A drying device and production system of a polyimide composite film

Abstract

The application discloses a kind of polyimide composite film drying device and production system, polyimide composite film drying device includes for the polyimide substrate film surface coating emulsion formed by polyimide composite film passing and carrying out microwave heating drying microwave heating area and for the polyimide composite film after microwave heating drying passing and carrying out infrared heating drying infrared heating area, the microwave heating area and infrared heating area are sequentially arranged and mutually communicated, and polyimide composite film sequentially passes the microwave heating area and infrared heating area along vertical direction.The application further discloses a kind of production system with above-mentioned polyimide composite film drying device.The application can be used to dry PI / PTFE composite film, and drying efficiency is high, drying effect is good, can guarantee the quality of final composite film product.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing technology, specifically to a drying device and production system for composite films. Background Technology

[0002] PI / PTFE composite films possess excellent performance and can be used in cables requiring high temperature resistance. However, mass production of wide and long roll PI / PTFE composite films is challenging, and corresponding production equipment is rarely reported. As an important polymer material, PTFE dispersion resin is widely used in military, electronics, chemical, and machinery industries, and is also a raw material for PI / PTFE composite film production. The production of PI / PTFE composite films involves coating PTFE dispersion resin onto a PI substrate film and then heating and drying it. However, currently, there are several technical problems with the heating, drying, stirring, conveying, and coating processes of PTFE dispersion resin, which seriously affect the final product quality of the PI / PTFE composite film.

[0003] For the drying of composite films, the curing of the PTFE coating requires multiple stages, including dehydration and high-temperature baking and sintering. Traditional drying ovens are typically single-temperature zones with uneven hot air circulation, resulting in large transverse temperature differences in the film. This easily leads to problems such as the newly coated PTFE emulsion peeling off and powdering. Reducing the hot air velocity results in the coating being heated solely by heat transfer, leading to large transverse temperature differences, low drying efficiency, and limited production speed. Furthermore, uneven evaporation rates of moisture and additives cause internal stress concentration, resulting in problems such as glue particles, blistering, and warping on the coating surface, affecting the uniformity of PTFE crystallization and ultimately impacting product adhesion and applications. Excessive drying can cause surface cracking and blistering. Due to the narrow PTFE crystallization temperature process window, the uniformity of the temperature field in the horizontal direction is even more critical when drying wide-width PTFE emulsion coatings. In addition, in existing drying equipment, the composite film to be dried is transported horizontally into the drying unit. Due to its own weight, the horizontally transported composite film naturally sags, and the sag is prone to scratching the equipment surface, causing defects such as damage.

[0004] For the raw material supply, transportation, and coating process of PTFE emulsion, since PTFE emulsion is a high-solids-content suspension prone to demulsification, if the shear rate is too high during the stirring or dispersion transportation of PTFE dispersion resin, it will accelerate the separation of the emulsion and lead to demulsification. Existing pumps commonly used in technology, such as gear pumps, centrifugal pumps, and vacuum pumps, all have certain mechanical pulses, mechanical stirring, and pipeline friction and collision, which can cause material demulsification, resulting in irreversible product quality risks. This leads to fluctuations in the final coating thickness and inconsistent performance, affecting coating quality. During coating, the low viscosity of PTFE emulsion leads to uneven extrusion, making it difficult to ensure the uniformity of the lateral thickness after coating to the substrate. Material backflow after shear metering (wire bar, doctor blade) is more likely to cause demulsification. Furthermore, commonly used wire bar and microgravure coating methods are difficult to form an extremely uniform and defect-free initial wet film at high speeds, easily resulting in defects such as granules, cracks, and fisheyes.

[0005] Therefore, there is currently a lack of a drying device and production system for drying polyimide composite films that can solve the aforementioned technical problems, so as to achieve stable and efficient production of high-performance PI / PTFE composite films. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a drying device and production system for polyimide composite films that can be used to dry PI / PTFE composite films with high drying efficiency, good drying effect and ensure the quality of the final composite film product.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0008] A drying apparatus for a polyimide composite film includes a microwave heating zone for passing through and drying a polyimide composite film formed by coating an emulsion on the surface of a polyimide substrate film using microwave heating, and an infrared heating zone for passing through and drying the microwave-dried polyimide composite film using infrared heating. The microwave heating zone and the infrared heating zone are arranged sequentially and connected to each other, and the polyimide composite film passes through the microwave heating zone and the infrared heating zone sequentially in a vertical direction. The drying device of this invention includes a microwave heating zone and an infrared heating zone, providing excellent drying and curing effects. After coating the polyimide substrate film with an emulsion, the resulting polyimide composite film moves vertically into the microwave heating zone. Under microwave heating, the film gains strength as moisture is dried. It then enters the infrared heating zone for further heating and curing. Through the synergistic drying of microwave and infrared heating, the microwave heating zone dries the moisture in the coated emulsion (e.g., PTFE) in a very short time, achieving rapid shaping. The infrared heating zone ensures uniform film surface temperature, providing an ideal thermal environment for the gradient curing of coatings such as PTFE coatings, avoiding internal stress, warping, and bubbles, and improving the adhesion between the coating and the substrate, as well as the overall performance of the final product. The drying device of this invention uses microwave heating at the front end to quickly remove most of the moisture, followed by high-temperature infrared curing and sintering, ensuring the uniformity of the emulsion (e.g., PTFE film). The synergistic heating of microwave and infrared heating can meet the requirements of high-speed coating, such as single-coating at 1-15 micrometers, ensuring uniform drying and improving production line efficiency.

[0009] Preferably, the aforementioned drying device for the polyimide composite film further includes a reversing component for changing the film's forward direction. This reversing component is located between the microwave heating zone and the infrared heating zone, ensuring the polyimide composite film's forward direction remains vertical and opposite in both zones. This invention employs a longitudinal conveying method, avoiding defects such as scratches caused by the film scraping the equipment surface due to its own weight. Newly coated emulsions lack adhesive strength and cannot be scraped. Lateral conveying requires film support, necessitating support rollers. However, laterally conveyed films are prone to scraping against these rollers, leading to film and emulsion falling off. In this invention, the polyimide composite film is conveyed vertically, with the reversing component providing longitudinal support. After exiting the microwave heating zone, the polyimide composite film is reversed by the reversing component, at which point it possesses sufficient adhesive strength, making it less prone to scraping against the equipment. Even if scraping occurs, it is less likely to severely affect the film, thus improving product quality.

[0010] Preferably, in the aforementioned drying device for polyimide composite film, the microwave heating zone and the infrared heating zone are vertically arranged on both sides of the drying device, and the reversing assembly is located at the top of the drying device and connected to the microwave heating zone and the infrared heating zone. The reversing assembly includes a reversing roller and a reversing roller drive, and the reversing roller drive is connected to the reversing roller. The drying device adopts a vertical structure with a small footprint. The microwave heating zone and the infrared heating zone are located on the left and right sides, and the reversing assembly is located at the top of the microwave heating zone and the infrared heating zone to change the film's vertical movement from bottom to top to top to bottom, thereby forming a three-dimensional space in the vertical direction, making the film more evenly heated. The film's movement direction is inverted U-shaped, that is, the film first passes through the microwave heating zone from bottom to top, then changes its movement direction through the reversing assembly, and then passes through the infrared heating zone from top to bottom for drying.

