High adhesive strength hot melt adhesive insulation film and its preparation process

Abstract

The application relates to the technical field of hot melt adhesive film processing, in particular to a hot melt adhesive insulation film with high bonding strength and a preparation process thereof; the hot melt adhesive insulation film comprises a PET film, an ink layer and a hot melt flame-retardant polyester adhesive layer; the PET film is sent into a constant-temperature oven for constant-temperature drying, and composite flame retardants, anti-aging agents and temperature-resistant modified filler powders are respectively screened for standby; micro-gravure coating equipment is used to uniformly coat the insulation ink on the surface of the PET base film; hot melt adhesive liquid is prepared in a closed stirring kettle; the prepared hot melt adhesive liquid is transported to scraper coating equipment, and the adhesive liquid is coated on the surface of the ink transition layer by using a scraper; the composite film with the coated hot melt adhesive layer is sent into segmented hot pressing equipment; the finished product film body after hot pressing is cooled and shaped; the surface of the hot melt adhesive layer is subjected to corona activation treatment; the bonding strength between the hot melt adhesive insulation film and the metal wire is enhanced, and the problems of delamination and peeling after repeated bending and high-low temperature cycles of the product are avoided.

Description

Technical Field

[0001] This invention relates to the field of hot melt adhesive film processing technology, and in particular to a hot melt adhesive insulating film with high bonding strength and its preparation process. Background Technology

[0002] Flexible flat cables (FFCs), with their advantages of flexibility, bendability, compact size, and easy assembly, are widely used in various consumer and industrial electronic products such as printers, copiers, LCD home appliances, and electronic instruments. Hot melt adhesive insulation film is a core component of flexible flat cables, primarily composed of a PET base film and a hot melt adhesive layer. It serves two purposes: firstly, it provides insulation and flame-retardant protection for the flat copper wires inside the cable; secondly, the adhesive layer's bonding force secures the metal conductors, ensuring the overall structural stability of the cable and normal signal transmission.

[0003] Currently, hot melt adhesive films are prepared using PET film as a substrate, combined with ordinary hot melt polyester adhesive, and through conventional single-stage coating and single hot-pressing processes.

[0004] In the above-mentioned prior art, the hot melt adhesive insulating film has poor bonding performance, and the PET base film, hot melt adhesive layer and metal wire are not firmly bonded. After repeated bending and alternating high and low temperatures, the product is prone to delamination and peeling failure. Summary of the Invention

[0005] The purpose of this invention is to provide a hot melt adhesive insulating film with high bonding strength and its preparation process, aiming to solve the technical problems of poor bonding performance of hot melt adhesive insulating films prepared in the prior art, weak bonding between PET base film, hot melt adhesive layer and metal wire, and easy delamination and peeling failure after repeated bending and alternating high and low temperature.

[0006] To achieve the above objectives, the present invention employs a high-adhesion-strength hot melt adhesive insulating film comprising: a PET film, an ink layer, and a hot melt flame-retardant polyester adhesive layer. The hot melt flame-retardant polyester adhesive layer comprises 70-85 parts of hot melt flame-retardant polyester resin, 3-8 parts of adhesion promoter, 8-15 parts of composite flame retardant, 1-3 parts of anti-aging agent, 0.2-0.8 parts of crosslinking agent, 2-5 parts of temperature-resistant modified filler, and 10-20 parts of methyl ethyl ketone solvent.

