Silver powder with narrow particle size distribution and preparation method thereof

Abstract

The invention provides silver powder with narrow particle size distribution and a preparation method thereof, and the preparation method comprises the following steps: dispersing silver nitrate in deionized water to obtain a solution A; dispersing a reducing agent in deionized water to obtain a solution B; dispersing a dispersing agent in deionized water to obtain a solution C; dispersing a coating agent in absolute ethyl alcohol to obtain a solution D; mixing the solution A and the solution C with set metering, heating to 60-70 DEG C to obtain a mixed solution, adding the solution B into the mixed solution, and stirring for reaction; when the concentration of Ag < + > in the mixed solution is reduced to 40-60%, adding the residual solution C into the mixed solution, reducing the temperature of the mixed solution to 40-50 DEG C, and continuing to add the solution B until charging is completed to obtain a reaction solution; and the solution D is added into the reaction solution, and the narrow-particle-size-distribution silver powder is obtained after the reaction is finished. The problems of secondary nucleation and non-uniform particle size distribution caused by improper addition of the dispersing agent when the silver powder is prepared by a chemical reduction method are solved by dynamically regulating and controlling the dispersing agent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal powder preparation, in particular to a kind of narrow particle size distribution silver powder and preparation method thereof. BACKGROUND

[0002] In prior art, Chinese patent 202110819190.X, publication date is November 16, 2021, the name is "a kind of particle size controllable distribution's spheroidal silver powder and preparation method and application", is prepared by the method of wet chemical oxidation-reduction reaction, the spheroidal silver powder with high tap density and uniform distribution is obtained.But, the silver powder prepared in the above technical scheme contains a variety of particle size in particle size, the particle size distribution range is wide, thus not suitable for front silver paste printing, at the same time, the process of generating silver powder particles in the above preparation method involves multiple variables, and the property regulation of silver powder particles is cumbersome.

[0003] In prior art, Chinese patent 201310036975.5, publication date is March 4, 2015, the name is "a kind of preparation method of high tap density monodisperse silver powder", by adding alkali metal salt and boric acid in silver precursor solution, the nucleation process and crystallization performance of silver powder are controlled, micron silver powder with uniform particles and narrow particle size distribution is prepared, the tap density of single specification silver powder can be greater than 5.5g / cm 3 . But different particle size characteristics of silver powder need to be mixed, the tap density can be increased to 6.5g / cm 3 . At the same time, the addition of alkali metal will introduce impurities in silver powder.

[0004] In traditional silver powder preparation, the dispersant adding method is single (such as one-time addition), which leads to uneven coverage of dispersant in silver ion reduction process, causing secondary nucleation and particle size distribution divergence. Although high concentration dispersant can inhibit agglomeration, it will hinder the diffusion of silver ions, and cannot fundamentally inhibit the particle size divergence in nucleation stage. SUMMARY

[0005] In view of the technical problems existing in the background art, the present application provides a kind of narrow particle size distribution silver powder and preparation method thereof, to solve the technical problem of silver powder particle size distribution divergence.

[0006] In the first aspect, the embodiments of the present application provide a preparation method of a kind of narrow particle size distribution silver powder, comprising the following steps: Disperse silver nitrate in deionized water to obtain solution A; Disperse the reducing agent in deionized water to obtain solution B; Disperse the dispersant in deionized water to obtain solution C; Disperse the coating agent in anhydrous ethanol to obtain solution D; Mix solution A and set amount of solution C, and heat to 60~70℃ to obtain a mixed solution, then add solution B into the mixed solution at a set flow rate, and stir to react; When the concentration of Ag + in the mixed solution is reduced to 40%~60% of the initial Ag + concentration, add the remaining solution C into the mixed solution, reduce the temperature of the mixed solution to 40~50℃, and continue to add solution B into the mixed solution at the set flow rate until the addition is completed to obtain a reaction solution; Add solution D into the reaction solution, and after the reaction is completed, perform solid-liquid separation and cleaning to obtain silver powder with narrow particle size distribution.

[0007] In some embodiments, the concentration of silver nitrate in solution A is 0.8~1.2 mol / L.

[0008] In some embodiments, the concentration of the reducing agent in solution B is 0.5~0.6 mol / L, and the reducing agent includes at least one of ascorbic acid, glucose, formaldehyde, triethanolamine, and hydrazine hydrate.

[0009] In some embodiments, the dispersant in solution C accounts for 5%~20% of the mass of silver nitrate, and the dispersant is at least one of PVP, gelatin, and polyethylene glycol.

[0010] In some embodiments, the K value of PVP is 31.5~33, the water content is <4%, the pH value is 3~4, the peroxide content is less than or equal to 200 mg / L, and the weight average molecular weight is 25000~40000.

[0011] In some embodiments, the coating agent includes at least one of oleic acid, lauric acid, stearic acid, and palmitic acid, and the mass ratio of the coating agent to silver nitrate is (0.8~1.2):100.

