Insulating paper double-sided plasma deposition device, method, product and application

Abstract

This invention discloses a double-sided plasma deposition apparatus, method, product, and application for insulating paper, relating to the field of surface modification technology for electrical insulation materials. The apparatus includes a processing chamber, a gas mixing system, an electrode module, a power supply module, and a transmission device. The processing chamber is sequentially configured with a first processing zone, an isolation gas curtain, and a second processing zone along the transmission direction of the insulating paper. Air-floating multi-microporous electrodes are used to achieve contactless levitation transmission of the insulating paper. The isolation gas curtain blocks crosstalk between the precursors in both zones, allowing for the sequential deposition of hydrophilic and hydrophobic layers on both sides of the insulating paper, forming a gradient structure with decreasing wettability in the thickness direction. This invention eliminates mechanical damage and electrostatic problems during the transmission of insulating paper, achieves wide-width uniform modification, and balances vacuum drying efficiency during transformer manufacturing with long-term moisture-proof insulation performance. It is suitable for the preparation of insulating paper for power transformers, insulating bushings, and other equipment.

Description

Technical Field

[0001] This invention relates to the field of surface modification technology for electrical insulation materials, specifically to a double-sided plasma deposition apparatus, method, product, and application for insulating paper. Background Technology

[0002] Cellulose insulating paper is commonly used as an important solid insulating material in common power equipment such as transformers and insulating bushings. Its internal moisture content directly determines the electrical insulation strength and aging life of the equipment. In the manufacturing and drying process of transformers, insulating paper needs to have excellent water dissipation properties to improve process efficiency. In long-term operation, it is also necessary to prevent external free moisture from penetrating into the fiber. Therefore, endowing insulating paper with "unidirectional hydrophobic" Janus double-sided properties through surface modification technology has become a key cutting-edge direction for improving the overall performance of transformers. However, existing conventional hydrophobic modification schemes are difficult to meet the performance requirements of the entire life cycle of transformers and the requirements of industrial mass production: the single homogeneous hydrophobic coating prepared by existing technology can achieve external moisture barrier, but it also significantly increases the mass transfer resistance of the bound water inside the insulating paper to diffuse outward. In the vacuum drying process during the transformer manufacturing stage, it is easy to cause the internal moisture migration to be hindered, which greatly prolongs the vacuum drying and oil injection cycle, directly restricting the production efficiency and capacity of enterprises. Meanwhile, existing continuous modification equipment for wide-width insulating paper mostly adopts mechanical contact transmission structure, which is prone to micro-damage and static electricity accumulation on the surface of insulating paper, making it difficult to achieve uniform deposition of modified coating on wide-width surfaces and failing to meet the quality and efficiency requirements of industrial-grade continuous production. Therefore, it is necessary to design a double-sided plasma deposition apparatus, method, product, and application for insulating paper. Summary of the Invention

[0003] The purpose of this invention is to provide a double-sided plasma deposition apparatus, method, product, and application for insulating paper, in order to solve the problems mentioned in the background art, such as the difficulty in achieving both vacuum drying dehydration efficiency and long-term water-blocking performance in the hydrophobic modification of insulating paper, and the tendency for mechanical damage and uneven coating deposition to occur during continuous modification of wide-width insulating paper.

[0004] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, an insulating paper double-sided plasma deposition apparatus is provided, comprising a processing chamber, a gas mixing system for supplying precursor gas to the processing chamber, an electrode module disposed in the processing chamber, a power supply module for supplying power to the electrode module, and a transmission device for pulling and conveying insulating paper. The processing chamber is sequentially provided with a first processing area, an isolation air curtain, and a second processing area along the direction of the insulating paper transmission. The isolation air curtain is sealed and insulated from the first and second processing areas. The electrode module includes two sets of air-floating multi-microporous electrodes disposed in the first processing area and the second processing area. Each set of air-floating multi-microporous electrodes includes a high-voltage electrode and a ground electrode arranged opposite each other. The surface of the air-floating multi-microporous electrodes is distributed with through-holes. The air-floating multi-microporous electrodes spray gas into the insulating paper through the micropores, so that the insulating paper is suspended in the discharge gap between the upper and lower electrodes without contact. The isolation air curtain is located between the first processing zone and the second processing zone to prevent cross-diffusion of precursor gases in adjacent processing zones. The gas mixing system includes two independent gas mixing units, which are respectively fluidly connected to the air-floating microporous electrodes in the first and second processing zones to sequentially deposit a hydrophilic layer and a hydrophobic layer on the surface of the insulating paper, forming a gradient structure in which the wettability decreases from the inside to the outside along the thickness direction of the insulating paper.

[0005] As a further technical solution of the present invention, the air-floating multi-microporous electrode has a layered structure, including a conductive porous metal substrate and a ceramic dielectric layer attached to the surface of the conductive porous metal substrate facing the discharge gap; the conductive porous metal substrate has a buffer gas uniform cavity processed inside, and the ceramic dielectric layer has gas permeation channels that communicate with the buffer gas uniform cavity.

[0006] As a further technical solution of the present invention, the ceramic dielectric layer is selected as an Al2O3 ceramic dielectric layer with a thickness of 0.5mm~1.5mm; the axis of the micropores on the surface of the air-floating multi-microporous electrode is provided with an aerodynamic tilt angle of 5°~15° along the transmission direction of the insulating paper.

