Electromagnetic shielding coating composition as well as preparation method and application thereof

Abstract

The invention discloses an electromagnetic shielding coating composition as well as a preparation method and application thereof, and relates to the technical field of electromagnetic shielding materials. The conductive adhesive comprises the following components in parts by weight: 100 parts of organic silicon resin, 100-400 parts of conductive filler, 1-20 parts of a vulcanizing agent, 0.1-2 parts of a catalyst, 0.1-10 parts of a dispersing agent, 0.1-10 parts of an anti-settling agent, 0.1-10 parts of a powder orientation agent and 50-500 parts of a solvent, the conductive filler comprises nickel-plated carbon nanotubes. The nickel-plated carbon nanotubes are adopted as the conductive filler, the conductivity is better, the electromagnetic shielding effect is better, and meanwhile, nickel is plated on the surfaces of the carbon nanotubes, so that the problems that the carbon nanotubes are extremely easy to agglomerate and difficult to disperse are solved; and the anti-settling agent and the powder orientation agent are cooperatively added to inhibit the settling problem of the nickel-plated carbon nanotubes. The electromagnetic shielding coating composition provided by the invention is good in electromagnetic shielding effect, uniform in dispersion, not easy to settle and suitable for electromagnetic shielding performance requirements of high-power and high-frequency electronic components.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic shielding materials, in particular to an electromagnetic shielding coating composition and a preparation method and application thereof. BACKGROUND

[0002] As a kind of functional coating, electromagnetic wave shielding coating is widely used in military industry, consumer electronics, automotive electronics, 5G communication and medical treatment and other fields. This kind of coating can be sprayed or squeegeed on rubber products, engineering plastics, glass steel, wood, cement wall and other non-metallic materials by mixing resin and conductive particles in chemical solvent, and a continuous conductive layer is formed after solidification to realize the shielding function of electromagnetic wave. When electromagnetic wave reaches the surface of the coating, electromagnetic wave is reflected at the interface due to the difference in wave impedance between the conductive coating and air; this part of energy is directly blocked outside, and the reflection efficiency depends on the discontinuity of interface impedance; the electromagnetic wave that is not reflected enters the coating, and the conductive filler induces eddy current to convert electromagnetic energy into heat energy consumption. Electromagnetic wave shielding coating realizes electromagnetic shielding function through reflection and heat energy consumption to ensure the stable use state of the product. Due to the characteristics of room temperature curing, flexible and convenient construction and strong adhesion, electromagnetic shielding coating is currently the most simple processing method for electromagnetic shielding of non-metallic shell of mobile phone, display, printer and various instruments.

[0003] However, the shielding efficiency of the existing electromagnetic shielding coating is low, which cannot meet the stringent requirements of high-power high-frequency electronic components on electromagnetic shielding performance, and cannot fully guarantee the operation reliability. At the same time, as a kind of nanometer material with excellent conductivity, carbon nanotube (CNT) is difficult to realize uniform dispersion in the electromagnetic shielding coating system, so that the advantages of its conductivity cannot be fully exerted. In addition, CNT electromagnetic shielding coating is prone to sedimentation during storage, which further affects the stability and use effect of the coating.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide an electromagnetic shielding coating composition and a preparation method and application thereof.

[0006] The present application is realized as follows: In a first aspect, the present application provides an electromagnetic shielding coating composition, which comprises, by weight, 100 parts of silicone resin, 100-400 parts of conductive filler, 1-20 parts of vulcanizing agent, 0.1-2 parts of catalyst, 0.1-10 parts of dispersing agent, 0.1-10 parts of anti-settling agent, 0.1-10 parts of powder orientation agent and 50-500 parts of solvent; the conductive filler comprises nickel-plated carbon nanotube.

[0007] Secondly, the present invention provides a method for preparing an electromagnetic shielding coating composition as described in any of the foregoing embodiments, comprising mixing an organosilicon resin, a conductive filler, a vulcanizing agent, a dispersant, an anti-settling agent, a powder orienting agent, a catalyst, and a solvent in a certain proportion to obtain an electromagnetic shielding coating slurry.

[0008] Thirdly, the present invention provides the application of an electromagnetic shielding coating composition as described in any of the foregoing embodiments or an electromagnetic shielding coating composition prepared by any of the foregoing embodiments in any of the fields of electronic products, communication materials and medical devices.

[0009] Preferably, the process includes coating an electromagnetic shielding coating composition onto a substrate and curing it to form an electromagnetic shielding layer.

