Low-density composite electromagnetic shielding plate and its preparation method

Abstract

The present invention discloses a low-density composite electromagnetic shielding plate and a preparation method thereof. The low-density composite electromagnetic shielding plate and the preparation method thereof include: two composite shielding layers and an electromagnetic wave absorbing foam layer; the composite shielding layer, the electromagnetic wave absorbing foam layer, and another composite shielding layer are sequentially stacked and connected to form the low-density composite electromagnetic shielding plate of the present invention. The composite shielding layer includes a plurality of glass fiber reinforced epoxy resin insulating layers and a plurality of graphene conductive shielding layers; the plurality of glass fiber reinforced epoxy resin insulating layers and the plurality of graphene conductive shielding layers are sequentially and alternately stacked and connected, and the outer surfaces on both sides of the composite shielding layer are both glass fiber reinforced epoxy resin insulating layers. The low-density composite electromagnetic shielding plate of the present invention uses a glass fiber reinforced epoxy resin insulating layer, a graphene conductive shielding layer, and an electromagnetic wave absorbing foam layer to be stacked and connected according to a preset rule to form a low-density composite plate capable of realizing electromagnetic shielding.

Description

Technical Field

[0001] The present invention relates to the technical field of shielding materials, and particularly to a low-density composite electromagnetic shielding board and a preparation method thereof. Background Art

[0002] With the rapid development of electronic product technology, the problem of electromagnetic pollution of various electronic products has become increasingly serious. In order to reduce the impact of electromagnetic pollution on people's lives, various electromagnetic shielding materials have emerged. The most commonly used are various metal sheets and various electromagnetic shielding films made of metal grids or powders combined with polymer materials. These electromagnetic shielding materials can effectively prevent or reduce the leakage of electromagnetic signals and reduce the harm of electromagnetic radiation to the human body;

[0003] However, due to the limitations of material characteristics, these electromagnetic shielding materials have their specific uses and application environments. In some special occasions with specific requirements, electromagnetic shielding materials are required to have a certain mechanical structural strength and not contain metal materials that can be detected by radar or X-rays. Summary of the Invention

[0004] Based on this, in view of the technical problem that existing electromagnetic shielding materials cannot meet the use scenarios sensitive to metal materials, it is necessary to provide a low-density composite electromagnetic shielding board and a preparation method thereof.

[0005] A low-density composite electromagnetic shielding board includes two composite shielding layers and an electromagnetic wave absorbing foam layer; the electromagnetic wave absorbing foam layer is disposed between the two composite shielding layers, that is, the composite shielding layer, the electromagnetic wave absorbing foam layer, and the other composite shielding layer are sequentially stacked and connected to form the low-density composite electromagnetic shielding board of the present invention.

[0006] The composite shielding layer includes a plurality of glass fiber reinforced epoxy resin insulating layers and a plurality of graphene conductive shielding layers; the plurality of glass fiber reinforced epoxy resin insulating layers and the plurality of graphene conductive shielding layers are sequentially and alternately stacked and connected, and both outer surfaces of the composite shielding layer are glass fiber reinforced epoxy resin insulating layers.

[0007] In one embodiment, the raw materials of the electromagnetic wave absorbing foam layer include: 60-90 parts of polyether polyol, 10-40 parts of polyester polyol, 1.0-2.5 parts of chemical blowing agent, 10-20 parts of physical blowing agent, 1.0-2.5 parts of catalyst, 1.0-2.0 parts of foam stabilizer, 10-30 parts of conductive carbon black, and 80-150 parts of polyisocyanate.

[0008] In one embodiment, the above-mentioned polyether polyol is one or a mixture of sucrose-based rigid foam polyol 4110, sucrose-based rigid foam polyol 6110, and sucrose-based rigid foam polyol with a hydroxyl value ranging from 420 to 450.

[0009] In one embodiment, the above-mentioned polyester polyol is one or a mixture of low molecular weight polyester-based polyols with a hydroxyl value ranging from 450 to 480.

[0010] In one embodiment, the above-mentioned chemical blowing agent is water.

[0011] In one embodiment, the above-mentioned physical blowing agent is one or a mixture of 1,1-dichloro-1-fluoroethane 141B, dichloromethane MC, and cyclohexane.

[0012] In one embodiment, the above-mentioned catalyst is one or a mixture of amine catalyst A33, amine catalyst A1, rigid foam catalyst PC5, and catalyst PC8.

[0013] In one embodiment, the above-mentioned foam stabilizer is polyether-modified silicone oil.

[0014] In one embodiment, the above-mentioned conductive carbon black is one or a mixture of conductive channel black, conductive furnace black, super conductive furnace black, ultra conductive furnace black, and acetylene black.

[0015] In one embodiment, the above-mentioned polyisocyanate is polyisobiphenyl isocyanate with an NCO content of 29% - 32%.

