Corrosion-resistant flaky silver-coated copper powder, preparation method thereof and electromagnetic shielding shell

Abstract

The invention discloses corrosion-resistant flaky silver-coated copper powder, a preparation method of the corrosion-resistant flaky silver-coated copper powder and an electromagnetic shielding shell, and the preparation method of the corrosion-resistant flaky silver-coated copper powder comprises the steps that flaky copper powder and a complexing agent are added into water to be evenly dispersed, and a water-based copper powder solution is obtained; adding the water-based copper powder solution and a corrosion inhibitor into a water solution containing a reducing agent, and uniformly dispersing to obtain a copper powder reducing solution; a silver-ammonia solution and a stabilizer are added into the copper powder reduction solution for a reduction reaction, silver-coated copper powder particles are obtained, and after precipitation and filtration, the corrosion-resistant flaky silver-coated copper powder is obtained; the stabilizer is obtained by carrying out a quaternization reaction on 3-dimethylamino-1-propanethiol and sodium 3-bromopropane sulfonate. The flaky copper powder and the silver ammonia react under the condition of the specific stabilizer, so that the coating property, the oxidation resistance, the coating uniformity and the compactness of the obtained silver-coated copper powder are effectively improved, and the obtained silver-coated copper powder is efficiently applied to an electromagnetic shielding shell.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding, and in particular relates to a corrosion-resistant flaky silver-coated copper powder and a preparation method thereof, and an electromagnetic shielding shell. Background Art

[0002] With the rapid development of 5G technology, the number of various wireless communication devices has increased dramatically, and the electromagnetic pollution problem caused by this has become increasingly serious. Electromagnetic radiation not only interferes with the normal operation of electronic equipment, but also poses potential hazards to human health. Therefore, the demand for high-performance electromagnetic interference (EMI) shielding materials is increasing day by day. Silver-coated copper powder has excellent electrical conductivity and corrosion resistance, and has become a hot spot in the research of electromagnetic shielding materials in recent years.

[0003] Corrosion-resistant flaky silver-coated copper powder is a flaky metal conductive powder that has been surface-coated. It has both the metallic conductivity of silver and bright colors. The characteristics of corrosion-resistant flaky silver-coated copper powder are obvious: bright colors, strong corrosion resistance, not easy to fade, strong metallic luster and conductivity, and low raw material cost. Corrosion-resistant flaky silver-coated copper powder is widely used in various industrial fields, such as inks, coatings, printing and packaging, printing and dyeing, automobiles, construction, home appliances and other industrial and decorative fields. In the field of electromagnetic shielding, the miniaturization and integration of 5G equipment have led to the use of harsh environments with high temperatures and complex environments such as coating solvents. Highly corrosion-resistant silver-coated copper can have corrosion resistance in solvent or high-heat application environments, thereby meeting the requirements of customers in the field of electromagnetic shielding for silver-coated copper powder to maintain a specific hue.

[0004] Patent publication CN118123016A provides a method for preparing uniformly coated silver-coated copper powder and silver-coated copper powder. Although it also involves a corrosion-resistant silver-coated copper powder, the method requires stannous chloride sensitization, and the process is complicated. In addition, silver ions will nucleate in large quantities under certain reducing conditions and grow by themselves to form silver particle powder, rather than being all directionally plated on the copper powder. This often results in a thin silver layer that is insufficient to block the contact between copper and oxygen, resulting in copper oxidation problems. Summary of the invention

[0005] Based on the above technical problems, the present invention provides a corrosion-resistant flaky silver-coated copper powder, a preparation method thereof and an electromagnetic shielding shell. By reacting flaky copper powder and silver ammonia under specific stabilizer conditions, the coating and oxidation resistance of the obtained silver-coated copper powder are effectively improved, and the coating uniformity and density are effectively improved, and the obtained silver-coated copper powder can be efficiently used in electromagnetic shielding shells.

[0006] The present invention provides a method for preparing a corrosion-resistant flaky silver-coated copper powder, comprising the following steps: S1, adding flaky copper powder and a complexing agent into water and dispersing them evenly to obtain an aqueous copper powder solution; S2, adding the aqueous copper powder solution and the corrosion inhibitor into the aqueous solution containing the reducing agent and dispersing them evenly to obtain a copper powder reduction solution; S3, adding the silver ammonia solution and the stabilizer to the copper powder reduction solution for reduction reaction, and filtering to obtain the corrosion-resistant flaky silver-coated copper powder; The stabilizer is obtained by quaternizing 3-dimethylamino-1-propanethiol and sodium 3-bromopropane sulfonate.