[0011] Preferably, in the aforementioned drying device for polyimide composite films, the microwave heating zone includes multiple microwave sub-heating zones arranged sequentially along the direction of travel of the polyimide composite film. Each microwave sub-heating zone includes a pair of U-shaped microwave insulation covers. The pair of microwave insulation covers are arranged opposite each other to form a microwave heating cavity. A microwave drying channel for the polyimide composite film to pass through is provided between the pair of microwave insulation covers. The microwave insulation covers are also equipped with magnetrons, thermocouples, and suction pipes for extracting moisture escaping from the microwave heating cavity. This invention uses a pair of U-shaped microwave insulation covers to form a microwave heating cavity, with a microwave drying channel between them. The U-shaped structure design ensures uniform temperature inside the cavity. The U-shaped microwave insulation covers concentrate heat at the top and surrounding areas like a greenhouse, reducing heat loss from the sides and creating a stable thermal environment, thus improving the insulation effect. The U-shaped opening design allows microwaves to enter more smoothly from the sides, forming a three-dimensional heating effect with the top microwaves, avoiding uneven heating between the center and edges of the film. Through reasonable cavity structure design and edge treatment, uniform microwave field distribution is ensured and leakage is prevented. The magnetron utilizes the dielectric heating principle to generate heat through high-speed vibration and friction of water molecules, achieving uniform heating of the entire thin-film emulsion coating and significantly improving initial drying efficiency. An extraction pipe on the microwave insulation cover directly and quickly removes any escaping moisture, preventing condensation and backflow on the film surface. The microwave heating zone dries the coated emulsion, such as PTFE, in a very short time, achieving rapid setting and uniform heating from the inside out. This results in a smooth and uniform product surface, avoiding the uneven surface caused by traditional hot air drying and the "particle" defects and air marks caused by hot air blowing onto the film surface. This allows for higher production line speeds. Furthermore, because microwaves act directly on the heated material, energy loss from traditional air-conduction heating is reduced, greatly improving heating efficiency and resulting in significant energy savings.

[0012] Preferably, in the aforementioned drying device for the polyimide composite film, the microwave insulation cover is further provided with a magnetron, a thermocouple, and an extraction pipe for removing moisture escaping from the microwave heating cavity. The microwave insulation cover includes a first insulation plate, a second insulation plate, and a third insulation plate. The first and second insulation plates are spaced apart from each other. The two sides of the third insulation plate are connected to the first and second insulation plates respectively, forming a U-shaped structure. The magnetron is located at the connection points between the third insulation plate and the first and second insulation plates, and between the third insulation plate and the second insulation plate. The thermocouple and the extraction pipe are located on the third insulation plate and connected to the microwave heating cavity. Specifically, the first and second insulation plates form two sides of the U-shaped structure, the third insulation plate forms the bottom side of the U-shaped structure, and the magnetron is located at the corner of the U-shaped structure. For a microwave heating cavity composed of a pair of microwave insulation covers, the magnetron is located at the corner of the microwave heating cavity, and the thermocouple and the extraction pipe pass through the third insulation plate. The magnetron, thermocouple, and evacuation tube work together to achieve precise and uniform heating and drying within the microwave heating cavity and timely removal of moisture. Placing the magnetron in a corner allows for control of the flow direction, thus reducing temperature fluctuations.

[0013] Preferably, in the aforementioned drying apparatus for the polyimide composite film, the infrared heating zone comprises multiple infrared sub-heating zones arranged sequentially along the direction of travel of the polyimide composite film. Each infrared sub-heating zone has several infrared heating units on both sides, and an infrared drying channel is provided between the infrared heating units on both sides for the polyimide composite film to pass through. As the film passes through the infrared drying channel, the infrared heating units on both sides of the film uniformly heat the film, ensuring a uniform film surface temperature within the same infrared sub-heating zone. This effectively avoids internal stress, warping, and bubbles, significantly improving the adhesion between the coating and the substrate, and enhancing the overall performance of the final product.

[0014] Preferably, in the aforementioned drying device for polyimide composite film, the infrared heating units on both sides of each infrared sub-heating zone are arranged at intervals along the horizontal direction of the polyimide composite film. Each infrared heating unit includes a heat-insulating cover plate, an adjusting screw, and an infrared heating plate. The heat-insulating cover plate is fixedly installed and has fixing holes that cooperate with the adjusting screw. One end of the adjusting screw is detachably and fixedly connected to the heat-insulating cover plate, and the other end is fixedly connected to the infrared heating plate. The infrared heating plate has multiple infrared heating blocks arranged alternately and at intervals. Multiple independently controlled infrared heating units are set as heating points along the horizontal direction of the film. Simultaneously, the special structure of the infrared heating units allows for multi-angle adjustment of the heat source height to achieve better heating and drying effects, covering the horizontal direction of the polyimide film. This ensures uniform temperature within the drying device and reduces the impact of temperature differences at different locations along the horizontal direction. In actual production, samples can be taken from the furnace-produced samples, such as PI / PTFE composite film samples. Based on the coating state of the PTFE surface and the peel strength performance analysis after sampling, for locations that do not meet the requirements, the vertical height and angle of the infrared heating plate can be adjusted online (by adjusting the screw). For example, if the micro-melting peel strength is low, the distance between the infrared heating plate and the film surface can be reduced, thereby ensuring the uniformity of the peel strength of the product after coating in the horizontal direction. Furthermore, multiple infrared heating blocks on the infrared heating plate are arranged in a staggered and close manner to further improve the heating uniformity of the material.

[0015] In the aforementioned drying apparatus for polyimide composite films, preferably, the outermost infrared heating unit in each infrared sub-heating zone along the horizontal direction of the film is inclined towards the film. The temperature of each infrared heating unit in the same infrared sub-heating zone is set to maintain a uniform film surface temperature in the infrared drying channel within that sub-heating zone. Actual production has revealed that the temperature on the outermost side along the horizontal direction of the film is often lower than the temperature on the inner side. This leads to temperature inhomogeneity between the sides and the middle of the film within the same infrared sub-heating zone, affecting the final product performance. Inclining the outermost infrared heating unit towards the film effectively solves this problem, maintaining a uniform film surface temperature in the infrared drying channel within the same sub-heating zone and improving product quality.

[0016] Preferably, the aforementioned drying device for the polyimide composite film includes, along the film's advancing direction, a preheating zone, a drying and evaporation zone, a melting zone, a high-temperature sintering zone, a molding and cooling zone, and a tail-end cooling zone. The microwave heating zone and infrared heating zone of the drying device are divided into six temperature zones based on the characteristics of the process temperature. Utilizing the independent temperature control characteristics of the microwave and infrared heating zones, the temperature is precisely controlled independently in different zones according to the product process, meeting the heating requirements of product production and ensuring the uniformity of the film surface temperature, thereby further improving product quality.

[0017] Preferably, the drying device for the aforementioned polyimide composite film is equipped with independent exhaust gas emission systems and air systems for both the microwave sub-heating zone and the infrared sub-heating zone, and the air volume is intelligently controlled to promptly remove the dried moisture.

[0018] As a general technical concept, the present invention also provides a production system for a polyimide composite film, comprising a fluorinated emulsion constant pressure feeding device, an emulsion coating device, a substrate unwinding device, and a drying device for the aforementioned polyimide composite film. The emulsion coating device is connected to the output ends of both the fluorinated emulsion constant pressure feeding device and the substrate unwinding device, and the input end of the drying device is connected to the output end of the emulsion coating device. In the polyimide composite film production system of the present invention, the substrate unwinding device, the emulsion coating device, and the drying device are arranged sequentially along the film travel direction. The emulsion coating device, as a device for forming the coated composite film, is also connected to the fluorinated emulsion constant pressure feeding device and coats the emulsion onto the polyimide substrate film. The polyimide composite film production system of the present invention uses a polyimide film as a substrate, which is fed from a substrate unwinding device to an emulsion coating device. The emulsion coating device is connected to a fluorinated emulsion constant pressure feeding device, which can provide a stable and non-degrading high-quality emulsion, effectively controlling problems such as emulsion degradation caused by shearing, ensuring that the concentration and viscosity of the emulsion are extremely uniform throughout the coating process, without bubbles or agglomeration, thus ensuring the uniformity and consistency of the coating. After the emulsion is coated on the polyimide film, it enters a drying device for drying.

