Electromagnetic shielding powder coating and preparation method thereof

Abstract

The invention discloses an electromagnetic shielding powder coating and a preparation method thereof, and belongs to the technical field of electromagnetic shielding coatings, and the electromagnetic shielding powder coating comprises the following raw materials in parts by weight: nano silicon dioxide, nano ferrite, nano aluminum nitride, nano ferrite, an activated carbonized material, modified graphite powder, epoxy resin, a curing agent, tinned copper powder and heat-conducting particles. The preparation method comprises the following steps: preparing a mixed filler from the nano silicon dioxide, the nano ferrite and the nano aluminum nitride; uniformly mixing the mixed filler with the activated carbonized material, modified graphite powder, epoxy resin and a curing agent to obtain a mixture; performing melt extrusion to obtain slices, and performing crushing and grinding treatment on the slices to obtain modified epoxy resin powder; and finally, uniformly mixing with the tinned copper powder and the heat-conducting particles to obtain the magnetic shielding powder coating. The electromagnetic shielding coating has excellent electromagnetic shielding performance and good heat conduction and heat dissipation effects, and can prevent the application of the coating from influencing the heat dissipation of equipment.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of electromagnetic shielding coatings, and specifically relates to an electromagnetic shielding powder coating and a preparation method thereof. Background Art

[0002] Electromagnetic shielding coatings generally contain composite particle fillers such as copper, silver, and activated carbon. They can shield electromagnetic interference by spraying or brushing. Their characteristics are that they form metal-like properties of absorbing, conducting, and attenuating electromagnetic waves on the surface of insulating non-metallic or non-conductive equipment through conductive materials, thus achieving the effect of electromagnetic shielding.

[0003] At present, the electromagnetic shielding performance of electromagnetic shielding powder coatings has been developed to a relatively mature level. For example, the patent with the authorization announcement number CN 114106670 B discloses an electromagnetic shielding powder coating and its preparation method. After the absorber is coated with silicon dioxide, it is chemically modified with a coupling agent, and the coupling agent is added to the graphene resin at the same time, so that the absorber, filler silicon dioxide, etc. are well compatible with the polyester resin matrix, and the dispersion effect of the absorber and filler in the coating is significantly improved. The patent with the authorization announcement number CN 114058258 B discloses an electromagnetic shielding coating suitable for heat shrinkable materials and its preparation method. The low melting point alloy is melted during the heating and shrinking process of the heat shrinkable material to promote the conductive filler to form a conductive network. The shielding performance of the shielding coating is increased through the heat shrinking process and the wrinkling and cracking caused by the addition of too much rigid metal filler is avoided, and finally the low addition and high shielding characteristics of the coating are achieved.

[0004] However, since electromagnetic shielding coating is the simplest treatment method for electromagnetic shielding of non-metallic shells of mobile phones, monitors, printers and various instruments, it is inevitable that the power equipment will generate heat during operation, and the electromagnetic shielding coating applied on the shell surface will affect the heat dissipation of the power equipment. Therefore, it is necessary to develop electromagnetic shielding coatings that can avoid affecting the heat dissipation of equipment. Summary of the invention

[0005] The technical solution of the present invention aims at the technical problem that the existing technical solutions are too single, and provides a solution that is significantly different from the existing technology. It mainly provides an electromagnetic shielding powder coating and a preparation method thereof, which is used to solve the technical problem raised in the above background technology that the existing electromagnetic shielding coating will affect the heat dissipation of the power equipment to which it is applied.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] An electromagnetic shielding powder coating comprises the following raw materials in parts by weight:

[0008] 2-4 parts of nano silicon dioxide;

[0009] 2-3 parts of nano ferrite;

[0010] 1-2 parts of nano aluminum nitride;

[0011] 3-6 parts of activated carbonized material;

[0012] 7-12 parts of modified graphite powder;

[0013] Epoxy resin 58-74 parts;

[0014] 3-6 parts of curing agent;

[0015] 5-8 parts of tinned copper powder;

[0016] 3-5 parts of thermal conductive particles.

[0017] Specifically, the thermally conductive particles are any one of aluminum oxide and silicon carbide or a combination of both.

[0018] Furthermore, the thermally conductive particles are spherical in shape.

[0019] Furthermore, the shape of the thermally conductive particles is a regular triangular pyramid structure, and the preparation method thereof is: introducing the thermally conductive particle material gel into a plurality of forming holes of a mold plate, the forming holes on the mold plate are regular triangular pyramids, performing heat treatment, and obtaining thermally conductive particles with a regular triangular pyramid structure after demolding.

[0020] Specifically, the particle size of the thermally conductive particles is 0.1-0.5 mm.

