A method for producing high-efficiency ultrafine silver powder

Abstract

This invention discloses a method for producing high-efficiency ultrafine silver powder, comprising the following steps: S1, dissolving silver: adding No. 1 silver ingot to a reaction vessel, and adding 65-68% concentrated nitric acid at a rate of 300L / h, with a total amount of concentrated nitric acid added of 1500-2000L, to obtain a silver solution; S2, removing impurities from the silver solution; S4, preparing a reducing solution; S5, preparing a base solution; S6, preparing a modifier solution; S7, reducing to prepare ultrafine silver powder; S8, washing the ultrafine silver powder; S9, coating the ultrafine silver powder with a surface: adding the modifier solution to the filtered ultrafine silver powder, and dispersing it in an emulsifier at a speed of 3000-8000rpm for 5-50min to obtain a surface-coated ultrafine silver powder; S10, drying the ultrafine silver powder: placing the surface-coated ultrafine silver powder in an oven and drying it at 50-80℃ until the moisture content is less than 0.1%; S11, crushing and sieving the dried silver powder to obtain the ultrafine silver powder product.

Description

Technical Field

[0001] This invention relates to the technical field of metal powder preparation methods for the electronics industry, and particularly to a method for producing high-efficiency ultrafine silver powder. Background Technology

[0002] Ultrafine silver powder, as a common metal powder, has excellent electrical and thermal conductivity. As the most critical raw material for photovoltaic silver paste, photovoltaic silver powder is the core to ensure the stable and reliable performance of silver paste.

[0003] Traditional ultrafine silver powder production typically uses silver nitrate crystals as the raw material. The silver nitrate crystals are dissolved to form a solution, which is then reduced in a liquid phase to produce ultrafine silver powder. However, in the production process of silver nitrate crystals, after the silver nitrate solution is purified, it still needs to undergo evaporation and crystallization to form the crystals. The evaporation and crystallization processes remove water from the solution, and a large amount of water needs to be added to dissolve the silver nitrate crystals during use. This process of removal and addition results in significant waste of time, energy, and resources. Therefore, developing a more efficient method for producing ultrafine silver powder is essential. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a highly efficient method for producing ultrafine silver powder.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A method for producing high-efficiency ultrafine silver powder includes the following steps: S1. Silver dissolution: Add No. 1 silver ingot to the reaction vessel, and add 65-68% concentrated nitric acid at a rate of 300L / h, with a total amount of concentrated nitric acid added of 1500-2000L; raise the temperature of the reaction system to 50-60℃, and react until no more nitrogen oxides are generated in the system to obtain silver solution; S2. Silver solution purification: The silver solution is pumped into the purification vessel, pure water is added, and the pH of the solution is adjusted to 5-7; heating is started while stirring, and the temperature is raised to 50-70℃ and kept at this temperature for 2-4 hours. The solution is then filtered to obtain the purified silver solution. S3. Silver nitrate solution concentration adjustment: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 100-200 g / L to obtain a silver nitrate solution. S4. Preparation of reducing solution: Take the reducing agent, add deionized water and stir to dissolve, prepare a reducing agent solution with a concentration of 10-100 g / L, add sodium hydroxide or potassium hydroxide, adjust the pH value to 11-14, keep the temperature at 30-50℃, and filter to obtain the reducing solution. S5. Preparation of the base solution: Take the dispersant, add deionized water and stir to dissolve it, prepare a base solution with a concentration of 0.1-1.0 g / L, keep the temperature at 30-50℃, and filter to obtain the dispersant base solution; S6. Preparation of modifier solution: Take the modifier, add anhydrous ethanol and stir to dissolve, prepare a modifier solution with a concentration of 1-10 g / L, and keep the temperature at 30-50℃. S7. Preparation of ultrafine silver powder by reduction: Silver nitrate solution and reducing liquid are added to the base liquid in a co-current manner to prepare ultrafine silver powder by reduction. The addition time is 10-50 min and the stirring speed is 100 rpm. S8. Washing the ultrafine silver powder: The solution prepared in step S7 is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is less than 15µΩ / cm, and then filtered until the moisture content in the powder is less than 50%. S9. Surface-coated ultrafine silver powder: Add a modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at a speed of 3000-8000 rpm for 5-50 minutes to obtain surface-coated ultrafine silver powder. S10. Drying the ultrafine silver powder: Place the surface-coated ultrafine silver powder into an oven and dry it at 50-80℃ until the moisture content is less than 0.1%; S11. The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product.