[0007] In the present invention, the structure of the stabilizer is shown below: In the present invention, on the basis of using silver ions to replace or reduce the surface of flaky copper powder to form silver-coated copper powder, a stabilizer obtained by quaternization reaction of 3-dimethylamino-1-propanethiol and sodium 3-bromopropane sulfonate is added. The stabilizer is essentially a zwitterionic surfactant containing a thiol group. The thiol group on the stabilizer can form Cu-S coordination with the flaky copper powder so that the flaky copper powder is adsorbed on the surface of the copper powder. The hydrophobic fatty chain group and the hydrophilic quaternary ammonium salt group and sulfonate group on the stabilizer not only enable the copper powder to be uniformly dispersed in the solution, but also the presence of the quaternary ammonium salt group can have a certain effect on the surface of the copper powder. Mild corrosion is carried out to increase the adsorption sites on the surface of the copper powder, which is helpful for the subsequent reduction of silver ions on the surface to form silver nanoparticles. At the same time, the sulfonate group has a certain adsorption and stabilization effect on silver ions, so that the silver ions will be directionally deposited on the copper surface to form a self-catalytic silver layer, which accelerates the deposition of silver on the copper powder surface and finally forms a dense silver coating layer on the copper powder surface. The diffusion, adsorption, nucleation and growth of silver ions in the solution are controlled, thereby changing the deposition density and morphology of silver on the copper powder, and finally making the obtained silver-coated copper powder dense and uniformly coated, and the antioxidant performance and conductive effect are significantly improved.

[0008] Preferably, in step S1, before adding the flaky copper powder and the complexing agent into water to be evenly dispersed, the step further includes first adding the flaky copper powder into an ethanol solution for alcohol washing, and then adding the flaky copper powder into an alkaline solution for alkaline washing; Preferably, the ethanol solution is an ethanol aqueous solution with a volume concentration of 93-98%, and the alkaline solution is a sodium hydroxide solution with a mass concentration of 1-10%.

[0009] In the present invention, by washing the flaky copper powder with alcohol and alkali, organic matter on the surface of the copper powder can be effectively removed, and the surface activity of the copper powder can be reduced, thereby providing a good foundation for subsequent silver coating.

[0010] Preferably, in step S1, the complexing agent is at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium aspartate diacetate, tetrasodium glutamate diacetate or trisodium methylglycine diacetate; Preferably, the mass ratio of the flaky copper powder to the complexing agent is 1:0.02-0.2.

[0011] In the present invention, the complexing agent can form a structurally stable complex with the enriched silver ammonium ions, thereby effectively stabilizing the silver ions in the solution and generating a dense silver coating layer on the surface of the copper powder.

[0012] Preferably, in step S2, the corrosion inhibitor is at least one of benzotriazole, methylbenzotriazole, mercaptobenzothiazole, sodium mercaptobenzothiazole, oleic acid imidazoline or benzimidazole; the reducing agent is at least one of glucose, citric acid, sodium citrate, sodium tartrate, ascorbic acid, ethylene glycol, formaldehyde, formic acid, acetaldehyde or glyoxylic acid; Preferably, the mass ratio of the flaky copper powder to the corrosion inhibitor and the reducing agent is 1:0.01-0.02:0.5-5.

[0013] In the present invention, the presence of the corrosion inhibitor can further enhance the corrosion resistance of the obtained silver-coated copper powder; the selection of the reducing agent not only avoids the strong reducing agent from quickly reducing the silver salt complex liquid to produce free nano-silver, but also avoids the weak reducing agent from being too low in activity and unable to reduce the silver salt complex liquid or having too low reduction efficiency.

[0014] Preferably, in step S3, the silver ammonia solution is obtained by adding silver nitrate to water to completely dissolve it, and then adding ammonia water to make the solution transparent; Preferably, the mass ratio of the flaky copper powder to silver nitrate and stabilizer is 1:0.1-2:0.05-0.5; Preferably, the stabilizer further comprises ammonium carbonate.

[0015] The present invention also provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the above preparation method.

[0016] The present invention also provides an electromagnetic shielding shell based on the corrosion-resistant flaky silver-coated copper powder, the surface of which is coated with an electromagnetic shielding water-based paint, which includes the flaky silver-coated copper powder and a water-based acrylic resin emulsion.