[0021] The present invention also provides a method for preparing the electromagnetic shielding powder coating, comprising the following steps:

[0022] S1. Evenly disperse nano-silicon dioxide, nano-ferrite and nano-aluminum nitride in an ethanol solution, add a coupling agent, stir evenly, let stand for 5-8 hours, filter, wash with water, and dry to constant weight to obtain a mixed filler;

[0023] S2, adding the mixed filler obtained in step S1, the activated carbonized material, the modified graphite powder, the epoxy resin, and the curing agent into a mixer and stirring them to obtain a mixed material;

[0024] S3, melt-extrude the mixture obtained in step S2 to obtain slices, and then crush and grind the slices to obtain modified epoxy resin powder;

[0025] S4, adding the modified epoxy resin powder obtained in step S3, the tinned copper powder and the thermal conductive particles into a mixer and stirring them evenly to obtain the desired magnetic shielding powder coating.

[0026] Specifically, in step S1, during stirring, the temperature is adjusted to 40-45° C., and the mixture is kept warm and stirred for 1-1.5 hours.

[0027] Specifically, in step S2, the stirring speed of the stirrer is 200 r / min, and the stirring temperature is 50-55°C.

[0028] Specifically, in step S3, a twin-screw extruder is used for melt extrusion, and the temperature in the twin-screw extruder is controlled at 115-120°C.

[0029] Specifically, in step S4, the stirring speed of the stirrer is 150 r / min.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) Thermally conductive particles and nano-aluminum nitride are added to the magnetic shielding powder coating provided by the present invention, and in the preparation process, nano-aluminum nitride is fused into the modified epoxy resin powder, and the thermally conductive particles are finally added and mixed to obtain the powder coating, which can maintain the structure and specifications of the thermally conductive particles. During coating application, the thermally conductive particles remain attached to the surface of the equipment in their original state, and their particle size is consistent with the coating thickness of the electromagnetic shielding material, that is, they can contact the surface of the equipment and extend to the coating surface, thereby facilitating heat dissipation. The thermal conductive and heat dissipation effects can be promoted. The present invention not only has the electromagnetic shielding function, but also has a good thermal conductive and heat dissipation effect, which can avoid the application of the coating affecting the heat dissipation of the equipment.

[0032] (2) In the optimized solution of the present invention, the thermally conductive particles are made into a regular triangular pyramid structure, so that a portion of the thermally conductive particles can be attached to the surface of the device at a variety of angles to improve the thermal conductivity effect.

[0033] (3) Nano ferrite and tinned copper powder are added to the magnetic shielding powder coating provided by the present invention, wherein copper is a high-conductivity material and has a good shielding effect on high-frequency electromagnetic interference; ferrite is a high-permeability material and has a good shielding effect on low-frequency electromagnetic interference. Combining the two, the magnetic shielding powder coating of the present invention can shield both high-frequency electromagnetic and low-frequency electromagnetic interference.

[0034] (4) Tinned copper powder is added to the magnetic shielding powder coating provided by the present invention, and during production and preparation, the tinned copper powder is finally mixed with modified epoxy resin powder and thermal conductive particles to obtain the powder coating. The structure of the tinned copper powder is not destroyed. When used, the tin layer on the surface of the copper particles is easier to melt during the heating and curing process, which facilitates the formation of connections between different copper particles, thereby facilitating the formation of a conductive network system, which can provide better electromagnetic shielding performance.

[0035] (5) The present invention imparts reactivity and adhesion to the epoxy resin molecules through the hydroxyl groups on the epoxy resin molecules, and can strengthen the coating skeleton through the activation of carbonized materials, modified graphite powder, and mixed fillers, thereby improving the heat resistance and toughness of the coating. The present invention uses epoxy resin as the coating matrix polymer, which can form chemical bonds with the surfaces of various materials and thus has excellent adhesion. In combination with the joint action of other components, the bonding strength between the prepared coating and the substrate is greatly increased, thereby increasing the service life of the coating formed by the powder coating.

[0036] The present invention will be explained in detail below with reference to specific embodiments. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present invention, the present invention will be described in more detail below. However, the present invention can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the content disclosed in the present invention more thorough and comprehensive.

[0038] Embodiment 1: A method for preparing an electromagnetic shielding powder coating comprises the following steps:

[0039] S1. Weigh the raw materials: 2g of nano silicon dioxide; 2g of nano ferrite; 1g of nano aluminum nitride; 3g of activated carbonized material; 7g of modified graphite powder; 74g of epoxy resin; 3g of curing agent; 5g of tinned copper powder; 3g of thermal conductive particles; 15g of ethanol solution (mass fraction is 65%); 0.2g of coupling agent; the curing agent is sebacic acid dihydrazide, and the coupling agent is titanate coupling agent;

[0040] The thermally conductive particles are made of aluminum oxide, are spherical particles, and have a particle size of 0.3 mm.

