Electromagnetic shielding structure and preparation method

Abstract

The invention relates to the technical field of electromagnetic shielding, in particular to an electromagnetic shielding structure and a preparation method thereof.The preparation method comprises the steps that a conductive foaming rubber sheet is placed in a foaming kettle, carbon dioxide is introduced to remove air in the foaming kettle, the pressure in the foaming kettle is controlled to be normal pressure, and the foaming kettle is placed in an oil bath pan; the oil bath pan is heated, and the oil bath pan is heated to a preset temperature and kept constant; the flow of the introduced carbon dioxide when the air pressure reaches the preset air pressure serves as the preset flow and is kept; and opening the pressure release valve, when the temperature in the foaming kettle is reduced to a preset packaging temperature, enabling the packaging layer to be in contact with the surface of the conductive polystyrene foam material, after the packaging layer and the conductive polystyrene foam material are stable, placing the foaming kettle in an ice-water bath for cooling and shaping, and pasting the bonding layer on the composite conductive layer to prepare the electromagnetic shielding structure. The electrical conductivity and the electromagnetic shielding property of the prepared electromagnetic shielding structure can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding, and in particular to an electromagnetic shielding structure and a preparation method thereof. Background Art

[0002] Conductive foam is a gap shielding material that is light, compressible and conductive. It is often used in gaps in electronic and electrical equipment to provide conductive connections and shielding. With the continuous upgrading of shielding devices, higher and higher requirements are placed on the performance of conductive foam. Therefore, it is necessary to control various parameters in the preparation process to ensure the foaming and preparation process.

[0003] Chinese Patent Publication No.: CN116606598A discloses a process for preparing ultra-thin shock-absorbing conductive foam, the preparation of which includes the following steps: S1, preparation of raw materials: preparing two kinds of raw materials for conductive foam, namely conductive cloth and conductive foaming rubber material, and cutting them separately according to the specifications of the finished product; the conductive foaming rubber material is made of thermoplastic polyurethane as a matrix, graphene, carbon black, silver powder and multi-walled carbon nanotube conductive fillers are added to the thermoplastic polyurethane matrix, and is prepared by supercritical CO2 foaming; S2, molding; S3, applying release paper; It can be seen that the process for preparing ultra-thin shock-absorbing conductive foam has the following problems: the invention only provides process parameters, and is unable to control the specific preparation process of the conductive foam, resulting in a relatively poor electromagnetic shielding effect of the electromagnetic shielding structure obtained. Summary of the invention

[0004] To this end, the present invention provides an electromagnetic shielding structure and a preparation method thereof, so as to overcome the problem that the electromagnetic shielding structure in the prior art has a relatively poor shielding effect.

[0005] To achieve the above object, the present invention provides a method for preparing an electromagnetic shielding structure, which is characterized by comprising:

[0006] Step S1, placing the conductive foam rubber sheets in a foaming kettle, introducing carbon dioxide to remove the air inside the foaming kettle, controlling the pressure inside the foaming kettle to be normal, and placing the foaming kettle in an oil bath;

[0007] Step S2, heating the oil bath pot, detecting the temperature of the foaming kettle, and determining the first characteristic point and the time of introducing carbon dioxide based on the comparison between the difference between the temperature of the foaming kettle and the preset ventilation temperature and the preset temperature difference;

[0008] Step S3, continuously introducing carbon dioxide gas into the foaming kettle, detecting the flow rate of the introduced carbon dioxide gas and the gas pressure in the foaming kettle, and heating the oil bath pot to a preset temperature and maintaining it constant;

[0009] Step S4, determining a second characteristic point and a time to reduce the flow rate of carbon dioxide based on a comparison result of the slope of the pressure curve in the foaming kettle with a preset slope;

[0010] Step S5, determining a method for adjusting the flow rate of carbon dioxide based on the rate of change of the air pressure in the foaming kettle at the time corresponding to the second characteristic point, and taking the flow rate of carbon dioxide introduced when the air pressure reaches a preset pressure as a preset flow rate and maintaining it;

[0011] Step S6, determining the time to stop introducing carbon dioxide based on the comparison between the difference between the air pressure in the foaming kettle and the preset air pressure and the preset air pressure difference;

[0012] Step S7, opening the pressure relief valve, when the temperature in the foaming kettle drops to a preset packaging temperature, bringing the packaging layer into contact with the surface of the conductive foaming material, and after the packaging layer and the conductive foaming material are stabilized, placing the foaming kettle in an ice water bath to cool and shape, thereby obtaining a composite conductive layer;

[0013] Step S8, attaching an adhesive layer to the composite conductive layer to obtain an electromagnetic shielding structure.

[0014] Further, in step S2, when it is detected that the difference between the temperature of the foaming kettle and the preset ventilation temperature is less than the preset temperature difference and lasts for a first time period, the point on the air pressure curve corresponding to this moment is determined as the first characteristic point.

[0015] Furthermore, in the step S2, the time corresponding to the first characteristic point is determined as the time for introducing carbon dioxide.