[0006] In step S2, the solution is filtered using a microporous filter with a pore size of 0.1–0.5 μm.

[0007] In step S4, the reducing agent is formaldehyde, hydrazine hydrate, glucose, ascorbic acid, triethanolamine, or glycerol.

[0008] In step S4, a reduction solution is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0009] In step S5, the dispersant is PEG, PVA, or PVP.

[0010] In step S5, the dispersant base liquid is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0011] In step S6, the modifier is a fatty acid, a fatty amine, or a fatty alcohol.

[0012] The fatty acid is selected from stearic acid, oleic acid, lauric acid, or hexadecanoic acid; the fatty amine is oleylamine; and the fatty alcohol is hexadecyl alcohol.

[0013] The beneficial effects of this invention are: this invention overcomes the waste of time, energy and resources caused by directly using silver nitrate crystals for production, and efficiently produces ultrafine silver powder. This silver powder has good dispersibility and can be applied to the front grid lines of photovoltaic cells. Attached Figure Description

[0014] Figure 1 The image shown is a scanning electron microscope image of the product prepared in Example 1 of this invention.

[0015] Figure 2 This is a scanning electron microscope image of the product prepared in Example 2 of the present invention.

[0016] Figure 3 This is a scanning electron microscope image of the product prepared in Example 3 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0018] Example 1: (1) Silver dissolution: Add 2000 kg of No. 1 silver ingot to a 4 m3 reactor, add 65% concentrated nitric acid at a rate of 300 L / h, and the total amount of concentrated nitric acid added is 2000 L; raise the temperature of the reaction system to 50 °C, and react until no more nitrogen oxides are generated in the system to obtain silver solution.

[0019] (2) Silver solution purification: The silver solution was pumped into a 6m3 purification vessel, pure water was added, and the pH of the solution was adjusted to 5. The heating was turned on while stirring, and the temperature was raised to 50°C and kept for 2 hours. The solution was filtered using a 0.1μm microporous filter to obtain the silver purified solution.

[0020] (3) Adjustment of silver nitrate solution concentration: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 100 g / L to obtain silver nitrate solution.

[0021] (4) Preparation of reducing solution: Weigh 25kg of ascorbic acid, add 200L of deionized water and stir to dissolve, prepare a reducing agent solution, add 500g of sodium hydroxide, adjust the pH value to 11, keep the temperature at 30℃, and filter with a 0.1μm ultrafiltration membrane to obtain the reducing solution; (5) Preparation of the base solution: Weigh 0.2 kg of dispersant PEG2000, add 400 L of deionized water and stir to dissolve, prepare a solution with a concentration of 0.5 g / L, keep the temperature at 30 °C, and filter with a 0.1 μm ultrafiltration membrane to obtain the dispersant base solution; (6) Preparation of modifier solution: Weigh 10g stearic acid, add 10L anhydrous ethanol and stir to dissolve, prepare a 1g / L modifier solution, and keep the temperature constant to 30℃; (7) Preparation of ultrafine silver powder by reduction: The 400L silver nitrate solution and 200L reducing solution are added to the bottom liquid in parallel to prepare ultrafine silver powder by reduction. The addition time is 20min and the stirring speed is 100rpm. (8) Washing the ultrafine silver powder: The reduced solution is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is 14µΩ / cm, and filtered until the moisture content in the powder is 49%; (9) Surface-coated ultrafine silver powder: Add modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at 3000 rpm for 5 min to obtain surface-coated ultrafine silver powder; (10) Drying the ultrafine silver powder: Place the ultrafine silver powder coated on the surface into an oven and dry it at 50°C until the moisture content is 0.08%.

[0022] (11) The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product, the scanning electron microscope image of which is shown below. Figure 1 As shown.

[0023] Example 2: (1) Silver dissolution: Add 2000 kg of No. 1 silver ingot to a 4 m3 reactor, add 67% concentrated nitric acid at a rate of 300 L / h, and the total amount of concentrated nitric acid added is 1800 L; raise the temperature of the reaction system to 55 °C, and react until no more nitrogen oxides are generated in the system to obtain silver solution.

[0024] (2) Silver solution purification: The silver solution was pumped into a 6m3 purification vessel, pure water was added, and the pH of the solution was adjusted to 6. The heating was turned on while stirring, and the temperature was raised to 60℃ and kept for 3h. The solution was filtered using a 0.2μm microporous filter to obtain the silver purified solution.

