Lithium battery diaphragm production extraction inlet protection method and system

Abstract

The invention discloses a method for protecting the extraction entrance of lithium battery diaphragm production, the method comprising: forming a first sealing area and a second sealing area connected to the extraction tank membrane entrance, the film entering the extraction tank from the membrane entrance is located between the first sealing area and the second sealing area; the first sealing area and the second sealing area are subjected to suction treatment by a suction device, so that the volatilized dichloromethane gas and indoor air in the extraction tank enter the first sealing area and the second sealing area; obtaining the gas pressure values ​​of the first sealing area and the second sealing area, and selecting one of them as the atmosphere pressure value; controlling the frequency of the suction device according to the atmosphere pressure value, so that the atmosphere pressure value is within a preset range. The first sealing area and the second sealing area of ​​the invention are in a negative pressure state, the dichloromethane gas will not be discharged into the workshop, and the dichloromethane flow rate delivered to the adsorption / desorption device is small, which delays the adsorption saturation speed of the adsorption / desorption core and ensures the long-term effective operation of the adsorption and desorption core.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery diaphragm preparation, and in particular to a method and system for protecting an extraction inlet of a lithium battery diaphragm production. Background Art

[0002] The wet process of lithium batteries can also be called the thermally induced phase separation method. The main principle of this method is to mix the polymer with a small molecular weight and high boiling point solvent white oil to obtain a mixture, extrude the mixture through an extruder at a predetermined high temperature to obtain a melt, and obtain a cast sheet by casting or calendering the melt. The cast sheet is stretched near the melting point to obtain a film, and the volatile reagent dichloromethane is used as an extractant to extract the high boiling point solvent white oil remaining on the film to obtain a polymer microporous film.

[0003] Extraction is one of the key processes in the wet process of lithium batteries. The dichloromethane extract is placed in the extraction tank. The boiling point of dichloromethane is around 39.8°C, and it is easy to evaporate from liquid to gas at room temperature. When the production line starts to produce film or the film breaks, the film needs to be pulled from the membrane inlet to the membrane outlet. Since the membrane inlet is open, the volatile dichloromethane gas will diffuse into the workshop through the membrane inlet. Dichloromethane is an irritating and toxic organic compound that can cause harm to the human body, such as damage to the central nervous system, damage to the lungs, spontaneous abortion, etc. Therefore, the extraction tank needs to be protected to form a negative pressure environment in the extraction tank to prevent the volatile dichloromethane from directly diffusing into the workshop.

[0004] The utility model patent with patent number 202222187345.5 discloses a micro-negative pressure vacuum device suitable for an extraction tank. The negative pressure mechanism provides negative pressure to the micro-suction mechanism, so that the micro-suction mechanism absorbs the volatilized extract in the extraction tank, preventing the extract from volatilizing and discharging into the workshop, reducing environmental pollution, and providing safety protection for workers in the production workshop. However, the negative pressure suction pipe of the device extends directly into the extraction tank for suction. If the suction pressure is too small, the dichloromethane gas will still be discharged to the workshop through the membrane inlet and membrane outlet, and will not play a protective role. If the suction pressure is too high, the flow rate of dichloromethane gas that needs to be recovered will also be larger, which will increase the recovery burden of the absorption / desorption device, and the frequency of replacement of the absorption / desorption device will be high, which will increase the production cost. Summary of the invention

[0005] In view of the above technical problems, the purpose of the present invention is to provide a lithium battery diaphragm production extraction protection system and method, which performs quasi-sealing treatment on the membrane inlet and / or membrane outlet, so that dichloromethane gas will not be discharged to the workshop, and the dichloromethane flow rate delivered to the adsorption / desorption device is small, thereby slowing down the adsorption saturation rate of the adsorption / desorption core and ensuring the long-term effective operation of the adsorption / desorption core.

[0006] The present invention provides a method for protecting the extraction entrance of a lithium battery diaphragm production, the method comprising:

[0007] A first sealing area and a second sealing area are formed at the membrane inlet of the extraction tank, which are in communication with the membrane inlet, and the thin film entering the extraction tank from the membrane inlet is located between the first sealing area and the second sealing area;

[0008] The first sealed area and the second sealed area are subjected to suction treatment by the air suction device, so that the volatilized dichloromethane gas in the extraction tank and the indoor air enter the first sealed area and the second sealed area;

[0009] Obtain the gas pressure values ​​of the first sealing area and the second sealing area, and select one of them as the atmosphere pressure value;

[0010] The frequency of the air suction device is controlled according to the atmosphere pressure value so that the atmosphere pressure value is within a preset range.