[0010] Preferably, the coating method includes any one of spraying, scraping, or dipping.

[0011] The present invention has the following beneficial effects: This invention provides an electromagnetic shielding coating composition, its preparation method, and its application. By using nickel-plated carbon nanotubes as a conductive filler, it achieves better conductivity and superior electromagnetic shielding effect. Furthermore, the nickel plating on the surface of the carbon nanotubes solves the problems of easy agglomeration and difficulty in dispersion. The addition of anti-settling agents and powder orientation agents further suppresses the sedimentation of the nickel-plated carbon nanotubes. The electromagnetic shielding coating composition provided by this invention offers excellent electromagnetic shielding performance, uniform dispersion, and is not prone to sedimentation, making it suitable for the electromagnetic shielding performance requirements of high-power, high-frequency electronic components. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0013] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0014] In a first aspect, the present invention provides an electromagnetic shielding coating composition, comprising, by weight, 100 parts of silicone resin, 100-400 parts of conductive filler, 1-20 parts of vulcanizing agent, 0.1-2 parts of catalyst, 0.1-10 parts of dispersant, 0.1-10 parts of anti-settling agent, 0.1-10 parts of powder orienting agent, and 50-500 parts of solvent; the conductive filler includes nickel-plated carbon nanotubes.

[0015] By using nickel-plated carbon nanotubes as conductive fillers, the conductivity is improved, resulting in superior electromagnetic shielding. Furthermore, the nickel plating on the surface of the carbon nanotubes solves the problems of easy agglomeration and difficulty in dispersion. The addition of anti-settling agents and powder orienting agents further suppresses the sedimentation of the nickel-plated carbon nanotubes. The electromagnetic shielding coating composition provided by this invention offers excellent electromagnetic shielding performance, uniform dispersion, and is not prone to sedimentation, making it suitable for the electromagnetic shielding performance requirements of high-power, high-frequency electronic components.

[0016] In an optional embodiment, the nickel content of the nickel-plated carbon nanotubes is ≥90wt%.

[0017] Preferably, depending on the different performance requirements of the electromagnetic shielding coating, other existing conductive fillers can be added to the conductive filler based on the addition of nickel-plated carbon nanotubes for compounding. For example, the conductive filler may also include at least one of carbon nanotubes, nickel-plated graphite, silver powder, silver-plated aluminum powder and silver-plated glass powder, and the mass percentage of nickel-plated carbon nanotubes in the conductive filler shall be ≥20% to ensure that the raw materials of the electromagnetic shielding coating composition are evenly distributed.

[0018] In an optional embodiment, the viscosity of the silicone resin is 100~500000 Pa·s, for example, it can be any value or a range of any two values ​​among 100 Pa·s, 1000 Pa·s, 10000 Pa·s, 100000 Pa·s, 200000 Pa·s, 100 Pa·s, 300000 Pa·s, 400000 Pa·s or 500000 Pa·s.

[0019] Preferably, the silicone resin includes at least one of polydimethylsiloxane resin and silicone oil, such as 107 glue.

[0020] In an optional embodiment, the anti-settling agent includes at least one of polyethylene wax paste, talc, diatomaceous earth, BYK302, and BYK163.

[0021] By adding the aforementioned anti-settling agent, the viscosity of the system can be increased or a thixotropic structure can be formed, creating a physical barrier on the surface of nickel-plated carbon nanotubes, reducing the aggregation between nickel-plated carbon nanotubes, and enhancing the suspension capacity.

[0022] Preferably, the powder orientation agent includes at least one of aluminum silver paste, cellulose acetate butyrate, Dow Corning DC3, BYK410 and PN411.

[0023] By adding the above-mentioned powder orientation agent, the molecular structure of the powder orientation agent interacts with the surface of the nickel-plated carbon nanotubes, causing the nickel-plated carbon nanotubes to be oriented in the system, reducing the disordered aggregation and settling between the nickel-plated carbon nanotubes.

[0024] By using anti-settling agents and powder orientation agents in synergy, the rheological properties of the system are improved to enhance suspension capacity, and the arrangement of nickel-plated carbon nanotubes is controlled to reduce aggregation and sedimentation, thereby achieving the effect of inhibiting the sedimentation of nickel-plated carbon nanotubes.

[0025] Preferably, the dispersant includes at least one of sodium hexametaphosphate, polyethylene glycol, polyvinylpyrrolidone, hydroxymethyl cellulose, Si-69, BYK110, and BYK2155.