[0019] Preferably, the aforementioned polyimide composite film production system further includes a winding device, the input end of which is connected to the output end of the drying device. Specifically, the input end of the microwave heating zone of the drying device is connected to the output end of the emulsion coating device, and the input end of the winding device is connected to the output end of the infrared heating zone. The winding device is located downstream of the drying device. After the polyimide composite film is dried by the drying device, it is finally wound up by the winding device to obtain a high-performance polyimide composite film.

[0020] In the aforementioned polyimide composite film production system, preferably, the fluorinated emulsion constant pressure feeding device includes a replenishment tank and an emulsion tank. A replenishment pipe is provided between the replenishment tank and the emulsion tank for supplying emulsion to the emulsion tank through the pressure difference between the replenishment tank and the emulsion tank. The emulsion tank is provided with a compressed gas inlet pipe and a compressed gas outlet pipe. The fluorinated emulsion constant pressure feeding device also includes a controller for controlling the pressure inside the emulsion tank to remain substantially constant by controlling the compressed gas flow rate of the compressed gas inlet pipe and the compressed gas outlet pipe. The outlet of the emulsion tank is also provided with a feeding pipe for supplying emulsion to the emulsion coating device through the pressure difference between the emulsion tank and the emulsion coating device. The emulsion is used to coat the surface of the substrate film to form a coated composite film. Neither the replenishment pipe nor the feeding pipe is equipped with a delivery pump.

[0021] The fluorinated emulsion constant pressure feeding device proposed in this invention sets up a replenishment tank and an emulsion tank, and provides a compressed gas inlet pipe and a compressed gas outlet pipe at the top of the emulsion tank. Compressed gas can be introduced into or discharged into the emulsion tank to regulate the pressure inside the emulsion tank, so that the pressure inside the emulsion tank is maintained at a basically constant pressure. After the pressure of the emulsion tank is set by the controller, the pressure can be precisely controlled and kept constant at ±0.01MPa. The replenishment pipe delivers the emulsion through the pressure difference between the replenishment tank and the emulsion tank, and the feeding pipe delivers the emulsion through the pressure difference between the emulsion tank and the emulsion coating device. This can avoid shearing conveying and maintain the stability of the emulsion. Since the emulsion tank is the core hub for both front-end replenishment and back-end feeding, and the emulsion material is transported via pressure difference to maintain stability, the pressure stability of the emulsion tank directly affects the stability of the emulsion transport and state in the replenishment and feeding pipes. By controlling the slow extrusion of the emulsion material under constant pressure, problems such as emulsion breakage due to shearing can be effectively controlled, ensuring that various emulsions, such as PTFE emulsions, have extremely uniform concentration and viscosity throughout the coating process, with no bubbles or agglomeration, thus guaranteeing the uniformity and consistency of the coating from the source. Furthermore, in the design of this invention, since the replenishment tank, emulsion tank, and emulsion coating device are all interconnected as a whole, the entire raw material supply and conveying system can be controlled in an integrated manner through the air pressure regulation and control device on the emulsion tank. This not only simplifies the structure and reduces the number of components, but also better maintains the stability of the entire feeding system, thereby better ensuring the quality of the emulsion during the coating process. Compared to traditional manual feeding processes, which are labor-intensive, pose a risk of secondary emulsion contamination, and suffer from localized demulsification and large replenishment errors due to instantaneous disturbances in the emulsion during addition, the aforementioned structure comprehensively improves work efficiency and reduces operator workload through an integrated electronically controlled switching system for emulsion supply to the tank. The sealed emulsion transport throughout its entire path avoids contamination and instantaneous disturbances, and precise control of the replenishment level enhances material stability. Since no pumps are installed on the conveying pipelines, shear transport of the emulsion is effectively avoided, ensuring a stable emulsion state.

[0022] In the aforementioned polyimide composite film production system, preferably, the compressed gas inlet pipe is equipped with an inlet proportional valve, the compressed gas outlet pipe is equipped with an outlet proportional valve, and the emulsion tank is equipped with a pressure gauge for monitoring the pressure inside the emulsion tank. The inlet proportional valve, outlet proportional valve, and pressure gauge are all connected to the controller. When the pressure gauge detects a change in the pressure inside the emulsion tank, the controller adjusts the inlet proportional valve and outlet proportional valve to maintain a constant pressure inside the emulsion tank, thereby ensuring stable emulsion delivery through the replenishment pipe and the feed pipe. When the gas pressure inside the emulsion tank changes, it drives the inlet proportional valve, outlet proportional valve, and other components to move for adjustment. When the pressure is too low, compressed gas is introduced through the inlet proportional valve; when the pressure is too high, some gas is discharged through the outlet proportional valve. By maintaining a constant pressure in the emulsion tank, stable emulsion delivery is achieved.

[0023] In the aforementioned polyimide composite film production system, preferably, the replenishment pipe is equipped with a replenishment control valve, and the emulsion tank is equipped with a level gauge for monitoring the emulsion level inside the tank. Both the replenishment control valve and the level gauge are signal-connected to the controller. When the level gauge detects a change in the emulsion level inside the tank, the controller adjusts the replenishment control valve to control the emulsion level within a preset range. The level gauge monitors changes in the emulsion level inside the tank. When the level is at the lower limit, the controller opens the replenishment control valve, and the emulsion in the replenishment tank replenishes the tank through the replenishment pipe. When the level is at the upper limit, the controller closes the replenishment control valve, and the replenishment tank stops replenishing, thus controlling the emulsion level within the tank within the preset range. By simultaneously monitoring changes in the gas pressure and liquid level inside the tank, the controller can more accurately and automatically adjust the gas pressure inside the tank, keeping the outlet and inlet pressures of the emulsion tank constant, thereby stabilizing the emulsion flow rate and state.

[0024] In the aforementioned polyimide composite membrane production system, preferably, the feed pipe is equipped with a Y-type filter, a rotor flow meter, and a needle valve for precisely controlling the emulsion flow rate delivered to the emulsion coating device. The Y-type filter is located upstream of the needle valve, and the rotor flow meter is located downstream of the needle valve. The Y-type filter prevents large particulate impurities from causing defects on the membrane surface. The rotor flow meter can be used for result feedback; currently, the coating amount can be obtained through calculation. The rotor flow meter facilitates manual inspection for flow fluctuations and also facilitates remote data monitoring. The needle valve can be adjusted to obtain the required flow rate, providing easy adjustment. Through the minute displacement of the needle-shaped valve core, milliliter-level flow control is achieved to meet the feeding requirements of different coating processes. The controller maintains a relatively constant pressure in the emulsion tank, acting as a power source, while the needle valve is a downstream control component. The coordinated control of these two components ensures stable transport and coating of the emulsion at the required flow rate.