[0016] In one embodiment, the above-mentioned glass fiber reinforced epoxy resin insulating layer includes an electronic grade alkali-free glass fiber cloth and an epoxy resin adhesive layer, wherein the epoxy resin adhesive layer wraps the surface of the electronic grade alkali-free glass fiber cloth.

[0017] In one embodiment, the above-mentioned electronic grade alkali-free glass fiber cloth is electronic grade glass fiber cloth 7628.

[0018] In one embodiment, the raw materials of the above-mentioned epoxy resin adhesive layer include: 50 - 80 parts of flame-retardant modified liquid bisphenol A epoxy resin, 20 - 50 parts of flame-retardant modified solid bisphenol A epoxy resin, 2 - 6 parts of latent curing agent, 0.01 - 0.5 parts of curing accelerator, 40 - 60 parts of organic solvent, and 50 - 100 parts of inorganic filler.

[0019] In one embodiment, the above-mentioned latent curing agent is one or a mixture of dicyandiamide, modified aliphatic amines, aromatic diamines, imidazoles, organic acid anhydrides, organic hydrazides, and Lewis acids.

[0020] In one embodiment, the above-mentioned curing accelerator is one or a mixture of several of dimethylimidazole, amines, phenols, substituted ureas, boron trifluoride complexes, metal organic salts, and phosphine compounds.

[0021] In one embodiment, the above-mentioned organic solvent is one or a mixture of several of acetone, methyl ethyl ketone, and dimethylformamide (DMF).

[0022] In one embodiment, the above-mentioned inorganic filler is one or a mixture of several of calcium carbonate, alumina, silica, aluminum hydroxide, magnesium hydroxide, and talcum powder.

[0023] In one embodiment, the above-mentioned graphene conductive shielding layer includes a glass fiber reinforced epoxy resin insulating layer and a coating layer, wherein the coating layer wraps around the outer surface of the glass fiber reinforced epoxy resin insulating layer.

[0024] In one embodiment, the raw materials of the above-mentioned coating layer include: 50 parts of conductive carbon black, 10 parts of graphene powder, 40 parts of epoxy resin, and 50 parts of diluent.

[0025] In one embodiment, the above-mentioned conductive carbon black is one or a mixture of several of conductive channel black, conductive furnace black, super conductive furnace black, special conductive furnace black, and acetylene black.

[0026] In one embodiment, the above-mentioned graphene powder is graphene produced by the redox method.

[0027] In one embodiment, the above-mentioned epoxy resin is a thermosetting liquid bisphenol A epoxy resin.

[0028] In one embodiment, the above-mentioned diluent is one or a mixture of several of butyl glycidyl ether (BGE), isophorone, and ethylene glycol monoethyl ether.

[0029] The present invention also discloses a preparation method of a low-density composite electromagnetic shielding plate, which is used to prepare the above-mentioned low-density composite electromagnetic shielding plate, and includes the following steps:

[0030] S1. Prepare a glass fiber reinforced epoxy resin insulating layer;

[0031] S2. Prepare a graphene conductive shielding layer;

[0032] S3. Prepare an electromagnetic wave absorbing foam layer;

[0033] S4. Stack a number of glass fiber reinforced epoxy resin insulating layers and a number of graphene conductive shielding layers alternately in sequence, so as to form a multi-layer composite structure with glass fiber reinforced epoxy resin insulating layers on both surfaces, and then form a sealed and insulated composite shielding layer through hot pressing and curing.

[0034] S5. Place the two composite shielding layers on the upper and lower surfaces of a predetermined mold, and inject the mixed raw material of the electromagnetic wave absorbing foam layer into the mold. The composite shielding layers on both sides and the electromagnetic wave absorbing foam layer between them are cooled and shaped in the mold to form a low-density composite electromagnetic shielding plate.

[0035] S6. Cut and trim the cooled and shaped low-density composite electromagnetic shielding plate to obtain the finished product of the low-density composite electromagnetic shielding plate.

[0036] In one embodiment, the above step S1 includes: an operator evenly coats an epoxy resin glue layer on the surface of an electronic-grade alkali-free glass fiber cloth through a sizing machine, and dries it to form a glass fiber reinforced epoxy resin insulating layer. Specifically, in this embodiment, the sizing machine adopts a vertical sizing machine or a horizontal sizing machine, the coating speed of the sizing machine is set to 18 - 20 m / min; the drying temperature of the epoxy resin glue layer is set to 180 - 210 °C; the thickness of the glass fiber reinforced epoxy resin insulating layer is 0.10 - 0.25 mm; the resin content in the epoxy resin glue layer is 30 - 40% by weight; at 170 °C, the gel time of the epoxy resin glue layer is 120 - 150 s; the fluidity of the epoxy resin glue layer is 18 - 22%.