[0011] In some embodiments, controlling the frequency of the air suction device according to the atmosphere pressure value so that the atmosphere pressure value is within a preset range includes:

[0012] If the atmosphere pressure value is less than the first target pressure threshold, the control device controls the air suction device to reduce the frequency at a predetermined frequency reduction speed until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency reduction is stopped;

[0013] If the atmosphere pressure value is greater than the second target pressure threshold, the control device controls the air suction device to increase the frequency at a predetermined frequency increase rate until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency increase is stopped;

[0014] If the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, the air suction device is controlled to maintain the current frequency operation and continue to monitor the atmosphere pressure value.

[0015] In some embodiments, the extraction tank protection device includes a frame, a drive roller group and a suction device, the frame is installed on the extraction tank and is located on the membrane inlet side of the extraction tank; the drive roller group includes a first drive roller and a second drive roller for pulling the film, the first drive roller and the second drive roller are staggered in the traveling direction of the film, and are enclosed with the frame, the film and the extraction tank to form a first sealing area and a second sealing area, the first sealing area and the second sealing area are respectively located on both sides of the film, and are connected to the membrane inlet of the extraction tank; the suction device is connected to the first sealing area and the second sealing area, respectively, and is used to suck dichloromethane gas and air into the first sealing area and the second sealing area; the control device is used to measure the atmosphere pressure of the first sealing area and the second sealing area, and calculate the level that the suction device should suck based on the atmosphere pressure, and change or maintain the suction level based on the calculated result.

[0016] In some embodiments, the frame includes a first sealing structure and a second sealing structure, the first sealing structure includes two seals, and the first ventilation pipe, the two seals and the first transmission roller form a first suction chamber in the first sealing area; the second sealing structure includes two seals, and the second ventilation pipe, the two seals and the second transmission roller form a second suction chamber in the second sealing area; the control device is used to measure the atmosphere pressure of the first suction chamber and the second suction chamber, and calculate the level that the suction device should suck based on the atmosphere pressure, and change or maintain the suction level based on the calculated result.

[0017] In some embodiments, the control device includes a monitoring unit and a control unit, the monitoring unit includes an air pressure sensor installed in the first suction chamber and the second suction chamber, respectively, and the air pressure sensor is used to monitor the gas pressure value in the first suction chamber and the second suction chamber. The control unit is used to control the suction device to reduce the frequency at a predetermined frequency reduction rate if the atmosphere pressure value is less than the first pressure threshold, until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, then stop reducing the frequency; if the atmosphere pressure value is greater than the second pressure threshold, control the suction device to increase the frequency at a predetermined frequency increase rate until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, then stop increasing the frequency; and if the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, control the suction device to maintain the current frequency operation and return to the monitoring unit to continue monitoring the atmosphere pressure value.

[0018] In some embodiments, the two seals of the first sealing structure and the two seals of the second sealing structure are arranged in a figure eight shape.

[0019] In some embodiments, the gap between the seal and the transmission roller is 0.01-10 mm.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention forms a first sealing area and a second sealing area on both sides of the film, and only a small amount of dichloromethane gas in the extraction tank enters the first sealing area and the second sealing area, and the dichloromethane gas in the first sealing area and the second sealing area is transported to the absorption / desorption tank through the suction device. On the one hand, the air pressure in the first sealing area and the second sealing area is dynamically controlled to ensure that the first sealing area and the second sealing area are in a negative pressure state, and to ensure that the dichloromethane gas in the extraction tank will not be discharged into the workshop, thereby reducing the loss of dichloromethane and preventing the harm to the on-site workers caused by the volatilization of dichloromethane. On the other hand, due to the small flow rate of dichloromethane transported to the absorption / desorption device, the adsorption saturation speed of the absorption / desorption core is delayed, and the long-term effective operation of the adsorption and desorption core is guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The preferred implementation modes will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0023] Figure 1 It is a structural schematic diagram of the extraction tank negative pressure protection device of the present invention being assembled in the extraction tank.

[0024] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure.

[0025] Figure 3 It is a structural schematic diagram of the negative pressure protection device of the extraction tank of the present invention.