[0025] In the aforementioned polyimide composite film production system, preferably, the emulsion coating device includes a slit-type die head for uniformly coating the emulsion onto the substrate film. The slit-type die head includes mating lip plates, and the lip plates are equipped with a digitally displayed micrometer screw for precisely adjusting the lip spacing. The emulsion coating device also includes a back pressure roller, with the slit-type die head positioned above the back pressure roller. The slit-type die head has a pre-set die head gap. The lip plates are squeezed using the digitally displayed micrometer screw adjustment device, and the lip spacing is adjusted in real-time based on the coating thickness, maintaining coating accuracy within a very small tolerance range. This ensures the uniformity of the overall thickness of the coated film, meeting the coating requirements for films of different widths. The digitally displayed micrometer screw allows for precise adjustment of the slit width of the slit-type die head's lip plates and the relative position of the back pressure roller, thereby precisely adjusting the discharge volume at each position. There is no material shearing or backflow, solving the problem of poor wettability of PTFE emulsion on PI film. This achieves ultra-thin, uniform, and defect-free coating at high speeds, significantly improving product yield.

[0026] In the aforementioned polyimide composite film production system, preferably, the compressed gas is a high-quality compressed gas with a particle size ≤0.3μm, a dew point ≤-20℃, and an oil content ≤0.01mg / m³. 3 Since oil, water vapor, dust, and other contaminants can affect the control precision of electrical components, using high-quality compressed gas can improve the control precision of the pressure inside the emulsion tank, ensuring a constant pressure inside the emulsion tank, thereby guaranteeing the stability of emulsion delivery and coating.

[0027] In the aforementioned polyimide composite film production system, preferably, the replenishment tank is equipped with a compressed gas inlet and a vent. The pressure of the replenishment tank can be adjusted via the compressed gas inlet and vent, and this, combined with the pressure control of the emulsion tank, ensures stable replenishment of the emulsion tank.

[0028] In the above-mentioned polyimide composite film production system, preferably, the emulsion tank is equipped with a cantilever micro-stirrer, which has three layers of single propeller blades, so as to achieve gentle stirring of high solids content PTFE emulsion and prevent sedimentation and flocculation.

[0029] In the aforementioned polyimide composite film production system, preferably, the emulsion tank and all conveying pipelines, such as the replenishment pipe and the feed pipe, are equipped with a jacketed circulating temperature control system. The jacketed circulating temperature control system precisely controls the emulsion temperature at 25±1℃, ensuring the stability of the emulsion viscosity and its viscosity state.

[0030] The fluorinated emulsion constant pressure feeding device in the production system of this invention provides continuous and stable feeding. It utilizes a replenishment tank and an emulsion tank, with the emulsion tank pressure maintained constant by a controller. High-gloss pressure vessels and pipelines are employed, and pressure control and regulation devices such as pressure transmitters, pressure regulating valves, and pressure gauges are added. Gas pressure changes drive the movement of components such as the compressed gas inlet pipe and compressed gas exhaust pipe valve core, automatically adjusting the gas flow rate to maintain a constant outlet or inlet pressure and stable material outlet flow rate. This achieves fully automatic and uninterrupted feeding. A precision needle valve and rotor flowmeter are installed on the material outlet feeding pipe to achieve precise control of the feeding flow rate, avoiding production line shutdowns caused by unstable emulsion shear. Constant pressure control and slow material extrusion effectively control problems such as demulsification caused by shear, ensuring extremely uniform concentration and viscosity of the PTFE emulsion throughout the coating process, free of bubbles and agglomeration. This guarantees the uniformity and consistency of the coating from the source, adapting to different continuous production needs and improving production efficiency.

[0031] The production system of this invention can be used for polytetrafluoroethylene (PTFE) emulsion coating on the surface of polyimide (PI) films. Through the collaborative innovative design of devices such as the constant pressure feeding device for fluorinated emulsions, the emulsion coating device, and the drying device, highly stable delivery, ultra-uniform coating, and precise gradient curing of emulsions, especially PTFE emulsions, are achieved. This results in a high-quality composite material with uniform coating, strong adhesion, and no defects, suitable for preparing high-performance PI / PTFE composite films. However, the production system of this invention is not limited to the preparation of PTFE emulsion-coated composite films; it can also be used simultaneously for the feeding, coating, and drying of other emulsions, including multiple coating processes. This production system has the advantages of intelligence and high efficiency. The entire production system is integrated and controlled through a central control system, achieving continuous, automated, and highly efficient production, suitable for the industrial manufacturing of high-end electronic materials.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] 1. The drying device of this invention includes a microwave heating zone and an infrared heating zone, providing excellent drying and curing effects. After coating the polyimide substrate film with an emulsion, the resulting polyimide composite film moves vertically into the microwave heating zone. Under microwave heating, the film gains strength as moisture is dried. It then enters the infrared heating zone for further heating and curing. Through the synergistic drying of microwave and infrared heating, the microwave heating zone can quickly dry the moisture in the coated emulsion (e.g., PTFE), achieving rapid shaping. The infrared heating zone ensures uniform film surface temperature, providing an ideal thermal environment for the gradient curing of coatings such as PTFE coatings, avoiding internal stress, warping, and bubbles, and improving the adhesion between the coating and the substrate, as well as the overall performance of the final product. The drying device of this invention uses microwave heating at the front end to quickly remove most of the moisture, followed by high-temperature infrared curing and sintering, ensuring the uniformity of the emulsion (e.g., PTFE film). The synergistic heating of microwave and infrared heating can meet the drying uniformity requirements of high-speed coating, such as single-coating at 1-15 micrometers, improving production line efficiency.

[0034] 2. The production system of this invention has excellent drying and curing effects. It adopts multi-level precise temperature control. The microwave heating zone can dry the moisture of the coated emulsion, such as PTFE, in a very short time, achieving rapid shaping. The infrared heating unit in the infrared heating zone can be independently controlled and adjusted in terms of installation position and angle, ensuring the uniformity of temperature along the horizontal direction of the drying device. This provides an ideal thermal environment for the gradient curing of coatings such as PTFE coatings. The transverse temperature difference of the film is less than ±1℃, effectively avoiding internal stress, warping, and bubbles, and significantly improving the adhesion between the coating and the substrate and the overall performance of the final product.

[0035] 3. The polyimide composite film production system of the present invention, wherein the polyimide film as the substrate is fed from the substrate unwinding device to the emulsion coating device, the emulsion coating device is connected to the fluorinated emulsion constant pressure feeding device, the fluorinated emulsion constant pressure feeding device can provide it with a high-quality emulsion that is stable and does not break the emulsion, effectively controlling the problem of emulsion breaking caused by shearing, ensuring that the concentration and viscosity of the emulsion are extremely uniform throughout the coating process, without bubbles or agglomeration, thus ensuring the uniformity and consistency of the coating. After the emulsion is coated on the polyimide film, it enters the drying device for drying to obtain a high-performance polyimide composite film. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the drying device for the polyimide composite film in Example 1.

[0037] Figure 2 This is a schematic diagram of the microwave heating zone in Example 1.

[0038] Figure 3 This is a schematic diagram of the infrared heating zone in Example 1.

[0039] Figure 4 yes Figure 3 A schematic diagram of the layout of the infrared heating unit along direction A (only a portion of the infrared heating unit on one side of an infrared sub-heating area is shown).

[0040] Figure 5 This is a schematic diagram of the infrared heating unit in Example 1.

[0041] Figure 6 This is a schematic diagram of the infrared heating unit from another perspective in Embodiment 1.

[0042] Figure 7 This is a schematic diagram of the layout of the outermost infrared heating unit along the horizontal direction of the membrane in Example 1 (only a portion of the infrared heating unit is shown).

[0043] Figure 8 This is a schematic diagram of the production system for the polyimide composite film of Example 2.

[0044] Figure 9 This is a schematic diagram of the constant pressure feeding device for fluorinated emulsion in Example 2.

[0045] Figure 10 This is a cross-sectional view of the slit-type mold head in Example 2.

[0046] Figure 11 This is a picture showing the inside of the fluorinated emulsion filter clean and free of demulsification after the constant pressure feeding device for fluorinated emulsion has been running for 100 hours.

