Silver powder and large-scale production method thereof

Abstract

The invention discloses silver powder and a large-scale production method thereof, and belongs to the technical field of silver powder preparation. The production method comprises the following steps: preparing a part of dispersing agent solution and a part of reducing agent solution into a base solution; simultaneously adding the silver source solution and the residual reducing agent solution into the base solution through a first flow path and a second flow path respectively, wherein the total adding time of the silver source solution and the residual reducing agent solution is t1; after the adding duration of the silver source solution and the residual reducing agent solution is t2, the residual dispersing agent solution is added through a third flow path, and the total adding duration of the residual dispersing agent solution is t3; after the silver source solution is completely added, adding a surfactant solution; wherein t1 = t2 + t3. According to the method, the problems of silver powder particle aggregation and obvious particle size in the production process can be effectively avoided, and stable and large-scale production of the superfine silver powder can be achieved under the condition that the high yield is kept. The obtained silver powder is narrow in particle size distribution, consistent in morphology and good in quality.

Description

Technical Field

[0001] The invention relates to the technical field of silver powder preparation, and in particular to silver powder and a large-scale production method thereof. Background Art

[0002] The research on the synthesis and stable amplification of ultrafine silver powder involves multiple fields such as nanomaterials, precious metal chemistry, and materials science. In particular, nano-scale silver powder has important application value in many fields due to its high specific surface area, conductivity, antibacterial properties and unique optical properties. For example, silver nanoparticles have good conductivity and can be widely used in conductive inks and conductive coatings. In addition, silver powder also plays an important role in antibacterial agents and antiviral coatings. With the development of nanotechnology, the smaller the particle size of silver powder, the more significant its performance. For example, in the field of catalysis, silver nanoparticles exhibit higher catalytic activity due to their high specific surface area. In addition, silver nanoparticles also have important applications in the fields of chemical and biological sensors, especially in surface enhanced Raman scattering (SERS) technology, where silver nanoparticles can greatly enhance optical signals and improve detection sensitivity.

[0003] However, there are great technical challenges in synthesizing high-quality ultrafine silver powder and being able to achieve stable amplification without affecting its performance. At present, the preparation of silver powder in small-scale laboratories can usually achieve a high reduction efficiency, but when it comes to industrial production, the yield tends to decrease. Normally, the reduction efficiency of silver ions in the laboratory can reach more than 90%, but in industrial production, due to limitations in equipment, environmental conditions, reaction efficiency, etc., the yield may drop below 70%.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide a silver powder and a large-scale production method thereof to solve or improve the above technical problems.

[0006] The present invention can be implemented like this:

[0007] In a first aspect, the present invention provides a large-scale production method of silver powder, comprising the following steps: preparing a base liquid with a part of a dispersant solution and a part of a reducing agent solution; adding a silver source solution and a remaining reducing agent solution to the base liquid simultaneously through a first flow path and a second flow path respectively, and the total addition time of the silver source solution and the remaining reducing agent solution is t1; after the silver source solution and the remaining reducing agent solution are added for a time of t2, adding the remaining dispersant solution through a third flow path, and the total addition time of the remaining dispersant solution is t3; after the silver source solution is completely added, adding a surfactant solution immediately;

[0008] Wherein, t1=t2+t3, t1 is 5min to 30min; and / or, t2 is 2min to 10min; and / or, t3 is 2min to 10min;

[0009] The entire production process is carried out at 5°C to 45°C; the stirring speed during the entire production process is 250rpm to 600rpm.

[0010] In an optional embodiment, when the volume of the reaction container used for production is less than 100 L, the stirring speed is 300 rpm to 600 rpm; when the volume of the reaction container used for production is ≥100 L, the stirring speed is 250 rpm to 350 rpm.

[0011] In an optional embodiment, the silver source in the silver source solution includes at least one of silver nitrate and silver acetate.

[0012] In an optional embodiment, the concentration of silver ions in the silver source solution is 1.8 mol / L to 2.2 mol / L, and the content of silver source in the silver source solution is 28 wt % to 32 wt %.

[0013] In an optional embodiment, the reducing agent in the reducing agent solution includes at least one of ascorbic acid, sodium ascorbate, glucose and hydrazine hydrate.

[0014] In an optional embodiment, the content of the reducing agent in the reducing agent solution is 13 wt % to 17 wt %.