[0026] Preferably, the solvent includes at least one of ethyl acetate, butyl acetate, toluene, xylene, isoparaffins, white spirit, and paraffin oil.

[0027] The aforementioned dispersant can directly inhibit the sedimentation of nickel-plated carbon nanotubes through adsorption, wetting, and anti-aggregation effects. The aforementioned solvent provides a suitable dispersion environment, supporting the dispersant, anti-settling agent, and powder orientation agent to perform their respective functions, thus enabling the electromagnetic shielding coating composition to form a stable dispersion system, thereby keeping the nickel-plated carbon nanotubes in a good suspended state in the coating.

[0028] Preferably, the vulcanizing agent includes at least one selected from di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,4-dichlorobenzoyl peroxide, hydrogen-containing silicone oil, tetraethyl orthosilicate, and vinyltributylone oxime silane.

[0029] By adding one or more of the above-mentioned vulcanizing agents, the organosilicon resin can undergo a cross-linking reaction during the curing process, thereby improving the physical properties (such as hardness, temperature resistance, adhesion, etc.) of the electromagnetic shielding coating composition, and thus stabilizing the curing and technical performance of the electromagnetic shielding coating composition.

[0030] Preferably, the catalyst comprises at least one of dibutyltin dilaurate or a platinum catalyst, wherein the platinum catalyst may be, for example, chloroplatinic acid.

[0031] By adding one or more of the above-mentioned catalysts to the electromagnetic shielding coating composition, the cross-linking reaction between the vulcanizing agent and the silicone resin can be accelerated, thereby speeding up the curing speed of the electromagnetic shielding coating composition or reducing the curing condition requirements, and improving production efficiency and process adaptability.

[0032] Secondly, the present invention provides a method for preparing an electromagnetic shielding coating composition as described in any of the foregoing embodiments, comprising mixing an organosilicon resin, a conductive filler, a vulcanizing agent, a dispersant, an anti-settling agent, a powder orienting agent, a catalyst, and a solvent in a certain proportion to obtain an electromagnetic shielding coating slurry.

[0033] It should be noted that electromagnetic shielding coating slurry is one form of electromagnetic shielding coating composition. When electromagnetic shielding coating slurry is applied to a specific material surface, it is coated onto the substrate and cured to form an electromagnetic shielding coating. This electromagnetic shielding coating is another form of electromagnetic shielding coating composition.

[0034] In an optional embodiment, the method for preparing nickel-plated carbon nanotubes includes the following steps: S01. Purification and Oxidation: Carbon nanotubes are immersed in an acid solution for purification and oxidation to remove impurities (such as catalyst residues, amorphous carbon, etc.) remaining on the surface of the carbon nanotubes during the preparation process. At the same time, defect sites on the carbon nanotube walls, such as vacancies, edges, and breaks, are oxidized by the acid to generate a large number of oxygen-containing functional groups, such as hydroxyl (-OH), carboxyl (-COOH), and carbonyl (C=O). These functional groups will adhere to the surface of the carbon nanotubes, which is conducive to the smooth progress of subsequent reactions.

[0035] Preferably, the acid solution includes one or more of 1-5 mol / L nitric acid or 1-5 mol / L sulfuric acid.

[0036] S02. Preparation of mixed solution: Dissolve palladium chloride in hydrochloric acid solution to obtain colloidal palladium solution. Then add stannous chloride and sodium chloride solution to colloidal palladium solution, heat and stir to mix. Heating and stirring can ensure that palladium chloride and stannous chloride are evenly dispersed in the mixed solution, which is beneficial to the uniform surface activation of carbon nanotubes.

[0037] Preferably, the hydrochloric acid solution is prepared by mixing 35-40% hydrochloric acid and deionized water at a volume ratio of 1:0.8-1.2; the mass ratio of palladium chloride to the volume ratio of the hydrochloric acid solution is 0.15-0.16 g:10 mL.

[0038] Preferably, the mass ratio of stannous chloride to palladium chloride is 1~10:0.15~0.16.

[0039] Preferably, the concentration of the sodium chloride solution is 0.1~0.2 g / ml.

[0040] Preferably, the mixing temperature for heating and stirring the colloidal palladium solution, stannous chloride and sodium chloride solution is 55~65℃, and the holding time is 50~70min.

