High-consistency silver powder and preparation method thereof

Abstract

The invention discloses high-consistency silver powder and a preparation method thereof, and belongs to the technical field of powder preparation. The preparation method comprises the following steps: respectively providing a silver source solution, a reducing agent solution, a compound dispersing agent solution and a coating agent solution; the pH value of the reducing agent solution is adjusted to be acidic, the reducing agent solution and the silver source solution are dropwise added into the compound dispersing agent solution step by step at the same time, after stirring treatment, the coating agent solution is added, stirring continues, and turbid liquid is obtained; and settling the turbid liquid, and carrying out solid-liquid separation, washing and drying to obtain the high-consistency silver powder. The silver powder with uniform particle size distribution and high consistency can be prepared by using the compound dispersing agent formed by combining the low-molecular-weight polyvinyl pyrrolidone and the high-molecular-weight polyvinyl pyrrolidone; and meanwhile, the reducing agent solution and the silver source solution are dropwise added step by step at the same time, and the particle size distribution uniformity and consistency of the silver powder can be further improved. Therefore, the method has a good application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder preparation, and particularly relates to high-consistency silver powder and a preparation method thereof. BACKGROUND

[0002] Silver powder is usually white or off-white and has metallic luster. The particle shape of silver powder is various, and common shapes include spherical, flaky, dendritic, etc. The morphology structure, particle size and distribution characteristics, bulk density and tap density, specific surface area, sintering performance, corrosion resistance, etc. of silver powder all affect the performance of silver conductive paste. Therefore, how to prepare silver powder with stable performance has become a research hotspot.

[0003] At present, the preparation methods of silver powder include mechanical ball milling, evaporation condensation, spray pyrolysis, chemical reduction, electrochemical deposition, microemulsion, etc. For example, a kind of controllable particle size distribution of spherical silver powder and its preparation method and application are disclosed in Chinese patent application document CN113658739A. The spherical silver powder is prepared by a wet chemical oxidation-reduction reaction method. However, the silver powder prepared by the above technical solution contains multiple particle sizes, and the particle size distribution of the silver powder is uneven and the consistency is poor.

[0004] Therefore, it is necessary to provide high-consistency silver powder and a preparation method thereof to solve the problems existing in the prior art. SUMMARY

[0005] The application aims to provide high-consistency silver powder and a preparation method thereof. The application solves the problems of uneven particle size distribution and poor consistency of existing silver powder.

[0006] In a first aspect, the application provides a preparation method of high-consistency silver powder, comprising the following steps: providing a silver source solution, a reducing agent solution, a compounded dispersant solution, and a coating agent solution, respectively; adjusting the pH value of the reducing agent solution to be acidic, and simultaneously adding the silver source solution and the reducing agent solution to the compounded dispersant solution by stepwise dripping, and then stirring to obtain a suspension liquid; adding the coating agent solution and continuing to stir to obtain a suspension liquid; and then performing sedimentation on the suspension liquid, and performing solid-liquid separation, washing, and drying to obtain high-consistency silver powder; wherein the compounded dispersant solution comprises low-molecular-weight polyvinylpyrrolidone and high-molecular-weight polyvinylpyrrolidone.

[0007] In the application, the inventors have found that the use of a compounded dispersant composed of low-molecular-weight polyvinylpyrrolidone and high-molecular-weight polyvinylpyrrolidone can prepare silver powder with uniform particle size distribution and high consistency. Meanwhile, the use of the stepwise dripping process for simultaneously adding the reducing agent solution and the silver source solution can further improve the uniformity and consistency of the particle size distribution of the silver powder. In addition, the preparation method of the application is simple, the raw materials used are cheap and easy to obtain, and it is suitable for industrial large-scale production and application.

[0008] In some embodiments, the concentration of the silver source solution is 200-300 g / L, the silver source solution comprises a silver nitrate solution, the concentration of the reducing agent solution is 100-200 g / L, the concentration of the complex dispersant solution is 10-50 g / L, and the concentration of the coating agent solution is 30-80 g / L; the volume ratio of the silver source solution, the reducing agent solution, the complex dispersant solution, and the coating agent solution is (50-70):(50-70):(80-100):(0.8-1.2).