[0015] In an optional embodiment, when the reducing agent is ascorbic acid, the content of ascorbic acid in the reducing agent solution is 13wt% to 17wt%; when the reducing agent is sodium ascorbate, the content of sodium ascorbate in the reducing agent solution is 13wt% to 13.2wt%.

[0016] In an optional embodiment, the amount of the reducing agent solution is not less than the theoretical amount for completely reducing the silver source in the silver source solution into silver powder.

[0017] In an alternative embodiment, the dispersant in the dispersant solution comprises PVP-K30.

[0018] In an optional embodiment, the content of the dispersant in the dispersant solution is 5 wt % to 30 wt %.

[0019] In an optional embodiment, the total amount of the dispersant is 5 wt % to 25 wt % of the silver powder.

[0020] In an alternative embodiment, the surfactant in the surfactant solution includes at least one of stearic acid, sodium oleate and carboxylate.

[0021] In an optional embodiment, the content of the surfactant in the surfactant solution is 1.0 wt% to 10.0 wt%.

[0022] In an optional embodiment, the total amount of the surfactant is 1 wt‰ to 1 wt % of the silver powder.

[0023] In a second aspect, the present invention provides a silver powder produced by the large-scale production method of any one of the aforementioned embodiments.

[0024] In an optional embodiment, the silver powder has a D 50 It is 500nm~3μm, and the span of silver powder is less than 1.5.

[0025] In an optional embodiment, the silver powder is spherical or quasi-spherical, and the specific surface area of ​​the silver powder is 0.5 m 2 / g~1.5m 2 / g.

[0026] The beneficial effects of the present invention include:

[0027] The present invention can coat the silver powder particles by adding the dispersant at the beginning of the reaction, effectively preventing direct contact between the silver powder particles, thereby avoiding the occurrence of agglomeration. Combined with the optimization and fine control of the reaction conditions (such as temperature, stirring speed, and reaction time), the uniform amplification of the silver powder is achieved, ensuring that its particle size distribution is narrow and the morphology is consistent. Among them, within a suitable range, the faster the stirring speed, the smaller the particle size of the silver powder produced; the lower the reaction temperature, the smaller the particle size of the silver powder produced; the reaction time is greater than 5min, which can improve the problem of coexistence of large and small particles and narrow the particle size distribution. This method can effectively avoid the problems of silver powder particle agglomeration and obvious large and small particles in the production process, and can achieve stable amplification of ultrafine silver powder under the condition of maintaining a high yield. The obtained silver powder has a narrow particle size distribution, consistent morphology, a small specific surface area, and good quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a SEM image of the silver powder prepared in Example 1;

[0030] Figure 2 This is a SEM image of the silver powder prepared in Example 2;

[0031] Figure 3 This is a SEM image of the silver powder prepared in Example 5;

[0032] Figure 4 This is a SEM image of the silver powder prepared in Comparative Example 3;

[0033] Figure 5 This is a SEM image of the silver powder prepared in Comparative Example 5;

[0034] Figure 6 This is the SEM image of the silver powder prepared in Comparative Example 6. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0036] The silver powder and the large-scale production method thereof provided by the present invention are specifically described below.

[0037] The present invention provides a large-scale production method of silver powder, comprising the following steps:

[0038] S1: preparing a base solution by mixing part of the dispersant solution and part of the reducing agent solution;

[0039] S2: adding the silver source solution and the remaining reducing agent solution to the base solution through the first flow path and the second flow path respectively, and the total adding time of the silver source solution and the remaining reducing agent solution is t1;

[0040] S3: After the silver source solution and the remaining reducing agent solution are added for a time period of t2, the remaining dispersant solution is added through the third flow path, and the total addition time of the remaining dispersant solution is t3; t1=t2+t3.

[0041] S4: After the silver source solution is completely added, the surfactant solution is added immediately.

[0042] It should be noted that in the above production process, the silver source solution and the remaining reducing agent solution are added and added at the same time (that is, the flow rates of the silver source solution and the remaining reducing agent solution are different), and when the silver source solution is added, the remaining dispersant solution is also added at the same time. During the entire material addition process, the addition flow rate of the same material remains consistent from beginning to end.

[0043] In some optional implementations, t1 may be 5 min to 30 min, such as 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, or may be other values ​​within the range of 5 min to 30 min.