[0041] S03. Activation: Carbon nanotubes are placed in a mixed solution of colloidal palladium and stannous chloride and heated for activation. Colloidal palladium provides palladium particles, which are adsorbed onto the surface of carbon nanotubes. Stannous chloride helps the palladium particles to better adhere to the surface of carbon nanotubes and activate them, thereby forming uniformly distributed palladium catalytic active sites on the surface of carbon nanotubes, providing the necessary catalytic basis for subsequent electroless nickel plating.

[0042] In an optional embodiment, during the activation process of the mixed solution and carbon nanotubes, the volume ratio of the mixed solution to the mass ratio of the carbon nanotubes is 500~550ml:10g, and the activation is carried out by heating and holding at a temperature of 55~65℃ for 50~70min.

[0043] S04. Debonding: In order to ensure the stable connection between nickel and carbon nanotubes, preferably, the activated carbon nanotubes are further subjected to ultrasonic debonding. The debonding solution is prepared by mixing hydrochloric acid (35-40% by mass) and deionized water at a volume ratio of 1:8-10. The debonding temperature is 40-50°C and the debonding time is 3-8 minutes.

[0044] S05, Electroless Nickel Plating: Activated carbon nanotubes are placed in a plating solution for electroless nickel plating.

[0045] In an optional embodiment, during the electroless nickel plating process, the plating solution includes: NiSO4 0.03~0.05mol / L, Na3C6H5O7 0.05~0.07mol / L, (NH4)2SO4 0.06~0.07mol / L, NaH2PO2 0.1~0.2mol / L, NaOH 0.05~0.15mol / L; the amount of carbon nanotubes added to the plating solution is 1~3g / L.

[0046] Preferably, electroless nickel plating involves placing activated carbon nanotubes in a plating solution and heating them under reflux for 55-65°C for 40-50 minutes.

[0047] By selecting the above-mentioned plating solution and electroless nickel plating parameters, a nickel layer can be uniformly distributed on the surface of the carbon nanotubes, resulting in a nickel content of ≥90wt% for the nickel-plated carbon nanotubes, which is beneficial to improving the electromagnetic shielding performance of the nickel-plated carbon nanotubes.

[0048] In an optional embodiment, the method for preparing the electromagnetic shielding coating slurry includes planetary mixing of organosilicon resin, conductive filler, dispersant, anti-settling agent, powder orienting agent and vulcanizing agent, followed by high-speed shear mixing with solvent, and then low-speed shear mixing with catalyst to obtain the electromagnetic shielding coating slurry, wherein the conductive filler is the nickel-plated carbon nanotubes obtained in the above steps.

[0049] Preferably, the parameters for planetary mixing include: rotation speed of 400~1200 rpm and mixing time of 1~4 h. By using planetary mixing to mix silicone resin, conductive filler, dispersant, anti-settling agent, powder orienting agent, the dispersant, anti-settling agent, powder orienting agent, and vulcanizing agent can be uniformly dispersed into the silicone resin and conductive filler system, while simultaneously expelling air bubbles generated inside the resin and during the mixing process, ensuring uniform mixing of all raw materials in the electromagnetic shielding coating slurry.

[0050] Preferably, the parameters for high-speed shear mixing include: rotation speed of 400~2200 rpm and mixing time of 10~60 min. After the above raw materials are mixed evenly, a solvent is added for high-speed shear mixing, which can quickly and evenly disperse the silicone resin, conductive filler, dispersant, anti-settling agent, powder orienting agent and vulcanizing agent into the solvent.

[0051] Preferably, the parameters for low-speed shear mixing include: rotation speed of 400~1000 rpm and mixing time of 1~10 min. Finally, the catalyst is added and mixed at low speed to ensure uniform dispersion of the catalyst in the system.

[0052] Thirdly, the present invention provides the application of an electromagnetic shielding coating composition as described in any of the foregoing embodiments or an electromagnetic shielding coating composition prepared by any of the foregoing embodiments in any of the fields of electronic products, communication materials and medical devices.

[0053] Preferably, the process includes coating an electromagnetic shielding coating composition onto a substrate and curing it to form an electromagnetic shielding layer.

[0054] Preferably, the coating method includes any one of spraying, scraping, or dipping.

[0055] Example 1 This embodiment provides an electromagnetic shielding coating composition, which, by weight, comprises 100 parts of polydimethylsiloxane resin, 100 parts of nickel-plated carbon nanotubes, 2.5 parts of di-tert-butyl peroxide (TBP), 0.7 parts of chloroplatinic acid, 1 part of sodium hexametaphosphate, 2 parts of diatomaceous earth, 1 part of aluminum silver paste, and 120 parts of butyl acetate.