[0017] Preferably, the surface of the flaky silver-coated copper powder is grafted with a silane coupling agent; Preferably, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane, preferably 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane.

[0018] In the present invention, the surface of the silver-coated copper powder is modified by a silane coupling agent, so that the silver-coated copper powder has better interface properties, and when used in an electromagnetic shielding water-based coating, it can show stronger dispersibility and overall uniformity.

[0019] Preferably, the aqueous acrylic resin emulsion is prepared by copolymerizing acrylic ester monomers to form acrylic resin and then dissolving the copolymerized acrylic ester monomers in an aqueous solvent; the acrylic ester monomers include acrylic esters having lipophilic groups and acrylic esters having hydrophilic groups; Preferably, the acrylate monomer having a lipophilic group is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate or 2-ethylhexyl methacrylate, and the acrylate monomer having a hydrophilic group is at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate or polyethylene glycol monomethacrylate.

[0020] In the present invention, the acrylic resin formed by copolymerization of an acrylic acid ester monomer having a lipophilic group and an acrylic acid ester monomer having a hydrophilic group has amphoteric properties, which can coat the silver-coated copper powder, so that it is uniformly dispersed in an aqueous solvent, and is regulated to have appropriate viscosity and rheological properties, which helps to form better coating adhesion.

[0021] Preferably, the acrylic ester monomer further comprises an acrylic ester monomer having a tertiary amine group, preferably at least one of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, tert-butylaminoethyl acrylate or tert-butylaminoethyl methacrylate.

[0022] In the present invention, after the acrylate monomer having a tertiary amine group participates in the copolymerization, the obtained acrylic resin contains a tertiary amine group, and a quaternization reaction can be formed between the acrylic resin and the silver-coated copper powder modified by 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane, thereby further ensuring that the flaky silver-coated copper powder is evenly dispersed in the acrylic resin, so that the obtained coating forms a conductive cross-linked network, and the conductive shielding effect is further improved.

[0023] Beneficial effects of the present invention: (1) The present invention provides a method for preparing corrosion-resistant flaky silver-coated copper powder, which does not require sensitization and activation treatment of the copper powder surface in the early stage, has simple process steps, is easy to operate, and is easy to mass produce.

[0024] (2) The present invention provides a corrosion-resistant flaky silver-coated copper powder, which has no obvious elemental silver particles, a smooth silver layer on the powder surface, good density, high electrical conductivity, and good oxidation resistance, and is suitable for use as a conductive filler in the field of electronic pastes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a SEM image of the flaky silver-coated copper powder described in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] Hereinafter, the present invention will describe the technical solution in detail through specific embodiments, but it should be clearly stated that these embodiments are for illustration only and are not to be construed as limiting the scope of the present invention.

[0027] Example 1

[0028] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 96% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 5% sodium hydroxide solution, stir magnetically for 10 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 0.5 g of disodium ethylenediaminetetraacetate, and mixing by magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 10 g of sodium citrate to 50 mL of deionized water, stirring magnetically to dissolve completely, obtaining a reducing agent solution, and then adding 0.1 g of benzotriazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, obtaining a copper powder reducing solution; (4) adding 3.5 g of silver nitrate to 50 mL of deionized water, stirring magnetically for 5 min, adding ammonia solution with a concentration of 28%, stirring until the solution becomes transparent, and obtaining a silver-ammonia solution; adding 1 g of a stabilizer and the silver-ammonia solution to the copper powder reduction solution in sequence, stirring magnetically for 30 min, obtaining silver-coated copper powder particles, filtering, washing three times with ethanol and water by centrifugation, and drying in a vacuum drying oven at 60° C., obtaining the corrosion-resistant flaky silver-coated copper powder; The above stabilizer is prepared by the following method: 1.19 g of 3-dimethylamino-1-propanethiol and 2.26 g of sodium 3-bromopropane sulfonate were dissolved in 30 mL of ethanol, and the mixture was stirred under magnetic stirring at 60° C. for 24 h. After the reaction, the residual solvent was removed by distillation under reduced pressure, and the mixture was recrystallized three times using an ethanol / acetone mixed solution to obtain a white solid, which was the stabilizer. 1 H NMR (400MHz, DMSO), δ: 3.83 – 3.72(m, 4H), 3.56(s, 6H), 3.05(m, 2H), 2.58(m, 2H), 2.29(m, 2H), 2.07(m, 2H), 1.5(s,1H).