[0047] Figure 12 The image shows the emulsion separating and breaking down on a filter screen after 12 hours of pumping emulsion using existing technology.

[0048] Figure 13 The image shows a coated composite film product prepared using an emulsion supplied by a fluorinated emulsion constant pressure feeding device.

[0049] Figure 14 This is a surface view of a polyimide composite film product produced using a polyimide composite film production system.

[0050] Figure 15 This is a diagram of the surface of a polyimide composite film product produced using existing technology (large adhesive particles are present on the film surface).

[0051] Figure 16 This is a diagram of the surface of a polyimide composite film product produced using existing technology (the film surface is uneven and contains a large number of small particles).

[0052] Legend:

[0053] 1. Fluorine emulsion constant pressure feeding device; 11. Replenishment tank; 111. Compressed gas inlet; 112. Vent port; 12. Emulsion tank; 121. Pressure gauge; 122. Level gauge; 13. Replenishment pipe; 131. Replenishment control valve; 14. Compressed gas inlet pipe; 141. Inlet proportional valve; 15. Compressed gas exhaust pipe; 151. Exhaust proportional valve; 16. Controller; 17. Feeding pipe; 171. Y-type filter; 172. Rotor flow meter; 173. Needle valve; 2. Emulsion coating device; 21. Back pressure roller; 22. Slit die head; 221. Die lip; 222. Digital display micrometer screw; 3. Substrate unwinding device 4. Winding device; 5. Drying device; 51. Microwave sub-heating zone; 511. Microwave insulation cover; 5111. First insulation plate; 5112. Second insulation plate; 5113. Third insulation plate; 512. Microwave heating cavity; 513. Microwave drying channel; 514. Magnetron; 515. Thermocouple; 516. Evacuation pipe; 52. Infrared sub-heating zone; 521. Infrared heating unit; 522. Heat insulation cover plate; 523. Adjusting screw; 524. Infrared heating plate; 525. Infrared drying channel; 526. Infrared heating block; 53. Reversing assembly; 54. Microwave heating zone; 55. Infrared heating zone. Detailed Implementation

[0054] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0055] Example 1:

[0056] like Figure 1 As shown, the drying apparatus for the polyimide composite film in this embodiment includes a microwave heating zone 54 for passing through and drying the polyimide composite film formed by coating an emulsion on the surface of a polyimide substrate film using microwave heating, and an infrared heating zone 55 for passing through and drying the microwave-heated polyimide composite film using infrared heating. The microwave heating zone 54 and the infrared heating zone 55 are arranged sequentially and are interconnected. The polyimide composite film passes through the microwave heating zone 54 and the infrared heating zone 55 sequentially in a vertical direction. Specifically, the input end of the microwave heating zone 54 is connected to the output end of the emulsion coating device 2, and the output end of the infrared heating zone 55 is connected to the input end of the winding device 4.

[0057] In this embodiment, the drying device 5 further includes a reversing component 53 for changing the forward direction of the film. The reversing component 53 is disposed between the microwave heating zone 54 and the infrared heating zone 55. The forward direction of the polyimide composite film in the microwave heating zone 54 and the infrared heating zone 55 remains vertical and opposite.

[0058] In this embodiment, the microwave heating zone 54 and the infrared heating zone 55 are vertically arranged on both sides of the drying device 5. The reversing assembly 53 is arranged on the top of the drying device 5 and connected to the microwave heating zone 54 and the infrared heating zone 55. The reversing assembly 53 includes a reversing roller and a reversing roller drive, and the reversing roller drive is connected to the reversing roller. Specifically, the microwave heating zone 54 and the infrared heating zone 55 are respectively arranged on the left and right sides of the drying device 5. The reversing assembly 53 is located on top of the microwave heating zone 54 and the infrared heating zone 55. The film passes through the microwave heating zone 54 from bottom to top, changes direction through the reversing assembly 53, and then passes through the infrared heating zone 55 from top to bottom.

[0059] like Figure 2 As shown, in this embodiment, the microwave heating zone 54 includes multiple microwave sub-heating zones 51 arranged sequentially along the advancing direction of the polyimide composite film. Each microwave sub-heating zone 51 includes a pair of U-shaped microwave insulation covers 511. The pair of microwave insulation covers 511 are arranged opposite each other to form a microwave heating cavity 512. A microwave drying channel 513 for the polyimide composite film to pass through is provided between the pair of microwave insulation covers 511. Specifically, this embodiment uses a multi-source microwave generator array with a working frequency of 915MHz or 2450MHz and a total power of up to 50kW. The microwave power can be controlled in segments, and each segment's power can be adjusted independently.

[0060] In this embodiment, the microwave insulation cover 511 is also provided with a magnetron 514, a thermocouple 515, and an extraction pipe 516 for extracting moisture that escapes from the microwave heating cavity 512. The microwave insulation cover 511 includes a first insulation plate 5111, a second insulation plate 5112, and a third insulation plate 5113. The first insulation plate 5111 and the second insulation plate 5112 are arranged at intervals relative to each other. The two sides of the third insulation plate 5113 are respectively connected to the first insulation plate 5111 and the second insulation plate 5112 to form a U-shaped structure. The magnetron 514 is provided at the connection between the third insulation plate 5113 and the first insulation plate 5111 and the third insulation plate 5113 and the second insulation plate 5112. The thermocouple 515 and the extraction pipe 516 are provided on the third insulation plate 5113 and connected to the microwave heating cavity 512. Specifically, the first insulation plate 5111, the second insulation plate 5112 and the third insulation plate 5113 are connected to form a U-shaped microwave insulation cover 511. Magnetrons 514 are provided at the two corners of the microwave insulation cover 511. For the microwave heating cavity 512 composed of a pair of microwave insulation covers 511, magnetrons 514 are provided at the four corners of the cavity to achieve a better microwave heating and drying effect.

[0061] like Figures 3 to 6As shown, in this embodiment, the infrared heating zone 55 includes multiple infrared sub-heating zones 52 arranged sequentially along the forward direction of the polyimide composite film. Each infrared sub-heating zone 52 has several infrared heating units 521 on both sides, and an infrared drying channel 525 for the polyimide composite film to pass through is provided between the infrared heating units 521 on both sides. The infrared heating units 521 on both sides of each infrared sub-heating zone 52 are arranged at intervals along the horizontal direction of the film, such as... Figure 4 As shown in the figure, the layout of infrared heating units 521 on one side of an infrared sub-heating area 52 along the horizontal direction of the membrane is schematically illustrated. It should be noted that multiple infrared heating units 521 on one side of an infrared sub-heating area 52 are usually arranged along the horizontal direction of the membrane. Only two infrared heating units 521 are shown in the figure for illustration, which does not mean that only two infrared heating units 521 are provided (the dividing line in the middle represents the omitted infrared heating units 521). The infrared heating unit 521 includes a heat insulation cover plate 522, an adjusting screw 523, and an infrared heating plate 524. The heat insulation cover plate 522 is fixedly installed and has a fixing hole that cooperates with the adjusting screw 523. One end of the adjusting screw 523 is detachably and fixedly connected to the heat insulation cover plate 522, and the other end is fixedly connected to the infrared heating plate 524. The infrared heating plate 524 has multiple infrared heating blocks 526, which are arranged alternately with each other. Specifically, multiple infrared heating units 521 located at the same height belong to the same infrared sub-heating zone 52. Multiple infrared heating units 521 are arranged laterally within the infrared heating zone 55, with heater power exceeding 1000W, covering the horizontal direction of the polyimide composite film to achieve uniform internal ambient temperature and reduce the impact of temperature differences at different locations along the horizontal direction. Specifically, a group of infrared heating units 521 is set up every 200mm-400mm along the horizontal direction of the film for individual adjustment. Multiple groups with independently adjustable temperature differences ensure consistent final heating temperature to the film surface. Furthermore, multiple infrared heating blocks 526 are closely and staggered on the infrared heating plate 524 to further improve heating uniformity. An additional set of temperature control probes is provided within the same infrared sub-heating zone 52. If a temperature control probe in the zone fails unexpectedly, the backup probe can take over. The infrared heating blocks 526 have an internal hollow structure filled with THI insulation cotton. This structure concentrates energy as much as possible on the front, reducing the back temperature and improving energy utilization, achieving energy savings of over 15%.