[0007] As a further technical solution of the present invention, the micropore distribution on the surface of the air-float multi-micropore electrode is divided into a central flow equalization gas delivery zone and an edge high-pressure gas dam zone. The central air distribution zone corresponds to the central region of the main width of the insulating paper, and the micropores are distributed in an equally spaced array. The edge high-pressure air dam area corresponds to the two edge positions of the insulating paper. The pore size of the micropores is smaller than that of the central flow equalization air supply area, and the pore density is higher than that of the central flow equalization air supply area.

[0008] As a further technical solution of the present invention, the gas mixing system also includes a gas path control module, a gas buoyancy distribution module, and an isolation gas curtain gas path; The gas path control module is used to regulate the mixing ratio of the precursor and the carrier gas and the airflow distribution. The air buoyancy distribution module is connected to the buffer uniform air cavity of the air-float multi-microporous electrode to provide a levitation power gas source. The isolation air curtain gas path is connected to the isolation air curtain to supply isolation gas. The gas path control module divides the airflow supplied to each of the air-float multi-micro-porous electrodes into a central main gas path and two auxiliary gas paths on both sides. The central main gas path corresponds to the central flow equalization gas delivery zone, and the two auxiliary gas paths on both sides correspond to the edge high-pressure gas dam zone. The back pressure of the two auxiliary gas paths on both sides is higher than that of the central main gas path.

[0009] As a further technical solution of the present invention, the isolation air curtain is provided with a pressure stabilizing chamber and a flow stabilizing baffle, the flow stabilizing baffle being used to stabilize the airflow entering the pressure stabilizing chamber; The isolation air curtain is provided with a pair of convergent slit nozzles arranged in a V-shape on the side facing the insulating paper. The slit width of the slit nozzles is 0.1mm~0.3mm, wherein the jet axis of the first slit is inclined at 15°~30° towards the first treatment area, and the jet axis of the second slit is inclined at 15°~30° towards the second treatment area. The isolation air curtain gas path introduces pure inert gas into the isolation air curtain at a pressure higher than the air cushion pressure of the treatment areas on both sides; A negative pressure exhaust groove is provided at the boundary between the isolation air curtain and the adjacent processing area to directionally extract the precursor exhaust gas and pure inert gas blocked by the air curtain. The power module is a dual-channel independent output nanosecond pulse power supply. Its two high-voltage output terminals are electrically connected to the high-voltage electrodes of the first processing area and the second processing area, respectively. The voltage amplitude, frequency, and duty cycle of the two outputs are independently adjustable.

[0010] In a second aspect, a method for double-sided plasma deposition of insulating paper is provided, implemented using the apparatus described in any one of the first aspects, comprising the following steps: S1: The insulating paper is pulled into the processing chamber by the transmission device. The gas sprayed through the micropores of the air-floating multi-micro-hole electrode makes the insulating paper float in the discharge gap between the upper and lower electrodes without contact and is continuously conveyed along the transmission direction. S2: In the first processing zone, a first precursor gas containing polar groups is supplied through a gas mixing system, and the power module is turned on to stimulate atmospheric pressure low-temperature plasma, and a hydrophilic layer is simultaneously deposited on both the upper and lower sides of the insulating paper. S3: The insulating paper that has completed the deposition of the hydrophilic layer passes through the isolation gas curtain continuously, and the inert gas curtain sprayed by the isolation gas curtain blocks the cross-diffusion of the precursor gas between the first treatment zone and the second treatment zone. S4: In the second processing zone, a second precursor gas containing non-polar groups is supplied through the gas mixing system, and the power module is turned on to excite atmospheric pressure low-temperature plasma. A hydrophobic layer is simultaneously deposited on the outer side of the hydrophilic layer on both sides of the insulating paper, forming a gradient structure with decreasing wettability from the inside to the outside in the thickness direction of the insulating paper. S5: The double-sided modified insulating paper is pulled out of the processing chamber by the transmission device and then wound up.

[0011] As a further technical solution of the present invention, the first precursor is selected as 3-aminopropyltriethoxysilane, and the second precursor is selected as hexamethyldisiloxane.

[0012] Thirdly, a modified insulating paper is provided, which is prepared by any one of the methods in the second aspect. The modified insulating paper includes a cellulose insulating paper substrate and a hydrophilic layer and a hydrophobic layer sequentially deposited on both sides of the cellulose insulating paper substrate, forming an asymmetric gradient structure in which wettability decreases from the inside to the outside along the thickness direction. The hydrophilic layer is a siloxane crosslinking layer covalently grafted with the hydroxyl groups of the cellulose insulating paper substrate and rich in amino polar groups; The hydrophobic layer is a silica-like nano-crosslinked network layer rich in methyl nonpolar groups.

[0013] Fourthly, the modified insulating paper described in the third aspect is provided for use in power transformers and insulating bushings in power equipment.

