A corrosion-resistant flaky silver-coated copper powder, its preparation method, and an electromagnetic shielding housing

Abstract

The present invention discloses a corrosion-resistant flaky silver-coated copper powder, a preparation method thereof, and an electromagnetic shielding housing. The preparation method of the corrosion-resistant flaky silver-coated copper powder includes: adding flaky copper powder and a complexing agent into water and dispersing uniformly to obtain an aqueous copper powder solution; adding the aqueous copper powder solution and a corrosion inhibitor into an aqueous solution containing a reducing agent and dispersing uniformly to obtain a copper powder reduction solution; adding a silver ammonia solution and a stabilizer into the copper powder reduction solution for a reduction reaction to obtain silver-coated copper powder particles, and after precipitation and filtration, the corrosion-resistant flaky silver-coated copper powder is obtained; the above stabilizer is obtained by carrying out a quaternization reaction on 3-dimethylamino-1-propanethiol and sodium 3-bromopropanesulfonate. The present invention reacts flaky copper powder with silver ammonia under specific stabilizer conditions, thereby effectively improving the coating property, oxidation resistance, coating uniformity and compactness of the obtained silver-coated copper powder, and enabling the obtained silver-coated copper powder to be efficiently applied to the electromagnetic shielding housing.

Description

Technical Field

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

[0002] With the rapid development of 5G technology, the number of various wireless communication devices has increased sharply, and the resulting electromagnetic pollution problem has become increasingly serious. Electromagnetic radiation not only interferes with the normal operation of electronic devices 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 research hotspot in electromagnetic shielding materials in recent years.

[0003] The corrosion-resistant flaky silver-coated copper powder is a flaky metal conductive powder with a surface coating treatment. It has both the metallic conductivity of silver and bright colors at the same time. The corrosion-resistant flaky silver-coated copper powder has obvious characteristics: bright colors, strong corrosion resistance, not easy to fade, strong metallic luster and electrical conductivity, and relatively low raw material costs. The corrosion-resistant flaky silver-coated copper powder is widely used in various industrial fields, such as inks, coatings, printing and packaging, dyeing and printing, automobiles, construction, household appliances, and other industrial and decorative fields. In the field of electromagnetic shielding, the miniaturization and integration of 5G devices lead to harsh environments such as high temperatures and complex environments such as coating solvents. The highly corrosion-resistant silver-coated copper can have corrosion resistance in solvent or high-heat application environments, thus meeting the requirements of customers in the electromagnetic shielding field for maintaining a specific hue of silver-coated copper powder.

[0004] The disclosed patent CN118123016A provides a preparation method of uniformly coated silver-coated copper powder and silver-coated copper powder. Although it also relates to a corrosion-resistant silver-coated copper powder, its method requires stannous chloride sensitization. While the process is complex, due to silver ions under certain reduction conditions, a large number of nuclei will also form and grow by themselves to form silver particle powder, rather than all being directionally plated on the copper powder. This often leads to a thin silver layer, which is not enough to block the contact between copper and oxygen, resulting in the problem of copper oxidation. 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 housing. By reacting flaky copper powder with silver ammonia under specific stabilizer conditions, the coating property, antioxidant property, coating uniformity, and denseness of the obtained silver-coated copper powder are effectively improved, and the obtained silver-coated copper powder is efficiently applied to the electromagnetic shielding housing.

[0006] A preparation method of a corrosion-resistant flaky silver-coated copper powder proposed by the present invention includes the following steps:

[0007] S1. Add flaky copper powder and complexing agent into water and disperse evenly to obtain an aqueous copper powder solution;

[0008] S2. Add the aqueous copper powder solution and corrosion inhibitor into an aqueous solution containing a reducing agent and disperse evenly to obtain a copper powder reduction solution;

[0009] S3. Add silver ammonia solution and stabilizer into the copper powder reduction solution for reduction reaction. After filtration, the corrosion-resistant flaky silver-coated copper powder is obtained;

[0010] The above stabilizer is obtained by quaternization reaction of 3-dimethylamino-1-propanethiol and sodium 3-bromopropanesulfonate.