[0029] The flaky silver-coated copper powder prepared in this example was observed under a scanning electron microscope. Figure 1 As shown, it can be seen that the silver coating on the surface of the silver-coated copper powder is uniform and dense, completely coated and has good dispersion.

[0030] This embodiment also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, which specifically includes: (1) adding 1 g of γ-aminopropyltriethoxysilane to 20 mL of deionized water, stirring the mixture under magnetic stirring for 10 min, adding 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder, stirring the mixture under magnetic stirring for 20 min at 30° C., and obtaining a flaky silver-coated copper powder dispersion; (2) 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate and 0.4 g of 2-hydroxyethyl methacrylate were added to 20 mL of ethanol, and the mixture was stirred and mixed uniformly under nitrogen protection. Then, 0.02 g of azobisisobutyronitrile was added, and the mixture was heated to 70° C. in a water bath and stirred for reaction for 4 h. After the solvent was removed by distillation, an acrylic resin was obtained. The acrylic resin was added to water, and the mixture was stirred and dispersed uniformly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt %; (3) adding the flaky silver-coated copper powder dispersion to the acrylic resin emulsion, stirring the mixture by magnetic stirring for 25 minutes, and then adding 10 mL of anhydrous ethanol to dilute the mixture to obtain a water-based electromagnetic shielding coating; (4) Pour the water-based electromagnetic shielding coating into a spray gun, spray it evenly on the surface of the plastic substrate used as the electromagnetic shielding shell, and place it in a 120° C. forced air drying oven for 30 minutes to obtain the electromagnetic shielding shell.

[0031] Example 2

[0032] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 93% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 1% sodium hydroxide solution, stir magnetically for 15 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 1 g of tetrasodium glutamate diacetate, and mixing by magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 5 g of sodium tartrate to 50 mL of deionized water, stirring magnetically to dissolve completely, obtaining a reducing agent solution, and then adding 0.2 g of methylbenzotriazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, obtaining a copper powder reducing solution; (4) 2.5 g of silver nitrate was added to 50 mL of deionized water, and the mixture was mixed by magnetic stirring for 5 min. Then, a 28% ammonia solution was added and stirred until the solution became transparent to obtain a silver-ammonia solution. 0.5 g of a stabilizer and the silver-ammonia solution were added to the copper powder reduction solution in sequence. The mixture was reacted by magnetic stirring for 30 min to obtain silver-coated copper powder particles. The particles were filtered, washed three times by centrifugation with ethanol and water, and dried in a vacuum drying oven at 60° C. to obtain the corrosion-resistant flaky silver-coated copper powder. The stabilizer was obtained by referring to the method described in Example 1.

[0033] This embodiment also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, which specifically includes: (1) adding 1 g of γ-glycidyloxypropyltrimethoxysilane to 20 mL of deionized water, stirring the mixture under magnetic stirring for 10 min, adding 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder, stirring the mixture under magnetic stirring for 20 min at 30° C., and obtaining a flaky silver-coated copper powder dispersion; (2) 0.3 g of methyl acrylate, 0.4 g of ethyl methacrylate, 0.3 g of butyl acrylate and 0.4 g of 2-hydroxyethyl methacrylate were added to 20 mL of ethanol, and the mixture was stirred and mixed uniformly under nitrogen protection. Then, 0.02 g of azobisisobutyronitrile was added, and the mixture was heated to 70° C. in a water bath and stirred for reaction for 4 h. After the solvent was removed by distillation, an acrylic resin was obtained. The acrylic resin was added to water, and the mixture was stirred and dispersed uniformly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt %; (3) adding the flaky silver-coated copper powder dispersion to the acrylic resin emulsion, stirring the mixture by magnetic stirring for 25 minutes, and then adding 10 mL of anhydrous ethanol to dilute the mixture to obtain a water-based electromagnetic shielding coating; (4) Pour the water-based electromagnetic shielding coating into a spray gun, spray it evenly on the surface of the plastic substrate used as the electromagnetic shielding shell, and place it in a 120° C. forced air drying oven for 30 minutes to obtain the electromagnetic shielding shell.