[0007] This invention also provides a process for preparing a hot melt adhesive insulating film with high bonding strength, comprising the following steps: Take the PET film and put it into a constant temperature oven for drying. Then, sieve the composite flame retardant, anti-aging agent and temperature-resistant modified filler powder separately for later use. Insulating ink is uniformly coated onto the surface of a PET base film using a micro-gravure coating machine, and then cured step by step through a three-stage gradient drying tunnel to obtain an ink transition layer. Prepare the hot melt adhesive solution in a sealed mixing tank and then filter it; The prepared hot melt adhesive is conveyed to the doctor blade coating equipment, and the doctor blade is used to coat the adhesive onto the surface of the ink transition layer. The composite film coated with hot melt adhesive is sent into a segmented hot pressing equipment, with nitrogen gas continuously supplied for protection throughout the process; The finished film after hot pressing is transported to an air-cooled cooling channel for cooling and shaping. After cooling and shaping, the film is sent to a corona treatment device with a corona power of 20kW to activate the surface of the hot melt adhesive layer. After the corona treatment is completed, the film is transferred to a room temperature resting area and left to stand continuously at room temperature for 30 hours. The membrane body, after being left to stand, is cut using a slitting device to remove edge waste. The slitting membrane body is then wound up using a constant tension winding device, with the tension controlled at 5~8N. After winding, the finished product is tested for performance according to the product standard. Once all indicators pass the test, the membrane body is put into storage.

[0008] In the step of sending the PET film into a constant temperature drying oven for constant temperature drying, and sieving the composite flame retardant, anti-aging agent and temperature-resistant modified filler powder for later use: Select a PET insulating base film with a thickness of 18μm and place it inside a constant temperature oven; Set the oven temperature to 85℃ and continuously dry the PET film at a constant temperature for 4 hours to remove moisture adsorbed on the surface and inside of the film. Collect three types of powder raw materials: composite flame retardant, anti-aging agent, and temperature-resistant modified filler, and feed them into the screening equipment; The powder raw materials are screened using a 300-mesh standard sieve to remove large particles and material agglomerates. After screening, the materials are sealed and stored for later use.

[0009] In the step of uniformly coating insulating ink onto the surface of a PET base film using a micro-gravure coating device and then curing it step by step through a three-stage gradient drying tunnel to obtain an ink transition layer: Start the microgravure coating equipment, feed the dried PET base film into the equipment at a uniform speed, control the equipment running speed to 10m / min, and uniformly coat the PET base film surface with insulating ink. The ink-coated film is sequentially introduced into three gradient drying tunnels, with the tunnel temperatures set at 70℃, 90℃, and 110℃ respectively. The film remains in each drying tunnel for 15-20 seconds to complete the step-by-step curing. After the curing process is completed, a dense and strongly adhesive ink transition layer is formed on the surface of the PET base film.

[0010] In the step of preparing the hot melt adhesive solution in a closed mixing tank and then filtering it: Add methyl ethyl ketone solvent and hot-melt flame-retardant polyester resin sequentially to a sealed stirring vessel, and heat to 60~75℃ and stir until the resin is completely dissolved. Add the adhesion promoter, composite flame retardant, temperature-resistant modified filler, and anti-aging agent in sequence, and stir at high speed for 40-50 minutes to fully mix the materials; Add crosslinking agent, switch to room temperature and low speed stirring for 10-15 minutes, and continuously purge nitrogen gas for protection throughout the stirring process. The mixed adhesive solution was filtered using a 200-mesh filter to remove minute impurities, resulting in a homogeneous hot melt adhesive solution.

[0011] In the step of conveying the prepared hot melt adhesive to the doctor blade coating equipment and applying the adhesive to the surface of the ink transition layer using a doctor blade: The filtered hot melt adhesive liquid is conveyed into the material tank of the doctor blade coating equipment; The composite substrate with the ink transition layer is fed into the coating equipment, and the equipment operating speed is set to 8m / min. The coating amount is precisely controlled by a doctor blade, and hot melt adhesive is applied to the surface of the ink transition layer, with a dry film thickness of 20μm.

[0012] In the step of feeding the composite film coated with hot melt adhesive into the segmented hot pressing equipment, nitrogen gas is continuously supplied for protection throughout the process: The pressure is applied in three pressure and temperature zones: pre-pressure zone 110℃, 0.12MPa; main pressure zone 128℃, 0.25MPa; and stabilizing zone 95℃, 0.18MPa.