[0025] (3) Adjustment of silver nitrate solution concentration: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 150 g / L to obtain silver nitrate solution.

[0026] (4) Preparation of reducing solution: Weigh a certain amount of 10kg of 80% hydrazine hydrate, add 300L of deionized water and stir to prepare a reducing agent solution with a reducing agent of 26g / L. Add 100g of sodium hydroxide, adjust the pH value to 13, keep the temperature at 40℃, and filter with a 0.1μm ultrafiltration membrane to obtain an alkaline solution. (5) Preparation of the base solution: Weigh 400g PVA, add 400L of deionized water and stir to dissolve, prepare a dispersant solution with a reducing agent of 1.0g / L, keep the temperature at 40℃, and filter with a 0.1μm ultrafiltration membrane to obtain the dispersant base solution; (6) Preparation of modifier solution: Weigh 20g of oleic acid, add 5L of anhydrous ethanol and stir to dissolve, prepare a modifier solution with a reducing agent of 4g / L, and keep the temperature constant to 40℃; (7) Preparation of ultrafine silver powder by reduction: The 260L silver nitrate solution and 300L reducing solution are added to the bottom liquid in parallel to prepare ultrafine silver powder by reduction. The addition time is 40min and the stirring speed is 100rpm. (8) Washing ultrafine silver powder: The reduced solution is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is 12µΩ / cm, and filtered until the moisture content in the powder is 48%; (9) Surface-coated ultrafine silver powder: Add modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at 5000 rpm for 10 min to obtain surface-coated ultrafine silver powder; (10) Drying the ultrafine silver powder: Place the ultrafine silver powder coated on the surface into an oven and dry it at 70°C until the moisture content is 0.09%.

[0027] (11) The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product, the scanning electron microscope image of which is shown below. Figure 2 As shown.

[0028] Example 3: (1) Silver dissolution: Add 2000 kg of No. 1 silver ingot to a 4 m3 reactor, add 68% concentrated nitric acid at a rate of 300 L / h, and the total amount of concentrated nitric acid added is 1500 L; raise the temperature of the reaction system to 60 °C, and react until no more nitrogen oxides are generated in the system to obtain silver solution.

[0029] (2) Silver solution purification: The silver solution was pumped into a 6m3 purification vessel, pure water was added, and the pH of the solution was adjusted to 7. The heating was turned on while stirring, and the temperature was raised to 70°C and kept for 4 hours. The solution was filtered using a 0.5μm microporous filter to obtain the silver purified solution.

[0030] (3) Adjustment of silver nitrate solution concentration: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 200 g / L to obtain silver nitrate solution.

[0031] (4) Preparation of reducing solution: Weigh 10 kg of triethanolamine, add 100 L of a certain amount of deionized water and stir to dissolve, prepare a reducing agent solution with a reducing agent concentration of 100 g / L, add 10 g of potassium hydroxide, adjust the pH value to 14, keep the temperature at 50 °C, and filter with a 0.1 μm ultrafiltration membrane to obtain an alkaline solution. (5) Preparation of the base solution: Weigh 4 kg PVP, add 400 L of deionized water and stir to dissolve, prepare a dispersant solution with a concentration of 1.0 g / L, keep the temperature at 50 °C, and filter with a 0.1 μm ultrafiltration membrane to obtain the dispersant base solution; (6) Preparation of modifier solution: Weigh 20g of cetyl alcohol, add 2L of anhydrous ethanol and stir to dissolve, prepare a modifier solution with a concentration of 10g / L, and keep the temperature constant to 50℃; (7) Preparation of ultrafine silver powder by reduction: 200L silver nitrate solution and 100L reducing solution are added to the bottom liquid in parallel to prepare ultrafine silver powder by reduction. The addition time is 10min and the stirring speed is 100rpm. (8) Washing ultrafine silver powder: The reduced solution is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is 12µΩ / cm, and filtered until the moisture content in the powder is 47%; (9) Surface-coated ultrafine silver powder: Add modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at 6000 rpm for 5 min to obtain surface-coated ultrafine silver powder; (10) Drying the ultrafine silver powder: Place the ultrafine silver powder coated on the surface into an oven and dry it at 80°C until the moisture content is 0.07%.

[0032] (11) The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product, the scanning electron microscope image of which is shown below. Figure 3 As shown.

[0033] .