[0016] Furthermore, in step S4, when the slope of the pressure curve in the foaming kettle is less than or equal to the preset slope, the point on the pressure curve corresponding to that moment is determined as the second characteristic point, and the preset slope is determined according to the pressure change rate in the foaming kettle.

[0017] Furthermore, in the step S4, the time corresponding to the second characteristic point is determined as the time for reducing the flow rate of the introduced carbon dioxide.

[0018] Furthermore, in the step S5, the air pressure change rate is determined according to the air pressure change amount in the foaming kettle within a preset time period, and the adjustment method of the carbon dioxide flow rate corresponds to the air pressure change rate.

[0019] Furthermore, in the step S6, when the difference between the air pressure in the foaming kettle and the preset air pressure is greater than the preset air pressure difference, this moment is determined as the moment to stop introducing carbon dioxide.

[0020] Furthermore, in step S7, the curing temperature of the encapsulation layer is lower than the preset encapsulation temperature; when the temperature in the foaming kettle drops to the curing temperature, the corresponding moment is the moment when the encapsulation layer is cured and in contact with the conductive foam material.

[0021] The present invention also provides an electromagnetic shielding structure, wherein a single electromagnetic shielding structure comprises:

[0022] A composite conductive layer, comprising a packaging layer and a conductive foam layer, wherein the packaging layer is connected to the conductive foam layer;

[0023] The adhesive layer is connected to the composite conductive layer and is used to fix the composite conductive layer and the surface requiring electromagnetic shielding.

[0024] Furthermore, each of the electromagnetic shielding structures is connected via a snap-fit ​​structure of the electromagnetic shielding structure, and the snap-fit ​​structure includes a snap-fit ​​portion and a snap-fit ​​portion that are arranged opposite to each other.

[0025] Compared with the prior art, the beneficial effect of the present invention lies in that, by determining the moment of introducing carbon dioxide, the method for preparing an electromagnetic shielding structure of the present invention avoids the formation of bubbles rather than effective dissolution by introducing carbon dioxide in advance at a lower temperature, thereby affecting the final foaming effect, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor and precise control of the foaming process of the electromagnetic shielding structure preparation method; at the same time, by controlling in advance to reduce the flow rate of carbon dioxide introduced, the flow rate of carbon dioxide drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, thereby ensuring the foaming effect; by making the air pressure change rate in the foaming kettle correspond to the adjustment method of the carbon dioxide flow rate, the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure is achieved, and at the same time, by determining the moment of stopping the introduction of carbon dioxide, so as to carry out the best foaming process subsequently, the safety problems caused by the increase of the air pressure in the foaming kettle and the influence on the subsequent foaming effect are avoided, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained.

[0026] Furthermore, the present invention comprehensively determines the first characteristic point based on the comparison result of the difference between the temperature of the oil bath pot and the preset ventilation temperature and the preset temperature difference, and the duration detection for the first duration, so as to accurately determine the time of introducing carbon dioxide subsequently, thereby avoiding the temperature of the oil bath pot possibly causing a sudden increase in the temperature of the oil bath pot for a certain period of time due to actual conditions (including unstable heating in the initial stage of heating, etc.), resulting in the first characteristic point being erroneously determined and judged as the time of introducing carbon dioxide only when the difference between the temperature of the oil bath pot and the preset ventilation temperature is less than the preset temperature difference for a certain period of time, causing the subsequent carbon dioxide to dissolve in the conductive foaming material under low temperature conditions, which may destroy the internal structure of the conductive foaming material and ineffectively dissolve, resulting in poor subsequent foaming effect and affecting the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure, thereby improving the accuracy of the subsequent determination of the time of introducing carbon dioxide, ensuring the conductivity and electromagnetic shielding performance of the obtained electromagnetic shielding structure, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0027] Furthermore, the method for preparing an electromagnetic shielding structure of the present invention clarifies the starting point of the absorption and dissolution process by determining the moment corresponding to the first characteristic point as the moment of introducing carbon dioxide, so that the carbon dioxide can fully contact the conductive foam material at an appropriate temperature to undergo a physical dissolution reaction; foaming is carried out in a heated environment, which not only increases the control of the reactants, but also ensures that the temperature is maintained in a suitable range throughout the process, reducing unnecessary temperature fluctuations, and at the same time, heating the oil bath to a suitable dissolution temperature can increase the reaction temperature and reaction rate, and improve the efficiency of the conductive foam material in dissolving carbon dioxide, thereby promoting better dissolution of carbon dioxide in polyurethane, avoiding the direct introduction of carbon dioxide at a lower temperature to form bubbles rather than effective dissolution, thereby affecting the final foaming effect, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0028] Furthermore, the method for preparing an electromagnetic shielding structure of the present invention determines the moment when the air pressure in the foaming kettle will reach the preset air pressure by determining the second characteristic point, so as to control and reduce the flow rate of carbon dioxide in advance, so that the flow rate of carbon dioxide drops to a constant value when the air pressure in the foaming kettle will reach the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, and avoid the situation where the flow rate of carbon dioxide cannot be quickly controlled when the air pressure in the foaming kettle reaches the preset air pressure, resulting in excessive air pressure in the foaming kettle, affecting the absorption and dissolution of carbon dioxide, foaming effect and safety problems, thereby ensuring the safety of the preparation process, improving the foaming effect, ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0029] Furthermore, the method for preparing an electromagnetic shielding structure of the present invention determines the moment of introducing the carbon dioxide flow rate to control and reduce the carbon dioxide flow rate in advance, so that the carbon dioxide flow rate drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve a dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, and avoids the situation where the carbon dioxide flow rate cannot be quickly controlled when the air pressure in the foaming kettle reaches the preset air pressure, causing the air pressure in the foaming kettle to be too high, affecting the absorption and dissolution of carbon dioxide, foaming effect and causing safety problems, thereby ensuring the safety of the preparation process, improving the foaming effect, ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0030] Furthermore, the electromagnetic shielding structure preparation method of the present invention determines the adjustment method for the carbon dioxide flow rate, and makes the air pressure change rate in the foaming kettle correspond to the adjustment method for the carbon dioxide flow rate, and controls the carbon dioxide flow rate and the air pressure in the foaming kettle by adjusting the adjustment method for the carbon dioxide flow rate in real time, so that the carbon dioxide flow rate drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0031] Furthermore, the method for preparing an electromagnetic shielding structure of the present invention determines the moment to stop introducing carbon dioxide so as to carry out the optimal foaming process subsequently, thereby avoiding safety problems caused by the increase in gas pressure in the foaming kettle and affecting the subsequent foaming effect, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained.