[0012] In some embodiments, the pH of solution B is adjusted to 4~6 by using lye.

[0013] In some embodiments, the amount of solution C added is 40~60wt%.

[0014] In some embodiments, the set flow rate at which solution B is added into the mixed solution is 95 mL / min.

[0015] In a second aspect, the embodiments of the present application provide a silver powder with narrow particle size distribution, which is prepared by using the above method.

[0016] Compared with the prior art, the beneficial effects of the present application include: In the technical scheme of the embodiment of the present application, the dispersant is added in two stages, the first-stage dispersant is 40% to 60% of the total dispersant, the reaction temperature of the first stage is 60 to 70°C, the silver nitrate concentration is high at the initial stage of the reaction, the reducing agent is rapidly mixed with the silver nitrate at a high temperature and reacts rapidly, burst nucleation occurs, and a large number of primary particles are generated, because the solute concentration is high at the initial stage of the reaction, a large number of primary particles tend to aggregate and grow into spherical particles, in addition, the dispersing effect of the PVP dispersant in the growth process and the temperature control inhibit excessive nucleation at a high temperature, and therefore, the spherical silver powder with good dispersibility can be finally prepared.

[0017] The first stage consumes a large amount of silver nitrate, at the second stage, the concentration of silver nitrate is greatly reduced, the reaction rate is slowed down, and the process of nucleation is separated from the process of growth, so that the process of nucleation and growth is basically separated. The remaining dispersant is added at the second stage to maintain the dispersion stability of the silver nuclei and inhibit secondary nucleation, and the reaction temperature at the second stage is controlled at 40 to 50°C to inhibit excessive nucleation at a high temperature, thereby reducing the particle size distribution width SPAN of the silver powder to less than 1.0.

[0018] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating labor.

[0020] Figure 1 The SEM image of the silver powder in Example 1 of the present application.

[0021] Figure 2 The SEM image of the silver powder in Example 2 of the present application.

[0022] Figure 3 The SEM image of the silver powder in Comparative Example 1 of the present application.

[0023] Figure 4 The SEM image of the silver powder in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the technical scheme of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical scheme of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," "having" and "with" used herein are meant to be inclusive, not exclusive.

[0026] Some specific examples are listed below, it should be noted that the examples described below are exemplary, only for the purpose of explaining the present application, and can not be understood as limiting the present application. The technical or conditions not specified in the examples, according to the literature described in the art or according to the product specification. The reagents or instruments are not specified by the manufacturer, are the conventional products can be obtained by market.

[0027] I. Preparation method Example 1 A method for preparing a silver powder with a narrow particle size distribution, comprising the following steps: (1) Liquid preparation Solution A: Take 68g of silver nitrate into a beaker, add 500ml of deionized water and stir to dissolve, heat and keep at 25℃, get solution A; Solution B: Take 44g of ascorbic acid into a beaker, add 500ml of deionized water and stir to dissolve. After complete dissolution, get solution B; Solution C: Take 13.6g of polyvinylpyrrolidone (PVP) into a beaker, add 450ml of deionized water and stir to dissolve. After complete dissolution, get solution C; Among them, the technical index of PVP is: K value should be 32, moisture 3%, pH value 3, peroxide content 200 ppm, weight average molecular weight 40000;

[0028] Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol and stir to dissolve, get solution D. (2) Silver powder preparation a. Adjust the pH value of solution B to 5.5 using 10mol / L concentration of sodium hydroxide solution; b. Transfer solution A and half of solution C to the reaction kettle, heat to 60℃, start mechanical stirring, control the stirring rate between 400 r / min; c. Solution B is added to the reactor at a rate of 95 ml / min, and the feeding time is controlled between 3 min. When the silver ion concentration is reduced to 0.5 mol / L, the remaining half of solution C is added, and the temperature is reduced to 45°C for continued reaction. After the feeding is completed, the mixture is stirred for 5 min, and solution D is added, followed by continued stirring for 5 min, and the reaction is completed; d. The reaction suspension is allowed to settle, and the supernatant is poured out for solid-liquid separation. The silver powder is washed with deionized water and anhydrous ethanol, respectively, until the conductivity of the filtrate is <20 μS / m. The silver powder is dried in a blast drying oven at 60°C for 22 h.

[0029] Example 2 A method for preparing silver powder with a narrow particle size distribution. Compared with Example 1, the dispersant is also added in steps, but other production process parameters are changed. The specific steps include the following: (1) Solution preparation Solution A: 102 g of silver nitrate is taken into a beaker, and 500 ml of deionized water is added for stirring and dissolution. The temperature is raised and maintained at 25°C to obtain solution A. Solution B: 52.8 g of ascorbic acid is taken into a beaker, and 500 ml of deionized water is added for stirring and dissolution. After complete dissolution, solution B is obtained. Solution C: 5.1 g of polyvinylpyrrolidone (PVP) is taken into a beaker, and 450 ml of deionized water is added for stirring and dissolution. After complete dissolution, solution C is obtained. Among them, the technical index of PVP is that the K value should be 29, the moisture content is 4%, the pH value is 4, the peroxide is 100 ppm, and the weight average molecular weight is 20000; Solution D: 0.85 g of oleic acid is taken into a beaker, and 10 ml of anhydrous ethanol is added for stirring and dissolution to obtain solution D.