[0037] In one embodiment, the above step S2 includes: an operator respectively takes conductive carbon black, graphene powder, epoxy resin and a diluent and mixes them into a slurry according to the ratio of 50:10:40:50. The slurry is repeatedly ground evenly by a three-roll grinder to make a graphene conductive slurry, and then the graphene conductive slurry is evenly printed on the surface of the glass fiber reinforced epoxy resin insulating layer through a screen printing process, and then dried and cured in a hot air oven at 150 - 180 °C for 3 - 5 min to form a graphene conductive shielding layer. Specifically, the thickness of the graphene conductive shielding layer is 0.15 - 0.30 mm.

[0038] In one embodiment, step S3 described above includes: an operator respectively takes polyether polyol, polyester polyol, water, foaming agent, catalyst, foam stabilizer, and conductive carbon black according to a preset component ratio, stirs and mixes them evenly, and places them in the polyol storage tank of a rigid polyurethane foam foaming machine; then takes polyisocyanate and places it in the isocyanate storage tank of the rigid polyurethane foam foaming machine; finally, sets the flow rates of the polyol storage tank and the isocyanate storage tank to a weight ratio of 1:1, and after the raw materials of the electromagnetic wave absorbing foam layer components are stirred and mixed evenly by the mixing head of the rigid polyurethane foam foaming machine, immediately injects them into a mold for cross-linking and curing reaction, and then cools and shapes to form an electromagnetic wave absorbing foam layer.

[0039] In one embodiment, when performing hot pressing and curing in step S4 above, the pressure is set to 20 - 35 kg / cm 2 , the temperature is set to 150 - 180 °C, and the hot pressing and curing time is set to 80 - 120 min. In actual production, before performing hot pressing and curing and shaping, an operator respectively lays a BOPP release film on one side surface of the two opposite hot pressing steel plates, and a number of glass fiber reinforced epoxy resin insulating layers and a number of graphene conductive shielding layers are alternately stacked in sequence between the two BOPP release films for hot pressing processing; when the hot pressing and curing is completed, the operator sequentially removes the corresponding two hot pressing steel plates and the two BOPP release films on both sides, and finally obtains a composite shielding layer.

[0040] In summary, the low-density composite electromagnetic shielding plate disclosed in the present invention uses a glass fiber reinforced epoxy resin insulating layer, a graphene conductive shielding layer, and an electromagnetic wave absorbing foam layer to be stacked and connected in a preset rule to form a low-density composite plate capable of realizing electromagnetic shielding. Among them, the glass fiber reinforced epoxy resin insulating layer has the characteristics of low density, high structural strength, and excellent insulation performance, and the graphene conductive shielding layer and the electromagnetic wave absorbing foam layer can provide effective electromagnetic shielding performance. Compared with the existing electromagnetic shielding films made of metal sheets, metal grids or powders, and polymer materials, the low-density composite electromagnetic shielding plate of the present invention can effectively prevent and reduce the leakage of electromagnetic signals, thereby effectively reducing the harm of electromagnetic radiation to the human body. At the same time, it can also adapt to some usage environments sensitive to metal materials, that is, the low-density composite electromagnetic shielding plate of the present invention has a wider application scenario. Detailed Description of the Invention

[0041] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following provides a detailed description of the specific embodiments of the present invention. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0042] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown below. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0043] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0044] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0046] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0047] The present invention discloses a low-density composite electromagnetic shielding plate, which comprises two composite shielding layers and an electromagnetic wave absorbing foam layer; wherein, the electromagnetic wave absorbing foam layer is disposed between the two composite shielding layers, that is, the composite shielding layer, the electromagnetic wave absorbing foam layer and the other composite shielding layer are sequentially stacked and connected to form the low-density composite electromagnetic shielding plate of the present invention.

[0048] Furthermore, the composite shielding layer comprises a plurality of glass fiber reinforced epoxy resin insulating layers and a plurality of graphene conductive shielding layers; wherein, the plurality of glass fiber reinforced epoxy resin insulating layers and the plurality of graphene conductive shielding layers are sequentially stacked and connected alternately, and the outer surfaces on both sides of the composite shielding layer are both glass fiber reinforced epoxy resin insulating layers. Specifically, the electromagnetic wave absorbing foam layer is disposed between the two corresponding glass fiber reinforced epoxy resin insulating layers on the surfaces of the two composite shielding layers and is sequentially stacked and connected, thereby forming the low-density composite electromagnetic shielding plate of the present invention. The glass fiber reinforced epoxy resin insulating layer has the characteristics of low density, high structural strength and excellent insulation performance, and the graphene conductive shielding layer and the electromagnetic wave absorbing foam layer can provide effective electromagnetic shielding performance.