[0056] The viscosity of the polydimethylsiloxane resin is 10000 Pa·s.

[0057] This embodiment also provides a method for preparing an electromagnetic shielding coating composition, comprising: first preparing nickel-plated carbon nanotubes; then mixing polydimethylsiloxane resin, nickel-plated carbon nanotubes, sodium hexametaphosphate, diatomaceous earth, aluminum silver paste and di-tert-butyl peroxide (TBP) in a planetary mixer at a speed of 1200 rpm for 60 min; then adding butyl acetate and mixing in a high-speed shear mill at a speed of 1600 rpm for 60 min; finally adding chloroplatinic acid and continuing to mix in a high-speed shear mill at a speed of 1000 rpm for 5 min to obtain an electromagnetic shielding coating slurry.

[0058] The preparation method of nickel-plated carbon nanotubes is as follows: S01. Purification: Immerse 100g of carbon nanotubes in 1L of 5mol / L nitric acid solution for purification and oxidation to remove impurities (such as catalyst residue, amorphous carbon, etc.) remaining on the surface of the carbon nanotubes during the preparation process.

[0059] S02. Preparation of the mixed solution: Mix 5 mL of 35% hydrochloric acid with 5 mL of deionized water to obtain a hydrochloric acid solution; add 0.155 g of palladium chloride to the hydrochloric acid solution and dissolve to obtain a colloidal palladium solution. Add 8 g of SnCl2·2H2O to the colloidal palladium solution and stir to dissolve. Then add 500 mL of 0.15 g / mL sodium chloride solution, heat at 60 °C, stir magnetically to mix, and keep at 60 °C for 1 h to obtain the mixed solution.

[0060] S03, Activation: Take 10g of carbon nanotubes obtained in step S01 and disperse them in the mixed solution obtained in step S02. Keep them at 60℃ for 1h for heating activation. After activation, filter and wash to obtain carbon nanotubes.

[0061] S04, Degellation: The activated carbon nanotubes obtained in step S03 are placed in a dilute hydrochloric acid solution (37% hydrochloric acid and deionized water mixed at a volume ratio of 1:9) at 45°C and ultrasonically degellated for 5 min. After degellation, the nanotubes are filtered, washed, and dried to obtain the activated and degellated carbon nanotubes.

[0062] S05, Electroless Nickel Plating: Using a three-hole flask as the reaction vessel, the carbon nanotubes obtained in step S04 are placed in the plating solution, heated in a water bath at 60°C and connected to a condenser for reflux, and stirred with magnetic force to perform electroless nickel plating for 45 minutes.

[0063] The plating solution contains 0.04 mol / L NiSO4, 0.06 mol / L Na3C6H5O7, 0.064 mol / L (NH4)2SO4, 0.16 mol / L NaH2PO2, 0.1 mol / L NaOH, and 2 g / L SO4 to obtain carbon nanotubes.

[0064] S06. Post-treatment: The reaction solution after plating is filtered through a 0.22μm microporous membrane to separate the nickel-plated carbon nanotubes and the plating solution. The separated nickel-plated carbon nanotubes are repeatedly washed with deionized water and vacuum dried for later use.

[0065] The nickel content of the nickel-plated carbon nanotubes obtained in this embodiment is 90 wt%.

[0066] Examples 2-5 and Comparative Examples 1-2 also provide an electromagnetic shielding coating composition and its preparation method. The raw material selection and preparation method are the same as those in Example 1. The only difference is that the proportions of each raw material in the electromagnetic shielding coating composition are different, as shown in Table 1.

[0067] Table 1 Formulation of electromagnetic shielding coating composition (unit: parts by weight)

[0068] Comparative Example 8 This comparative example provides an electromagnetic shielding coating composition, the raw material ratio and preparation method of which are the same as those in Example 1, the only difference being that 10 parts of carbon nanotubes (equivalent to the weight of carbon nanotubes before nickel plating in Example 1) are used instead of 100 parts of nickel-plated carbon nanotubes.

[0069] Comparative Example 9 This comparative example provides an electromagnetic shielding coating composition, whose raw material ratio and preparation method are the same as those of Comparative Example 8, the only difference being the anti-settling agent 10 and the powder orientation agent 5.

[0070] Comparative Example 10 This comparative example provides an electromagnetic shielding coating composition, whose raw material ratio and preparation method are the same as those in Example 1, except that nickel-plated graphite is used instead of nickel-plated carbon nanotubes.