[0041] S2. Evenly disperse nano-silicon dioxide, nano-ferrite and nano-aluminum nitride in an ethanol solution, add a coupling agent, adjust the temperature to 40°C, keep stirring for 1.5 hours, let stand for 5 hours, then filter, wash with water, and dry to constant weight to obtain a mixed filler.

[0042] S3. Add the mixed filler, activated carbonized material, modified graphite powder, epoxy resin and curing agent into a mixer and stir at a stirring speed of 200 r / min and a stirring temperature of 55° C. to obtain a mixed material.

[0043] S4, adding the above mixed material into a twin-screw extruder for melting, controlling the temperature in the twin-screw extruder at 120° C., extruding to obtain slices, and then crushing and grinding the slices to obtain modified epoxy resin powder.

[0044] S5. Add the modified epoxy resin powder, tinned copper powder and thermal conductive particles into a mixer and stir them at a stirring speed of 150 r / min. Mix them evenly to obtain a magnetic shielding powder coating.

[0045] Embodiment 2: A method for preparing an electromagnetic shielding powder coating, comprising the following steps:

[0046] S1. Weigh the raw materials: 3g of nano silicon dioxide; 3g of nano ferrite; 2g of nano aluminum nitride; 6g of activated carbonized material; 9g of modified graphite powder; 62g of epoxy resin; 4g of curing agent; 6g of tinned copper powder; 5g of thermal conductive particles; 15g of ethanol solution (mass fraction is 65%); 0.2g of coupling agent; the curing agent is sebacic acid dihydrazide, and the coupling agent is titanate coupling agent;

[0047] The thermally conductive particles are made of a composition of aluminum oxide and silicon carbide, and the mass ratio of aluminum oxide to silicon carbide is 1:1. The particle size of the thermally conductive particles is 0.1 mm.

[0048] S2. Evenly disperse nano-silicon dioxide, nano-ferrite and nano-aluminum nitride in an ethanol solution, add a coupling agent, adjust the temperature to 45°C, keep warm and stir for 1 hour, let stand for 6 hours, then filter, wash with water, and dry to constant weight to obtain a mixed filler.

[0049] S3. Add the mixed filler, activated carbonized material, modified graphite powder, epoxy resin and curing agent into a mixer and stir at a stirring speed of 200 r / min and a stirring temperature of 50° C. to obtain a mixture.

[0050] S4, adding the above mixed material into a twin-screw extruder for melting, controlling the temperature in the twin-screw extruder at 115° C., extruding to obtain slices, and then crushing and grinding the slices to obtain modified epoxy resin powder.

[0051] S5. Add the modified epoxy resin powder, tinned copper powder and thermal conductive particles into a mixer and stir them at a stirring speed of 150 r / min. Mix them evenly to obtain a magnetic shielding powder coating.

[0052] Embodiment 3: A method for preparing an electromagnetic shielding powder coating, comprising the following steps:

[0053] S1. Weigh the raw materials: 4g of nano silicon dioxide; 2g of nano ferrite; 2g of nano aluminum nitride; 4g of activated carbonized material; 12g of modified graphite powder; 58g of epoxy resin; 6g of curing agent; 8g of tinned copper powder; 4g of thermal conductive particles; 15g of ethanol solution (mass fraction is 65%); 0.2g of coupling agent; the curing agent is sebacic acid dihydrazide, and the coupling agent is titanate coupling agent;

[0054] The thermal conductive particles are made of silicon carbide, and the particle size (height) of the thermal conductive particles is 0.5 mm. The shape of the thermal conductive particles is a regular rhombic pyramid structure. The preparation method is: introducing silicon carbide gel into several forming holes of a mold plate, the forming holes on the mold plate are regular rhombic pyramids, performing heat treatment, and obtaining thermal conductive particles with a regular rhombic pyramid structure after demolding.

[0055] S2. Evenly disperse nano-silicon dioxide, nano-ferrite and nano-aluminum nitride in an ethanol solution, add a coupling agent, adjust the temperature to 40°C, keep stirring for 1.5 hours, let stand for 8 hours, then filter, wash with water, and dry to constant weight to obtain a mixed filler.

[0056] S3. Add the mixed filler, activated carbonized material, modified graphite powder, epoxy resin and curing agent into a mixer and stir at a stirring speed of 200 r / min and a stirring temperature of 50° C. to obtain a mixture.