[0049] Furthermore, the raw materials of the electromagnetic wave absorbing foam layer include: 60-90 parts of polyether polyol, 10-40 parts of polyester polyol, 1.0-2.5 parts of chemical blowing agent, 10-20 parts of physical blowing agent, 1.0-2.5 parts of catalyst, 1.0-2.0 parts of foam stabilizer, 10-30 parts of conductive carbon black and 80-150 parts of polyisocyanate.

[0050] Specifically, the polyether polyol is one or a mixture of sucrose-based rigid foam polyol 4110, sucrose-based rigid foam polyol 6110 and sucrose-based rigid foam polyol with a hydroxyl value in the range of 420-450.

[0051] Specifically, the polyester polyol is one or a mixture of low molecular weight polyester-based polyols with a hydroxyl value in the range of 450-480.

[0052] Specifically, the chemical blowing agent is water.

[0053] Specifically, the physical blowing agent is one or a mixture of several of 1,1-dichloro-1-fluoroethane 141B, methylene chloride MC, and cyclohexane.

[0054] Specifically, the catalyst is one or a mixture of several of amine catalyst A33, amine catalyst A1, rigid foam catalyst PC5, and catalyst PC8.

[0055] Specifically, the foam stabilizer is polyether-modified silicone oil.

[0056] Specifically, the conductive carbon black is one or a mixture of several of conductive channel black, conductive furnace black, super-conductive furnace black, ultra-conductive furnace black, and acetylene black.

[0057] Specifically, the polyisocyanate is polyisobiphenyl isocyanate, and its NCO content is 29% - 32%.

[0058] Further, the glass fiber-reinforced epoxy resin insulating layer includes an electronic-grade alkali-free glass fiber cloth and an epoxy resin adhesive layer, wherein the epoxy resin adhesive layer is wrapped on the surface of the electronic-grade alkali-free glass fiber cloth.

[0059] Specifically, in this embodiment, the electronic-grade alkali-free glass fiber cloth is electronic-grade glass fiber cloth 7628.

[0060] Further, the raw materials of the epoxy resin adhesive layer include: 50 - 80 parts of flame-retardant modified liquid bisphenol A epoxy resin, 20 - 50 parts of flame-retardant modified solid bisphenol A epoxy resin, 2 - 6 parts of latent curing agent, 0.01 - 0.5 parts of curing accelerator, 40 - 60 parts of organic solvent, and 50 - 100 parts of inorganic filler.

[0061] Specifically, the latent curing agent is one or a mixture of several of dicyandiamide, modified aliphatic amines, aromatic diamines, imidazoles, organic acid anhydrides, organic hydrazides, and Lewis acids.

[0062] Specifically, the curing accelerator is one or a mixture of several of dimethylimidazole, amines, phenols, substituted ureas, boron trifluoride complexes, metal organic salts, and phosphine compounds.

[0063] Specifically, the organic solvent is one or a mixture of several of acetone, methyl ethyl ketone, and dimethylformamide DMF.

[0064] Specifically, the inorganic filler is one or a mixture of several of calcium carbonate, alumina, silica, aluminum hydroxide, magnesium hydroxide, and talc powder.

[0065] Further, the graphene conductive shielding layer includes a glass fiber-reinforced epoxy resin insulating layer and a coating layer, wherein the coating layer is wrapped on the outer surface of the glass fiber-reinforced epoxy resin insulating layer.

[0066] Furthermore, the raw materials of the coating layer include: 50 parts of conductive carbon black, 10 parts of graphene powder, 40 parts of epoxy resin, and 50 parts of diluent.

[0067] Specifically, the conductive carbon black is one or a mixture of several of conductive channel black, conductive furnace black, super conductive furnace black, extra conductive furnace black, and acetylene black.

[0068] Specifically, the graphene powder is graphene produced by the redox method.

[0069] Specifically, the epoxy resin is a thermosetting liquid bisphenol A epoxy resin.

[0070] Specifically, the diluent is one or a mixture of several of butyl glycidyl ether BGE, isophorone, and ethylene glycol monoethyl ether.

[0071] The present invention also discloses a preparation method of a low-density composite electromagnetic shielding plate, which is used to prepare the above-mentioned low-density composite electromagnetic shielding plate, and includes the following steps:

[0072] S1. Prepare a glass fiber-reinforced epoxy resin insulating layer;

[0073] S2. Prepare a graphene conductive shielding layer;

[0074] S3. Prepare an electromagnetic wave absorption foam layer;

[0075] S4. Stack a number of glass fiber-reinforced epoxy resin insulating layers and a number of graphene conductive shielding layers alternately in sequence to form a multi-layer composite structure with glass fiber-reinforced epoxy resin insulating layers on both surfaces, and then form a composite shielding layer through hot pressing and curing;

[0076] S5. Place the two composite shielding layers on the upper and lower surfaces of a predetermined mold, and inject the mixed raw materials of the electromagnetic wave absorption foam layer into the mold. The composite shielding layers on both sides and the electromagnetic wave absorption foam layer between them are cooled and shaped in the mold to form a low-density composite electromagnetic shielding plate;

[0077] S6. Cut and trim the cooled and shaped low-density composite electromagnetic shielding plate to obtain the finished low-density composite electromagnetic shielding plate.