[0009] In some embodiments, the mass ratio of the low-molecular-weight polyvinylpyrrolidone and the high-molecular-weight polyvinylpyrrolidone is (1-8):1.

[0010] In some embodiments, the reducing agent solution comprises at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

[0011] In some embodiments, the coating agent solution comprises at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

[0012] In some embodiments, in the step of obtaining the suspension, the stepwise dropping comprises a first stepwise dropping, a second stepwise dropping, and a third stepwise dropping; wherein the first stepwise dropping is performed at a speed of 50-70 ml / min, a temperature of 10-30°C, and for a time of 1-2 min; the second stepwise dropping is performed at a speed of 300-400 ml / min, a temperature of 40-60°C, and for a time of 1-2 min; and the third stepwise dropping is performed at a speed of 100-200 ml / min, a temperature of 40-60°C, and for a time of 1-2 min.

[0013] In some embodiments, in the step of obtaining the high-consistency silver powder, the washing comprises washing with a cleaning liquid until the conductivity of the filtrate is <20 μS / m; wherein the cleaning liquid comprises at least one of deionized water and anhydrous ethanol.

[0014] In some embodiments, in the step of obtaining the high-consistency silver powder, the drying comprises drying at a temperature of 40-80°C for 20-24 h.

[0015] In a second aspect, the present application provides a high-consistency silver powder, which is prepared by any of the above preparation methods.

[0016] In some embodiments, the D10 particle size of the high-consistency silver powder is 0.94-0.97 μm, the D50 particle size is 1.41-1.44 μm, the D90 particle size is 2.09-2.14 μm, the D100 particle size is 3.39-3.55 μm, and the tap density is 6.53-6.55 g / cm 3 .

[0017] The beneficial effects of the present application are: different from the prior art, the present application can prepare silver powder with uniform particle size distribution and high consistency by using a complex dispersant combined with low molecular weight polyvinylpyrrolidone and high molecular weight polyvinylpyrrolidone; at the same time, the simultaneous stepwise dropping process of the reducing agent solution and the silver source solution can further improve the uniformity and consistency of the particle size distribution of the silver powder; in addition, the preparation method of the present application is simple, the raw materials used are cheap and easy to obtain, and is suitable for industrial large-scale production application. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Preparation method flow chart of high consistency silver powder in the present application; Figure 2 SEM image of high consistency silver powder prepared in Example 1 of the present application; Figure 3 SEM image of high consistency silver powder prepared in Example 2 of the present application; Figure 4 SEM image of high consistency silver powder prepared in Example 3 of the present application; Figure 5 SEM image of silver powder prepared in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application, obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0020] The experimental methods not specified in the embodiments are usually carried out according to the conventional conditions and the conditions described in the manual, or according to the conditions suggested by the manufacturer, and the general equipment, materials, reagents, etc. used are commercially available, unless otherwise specified.

[0021] At present, the existing silver powder has problems of uneven particle size distribution and poor consistency.

[0022] In order to solve the problems of uneven particle size distribution and poor consistency of the existing silver powder, the present application provides a high consistency silver powder and a preparation method thereof.

[0023] In a first aspect, the present application provides a method for preparing high-consistency silver powder, comprising the following steps: providing a silver source solution, a reducing agent solution, a compounded dispersant solution, and a coating agent solution, respectively; adjusting the pH value of the reducing agent solution to be acidic, and simultaneously adding the silver source solution and the reducing agent solution into the compounded dispersant solution by steps, and then stirring to obtain a suspension after adding the coating agent solution and continuing to stir; performing sedimentation on the suspension, and then performing solid-liquid separation, washing, and drying to obtain high-consistency silver powder; wherein the compounded dispersant solution comprises low-molecular-weight polyvinylpyrrolidone and high-molecular-weight polyvinylpyrrolidone.