[0013] In the step of conveying the finished film after hot pressing and lamination to the air-cooling channel for cooling and shaping: The ambient temperature inside the channel is kept constant at 25°C, and the membrane passes through a cooling zone with a length of 10m.

[0014] The process includes: using a slitting device to cut the settled film body, removing edge waste, and using a constant tension winding device to wind the slit film body, with the tension controlled at 5~8N. After winding, the finished product undergoes performance testing according to product standards, and is put into storage only after all indicators pass the inspection. Performance testing includes bond strength, voltage resistance, flame retardancy, and high and low temperature cycling.

[0015] This invention discloses a high-bonding-strength hot melt adhesive insulating film and its preparation process, comprising a PET film, an ink layer, and a hot melt flame-retardant polyester adhesive layer; the process includes the following steps: PET film is placed in a constant-temperature oven for drying; composite flame retardant, anti-aging agent, and temperature-resistant modified filler powders are sieved for later use; insulating ink is uniformly coated onto the surface of the PET base film using a micro-gravure coating device, and then cured step-by-step through a three-stage gradient drying tunnel to obtain an ink transition layer; hot melt adhesive solution is prepared in a sealed stirring tank and filtered; the prepared hot melt adhesive solution is transported to a doctor blade coating device, and the adhesive solution is coated onto the surface of the ink transition layer using a doctor blade; the composite film coated with the hot melt adhesive layer is sent to a segmented hot pressing device, with continuous nitrogen protection throughout the process; the finished film after hot pressing is transported to an air-cooling cooling channel. The process involves cooling and shaping the film. After cooling and shaping, the film is placed in a corona treatment device with a power of 20kW to activate the hot melt adhesive layer. Once the corona treatment is complete, the film is transferred to a room-temperature resting area and left to stand continuously for 30 hours. A slitting device is then used to cut the film, removing edge waste. A constant tension winding device is then used to wind up the cut film, with the tension controlled at 5-8N. After winding, the finished product undergoes performance testing according to product standards. Once all indicators pass the test, the film is stored in the warehouse. This method enhances the bonding strength between the layers of the hot melt adhesive insulating film and with the metal conductor, preventing delamination and peeling after repeated bending and high / low temperature cycling, thus improving the structural stability and durability of the cable. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the preparation process of the high-bonding-strength hot melt adhesive insulating film of the present invention.

[0018] Figure 2 This is a flowchart of steps S100 of the present invention.

[0019] Figure 3 This is a flowchart of steps S200 of the present invention.

[0020] Figure 4 This is a flowchart of steps S300 of the present invention.

[0021] Figure 5 This is a flowchart of steps S400 of the present invention. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0025] This invention provides a high-bonding-strength hot melt adhesive insulating film, comprising: a PET film, an ink layer, and a hot melt flame-retardant polyester adhesive layer. The hot melt flame-retardant polyester adhesive layer comprises 70-85 parts of hot melt flame-retardant polyester resin, 3-8 parts of adhesion promoter, 8-15 parts of composite flame retardant, 1-3 parts of anti-aging agent, 0.2-0.8 parts of crosslinking agent, 2-5 parts of temperature-resistant modified filler, and 10-20 parts of methyl ethyl ketone solvent.