[0032] Furthermore, the electromagnetic shielding structure preparation method of the present invention accelerates the curing reaction rate, reduces the curing time, and improves the efficiency of the electromagnetic shielding structure preparation process by adding an adhesive to finally form the composite conductive layer when the foaming kettle drops to the curing temperature.

[0033] Furthermore, the electromagnetic shielding structure of the present invention ensures the conductivity and electromagnetic shielding effect as well as the protection of the conductive foam layer by providing the packaging layer and the conductive foam layer as the composite conductive layer, thereby increasing the service life. At the same time, the adhesive layer is provided to achieve the adhesiveness and practicality of the electromagnetic shielding structure.

[0034] Furthermore, the electromagnetic shielding structure of the present invention connects adjacent electromagnetic shielding structures by providing a snap-fit ​​structure, thereby preventing the electromagnetic shielding structure from loosening and adjacent electromagnetic shielding structures from disconnecting, which would cause damage to the closed-circuit structure of the electromagnetic shielding structure during actual use and lead to failure of the electromagnetic shielding, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The following is a flowchart of a method for preparing an electromagnetic shielding structure according to an embodiment of the present invention;

[0036] Figure 2 A logic judgment diagram for determining a first characteristic point in an embodiment of the present invention;

[0037] Figure 3 A logic judgment diagram for determining a second characteristic point according to an embodiment of the present invention;

[0038] Figure 4 It is a schematic structural diagram of an electromagnetic shielding structure according to an embodiment of the present invention;

[0039] In the figure: 1, composite conductive layer; 11, packaging layer; 12, conductive foam layer; 2, adhesive layer; 3, slot portion; 4, buckle portion. DETAILED DESCRIPTION

[0040] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0042] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0043] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] See also Figure 1 As shown, it is a workflow diagram of the method for preparing the electromagnetic shielding structure according to an embodiment of the present invention.

[0045] An embodiment of the present invention provides a method for preparing an electromagnetic shielding structure, comprising:

[0046] Step S1, placing the conductive foam rubber sheets in a foaming kettle, introducing carbon dioxide to remove the air inside the foaming kettle, controlling the pressure inside the foaming kettle to be normal, and placing the foaming kettle in an oil bath;

[0047] Step S2, heating the oil bath pot, detecting the temperature of the foaming kettle, and determining the first characteristic point and the time of introducing carbon dioxide based on the comparison between the difference between the temperature of the foaming kettle and the preset ventilation temperature and the preset temperature difference;

[0048] Step S3, continuously introducing carbon dioxide gas into the foaming kettle, detecting the flow rate of the introduced carbon dioxide gas and the gas pressure in the foaming kettle, and heating the oil bath pot to a preset temperature and maintaining it constant;

[0049] Step S4, determining a second characteristic point and a time to reduce the flow rate of carbon dioxide based on a comparison result of the slope of the pressure curve in the foaming kettle with a preset slope;

[0050] Step S5, determining a method for adjusting the flow rate of carbon dioxide based on the rate of change of the air pressure in the foaming kettle at the time corresponding to the second characteristic point, and taking the flow rate of carbon dioxide introduced when the air pressure reaches a preset pressure as a preset flow rate and maintaining it;

[0051] Step S6, determining the time to stop introducing carbon dioxide based on the comparison between the difference between the air pressure in the foaming kettle and the preset air pressure and the preset air pressure difference;

[0052] Step S7, opening the pressure relief valve, when the temperature in the foaming kettle drops to a preset packaging temperature, bringing the packaging layer into contact with the surface of the conductive foaming material, and after the packaging layer and the conductive foaming material are stabilized, placing the foaming kettle in an ice water bath to cool and shape, thereby obtaining a composite conductive layer;

[0053] Step S8, attaching an adhesive layer to the composite conductive layer to obtain an electromagnetic shielding structure.