[0026] Figure 4 It is a structural schematic diagram of the part where the first transmission roller and the first sealing mechanism of the present invention are located.

[0027] Figure 5 It is another structural schematic diagram of the part where the first transmission roller and the first sealing mechanism are located in the present invention.

[0028] Figure 6 It is a structural schematic diagram of the part where the second transmission roller and the second sealing mechanism of the present invention are located.

[0029] Figure 7 It is another structural schematic diagram of the part where the second transmission roller and the second sealing mechanism of the present invention are located.

[0030] Description of Figure Numbers:

[0031] Support 1; film 2; first transmission roller 3; second transmission roller 4; extraction tank 5; first sealing structure 6; first ventilation pipe 61; sealing member 62; sealing strip 621; bottom plate 622; rib plate 623; second sealing structure 7; second ventilation pipe 71; first sealing area 8; first suction chamber 81; second sealing area 9; second suction chamber 91; third ventilation pipe 10; fourth ventilation pipe 11; fifth ventilation pipe 12; extraction tank negative pressure protection device 13. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0033] refer to Figure 1 and Figure 2 The extraction tank negative pressure protection device 13 in the embodiment of the present invention is used to suck the dichloromethane gas volatilized in the extraction tank 5, and form a negative pressure environment near the membrane inlet and / or membrane outlet of the extraction tank 5 to prevent the dichloromethane gas from being discharged into the workshop. In addition, the suction amount of dichloromethane is low, and the amount of dichloromethane gas delivered to the absorption / desorption device is small, thereby reducing the dichloromethane processing amount of the absorption / desorption device.

[0034] In the wet process of preparing lithium battery diaphragm, the film 2 needs to be inserted from the membrane inlet of the extraction tank 5, and then pass through the membrane outlet of the extraction tank 5 after passing through multiple rollers. The extraction tank negative pressure protection device 13 of the embodiment of the present invention is arranged at the membrane inlet and / or membrane outlet of the extraction tank 5, and the dichloromethane gas volatilized in the extraction tank 5 is sucked by the extraction tank negative pressure protection device 13. The number and installation position of the extraction tank negative pressure protection device 13 are not particularly limited in this embodiment, but it is particularly advantageous that the extraction tank negative pressure protection device 13 is arranged at the membrane inlet and membrane outlet of the extraction tank 5, and the two extraction tank negative pressure protection devices 13 are used to simultaneously perform micro-sucking at the membrane inlet and membrane outlet of the extraction tank 5, which can effectively prevent dichloromethane gas from being discharged into the workshop from the membrane inlet and membrane outlet of the extraction tank 5. As an example, the structure of the extraction tank negative pressure protection device 13 at the membrane inlet of the extraction tank 5 is described as follows in the embodiment of the present invention, and the structure of the extraction tank negative pressure protection device 13 at the membrane outlet of the extraction tank 5 can refer to the structure of the extraction tank negative pressure protection device 13 at the membrane inlet.

[0035] The extraction tank negative pressure protection device 13 comprises a frame, a transmission roller group and an air suction device.

[0036] refer to Figure 3, the transmission roller group includes two transmission rollers, which are rotatably connected to the frame, staggered in the traveling direction of the film 2, and extend along the length direction of the film inlet of the extraction tank 5. For the convenience of description and distinction, the transmission roller close to the film inlet of the extraction tank 5 is defined as the first transmission roller 3, and the other transmission roller is defined as the second transmission roller 4. The film 2 passes through the second transmission roller 4 and the first transmission roller 3 in sequence and enters the extraction tank 5 from the film inlet of the extraction tank 5. It can be understood by those skilled in the art that the height of the first transmission roller 3 and the second transmission roller 4 in the spatial position can be adjusted according to the production line requirements, and the embodiment of the present invention does not make specific limitations. As an example, the second transmission roller 4 is located obliquely above the first transmission roller 3, and the film 2 travels downward after wrapping around the second transmission roller 4, and enters the extraction tank 5 through the film inlet of the extraction tank 5 after wrapping around the first transmission roller 3. The film 2 entering the extraction tank 5 divides the film inlet of the extraction tank 5 into two parts, upper and lower.