[0034] Example 3

[0035] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 98% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 10% sodium hydroxide solution, stir magnetically for 5 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 2 g of ethylenediaminetetraacetic acid, and mixing with magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 15 g of ascorbic acid to 50 mL of deionized water, stirring magnetically to dissolve completely to obtain a reducing agent solution, and then adding 0.1 g of mercaptobenzothiazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, to obtain a copper powder reducing solution; (4) 4.5 g of silver nitrate was added to 50 mL of deionized water, and the mixture was mixed by magnetic stirring for 5 min. Then, a 28% ammonia solution was added and stirred until the solution became transparent to obtain a silver-ammonia solution. 1 g of a stabilizer, 1 g of ammonium carbonate and the silver-ammonia solution were added to the copper powder reduction solution in sequence. The mixture was reacted by magnetic stirring for 30 min to obtain silver-coated copper powder particles. The particles were filtered, washed three times by centrifugation with ethanol and water, and dried in a vacuum drying oven at 60° C. to obtain the corrosion-resistant flaky silver-coated copper powder. The stabilizer was obtained by referring to the method described in Example 1.

[0036] This embodiment also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, and specific reference is made to Embodiment 1.

[0037] Example 4

[0038] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is obtained by referring to the method described in Example 1.

[0039] This embodiment also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, which specifically includes: (1) adding 1 g of γ-aminopropyltriethoxysilane to 20 mL of deionized water, stirring the mixture under magnetic stirring for 10 min, adding 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder, stirring the mixture under magnetic stirring for 20 min at 30° C., and obtaining a flaky silver-coated copper powder dispersion; (2) 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate, 0.4 g of hydroxyethyl methacrylate and 0.2 g of dimethylaminoethyl acrylate were added to 20 mL of ethanol, stirred and mixed evenly under nitrogen protection, and then 0.02 g of azobisisobutyronitrile was added. The mixture was heated to 70° C. in a water bath and stirred for reaction for 4 h. After the solvent was removed by distillation, an acrylic resin was obtained. The acrylic resin was added to water, stirred and dispersed evenly, and an aqueous acrylic resin emulsion with a solid content of 30 wt% was obtained. (3) adding the flaky silver-coated copper powder dispersion to the acrylic resin emulsion, stirring the mixture by magnetic stirring for 25 minutes, and then adding 10 mL of anhydrous ethanol to dilute the mixture to obtain a water-based electromagnetic shielding coating; (4) Pour the water-based electromagnetic shielding coating into a spray gun, spray it evenly on the surface of the plastic substrate used as the electromagnetic shielding shell, and place it in a 120° C. forced air drying oven for 30 minutes to obtain the electromagnetic shielding shell.

[0040] Example 5

[0041] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is obtained by referring to the method described in Example 1.

[0042] This embodiment also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, which specifically includes: (1) 1 g of 3-chloropropyltriethoxysilane was added to 20 mL of deionized water, and the mixture was mixed by magnetic stirring for 10 min. Then, 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder was added, and the mixture was mixed by magnetic stirring for 20 min at 30° C. to obtain a flaky silver-coated copper powder dispersion; (2) 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate, 0.4 g of hydroxyethyl methacrylate and 0.2 g of dimethylaminoethyl acrylate were added to 20 mL of ethanol, stirred and mixed evenly under nitrogen protection, and then 0.02 g of azobisisobutyronitrile was added. The mixture was heated to 70° C. in a water bath and stirred for reaction for 4 h. After the solvent was removed by distillation, an acrylic resin was obtained. The acrylic resin was added to water, stirred and dispersed evenly, and an aqueous acrylic resin emulsion with a solid content of 30 wt% was obtained. (3) adding the flaky silver-coated copper powder dispersion to the acrylic resin emulsion, stirring the mixture by magnetic stirring for 25 minutes, and then adding 10 mL of anhydrous ethanol to dilute the mixture to obtain a water-based electromagnetic shielding coating; (4) Pour the water-based electromagnetic shielding coating into a spray gun, spray it evenly on the surface of the plastic substrate used as the electromagnetic shielding shell, and place it in a 120° C. forced air drying oven for 30 minutes to obtain the electromagnetic shielding shell.