[0054] It can be understood that by heating the oil bath pot, the heat is transferred to the foaming kettle, so that the temperature of the foaming kettle is increased, and carbon dioxide is introduced at the time of introducing carbon dioxide, and the gas pressure of the foaming kettle is increased; when the temperature of the foaming kettle is greater than the critical temperature and the gas pressure is greater than the critical gas pressure, the carbon dioxide is above the critical point, and the state changes from gas to supercritical fluid, and the carbon dioxide begins to dissolve in the conductive foaming material, that is, the absorption and dissolution phenomenon, and the gas pressure of the foaming kettle is reduced. In order to maintain the gas pressure to ensure the absorption and dissolution effect and the foaming effect, carbon dioxide gas needs to be continuously filled; and before foaming, it is necessary to maintain a preset gas pressure and a preset temperature in the foaming kettle for a period of time so that the carbon dioxide The carbon dioxide is fully dissolved in the conductive foaming material; after the absorption and dissolution are completed, the pressure relief valve is opened, and when a great pressure drop is caused in a short time, the air pressure in the foaming kettle is quickly released, and the dissolved carbon dioxide will instantly expand and form bubbles to promote the foaming process; after the pressure relief valve is opened, the temperature in the foaming kettle drops rapidly at the same time, and when the temperature drops to the curing temperature of the encapsulation layer, the encapsulation layer is contacted with the conductive foaming material, and the excess heat of the foaming kettle is used to connect the encapsulation layer and the conductive foaming material into one body to form the composite conductive layer, and the foaming kettle is placed in an ice water bath after stabilization, so that the encapsulation layer and the conductive foaming material are cooled and shaped to obtain the composite conductive layer.

[0055] It is understood that supercritical fluids have some properties of both gases and liquids, including the ability to permeate and dissolve certain substances at high densities similar to liquids while having mobility similar to gases.

[0056] In this embodiment, the introduced gas is carbon dioxide, and the conductive foam material includes a thermoplastic polyurethane matrix. The carbon dioxide interacts with the thermoplastic polyurethane matrix and is dissolved in the conductive foam material.

[0057] It is understandable that it is known that the critical temperature of carbon dioxide is 31.1°C and the critical pressure is 7.38 MPa.

[0058] It is understandable that the preset air pressure is an appropriate air pressure to ensure optimal foaming, which is determined based on actual conditions, including the properties and quality of the conductive foaming material, the external ambient temperature, and the design of the foaming kettle.

[0059] It is understandable that the preset temperature is determined according to actual conditions, including the properties and quality of the conductive foam material, the external environment temperature and the design of the foaming kettle.

[0060] In this embodiment, the preset air pressure value range is set to 10MPa-16MPa, the preset temperature value range is set to 80°C-120°C, and the foaming kettle is placed in an ice water bath for 1min-10min.

[0061] In a specific embodiment, the preset air pressure is 15 MPa, the preset temperature is 100° C., and the foaming kettle is placed in an ice water bath for 8 minutes.

[0062] The electromagnetic shielding structure preparation method of the present invention avoids the formation of bubbles rather than effective dissolution of carbon dioxide at a relatively low temperature by determining the time of introducing carbon dioxide, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor and precise control of the foaming process of the electromagnetic shielding structure preparation method; at the same time, by controlling in advance to reduce the flow rate of carbon dioxide introduced, the flow rate of carbon dioxide drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, thereby ensuring the foaming effect; by making the air pressure change rate in the foaming kettle correspond to the adjustment method of the carbon dioxide flow rate, the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure is achieved, and at the same time, by determining the time of stopping the introduction of carbon dioxide so as to carry out the best foaming process subsequently, the safety problems caused by the increase of the air pressure in the foaming kettle and the influence on the subsequent foaming effect are avoided, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained.

[0063] See also Figure 2 As shown, it is a logical judgment diagram for determining the first feature point in an embodiment of the present invention.

[0064] Specifically, in step S2, when it is detected that the difference between the temperature of the foaming kettle and the preset ventilation temperature is less than the preset temperature difference and lasts for a first period of time, the point on the air pressure curve corresponding to this moment is determined as the first characteristic point.

[0065] It is understandable that if it is detected that the difference between the temperature of the oil bath pot and the preset ventilation temperature is less than the preset temperature difference but does not last for the first time period, no operation is performed;

[0066] If it is detected that the difference between the temperature of the oil bath and the preset ventilation temperature is greater than the preset temperature difference, no operation is performed.

[0067] In this embodiment, the preset ventilation temperature value range is set to 28°C to 40°C, the preset temperature difference value range is set to 2°C to 5°C, and the first time length value range is set to 5s to 60s.