[0014] Compared with existing technologies, the beneficial effects of this double-sided plasma deposition apparatus, method, product, and application for insulating paper are: The air-floating, contactless transmission architecture employed in this invention significantly improves the yield rate of wide-width flexible insulation material processing and the stability of continuous equipment operation. By injecting gas through air-floating multi-microporous electrodes, the insulating paper is suspended in the discharge gap without contact throughout the entire process, completely eliminating the surface micro-cracks and electrostatic spot accumulation problems caused by traditional mechanical transmission methods during long-distance paper feeding of wide-width insulation paper. This effectively avoids localized filamentary arc ablation caused by electrostatic discharge, fully preserving the original tensile strength and AC breakdown voltage background performance of the cellulose insulation paper. Simultaneously, the multi-porous permeable electrode with an internal buffered gas-uniform cavity, designed in this invention, works in conjunction with the matching air... The road control module and pressure equalization flow field design overcome the precursor depletion effect caused by traditional side air intake, ensuring the uniformity of thin film deposition on a wide surface. Moreover, the double-sided synchronous discharge deposition achieved by the upper and lower symmetrical electrode structure eliminates the thermal stress deformation caused by alternating single-sided processing, doubling the single-line capacity of the equipment. In addition, the auxiliary propulsion effect brought by the aerodynamic tilt angle along the paper feeding direction through the electrode micropores, and the passive correction mechanism of the edge high-pressure air dam area set on the electrode surface, significantly reduce the background mechanical tension required for paper feeding, enabling high-speed continuous processing of low-stiffness cellulose materials, and significantly reducing the risk of tape breakage and shutdown. This invention employs a dual-path independent output nanosecond pulse power supply, combined with atmospheric pressure low-temperature plasma deposition technology, to achieve a green transformation of cellulose surface modification processes and intrinsic chemical non-destructive protection. The atmospheric pressure low-temperature plasma dry vapor deposition technology completely replaces traditional liquid-phase dipping and sol-gel processes, eliminating the emission of volatile organic compounds and wastewater pollution at the source, and eliminating the energy-intensive solvent recovery and hot air drying processes, achieving extremely low-energy manufacturing of insulating materials. More importantly, the cold-state characteristics of plasma non-equilibrium discharge, combined with millisecond-level reaction residence time matched with continuous transmission, ensures that the overall reaction is in a near-room temperature state. This dry process effectively avoids the dissolution of cellulose macromolecular chains by liquid-phase chemical reagents and thermal degradation caused by high temperatures, strictly maintaining the average degree of polymerization of the insulating paper and effectively guaranteeing the long-term anti-aging potential of the insulating material. This invention constructs an asymmetric gradient structure on the surface of insulating paper, with wettability decreasing from the inside to the outside along the thickness direction. This reshapes the dynamic migration behavior of moisture in the insulating paper, achieving a synergistic effect between improved efficiency in transformer manufacturing and long-term operation. The longitudinal wetting gradient film constructed in this invention significantly reduces the physical energy barrier for the desorption of bound water from the inside of the insulating paper. In the vacuum drying process of the transformer body, the "self-driven drainage" effect brought by this structure can significantly accelerate the vaporization and overflow of deep moisture in the matrix, breaking the "water seal" lag phenomenon caused by traditional strong hydrophobic films. This effectively shortens the vacuum drying and oil injection cycle of large transformers, saving enterprises significant time and energy costs. In the long-term operation stage after the transformer is put into operation, the highly cross-linked non-polar methyl silica nano-crosslinked network on the outermost layer of the modified insulating paper endows the material with excellent surface hydrophobicity. It can effectively resist the penetration and accumulation of free water in the insulating oil into the interior, fundamentally inhibiting the acidic hydrolysis reaction of cellulose catalyzed by water molecules, and significantly improving the long-term insulation reliability and overall service life of the transformer. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall device structure of the present invention; Figure 2 This is a side sectional view of the electrode module of the present invention; Figure 3 This is a schematic diagram of the isolation air curtain structure of the present invention; Figure 4 This is a schematic diagram of the air-float multi-microporous electrode structure of the present invention; Figure 5 This is a schematic diagram illustrating the principle of unidirectional water transport in this invention. Figure 6 This is a schematic diagram of the method flow in this invention; In the diagram: 1. Insulating paper; 2. First processing zone; 3. Second processing zone; 4. Isolation air curtain; 5. Multi-stage series air-float microporous electrode module (hereinafter referred to as electrode module); 6. Multi-path gasification mixing system (hereinafter referred to as mixing system); 7. Transmission device; 8. Power supply module; 41. Slit nozzle; 42. Negative pressure exhaust groove; 43. Pressure stabilizing chamber; 44. Flow stabilizing baffle; 51. Air-float microporous electrode; 52. High-voltage electrode; 53. Ground electrode; 511. Micropore; 512. Conductive porous metal substrate; 513. Ceramic dielectric layer; 61. Gas path control module; 62. Air buoyancy distribution module; 63. Isolation air curtain gas path; 64. Central main gas path; 65. Side auxiliary gas paths. Detailed Implementation