[0043] Comparative Example 1 This comparative example proposes a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 96% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 5% sodium hydroxide solution, stir magnetically for 10 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 0.5 g of disodium ethylenediaminetetraacetate, and mixing by magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 10 g of sodium citrate to 50 mL of deionized water, stirring magnetically to dissolve completely, obtaining a reducing agent solution, and then adding 0.1 g of benzotriazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, obtaining a copper powder reducing solution; (4) Add 3.5 g of silver nitrate to 50 mL of deionized water, stir magnetically for 5 minutes, then add 28% ammonia solution, stir until the solution becomes transparent, and obtain a silver-ammonia solution; add the silver-ammonia solution to the copper powder reduction solution, stir magnetically for 30 minutes, and obtain silver-coated copper powder particles; filter, wash three times with ethanol and water by centrifugation, and dry in a vacuum drying oven at 60° C. to obtain the corrosion-resistant flaky silver-coated copper powder.

[0044] This comparative example also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, and specific reference is made to Example 1.

[0045] Comparative Example 2 This comparative example proposes a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 96% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 5% sodium hydroxide solution, stir magnetically for 10 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 0.5 g of disodium ethylenediaminetetraacetate, and mixing by magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 10 g of sodium citrate to 50 mL of deionized water, stirring magnetically to dissolve completely, obtaining a reducing agent solution, and then adding 0.1 g of benzotriazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, obtaining a copper powder reducing solution; (4) Add 3.5 g of silver nitrate to 50 mL of deionized water, stir magnetically for 5 minutes, then add 28% ammonia solution, stir until the solution becomes transparent, and obtain a silver-ammonia solution; add 1 g of ammonium carbonate and the silver-ammonia solution to the copper powder reduction solution in sequence, stir magnetically for 30 minutes, and obtain silver-coated copper powder particles, filter, wash three times with ethanol and water by centrifugation, and dry in a vacuum drying oven at 60° C. to obtain the corrosion-resistant flaky silver-coated copper powder.

[0046] This comparative example also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, and specific reference is made to Example 1.

[0047] Comparative Example 3 This comparative example proposes a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method: (1) Add 10 g of flaky copper powder (particle size of 5-10 μm) to 100 mL of 96% ethanol, stir magnetically for 30 min, filter, add to 100 mL of 5% sodium hydroxide solution, stir magnetically for 10 min, filter, and wash with deionized water by centrifugation until neutral to obtain pretreated flaky copper powder; (2) adding the pretreated flaky copper powder into 200 mL of deionized water, and then adding 0.5 g of disodium ethylenediaminetetraacetate, and mixing by magnetic stirring for 10 minutes to obtain an aqueous copper powder solution; (3) adding 10 g of sodium citrate to 50 mL of deionized water, stirring magnetically to dissolve completely, obtaining a reducing agent solution, and then adding 0.1 g of benzotriazole and the aqueous copper powder solution in sequence, stirring magnetically to mix for 20 minutes, obtaining a copper powder reducing solution; (4) Add 3.5 g of silver nitrate to 50 mL of deionized water, stir magnetically for 5 minutes, add 28% ammonia solution, stir until the solution becomes transparent, and obtain a silver ammonia solution; add 1 g of sodium dodecyl sulfate and the silver ammonia solution to the copper powder reduction solution, stir magnetically for 30 minutes, and obtain silver-coated copper powder particles, filter, wash three times with ethanol and water by centrifugation, and dry in a vacuum drying oven at 60° C. to obtain the corrosion-resistant flaky silver-coated copper powder.

[0048] This comparative example also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding shell, and specific reference is made to Example 1.

[0049] The square resistance and resistivity of the coating films (the size of the film samples is 10 cm×10 cm×50 μm) on the electromagnetic shielding shells prepared in the embodiments and comparative examples were tested by a four-probe resistivity meter, and the test was conducted again after being placed for 30 days. A vector network analyzer connected to two X-band waveguides was used to test the electromagnetic shielding performance of the coating films on the electromagnetic shielding shells prepared in the embodiments and comparative examples by a waveguide method at room temperature, a frequency band of X-band (8.2-18.0 GHz), and a bandwidth of 1 kHz. The test results are shown in Table 1.

[0050]

[0051] As shown in Table 1 above, the flaky silver-coated copper powder prepared in the embodiment has good conductivity and electromagnetic shielding performance after being used for film formation of water-based electromagnetic shielding coatings, and the resistivity value after natural placement for 30 days changes slightly, indicating that the flaky silver-coated copper powder prepared in the embodiment has good antioxidant properties. Among them, by comparing Example 1 with Comparative Examples 1-3, it can be seen that the selection of the stabilizer of the present invention enables silver to have a dense coating effect on the surface of the copper powder, and the obtained flaky silver-coated copper powder has excellent conductivity and antioxidant properties; by comparing Example 1, Example 4 and Example 5, it can be seen that the flaky silver-coated copper powder is modified by a specific silane coupling agent and placed in a specific water-based acrylic resin emulsion system, which will further improve the conductivity and electromagnetic shielding performance.