[0024] In the present application, the inventors have found that polyvinylpyrrolidone (PVP) with different K values has different dispersing effects, PVP is easy to adsorb on the surface of Ag + The PVP forms a complex with the silver ions, and when the silver is reduced, the PVP is adsorbed on the surface of the silver, thereby affecting the growth of the silver powder. With the progress of the reaction, the crystal nucleation and growth form secondary particles, and in this process, the PVP will preferentially adsorb on the sharp parts of the surface of the secondary particles, change the specific surface energy, and reduce the growth rate of this part, thereby promoting the deposition and growth of silver atoms at non-sharp parts into spherical particles with a relatively smooth surface. After the spherical particles are generated, the PVP is uniformly adsorbed on the surface of the particles, and the steric hindrance formed by the long-chain structure of the PVP not only hinders the subsequent reduced silver atoms from continuing to grow on the silver particles, preventing the silver powder from being too large in size, but also reduces the collision between the silver powder particles and the particles, reducing the agglomeration of the silver powder, and ultimately preparing spherical silver powder with a relatively smooth surface and good dispersibility. The higher the K value of the PVP is, the longer the PVP molecular chain is, and the stronger the steric hindrance effect is. In order to produce high-consistency silver powder, different K values of PVP are compounded in the present application to control the steric hindrance effect of the PVP, thereby significantly improving the particle size uniformity and consistency of the silver powder.

[0025] In some embodiments, the concentration of the silver source solution is 200-300 g / L, for example, it can be 200 g / L, 220 g / L, 250 g / L, 270 g / L, 300 g / L or other values in the range; the silver source solution includes a silver nitrate solution, the concentration of the reducing agent solution is 100-200 g / L, for example, it can be 100 g / L, 120 g / L, 150 g / L, 170 g / L, 200 g / L or other values in the range; the concentration of the complex dispersant solution is 10-50 g / L, for example, it can be 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L or other values in the range; the concentration of the coating agent solution is 30-80 g / L, for example, it can be 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L or other values in the range; the volume ratio of the silver source solution, the reducing agent solution, the complex dispersant solution and the coating agent solution is (50-70):(50-70):(80-100):(0.8-1.2), for example, it can be 50:50:80:0.8, 50:60:90:1, 50:70:100:1.2, 60:50:80:0.8, 60:60:90:1, 60:70:100:1.2, 70:50:80:0.8, 70:60:90:1, 70:70:100:1.2 or other ratios in the range.

[0026] In the present application, by controlling the concentration and volume ratio of the silver source solution, the reducing agent solution, the complex dispersant solution and the coating agent solution in a specific range, the reaction can be complete, and further, the silver powder with uniform particle size distribution and high consistency can be obtained.

[0027] It can be understood that the silver source solution, the reducing agent solution and the complex dispersant solution are obtained by dissolving the silver source, the reducing agent and the complex dispersant in deionized water respectively; the coating agent solution is obtained by dissolving the coating agent in an organic solvent, preferably, the organic solvent includes anhydrous ethanol.

[0028] In some embodiments, the mass ratio of the low molecular weight polyvinylpyrrolidone and the high molecular weight polyvinylpyrrolidone is (1-8):1, for example, it can be 1:1, 3:1, 5:1, 7:1, 8:1 or other ratios in the range.

[0029] In the present application, the complex dispersant obtained by mixing the low molecular weight polyvinylpyrrolidone and the high molecular weight polyvinylpyrrolidone according to a specific mass ratio has better dispersing performance, and can further significantly improve the particle size uniformity and consistency of the silver powder.

[0030] In some embodiments, the reducing agent solution includes at least one of ascorbic acid, glucose, formaldehyde, triethanolamine and hydrazine hydrate.

[0031] It can be understood that the kind of the reducing agent solution can be selected from conventional reducing agents in the prior art according to actual needs, as long as the reducing activity can be played. For example, in the present application, the reducing agent solution preferably includes at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

[0032] In some embodiments, the coating agent solution includes at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

[0033] It can be understood that the kind of the coating agent solution can be selected from conventional coating agents in the prior art according to actual needs, as long as the coating can be performed. For example, in the present application, the coating agent solution preferably includes at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

[0034] In some embodiments, in the step of obtaining the suspension, the stepwise dropping includes a first stepwise dropping, a second stepwise dropping, and a third stepwise dropping; wherein the first stepwise dropping has a speed of 50-70 ml / min, for example, can be 50 ml / min, 60 ml / min, 70 ml / min, or other values in the range; the temperature is 10-30°C, for example, can be 10°C, 20°C, 30°C, or other values in the range; the time is 1-2 min, for example, can be 1 min, 1.5 min, 2 min, or other values in the range; the second stepwise dropping has a speed of 300-400 ml / min, for example, can be 300 ml / min, 350 ml / min, 400 ml / min, or other values in the range; the temperature is 40-60°C, for example, can be 40°C, 50°C, 60°C, or other values in the range; the time is 1-2 min, for example, can be 1 min, 1.5 min, 2 min, or other values in the range; the third stepwise dropping has a speed of 100-200 ml / min, for example, can be 100 ml / min, 150 ml / min, 200 ml / min, or other values in the range; the temperature is 40-60°C, for example, can be 40°C, 50°C, 60°C, or other values in the range; the time is 1-2 min, for example, can be 1 min, 1.5 min, 2 min, or other values in the range.