[0057] S4, adding the above mixed material into a twin-screw extruder for melting, controlling the temperature in the twin-screw extruder at 120° C., extruding to obtain slices, and then crushing and grinding the slices to obtain modified epoxy resin powder.

[0058] S5. Add the modified epoxy resin powder, tinned copper powder and thermal conductive particles into a mixer and stir them at a stirring speed of 150 r / min. Mix them evenly to obtain a magnetic shielding powder coating.

[0059] Comparative Example 1: The difference from Example 1 is that no tinned copper powder is added;

[0060] Comparative Example 2: The difference from Example 1 is that no thermally conductive particles are added.

[0061] Comparative Example 3: The difference from Example 1 is that nano-aluminum nitride, nano-ferrite, tin-plated copper powder and thermal conductive particles are not added.

[0062] Electromagnetic shielding performance test:

[0063] The embodiment and the comparative example were sprayed onto a flat plate with a size of 20 mm×20 mm×1.5 mm. (1) The electromagnetic shielding performance of the coating was tested by an electromagnetic shielding tester at room temperature and a test frequency of 10.5 GHz.

[0064] (2) The heat dissipation performance was tested by heating one side of the flat plate. The results are shown in Table 1.

[0065] Table 1 Performance statistics of Examples 1 to 3 and Comparative Examples 1 to 3

[0066]

[0067]

[0068] It can be seen from Table 1 that the present invention can improve the electromagnetic shielding performance of the coating by adding tin-plated copper powder and nano-ferrite, and can make the coating have better heat dissipation performance by adding thermal conductive particles and nano-aluminum nitride, so as to effectively avoid affecting the heat dissipation performance of the applied equipment.

[0069] The above is an exemplary description of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. An electromagnetic shielding powder coating, characterized in that: The invention comprises the following raw materials in parts by weight: 2-4 parts of nano silicon dioxide; 2-3 parts of nano ferrite; 1-2 parts of nano aluminum nitride; 3-6 parts of activated carbonized material; 7-12 parts of modified graphite powder; Epoxy resin 58-74 parts; 3-6 parts of curing agent; 5-8 parts of tinned copper powder; 3-5 parts of thermal conductive particles.

2. The electromagnetic shielding powder coating according to claim 1, characterized in that: The thermally conductive particles are any one of aluminum oxide and silicon carbide or a combination of the two.

3. The electromagnetic shielding powder coating according to claim 2, characterized in that: The thermally conductive particles are spherical in shape.

4. The electromagnetic shielding powder coating according to claim 2, characterized in that: The shape of the thermally conductive particles is a regular triangular pyramid structure, and the preparation method thereof is as follows: introducing a thermally conductive particle material gel into a plurality of forming holes of a mold plate, wherein the forming holes on the mold plate are regular triangular pyramids, performing heat treatment, and obtaining thermally conductive particles with a regular triangular pyramid structure after demolding.

5. The electromagnetic shielding powder coating according to claim 1, characterized in that: The particle size of the thermally conductive particles is 0.1-0.5 mm.

6. A method for preparing the electromagnetic shielding powder coating according to any one of claims 1 to 5, characterized in that: The steps include: S1. Evenly disperse nano-silicon dioxide, nano-ferrite and nano-aluminum nitride in an ethanol solution, add a coupling agent, stir evenly, let stand for 5-8 hours, filter, wash with water, and dry to constant weight to obtain a mixed filler; S2, adding the mixed filler obtained in step S1, the activated carbonized material, the modified graphite powder, the epoxy resin, and the curing agent into a mixer and stirring them to obtain a mixed material; S3, melt-extrude the mixture obtained in step S2 to obtain slices, and then crush and grind the slices to obtain modified epoxy resin powder; S4, adding the modified epoxy resin powder obtained in step S3, the tinned copper powder and the thermal conductive particles into a mixer and stirring them evenly to obtain the desired magnetic shielding powder coating.

7. The method for preparing an electromagnetic shielding powder coating according to claim 6, characterized in that: In step S1, during stirring, the temperature is adjusted to 40-45° C., and the stirring is maintained at this temperature for 1-1.5 hours.

8. The method for preparing an electromagnetic shielding powder coating according to claim 6, characterized in that: In step S2, the stirring speed of the stirrer is 200 r / min, and the stirring temperature is 50-55°C.

9. The method for preparing an electromagnetic shielding powder coating according to claim 6, characterized in that: In step S3, a twin-screw extruder is used for melt extrusion, and the temperature in the twin-screw extruder is controlled at 115-120°C.

10. The method for preparing an electromagnetic shielding powder coating according to claim 6, characterized in that: In step S4, the stirring speed of the stirrer is 150 r / min.

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