[0052] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing corrosion-resistant flaky silver-coated copper powder, characterized in that: The steps include: S1, adding flaky copper powder and a complexing agent into water and dispersing them evenly to obtain an aqueous copper powder solution; S2, adding the aqueous copper powder solution and the corrosion inhibitor into the aqueous solution containing the reducing agent and dispersing them evenly to obtain a copper powder reduction solution; S3, adding the silver ammonia solution and the stabilizer to the copper powder reduction solution for reduction reaction, and filtering to obtain the corrosion-resistant flaky silver-coated copper powder; The stabilizer is obtained by quaternizing 3-dimethylamino-1-propanethiol and sodium 3-bromopropane sulfonate.

2. The method for preparing the corrosion-resistant flaky silver-coated copper powder according to claim 1, characterized in that: In step S1, before adding the flaky copper powder and the complexing agent into water to be evenly dispersed, the step further includes first adding the flaky copper powder into an ethanol solution for alcohol washing, and then adding the flaky copper powder into an alkaline solution for alkaline washing; The ethanol solution is an ethanol aqueous solution with a volume concentration of 93-98%, and the alkaline solution is a sodium hydroxide solution with a mass concentration of 1-10%.

3. The method for preparing the corrosion-resistant flaky silver-coated copper powder according to claim 1 or 2, characterized in that: In step S1, the complexing agent is at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium aspartate diacetate, tetrasodium glutamate diacetate or trisodium methylglycine diacetate; The mass ratio of the flaky copper powder to the complexing agent is 1:0.02-0.

2.

4. The method for preparing the corrosion-resistant flaky silver-coated copper powder according to claim 1 or 2, characterized in that: In step S2, the corrosion inhibitor is at least one of benzotriazole, methylbenzotriazole, mercaptobenzothiazole, sodium mercaptobenzothiazole, oleic acid imidazoline or benzimidazole; the reducing agent is at least one of glucose, citric acid, sodium citrate, sodium tartrate, ascorbic acid, ethylene glycol, formaldehyde, formic acid, acetaldehyde or glyoxylic acid; The mass ratio of the flaky copper powder to the corrosion inhibitor and the reducing agent is 1:0.01-0.02:0.5-5.

5. The method for preparing the corrosion-resistant flaky silver-coated copper powder according to claim 1 or 2, characterized in that: In step S3, the silver ammonia solution is obtained by adding silver nitrate to water to completely dissolve it, and then adding ammonia water to make the solution transparent; The mass ratio of the flaky copper powder to silver nitrate and the stabilizer is 1:0.1-2:0.05-0.

5.

6. A corrosion-resistant flaky silver-coated copper powder, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 5.

7. An electromagnetic shielding shell based on the corrosion-resistant flaky silver-coated copper powder according to claim 6, characterized in that: The surface of the coating is coated with an electromagnetic shielding water-based coating, which comprises the flaky silver-coated copper powder and a water-based acrylic resin emulsion.

8. The electromagnetic shielding shell according to claim 7, characterized in that: The surface of the flaky silver-coated copper powder is grafted with a silane coupling agent; The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane.

9. The electromagnetic shielding shell according to claim 7 or 8, characterized in that: The aqueous acrylic resin emulsion is prepared by copolymerizing acrylic acid ester monomers to form acrylic acid resin, and then dissolving the copolymerized acrylic acid ester monomers in an aqueous solvent; the acrylic acid ester monomers include acrylic acid ester monomers having a lipophilic group and acrylic acid ester monomers having a hydrophilic group; The acrylate monomer having a lipophilic group is at least one of methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate or 2-ethylhexyl methacrylate, and the acrylate monomer having a hydrophilic group is at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate or polyethylene glycol monomethacrylate.

10. The electromagnetic shielding shell according to claim 9, characterized in that: The acrylic acid ester monomer further comprises an acrylic acid ester monomer having a tertiary amine group, which is at least one of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, tert-butylaminoethyl acrylate or tert-butylaminoethyl methacrylate.

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