[0035] In the present application, the inventors further found that accurate control of the dropping speed of the oxidizing agent (silver nitrate solution) and the reducing agent is a key factor affecting the reaction stability, silver powder particle size distribution and morphology consistency. The dropping speed of the oxidizing agent directly affects the local concentration of Ag+ in the reaction system, and then affects the nucleation rate and particle growth kinetics. Too fast dropping speed will lead to local supersaturation, causing instantaneous nucleation of a large number of small particles with poor dispersibility; too slow dropping speed may lead to excessive growth of particles. Therefore, in the present application, a stepwise dropping method is adopted, i.e., slow dropping at the initial stage to form a small amount of crystal nuclei at low Ag+ concentration to lay the foundation for monodispersity; accelerated dropping at the middle stage to promote uniform growth of particles in the presence of stable crystal nuclei; and decelerated dropping at the later stage to avoid secondary nucleation caused by excess Ag+. The dropping speed of the reducing agent determines the conversion rate of Ag+ to Ag, affecting the balance between nucleation and growth. Excess reducing agent may cause rapid reduction, leading to particle agglomeration or irregular morphology (such as dendrites). The dropping speed of the reducing agent is synchronously controlled with the dropping speed of the oxidizing solution to ensure that the Ag+ is completely reduced but not in excess. Through the coordinated control of the dropping speed of the oxidizing-reducing agent and the adjustment of the temperature at different stages, the complex dispersant is preferentially adsorbed on the surface of silver crystal nuclei at the low-temperature nucleation stage to inhibit rapid growth, and the defects in the particles are eliminated at the high-temperature maturation stage to improve the consistency; thereby, silver powder with high morphology consistency is prepared. 0

[0036] In some embodiments, in the step of obtaining the silver powder with high consistency, the washing comprises: washing with a cleaning liquid until the conductivity of the filtrate is <20 μS / m; wherein the cleaning liquid comprises at least one of deionized water and anhydrous ethanol.

[0037] It can be understood that the type of cleaning liquid can be selected according to actual needs, as long as it can be cleaned. For example, in the present application, the cleaning liquid preferably comprises at least one of deionized water and anhydrous ethanol.

[0038] In some embodiments, in the step of obtaining the silver powder with high consistency, the drying comprises: drying at a temperature of 40-80°C (for example, it can be 40°C, 50°C, 60°C, 70°C, 80°C or other values within the range) for 20-24 h (for example, it can be 20 h, 21 h, 22 h, 23 h, 24 h or other values within the range).

[0039] In the present application, by controlling the temperature and time of drying within a specific range, the moisture in the silver powder can be removed.

[0040] In a second aspect, the present application provides a silver powder with high consistency, which is prepared by any of the above preparation methods.

[0041] ​In some embodiments, the high-consistency silver powder has a D10 particle size of 0.94-0.97 μm, for example, 0.94 μm, 0.95 μm, 0.96 μm, 0.97 μm, or other values within the range; a D50 particle size of 1.41-1.44 μm, for example, 1.41 μm, 1.42 μm, 1.43 μm, 1.44 μm, or other values within the range; a D90 particle size of 2.09-2.14 μm, for example, 2.09 μm, 2.1 μm, 2.12 μm, 2.14 μm, or other values within the range; a D100 particle size of 3.39-3.55 μm, for example, 3.39 μm, 3.43 μm, 3.47 μm, 3.51 μm, 3.55 μm, or other values within the range; a tap density of 6.53-6.55 g / cm 3 , for example, 6.53 g / cm 3 , 6.54 g / cm 3 , 6.55 g / cm 3 , or other values within the range.

[0042] The silver powder in the present application has high consistency, a smaller SPAN value, uniform particle size distribution, reduced silver powder adhesion and agglomeration, and a higher tap density.