[0078] Further, step S1 includes: an operator evenly coats an epoxy resin liquid layer on the surface of an electronic-grade alkali-free glass fiber cloth through a sizing machine, and dries it to form a glass fiber-reinforced epoxy resin insulating layer. Specifically, in this embodiment, the sizing machine is a vertical sizing machine or a horizontal sizing machine, the coating speed of the sizing machine is set to 18 - 20 m / min; the drying temperature of the epoxy resin liquid layer is set to 180 - 210 °C; the thickness of the glass fiber-reinforced epoxy resin insulating layer is 0.10 - 0.25 mm; the resin content in the epoxy resin liquid layer is 30 - 40% by weight; at 170 °C, the gel time of the epoxy resin liquid layer is 120 - 150 s; the fluidity of the epoxy resin liquid layer is 18 - 22%.

[0079] Further, step S2 includes: an operator respectively takes carbon black, graphene powder, epoxy resin, and a diluent and mixes them into a slurry according to a ratio of 50:10:40:50. The slurry is repeatedly ground evenly by a three-roll grinder to make a graphene conductive slurry, and then the graphene conductive slurry is evenly printed on the surface of the glass fiber-reinforced epoxy resin insulating layer through a screen printing process, and then dried and cured in a hot air oven at 150 - 180 °C for 3 - 5 min to form a prepared graphene conductive shielding layer. Specifically, the thickness of the graphene conductive shielding layer is 0.15 - 0.30 mm.

[0080] Further, step S3 includes: an operator respectively takes polyether polyol, polyester polyol, water, a foaming agent, a catalyst, a foam stabilizer, and carbon black according to a preset component ratio, stirs and mixes them evenly, and places them in the polyol storage tank of a rigid polyurethane foam foaming machine; then takes polyisocyanate and places it in the isocyanate storage tank of the rigid polyurethane foam foaming machine; finally, sets the flow rates of the polyol storage tank and the isocyanate storage tank to a weight ratio of 1:1, and immediately injects the raw materials of the electromagnetic wave absorbing foam layer component into the mold through the mixing head of the rigid polyurethane foam foaming machine after high-speed stirring and mixing, and then cools and shapes to form an electromagnetic wave absorbing foam layer.

[0081] Further, when performing hot pressing and curing in step S4, the pressure is set to 20 - 35 kg / cm 2 , the temperature is set to 150 - 180 °C, and the hot pressing and curing time is set to 80 - 120 min. In actual production, before performing hot pressing and curing and shaping, an operator respectively lays a side of BOPP release film on the opposite surfaces of two hot pressing steel plates, and a plurality of glass fiber-reinforced epoxy resin insulating layers and a plurality of graphene conductive shielding layers are alternately stacked in sequence between the two BOPP release films for hot pressing processing; when the hot pressing and curing is completed, the operator sequentially removes the corresponding two hot pressing steel plates and the two sides of the BOPP release film, and finally obtains a composite shielding layer.

[0082] Example 1

[0083] Based on the above-mentioned low-density composite electromagnetic shielding plate and its preparation method:

[0084] In this embodiment, the raw materials of the electromagnetic wave absorption foam layer include: 80 parts of polyether polyol, 20 parts of polyester polyol, 1.5 parts of water, 15 parts of physical foaming agent, 1.8 parts of catalyst, 1.2 parts of foam stabilizer, 20 parts of conductive carbon black, and 80 - 150 parts of polyisocyanate.

[0085] In this embodiment, the raw materials of the epoxy resin adhesive layer include: 80 parts of flame-retardant modified liquid bisphenol A epoxy resin, 20 parts of flame-retardant modified solid bisphenol A epoxy resin, 3 parts of latent curing agent, 0.12 parts of curing accelerator dimethylimidazole, 50 parts of organic solvent, and 50 parts of inorganic filler aluminum hydroxide.

[0086] In this embodiment, the raw materials of the coating layer include: 50 parts of conductive carbon black, 10 parts of graphene powder, 40 parts of epoxy resin, and 50 parts of diluent.