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

[0017] Please see Figures 1-5 The present invention provides an embodiment 1: a double-sided plasma deposition device for insulating paper, comprising a processing chamber, a multi-channel gasification mixing system (hereinafter referred to as the mixing system, reference 6) that supplies precursor gas to the processing chamber, a multi-stage series air-floating microporous electrode module (hereinafter referred to as the electrode module, reference 5) configured in the processing chamber, a power supply module 8 that supplies power to the electrode module 5, and a transmission device 7 for pulling the insulating paper 1 to be conveyed. The processing chamber is arranged in sequence along the transmission direction of the insulating paper 1, including the first processing area 2, the isolation air curtain 4, and the second processing area 3. The isolation air curtain 4 is seamlessly spliced ​​with the first processing area 2 and the second processing area 3 through an insulating flange with a high-pressure sealing structure to achieve a sealed and insulating connection. The electrode module 5 includes two sets of air-floating multi-microporous electrodes 51 respectively disposed in the first processing area 2 and the second processing area 3. Each set of air-floating multi-microporous electrodes 51 includes a high-voltage electrode 52 and a ground electrode 53 arranged opposite each other. The high-voltage electrode 52 is arranged above the processing cavity, and the ground electrode 53 is arranged below the processing cavity and reliably grounded. The surface of the air-floating multi-microporous electrode 51 is distributed with through-holes 511. The air-floating multi-microporous electrode 51 sprays gas into the insulating paper 1 through the micropores 511, forming a rigid air cushion between the electrode and the insulating paper 1, so that the insulating paper 1 is suspended in the discharge gap between the upper and lower electrodes without contact. Furthermore, the air-floating microporous electrode 51 has a layered structure, including a conductive porous metal substrate 512 and a ceramic dielectric layer 513 attached to the surface of the conductive porous metal substrate 512 facing the discharge gap. The conductive porous metal substrate 512 has a buffer gas uniform cavity inside, and the ceramic dielectric layer 513 has micron-level gas permeation channels that are connected to the buffer gas uniform cavity. While providing the electrical insulation strength required for dielectric barrier discharge, it also enables the uniform permeation of the mixed gas. Furthermore, the ceramic dielectric layer 513 is selected as an Al2O3 ceramic dielectric layer with a thickness of 0.5mm~1.5mm; the axis of the micropores 511 on the surface of the air-floating microporous electrode 51 is set with an aerodynamic tilt angle of 5°~15° along the transmission direction of the insulating paper 1, so that when the high-pressure mixed gas is ejected from the micropores 511, it generates an air cushion pressure that lifts the insulating paper 1 in the normal direction, and generates a surface aerodynamic shear force along the paper-feeding direction of the insulating paper 1 in the tangential direction, thus forming an auxiliary propulsion effect on the suspended insulating paper 1; Furthermore, the distribution of micropores 511 on the surface of the air-float multi-microporous electrode 51 is divided into a central flow equalization gas delivery zone and an edge high-pressure gas dam zone. The central flow equalization gas delivery zone corresponds to the central area of ​​the main width of the insulating paper 1. The micropores 511 are distributed in a high-density, equally spaced rectangular array, providing uniform vertical aerodynamic lifting force for the insulating paper 1, while ensuring the consistency of precursor gas concentration over a large area. The edge high-pressure air dam area corresponds to the two sides of the edge of the insulating paper 1, that is, the outermost 50mm~100mm area of ​​the electrode width. The pore diameter of the micropore 511 is smaller than that of the central flow equalization and gas delivery area and the pore density is higher than that of the central flow equalization and gas delivery area, forming a high flow resistance structure to form a high-pressure air dam on both sides of the insulating paper 1, so as to realize the non-contact passive centering and correction of the insulating paper 1. An isolation gas curtain 4 is placed between the first processing zone 2 and the second processing zone 3 to prevent cross-diffusion of precursor gases in adjacent processing zones, avoid cross-contamination between the polar precursor in the first processing zone 2 and the non-polar precursor in the second processing zone 3, and ensure the purity of the two-step deposition reaction. Furthermore, the isolation air curtain 4 is equipped with a pressure stabilizing chamber 43 and a flow stabilizing baffle 44. The flow stabilizing baffle 44 is used to eliminate airflow turbulence and stabilize the airflow pressure and velocity entering the pressure stabilizing chamber 43. A pair of converging slit nozzles 41 arranged in a V-shape are provided on the side of the isolation air curtain 4 facing the insulating paper 1. The slit width of the slit nozzles 41 is 0.1mm~0.3mm. The jet axis of the first slit is inclined at 15°~30° towards the first processing zone 2, and the jet axis of the second slit is inclined at 15°~30° towards the second processing zone 3. The throttling effect of the slits can be used to spray out two high-rigidity inclined micro-air curtains, forming a high-pressure diversion stagnation point on the surface of the insulating paper 1. Through the momentum blocking mechanism, the spatial convection and diffusion of the precursor gas on both sides are suppressed and cut off. The isolation gas curtain gas passage 63 introduces a pure inert gas with a pressure higher than that of the air cushions in the two treatment zones into the isolation gas curtain 4. This pure inert gas can be argon with a purity of ≥99.99%. A negative pressure exhaust groove 42 is provided at the junction of the isolation air curtain 4 and the adjacent processing area. It is used to directionally extract the precursor exhaust gas and inert gas blocked by the air curtain, construct a "blowing-suction" flow field closed loop, and at the same time prevent the high-pressure isolation airflow from invading the main processing area and dispersing the plasma discharge cloud, so as to maintain the continuity and stability of the air-floating suspension attitude of the insulating paper 1 when crossing the isolation area. The power module 8 is a dual-path independent output nanosecond pulse power supply. Compared with high-frequency AC power supply or microsecond pulse power supply, it has the advantages of gentle discharge, high energy efficiency and high utilization rate of excited active particles. Its two high-voltage output terminals are electrically connected to the high-voltage electrodes 52 of the first processing zone 2 and the second processing zone 3, respectively. The voltage amplitude, frequency and duty cycle of the two outputs can be adjusted independently. The optimal discharge parameters can be matched for the polar precursor system of the first processing zone 2 and the non-polar precursor system of the second processing zone 3, respectively, to ensure the crosslinking quality of the bilayer film. The gas mixing system 6 includes two independent gas mixing units, which correspond to the first processing zone 2 and the second processing zone 3 respectively. Each gas mixing unit includes a precursor storage bottle, a bubbling pipeline, a carrier gas pipeline and a gas mixing bottle. The precursor and argon carrier gas can be mixed and homogenized in a preset ratio by bubbling and then sent to the air-floating multi-microporous electrode 51 in the corresponding processing zone to achieve fluid communication with the air-floating multi-microporous electrode 51, so as to deposit a hydrophilic layer and a hydrophobic layer on the surface of the insulating paper 1 in sequence, forming a gradient structure with decreasing wettability from the inside to the outside along the thickness direction of the insulating paper 1. Furthermore, the mixing system 6 also includes an air path control module 61, an air buoyancy distribution module 62, and an isolation air curtain air path 63; The gas path control module 61 is used to regulate the mixing ratio of the precursor and the carrier gas and the airflow distribution. The air flotation force distribution module 62 has a built-in precision pressure regulating valve, which can stabilize and regulate the mixed gas entering the air flotation multi-microporous electrode 51. It is connected to the buffer uniform air cavity of the air flotation multi-microporous electrode 51 to provide the suspension power gas source. The isolation air curtain gas path 63 is connected to the isolation air curtain 4 to supply isolation gas. The air path control module 61 divides the airflow supplied to each air-float multi-micro-hole electrode 51 into a central main air path 64 and two auxiliary air paths 65. The central main air path 64 corresponds to the central flow equalization air delivery zone, and the two auxiliary air paths 65 correspond to the edge high-pressure air dam zone. The back pressure of the two auxiliary air paths 65 is higher than that of the central main air path 64. By increasing the back pressure of the two auxiliary air paths 65, a reliable airflow power source is provided for the air dam effect of the edge high-pressure air dam zone, ensuring the passive centering and correction effect of the insulating paper 1.