[0062] like Figure 7As shown, in this embodiment, the outermost infrared heating units 521 along the horizontal direction of the film in each infrared sub-heating zone 52 (the infrared heating units 521 on the left and right sides in the figure) are inclined towards the film. Multiple infrared heating units 521 are typically arranged along the horizontal direction of the film on one side of an infrared sub-heating zone 52. Only four infrared heating units 521 are shown in the figure for illustration, and this does not mean that only four infrared heating units 521 are present (the dividing line in the middle represents omitted infrared heating units 521). The temperature of each infrared heating unit 521 located in the same infrared sub-heating zone 52 is set to maintain a uniform film surface temperature in the infrared drying channel 525 of that infrared sub-heating zone 52. Specifically, since the heating power of each infrared heating unit 521 can be controlled individually, the heating power of each infrared heating unit 521 is adjusted according to actual conditions and production needs to maintain a uniform film surface temperature in the corresponding infrared sub-heating zone 52, avoiding uneven heating of different parts of the film in the same infrared sub-heating zone 52, such as different positions along the horizontal direction, thereby affecting the final product quality.

[0063] By employing the drying device 5 of this embodiment, compared with the hot air drying method in the prior art, the weld strength (350°C) and transverse uniformity of the polyimide composite film product in this embodiment are significantly improved. The weld strength (350°C) of this embodiment can reach 0.4-0.42.

[0064] The weld strength performance parameters of the above-mentioned polyimide composite film products were tested according to the method of GB / T2791-1995.

[0065] Example 2:

[0066] like Figure 8 As shown, the polyimide composite film production system of this embodiment includes a fluorinated emulsion constant pressure feeding device 1, an emulsion coating device 2, a substrate unwinding device 3, a winding device 4, and the aforementioned polyimide composite film drying device 5. The emulsion coating device 2 is connected to the output ends of the fluorinated emulsion constant pressure feeding device 1 and the substrate unwinding device 3, respectively. The input end of the drying device 5 is connected to the output end of the emulsion coating device 2, and the input end of the winding device 4 is connected to the output end of the drying device 5.

[0067] like Figure 9As shown, in this embodiment, the fluorinated emulsion constant pressure feeding device 1 includes a replenishment tank 11 and an emulsion tank 12. A replenishment pipe 13 is provided between the replenishment tank 11 and the emulsion tank 12 for conveying emulsion to the emulsion tank 12 through the pressure difference between the replenishment tank 11 and the emulsion tank 12. The emulsion tank 12 is provided with a compressed gas inlet pipe 14 and a compressed gas outlet pipe 15. The fluorinated emulsion constant pressure feeding device 1 also includes a controller 16 for controlling the pressure inside the emulsion tank 12 to be basically constant by controlling the compressed gas flow rate of the compressed gas inlet pipe 14 and the compressed gas outlet pipe 15. The outlet of the emulsion tank 12 is also provided with a feeding pipe 17 for conveying emulsion to the emulsion coating device 2 through the pressure difference between the emulsion tank 12 and the emulsion coating device 2. The emulsion is used to coat the surface of the substrate film to form a coated composite film. No delivery pump is provided on the replenishment pipe 13 or the feeding pipe 17. Specifically, controller 16 is a PLC controller, and the emulsion is a polytetrafluoroethylene (PTFE) emulsion. In order to avoid demulsification, no pump of any kind is installed on the replenishment pipe 13 and the feed pipe 17.

[0068] In this embodiment, an intake proportional valve 141 is provided on the compressed gas inlet pipe 14, an exhaust proportional valve 151 is provided on the compressed gas exhaust pipe 15, and a pressure gauge 121 for monitoring the pressure inside the emulsion tank 12 is provided on the emulsion tank 12. The intake proportional valve 141, the exhaust proportional valve 151, and the pressure gauge 121 are all connected to the controller 16 via signal connection. When the pressure gauge 121 detects a change in the pressure inside the emulsion tank 12, the controller 16 adjusts the intake proportional valve 141 and the exhaust proportional valve 151 to maintain a constant pressure inside the emulsion tank 12, thereby ensuring a stable emulsion delivery process through the replenishment pipe 13 and the supply pipe 17. Specifically, a check valve is also provided on the compressed gas inlet pipe 14.

[0069] In this embodiment, a replenishment control valve 131 is provided on the replenishment pipe 13, and a level gauge 122 for monitoring the emulsion level in the emulsion tank 12 is provided on the emulsion tank 12. Both the replenishment control valve 131 and the level gauge 122 are connected to the controller 16 via signal connection. When the level gauge 122 detects a change in the emulsion level in the emulsion tank 12, the controller 16 adjusts the replenishment control valve 131 to control the emulsion level in the emulsion tank 12 within a preset range. Specifically, the level gauge 122 is a radar level gauge installed on the top of the emulsion tank 12.

[0070] In this embodiment, the feed pipe 17 is equipped with a Y-type filter 171, a rotor flow meter 172, and a needle valve 173 for precisely controlling the flow rate of the emulsion delivered to the emulsion coating device 2. The Y-type filter 171 is located upstream of the needle valve 173, and the rotor flow meter 172 is located downstream of the needle valve 173.

[0071] like Figure 10As shown, in this embodiment, the emulsion coating device 2 includes a slit-type die head 22 for uniformly coating the emulsion onto the substrate film. The slit-type die head 22 includes a die lip 221 that cooperates with each other. The die lip 221 is provided with a digital display micrometer screw 222 that can precisely adjust the lip spacing. The emulsion coating device 2 also includes a back pressure roller 21, and the slit-type die head 22 is located above the back pressure roller 21. Specifically, the emulsion coating device 2 includes a back pressure roller 21, a slit die head 22, and a flow regulating valve. The back pressure roller 21 is used to support the substrate film (polyimide film / PI film). A vacuum adsorption roller is also provided at the upstream end of the back pressure roller 21. The emulsion from the fluorinated emulsion constant pressure feeding device 1 is sent to the lip 221 of the slit die head 22 to form a stable "slurry curtain". The film thickness at different width positions can be adjusted by finely adjusting the bolt gap through the digital display micrometer screw 222. The "slurry curtain" is evenly sprayed on the PI film and coated stably by the support of the back pressure roller 21.

[0072] In this embodiment, the compressed gas is a high-quality compressed gas with a particle size ≤0.3μm, a dew point ≤-20℃, and an oil content ≤0.01mg / m³. 3 .

[0073] In this embodiment, the replenishment tank 11 is provided with a compressed gas inlet 111 and a vent 112.

[0074] In this embodiment, a cantilevered micro-stirrer is provided inside the emulsion tank 12.

[0075] In this embodiment, the emulsion tank 12, the replenishment pipe 13, and the feed pipe 17 are all equipped with a jacketed circulating constant temperature system to precisely control the temperature of the PTFE emulsion.