[0071] Comparative Example 11 This comparative example provides an electromagnetic shielding coating composition, the raw material ratio and preparation method of which are similar to those of Example 1, the only difference being that the chemical composition of the plating solution is only sodium sulfate solution.

[0072] Experimental Example 1 Viscosity and storage time tests were conducted on the electromagnetic shielding coating compositions prepared in Examples 1-5 and Comparative Examples 1-11. Then, each electromagnetic shielding coating composition was coated onto a silicone rubber strip substrate. After curing, an electromagnetic shielding coating was formed. The adhesion between the electromagnetic shielding coating and the substrate, the volume resistivity of the electromagnetic shielding coating, and the shielding effectiveness were tested, and the results are shown in Table 2.

[0073] The viscosity test was performed using the rotational viscometer method, which can be found in GB / T 2794-2013 "Determination of Viscosity of Adhesives".

[0074] The method for testing storage time includes: sealing and encapsulating the electromagnetic shielding coating compositions prepared in Examples 1-5 and Comparative Examples 1-2, storing them at 25±2℃ and 60%±5% RH humidity, and periodically (e.g., 1 day, 3 days, 7 days, 14 days, 30 days, 60 days, 90 days, 120 days, 150 days and 180 days) to test viscosity, sedimentation, etc., to determine whether the coating still meets the usage requirements.

[0075] Adhesion is tested using the cross-cut test, specifically referring to GB / T 9286-1998 "Cross-cut test for paint and varnish films". If the edges of the cross-cut are completely smooth with no coating peeling, corresponding to grade 0 or 1 in the standard (grade 1 allows for a very small area of ​​peeling at the intersection of the squares, ≤5%), then the adhesion is considered good. If the area of ​​coating peeling within the squares is greater than 5%, or if there is obvious peeling at the edges, corresponding to grade 2 or below in the standard, then the adhesion is considered unqualified.

[0076] Volume resistivity was measured using the four-probe method, referring to MIL-DTL-83528.

[0077] The shielding effectiveness was tested using the shielding chamber method (window method) to assess the electromagnetic shielding capability of the electromagnetic shielding coating in the range of 200MHz to 10GHz, with reference to MIL-DTL-83528.

[0078] Table 2. Performance of Electromagnetic Shielding Coating Compositions and Electromagnetic Shielding Coatings

[0079] As shown in Table 2, the electromagnetic shielding coating composition provided in this embodiment of the invention has a moderate viscosity, is easy to level, and ensures uniform thickness throughout the electromagnetic shielding coating. The electromagnetic shielding coating composition exhibits good adhesion to the substrate, with no powder shedding. Furthermore, the electromagnetic shielding coating composition has a low volume resistivity and high shielding effectiveness, demonstrating excellent electromagnetic shielding performance, making it suitable for high-power, high-frequency products. Additionally, the electromagnetic shielding coating composition provided in this embodiment of the invention shows almost no delamination after 6 months of storage. Therefore, the electromagnetic shielding coating composition provided in this embodiment of the invention has advantages such as stable conductivity, high shielding effectiveness, strong adhesion, long shelf life, and high reliability.

[0080] Comparative Example 1, without the addition of an anti-settling agent, showed significant stratification of the electromagnetic shielding coating composition after six months of storage, indicating poor storage stability. Comparative Example 2, by reducing the amount of nickel-plated carbon nanotubes, resulted in a significant increase in the volume resistivity of the electromagnetic shielding coating and a decrease in shielding effectiveness. Comparative Example 3, by increasing the amount of nickel-plated carbon nanotubes, resulted in a significant increase in the viscosity of the electromagnetic shielding coating composition, leading to severe powder shedding during the adhesion test and failure to pass the adhesion test.

[0081] Comparative Example 4 reduced the amount of anti-settling agent added, resulting in poor storage stability of the electromagnetic shielding coating composition, with obvious stratification appearing after 3 months of storage; Comparative Example 5 increased the amount of anti-settling agent added, but the performance was comparable to that of Example 1, indicating that excessive addition of anti-settling agent cannot infinitely improve the overall performance of the electromagnetic shielding coating composition.

[0082] Comparative Example 6 reduced the amount of powder orientation agent added, resulting in the electromagnetic shielding coating peeling off at the edges during the adhesion test, and the adhesion test failed. Comparative Example 7 increased the amount of powder orientation agent added, resulting in a significant increase in the volume resistivity of the electromagnetic shielding coating and a decrease in shielding effectiveness.