[0026] Please see Figures 1-5 The present invention also provides a process for preparing a hot melt adhesive insulating film with high bonding strength, comprising the following steps: S100: Take the PET film and put it into a constant temperature oven for constant temperature drying. The composite flame retardant, anti-aging agent and temperature-resistant modified filler powder are sieved and set aside for later use. S200: The insulating ink is uniformly coated on the surface of the PET base film using a micro-gravure coating equipment, and then cured step by step through a three-stage gradient drying tunnel to obtain an ink transition layer. S300: Prepare hot melt adhesive liquid in a closed mixing tank and filter it; S400: The prepared hot melt adhesive liquid is conveyed to the doctor blade coating equipment, and the adhesive liquid is coated on the surface of the ink transition layer using a doctor blade; S500: The composite film coated with hot melt adhesive is sent into a segmented hot pressing equipment, with nitrogen gas continuously supplied for protection throughout the process. It undergoes composite treatment in three pressure and temperature zones in sequence: pre-pressing zone 110℃, 0.12MPa; main pressure zone 128℃, 0.25MPa; and stabilizing zone 95℃, 0.18MPa. S600: The finished film after hot pressing and lamination is transported to the air-cooled cooling channel for cooling and shaping. The ambient temperature in the channel is kept constant at 25°C, and the film passes through a cooling area with a length of 10m. S700: The cooled and shaped film is sent to the corona treatment equipment, the corona power is set to 20kW, and the surface of the hot melt adhesive layer is subjected to corona activation treatment. After the corona treatment is completed, the film is transferred to the room temperature standing area and left to stand continuously at room temperature for 30 hours. S800: The film body is cut by a slitting device after it has been left to stand, and the edge waste is removed. The slitting film body is then wound up by a constant tension winding device with the tension controlled at 5~8N. After winding, the finished product is tested for performance according to the product standard. After all indicators pass the test, the product is put into storage. The performance test includes bonding strength, voltage resistance, flame retardancy and high and low temperature cycling.

[0027] In this embodiment, the PET film is first dried in a constant-temperature oven, and the composite flame retardant, anti-aging agent, and temperature-resistant modified filler powder are sieved for later use. Then, an insulating ink is evenly coated onto the surface of the PET base film using a micro-gravure coating device, and cured step-by-step through a three-stage gradient drying tunnel to obtain an ink transition layer. Simultaneously, a hot melt adhesive solution is prepared in a sealed stirring tank and filtered. The prepared hot melt adhesive solution is then transported to a doctor blade coating device, where a doctor blade coats the adhesive solution onto the surface of the ink transition layer. The composite film with the hot melt adhesive layer is then sent to a segmented hot-pressing device, continuously protected by nitrogen gas throughout the process. It undergoes composite processing in three pressure and temperature zones: a pre-pressing zone at 110°C and 0.12MPa; a main press zone at 128°C and 0.25MPa; and a stabilizing zone at 95°C and 0.18MPa. Finally, the hot-pressed composite film is transported to a cooling channel for cooling and shaping, where the environment within the channel is... The temperature is kept constant at 25℃, and the film passes through a 10m long cooling zone. After cooling and shaping, the film is sent to a corona treatment device with a corona power of 20kW to activate the surface of the hot melt adhesive layer. After the corona treatment is completed, the film is transferred to a room temperature resting area and left to stand continuously at room temperature for 30 hours. Finally, the film is slit using a slitting device to remove edge waste, and the slit film is wound up using a constant tension winding device with the tension controlled at 5~8N. After winding, the finished product is tested for performance according to product standards. After all indicators pass the test, the product is put into storage. The performance tests include bonding strength, voltage resistance, flame retardancy, and high and low temperature cycling. Through the above process, the bonding strength between the layers of the hot melt adhesive insulation film and with the metal conductor is enhanced, avoiding delamination and peeling problems after repeated bending and high and low temperature cycling, thus improving the structural stability and durability of the cable.

[0028] S100: Take the PET film and put it into a constant temperature oven for drying. Then, sieve the composite flame retardant, anti-aging agent and temperature-resistant modified filler powder separately for later use.