[0076] The fully automatic replenishment process of the fluorinated emulsion constant pressure feeding device 1 in this embodiment is as follows: A replenishment tank 11 is set up to replenish the emulsion tank 12. The pressure of the replenishment tank 11 can be adjusted through the compressed gas inlet 111 and the vent 112. The controller 16 sets the upper and lower limits of the control liquid level in the emulsion tank 12. The level gauge 122 installed on the top of the emulsion tank 12 scans the changes in the liquid level of the emulsion material in the emulsion tank 12 in real time. When the liquid level in the emulsion tank 12 is at the lower limit, the replenishment control valve 131 is automatically opened. Through the pressure difference between the replenishment tank 11 and the emulsion tank 12, new material is continuously supplied to the emulsion tank 12, avoiding shear conveying and maintaining material stability. When the liquid level is higher than the upper limit of the liquid level alarm, the replenishment control valve 131 is automatically closed, and the replenishment ends.

[0077] The fully automatic feeding process of the fluorinated emulsion constant pressure feeding device 1 in this embodiment is as follows: a needle valve 173 and a rotor flow meter 172 are installed on the feeding pipe 17 at the emulsion material outlet. By adjusting the minute displacement of the needle valve core with precision needle type adjustment, milliliter-level flow control is achieved to meet the feeding requirements of different coating processes.

[0078] Compared to the prior art's method of using a transfer pump for liquid replenishment, the constant pressure feeding device 1 for fluorinated emulsions in this embodiment significantly improves the stability of the emulsion, such as... Figure 11 As shown, after 100 hours of operation, the fluorinated emulsion filter remained clean with no demulsification or precipitation; however, using a pump with existing technology to deliver the emulsion for 12 hours resulted in demulsification, such as... Figure 12 As shown in the figure, the emulsion has precipitated and broken on the filter screen, resulting in severe clogging. The quality of coated composite membrane products (such as PI / PTFE composite membranes) prepared using this emulsion is significantly improved; see [link to details]. Figure 13 As can be seen from the figure, the membrane is continuous, fine and uniform (the yellow area in the figure is caused by the light from the production equipment shining on the support roller below).

[0079] The aforementioned constant-pressure feeding device 1 for fluorinated emulsions provides stable and high-quality emulsion raw materials. Simultaneously, the temperature uniformity of the drying device 5 provides an ideal thermal environment for the gradient curing of coatings such as PTFE coatings. The transverse temperature difference of the film is less than ±1℃, effectively avoiding internal stress, warping, and bubbles. This significantly improves the adhesion between the coating and the substrate, as well as the overall performance of the final product. The final polyimide composite film product has a fine and uniform surface, without obvious adhesive particles. Specifically, as shown... Figure 14 As shown in the figure. However, the polyimide composite film product prepared using existing technology exhibits noticeable colloidal particles on its surface due to emulsion demulsification and uneven heating, specifically as shown in the figure. Figure 15 and Figure 16 As shown.

[0080] The polyimide composite film production system of this embodiment uses a high-gloss pressure vessel and pipeline. By controlling the constant pressure and slowly extruding the emulsion material, problems such as emulsion breakage caused by shearing can be effectively controlled. The extruded low-viscosity PTFE emulsion material enters the emulsion coating device 2 to precisely coat the PI film surface. The drying device 5 with multi-stage precise temperature control ensures that the product is heated uniformly in the lateral direction. It has the advantages of good coating properties, uniform coating, no raw material breakage and precipitation particles, and strong adhesion. The product process quality is stable, the continuous production time is long, and the production efficiency and product yield are significantly improved.

[0081] This embodiment uses the above-mentioned polyimide composite film production system to prepare a film with specifications of PTFE / PI / PTFE 12 / 16 / 2.5μm. The preparation method includes the following steps:

[0082] S1. Add defoamer, leveling agent, thickener and emulsion stabilizer to the PTFE low viscosity emulsion, then dilute with water to 50% solid content, pour into the fluorinated emulsion constant pressure feeding device 1, and set the pressure parameter of the emulsion tank 12 to 0.50MPa.

[0083] S2. Place the rolled 16μm PI film in the substrate unwinding device 3 area and guide the film to the winding device 4;

[0084] S3. Adjust the contact gap between the slit die 22 and the PI film in the emulsion coating device 2 and the flow rate of PTFE emulsion at the lip (7L / h).

[0085] S4. The PTFE emulsion is uniformly coated onto the A side of the PI film using a slit-type die 22, with a coating thickness of 12μm. The machine speed is 4m / min. The coated film is then sent to the drying device 5 for drying. The drying device 5 includes microwave heating zone I (preheating zone, 100℃), microwave heating zone II (drying and volatile zone, 130℃), microwave heating zone III (melting zone, 200℃); infrared heating zone IV (high-temperature sintering zone, 300℃), infrared heating zone V (forming and cooling zone, 260℃), and infrared heating zone VI (tail-end cooling zone, 100℃), forming an adhesive layer on the A side.

[0086] S5. PTFE emulsion is uniformly coated onto the B side of the PI film with a coating thickness of 2.5 μm. The machine speed is 6 m / min. The coated film is then sent to the drying device 5 for drying. The drying device 5 includes microwave heating zone I (preheating zone, 100℃), microwave heating zone II (drying and volatile zone, 200℃), microwave heating zone III (melting zone, 320℃); infrared heating zone IV (high-temperature sintering zone, 380℃), infrared heating zone V (forming and cooling zone, 320℃), and infrared heating zone VI (tail-end cooling zone, 100℃) to form the B-side adhesive layer, finally obtaining a uniformly coated PTFE / PI / PTFE film after curing.

[0087] Comparative example:

[0088] S1. Add defoamer, leveling agent, thickener and emulsion stabilizer to the PTFE low viscosity emulsion, then dilute with water to 50% solid content, pour into a stainless steel container, and feed and transport the material using a low shear peristaltic pump.

[0089] S2. Dry the 16μm PI film in a hot air oven from unwinding to rewinding.

[0090] S3. PTFE emulsion is coated onto the A side of the PI film by dip coating. The coating thickness is 12μm by extrusion wire metering at a speed of 0.8m / min. The temperatures of hot air heating zone I (100℃), hot air heating zone II (130℃), hot air heating zone III (200℃), hot air heating zone IV (300℃), hot air heating zone V (260℃), and hot air heating zone VI (100℃) are used to form the A side adhesive layer.

[0091] S4. Coat the B side of the PI film with PTFE emulsion. The coating thickness is 2.5μm using an extrusion wire rod metering method at a speed of 0.8m / min. The temperature of hot air heating zone I (100℃), hot air heating zone II (200℃), hot air heating zone III (320℃), hot air heating zone IV (380℃), hot air heating zone V (320℃), and hot air heating zone VI (100℃) are used to form the B side adhesive layer, thus obtaining the cured PTFE / PI / PTFE film.

[0092] The relevant properties of the PTFE / PI / PTFE films in the above embodiments and comparative examples were tested, and the results are shown in the table below.

[0093] Table 1. Test results of relevant properties of PTFE / PI / PTFE films

[0094]

[0095] As can be seen from the data in the table above, the PTFE / PI / PTFE film prepared in Example 2 shows a significant improvement in operational stability compared to the original mechanically transported PTFE emulsion material in the comparative example. It can operate for more than 100 hours, and the number of "particles" with product appearance defects is significantly reduced. This solves the problem of coating thick coatings at high speeds and avoids the inefficiency and low quality of multiple coatings. The product curing adopts microwave heating and infrared heating in synergistic drying, which ensures the uniformity of peel force of the product after coating in the horizontal direction, and can greatly improve efficiency.

[0096] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the present invention, should fall within the protection scope of the present invention.