[0011] In the present invention, the structural schematic diagram of the stabilizer is as follows: In the present invention, on the basis of using silver ions to displace or reduce on 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-bromopropanesulfonate is added. This stabilizer is essentially an amphoteric ion surfactant containing a mercapto group. The mercapto group on it can form a Cu-S coordination with the flaky copper powder, so that it adsorbs on the surface of the copper powder. The hydrophobic aliphatic chain group, hydrophilic quaternary ammonium salt group and sulfonate group on it not only enable the copper powder to be evenly dispersed in the solution, but also the presence of the quaternary ammonium salt group can slightly corrode the surface of the copper powder, increasing the adsorption sites on the surface of the copper powder, which helps the subsequent silver ions to be reduced on the surface to form silver nanoparticles. At the same time, the sulfonate group has a certain adsorption and stabilizing effect on silver ions, so that the silver ions will be deposited on the copper surface directionally, forming a self-catalytic silver layer, accelerating the deposition of silver on the surface of the copper powder. Finally, a dense silver coating layer is formed on the surface of the copper powder, realizing the control of the diffusion, adsorption, nucleation and growth of silver ions in the solution, thereby changing the deposition density and morphology of silver on the copper powder. Finally, the obtained silver-coated copper powder has a dense and uniform coating, and the antioxidant performance and conductive effect are significantly improved.

[0012] Preferably, in step S1, before adding the flaky copper powder and the complexing agent into water and dispersing evenly, it further includes adding the flaky copper powder into an ethanol solution for alcohol washing first, and then adding it into an alkaline solution for alkali washing;

[0013] 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%.

[0014] In the present invention, by alcohol washing and alkali washing the flaky copper powder, the organic matter on the surface of the copper powder can be effectively removed, and the surface activity of the copper powder is reduced, providing a good basis for the subsequent silver coating.

[0015] Preferably, in step S1, the complexing agent is at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium aspartic acid diacetate, tetrasodium glutamate diacetate, or trisodium methylglycine diacetate;

[0016] Preferably, the mass ratio of the flaky copper powder to the complexing agent is 1:0.02 - 0.2.

[0017] In the present invention, the complexing agent can form a complex with the enriched silver ammonia ions with a stable structure, thereby effectively stabilizing the silver ions in the solution and generating a dense silver coating layer on the surface of the copper powder.

[0018] 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;

[0019] 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.

[0020] 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 avoids both the rapid reduction of free nano-silver from the silver salt complex solution by a strong reducing agent and the too low activity of a weak reducing agent, which cannot reduce the silver salt complex solution or has too low reduction efficiency.

[0021] Preferably, in step S3, the silver ammonia solution is obtained by completely dissolving silver nitrate in water and then adding ammonia water until the solution becomes transparent;

[0022] Preferably, the mass ratio of the flaky copper powder to silver nitrate and the stabilizer is 1:0.1 - 2:0.05 - 0.5;

[0023] Preferably, the stabilizer further includes ammonium carbonate.

[0024] The present invention also provides a corrosion-resistant flaky silver-coated copper powder prepared by the above preparation method.

[0025] The present invention also provides an electromagnetic shielding housing based on the above corrosion-resistant flaky silver-coated copper powder, the surface of which is coated with an electromagnetic shielding waterborne coating, and the electromagnetic shielding waterborne coating includes the flaky silver-coated copper powder and an aqueous acrylic resin emulsion.

[0026] Preferably, the surface of the flaky silver-coated copper powder is grafted with a silane coupling agent;

[0027] Preferably, the silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane, preferably 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane.

[0028] In the present invention, the surface of the silver-coated copper powder is modified with a silane coupling agent, so that the silver-coated copper powder has better interfacial properties. When used in an electromagnetic shielding waterborne coating, it can exhibit stronger dispersion performance and overall uniformity.