[0034] Example 4 A method for producing high-efficiency ultrafine silver powder includes the following steps: S1. Silver dissolution: Add No. 1 silver ingot to the reaction vessel, and add 65% concentrated nitric acid at a rate of 300L / h, with a total amount of concentrated nitric acid added of 1500L; raise the temperature of the reaction system to 50℃, and react until no more nitrogen oxides are generated in the system to obtain silver solution; S2. Silver solution purification: The silver solution is pumped into the purification vessel, pure water is added, and the pH of the solution is adjusted to 5. The heating is turned on while stirring, heated to 50°C, and kept at this temperature for 2 hours. The solution is then filtered to obtain the purified silver solution. S3. Silver nitrate solution concentration adjustment: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 100g / L to obtain a silver nitrate solution. S4. Preparation of reducing solution: Take the reducing agent, add deionized water and stir to dissolve, prepare a reducing agent solution with a concentration of 10g / L, add sodium hydroxide or potassium hydroxide, adjust the pH value to 11, keep the temperature at 30℃, and filter to obtain the reducing solution. S5. Preparation of the base solution: Take the dispersant, add deionized water and stir to dissolve it, prepare a base solution with a concentration of 0.1 g / L, keep the temperature at 30℃, and filter to obtain the dispersant base solution; S6. Preparation of modifier solution: Take the modifier, add anhydrous ethanol and stir to dissolve, prepare a modifier solution with a concentration of 1g / L, and keep the temperature constant to 30℃. S7. Preparation of ultrafine silver powder by reduction: Silver nitrate solution and reducing liquid are added to the base liquid in a co-current manner to prepare ultrafine silver powder by reduction. The addition time is 10 min and the stirring speed is 100 rpm. S8. Washing the ultrafine silver powder: The solution prepared in step S7 is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is 12µΩ / cm, and then filtered until the moisture content in the powder is 48%. S9. Surface-coated ultrafine silver powder: Add a modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at 3000 rpm for 5 minutes to obtain surface-coated ultrafine silver powder. S10. Drying the ultrafine silver powder: Place the surface-coated ultrafine silver powder into an oven and dry it at 50°C until the moisture content is less than 0.1%; S11. The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product.

[0035] In step S2, the solution is filtered using a 0.1 μm microporous filter.

[0036] In step S4, the reducing agent is formaldehyde.

[0037] In step S4, a reduction solution is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0038] In step S5, the dispersant is PEG.

[0039] In step S5, the dispersant base liquid is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0040] In step S6, the modifier is lauric acid.

[0041] Example 5 A method for producing high-efficiency ultrafine silver powder includes the following steps: S1. Silver dissolution: Add No. 1 silver ingot to the reaction vessel, and add 68% concentrated nitric acid at a rate of 300L / h, with a total amount of concentrated nitric acid added of 2000L; raise the temperature of the reaction system to 60℃, and react until no more nitrogen oxides are generated in the system to obtain silver solution; S2. Silver solution purification: The silver solution is pumped into the purification vessel, pure water is added, and the pH of the solution is adjusted to 7. The heating is turned on while stirring, heated to 70°C, and kept at this temperature for 4 hours. The solution is then filtered to obtain the purified silver solution. S3. Silver nitrate solution concentration adjustment: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 200g / L to obtain a silver nitrate solution. S4. Preparation of reducing solution: Take the reducing agent, add deionized water and stir to dissolve, prepare a reducing agent solution with a concentration of 100g / L, add sodium hydroxide or potassium hydroxide, adjust the pH value to 14, keep the temperature at 50℃, and filter to obtain the reducing solution. S5. Preparation of the base solution: Take the dispersant, add deionized water and stir to dissolve it, prepare a base solution with a concentration of 1.0 g / L, keep the temperature at 50℃, and filter to obtain the dispersant base solution; S6. Preparation of modifier solution: Take the modifier, add anhydrous ethanol and stir to dissolve, prepare a modifier solution with a concentration of 10g / L, and keep the temperature constant to 50℃. S7. Preparation of ultrafine silver powder by reduction: Silver nitrate solution and reducing liquid are added to the base liquid in a co-current manner to prepare ultrafine silver powder by reduction. The addition time is 50 min and the stirring speed is 100 rpm. S8. Washing the ultrafine silver powder: The solution prepared in step S7 is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is 14µΩ / cm, and then filtered until the moisture content in the powder is 48%. S9. Surface-coated ultrafine silver powder: Add a modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at 8000 rpm for 50 min to obtain surface-coated ultrafine silver powder. S10. Drying the ultrafine silver powder: Place the surface-coated ultrafine silver powder into an oven and dry it at 80°C until the moisture content is less than 0.1%; S11. The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product.