[0044] In some optional implementations, t2 may be 2 min to 10 min, such as 2 min, 4 min, 6 min, 8 min or 10 min, etc., or may be other values ​​within the range of 2 min to 10 min.

[0045] In some optional implementations, t3 may be 2 min to 10 min, such as 2 min, 4 min, 6 min, 8 min or 10 min, etc., or may be other values ​​within the range of 2 min to 10 min.

[0046] In some optional implementations, 1 / 15t1≤t2≤2 / 3t1. In some typical implementations, t2=1 / 2t1, that is, t2=t3.

[0047] By controlling t2 and t3 within the above range, the stability of scale-up production can be ensured.

[0048] In some optional embodiments, the entire production process can be carried out at 5° C. to 45° C. In other words, the reaction temperature can be 5° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C. or 45° C., or other values ​​within the range of 5° C. to 45° C.

[0049] In some optional embodiments, the stirring speed during the entire production process can be 250 rpm to 600 rpm. In other words, the stirring speed of the reaction can be 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm or 600 rpm, etc., or other values ​​within the range of 250 rpm to 600 rpm.

[0050] In some more specific embodiments, when the volume of the reaction container used for production is less than 100 L, the stirring speed is preferably set to 300 rpm to 600 rpm; when the volume of the reaction container used for production is ≥100 L, the stirring speed is preferably set to 250 rpm to 350 rpm.

[0051] In some optional embodiments, the silver source in the silver source solution may illustratively but not limitatively include at least one of silver nitrate and silver acetate.

[0052] The concentration of silver ions in the silver source solution can be 1.8mol / L to 2.2mol / L, such as 1.8mol / L, 1.9mol / L, 2.0mol / L, 2.1mol / L or 2.2mol / L, or other values ​​within the range of 1.8mol / L to 2.2mol / L.

[0053] The content of the silver source in the silver source solution can be 28wt% to 32wt%, such as 28wt%, 29wt%, 30wt%, 31wt% or 32wt%, etc., or other values ​​within the range of 28wt% to 32wt%.

[0054] In some optional embodiments, the reducing agent in the reducing agent solution may illustratively but not limitatively include at least one of ascorbic acid, sodium ascorbate, glucose and hydrazine hydrate.

[0055] The content of the reducing agent in the reducing agent solution may be 13wt% to 17wt%, such as 13wt%, 14wt%, 15wt%, 16wt% or 17wt%, etc., or may be other values ​​within the range of 13wt% to 17wt%.

[0056] In some more specific embodiments, when the reducing agent is ascorbic acid, the content of ascorbic acid in the reducing agent solution is preferably set to 13wt% to 17wt%; when the reducing agent is sodium ascorbate, the content of sodium ascorbate in the reducing agent solution is preferably set to 13wt% to 13.2wt%.

[0057] The amount of the reducing agent solution is not less than the theoretical amount for completely reducing the silver source in the silver source solution to silver powder. For example, taking the reducing agent solution as an ascorbic acid solution and the silver source solution as a silver nitrate solution as an example, the molar ratio of the silver nitrate solution to the ascorbic acid solution can be set to 2:1 based on the electron molar ratio during the reaction.

[0058] In some optional embodiments, the dispersant in the dispersant solution may illustratively but not limitedly include PVP-K30.

[0059] The content of the dispersant in the dispersant solution may be 5wt% to 30wt%, such as 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%, etc., or may be other values ​​within the range of 5wt% to 30wt%.

[0060] The total amount of the dispersant can be 5wt% to 25wt% of the silver powder, such as 5wt%, 8wt%, 10wt%, 12wt%, 15wt%, 18wt%, 20wt%, 22wt% or 25wt%, etc., or other values ​​within the range of 5wt% to 25wt%.

[0061] In some optional embodiments, the surfactant in the surfactant solution may illustratively but not limitatively include at least one of stearic acid, sodium oleate and carboxylate.

[0062] The content of surfactant in the surfactant solution is 1.0wt% to 10.0wt%, such as 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%, etc., and can also be other values ​​within the range of 1.0wt% to 10.0wt%.

[0063] The total amount of the surfactant can be 1wt‰ to 1wt% of the silver powder, such as 1wt‰, 2wt‰, 4wt‰, 6wt‰, 8wt‰ or 1wt%, or other values ​​within the range of 1wt‰ to 1wt%.

[0064] After adding the surfactant, stirring can continue for 3 to 5 minutes.