[0068] The present invention comprehensively determines the first characteristic point based on the comparison result of the difference between the temperature of the oil bath pot and the preset ventilation temperature and the preset temperature difference, and the duration detection of the first duration, so as to accurately determine the time of introducing carbon dioxide subsequently, thereby avoiding the situation that the temperature of the oil bath pot may suddenly increase at several moments due to actual conditions including unstable heating in the initial stage of heating, resulting in the difference between the temperature of the oil bath pot and the preset ventilation temperature being less than the preset temperature difference only at several moments, and the first characteristic point is erroneously determined and judged as the time of introducing carbon dioxide, causing the subsequent carbon dioxide to dissolve in the conductive foaming material under low temperature conditions, which may destroy the internal structure of the conductive foaming material and ineffectively dissolve, resulting in poor subsequent foaming effect and affecting the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure, thereby improving the accuracy of the subsequent determination of the time of introducing carbon dioxide, ensuring the conductivity and electromagnetic shielding performance of the obtained electromagnetic shielding structure, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0069] Specifically, in step S2, the time corresponding to the first characteristic point is determined as the time for introducing carbon dioxide.

[0070] It is understandable that before the oil bath is heated to the preset ventilation temperature, the temperature of the foaming kettle is too low. If carbon dioxide is introduced at this time, it will be detrimental to the dissolution of carbon dioxide in polyurethane, and will affect the material properties of the conductive foam material, and affect the elasticity, compressive strength, conductivity and other properties of the final composite conductive layer.

[0071] The electromagnetic shielding structure preparation method of the present invention clarifies the starting point of the absorption and dissolution process by determining the moment corresponding to the first characteristic point as the moment of introducing carbon dioxide, so that the carbon dioxide can fully contact the conductive foam material at an appropriate temperature to undergo a physical dissolution reaction; foaming is carried out in a heated environment, which not only increases the control of the reactants, but also ensures that the temperature is maintained in a suitable range throughout the process, reducing unnecessary temperature fluctuations. At the same time, the oil bath is first heated to a suitable dissolution temperature, which can increase the reaction temperature and reaction rate, and improve the efficiency of the conductive foam material in dissolving carbon dioxide, thereby promoting better dissolution of carbon dioxide in polyurethane, avoiding the direct introduction of carbon dioxide at a lower temperature to form bubbles rather than effective dissolution, thereby affecting the final foaming effect, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0072] See also Figure 3 As shown, it is a logical judgment diagram for determining the second feature point in an embodiment of the present invention.

[0073] Specifically, in step S4, when the slope of the pressure curve in the foaming kettle is less than or equal to the preset slope, the point on the pressure curve corresponding to that moment is determined as the second characteristic point, and the preset slope is determined according to the pressure change rate in the foaming kettle.

[0074] It can be understood that when the slope of the air pressure curve in the foaming kettle is greater than the preset slope, no operation is performed.

[0075] In this embodiment, the preset slope value range is set to 0.05-0.2.

[0076] It is understandable that the gas pressure in the foaming kettle can be changed by adjusting the flow rate of carbon dioxide.

[0077] It can be understood that the slope of the air pressure curve in the foaming kettle is determined according to the air pressure change rate in the foaming kettle, and the air pressure change rate is determined according to the amount of change of the air pressure in the foaming kettle within a preset time period, reflecting the speed of change of the air pressure in the foaming kettle. By determining the moment when the slope of the air pressure curve in the foaming kettle is greater than the preset slope, the second characteristic point and the moment of reducing the flow rate of carbon dioxide are determined.

[0078] It is understandable that in order to ensure the accuracy of the calculated air pressure change rate, the preset time length needs to be reduced as much as possible. In this embodiment, the preset time length is greater than 0s and less than 2s.

[0079] The method for preparing an electromagnetic shielding structure of the present invention determines the moment when the air pressure in the foaming kettle will reach the preset air pressure by determining the second characteristic point, so as to control and reduce the flow rate of carbon dioxide in advance, so that the flow rate of carbon dioxide drops to a constant value when the air pressure in the foaming kettle will reach the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, and avoid the situation where the flow rate of carbon dioxide cannot be quickly controlled when the air pressure in the foaming kettle reaches the preset air pressure, resulting in excessive air pressure in the foaming kettle, affecting the absorption and dissolution of carbon dioxide, foaming effect and causing safety problems, thereby ensuring the safety of the preparation process, improving the foaming effect, ensuring the conductivity and electromagnetic shielding performance of the prepared electromagnetic shielding structure, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0080] Specifically, in step S4, the time corresponding to the second characteristic point is determined as the time for reducing the flow rate of carbon dioxide.

[0081] It is understandable that the air pressure during the foaming process needs to be set at a preset air pressure, and the dissolution effect of carbon dioxide in polyurethane and the final foaming effect are best under the preset air pressure.

[0082] When the air pressure in the foaming kettle is about to reach the preset air pressure, since the control of the introduction of carbon dioxide has a delay, the flow rate of carbon dioxide needs to be reduced in advance, that is, this moment is the moment of reducing the flow rate of carbon dioxide introduction, and the flow rate is reduced to the preset flow rate, so that the air pressure in the foaming kettle can steadily reach the preset air pressure and maintain it, ensuring that the flow rate of carbon dioxide in the subsequent foaming process is maintained at the preset flow rate and the air pressure is maintained at the preset pressure, thereby meeting the optimal air pressure conditions for foaming.