[0037] The frame includes a bracket 1, a first sealing structure 6 and a second sealing structure 7. The bracket 1 is installed at the membrane inlet side of the extraction tank 5, and the drive roller group, the first sealing structure 6 and the second sealing structure 7 are installed on the bracket 1. The frame, the drive roller group, the film 2 and the extraction tank 5 are surrounded to form a first sealing area 8 and a second sealing area 9. The first sealing area 8 and the second sealing area 9 are respectively located on both sides of the film 2, which are almost completely closed. There is only a small gap between the sealing structure and the drive roller matching position, which does not affect the rotation of the drive roller and creates a nearly sealed environment, reducing the air output of the extraction tank 5.

[0038] refer to Figure 4 The first sealing structure 6 includes a first ventilation pipe 61 and a sealing member 62 .

[0039] The first ventilation pipe 61 is installed at the membrane entrance of the extraction tank 5, is located above the first driving roller 3, and extends along the length direction of the membrane entrance of the extraction tank 5. The first ventilation pipe 61 has an air inlet and an air outlet connected to the air inlet. The air inlet of the first ventilation pipe 61 is connected to the first sealing area 8, and the air outlet of the first ventilation pipe 61 is connected to the air suction device. The gas in the first sealing area 8 enters the first ventilation pipe 61 through the air inlet of the first ventilation pipe 61, and is transported to the suction / desorption device by the air suction device after passing through the air outlet of the first ventilation pipe 61. The embodiment of the present invention does not specifically limit the opening positions of the air inlet and the air outlet on the first ventilation pipe 61. As an example, a plurality of air inlets are provided at intervals along the length direction at the bottom of the first ventilation pipe 61, and a plurality of air outlets are provided at intervals along the length direction at the side of the first ventilation pipe 61.

[0040] The first ventilation pipe 61 is used to transmit the gas in the first sealing area 8 to the suction device. Its shape is circular, square or special-shaped structure, etc., and the number can be one or multiple interconnected ones. The embodiment of the present invention is not particularly limited. As an example, the first sealing structure 6 includes two first ventilation pipes 61, the air inlet of one first ventilation pipe 61 faces the first transmission roller 3, the air outlet of the first ventilation pipe 61 is connected with the air inlet of another ventilation pipe, and the air outlet of the other ventilation pipe is connected with the suction device. The first ventilation pipe 61 of the embodiment of the present invention can be a rectangular tube, which has a large contact area with the extraction tank 5, and realizes a stable connection between the extraction tank 5 and the extraction tank 5. The sealing is more reliable and can prevent the gas in the extraction tank 5 from being discharged from the gap between the first ventilation pipe 61 and the extraction tank 5.

[0041] The sealing member 62 includes a bottom plate 622 and a sealing strip 621. The extension direction of the bottom plate 622 is consistent with the length direction of the first ventilation pipe 61. The bottom plate 622 is formed by bending a plate multiple times to form a first mounting portion and a second mounting portion that are opposite to each other. The first mounting portion and the second mounting portion are respectively located on both sides of the width direction of the bottom plate 622. The bottom plate 622 is mounted on the first ventilation pipe 61 through the first mounting portion. The sealing strip 621 is mounted on the second mounting portion of the bottom plate 622, close to but not in contact with the first transmission roller 3. The air inlet of the first ventilation pipe 61 is located between the sealing strip 621 and the membrane inlet of the extraction tank 5. In order to improve the mechanical strength of the bottom plate 622, the sealing member 62 also includes a plurality of ribs 623. The plurality of ribs 623 are connected to the bottom plate 622 and arranged at intervals along the length direction of the bottom plate 622.

[0042] The first sealing area 8 in the embodiment of the present invention is separated from the indoor environment at the gap between the sealing strip 621 and the first transmission roller 3. When the suction device is sucking, the volatilized dichloromethane gas in the extraction tank 5 enters the first sealing area 8 through the upper part of the membrane inlet of the extraction tank 5, and the external air enters the first sealing area 8 through the gap between the sealing strip 621 and the first transmission roller 3. The mixed gas of dichloromethane gas and air flows toward the suction / desorption device through the first ventilation pipe 61. Since the suction device simultaneously extracts the air of the indoor environment and the dichloromethane gas in the extraction tank 5, compared with the method of directly extracting the dichloromethane gas in the extraction tank 5, under the same conditions, the extraction amount of dichloromethane is low, and the amount of dichloromethane delivered to the suction / desorption device is significantly reduced.