[0087] In this embodiment, step S1 includes: under continuous stirring conditions, the operator mixes the components of the epoxy resin adhesive layer in this embodiment evenly in a batching tank, and uses a horizontal continuous gluing machine to evenly coat the epoxy resin adhesive layer on the surface of the electronic-grade non-alkali glass fiber cloth 7628, and then dries it to form a glass fiber-reinforced epoxy resin insulating layer. Specifically, in this embodiment, the coating speed of the horizontal continuous gluing machine is set to 18 m / min; the drying temperature of the epoxy resin adhesive layer is set to 180 - 210 °C; the thickness of the glass fiber-reinforced epoxy resin insulating layer is 0.22 mm; the resin content in the epoxy resin adhesive layer is 36% by weight; at 170 °C, the gel time of the epoxy resin adhesive layer is 135 s; the fluidity of the epoxy resin adhesive layer is 18%.

[0088] In this embodiment, step S2 includes: the operator respectively takes conductive carbon black, graphene powder, epoxy resin, and diluent and mixes them into a slurry according to the ratio of 50:10:40:50, and the slurry is repeatedly ground evenly by a three-roll mill to make graphene conductive slurry, and then the graphene conductive slurry is evenly printed on the surface of the glass fiber-reinforced epoxy resin insulating layer through a screen printing process, and then dried and cured in a hot air oven at 150 - 180 °C for 3 - 5 min to form a graphene conductive shielding layer. Specifically, the thickness of the graphene conductive shielding layer is 0.28 mm.

[0089] In this embodiment, step S3 includes: The operator respectively takes 80 parts of polyether polyol, 20 parts of polyester polyol, 1.5 parts of water, 15 parts of foaming agent, 1.8 parts of catalyst, 1.2 parts of foam stabilizer, and 20 parts of conductive carbon black according to the component ratio in this embodiment, stirs and mixes them evenly, and places them in the polyol storage tank of the rigid polyurethane foam foaming machine; then takes polyisocyanate and places it in the isocyanate storage tank of the rigid polyurethane foam foaming machine; finally, sets the flow rates of the polyol storage tank and the isocyanate storage tank to a weight ratio of 1:1, and after the raw materials of the electromagnetic wave absorption foam layer components are stirred and mixed evenly by the mixing head of the rigid polyurethane foam foaming machine, immediately injects them into the mold for cross-linking and curing reaction. At this time, the volume of the mixed raw materials of the electromagnetic wave absorption foam layer expands to 20 - 30 times, and then cools and shapes to form the electromagnetic wave absorption foam layer.

[0090] In this embodiment, when performing hot pressing and curing in step S4, the pressure is set to 30 kg / cm 2 , the temperature is set to 170 °C, the hot pressing and curing time is set to 110 min, and the preset target thickness of the composite shielding layer is 2.0 mm.

[0091] Based on the low-density composite electromagnetic shielding board and its preparation method of the present invention, combined with the ratio of the glass fiber-reinforced epoxy resin insulating layer, graphene conductive shielding layer, and electromagnetic wave absorption foam layer in this embodiment and the process conditions of step S1, step S2, step S3, and step S4 in this embodiment, a finished product of the low-density composite electromagnetic shielding board is obtained in actual production. The performance parameters of the low-density composite electromagnetic shielding board are shown in Table 1.

[0092] Table 1: Performance parameters of the low-density composite electromagnetic shielding board in Example 1

[0093]

[0094] Example 2

[0095] Based on the above low-density composite electromagnetic shielding board and its preparation method:

[0096] In this embodiment, the raw materials of the electromagnetic wave absorption foam layer include: 70 parts of polyether polyol, 30 parts of polyester polyol, 1.5 parts of water, 15 parts of physical foaming agent, 1.8 parts of catalyst, 1.2 parts of foam stabilizer, 20 parts of conductive carbon black, and 80 - 150 parts of polyisocyanate.

[0097] In this embodiment, the raw materials of the epoxy resin adhesive layer include: 70 parts of flame-retardant modified liquid bisphenol A epoxy resin, 30 parts of flame-retardant modified solid bisphenol A epoxy resin, 3.2 parts of latent curing agent, 0.15 part of curing accelerator dimethylimidazole, 50 parts of organic solvent, and 30 parts of inorganic filler aluminum hydroxide.

[0098] In this embodiment, the raw materials of the coating layer include: 50 parts of conductive carbon black, 10 parts of graphene powder, 40 parts of epoxy resin, and 50 parts of diluent.

[0099] In this embodiment, step S1 includes: under continuous stirring conditions, the operator mixes the components of the epoxy resin adhesive layer in this embodiment evenly in a batching tank, and uses a horizontal continuous gluing machine to evenly coat the epoxy resin adhesive layer on the surface of the electronic-grade alkali-free glass fiber cloth 7628, and then dries it to form a glass fiber-reinforced epoxy resin insulation layer. Specifically, in this embodiment, the coating speed of the horizontal continuous gluing machine is set to 20 m / min; the drying temperature of the epoxy resin adhesive layer is set to 180 - 200 °C; the thickness of the glass fiber-reinforced epoxy resin insulation layer is 0.21 mm; the resin content in the epoxy resin adhesive layer is 38% by weight; at 170 °C, the gel time of the epoxy resin adhesive layer is 125 s; the fluidity of the epoxy resin adhesive layer is 15%.