[0018] Please see Figure 6The present invention provides an embodiment 2: a double-sided plasma deposition method for insulating paper, implemented using the apparatus of embodiment 1 above, comprising the following steps: S1: The insulating paper 1 is pulled into the processing chamber by the transmission device 7. The gas injected through the micropores 511 of the air-floating multi-microporous electrode 51 makes the insulating paper 1 float in the discharge gap between the upper and lower electrodes without contact and is continuously conveyed along the transmission direction. Before the step is executed, the device is pre-adjusted: the carrier gas valve of the gas mixing system 6 is opened, and argon carrier gas is introduced into the air-floating multi-microporous electrode 51 through the air buoyancy distribution module 62 to establish a stable air cushion pressure field on the electrode surface; the isolation air curtain gas path 63 is opened to establish a rigid air curtain barrier of the isolation air curtain 4 and the negative The pressure extraction closed loop is used; the servo parameters of the transmission device 7 are adjusted, and the linear speed synchronization of the unwinding unit and the winding unit is calibrated. The transmission speed of the insulating paper 1 is set to 2m / min~20m / min. During the transmission process, the high-pressure gas ejected from the air-floating multi-microporous electrode 51 forms a uniform rigid air cushion between the electrode and the insulating paper 1. Based on the principle of air cushion bearing in fluid mechanics, the insulating paper 1 is completely lifted in the discharge gap, achieving no physical contact between the insulating paper 1 and the electrode or mechanical parts throughout the process, fundamentally eliminating the surface micro-cracks caused by traditional mechanical guide roller transmission. To address the issues of texture and static clot accumulation and prevent localized filamentous arc ablation caused by static electricity, the micropores 511 on the surface of the air-floating multi-microporous electrode 51 are aerodynamically tilted at an angle of 5° to 15° along the transmission direction of the insulating paper 1. When the high-pressure mixed gas is ejected from the tilted micropores, it generates an air cushion pressure that lifts the insulating paper 1 in the normal direction, while simultaneously generating a surface aerodynamic shear force along the paper-feeding direction in the tangential direction. This provides an auxiliary propulsion effect on the suspended insulating paper 1, reducing the tension load on the main traction motor outside the reaction zone and preventing the flexible insulating paper from being subjected to high tension. A breakage occurs; simultaneously, the high-pressure air dam area at the outermost edge of the air-floating multi-microporous electrode 51, with a width of 50mm~100mm, forms a high flow resistance structure by reducing the micropore diameter and increasing the pore density, creating two extremely high-pressure air dams on both sides of the insulating paper 1; when the insulating paper 1 deviates laterally to either side, the paper edge will cut off the high-pressure airflow exhaust channel of the air dam on that side, instantly generating a powerful lateral aerodynamic counter-force, pushing the insulating paper 1 back to the center position, realizing non-contact passive centering and correction of the material, ensuring that there is no deviation or wrinkles during the paper feeding process; S2: Within the first processing zone 2, a first precursor gas containing polar groups is supplied via the gas mixing system 6. The power module 8 is activated to stimulate atmospheric pressure low-temperature plasma, simultaneously depositing a hydrophilic layer on both the upper and lower sides of the insulating paper 1. The first precursor is selected as 3-aminopropyltriethoxysilane (APTES). The first set of independent gas mixing units in the gas mixing system 6 uses a flow controller to mix the APTES precursor with argon carrier gas in precise proportions via a bubbling method: one path is introduced to the bottom of the APTES storage bottle via a bubbling pipeline, where APTES molecules are entrained by the bubbling method to form a carrier gas containing the precursor, which is then sent to the gas mixing bottle; the other path is directly introduced into the gas mixing bottle via a pipeline to regulate the precursor concentration. After the two gases are fully homogenized, a mixed gas with an APTES volume concentration of 0.5% to 5% is formed and uniformly fed into the buffer uniform gas cavity of the upper and lower air-floating multi-microporous electrodes 51 in the first processing zone 2. The output path of the power module 8 corresponding to the first processing zone 2 is turned on. The power module 8 is a dual-path independent output nanosecond pulse power supply, and the output parameters are independently adjusted to match the polarity of the APTES precursor system. The parameters are set as follows: voltage amplitude 10kV to 30kV, frequency 5kHz to 20kHz, and duty cycle 1% to 10%. In the discharge gap between the upper and lower symmetrical high-voltage electrodes 52 and the ground electrode 53, atmospheric pressure dielectric barrier discharge low-temperature plasma is excited. The process involves controlling the residence time of insulating paper 1 in the first treatment zone 2 to be 0.5s~5s, achieving simultaneous deposition modification on both the upper and lower sides of insulating paper 1. This process relies on the non-equilibrium discharge characteristics of atmospheric pressure low-temperature plasma to achieve dry non-destructive modification: In the discharge gap, electrons are accelerated by an external high-frequency pulsed electric field to obtain extremely high kinetic energy, sufficient to break the chemical bonds on the surface of the insulating paper and the molecular bonds of the APTES precursor. However, the electron mass is extremely small, and the energy transferred by elastic collisions with ions or neutral gas molecules is minimal, keeping the temperature of the entire macroscopic gas flow field consistently near room temperature. This induces gas-phase free radicals without damaging the mechanical strength and electrical background properties of the insulating paper. Chemical vapor deposition reaction; during the reaction, APTES molecules are partially cleaved by high-energy electrons, and their siloxane groups undergo dehydration condensation reaction with the hydroxyl groups on the surface of cellulose insulating paper to achieve covalent grafting; at the same time, APTES exposes a large number of amino polar hydrophilic groups to the outside, forming an APTES hydrophilic layer on the surface of insulating paper 1; this hydrophilic layer serves as a "chemical bridge" between the cellulose substrate and the subsequent hydrophobic layer, enhancing the interfacial bonding force between the two films; on the other hand, it utilizes the strong hydrogen bonding between amino groups and water molecules to actively adsorb and enrich the bound water deep in the substrate of insulating paper 1 to the near surface, preventing the water from being directly sealed inside the substrate by the subsequent hydrophobic layer; S3: The insulating paper 1, having completed the hydrophilic layer deposition, continuously passes through the isolation gas curtain 4. The inert gas curtain 4 blocks the