[0083] It is understandable that when the flow rate of carbon dioxide is maintained at the preset flow rate, the carbon dioxide in gaseous form reduced by the dissolution reaction of carbon dioxide with the conductive foaming material is offset by the introduced carbon dioxide, so that the gas pressure in the foaming kettle maintains a dynamic balance.

[0084] The method for preparing an electromagnetic shielding structure of the present invention determines the moment of introducing the carbon dioxide flow rate to control and reduce the introduced carbon dioxide flow rate in advance, so that the carbon dioxide flow rate drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve a dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, and avoids the situation where the carbon dioxide flow rate cannot be quickly controlled when the air pressure in the foaming kettle reaches the preset air pressure, causing the air pressure in the foaming kettle to be too high, affecting the absorption and dissolution of carbon dioxide, foaming effect and causing safety problems, thereby ensuring the safety of the preparation process, improving the foaming effect, ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0085] Specifically, in step S5, the air pressure change rate is determined according to the air pressure change amount in the foaming kettle within a preset time period, and the adjustment method of the carbon dioxide flow rate corresponds to the air pressure change rate.

[0086] It can be understood that the preset flow rate is determined according to the actual fermentation conditions, including the properties, type, quality, etc. of the fermentation liquid. The preset flow rate can maintain the air pressure in the foaming kettle at the preset air pressure, that is, the content of carbon dioxide gas absorbed and dissolved in the conductive foam material is the same as the flow rate introduced, maintaining dynamic balance.

[0087] It can be understood that reducing the flow rate of carbon dioxide introduced reduces the difference between the flow rate of carbon dioxide introduced and the consumption flow rate of carbon dioxide in gaseous form by the dissolution reaction of the foaming material, thereby slowing down the rate of change of air pressure in the foaming kettle. In the present embodiment, the growth rate of air pressure becomes smaller, and the method of adjusting the carbon dioxide flow rate corresponds to the air pressure change rate.

[0088] The electromagnetic shielding structure preparation method of the present invention determines the adjustment method for the carbon dioxide flow rate, and makes the air pressure change rate in the foaming kettle correspond to the adjustment method for the carbon dioxide flow rate. The carbon dioxide flow rate and the air pressure in the foaming kettle are controlled by adjusting the adjustment method for the carbon dioxide flow rate in real time, so that the carbon dioxide flow rate drops to a constant value when the air pressure in the foaming kettle reaches the preset air pressure, so as to achieve the dynamic balance of the air pressure in the foaming kettle during the subsequent absorption and dissolution of carbon dioxide under the preset air pressure, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained, and improving the process rigor of the electromagnetic shielding structure preparation method and the precise control of the foaming process.

[0089] Specifically, in step S6, when the difference between the air pressure in the foaming kettle and the preset air pressure is greater than the preset air pressure difference, this moment is determined as the moment to stop introducing carbon dioxide.

[0090] It is understandable that, if in step S6, if the difference between the air pressure in the foaming kettle and the preset air pressure is less than or equal to the preset air pressure difference, no adjustment is made.

[0091] In this embodiment, the preset air pressure difference value range is set to 0.05Mpa to 0.1Mpa.

[0092] It can be understood that the step S6 is to determine the time to stop introducing carbon dioxide after the carbon dioxide is completely absorbed and dissolved in the conductive foam material.

[0093] When the carbon dioxide is completely dissolved in the foaming material, this is the best time for foaming. If carbon dioxide continues to be introduced at this time, the air pressure will further increase, which will increase the solubility of carbon dioxide gas, resulting in the inability of carbon dioxide to quickly turn into gas when released, affecting the subsequent foam formation and the foaming effect. At the same time, it will cause the components of the foaming system, including the foaming kettle, pipelines, valves, etc., to be unable to withstand excessive air pressure, resulting in equipment rupture, leakage or other mechanical failures, posing a safety hazard.

[0094] When it is detected that the difference between the air pressure in the foaming kettle and the preset air pressure is greater than the preset air pressure difference, the air pressure fluctuation in the normal dynamic dissolution process is eliminated, and it is judged that the carbon dioxide absorption and dissolution process is completed. This is the moment to stop introducing carbon dioxide, thereby ensuring the foaming effect and avoiding safety problems caused by excessive air pressure in the foaming kettle.

[0095] The method for preparing an electromagnetic shielding structure of the present invention determines the moment to stop introducing carbon dioxide so as to perform the optimal foaming process subsequently, thereby avoiding safety problems caused by increased air pressure in the foaming kettle and affecting subsequent foaming effects, thereby ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure obtained.

[0096] Specifically, in step S7, the curing temperature of the encapsulation layer is lower than the preset encapsulation temperature; when the temperature in the foaming kettle drops to the curing temperature, the corresponding moment is the moment when the encapsulation layer is cured and in contact with the conductive foam material.

[0097] In this embodiment, the packaging layer includes an adhesive to protect the conductive foam material to avoid being damaged by the external environment.

[0098] It can be understood that the preset packaging temperature is determined according to the accelerated curing temperature of the adhesive.

[0099] In this embodiment, the adhesive is polyester resin, and the accelerated curing temperature, ie, the preset packaging temperature, is set in the range of 60° C. to 80° C.