[0029] Preferably, the aqueous acrylic resin emulsion is prepared by copolymerizing acrylate monomers to form an acrylic resin and then dissolving it in an aqueous solvent; the acrylate monomers include acrylates with lipophilic groups and acrylates with hydrophilic groups;

[0030] Preferably, the acrylate monomer with 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 with a hydrophilic group is at least one of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate or polyethylene glycol monomethyl acrylate.

[0031] In the present invention, the acrylic resin formed by copolymerizing the acrylate monomer with a lipophilic group and the acrylate monomer with a hydrophilic group has amphoteric properties. It can coat the silver-coated copper powder, make it uniformly dispersed in the aqueous solvent, and regulate appropriate viscosity and rheological properties, which helps to form better coating adhesion.

[0032] Preferably, the acrylate monomers further include acrylate monomers with tertiary amine groups, preferably at least one of dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, tert-butylaminoethyl acrylate or tert-butylaminoethyl methacrylate.

[0033] In the present invention, after the acrylate monomer with a tertiary amine group participates in the copolymerization, the resulting acrylic resin contains a tertiary amine group, and a quaternization reaction can occur between it and the silver-coated copper powder modified with 3-chloropropyltrimethoxysilane or 3-chloropropyltriethoxysilane as described above. Thereby, it further ensures the uniform dispersion of the flaky silver-coated copper powder in the acrylic resin, so that the resulting coating forms a conductive crosslinked network and the conductive shielding effect is further improved.

[0034] Advantages of the present invention:

[0035] (1)The preparation method of a corrosion-resistant flaky silver-coated copper powder provided by the present invention does not require surface sensitization and activation treatment of copper powder in the early stage. The process steps are simple, easy to operate, and easy to mass-produce.

[0036] (2)The corrosion-resistant flaky silver-coated copper powder provided by the present invention has no obvious elemental silver particles. The silver layer on the powder surface is smooth, has good compactness, high conductivity, and good oxidation resistance, and is suitable for acting as a conductive filler in the field of electronic pastes. Description of the Drawings

[0037] Figure 1 It is the SEM picture of the flaky silver-coated copper powder described in Example 1 of the present invention. Detailed Embodiments

[0038] Next, the present invention details the technical solutions through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not construed as limiting the scope of the present invention.

[0039] Example 1

[0040] This example provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0041] (1)Add 10 g of flaky copper powder (particle size 5 - 10 μm) into 100 mL of ethanol with a volume concentration of 96%. After magnetic stirring for 30 min, filter, add it into 100 mL of sodium hydroxide solution with a mass concentration of 5%. After magnetic stirring for 10 min, filter, and centrifuge and wash with deionized water until neutral to obtain pretreated flaky copper powder;

[0042] (2)Add the pretreated flaky copper powder into 200 mL of deionized water, and then add 0.5 g of disodium ethylenediaminetetraacetate. After magnetic stirring and mixing for 10 min, obtain an aqueous copper powder solution;

[0043] (3)Add 10 g of sodium citrate into 50 mL of deionized water. After magnetic stirring until completely dissolved, obtain a reducing agent solution. Then, successively add 0.1 g of benzotriazole and the aqueous copper powder solution. After magnetic stirring and mixing for 20 min, obtain a copper powder reduction solution;

[0044] (4)Add 3.5 g of silver nitrate into 50 mL of deionized water. After magnetic stirring and mixing for 5 min, add an ammonia water solution with a concentration of 28%. Stir until the solution color becomes transparent to obtain a silver ammonia solution; successively add 1 g of stabilizer and the silver ammonia solution into the copper powder reduction solution. After magnetic stirring and reacting for 30 min, obtain silver-coated copper powder particles. Filter, centrifuge and wash three times with ethanol and water, and dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder;

[0045] The above stabilizer is prepared by the following method:

[0046] Dissolve 1.19 g of 3-dimethylamino-1-propanethiol and 2.26 g of sodium 3-bromopropanesulfonate in 30 mL of ethanol, stir magnetically at 60 °C for 24 h. After completion, remove the residual solvent by distillation under reduced pressure, and recrystallize three times with an ethanol / acetone mixed solution to obtain a white solid, which is the stabilizer; 1 1H NMR (400 MHz, 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).