cross-diffusion of precursor gases between the first processing zone 2 and the second processing zone 3. The insulating paper 1, having completed the first-stage hydrophilic layer deposition, continuously and smoothly passes through the isolation gas curtain 4 region at a constant transmission speed. Pure argon inert gas is continuously introduced into the pressure stabilizing chamber 43 inside the isolation gas curtain 4 via the gas path 63. The pressure of the introduced gas is 0.02MPa~0.05MPa higher than the air cushion pressure in the two processing zones. The airflow first passes through the flow stabilizing baffle 44 to eliminate turbulence and stabilize the flow velocity and pressure before being sent into a pair of converging slit nozzles 45 arranged in a V-shape at the bottom. The slit width of the slit nozzles 45 is precisely controlled between 0.1mm and 0.3mm, with the jet axis of the first slit inclined at 15°~30° towards the first processing zone 2, and the jet axis of the second slit... The line is inclined at 15°~30° towards the second processing zone 3. Utilizing the throttling effect of the slit, two high-rigidity inclined micro-air curtains are ejected, forming a high-pressure diversion stagnation point on the surface of the insulating paper 1. Through the momentum blocking mechanism, the spatial convection and diffusion of the polar APTES and non-polar HMDSO precursor gases on both sides are suppressed and cut off, achieving efficient physical isolation between different precursor reaction zones. The precursor exhaust gas and inert gas blocked by the high-pressure air curtain flow into the negative pressure exhaust groove 42 at the junction of the isolation air curtain 4 and the two processing zones, and are directionally extracted by the external exhaust system, thus constructing a "blowing-suction" flow field closed loop. This structure builds a gas phase isolation barrier on the surface of the insulating paper 1, while ensuring the purity of the two-step deposition reaction. It also completely avoids the high-pressure isolation airflow from intruding into the main processing zone and dispersing the plasma discharge cloud, maintaining the continuity and stability of the air-floating suspension attitude of the flexible insulating paper when crossing the isolation zone. S4: In the second processing zone 3, a second precursor gas containing non-polar groups is supplied through the gas mixing system 6, and the power module 8 is turned on to excite atmospheric pressure low-temperature plasma. A hydrophobic layer is simultaneously deposited on the outer side of the hydrophilic layer on both sides of the insulating paper 1, forming a gradient structure with decreasing wettability from the inside to the outside in the thickness direction of the insulating paper 1. The second precursor is selected as hexamethyldisiloxane (HMDSO). The second set of independent gas mixing units of the gas mixing system 6 mixes the HMDSO precursor with argon carrier gas in a precise ratio through bubbling to form a mixed gas with an HMDSO volume concentration of 1%~8%, which is uniformly sent into the buffer uniform gas cavity of the upper and lower air-floating multi-microporous electrodes 51 in the second processing zone 3. The power module 8 is turned on. Block 8 corresponds to the output path of the second processing zone 3. The nanosecond pulse power supply parameters are independently adjusted to match the nonpolar HMDSO precursor system. The parameters are set as follows: voltage amplitude 15kV~35kV, frequency 5kHz~20kHz, duty cycle 1%~10%, to excite atmospheric pressure low-temperature plasma within the discharge gap. The residence time of insulating paper 1 in the second processing zone 3 is controlled to be 1s~10s, and synchronous cross-linking deposition is achieved on the outer side of the APTES hydrophilic layer on both sides of the insulating paper 1. During this process, after HMDSO enters the plasma field, its molecular bonds are broken by high-energy electrons, forming a large number of silicon- and methyl-containing free radical fragments. These fragments are further cross-linked on the APTES hydrophilic layer to generate a rich... A hydrophobic layer of a silica-like polymer nanonetwork containing nonpolar methyl groups, together with the inner hydrophilic layer of APTES, forms a longitudinal wetting gradient Janus film structure with increasing hydrophobicity from the inside out. The core working mechanism of this structure is as follows: In the vacuum drying and dehydration process of transformers, during the dehydration of traditional isotropic hydrophilic insulating paper, moisture easily condenses on the surface via capillary action, forming a continuous water film and creating a "water seal effect" that prevents further leakage of internal gaseous moisture. However, the gradient film constructed in this invention, according to the Laplace pressure formula, has an outer hydrophobic film with extremely low surface tension. When moisture migrates outward from the inside of the insulating paper 1, it is driven by an asymmetric Laplace pressure difference pointing towards the hydrophobic side, and is affected by APTES. The PTES hydrophilic layer adsorbs and enriches water near the surface. Upon contact with the HMDSO hydrophobic interface, the sudden change in surface energy prevents wetting and spreading. The water is rapidly desorbed and evaporated in a discrete state, greatly reducing the desorption energy barrier for water overflow and achieving "self-driven drainage" to accelerate drying. This completely solves the problem of traditional single hydrophobic modification exacerbating the drying and dehydration bottleneck. During the long-term operation of the transformer, the free liquid water in the external insulating oil is completely blocked from penetrating the fiber matrix due to the lack of capillary driving force for inward penetration. This fundamentally inhibits the acidic hydrolysis reaction of cellulose catalyzed by water molecules, significantly improving the long-term insulation reliability and overall service life of the transformer. S5: The double-sided modified insulating paper 1 is pulled out of the processing chamber by the transmission device 7 and wound up. The winding unit and unwinding unit of the transmission device 7 are kept in closed-loop servo control in complete synchronization. The modified insulating paper is wound up smoothly with constant low tension. There is no mechanical friction or bending damage throughout the process, which ensures the integrity of the double-sided modified film structure and the uniformity of deposition in the width direction. After winding, the two precursor bubbling pipelines are closed first, and the argon carrier gas is maintained for 5 min to 10 min to purge the precursor gas in the device pipeline. Then, the power module 8, the gas mixing system 6, the isolation gas curtain gas path 63 and the transmission device 7 are closed in sequence to complete the entire process. The modified insulating paper finally obtained retains the original tensile strength and AC breakdown voltage background performance of cellulose insulating paper by relying on the air-float suspension non-contact transmission architecture. At the same time, through the longitudinal wetting gradient film structure, it takes into account the vacuum drying and dehydration efficiency in the transformer manufacturing stage and the moisture-proof insulation stability in the long-term operation stage.