[0100] It can be understood that, in a heated state, the adhesive absorbs heat and increases molecular kinetic energy, thereby increasing the rate of chemical reactions; and heating can increase the fluidity of the glue, making it easier for it to penetrate into the bonded surface, which further enhances the bonding strength; the type and quality of the adhesive are determined based on actual conditions. If the adhesive is a polyurethane adhesive and contains a volatile solvent, heating helps to accelerate the volatilization of the solvent, thereby achieving faster drying and curing of the adhesive. Therefore, the adhesive cures faster in a heated state than at room temperature.

[0101] Therefore, the embodiment of the present invention increases the curing temperature of the adhesive to improve the curing rate and curing effect.

[0102] Therefore, in the embodiment of the present invention, when the foaming kettle drops to the curing temperature, an adhesive is added to the surface of the conductive foam material, so that the curing of the adhesive and the foaming process of the conductive foam material are carried out simultaneously, and the composite conductive layer is formed by cooling through an ice water bath.

[0103] It can be understood that the curing temperature is determined according to the type of the adhesive.

[0104] In a specific embodiment, the encapsulation layer also includes a protective shell. After the ice water bath cooling is completed, the protective shell is fixed to the surface of the cured adhesive to protect the adhesive and prevent the adhesive from being affected by temperature and absorbing heat to soften and affect performance or restore the adhesive effect to affect use.

[0105] In this embodiment, the adhesive layer includes release paper, which serves to adhere the composite conductive layer to a surface requiring electromagnetic shielding.

[0106] It can be understood that the size and number of layers of the packaging layer, the conductive foam material and the adhesive layer are determined according to actual conditions. Changes in the distribution of the packaging layer, the conductive foam material and the adhesive layer, changes in the number of layers, and alternative preparation methods and process steps all fall within the scope of protection of the present invention and will not be repeated here.

[0107] The electromagnetic shielding structure preparation method of the present invention accelerates the curing reaction rate, reduces the curing time, and improves the efficiency of the electromagnetic shielding structure preparation process by adding an adhesive to finally form the composite conductive layer when the foaming kettle drops to the curing temperature.

[0108] See also Figure 4 As shown, it is a schematic diagram of the structure of the electromagnetic shielding structure according to an embodiment of the present invention, which includes a composite conductive layer 1, a packaging layer 11, a conductive foam layer 12, an adhesive layer 2, a slot portion 3 and a buckle portion 4.

[0109] The embodiment of the present invention further provides an electromagnetic shielding structure prepared using the electromagnetic shielding structure preparation method, wherein a single electromagnetic shielding structure comprises:

[0110] The composite conductive layer 1 comprises a packaging layer 11 and a conductive foam layer 12, wherein the packaging layer 11 is connected to the conductive foam layer 12;

[0111] The adhesive layer 2 is connected to the composite conductive layer 1 and is used to fix the composite conductive layer 1 and the surface requiring electromagnetic shielding.

[0112] The conductive foam layer 12 is made by foaming a conductive foam material, wherein the conductive foam material includes several of a thermoplastic polyurethane matrix, carbon black, graphene, metal powder and multi-walled carbon nanotubes.

[0113] In a specific embodiment, the mass fractions of the components of the conductive foam material are: 95% of the foam matrix, 2.5% of the carbon black, 1.5% of the graphene, 0.5% of the metal powder, and 0.5% of the multi-walled carbon nanotubes.

[0114] The electromagnetic shielding structure of the present invention ensures the conductivity and electromagnetic shielding effect as well as the protection of the conductive foam layer by providing the packaging layer and the conductive foam layer as the composite conductive layer, thereby increasing the service life. At the same time, the adhesive layer is provided to achieve the adhesiveness and practicality of the electromagnetic shielding structure.

[0115] Specifically, the electromagnetic shielding structures are connected to each other via a snap-fit ​​structure of the electromagnetic shielding structure, and the snap-fit ​​structure includes a snap-fit ​​portion 3 and a snap-fit ​​portion 4 that are arranged opposite to each other.

[0116] It can be understood that the snap-on structure in the figure is only an example, and the specific shape and structure are not limited. When installing the electromagnetic shielding structure, the number and arrangement of the electromagnetic shielding structure are determined according to actual conditions. Adjacent electromagnetic shielding structures need to be connected in pairs to form a closed structure to achieve the electromagnetic shielding effect.

[0117] In this embodiment, the snap-on structure is divided into a snap-on portion 3 and a snap-on portion 4. The snap-on portion 4 is embedded in the snap-on portion 3 to form a snap-on structure to connect adjacent electromagnetic shielding structures and prevent the electromagnetic shielding structure from loosening and adjacent electromagnetic shielding structures from being disconnected, thereby causing failure of electromagnetic shielding.

[0118] It can be understood that, in this embodiment, the conductive foam material is mixed evenly and added to an internal mixer for mixing. After standing, it is hot-pressed into the conductive foam sheet by a tablet press and added to a foaming kettle. Carbon dioxide is introduced into the foaming kettle and a certain temperature and air pressure are maintained to dissolve the carbon dioxide in the conductive foam material. After the carbon dioxide has been dissolved, the pressure relief valve is opened to foam the conductive foam material to form the conductive foam layer 12.