[0047] Place the flaky silver-coated copper powder prepared in this example under a scanning electron microscope for observation. The results are as Figure 1 shown. It can be seen that the silver coating on the surface of the silver-coated copper powder is uniform, dense, completely wrapped, and has good dispersibility.

[0048] This example also proposes an application of the above flaky silver-coated copper powder in an electromagnetic shielding housing, which specifically includes:

[0049] (1) Add 1 g of γ-aminopropyltriethoxysilane to 20 mL of deionized water, stir magnetically for 10 min, then add 10 g of the above corrosion-resistant flaky silver-coated copper powder, and stir magnetically at 30 °C for 20 min to obtain a flaky silver-coated copper powder dispersion;

[0050] (2) Add 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate, and 0.4 g of 2-hydroxyethyl methacrylate to 20 mL of ethanol, stir and mix evenly under nitrogen protection, then add 0.02 g of azobisisobutyronitrile, heat to 70 °C in a water bath and stir for 4 h. After distilling off the solvent, an acrylic resin is obtained. Add the acrylic resin to water and stir to disperse evenly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt%;

[0051] (3) Add the flaky silver-coated copper powder dispersion to the aqueous acrylic resin emulsion, stir magnetically for 25 min, then add 10 mL of anhydrous ethanol for dilution to obtain an aqueous electromagnetic shielding coating;

[0052] (4) Pour the aqueous electromagnetic shielding coating into a spray gun, evenly spray it on the surface of a plastic substrate used as an electromagnetic shielding housing, and place it in a forced-air drying oven at 120 °C for drying for 30 min to obtain the electromagnetic shielding housing.

[0053] Example 2

[0054] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0055] (1) Add 10 g of flaky copper powder (particle size 5 - 10 μm) to 100 mL of ethanol with a volume concentration of 93%, stir magnetically for 30 min, then filter, add to 100 mL of sodium hydroxide solution with a mass concentration of 1%, stir magnetically for 15 min, then filter, and wash by centrifugation with deionized water until neutral to obtain pretreated flaky copper powder;

[0056] (2) Add the pretreated flaky copper powder to 200 mL of deionized water, then add 1 g of glutamate diacetic acid tetrasodium, stir magnetically and mix for 10 min to obtain an aqueous copper powder solution;

[0057] (3) Add 5 g of sodium tartrate to 50 mL of deionized water, stir magnetically until completely dissolved to obtain a reducing agent solution, then successively add 0.2 g of methylbenzotriazole and the aqueous copper powder solution, stir magnetically and mix for 20 min to obtain a copper powder reduction solution;

[0058] (4) Add 2.5 g of silver nitrate to 50 mL of deionized water, stir magnetically and mix for 5 min, then add ammonia water solution with a concentration of 28%, stir until the solution color becomes transparent to obtain a silver ammonia solution; Add 0.5 g of stabilizer and the silver ammonia solution successively to the copper powder reduction solution, stir magnetically and react for 30 min to obtain silver-coated copper powder particles, filter, wash by centrifugation with ethanol and water three times, and then dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder; The above stabilizer is obtained by referring to the method described in Example 1.

[0059] This embodiment also provides an application of the above flaky silver-coated copper powder in an electromagnetic shielding housing, which specifically includes:

[0060] (1) Add 1 g of γ-glycidyl ether oxypropyltrimethoxysilane to 20 mL of deionized water, stir magnetically and mix for 10 min, then add 10 g of the above corrosion-resistant flaky silver-coated copper powder, and stir magnetically and mix at 30 °C for 20 min to obtain a flaky silver-coated copper powder dispersion;

[0061] (2) Add 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 to 20 mL of ethanol, stir and mix evenly under nitrogen protection, then add 0.02 g of azobisisobutyronitrile, heat to 70 °C in a water bath and stir and react for 4 h, distill off the solvent to obtain an acrylic resin, add the acrylic resin to water, stir and disperse evenly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt%;

[0062] (3) Add the flaky silver-coated copper powder dispersion into the acrylic resin emulsion. After magnetic stirring for 25 min, add 10 mL of absolute ethanol for dilution to obtain an aqueous electromagnetic shielding coating.