[0043] Some specific examples are listed below. It should be noted that the examples described below are exemplary and are used to explain the present application, and cannot be understood as limiting the present application.

[0044] Please refer to Figure 1 , which is a flow chart of the preparation method of the high-consistency silver powder in the present application. Specifically, the preparation method of the high-consistency silver powder comprises the following steps: providing a silver source solution, a reducing agent solution, a compounded dispersant solution, and a coating agent solution, respectively; adjusting the pH value of the reducing agent solution to be alkaline, and simultaneously adding the silver source solution and the reducing agent solution to the compounded dispersant solution in steps, stirring, adding the coating agent solution, and continuing to stir to obtain a suspension; performing sedimentation on the suspension, and performing solid-liquid separation, washing, and drying to obtain the high-consistency silver powder.

[0045] Example 1 A preparation method of a high-consistency silver powder, comprising the following steps: S1, take 160g silver nitrate into a beaker, add 600ml deionized water to stir and dissolve, warm and keep to 25℃, get silver nitrate solution; take 86.4g ascorbic acid into a beaker, add 600ml deionized water to stir and dissolve, get reducing agent solution; take 11.2g polyvinylpyrrolidone (K30) and 11.2g polyvinylpyrrolidone (K35) into a beaker, add 900ml deionized water to stir and dissolve, get complex dispersant solution; take 0.5g oleic acid into a beaker, add 10ml anhydrous ethanol to stir and dissolve, get coating agent solution; S2, transfer the complex dispersant solution obtained in step S1 to a reaction kettle, start mechanical stirring, control the stirring speed to 500rpm; use 10mol / L sodium hydroxide solution to adjust the pH value of the reducing agent solution obtained in step S1 to 5.5, and add it and the silver nitrate solution obtained in step S1 into the reaction kettle at the same time by stepwise dropping, wherein the stepwise dropping includes first stepwise dropping, second stepwise dropping and third stepwise dropping, the first stepwise dropping speed is 50ml / min, the temperature is 25℃, and the time is 2min; the second stepwise dropping speed is 300ml / min, the temperature is 40℃, and the time is 1min; the third stepwise dropping speed is 100ml / min, the temperature is 40℃, and the time is 2min; after dropping, stir for 5min, add the coating agent solution obtained in step S1, continue to stir for 5min, get the suspension; S3, sedimentation is carried out on the suspension obtained in step S2, the supernatant is poured out, the silver powder is washed with deionized water and anhydrous ethanol respectively, the washing is carried out until the conductivity of the filtrate is <20μS / m, the silver powder is dried in a 60℃ air drying oven for 22h, get high consistency silver powder.

[0046] Example 2 A method for preparing high consistency silver powder, comprising the following steps: S1, take 160g silver nitrate into a beaker, add 600ml deionized water to stir and dissolve, warm and keep to 25℃, get silver nitrate solution; take 86.4g ascorbic acid into a beaker, add 600ml deionized water to stir and dissolve, get reducing agent solution; take 11.2g polyvinylpyrrolidone (K30) and 11.2g polyvinylpyrrolidone (K35) into a beaker, add 900ml deionized water to stir and dissolve, get complex dispersant solution; take 0.5g oleic acid into a beaker, add 10ml anhydrous ethanol to stir and dissolve, get coating agent solution; S2, the complex dispersant solution obtained in step S1 is transferred to a reaction kettle, mechanical stirring is started, and the stirring rate is controlled at 500 rpm; the pH value of the reducing agent solution obtained in step S1 is adjusted to 5 using a 10 mol / L sodium hydroxide solution, and it is added to the reaction kettle at the same time as the silver nitrate solution obtained in step S1, wherein the stepwise addition includes first stepwise addition, second stepwise addition, and third stepwise addition, the first stepwise addition has a speed of 50 ml / min, a temperature of 25°C, and a time of 2 min; the second stepwise addition has a speed of 300 ml / min, a temperature of 40°C, and a time of 1 min; the third stepwise addition has a speed of 100 ml / min, a temperature of 40°C, and a time of 2 min; after the addition is completed, stirring is continued for 5 min, the coating agent solution obtained in step S1 is added, and stirring is continued for 5 min to obtain a suspension; S3, the suspension obtained in step S2 is settled, the supernatant is poured out, and the silver powder is washed with deionized water and anhydrous ethanol through solid-liquid separation, and the conductivity of the filtrate is <20 μS / m. After drying in a 60°C air-drying oven for 22 h, high-consistency silver powder is obtained.