[0083] Comparative Example 8 used 10 parts by weight of ordinary carbon nanotubes (equivalent to the weight of the carbon nanotubes in Example 1 before nickel plating) instead of the nickel-plated carbon nanotubes of this application. Ordinary carbon nanotubes have a larger specific surface area, higher viscosity, and poor dispersibility, making it difficult to add in large quantities and prone to agglomeration. The resulting electromagnetic shielding coating composition had high viscosity, the carbon nanotubes were not easy to disperse, the volume resistivity was high, the shielding effectiveness was low, and the electromagnetic shielding performance was worse than that of the Example. Comparative Example 9 increased the amount of anti-settling agent and powder orientation agent based on Comparative Example 8, but it still could not solve the stability problem of the electromagnetic shielding coating composition. After 6 months of storage, the electromagnetic shielding coating composition showed obvious stratification.

[0084] Comparative Example 10 used nickel-plated graphite instead of nickel-plated carbon nanotubes, which caused the electromagnetic shielding coating to locally shed powder under the adhesion test, and the adhesion test failed. In addition, the storage stability of the electromagnetic shielding coating composition was also poor. After 6 months of storage, the electromagnetic shielding coating composition showed slight delamination.

[0085] Comparative Example 11 altered the chemical composition of the plating solution, resulting in a significant decrease in nickel plating performance. The conductivity and dispersibility of powders such as carbon nanotubes were insufficient, which in turn led to a significant increase in the volume resistivity of the electromagnetic shielding coating composition and a substantial reduction in shielding effectiveness. At the same time, the adhesion between the coating and the substrate deteriorated, resulting in large-area powder shedding during the adhesion test. Furthermore, the coating was prone to delamination during storage, and its overall performance was severely substandard.

[0086] This embodiment provides an electromagnetic shielding coating composition, its preparation method, and its application, which have at least the following advantages: By plating nickel onto the surface of carbon nanotubes, the specific surface area of ​​the surface-modified carbon nanotubes is significantly reduced, thereby improving the dispersion ability of carbon nanotubes. At the same time, the nickel content of nickel-plated carbon nanotubes can reach more than 90%, which improves the conductivity and electromagnetic shielding effect of the electromagnetic shielding coating composition. Furthermore, nickel-plated carbon nanotubes also have a certain reinforcing effect.

[0087] Surface-modified carbon nanotubes can be well dispersed in the resin matrix using traditional equipment such as planetary mixers and high-speed dispersers. The preparation process is simple, omitting the step of pre-dispersing carbon nanotubes and preparing a highly concentrated carbon nanotube slurry before dilution.

[0088] The embodiments of the present invention improve the fluidity of the electromagnetic shielding coating composition by adjusting the type and amount of solvent to facilitate construction. In order to prevent nickel-plated carbon nanotubes from settling in the system, anti-settling agents and powder orienting agents are added to inhibit the settling of nickel-plated carbon nanotube powder.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic shielding coating composition, characterized in that, By weight, it comprises 100 parts of silicone resin, 100-400 parts of conductive filler, 1-20 parts of vulcanizing agent, 0.1-2 parts of catalyst, 0.1-10 parts of dispersant, 0.1-10 parts of anti-settling agent, 0.1-10 parts of powder orientation agent, and 50-500 parts of solvent; the conductive filler includes nickel-plated carbon nanotubes.

2. The electromagnetic shielding coating composition according to claim 1, characterized in that, The nickel content of the nickel-plated carbon nanotubes is ≥90wt%; Preferably, the conductive filler further includes at least one of carbon nanotubes, nickel-plated graphite, silver powder, silver-plated aluminum powder, and silver-plated glass powder, and the mass percentage of the nickel-plated carbon nanotubes in the conductive filler is ≥20%.

3. The electromagnetic shielding coating composition according to claim 1, characterized in that, The viscosity of the organosilicon resin is 100~500000 Pa·s; Preferably, the silicone resin includes at least one of polydimethylsiloxane resin and silicone oil, wherein the silicone oil includes 107 glue.