[0043] The adsorption / desorption device is a device for absorbing dichloromethane gas and desorbing the previously adsorbed dichloromethane through steam. The adsorption / desorption device includes an adsorption / desorption tank, each of which is provided with an adsorption / desorption core, and the adsorption / desorption core is used to adsorb dichloromethane gas. The material of the adsorption / desorption core is not specifically limited in the embodiment of the present invention, as long as it can adsorb dichloromethane and does not react chemically with it, and can also desorb dichloromethane after heating. For example, the material of the adsorption / desorption core is selected from activated carbon, zeolite, polystyrene resin, and polyamide resin, and one of them can be used, or more than two substances can be used at the same time. Since the embodiment of the present invention reduces the flow rate of dichloromethane delivered to the adsorption / desorption device, the adsorption saturation rate of the adsorption / desorption core is slowed down, and the long-term effective operation of the adsorption and desorption core is guaranteed.

[0044] refer to Figure 5 According to a preferred embodiment, the first sealing structure 6 includes two sealing members 62, and the two sealing members 62 are respectively connected to the two first ventilation pipes 61 through the bottom plate 622, and are arranged in a shape similar to an "eight". The first ventilation pipe 61, the two sealing members 62 and the first transmission roller 3 form a first suction chamber 81 in the first sealing area 8, and the air of the indoor environment enters the first suction chamber 81 through the gap between a sealing strip 621 and the first transmission roller 3, and the dichloromethane gas volatilized in the extraction tank 5 enters the first suction chamber 81 through the gap between another sealing strip 621 and the first transmission roller 3, and the mixed gas formed by the air and the dichloromethane gas is transported from the first suction chamber 81 to the adsorption / desorption device through the first ventilation pipe 61.

[0045] The embodiment of the present invention further blocks the dichloromethane gas in the extraction tank 5 from being discharged outward through the two sealing members 62 of the first sealing structure 6, and simultaneously draws air and dichloromethane gas through the suction device. Under the premise that the suction volume remains unchanged, the flow rate of dichloromethane entering the first ventilation pipe 61 is reduced, thereby reducing the flow rate of dichloromethane gas drawn by the suction device to the first sealing area 8.

[0046] refer to Figure 6 The second sealing structure 7 includes a second ventilation pipe 71 and a sealing member 62 .

[0047] The second ventilation pipe 71 is installed on the bracket 1, located below the second driving roller 4, and extends along the length direction of the membrane inlet of the extraction tank 5. The second ventilation pipe 71 has an air inlet and an air outlet connected to the air inlet. The air inlet of the second ventilation pipe 71 is connected to the second sealing area 9, and the air outlet of the second ventilation pipe 71 is connected to the air suction device. The dichloromethane gas in the second sealing area 9 enters the second ventilation pipe 71 through the air inlet of the second ventilation pipe 71, and flows to the air suction device after passing through the air outlet of the second ventilation pipe 71. The embodiment of the present invention does not specifically limit the opening positions of the air inlet and the air outlet. As an example, the top of the second ventilation pipe 71 is provided with a plurality of air inlets spaced apart along the length direction, and the bottom of the second ventilation pipe 71 is provided with a plurality of air outlets spaced apart along the length direction.

[0048] The second ventilation pipe 71 is used to transmit the gas in the second sealing area 9 to the suction device. Its shape is circular, square or special-shaped structure, etc. The number can be 1 or multiple interconnected ones. The embodiment of the present invention is not particularly limited. As an example, the second sealing structure 7 includes a second ventilation pipe 71, and the air inlet of the second ventilation pipe 71 faces the second drive roller 4.

[0049] The seal 62 of the second sealing structure 7 has the same structure as the seal 62 of the first sealing structure 6, and also includes a bottom plate 622 and a sealing strip 621. To save space and in accordance with the embodiment of the invention, the structure of the seal 62 is not described in detail. The bottom plate 622 of the seal 62 is mounted on the second ventilation pipe 71, the sealing strip 621 of the seal 62 is close to but not in contact with the second transmission roller 4, and the air inlet of the second ventilation pipe 71 is located between the sealing strip 621 of the seal 62 and the membrane inlet of the extraction tank 5.

[0050] The second sealing area 9 is separated from the indoor environment at the gap between the sealing strip 621 and the second transmission roller 4. When the suction device performs suction, the volatilized dichloromethane gas in the extraction tank 5 enters the second sealing area 9 through the lower half of the membrane inlet of the extraction tank 5, and the external air enters the second sealing area 9 through the gap between the sealing strip 621 and the second transmission roller 4. The mixed gas of dichloromethane gas and air flows toward the absorption / desorption tank through the second ventilation pipe 71.

