-ethylenebisacrylamide, having a high water absorption ratio of more than 50 times and good chemical stability. As an alternative embodiment, the polymer swelling material is cross-linked polyvinyl alcohol (PVA) hydrogel, with PVA as the main body, forming a three-dimensional network structure after cross-linking with cross-linking agents such as boric acid or glutaraldehyde, being sensitive to water vapor and capable of maintaining a certain elasticity after swelling. As an alternative embodiment, the polymer swelling material is modified bentonite, obtained by modifying natural bentonite with organic cations to improve the adsorption and swelling ability for polar molecules, and can further fill tiny gaps in the wet state. As an alternative embodiment, the polymer swelling material is sodium alginate-based water-absorbing material: constructing a Joule network by cross-linking sodium alginate with calcium salt ions, having both biodegradability and good swelling performance. As an alternative embodiment, the polymer swelling material is silane-modified silica, introducing hydrophilic groups on the surface of silica through silane coupling agents to form nano-scale water-absorbing particles, which can rapidly swell in a micro-moisture environment.

[0057] This embodiment also provides a method for continuously etching a PTFE tube, using the above-mentioned PTFE tube continuous etching equipment. This method includes the following steps:

[0058] Transportation: The PTFE tube to be processed is transported to the etching tank 200 at a constant speed of 0.5-2 m / min through the transportation mechanism 100;

[0059] Etching: Continuously immerse the PTFE tube in the etching tank 200 with a sodium-naphthalene etching solution at a temperature of 20-30 °C and a concentration of 5-10%, and introduce nitrogen into the tank body to maintain a positive pressure environment; wherein, during the etching process, the PTFE tube successively passes through the sealing structures provided at the inlet and outlet of the etching tank 200, uses the sealing structures to block oxygen and moisture in stages, and maintains the nitrogen flow rate at 0.1-10 L / min through the control valve 605;

[0060] Neutralization and cleaning: Pass the etched PTFE tube through the neutralization tank and multiple ultrasonic cleaning tanks in sequence to terminate the chemical reaction and remove the residual etching solution;

[0061] Drying: Dry the cleaned PTFE tube in a hot air drying unit at 80-120 °C;

[0062] Tail gas treatment: The tail gases of all the sealing structures and the etching tank 200 are uniformly introduced into the tail gas treatment unit, and after being treated by activated carbon adsorption, pickling or a condensation phase transfer adsorption layer, they are discharged up to the standard.

[0063] The above embodiments are only explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to the embodiments without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A continuous etching device for PTFE tubes, characterized in that, Comprising: A conveying mechanism (100) for continuously conveying the PTFE tube to be processed; An etching tank (200) located on the transmission path of the PTFE tube. The etching tank (200) is filled with a sodium-naphthalene etching solution and an inert gas is introduced to maintain a positive pressure environment; A sealing structure (600) provided at the inlet and outlet of the etching tank (200). Each sealing structure (600) includes at least three levels of sealing units arranged in sequence from inside to outside along the conveying direction of the PTFE tube. Each sealing unit includes a channel section (601) and an air chamber (602) communicated therewith. The air chamber (602) is provided with a gas input channel (603), a tail gas discharge port (604), a pressure sensor (606) and a control valve (605). The pressures of the air chambers (602) of each sealing unit are set as positive pressure, neutral pressure and negative pressure in sequence from the side close to the etching tank (200) to the outside; A neutralization and cleaning unit (300), a drying unit (400) and a tail gas treatment unit (500), which are sequentially connected to the rear end of the etching tank (200); A control system for coordinating the operation of each unit and adjusting the air pressure in the etching tank (200) and the working state of the sealing structure; Wherein, at least one level of sealing unit adopts a magnetorheological fluid sealing structure (700). The magnetorheological fluid (701) is composed of magnetic nanoparticles suspended in a carrier liquid. A circular magnetic field is formed by a magnetic ring (702) arranged outside the channel section (601) to drive the magnetorheological fluid (701) to fit the surface of the PTFE tube to form a dynamic sealing band; At least one level of sealing unit adopts a nitrogen vortex diversion structure (800). The diversion structure includes a tangential air inlet hole (801) and a spiral air guiding groove (802). The tangential air inlet hole (801) ejects nitrogen tangentially along the inner wall of the air chamber (602), and the spiral air guiding groove (802) guides the nitrogen to form an annular air curtain around the PTFE tube inside the air chamber (602); The third-level sealing unit adopts an annular expansion type sealing layer (900). The annular expansion type sealing layer (900) is composed of a polymer swelling material sensitive to oxygen or water vapor. The annular expansion type sealing layer (900) expands in volume after absorbing oxygen or moisture, and then forms a fitting connection with the inner wall of the channel section (601) of the sealing structure (600); 2. The PTFE tube continuous etching equipment according to claim 1, characterized in that: A micro magnetic array (703) for adjusting the magnetic field distribution is arranged on the periphery of the magnetorheological fluid sealing structure (700). The magnetic array includes a plurality of magnet elements that can independently control the magnetic flux, and is used to dynamically adjust the sealing strength and distribution range of the magnetorheological fluid (701) under different operating states; 3. The PTFE tube continuous etching equipment according to claim 1, characterized in that: The magnetorheological fluid (701) of the magnetorheological fluid sealing structure (700) is composed of 5-15 wt% of magnetic nanoparticles suspended in a carrier liquid, and the average particle size of the magnetic nanoparticles is 10-50 nm. The dynamic viscosity of the magnetorheological fluid (701) at 20 °C is 50-200 mPa·s.

4. The PTFE tube continuous etching equipment according to claim 1, characterized in that: The tangential air inlet holes (801) or the spiral air guide grooves (802) of the nitrogen vortex diversion structure (800) are connected to the control valve (605) through pipelines. The control valve (605) is controlled by the control system and is used to adjust the nitrogen flow rate within the range of 0.1 - 10 L / min to control the vortex intensity of the annular air curtain in real time.

5. A continuous etching method for PTFE tubes, characterized in that, Using the PTFE tube continuous etching equipment according to any one of claims 1 - 4, the method comprises the following steps: Transportation: The PTFE tube to be processed is transported to the etching tank (200) at a constant speed of 0.5 - 2 m / min through the transportation mechanism (100). Etching: Continuously immerse the PTFE tube in the etching tank (200) with a sodium-naphthalene etching solution at a temperature of 20 - 30 °C and a concentration of 5 - 10%. Nitrogen is introduced into the tank body to maintain a positive pressure environment. During the etching process, the PTFE tube successively passes through the sealing structures provided at the inlet and outlet of the etching tank (200), uses the sealing structures to block oxygen and moisture in stages, and maintains the nitrogen flow rate at 0.1 - 10 L / min through the control valve (605). Neutralization and cleaning: Pass the etched PTFE tube through the neutralization tank and the multi-stage ultrasonic cleaning tank in sequence to terminate the chemical reaction and remove the residual etching solution. Drying: Dry the cleaned PTFE tube in a hot air drying unit at 80 - 120 °C. Tail gas treatment: Uniformly introduce the tail gases of all the sealing structures and the etching tank (200) into the tail gas treatment unit, and discharge them up to the standard after being treated by activated carbon adsorption, pickling or a condensation phase transfer adsorption layer.

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