Claims

1. A drying device for a polyimide composite film, characterized in that: The drying device (5) further comprises a reversing assembly (53) for changing the advancing direction of the film, the reversing assembly (53) is arranged between the microwave heating zone (54) and the infrared heating zone (55), and the advancing directions of the polyimide composite film in the microwave heating zone (54) and the infrared heating zone (55) are kept vertical and opposite. The microwave heating zone (54) comprises a plurality of microwave sub-heating zones (51) arranged in sequence along the advancing direction of the polyimide composite film, and the microwave sub-heating zones (51) of the microwave heating zone (54) form a preheating zone, a drying volatile zone and a melting zone in sequence along the advancing direction of the polyimide composite film. The infrared heating zone (55) comprises a plurality of infrared sub-heating zones (52) arranged in sequence along the advancing direction of the polyimide composite film, and the infrared sub-heating zones (52) of the infrared heating zone (55) form a high-temperature sintering zone, a forming cooling zone and a tail cooling zone in sequence along the advancing direction of the polyimide composite film, each of the infrared sub-heating zones (52) is provided with a plurality of infrared heating units (521) on both sides, the infrared heating units (521) on both sides of each of the infrared sub-heating zones (52) are arranged in a spaced manner along the width direction of the film, and the infrared heating units (521) on the outermost side of each of the infrared sub-heating zones (52) along the width direction of the film are arranged in a tilted manner towards the film.

2. The drying apparatus of the polyimide composite film according to claim 1, characterized by: The drying device (5) further comprises a reversing assembly (53) for changing the advancing direction of the film, the reversing assembly (53) is arranged between the microwave heating zone (54) and the infrared heating zone (55), and the advancing directions of the polyimide composite film in the microwave heating zone (54) and the infrared heating zone (55) are kept vertical and opposite.

3. The drying apparatus of the polyimide composite film according to claim 2, characterized by: The microwave heating zone (54) and the infrared heating zone (55) are vertically arranged on both sides of the drying device (5) respectively, the reversing assembly (53) is arranged on the top of the drying device (5) and is connected with the microwave heating zone (54) and the infrared heating zone (55).

4. The drying apparatus of the polyimide composite film according to any one of claims 1 to 3, characterized by: The microwave sub-heating zone (51) comprises a pair of microwave heat preservation covers (511) in U-shaped structure, the pair of microwave heat preservation covers (511) are arranged oppositely to form a microwave heating cavity (512), and a microwave drying channel (513) for the polyimide composite film to pass through is arranged between the pair of microwave heat preservation covers (511).

5. The drying apparatus of the polyimide composite film according to claim 4, characterized by: The microwave holding cover (511) is further provided with a magnetron (514), a thermocouple (515) and an air exhaust pipe (516) for extracting water vapor escaped from the microwave heating cavity (512), the microwave holding cover (511) comprises a first holding plate (5111), a second holding plate (5112) and a third holding plate (5113), the first holding plate (5111) and the second holding plate (5112) are oppositely spaced, the third holding plate (5113) is connected with the first holding plate (5111) and the second holding plate (5112) on both sides to form a U-shaped structure, the magnetron (514) is arranged at the connecting position of the third holding plate (5113) and the first holding plate (5111) and the third holding plate (5113) and the second holding plate (5112), and the thermocouple (515) and the air exhaust pipe (516) are arranged on the third holding plate (5113) and connected with the microwave heating cavity (512).

6. The drying apparatus of the polyimide composite film according to claim 1, characterized by: The infrared heating units (521) on both sides are provided with an infrared drying channel (525) for passing the polyimide composite film.

7. The drying apparatus of the polyimide composite film according to claim 6, characterized by: The infrared heating unit (521) comprises a heat insulation cover plate (522), an adjusting screw (523) and an infrared heating plate (524), the heat insulation cover plate (522) is fixedly arranged and provided with a fixing hole matched with the adjusting screw (523), one end of the adjusting screw (523) is detachably fixedly connected with the heat insulation cover plate (522), and the other end is fixedly connected with the infrared heating plate (524), the infrared heating plate (524) is provided with a plurality of infrared heating blocks (526), and the plurality of infrared heating blocks (526) are arranged in an interlaced manner.

8. A production system of a polyimide composite film, characterized by comprising: The drying device (5) of the polyimide composite film comprises a fluorine-containing emulsion constant pressure feeding device (1), an emulsion coating device (2), a substrate unwinding device (3) and the polyimide composite film drying device (5) of any one of claims 1 to 7, the emulsion coating device (2) is connected with the output ends of the fluorine-containing emulsion constant pressure feeding device (1) and the substrate unwinding device (3) respectively, and the input end of the drying device (5) is connected with the output end of the emulsion coating device (2).

9. The polyimide composite film production system according to claim 8, characterized by: The fluorine-containing emulsion constant pressure feeding device (1) comprises a liquid supplement tank (11) and an emulsion tank (12), a liquid supplement pipe (13) for delivering emulsion to the emulsion tank (12) by pressure difference between the liquid supplement tank (11) and the emulsion tank (12) is arranged between the liquid supplement tank (11) and the emulsion tank (12), a compressed gas inlet pipe (14) and a compressed gas outlet pipe (15) are arranged on the emulsion tank (12), the fluorine-containing emulsion constant pressure feeding device (1) further comprises a controller (16) for controlling the pressure in the emulsion tank (12) to be substantially constant by controlling the flow of compressed gas through the compressed gas inlet pipe (14) and the compressed gas outlet pipe (15), and an emulsion feeding pipe (17) for delivering emulsion to an emulsion coating device (2) by pressure difference between the emulsion tank (12) and the emulsion coating device (2) is arranged at the outlet of the emulsion tank (12), the emulsion is used to coat on the surface of a substrate film to form a coated composite film, and no delivery pump is arranged on the liquid supplement pipe (13) and the emulsion feeding pipe (17).

10. The polyimide composite film production system according to claim 9, characterized by: The compressed gas inlet pipe (14) is provided with an inlet proportional valve (141), the compressed gas outlet pipe (15) is provided with an outlet proportional valve (151), and a pressure gauge (121) for monitoring the pressure in the emulsion tank (12) is arranged on the emulsion tank (12), the inlet proportional valve (141), the outlet proportional valve (151) and the pressure gauge (121) are signal connected with the controller (16), when the pressure gauge (121) detects that the pressure in the emulsion tank (12) changes, the controller (16) is used to adjust the inlet proportional valve (141) and the outlet proportional valve (151) to maintain the pressure in the emulsion tank (12) constant, so that the emulsion delivery process of the liquid supplement pipe (13) and the emulsion feeding pipe (17) is maintained stable.

11. The polyimide composite film production system according to claim 9, characterized by: The liquid supplement pipe (13) is provided with a liquid supplement control valve (131), and a liquid level gauge (122) for monitoring the liquid level in the emulsion tank (12) is arranged on the emulsion tank (12), the liquid supplement control valve (131) and the liquid level gauge (122) are signal connected with the controller (16), when the liquid level gauge (122) detects that the liquid level in the emulsion tank (12) changes, the controller (16) is used to adjust the liquid supplement control valve (131) to control the liquid level in the emulsion tank (12) within a preset range.

12. The polyimide composite film production system according to any one of claims 9 to 11, characterized by: The emulsion feeding pipe (17) is provided with a Y-type filter (171), a rotor flowmeter (172) and a needle valve (173) for accurately controlling the flow of emulsion delivered to the emulsion coating device (2), the Y-type filter (171) is arranged upstream of the needle valve (173), and the rotor flowmeter (172) is arranged downstream of the needle valve (173).

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