[0051] refer to Figure 7According to a preferred embodiment, the second sealing structure 7 includes two sealing members 62, both of which are connected to the second ventilation pipe 71 through a bottom plate 622 and arranged in a shape similar to an "eight". The second ventilation pipe 71, the two sealing members 62 and the second transmission roller 4 form a second suction chamber 91 in the second sealing area 9, and the air of the indoor environment enters the second suction chamber 91 through the gap between a sealing strip 621 and the second transmission roller 4, and the dichloromethane gas volatilized in the extraction tank 5 enters the second suction chamber 91 through the gap between another sealing strip 621 and the second transmission roller 4, and the mixed gas formed by the air and the dichloromethane gas is transported from the second suction chamber 91 to the suction / desorption device through the suction device.

[0052] The two seals 62 of the second sealing structure 7 further prevent the volatilized dichloromethane gas in the extraction tank 5 from being discharged to the outside, and the air and dichloromethane gas are sucked simultaneously by the suction device. Under the premise of unchanged suction volume, the flow of dichloromethane entering the second ventilation pipe 71 is reduced, thereby reducing the flow of dichloromethane gas sucked by the suction device to the second sealing area 9.

[0053] It should be noted that the gap between the sealing strip 621 and the first transmission roller 3, and the gap between the sealing strip 621 and the second transmission roller 4 can be adjusted according to the process requirements. The larger the gap, the greater the gas flow, and vice versa, the gas flow becomes smaller. However, the adjustment is difficult, and it is easy to make the sealing strip 621 and the transmission roller rigidly contact, causing damage to the transmission roller. As an example, the gap between the sealing strip and the transmission roller is 0.01mm-10mm.

[0054] The suction device is a device for sucking gas, and delivers the dichloromethane gas in the extraction tank 5 to the suction / desorption tank, so that the first sealed cavity area and the second sealed area form a negative pressure environment, and the dichloromethane gas is prevented from being discharged into the workshop. The specific structure of the suction device is not particularly limited in this embodiment, as long as the structure can suck gas, for example, various known fans can be used. When the fan is used in the suction device, the air outlets of the first suction pipe and the second suction pipe are connected to the air inlet of the fan.

[0055] See again Figure 3 The air suction device includes a third ventilation pipe 10, a fourth ventilation pipe 11 and a fifth ventilation pipe 12 installed on the bracket 1. The third ventilation pipe 10 is located below the first transmission roller 3 and the second transmission roller 4, extends along the length direction of the membrane inlet of the extraction tank 5, and is located in the second sealing area 9. The first ventilation pipe 61 is connected with the third ventilation pipe 10 through the fourth ventilation pipe 11. The fourth ventilation pipe 11 is located on one side of the length direction of the membrane inlet of the extraction tank 5 and extends in the vertical direction. The second ventilation pipe 71 is connected with the third ventilation pipe 10 through the fifth ventilation pipe 12. The fifth ventilation pipe 12 can be a curved pipe to transport the mixed gas in the second ventilation pipe 71 from the second ventilation pipe 71 to the third ventilation pipe 10.

[0056] The frame should have a sealing plate, which is used to seal the open area of ​​the first sealing area 8 and the second sealing area 9 (excluding the gap between the sealing strip and the transmission roller) to prevent the dichloromethane gas in the first sealing area 8 and the second sealing area 9 from escaping outward through the pores. Advantageously, a sealing plate is connected between the second ventilation pipe 71 and the third ventilation pipe 10, and an inspection door (not shown) is formed on the sealing plate. When the film is broken or the production line starts production, the inspection door can be opened to expose the second sealing area 9. After the film passes through the second transmission roller 4, it is convenient for the staff to pass the film 2 on the first transmission roller 3. However, after the passing is completed, the inspection door needs to be closed in time to avoid failure of the second sealing area 9.

[0057] According to the extraction tank negative pressure protection device proposed in the present invention, the extraction tank and the film are enclosed to form the first sealing area 8 and the second sealing area 9. Only a small amount of dichloromethane gas in the extraction tank 5 enters the first sealing area 8 and the second sealing area 9, and the dichloromethane gas in the first sealing area 8 and the second sealing area 9 is transported to the adsorption / desorption device through the suction device. On the one hand, the dichloromethane gas in the extraction tank 5 will not be discharged into the workshop, reducing the loss of dichloromethane and preventing the harm to the on-site workers caused by the volatilization of dichloromethane. On the other hand, the dichloromethane flow rate transported to the adsorption / desorption device is small, which slows down the adsorption saturation speed of the adsorption / desorption core and ensures the long-term effective operation of the adsorption and desorption core.