[0047] Example 3 A method for preparing high-consistency silver powder includes the following steps: S1, 160 g of silver nitrate is added to a beaker, 600 ml of deionized water is added and stirred to dissolve, and the temperature is raised and maintained at 25°C to obtain a silver nitrate solution; 86.4 g of ascorbic acid is added to a beaker, 600 ml of deionized water is added and stirred to dissolve to obtain a reducing agent solution; 19.6 g of polyvinylpyrrolidone (K30) and 2.8 g of polyvinylpyrrolidone (K90) are added to a beaker, 900 ml of deionized water is added and stirred to dissolve to obtain a complex dispersant solution; 0.5 g of oleic acid is added to a beaker, 10 ml of anhydrous ethanol is added and stirred to dissolve to obtain a coating agent solution; S2, the complex dispersant solution obtained in step S1 is transferred to a reaction kettle, mechanical stirring is started, and the stirring rate is controlled at 500 rpm; the pH value of the reducing agent solution obtained in step S1 is adjusted to 5 using a 10 mol / L sodium hydroxide solution, and it is added to the reaction kettle at the same time as the silver nitrate solution obtained in step S1, wherein the stepwise addition includes first stepwise addition, second stepwise addition, and third stepwise addition, the first stepwise addition has a speed of 50 ml / min, a temperature of 25°C, and a time of 2 min; the second stepwise addition has a speed of 300 ml / min, a temperature of 40°C, and a time of 1 min; the third stepwise addition has a speed of 100 ml / min, a temperature of 40°C, and a time of 2 min; after the addition is completed, stirring is continued for 5 min, the coating agent solution obtained in step S1 is added, and stirring is continued for 5 min to obtain a suspension; S3, the suspension obtained in step S2 is settled, the supernatant is poured out, the silver powder is separated from the liquid and washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate is less than 20 μS / m, and then the silver powder is dried in a blast drying oven at 60°C for 22 h to obtain the high-consistency silver powder.

[0048] Comparative Example 1 A method for preparing silver powder, comprising the following steps: S1, 160 g of silver nitrate is taken into a beaker, 600 ml of deionized water is added and stirred to dissolve, and the temperature is raised and kept at 25°C to obtain a silver nitrate solution; 86.4 g of ascorbic acid is taken into a beaker, 600 ml of deionized water is added and stirred to dissolve to obtain a reducing agent solution; 22.4 g of polyvinylpyrrolidone (K30) is taken into a beaker, 900 ml of deionized water is added and stirred to dissolve to obtain a complex dispersant solution; 0.5 g of oleic acid is taken into a beaker, 10 ml of anhydrous ethanol is added and stirred to dissolve to obtain a coating agent solution; S2, the complex dispersant solution obtained in step S1 is transferred to a reaction kettle, mechanical stirring is started, and the stirring speed is controlled at 500 rpm; the pH value of the reducing agent solution obtained in step S1 is adjusted to 5.5 using a 10 mol / L sodium hydroxide solution, and it is added to the reaction kettle at the same time as the silver nitrate solution obtained in step S1, wherein the dropping speed is 120 ml / min, the temperature is 40°C, and the time is 5 min; after the dropping is completed, stirring is continued for 5 min, the coating agent solution obtained in step S1 is added, and stirring is continued for 5 min to obtain a suspension; S3, the suspension obtained in step S2 is settled, the supernatant is poured out, the silver powder is separated from the liquid and washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate is less than 20 μS / m, and then the silver powder is dried in a blast drying oven at 60°C for 22 h to obtain the high-consistency silver powder.

[0049] Performance test The high-consistency silver powder prepared in Examples 1-3 and the silver powder prepared in Comparative Example 1 are subjected to SEM test, and the results are shown in Figures 2-5 .

[0050] As can be seen from Figures 2-5 , compared with Comparative Example 1, the consistency of the silver powder prepared in Examples 1-3 is better, and the particle size is more uniform.