[0100] In this embodiment, step S2 includes: the operator respectively takes conductive carbon black, graphene powder, epoxy resin, and diluent and mixes them into a slurry according to the ratio of 50:10:40:50. The slurry is repeatedly ground evenly by a three-roll grinder to make a graphene conductive slurry, and then the graphene conductive slurry is evenly printed on the surface of the glass fiber-reinforced epoxy resin insulation layer through a screen printing process, and then dried and cured in a hot air oven at 150 - 180 °C for 3 - 5 min to form a graphene conductive shielding layer. Specifically, the thickness of the graphene conductive shielding layer is 0.26 mm.

[0101] In this embodiment, step S3 includes: the operator respectively takes 70 parts of polyether polyol, 30 parts of polyester polyol, 1.5 parts of water, 15 parts of foaming agent, 1.8 parts of catalyst, 1.2 parts of foam stabilizer, and 20 parts of conductive carbon black according to the component ratio in this embodiment, stirs and mixes them evenly, and places them in the polyol storage tank of a polyurethane rigid foam foaming machine; then takes polyisocyanate and places it in the isocyanate storage tank of the polyurethane rigid foam foaming machine; finally, sets the flow rates of the polyol storage tank and the isocyanate storage tank to a weight ratio of 1:1, and high-speed stirs and mixes the raw materials of the electromagnetic wave absorption foam layer components evenly through the mixing head of the polyurethane rigid foam foaming machine, and immediately injects them into a mold for cross-linking and curing reaction. At this time, the volume of the mixed raw materials of the electromagnetic wave absorption foam layer expands to 20 - 30 times, and then cools and shapes to form an electromagnetic wave absorption foam layer.

[0102] In this embodiment, in step S4, a number of glass fiber-reinforced epoxy resin insulation layers and a number of graphene conductive shielding layers are alternately stacked in sequence to form a 9-layer composite structure with glass fiber-reinforced epoxy resin insulation layers on both surfaces; when performing hot pressing and curing, the pressure is set to 30 kg / cm2 The temperature is set at 170 °C, the hot pressing and curing time is set at 110 min, and the preset target thickness of the composite shielding layer is 2.0 mm.

[0103] Based on the low-density composite electromagnetic shielding board and its preparation method of the present invention, combined with the ratio of the glass fiber reinforced epoxy resin insulating layer, the graphene conductive shielding layer and the electromagnetic wave absorbing foam layer in this embodiment and the process conditions of step S1, step S2, step S3 and step S4 in this embodiment, a finished low-density composite electromagnetic shielding board is obtained in actual production. The performance parameters of the low-density composite electromagnetic shielding board are shown in Table 2.

[0104] Table 2: Performance parameters of the low-density composite electromagnetic shielding board in Example 2

[0105]

[0106] In summary, the low-density composite electromagnetic shielding board disclosed by the present invention uses a glass fiber reinforced epoxy resin insulating layer, a graphene conductive shielding layer and an electromagnetic wave absorbing foam layer to be stacked and connected in a preset rule to form a low-density composite board capable of realizing electromagnetic shielding. Among them, the glass fiber reinforced epoxy resin insulating layer has the characteristics of low density, high structural strength and excellent insulation performance, and the graphene conductive shielding layer and the electromagnetic wave absorbing foam layer can provide effective electromagnetic shielding performance. Compared with the existing electromagnetic shielding films made of metal sheets, metal grids or powders and polymer materials, the low-density composite electromagnetic shielding board of the present invention can effectively prevent and reduce the leakage of electromagnetic signals, thereby effectively reducing the harm of electromagnetic radiation to the human body. At the same time, it can also adapt to some use environments sensitive to metal materials, that is, the low-density composite electromagnetic shielding board of the present invention has a wider application scenario.