[0058] The present invention also proposes a lithium battery diaphragm production extraction entrance protection method, which adjusts the air pressure in the first suction chamber and the second suction chamber by adjusting the operating frequency of the suction device. The method includes the following steps:

[0059] S1: Obtain the gas pressure values ​​of the first suction chamber 8 and the second suction chamber 9.

[0060] In a specific implementation, in this embodiment, air pressure sensors can be installed in the first suction chamber 8 and the second suction chamber 9 to measure the gas pressure values ​​in the first suction chamber 8 and the second suction chamber 9, and one of them can be selected as the atmosphere pressure value.

[0061] S2: Determine the target pressure value and the atmosphere pressure value, and control the operating state of the suction device.

[0062] If the atmosphere pressure value is less than the first target pressure threshold, the control device controls the suction device to reduce the frequency at a predetermined frequency reduction speed until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency reduction is stopped.

[0063] If the atmosphere pressure value is greater than the second target pressure threshold, the control device controls the suction device to increase the frequency at a predetermined frequency increase rate until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency increase is stopped.

[0064] If the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, the air suction device is controlled to maintain the current frequency operation and continue to monitor the atmosphere pressure value.

[0065] The frequency reduction rate and frequency increase rate can be set according to actual needs. The predetermined frequency reduction rate and the predetermined frequency increase rate can be equal or different. For example, the predetermined frequency reduction rate is 1Hz / s and the predetermined frequency increase rate is 2Hz / s. If the frequency is reduced to the lowest frequency, the suction devices are turned off one by one. If the frequency is increased to the highest frequency, the highest frequency operation is maintained.

[0066] In this embodiment, the operating frequency of the air suction device is controlled by the control device so that the atmosphere pressure value is within a preset range, wherein the first pressure threshold and the second pressure threshold are the above-mentioned preset ranges. The first pressure threshold and the second pressure threshold in this embodiment can be set according to actual needs, and the embodiment of the present invention does not specifically limit them.

[0067] The embodiment of the present invention obtains the gas pressure values ​​of the first suction chamber and the second suction chamber, selects one of the gas pressure values ​​as the atmosphere pressure value, and then judges the size of the atmosphere pressure value and the target atmosphere pressure threshold value, and controls the suction device to increase or decrease the frequency based on the judgment result, so that the air pressure values ​​of the first suction chamber and the second suction chamber are within a preset range, thereby achieving the purpose of adjusting the air pressure of the first suction chamber and the second suction chamber.

[0068] Based on the same inventive concept, this embodiment provides an extraction tank negative pressure protection control device, which can be used to implement the extraction inlet protection method for lithium battery diaphragm production. The extraction tank negative pressure protection control device can be implemented by software and hardware.

[0069] The extraction tank negative pressure protection control device comprises:

[0070] The control module is used to control the frequency of the air suction device according to the atmosphere pressure so that the atmosphere pressure value is within a preset range.

[0071] The control module comprises:

[0072] The monitoring unit includes air pressure sensors installed in the first suction chamber 8 and the second suction chamber 9 respectively, and the air pressure sensors are used to monitor the gas pressure values ​​in the first suction chamber 8 and the second suction chamber 9.

[0073] A control unit is used to control the air suction device to reduce the frequency at a predetermined frequency reduction rate if the atmosphere pressure value is less than a first pressure threshold, until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and then the frequency reduction is stopped; and to control the air suction device to increase the frequency at a predetermined frequency increase rate if the atmosphere pressure value is greater than the second pressure threshold, until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and then the frequency increase is stopped; and to control the air suction device to maintain the current frequency operation and return to the monitoring unit to continue monitoring the atmosphere pressure value if the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold.

[0074] The above extraction tank negative pressure protection control device can execute the lithium battery diaphragm production extraction inlet protection method provided by the embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the above method. For technical details not fully described in this embodiment, please refer to the extraction tank negative pressure protection control method provided by the embodiment of the present invention.