[0029] In this embodiment, the PET film is placed in a constant temperature oven for drying, and the composite flame retardant, anti-aging agent, and temperature-resistant modified filler powders are sieved for later use. The specific process is as follows: S101: Select a PET insulating base film with a thickness of 18μm and place it inside a constant temperature oven; S102: Set the oven temperature to 85℃ and continuously dry the PET film at a constant temperature for 4 hours to remove moisture adsorbed on the surface and inside of the film. S103: Collect three types of powder raw materials: composite flame retardant, anti-aging agent, and temperature-resistant modified filler, and feed them into the screening equipment; S104: The powder raw material is screened using a 300-mesh standard sieve to remove large particles and material agglomerates. After screening, it is sealed and stored for later use.

[0030] In the above process, firstly, a PET insulating base film with a thickness of 18μm is selected and placed inside a constant temperature oven. The oven temperature is set to 85℃, and the PET film is continuously dried at a constant temperature for 4 hours to remove moisture adsorbed on the surface and inside of the film. Three types of powder raw materials, namely composite flame retardant, anti-aging agent, and temperature-resistant modified filler, are collected and put into a sieving device. Then, a 300-mesh standard sieve is used to sieve the powder raw materials to remove large particles and material agglomerates. After sieving, the materials are sealed and stored for later use. In the above process, the drying process avoids the generation of bubbles and pinholes in the subsequent coating, and the sieving process ensures the uniformity of the particle size of the powder raw materials, thus ensuring the quality of subsequent batching and film formation.

[0031] S200: The insulating ink is uniformly coated on the surface of the PET base film using a micro-gravure coating equipment, and then cured step by step through a three-stage gradient drying tunnel to obtain the ink transition layer.

[0032] In this embodiment, an insulating ink is uniformly coated onto the surface of a PET base film using a micro-gravure coating device, and then cured step-by-step through a three-stage gradient drying tunnel to obtain an ink transition layer. The specific process is as follows: S201: Start the micro-gravure coating equipment, feed the dried PET base film into the equipment at a uniform speed, control the equipment running speed to 10m / min, and uniformly coat the PET base film surface with insulating ink. S202: The ink-coated film is sequentially introduced into three gradient drying tunnels, with the tunnel temperatures set at 70℃, 90℃, and 110℃ respectively. The film stays in each drying tunnel for 15~20 seconds to complete the step-by-step curing. After the curing process is completed, a dense and strongly adhesive ink transition layer is formed on the surface of the PET base film.

[0033] In the above process, the microgravure coating equipment is first started, and the dried PET base film is fed into the equipment at a uniform speed. The operating speed of the equipment is controlled at 10m / min, and insulating ink is uniformly coated on the surface of the PET base film. Then, the ink-coated film is sequentially put into three gradient drying tunnels, with the tunnel temperatures set at 70℃, 90℃, and 110℃ respectively. The film stays in each drying tunnel for 15~20s to complete the step-by-step curing. After the curing process is completed, a dense and strongly adhesive ink transition layer is formed on the surface of the PET base film. In the above, gradient temperature curing can prevent local heat cracking of the ink and ensure that the ink transition layer has uniform thickness and stable performance.

[0034] S300: Prepare hot melt adhesive liquid in a closed mixing tank and filter it.

[0035] In this embodiment, the hot melt adhesive solution is prepared in a sealed stirring tank and then filtered. The specific process is as follows: S301: Add methyl ethyl ketone solvent and hot melt flame retardant polyester resin sequentially to a sealed stirring tank, heat to 60~75℃ and stir until the resin is completely dissolved; S302: Add adhesion promoter, composite flame retardant, temperature-resistant modified filler and anti-aging agent in sequence, and stir at high speed for 40-50 minutes to fully mix the materials; S303: Add crosslinking agent, switch to room temperature and low speed stirring for 10-15 minutes, and continuously purge nitrogen gas for protection throughout the stirring process; S304: The mixed adhesive solution is filtered using a 200-mesh filter to remove minute impurities and obtain a homogeneous hot melt adhesive solution.