[0107] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0108] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A low-density composite electromagnetic shielding plate, characterized in that, Including: Two composite shielding layers and an electromagnetic wave absorbing foam layer; The electromagnetic wave absorbing foam layer is disposed between the two composite shielding layers, that is, the composite shielding layer, the electromagnetic wave absorbing foam layer, and the other composite shielding layer are sequentially stacked and connected to form the low-density composite electromagnetic shielding plate; The composite shielding layer includes a plurality of glass fiber reinforced epoxy resin insulating layers and a plurality of graphene conductive shielding layers; the plurality of glass fiber reinforced epoxy resin insulating layers and the plurality of graphene conductive shielding layers are sequentially stacked and connected alternately, and both outer surfaces of the composite shielding layer are the glass fiber reinforced epoxy resin insulating layers; The raw materials of the electromagnetic wave absorbing foam layer include: 60-90 parts of polyether polyol, 10-40 parts of polyester polyol, 1.0-2.5 parts of chemical blowing agent, 10-20 parts of physical blowing agent, 1.0-2.5 parts of catalyst, 1.0-2.0 parts of foam stabilizer, 10-30 parts of conductive carbon black, and 80-150 parts of polyisocyanate; The glass fiber reinforced epoxy resin insulating layer includes an electronic grade alkali-free glass fiber cloth and an epoxy resin adhesive layer, and the epoxy resin adhesive layer wraps the surface of the electronic grade alkali-free glass fiber cloth; The raw materials of the epoxy resin adhesive layer include: 50-80 parts of flame retardant modified liquid bisphenol A epoxy resin, 20-50 parts of flame retardant modified solid bisphenol A epoxy resin, 2-6 parts of latent curing agent, 0.01-0.5 parts of curing accelerator, 40-60 parts of organic solvent, and 50-100 parts of inorganic filler; The graphene conductive shielding layer includes a glass fiber reinforced epoxy resin insulating layer and a coating layer, and the coating layer wraps the outer surface of the glass fiber reinforced epoxy resin insulating layer; The raw materials of the coating layer include: 50 parts of conductive carbon black, 10 parts of graphene powder, 40 parts of epoxy resin, and 50 parts of diluent.

2. A method for preparing the low-density composite electromagnetic shielding plate according to claim 1, characterized in that, It includes the following steps: S1. Prepare the glass fiber reinforced epoxy resin insulating layer; S2. Prepare the graphene conductive shielding layer; S3. Prepare the electromagnetic wave absorbing foam layer; S4. Stack a plurality of the glass fiber reinforced epoxy resin insulating layers and a plurality of the graphene conductive shielding layers alternately in sequence to form a multi-layer composite structure with both side surfaces being the glass fiber reinforced epoxy resin insulating layers, and then form the composite shielding layer through hot pressing and curing; S5. Dispose the two composite shielding layers on the upper and lower surfaces of a predetermined mold, and inject the mixed raw materials of the electromagnetic wave absorbing foam layer into the mold. The two composite shielding layers on both sides and the electromagnetic wave absorbing foam layer therebetween are cooled and shaped in the mold to form the low-density composite electromagnetic shielding plate; S6. Cut and trim the cooled and shaped low-density composite electromagnetic shielding plate to obtain the finished product of the low-density composite electromagnetic shielding plate.

3. The preparation method of the low-density composite electromagnetic shielding plate according to claim 2, characterized in that, The step S1 includes: an operator evenly coats the surface of the electronic-grade alkali-free glass fiber cloth with the epoxy resin glue solution layer through a sizing machine, and dries it to form the glass fiber reinforced epoxy resin insulating layer; the coating speed of the sizing machine is set to 18 - 20 m / min; the drying temperature of the epoxy resin glue solution layer is set to 180 - 210 °C; the thickness of the glass fiber reinforced epoxy resin insulating layer is 0.10 - 0.25 mm; the resin content in the epoxy resin glue solution layer is 30 - 40% by weight; at 170 °C, the gel time of the epoxy resin glue solution layer is 120 - 150 s; the fluidity of the epoxy resin glue solution layer is 18 - 22%.

4. The preparation method of the low-density composite electromagnetic shielding plate according to claim 2, characterized in that, The step S2 includes: an operator respectively takes the conductive carbon black, the graphene powder, the epoxy resin, and the diluent and mixes them into a slurry according to the ratio of 50:10:40:

50. The slurry is repeatedly ground evenly by a three-roll grinder to make the graphene conductive slurry. Then, the graphene conductive slurry is evenly printed on the surface of the glass fiber reinforced epoxy resin insulating layer through a screen printing process, and then dried and cured in a hot air oven at 150 - 180 °C for 3 - 5 min to form the graphene conductive shielding layer, and the thickness of the graphene conductive shielding layer is 0.15 - 0.30 mm.

5. The preparation method of the low-density composite electromagnetic shielding plate according to claim 2, characterized in that, The step S3 includes: an operator respectively takes the polyether polyol, the polyester polyol, water, the foaming agent, the catalyst, the foam stabilizer, and the conductive carbon black according to a preset component ratio, stirs and mixes them evenly, and places them in the polyol storage tank of a rigid polyurethane foam foaming machine; then takes the polyisocyanate and places it in the isocyanate storage tank of the rigid polyurethane foam foaming machine; finally, sets the flow rates of the polyol storage tank and the isocyanate storage tank to a weight ratio of 1:1, and after the raw materials of the electromagnetic wave absorbing foam layer components are highly stirred and mixed evenly through the mixing head of the rigid polyurethane foam foaming machine, immediately injects them into a mold for cross-linking and curing reaction, and then cools and shapes to form the electromagnetic wave absorbing foam layer.

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