[0063] (4) Pour the aqueous electromagnetic shielding coating into a spray gun and evenly spray it on the surface of a plastic substrate used as an electromagnetic shielding housing. Place it in a forced-air drying oven at 120 °C and dry for 30 min to obtain the electromagnetic shielding housing.

[0064] Example 3

[0065] This example presents a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0066] (1) Add 10 g of flaky copper powder (particle size 5 - 10 μm) into 100 mL of ethanol with a volume concentration of 98%. After magnetic stirring for 30 min, filter, add it into 100 mL of sodium hydroxide solution with a mass concentration of 10%. After magnetic stirring for 5 min, filter, and centrifuge and wash with deionized water until neutral to obtain pretreated flaky copper powder.

[0067] (2) Add the pretreated flaky copper powder into 200 mL of deionized water, and then add 2 g of ethylenediaminetetraacetic acid. After magnetic stirring and mixing for 10 min, obtain an aqueous copper powder solution.

[0068] (3) Add 15 g of ascorbic acid into 50 mL of deionized water. After magnetic stirring until completely dissolved, obtain a reducing agent solution. Then, sequentially add 0.1 g of mercaptobenzothiazole and the aqueous copper powder solution, and magnetic stir and mix for 20 min to obtain a copper powder reduction solution.

[0069] (4) Add 4.5 g of silver nitrate into 50 mL of deionized water. After magnetic stirring and mixing for 5 min, add 28% ammonia water solution. Stir until the solution becomes transparent to obtain a silver ammonia solution. Sequentially add 1 g of stabilizer, 1 g of ammonium carbonate, and the silver ammonia solution into the copper powder reduction solution. After magnetic stirring and reacting for 30 min, obtain silver-coated copper powder particles. Filter, centrifuge and wash three times with ethanol and water, and dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder; the above stabilizer is obtained by referring to the method described in Example 1.

[0070] This example also presents an application of the above flaky silver-coated copper powder in an electromagnetic shielding housing, specifically referring to Example 1.

[0071] Example 4

[0072] This example presents a corrosion-resistant flaky silver-coated copper powder, which is obtained by referring to the method described in Example 1.

[0073] This embodiment also provides an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding housing, which specifically includes:

[0074] (1) Add 1 g of γ-aminopropyltriethoxysilane to 20 mL of deionized water, stir magnetically for 10 min, then add 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder, and stir magnetically at 30 °C for 20 min to obtain a dispersion of flaky silver-coated copper powder;

[0075] (2) Add 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate, 0.4 g of 2-hydroxyethyl methacrylate, and 0.2 g of dimethylaminoethyl acrylate to 20 mL of ethanol, stir and mix evenly under nitrogen protection, then add 0.02 g of azobisisobutyronitrile, heat to 70 °C in a water bath and stir for 4 h, distill off the solvent to obtain an acrylic resin, add the acrylic resin to water, stir and disperse evenly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt%;

[0076] (3) Add the dispersion of flaky silver-coated copper powder to the aqueous acrylic resin emulsion, stir magnetically for 25 min, then add 10 mL of absolute ethanol for dilution to obtain an aqueous electromagnetic shielding coating;

[0077] (4) Pour the aqueous electromagnetic shielding coating into a spray gun, spray it evenly on the surface of a plastic substrate used as an electromagnetic shielding housing, and place it in a forced-air drying oven at 120 °C for drying for 30 min to obtain the electromagnetic shielding housing.

[0078] Example 5

[0079] This embodiment provides a corrosion-resistant flaky silver-coated copper powder, which is obtained by referring to the method described in Example 1.