[0036] In the above process, firstly, methyl ethyl ketone solvent and hot-melt flame-retardant polyester resin are added sequentially to a sealed stirring tank, and the temperature is raised to 60~75℃ and stirred until the resin is completely dissolved; then, adhesion promoter, composite flame retardant, temperature-resistant modified filler, and anti-aging agent are added in sequence, and the mixture is stirred at high speed for 40~50 minutes to fully mix the materials; then, crosslinking agent is added, and the mixture is stirred at low speed at room temperature for 10~15 minutes, with nitrogen gas continuously introduced for protection throughout the stirring process; then, the mixed adhesive solution is filtered using a 200-mesh filter to remove tiny impurities, resulting in a homogeneous hot-melt adhesive solution. In the above process, the nitrogen atmosphere can prevent high-temperature oxidation of materials and premature failure of crosslinking agent, and the filtration process further improves the purity of the adhesive solution.

[0037] S400: The prepared hot melt adhesive is conveyed to the doctor blade coating equipment, and the doctor blade is used to coat the adhesive onto the surface of the ink transition layer.

[0038] In this embodiment, the prepared hot melt adhesive is conveyed to a doctor blade coating device, and the adhesive is coated onto the surface of the ink transition layer using a doctor blade. The specific process is as follows: S401: The filtered hot melt adhesive liquid is conveyed to the material tank of the doctor blade coating equipment; S402: Feed the composite substrate with the ink transition layer into the coating equipment, and set the equipment operating speed to 8m / min; S403: The coating amount is precisely controlled by a doctor blade to coat the surface of the ink transition layer with hot melt adhesive, and the dry film thickness is 20μm.

[0039] In the above process, the filtered hot melt adhesive liquid is first transported to the material tank of the doctor blade coating equipment; then the composite substrate with the ink transition layer is fed into the coating equipment, and the equipment running speed is set to 8m / min; then the coating amount is precisely controlled by the doctor blade, and the hot melt adhesive liquid is coated on the surface of the ink transition layer, with a dry film thickness of 20μm. In the above process, the precise control of the coating speed and the thickness of the adhesive layer can ensure that the appearance and performance of the hot melt adhesive layer meet the standards.

[0040] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0041] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A hot melt adhesive insulating film with high bonding strength, characterized in that, It includes a PET film, an ink layer, and a hot-melt flame-retardant polyester adhesive layer. The hot-melt flame-retardant polyester adhesive layer includes 70-85 parts of hot-melt flame-retardant polyester resin, 3-8 parts of adhesion promoter, 8-15 parts of composite flame retardant, 1-3 parts of anti-aging agent, 0.2-0.8 parts of crosslinking agent, 2-5 parts of temperature-resistant modified filler, and 10-20 parts of methyl ethyl ketone solvent.

2. A process for preparing a high-adhesion-strength hot melt adhesive insulating film, such as the high-adhesion-strength hot melt adhesive insulating film as described in claim 1, characterized in that, Includes the following steps: Take the PET film and put it into a constant temperature oven for drying. Then, sieve the composite flame retardant, anti-aging agent and temperature-resistant modified filler powder separately for later use. Insulating ink is uniformly coated onto the surface of a PET base film using a micro-gravure coating machine, and then cured step by step through a three-stage gradient drying tunnel to obtain an ink transition layer. Prepare the hot melt adhesive solution in a sealed mixing tank and then filter it; The prepared hot melt adhesive is conveyed to the doctor blade coating equipment, and the doctor blade is used to coat the adhesive onto the surface of the ink transition layer. The composite film coated with hot melt adhesive is sent into a segmented hot pressing equipment, with nitrogen gas continuously supplied for protection throughout the process; The finished film after hot pressing is transported to an air-cooled cooling channel for cooling and shaping. After cooling and shaping, the film is sent to a corona treatment device with a corona power of 20kW to activate the surface of the hot melt adhesive layer. After the corona treatment is completed, the film is transferred to a room temperature resting area and left to stand continuously at room temperature for 30 hours. The membrane body, after being left to stand, is cut using a slitting device to remove edge waste. The slitting membrane body is then wound up using a constant tension winding device, with the tension controlled at 5~8N. After winding, the finished product is tested for performance according to the product standard. Once all indicators pass the test, the membrane body is put into storage.

3. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the steps of taking PET film and sending it into a constant temperature oven for drying, and sieving the composite flame retardant, anti-aging agent and temperature-resistant modified filler powder for later use: Select a PET insulating base film with a thickness of 18μm and place it inside a constant temperature oven; Set the oven temperature to 85℃ and continuously dry the PET film at a constant temperature for 4 hours to remove moisture adsorbed on the surface and inside of the film. Collect three types of powder raw materials: composite flame retardant, anti-aging agent, and temperature-resistant modified filler, and feed them into the screening equipment; The powder raw materials are screened using a 300-mesh standard sieve to remove large particles and material agglomerates. After screening, the materials are sealed and stored for later use.

4. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the step of uniformly coating insulating ink onto the surface of a PET base film using a micro-gravure coating machine and then curing it step by step through a three-stage gradient drying tunnel to obtain an ink transition layer: Start the microgravure coating equipment, feed the dried PET base film into the equipment at a uniform speed, control the equipment running speed to 10m / min, and uniformly coat the PET base film surface with insulating ink. The ink-coated film is sequentially introduced into three gradient drying tunnels, with the tunnel temperatures set at 70℃, 90℃, and 110℃ respectively. The film remains in each drying tunnel for 15-20 seconds to complete the step-by-step curing. After the curing process is completed, a dense and strongly adhesive ink transition layer is formed on the surface of the PET base film.

5. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the step of preparing the hot melt adhesive solution in a closed mixing tank and filtering it: Add methyl ethyl ketone solvent and hot-melt flame-retardant polyester resin sequentially to a sealed stirring vessel, and heat to 60~75℃ and stir until the resin is completely dissolved. Add the adhesion promoter, composite flame retardant, temperature-resistant modified filler, and anti-aging agent in sequence, and stir at high speed for 40-50 minutes to fully mix the materials; Add crosslinking agent, switch to room temperature and low speed stirring for 10-15 minutes, and continuously purge nitrogen gas for protection throughout the stirring process. The mixed adhesive solution was filtered using a 200-mesh filter to remove minute impurities, resulting in a homogeneous hot melt adhesive solution.

6. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the step of conveying the prepared hot melt adhesive to the doctor blade coating equipment and using a doctor blade to coat the adhesive onto the surface of the ink transition layer: The filtered hot melt adhesive liquid is conveyed into the material tank of the doctor blade coating equipment; The composite substrate with the ink transition layer is fed into the coating equipment, and the equipment operating speed is set to 8m / min. The coating amount is precisely controlled by a doctor blade, and hot melt adhesive is applied to the surface of the ink transition layer, with a dry film thickness of 20μm.

7. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the step of feeding the composite film coated with hot melt adhesive into the segmented hot pressing equipment, nitrogen gas is continuously supplied for protection throughout the process: The pressure is applied in three pressure and temperature zones: pre-pressure zone 110℃, 0.12MPa; main pressure zone 128℃, 0.25MPa; and stabilizing zone 95℃, 0.18MPa.

8. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, In the step of conveying the finished film after hot pressing lamination to the air-cooling channel for cooling and shaping: The ambient temperature inside the channel is kept constant at 25°C, and the membrane passes through a cooling zone with a length of 10m.

9. The preparation process of the high-bonding-strength hot melt adhesive insulating film as described in claim 2, characterized in that, The process involves using a slitting device to cut the settled film, removing edge waste, and then using a constant tension winding device to wind the slit film, controlling the tension at 5-8N. After winding, the finished product undergoes performance testing according to product standards. Only after all indicators pass the inspection is the film put into storage. Performance testing includes bond strength, voltage resistance, flame retardancy, and high and low temperature cycling.

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