[0051] Further, the performance of the high-consistency silver powder prepared in Examples 1-3 and the silver powder prepared in Comparative Example 1 is tested, and the results are shown in Table 1.

[0052] Table 1 Performance test results

[0053] As can be seen from Table 1, compared with Comparative Example 1, the silver powder prepared in Examples 1-3 has higher consistency, smaller SPAN value, uniform particle size distribution, reduced silver powder adhesion and agglomeration, and higher tap density.

[0054] In conclusion, the combination of low molecular weight polyvinylpyrrolidone and high molecular weight polyvinylpyrrolidone in the present application can prepare silver powder with uniform particle size distribution and high consistency; and the simultaneous stepwise dropping process of the reducing agent solution and the silver source solution can further improve the particle size distribution uniformity and consistency of the silver powder.

[0055] It should be noted that each of the above embodiments belongs to the same inventive concept, and the description of each embodiment has its own emphasis. If the description in an individual embodiment is not exhaustive, the description in other embodiments can be referred to.

[0056] The above-described embodiments only express the implementation of the present application, and the description is more specific and detailed, but it should not be construed as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method for preparing a high-consistency silver powder, characterized by, The method comprises the following steps: providing a silver source solution, a reducing agent solution, a compound dispersant solution, and a coating agent solution, respectively; adjusting the pH value of the reducing agent solution to be acidic, and adding the silver source solution and the reducing agent solution into the compound dispersant solution step by step, and then adding the coating agent solution after stirring, to obtain a suspension; settling the suspension, and obtaining high-consistency silver powder after solid-liquid separation, washing, and drying; the compound dispersant solution comprises low-molecular-weight polyvinylpyrrolidone and high-molecular-weight polyvinylpyrrolidone.

2. The method for preparing highly uniform silver powder according to claim 1, characterized in that, The concentration of the silver source solution is 200-300 g / L, the silver source solution comprises a silver nitrate solution, the concentration of the reducing agent solution is 100-200 g / L, the concentration of the compound dispersant solution is 10-50 g / L, and the concentration of the coating agent solution is 30-80 g / L. The volume ratio of the silver source solution, the reducing agent solution, the compound dispersant solution, and the coating agent solution is (50-70):(50-70):(80-100):(0.8-1.2).

3. The method for preparing highly uniform silver powder according to claim 1, characterized in that, The mass ratio of the low-molecular-weight polyvinylpyrrolidone and the high-molecular-weight polyvinylpyrrolidone is (1-8):

1.

4. The method for preparing highly uniform silver powder according to claim 1, characterized in that, The reducing agent solution comprises at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

5. The method for preparing highly uniform silver powder according to claim 1, characterized in that, The coating agent solution comprises at least one of oleic acid, lauric acid, stearic acid, and palmitic acid.

6. The method for preparing highly uniform silver powder according to claim 1, characterized in that, In the step of obtaining the suspension, the stepwise addition comprises first stepwise addition, second stepwise addition, and third stepwise addition. The first stepwise addition is performed at a speed of 50-70 ml / min, a temperature of 10-30℃, and a time of 1-2 min; the second stepwise addition is performed at a speed of 300-400 ml / min, a temperature of 40-60℃, and a time of 1-2 min; and the third stepwise addition is performed at a speed of 100-200 ml / min, a temperature of 40-60℃, and a time of 1-2 min.

7. The method for preparing highly uniform silver powder according to claim 1, characterized in that, In the step of obtaining the high-consistency silver powder, the washing comprises washing with a cleaning liquid until the conductivity of the filtrate is less than 20 μS / m. The cleaning liquid comprises at least one of deionized water and anhydrous ethanol.

8. The method for preparing highly uniform silver powder according to claim 1, characterized in that, In the step of obtaining the high-consistency silver powder, the drying comprises drying at a temperature of 40-80℃ for 20-24 h.

9. A high-consistency silver powder, characterized by, The high-consistency silver powder is prepared by the method of any one of claims 1-8.

10. The high-consistency silver powder of claim 9, wherein The high-consistency silver powder has a D10 particle size of 0.94-0.97 μm, a D50 particle size of 1.41-1.44 μm, a D90 particle size of 2.09-2.14 μm, a D100 particle size of 3.39-3.55 μm, and a tap density of 6.53-6.55 g / cm 3 .

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