[0075] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for protecting the extraction entrance of lithium battery diaphragm production, characterized in that: The method comprises: A first transmission roller and a second transmission roller for pulling the film are arranged at the film entrance of the extraction tank. The first transmission roller and the second transmission roller are staggered in the traveling direction of the film, and are enclosed with the film, the extraction tank and the frame on the extraction tank to form a first sealing area and a second sealing area. The film is located between the first sealing area and the second sealing area. The first sealed area and the second sealed area are subjected to suction treatment by the air suction device, so that the volatilized dichloromethane gas in the extraction tank and the indoor air enter the first sealed area and the second sealed area; Obtain the gas pressure values ​​of the first sealing area and the second sealing area, and select one of them as the atmosphere pressure value; The frequency of the air suction device is controlled according to the atmosphere pressure value so that the atmosphere pressure value is within a preset range.

2. The lithium battery diaphragm production extraction inlet protection method according to claim 1, characterized in that: Controlling the frequency of the air suction device according to the atmosphere pressure value so that the atmosphere pressure value is within a preset range includes: If the atmosphere pressure value is less than the first target pressure threshold, the control device controls the air suction device to reduce the frequency at a predetermined frequency reduction speed until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency reduction is stopped; If the atmosphere pressure value is greater than the second target pressure threshold, the control device controls the air suction device to increase the frequency at a predetermined frequency increase rate until the actual atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and the frequency increase is stopped; If the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, the air suction device is controlled to maintain the current frequency operation and continue to monitor the atmosphere pressure value.

3. A lithium battery diaphragm production extraction protection system, characterized in that: The system includes an extraction tank protection device and a control device. The extraction tank protection device includes a frame, a drive roller group and an air suction device. The frame is installed on the extraction tank and is located at the membrane inlet side of the extraction tank; the drive roller group includes a first drive roller and a second drive roller for pulling the film, the first drive roller and the second drive roller are staggered in the traveling direction of the film, and are enclosed with the frame, the film and the extraction tank to form a first sealing area and a second sealing area, the first sealing area and the second sealing area are respectively located on both sides of the film, and are connected to the membrane inlet of the extraction tank; the air suction device is connected to the first sealing area and the second sealing area respectively, and is used to suck dichloromethane gas and air into the first sealing area and the second sealing area; the control device is used to measure the atmosphere pressure of the first sealing area and the second sealing area, and calculate the level that the air suction device should suck based on the atmosphere pressure, and change or maintain the suction level based on the calculated result.

4. The lithium battery diaphragm production extraction protection system according to claim 3, characterized in that: The frame includes a first sealing structure and a second sealing structure, the first sealing structure includes a first ventilation pipe and two sealing members, the first ventilation pipe, the two sealing members and the first transmission roller form a first suction chamber in the first sealing area; the second sealing structure includes a second ventilation pipe and two sealing members, the second ventilation pipe, the two sealing members and the second transmission roller form a second suction chamber in the second sealing area; The control device is used to measure the atmospheric pressure of the first suction chamber and the second suction chamber, calculate the level that the suction device should suck based on the atmospheric pressure, and change or maintain the suction level based on the calculated result.

5. The lithium battery diaphragm production extraction protection system according to claim 4, characterized in that: The control device comprises a monitoring unit and a control unit; The monitoring unit comprises air pressure sensors respectively installed in the first air suction chamber and the second air suction chamber, and the air pressure sensors are used to monitor the gas pressure values ​​in the first air suction chamber and the second air suction chamber; A control unit is used to control the air suction device to reduce the frequency at a predetermined frequency reduction rate if the atmosphere pressure value is less than a first pressure threshold, until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and then the frequency reduction is stopped; and to control the air suction device to increase the frequency at a predetermined frequency increase rate if the atmosphere pressure value is greater than the second pressure threshold, until the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold, and then the frequency increase is stopped; and to control the air suction device to maintain the current frequency operation and return to the monitoring unit to continue monitoring the atmosphere pressure value if the atmosphere pressure value is greater than or equal to the first pressure threshold and less than or equal to the second pressure threshold.

6. The lithium battery diaphragm production extraction protection system according to claim 4, characterized in that: The two seals of the first sealing structure and the two seals of the second sealing structure are arranged in an "eight" shape.

7. The lithium battery diaphragm production extraction protection system according to claim 4, characterized in that: The gap between the sealing element and the transmission roller is 0.01-10 mm.

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