[0065] Furthermore, the large-scale production method of the silver powder may also include:

[0066] S5: Stop stirring, let stand (e.g., 25 min to 35 min) to allow the silver powder to settle by itself, then remove the upper clear liquid; add deionized water for washing, let stand again, repeat the washing and standing process, then dry the wet powder (e.g., 45° C. to 55° C.) to obtain a finished silver powder.

[0067] As mentioned above, the above method is simple in process and can effectively avoid the problems of silver powder particle agglomeration and obvious size of particles in the production process, and can achieve stable mass production-level scale-up production of ultrafine silver powder while maintaining a high yield (≥96.5%).

[0068] Specifically, by adding the dispersant at the beginning of the reaction, the silver powder particles can be coated, effectively preventing direct contact between the silver powder particles, thereby avoiding the occurrence of agglomeration. Combined with the optimization and fine control of the reaction (such as the reaction temperature, stirring speed, and reaction time), the uniform amplification of the silver powder is achieved, ensuring that its particle size distribution is narrow and the morphology is consistent. Among them, within a suitable range, the faster the stirring speed, the smaller the particle size of the silver powder produced; the lower the reaction temperature, the smaller the particle size of the silver powder produced; the reaction time>5min can improve the problem of mixed coexistence of large and small particles and narrow the particle size distribution.

[0069] Correspondingly, the present invention provides a silver powder produced by the above-mentioned large-scale production method.

[0070] In some optional embodiments, the D of the silver powder produced is 50 In some typical embodiments, the D of the silver powder produced is 50 It is 0.67μm~1.21μm.

[0071] In some optional embodiments, the span of the produced silver powder is less than 1.5. 90 -D 10 ) / D 50 In some typical embodiments, the span of the produced silver powder is 1.19 to 1.36.

[0072] In some optional embodiments, the produced silver powder is spherical or quasi-spherical.

[0073] In some optional embodiments, the specific surface area of ​​the produced silver powder is 0.5 m 2 / g~1.5m 2 / g, such as 0.5m 2 / g, 0.8m 2 / g, 1m 2 / g, 1.2m 2 / g or 1.5m 2 / g, etc., can also be 0.5m 2 / g~1.5m 2 In some typical embodiments, the specific surface area of ​​the silver powder produced is 0.53 m 2 / g~0.82m 2 / g.

[0074] As mentioned above, the silver powder prepared by the present invention has a narrow particle size distribution, a uniform morphology, a small specific surface area, and good quality.

[0075] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0076] Example 1

[0077] This embodiment provides a method for producing silver powder, which is carried out in a 1L reactor and specifically comprises the following steps:

[0078] S1: Prepare solutions of various materials.

[0079] 62 g of silver nitrate (theoretical silver powder 39.37 g) was dissolved in 144 g of deionized water to prepare 206 g of a silver nitrate solution with a mass fraction of 30%. Accordingly, the concentration of silver ions in the silver nitrate solution was about 2.0 mol / L.

[0080] 20 g of sodium ascorbate was dissolved in 131 g of deionized water to prepare a sodium ascorbate solution with a mass fraction of 13.2%.

[0081] 10 g of PVP-K30 powder was dissolved in 190 g of deionized water and stirred until completely dissolved to obtain 200 g of a dispersant solution with a mass fraction of 5%.

[0082] 5 g of stearic acid powder was dissolved in 495 g of alcohol to prepare a stearic acid solution with a mass fraction of 1.0 wt%.

[0083] S2: Under the stirring conditions of 25°C and 400rpm, first take 150g of dispersant solution and 151g of sodium ascorbate solution and pour them into a 1L reactor, then start the double flow of silver nitrate (first flow path) and sodium ascorbate (second flow path) through a peristaltic pump, and set the double flow time to 5min. After the double flow reacts for 2.5min, the remaining 50g of dispersant solution is also injected through the third flow path through a peristaltic pump, and the injection time is 2.5min.

[0084] S3: After all the silver nitrate solution has been added, immediately add 20 g of surfactant stearic acid solution and continue stirring for 4 minutes.

[0085] S4: After the stirring is completed, stop stirring and let it stand for 30 minutes. After the silver powder settles by itself, pour out the upper clear liquid, add deionized water again, repeat the operation twice, put the wet powder into a 50°C oven to dry, and obtain the finished silver powder.