4. The electromagnetic shielding coating composition according to claim 1, characterized in that, The anti-settling agent includes at least one of polyethylene wax paste, talc powder, diatomaceous earth, BYK302 and BYK163; Preferably, the powder orientation agent includes at least one of aluminum silver paste, cellulose acetate butyrate, Dow Corning DC3, BYK410 and PN411; Preferably, the dispersant comprises at least one of sodium hexametaphosphate, polyethylene glycol, polyvinylpyrrolidone, hydroxymethyl cellulose, Si-69, BYK110, and BYK2155; Preferably, the solvent includes at least one selected from ethyl acetate, butyl acetate, toluene, xylene, isoalkanes, white spirit, and paraffin oil; Preferably, the vulcanizing agent comprises at least one selected from di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,4-dichlorobenzoyl peroxide, hydrogen-containing silicone oil, tetraethyl orthosilicate, and vinyltributylone oxime silane. Preferably, the catalyst comprises at least one of dibutyltin dilaurate or platinum catalyst.

5. A method for preparing an electromagnetic shielding coating composition as described in any one of claims 1 to 4, characterized in that, The method involves mixing the aforementioned silicone resin, conductive filler, vulcanizing agent, dispersant, anti-settling agent, powder orienting agent, catalyst, and solvent in a specific ratio to prepare an electromagnetic shielding coating slurry.

6. The preparation method according to claim 5, characterized in that, The preparation method of the nickel-plated carbon nanotubes includes: purifying and oxidizing the carbon nanotubes with an acid solution, then activating the carbon nanotubes with a mixed solution of colloidal palladium and stannous chloride, and then chemically plating the activated carbon nanotubes in a plating solution. Preferably, the acid solution comprises one or more of 1-5 mol / L nitric acid or 1-5 mol / L sulfuric acid; Preferably, the preparation of the mixed solution includes: dissolving palladium chloride in hydrochloric acid solution to obtain a colloidal palladium solution, and then adding stannous chloride and sodium chloride solution to the colloidal palladium solution, and heating and stirring to mix; Preferably, the hydrochloric acid solution is prepared by mixing 35-40% hydrochloric acid and deionized water at a volume ratio of 1:0.8-1.2; the mass ratio of palladium chloride to the volume ratio of the hydrochloric acid solution is 0.15-0.16 g:10 mL. Preferably, the mass ratio of stannous chloride to palladium chloride is 1~10:0.15~0.16; Preferably, the concentration of the sodium chloride solution is 0.1~0.2 g / ml; Preferably, the mixing temperature of the colloidal palladium solution, stannous chloride and sodium chloride solution during heating and stirring is 55~65℃, and the holding time is 50~70min.

7. The preparation method according to claim 6, characterized in that, During the activation process of the mixed solution and the carbon nanotubes, the volume ratio of the mixed solution to the mass ratio of the carbon nanotubes is 500~550ml:10g. The activation is carried out by heating and holding at a temperature of 55~65℃ for 50~70min. Preferably, the method further includes ultrasonically degelating the activated carbon nanotubes. The degelating solution is prepared by mixing 35-40% hydrochloric acid and deionized water at a volume ratio of 1:8-10. The degelating temperature is 40-50°C and the degelating time is 3-8 minutes.

8. The preparation method according to claim 6, characterized in that, In the electroless nickel plating process, the plating solution comprises: NiSO4 0.03~0.05mol / L, Na3C6H5O7 0.05~0.07mol / L, (NH4)2SO4 0.06~0.07mol / L, NaH2PO2 0.1~0.2mol / L, and NaOH 0.05~0.15mol / L; the amount of carbon nanotubes added to the plating solution is 1~3g / L. Preferably, the electroless nickel plating includes placing the activated carbon nanotubes in a plating solution and heating them under reflux for 55-65°C for 40-50 minutes.

9. The preparation method according to claim 5, characterized in that, The process involves planetary mixing of the silicone resin, conductive filler, dispersant, anti-settling agent, powder orienting agent, and vulcanizing agent, followed by high-speed shear mixing with the solvent, and then low-speed shear mixing with the catalyst to obtain an electromagnetic shielding coating slurry. Preferably, the parameters for planetary mixing include: rotation speed of 400~1200 rpm and mixing time of 1~4 h; Preferably, the parameters for the high-speed shear mixing include: rotation speed of 400~2200 rpm and mixing time of 10~60 min; Preferably, the parameters for the low-speed shear mixing include: rotation speed of 400~1000 rpm and mixing time of 1~10 min.

10. The application of an electromagnetic shielding coating composition as described in any one of claims 1 to 4 or an electromagnetic shielding coating composition prepared by any one of claims 5 to 9 in any field of electronic products, communication materials, and medical devices; Preferably, the method includes coating the electromagnetic shielding coating composition onto a substrate and curing it to form an electromagnetic shielding layer; Preferably, the coating method includes any one of spraying, scraping, or dipping.

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