[0119] The electromagnetic shielding structure of the present invention connects adjacent electromagnetic shielding structures by providing a snap-fit ​​structure, thereby preventing the electromagnetic shielding structure from loosening and adjacent electromagnetic shielding structures from being disconnected, thereby preventing the closed-circuit structure of the electromagnetic shielding structure from being destroyed during actual use, leading to failure of the electromagnetic shielding, and ensuring the conductivity and electromagnetic shielding performance of the electromagnetic shielding structure.

[0120] Any matters not described in the present invention are applicable to the prior art.

[0121] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for preparing an electromagnetic shielding structure, characterized in that: include: Step S1, placing the conductive foam rubber sheets in a foaming kettle, introducing carbon dioxide to remove the air inside the foaming kettle, controlling the pressure inside the foaming kettle to be normal, and placing the foaming kettle in an oil bath; Step S2, heating the oil bath pot, detecting the temperature of the foaming kettle, and determining the first characteristic point and the time of introducing carbon dioxide based on the comparison between the difference between the temperature of the foaming kettle and the preset ventilation temperature and the preset temperature difference; Step S3, continuously introducing carbon dioxide gas into the foaming kettle, detecting the flow rate of the introduced carbon dioxide gas and the gas pressure in the foaming kettle, and heating the oil bath pot to a preset temperature and maintaining it constant; Step S4, determining a second characteristic point and a time to reduce the flow rate of carbon dioxide based on a comparison result of the slope of the pressure curve in the foaming kettle with a preset slope; Step S5, determining a method for adjusting the flow rate of carbon dioxide based on the rate of change of the air pressure in the foaming kettle at the time corresponding to the second characteristic point, and taking the flow rate of carbon dioxide introduced when the air pressure reaches a preset pressure as a preset flow rate and maintaining it; Step S6, determining the time to stop introducing carbon dioxide based on the comparison between the difference between the air pressure in the foaming kettle and the preset air pressure and the preset air pressure difference; Step S7, opening the pressure relief valve, when the temperature in the foaming kettle drops to a preset packaging temperature, bringing the packaging layer into contact with the surface of the conductive foaming material, and after the packaging layer and the conductive foaming material are stabilized, placing the foaming kettle in an ice water bath to cool and shape, thereby obtaining a composite conductive layer; Step S8, attaching an adhesive layer to the composite conductive layer to obtain an electromagnetic shielding structure.

2. The method for preparing an electromagnetic shielding structure according to claim 1, characterized in that: In step S2, when it is detected that the difference between the temperature of the foaming kettle and the preset ventilation temperature is less than the preset temperature difference and lasts for a first time period, the point on the air pressure curve corresponding to this moment is determined as the first characteristic point.

3. The method for preparing an electromagnetic shielding structure according to claim 2, characterized in that: In the step S2, the time corresponding to the first characteristic point is determined as the time for introducing carbon dioxide.

4. The method for preparing an electromagnetic shielding structure according to claim 3, characterized in that: In step S4, when the slope of the pressure curve in the foaming kettle is less than or equal to the preset slope, the point on the pressure curve corresponding to that moment is determined as the second characteristic point, and the preset slope is determined according to the pressure change rate in the foaming kettle.

5. The method for preparing an electromagnetic shielding structure according to claim 4, characterized in that: In the step S4, the time corresponding to the second characteristic point is determined as the time for reducing the flow rate of carbon dioxide.

6. The method for preparing an electromagnetic shielding structure according to claim 5, characterized in that: In the step S5, the air pressure change rate is determined according to the air pressure change amount in the foaming kettle within a preset time period, and the adjustment method of the carbon dioxide flow rate corresponds to the air pressure change rate.

7. The method for preparing an electromagnetic shielding structure according to claim 6, characterized in that: In the step S6, when the difference between the air pressure in the foaming kettle and the preset air pressure is greater than the preset air pressure difference, this moment is determined as the moment to stop introducing carbon dioxide.

8. The method for preparing an electromagnetic shielding structure according to claim 7, characterized in that: In step S7, the curing temperature of the encapsulation layer is lower than the preset encapsulation temperature; when the temperature in the foaming kettle drops to the curing temperature, the corresponding moment is the moment when the encapsulation layer is cured and in contact with the conductive foam material.

9. An electromagnetic shielding structure prepared by the method for preparing an electromagnetic shielding structure according to any one of claims 1 to 8, characterized in that: A single electromagnetic shielding structure includes: A composite conductive layer, comprising a packaging layer and a conductive foam layer, wherein the packaging layer is connected to the conductive foam layer; The adhesive layer is connected to the composite conductive layer and is used to fix the composite conductive layer and the surface requiring electromagnetic shielding.

10. The electromagnetic shielding structure according to claim 9, characterized in that: The electromagnetic shielding structures are connected to each other through a buckle structure of the electromagnetic shielding structure, and the buckle structure includes a buckle slot portion and a buckle portion which are arranged opposite to each other.

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