[0086] In this embodiment, the total amount of the dispersant is 25 wt % of the silver powder, and the total amount of the surfactant is 0.5 wt % of the silver powder.

[0087] Example 2

[0088] This embodiment provides a method for producing silver powder, which is carried out in a 2L reactor and specifically comprises the following steps:

[0089] S1: Prepare solutions of various materials.

[0090] 124 g of silver nitrate (theoretical silver powder 78.74 g) was dissolved in 288 g of deionized water to prepare 412 g of a silver nitrate solution with a mass fraction of 30%. Accordingly, the concentration of silver ions in the silver nitrate solution was about 2.0 mol / L.

[0091] 40 g of sodium ascorbate was dissolved in 262 g of deionized water to prepare a sodium ascorbate solution with a mass fraction of 13.2%.

[0092] 20 g of PVP-K30 powder was dissolved in 380 g of deionized water and stirred until completely dissolved to obtain 400 g of a dispersant solution with a mass fraction of 5%.

[0093] 1 g of stearic acid powder was dissolved in 99 g of alcohol solution to prepare a stearic acid solution with a mass fraction of 1.0 wt%.

[0094] S2: Under the stirring conditions of 25°C and 400rpm, first take 300g of dispersant solution and 302g of sodium ascorbate solution and pour them into a 2L reactor, then start the double flow of silver nitrate (first flow path) and sodium ascorbate (second flow path) through a peristaltic pump, and set the double flow time to 5min. After the double flow reacts for 2.5min, the remaining 100g of dispersant solution is also injected through the third flow path through a peristaltic pump, and the injection time is 2.5min.

[0095] S3: After all the silver nitrate solution has been added, immediately add 80 g of surfactant stearic acid solution and continue stirring for 4 minutes.

[0096] S4: After the stirring is completed, stop stirring and let it stand for 30 minutes. After the silver powder settles by itself, pour out the upper clear liquid, add deionized water again, repeat the operation twice, put the wet powder into a 50°C oven to dry, and obtain the finished silver powder.

[0097] In this embodiment, the total amount of the dispersant is 25 wt % of the silver powder, and the total amount of the surfactant is 1.0 wt % of the silver powder.

[0098] Example 3

[0099] This embodiment provides a method for producing silver powder, which is carried out in a 5L reactor and specifically comprises the following steps:

[0100] S1: Prepare solutions of various materials.

[0101] 310 g of silver nitrate (theoretical silver powder 196.85) was dissolved in 720 g of deionized water to prepare 1030 g of a silver nitrate solution with a mass fraction of 30%.

[0102] 100 g of sodium ascorbate was dissolved in 655 g of deionized water to prepare a sodium ascorbate solution with a mass fraction of 13.2%.

[0103] 50 g of PVP-K30 powder was dissolved in 950 g of deionized water and stirred until completely dissolved to obtain 1000 g of a dispersant solution with a mass fraction of 5%.

[0104] 2.5 g of stearic acid powder was dissolved in 247.5 g of alcohol solution to prepare a stearic acid solution with a mass fraction of 1.0 wt%.

[0105] S2: Under the stirring conditions of 20°C and 350rpm, first pour 750g of dispersant solution and 755g of sodium ascorbate solution into a 5L reactor, then start the double flow of silver nitrate (first flow path) and sodium ascorbate (second flow path) through a peristaltic pump. After the double flow reacts for 5 minutes, the remaining 250g of dispersant solution is also injected through the third flow path through a peristaltic pump, and the injection time is 5 minutes.

[0106] S3: After all the silver nitrate solution has been added, immediately add 150 g of surfactant stearic acid solution and continue stirring for 4 minutes.

[0107] S4: After the stirring is completed, stop stirring and let it stand for 30 minutes. After the silver powder settles by itself, pour out the upper clear liquid, add deionized water again, repeat the operation twice, put the wet powder into a 50°C oven to dry, and obtain the finished silver powder.

[0108] In this embodiment, the total amount of the dispersant is 25 wt % of the silver powder, and the total amount of the surfactant is 0.8 wt % of the silver powder.

[0109] Example 4

[0110] This embodiment provides a method for producing silver powder, which is carried out in a 10L reactor and specifically comprises the following steps:

[0111] S1: Prepare solutions of various materials.

[0112] 620 g of silver nitrate (theoretical silver powder 393.7 g) was dissolved in 1440 g of deionized water to prepare 2060 g of a silver nitrate solution with a mass fraction of 30%.