[0042] In step S2, the solution is filtered using a 0.5 μm microporous filter.

[0043] In step S4, the reducing agent is glucose.

[0044] In step S4, a reduction solution is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0045] In step S5, the dispersant is PEG.

[0046] In step S5, the dispersant base liquid is obtained by filtration using a 0.1 μm ultrafiltration membrane.

[0047] In step S6, the modifier is oleylamine.

[0048] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for producing high-efficiency ultrafine silver powder, characterized in that, Includes the following steps: S1. Silver dissolution: Add No. 1 silver ingot to the reaction vessel, and add 65-68% concentrated nitric acid at a rate of 300L / h, with a total amount of concentrated nitric acid added of 1500-2000L; raise the temperature of the reaction system to 50-60℃, and react until no more nitrogen oxides are generated in the system to obtain silver solution; S2. Silver solution purification: The silver solution is pumped into the purification vessel, pure water is added, and the pH of the solution is adjusted to 5-7; heating is started while stirring, and the temperature is raised to 50-70℃ and kept at this temperature for 2-4 hours. The solution is then filtered to obtain the purified silver solution. S3. Silver nitrate solution concentration adjustment: Add pure water to the silver purification solution to adjust the silver nitrate concentration to 100-200 g / L to obtain a silver nitrate solution. S4. Preparation of reducing solution: Take the reducing agent, add deionized water and stir to dissolve, prepare a reducing agent solution with a concentration of 10-100 g / L, add sodium hydroxide or potassium hydroxide, adjust the pH value to 11-14, keep the temperature at 30-50℃, and filter to obtain the reducing solution. S5. Preparation of the base solution: Take the dispersant, add deionized water and stir to dissolve it, prepare a base solution with a concentration of 0.1-1.0 g / L, keep the temperature at 30-50℃, and filter to obtain the dispersant base solution; S6. Preparation of modifier solution: Take the modifier, add anhydrous ethanol and stir to dissolve, prepare a modifier solution with a concentration of 1-10 g / L, and keep the temperature at 30-50℃. S7. Preparation of ultrafine silver powder by reduction: Silver nitrate solution and reducing liquid are added to the base liquid in a co-current manner to prepare ultrafine silver powder by reduction. The addition time is 10-50 min and the stirring speed is 100 rpm. S8. Washing the ultrafine silver powder: The solution prepared in step S7 is filtered to separate the ultrafine silver powder solid, washed with deionized water until the conductivity of the washing solution is less than 15µΩ / cm, and then filtered until the moisture content in the powder is less than 50%. S9. Surface-coated ultrafine silver powder: Add a modifier solution to the filtered ultrafine silver powder and disperse it in an emulsifier at a speed of 3000-8000 rpm for 5-50 minutes to obtain surface-coated ultrafine silver powder. S10. Drying the ultrafine silver powder: Place the surface-coated ultrafine silver powder into an oven and dry it at 50-80℃ until the moisture content is less than 0.1%; S11. The dried silver powder is crushed and sieved to obtain an ultrafine silver powder product.

2. The method for producing high-efficiency ultrafine silver powder according to claim 1, characterized in that, In step S2, the solution is filtered using a microporous filter with a pore size of 0.1–0.5 μm.

3. The method for producing high-efficiency ultrafine silver powder according to claim 2, characterized in that, In step S4, the reducing agent is formaldehyde, hydrazine hydrate, glucose, ascorbic acid, triethanolamine, or glycerol.

4. The method for producing high-efficiency ultrafine silver powder according to claim 1, characterized in that, In step S4, a reducing solution is obtained by filtration using a 0.1 μm ultrafiltration membrane.

5. The method for producing high-efficiency ultrafine silver powder according to claim 1, characterized in that, In step S5, the dispersant is PEG, PVA, or PVP.

6. The method for producing high-efficiency ultrafine silver powder according to claim 1, characterized in that, In step S5, the dispersant base liquid is obtained by filtration using a 0.1 μm ultrafiltration membrane.

7. The method for producing high-efficiency ultrafine silver powder according to claim 1, characterized in that, In step S6, the modifier is a fatty acid, a fatty amine, or a fatty alcohol.

8. The method for producing high-efficiency ultrafine silver powder according to claim 7, characterized in that, The fatty acids are selected from stearic acid, oleic acid, lauric acid, or hexadecanoic acid; the fatty amine is oleylamine; and the fatty alcohol is hexadecyl alcohol.

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