[0080] This embodiment also provides an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding housing, which specifically includes:

[0081] (1) Add 1 g of 3-chloropropyltriethoxysilane to 20 mL of deionized water, stir magnetically for 10 min, then add 10 g of the above-mentioned corrosion-resistant flaky silver-coated copper powder, and stir magnetically at 30 °C for 20 min to obtain a dispersion of flaky silver-coated copper powder;

[0082] (2) Add 0.6 g of methyl methacrylate, 0.4 g of butyl acrylate, 0.4 g of 2-hydroxyethyl methacrylate, and 0.2 g of dimethylaminoethyl acrylate to 20 mL of ethanol, stir and mix evenly under nitrogen protection, then add 0.02 g of azobisisobutyronitrile, heat to 70 °C in a water bath and stir for 4 h, distill off the solvent to obtain an acrylic resin, add the acrylic resin to water, stir and disperse evenly to obtain an aqueous acrylic resin emulsion with a solid content of 30 wt%;

[0083] (3) Add the flaky silver-coated copper powder dispersion into the acrylic resin emulsion. After magnetic stirring for 25 min, add 10 mL of absolute ethanol for dilution to obtain an aqueous electromagnetic shielding coating.

[0084] (4) Pour the aqueous electromagnetic shielding coating into a spray gun and evenly spray it on the surface of a plastic substrate used as an electromagnetic shielding housing. Place it in a forced-air drying oven at 120 °C and dry for 30 min to obtain the electromagnetic shielding housing.

[0085] Comparative Example 1

[0086] This comparative example presents a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0087] (1) Add 10 g of flaky copper powder (particle size 5 - 10 μm) into 100 mL of ethanol with a volume concentration of 96%. After magnetic stirring for 30 min, filter, add it into 100 mL of sodium hydroxide solution with a mass concentration of 5%. After magnetic stirring for 10 min, filter, and centrifuge and wash with deionized water until neutral to obtain pretreated flaky copper powder.

[0088] (2) Add the pretreated flaky copper powder into 200 mL of deionized water, and then add 0.5 g of disodium ethylenediaminetetraacetate. After magnetic stirring and mixing for 10 min, obtain an aqueous copper powder solution.

[0089] (3) Add 10 g of sodium citrate into 50 mL of deionized water. After magnetic stirring until completely dissolved, obtain a reducing agent solution. Then, sequentially add 0.1 g of benzotriazole and the aqueous copper powder solution, and magnetic stir and mix for 20 min to obtain a copper powder reduction solution.

[0090] (4) Add 3.5 g of silver nitrate into 50 mL of deionized water. After magnetic stirring and mixing for 5 min, add an ammonia water solution with a concentration of 28%. Stir until the solution color becomes transparent to obtain a silver ammonia solution. Add the silver ammonia solution into the copper powder reduction solution, and magnetic stir and react for 30 min to obtain silver-coated copper powder particles. Filter, centrifuge and wash three times with ethanol and water, and dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder.

[0091] This comparative example also presents an application of the above flaky silver-coated copper powder in an electromagnetic shielding housing, specifically referring to Example 1.

[0092] Comparative Example 2

[0093] This comparative example presents a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0094] (1) Add 10 g of flaky copper powder (particle size 5 - 10 μm) to 100 mL of ethanol with a volume concentration of 96%. After magnetic stirring for 30 min, filter, add it to 100 mL of sodium hydroxide solution with a mass concentration of 5%. After magnetic stirring for 10 min, filter, and centrifuge and wash with deionized water until neutral to obtain pretreated flaky copper powder;

[0095] (2) Add the pretreated flaky copper powder to 200 mL of deionized water, and then add 0.5 g of disodium ethylenediaminetetraacetate. After magnetic stirring and mixing for 10 min, obtain an aqueous copper powder solution;

[0096] (3) Add 10 g of sodium citrate to 50 mL of deionized water. After magnetic stirring until completely dissolved, obtain a reducing agent solution. Then, sequentially add 0.1 g of benzotriazole and the aqueous copper powder solution, and after magnetic stirring and mixing for 20 min, obtain a copper powder reduction solution;