[0019] Another embodiment 3 provided: A modified insulating paper is provided, which is prepared by the method of embodiment 2. The modified insulating paper includes a cellulose insulating paper substrate and a hydrophilic layer and a hydrophobic layer sequentially deposited on both sides of the cellulose insulating paper substrate, forming an asymmetric gradient structure in which the wettability decreases from the inside to the outside along the thickness direction. The hydrophilic layer is a siloxane crosslinking layer covalently grafted with the hydroxyl groups of the cellulose insulating paper substrate and rich in amino polar groups; The hydrophobic layer is a silica-like nano-crosslinked network layer rich in methyl nonpolar groups.

[0020] Another embodiment 4 provides the application of the modified insulating paper of embodiment 3 in power transformers and insulating bushings in power equipment.

[0021] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A double-sided plasma deposition apparatus for insulating paper, comprising a processing chamber, a gas mixing system (6) for supplying precursor gas to the processing chamber, an electrode module (5) disposed within the processing chamber, a power supply module (8) for supplying power to the electrode module (5), and a transmission device (7) for pulling and conveying insulating paper (1), characterized in that: The processing chamber is provided with a first processing area (2), an isolation air curtain (4), and a second processing area (3) in sequence along the transmission direction of the insulating paper (1). The isolation air curtain (4) is sealed and insulated from the first processing area (2) and the second processing area (3). The electrode module (5) includes two sets of air-floating microporous electrodes (51) respectively disposed in the first processing area (2) and the second processing area (3). Each set of air-floating microporous electrodes (51) includes a high-voltage electrode (52) and a ground electrode (53) arranged opposite to each other. The surface of the air-floating microporous electrodes (51) is distributed with through-hole micropores (511). The air-floating microporous electrodes (51) spray gas into the insulating paper (1) through the micropores (511), so that the insulating paper (1) is suspended in the discharge gap between the upper and lower electrodes without contact. The isolation curtain (4) is located between the first processing zone (2) and the second processing zone (3) to prevent the cross-diffusion of precursor gases in adjacent processing zones; The gas mixing system (6) includes two independent gas mixing units. The two gas mixing units are fluidly connected to the air-floating microporous electrodes (51) of the first processing zone (2) and the second processing zone (3) respectively, so as to deposit a hydrophilic layer and a hydrophobic layer on the surface of the insulating paper (1) in sequence, forming a gradient structure with decreasing wettability from the inside to the outside along the thickness direction of the insulating paper (1).

2. The double-sided plasma deposition apparatus for insulating paper according to claim 1, characterized in that: The air-floating microporous electrode (51) has a layered structure, including a conductive porous metal substrate (512) and a ceramic dielectric layer (513) attached to the surface of the conductive porous metal substrate (512) facing the discharge gap. The conductive porous metal substrate (512) has a buffer gas uniform cavity inside, and the ceramic dielectric layer (513) has gas permeation channels that communicate with the buffer gas uniform cavity.