[0113] 200 g of sodium ascorbate was dissolved in 1310 g of deionized water to prepare a sodium ascorbate solution with a mass fraction of 13.2%.

[0114] 100 g of PVP-K30 powder was dissolved in 1900 g of deionized water and stirred until completely dissolved to obtain 2000 g of a dispersant solution with a mass fraction of 5%.

[0115] 5.0 g of stearic acid powder was dissolved in 495 g of alcohol solution to prepare a stearic acid solution with a mass fraction of 1 wt%.

[0116] S2: Under the stirring conditions of 20°C and 350rpm, first pour 1500g of dispersant solution and 1510g of sodium ascorbate solution into a 10L reactor, and then start the double flow of silver nitrate (first flow path) and sodium ascorbate (second flow path) through a peristaltic pump, and set the double flow time to 20min. After the double flow reacts for 10min, the remaining 500g of dispersant solution is also injected through the third flow path through a peristaltic pump, and the injection time is 10min.

[0117] S3: After all the silver nitrate solution is added, immediately add 400 g of surfactant stearic acid solution and continue stirring for 4 minutes.

[0118] S4: After the stirring is completed, stop stirring and let it stand for 30 minutes. After the silver powder settles by itself, pour out the upper clear liquid, add deionized water again, repeat the operation twice, put the wet powder into a 50°C oven to dry, and obtain the finished silver powder.

[0119] In this embodiment, the total amount of the dispersant is 25 wt % of the silver powder, and the total amount of the surfactant is 1.0 wt % of the silver powder.

[0120] Example 5

[0121] This embodiment provides a method for producing silver powder, which is carried out in a 100L reactor and specifically includes the following steps:

[0122] S1: Prepare solutions of various materials.

[0123] 6200 g of silver nitrate (theoretical silver powder 3937 g) was dissolved in 14400 g of deionized water to prepare 20600 g of silver nitrate solution with a mass fraction of 30%.

[0124] 2000 g of sodium ascorbate was dissolved in 13100 g of deionized water to prepare a sodium ascorbate solution with a mass fraction of 13.2%.

[0125] 1000 g of PVP-K30 powder was dissolved in 19000 g of deionized water and stirred until completely dissolved to obtain 20000 g of a dispersant solution with a mass fraction of 5%.

[0126] 5.0 g of stearic acid powder was dissolved in 495 g of alcohol to prepare a stearic acid solution with a mass fraction of 1 wt%.

[0127] S2: Under the conditions of 20°C and 300rpm stirring, first take 15000g of dispersant solution and 15100g of sodium ascorbate and pour them into a 100L reactor, then start the double flow of silver nitrate (first flow path) and sodium ascorbate (second flow path) through a peristaltic pump, and set the double flow time to 30min. After the double flow reacts for 30min, the remaining 5000g of dispersant solution is also injected through the third flow path through a peristaltic pump, and the injection time is 15min.

[0128] S3: After all the silver nitrate solution is added, immediately add 400 g of surfactant stearic acid solution and continue stirring for 4 minutes.

[0129] S4: After the stirring is completed, stop stirring and let it stand for 30 minutes. After the silver powder settles by itself, pour out the upper clear liquid, add deionized water again, repeat the operation twice, put the wet powder into a 50°C oven to dry, and obtain the finished silver powder.

[0130] In this embodiment, the total amount of the dispersant is 25 wt % of the silver powder, and the total amount of the surfactant is 1.0 wt % of the silver powder.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 5 is that the third flow path is added simultaneously with the first flow path and the second flow path, that is, t1 = t3 = 30 min, t2 = 0 min.

[0133] Comparative Example 2

[0134] The difference between this comparative example and Example 5 is that: t1 = 30 min, t2 = 20 min, t3 = 10 min.

[0135] Comparative Example 3

[0136] The difference between this comparative example and Example 5 is that the entire production process is carried out at 50°C.

[0137] Comparative Example 4

[0138] The difference between this comparative example and Example 5 is that the entire production process is carried out at 150 rpm.

[0139] Comparative Example 5

[0140] The difference between this comparative example and Example 5 is that the entire production process is carried out at 800 rpm.

[0141] Comparative Example 6

[0142] The difference between this comparative example and Example 5 is that after the silver source solution is completely added, the surfactant solution is not added.