[0097] (4) Add 3.5 g of silver nitrate to 50 mL of deionized water. After magnetic stirring and mixing for 5 min, add 28% ammonia water solution. Stir until the solution becomes transparent to obtain a silver ammonia solution; sequentially add 1 g of ammonium carbonate and the silver ammonia solution to the copper powder reduction solution. After magnetic stirring and reacting for 30 min, obtain silver-coated copper powder particles. Filter, centrifuge and wash three times with ethanol and water, and dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder.

[0098] This comparative example also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding housing, specifically referring to Example 1.

[0099] Comparative Example 3

[0100] This comparative example proposes a corrosion-resistant flaky silver-coated copper powder, which is prepared by the following method:

[0101] (1) Add 10 g of flaky copper powder (particle size 5 - 10 μm) to 100 mL of ethanol with a volume concentration of 96%. After magnetic stirring for 30 min, filter, add it to 100 mL of sodium hydroxide solution with a mass concentration of 5%. After magnetic stirring for 10 min, filter, and centrifuge and wash with deionized water until neutral to obtain pretreated flaky copper powder;

[0102] (2) Add the pretreated flaky copper powder to 200 mL of deionized water, and then add 0.5 g of disodium ethylenediaminetetraacetate. After magnetic stirring and mixing for 10 min, obtain an aqueous copper powder solution;

[0103] (3) Add 10 g of sodium citrate to 50 mL of deionized water. After magnetic stirring until completely dissolved, obtain a reducing agent solution. Then, sequentially add 0.1 g of benzotriazole and the aqueous copper powder solution, and after magnetic stirring and mixing for 20 min, obtain a copper powder reduction solution;

[0104] (4) Add 3.5 g of silver nitrate to 50 mL of deionized water. After magnetic stirring and mixing for 5 min, add an ammonia water solution with a concentration of 28%. Stir until the color of the solution becomes transparent to obtain a silver ammonia solution. Add 1 g of sodium dodecyl sulfonate and the silver ammonia solution to the copper powder reduction solution. After magnetic stirring and reacting for 30 min, silver-coated copper powder particles are obtained. Filter, wash three times by centrifugation with ethanol and water, and then dry in a vacuum drying oven at 60 °C to obtain the corrosion-resistant flaky silver-coated copper powder.

[0105] This comparative example also proposes an application of the above-mentioned flaky silver-coated copper powder in an electromagnetic shielding housing, with specific reference to Example 1.

[0106] Use a four-probe resistivity meter to measure the sheet resistance and resistivity of the coating film on the electromagnetic shielding housing prepared in the examples and comparative examples (the size specification of the film-forming sample is 10 cm × 10 cm × 50 μm), and conduct the measurement again after 30 days of placement. Use a vector network analyzer connected to two X-band waveguides to measure the electromagnetic shielding performance of the coating film on the electromagnetic shielding housing prepared in the examples and comparative examples by the waveguide method at room temperature, in the X-band (8.2 - 18.0 GHz) frequency band, and with a frequency bandwidth of 1 kHz. The test results are shown in Table 1.

[0107]

[0108] As can be seen from Table 1 above, the flaky silver-coated copper powder prepared in the examples has good electrical conductivity and electromagnetic shielding performance after forming a film in the waterborne electromagnetic shielding coating. The change in the resistivity value after 30 days of natural placement is minimal, indicating that the flaky silver-coated copper powder prepared in the examples 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 in the present invention makes the silver have a dense coating effect on the surface of the copper powder, and the obtained flaky silver-coated copper powder has excellent electrical conductivity and antioxidant properties. Comparing Example 1, Example 4 with Example 5 shows that the flaky silver-coated copper powder modified with a specific silane coupling agent and placed in a specific waterborne acrylic resin emulsion system will further improve the electrical conductivity and electromagnetic shielding performance.

[0109] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within 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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