3. The double-sided plasma deposition apparatus for insulating paper according to claim 2, characterized in that: The ceramic dielectric layer (513) is selected as an Al2O3 ceramic dielectric layer with a thickness of 0.5mm~1.5mm; the axis of the micropores (511) on the surface of the air-floating multi-microporous electrode (51) is provided with an aerodynamic tilt angle of 5°~15° along the transmission direction of the insulating paper (1).

4. The double-sided plasma deposition apparatus for insulating paper according to claim 3, characterized in that: The micropores (511) on the surface of the air-float multi-microporous electrode (51) are divided into a central flow equalization gas delivery zone and an edge high-pressure gas dam zone. The central air distribution zone corresponds to the central area of ​​the main width of the insulating paper (1), and the micropores (511) are distributed in an equally spaced array. The edge high-pressure air dam area corresponds to the two edge positions of the insulating paper (1). The pore size of the micropore (511) is smaller than that of the central flow equalization air supply area and the pore density is higher than that of the central flow equalization air supply area.

5. The double-sided plasma deposition apparatus for insulating paper according to claim 4, characterized in that: The gas mixing system (6) also includes a gas path control module (61), a gas buoyancy distribution module (62), and an isolation air curtain gas path (63). The gas path control module (61) is used to regulate the mixing ratio of the precursor and the carrier gas and the airflow distribution. The air buoyancy distribution module (62) is connected to the buffer uniform air cavity of the air-float multi-microporous electrode (51) to provide a levitation power gas source. The isolation air curtain gas path (63) is connected to the isolation air curtain (4) to supply isolation gas. The gas path control module (61) divides the airflow supplied to each of the air-float multi-micro-porous electrodes (51) into a central main gas path (64) and two auxiliary gas paths (65) on both sides. The central main gas path (64) corresponds to the central flow equalization gas delivery zone, and the two auxiliary gas paths (65) on both sides correspond to the edge high-pressure gas dam zone. The back pressure of the two auxiliary gas paths (65) is higher than that of the central main gas path (64).

6. The double-sided plasma deposition apparatus for insulating paper according to claim 5, characterized in that: The isolation air curtain (4) is provided with a pressure stabilizing chamber (43) and a flow stabilizing baffle (44) inside. The flow stabilizing baffle (44) is used to stabilize the airflow entering the pressure stabilizing chamber (43). The isolation air curtain (4) is provided with a pair of convergent slit nozzles (41) arranged in a V-shape on the side facing the insulating paper (1). The slit width of the slit nozzles (41) is 0.1mm~0.3mm, wherein the jet axis of the first slit is inclined at 15°~30° towards the first treatment area (2), and the jet axis of the second slit is inclined at 15°~30° towards the second treatment area (3). The isolation air curtain air passage (63) introduces pure inert gas with a pressure higher than that of the air cushion pressure in the two treatment zones into the isolation air curtain (4); A negative pressure exhaust groove (42) is provided at the junction of the isolation air curtain (4) and the adjacent processing area to directionally extract the precursor exhaust gas and pure inert gas blocked by the air curtain; The power module (8) is a dual-channel independent output nanosecond pulse power supply. Its two high-voltage output terminals are electrically connected to the high-voltage electrodes (52) of the first processing area (2) and the second processing area (3), respectively. The voltage amplitude, frequency and duty cycle of the two outputs are independently adjustable.

7. A method for double-sided plasma deposition of insulating paper, characterized in that, The device according to any one of claims 1 to 6 is used to implement the following steps: S1: The insulating paper (1) is pulled into the processing chamber by the transmission device (7). The gas sprayed through the micro-hole (511) of the air-floating multi-micro-hole electrode (51) makes the insulating paper (1) float in the discharge gap between the upper and lower electrodes without contact and is continuously conveyed along the transmission direction. S2: In the first processing zone (2), the first precursor gas containing polar groups is supplied through the gas mixing system (6), the power module (8) is turned on to stimulate atmospheric pressure low temperature plasma, and a hydrophilic layer is simultaneously deposited on both the upper and lower sides of the insulating paper (1). S3: The insulating paper (1) that has completed the deposition of the hydrophilic layer passes through the isolation curtain (4) continuously. The inert gas curtain (4) sprayed by the isolation curtain (4) blocks the cross-diffusion of the precursor gas between the first treatment zone (2) and the second treatment zone (3). S4: In the second processing zone (3), a second precursor gas containing non-polar groups is supplied through the gas mixing system (6), and the power module (8) is turned on to excite atmospheric pressure low-temperature plasma. A hydrophobic layer is simultaneously deposited on the outside of the hydrophilic layer on both sides of the insulating paper (1), forming a gradient structure with decreasing wettability from the inside to the outside in the thickness direction of the insulating paper (1). S5: The double-sided modified insulating paper (1) is pulled out of the processing chamber by the transmission device (7) and then wound up.

8. The method for double-sided plasma deposition of insulating paper according to claim 7, characterized in that: The first precursor is selected as 3-aminopropyltriethoxysilane, and the second precursor is selected as hexamethyldisiloxane.

9. A modified insulating paper, characterized in that, The modified insulating paper is prepared by any one of claims 7 to 8, comprising a cellulose insulating paper substrate and a hydrophilic layer and a hydrophobic layer sequentially deposited on both sides of the cellulose insulating paper substrate, forming an asymmetric gradient structure in which wettability decreases from the inside to the outside along the thickness direction; The hydrophilic layer is a siloxane crosslinking layer covalently grafted with the hydroxyl groups of the cellulose insulating paper substrate and rich in amino polar groups; The hydrophobic layer is a silica-like nano-crosslinked network layer rich in methyl nonpolar groups.

10. The application of the modified insulating paper according to claim 9 in power transformers and insulating bushings in power equipment.

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