[0143] Test example

[0144] The silver powders prepared in the above Examples 1 to 5 and Comparative Examples 1 to 6 were compared, and the results are shown in Table 1 and Figures 1 to 6 shown.

[0145] Table 1 Comparison results

[0146]

[0147] It can be seen from Table 1 that the method provided in the embodiment of the present invention can effectively achieve stable mass production of silver powder while ensuring a high yield, and the obtained silver powder has a narrow particle size distribution, consistent morphology, a small specific surface area, and good quality.

[0148] By comparing Example 5 with Comparative Examples 1 to 6, it can be seen that when some conditions in the production process are improperly set, it will lead to the inability to achieve both high yield and good silver powder quality.

[0149] In summary, the production method provided by the present invention overcomes the technical difficulties of the conventional liquid phase reduction method for preparing silver powder in the scale-up process, especially the control of particle size and morphology, the prevention of agglomeration, the optimization of reaction conditions, the improvement of yield and the maintenance of stability, so that it has good operability and cost advantages, but the actual effect in scale-up production and application reaches a relatively ideal state. Therefore, in industrial applications, large-scale production of high-performance silver powder can be achieved.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A large-scale production method of silver powder, characterized in that: The following steps are involved: Prepare a base solution by mixing part of the dispersant solution and part of the reducing agent solution; The silver source solution and the remaining reducing agent solution are added to the base solution through the first flow path and the second flow path respectively, and the total addition time of the silver source solution and the remaining reducing agent solution is t1; after the silver source solution and the remaining reducing agent solution are added for t2, the remaining dispersant solution is added through the third flow path, and the total addition time of the remaining dispersant solution is t3; after the silver source solution is completely added, the surfactant solution is added immediately; Wherein, t1=t2+t3, t1 is 5min to 30min; and / or, t2 is 2min to 10min; and / or, t3 is 2min to 10min; The entire production process is carried out at 5°C to 45°C; the stirring speed during the entire production process is 250rpm to 600rpm.

2. The large-scale production method according to claim 1, characterized in that: When the volume of the reaction container used in production is less than 100 L, the stirring speed is 300 rpm to 600 rpm; when the volume of the reaction container used in production is ≥100 L, the stirring speed is 250 rpm to 350 rpm.

3. The large-scale production method according to claim 1 or 2, characterized in that: The silver source in the silver source solution comprises at least one of silver nitrate and silver acetate; Preferably, the concentration of silver ions in the silver source solution is 1.8 mol / L to 2.2 mol / L, and the content of silver source in the silver source solution is 28 wt % to 32 wt %.

4. The large-scale production method according to claim 1 or 2, characterized in that: The reducing agent in the reducing agent solution includes at least one of ascorbic acid, sodium ascorbate, glucose and hydrazine hydrate; Preferably, the content of the reducing agent in the reducing agent solution is 13wt% to 17wt%; Preferably, the amount of the reducing agent solution is not less than the theoretical amount for completely reducing the silver source in the silver source solution into silver powder.

5. The large-scale production method according to claim 4, characterized in that: When the reducing agent is ascorbic acid, the content of ascorbic acid in the reducing agent solution is 13 wt % to 17 wt %; when the reducing agent is sodium ascorbate, the content of sodium ascorbate in the reducing agent solution is 13 wt % to 13.2 wt %.

6. The large-scale production method according to claim 1 or 2, characterized in that: The dispersant in the dispersant solution includes PVP-K30; Preferably, the content of the dispersant in the dispersant solution is 5wt% to 30wt%; Preferably, the total amount of the dispersant is 5wt% to 25wt% of the silver powder.

7. The large-scale production method according to claim 1 or 2, characterized in that: The surfactant in the surfactant solution includes at least one of stearic acid, sodium oleate and carboxylate; Preferably, the content of the surfactant in the surfactant solution is 1.0 wt% to 10.0 wt%; Preferably, the total amount of the surfactant is 1wt‰ to 1wt% of the silver powder.

8. A silver powder, characterized in that: The product is produced by the large-scale production method described in any one of claims 1 to 7.

9. The silver powder according to claim 8, characterized in that The silver powder D 50 The thickness of the silver powder is 500nm-3μm, and the span of the silver powder is less than 1.

5.

10. The silver powder according to claim 8, characterized in that The silver powder is spherical or quasi-spherical, and the specific surface area of ​​the silver powder is 0.5 m 2 / g~1.5m 2 / g.

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