[0030] (2) Silver powder preparation a. The pH value of solution B is adjusted to 5.5 using a 10 mol / L sodium hydroxide solution; b. Solution A and half of solution C are transferred to the reactor, and the temperature is raised to 60°C. The mechanical stirring is started, and the stirring rate is controlled at 600 rpm; c. Solution B is added to the reactor at a rate of 95 ml / min, and the feeding time is controlled between 3 min. When the silver ion concentration is reduced to 0.5 mol / L, the remaining half of solution C is added, and the temperature is reduced to 45°C for continued reaction. After the feeding is completed, the mixture is stirred for 5 min, and solution D is added, followed by continued stirring for 5 min, and the reaction is completed; d. The reaction suspension is allowed to settle, and the supernatant is poured out for solid-liquid separation. The silver powder is washed with deionized water and anhydrous ethanol, respectively, until the conductivity of the filtrate is <20 μS / m. The silver powder is dried in a blast drying oven at 60°C for 22 h.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that solution C is added to the reaction kettle at one time, and the specific steps are as follows: (1) Liquid preparation Solution A: Take 85g of silver nitrate into a beaker, add 500ml of deionized water and stir to dissolve, and then heat and keep the temperature at 25℃ to obtain solution A; Solution B: Take 45.9g of ascorbic acid into a beaker, add 500ml of deionized water and stir to dissolve. After complete dissolution, solution B is obtained; Solution C: Take 11.9g of polyvinylpyrrolidone into a beaker, add 450ml of deionized water and stir to dissolve. After complete dissolution, solution C is obtained; Among them, the technical index of polyvinylpyrrolidone is that the K value should be 32, the moisture content is 3%, the pH value is 3, the peroxide content is equal to 400ppm, and the weight average molecular weight is 40000; Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol and stir to dissolve to obtain solution D.

[0032] (2) Silver powder preparation a. Adjust the pH value of solution B to 5.5 using a 10mol / L concentration of sodium hydroxide solution; b. Transfer solution A and solution C to the reaction kettle, start mechanical stirring, and control the stirring speed between 400r / min; c. Add solution B to the reaction kettle at a certain flow rate, control the feeding time to be 3min, after the feeding is completed, stir for 5min, and then add solution D and continue to stir for 5min, and the reaction is completed; d. The reaction suspension is settled, the supernatant is poured out, and solid-liquid separation is carried out. The silver powder is washed with deionized water and anhydrous ethanol respectively until the conductivity of the filtrate is <20μS / m, and then dried in a 60℃ air drying oven for 22h.

[0033] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that solutions A and B are added to solution C in stages, and the specific steps are as follows: (1) Liquid preparation Solution A: Take 85g of silver nitrate into a beaker, add 500ml of deionized water and stir to dissolve, and then heat and keep the temperature at 25℃ to obtain solution A; Solution B: Take 45.9g of ascorbic acid into a beaker, add 500ml of deionized water and stir to dissolve. After complete dissolution, solution B is obtained; Solution C: Take 11.9g of polyvinylpyrrolidone into a beaker, add 450ml of deionized water and stir to dissolve. After complete dissolution, solution C is obtained; The technical index of polyvinylpyrrolidone is that the K value should be 29, the moisture content is 4%, the pH value is 4, the peroxide content is equal to 100 ppm, and the weight average molecular weight is 20000; Solution D: Take 0.5g of oleic acid into a beaker, add 10ml of anhydrous ethanol, stir to dissolve, and get solution D.

[0034] (2) Silver powder preparation a. Adjust the pH value of solution B to 5.5 using a sodium hydroxide solution with a concentration of 10mol / L; b. Transfer solution C to the reaction kettle, start mechanical stirring, and control the stirring speed between 600 r / min; c. Simultaneously add solution A and solution B into the reaction kettle at a certain flow rate, the amount of solution A added is 50wt%, the amount of solution B added is 50wt%, the first stage feeding time is controlled to be 3min, after the first stage feeding is completed, continue to stir for 3min, then simultaneously add the remaining solution A and solution B into the reaction kettle, and finally add solution D after the feeding is completed, continue to stir for 5min, and the reaction is completed; d. Perform sedimentation on the reaction suspension, pour out the supernatant, perform solid-liquid separation, and wash the silver powder with deionized water and anhydrous ethanol respectively, wash until the conductivity of the filtrate is <20μS / m, and dry in a blast drying oven at 60℃ for 22h.

[0035] II. Test method 1. Particle size detection method: GB / T 19077-2016 "Particle size analysis laser diffraction method".

[0036] 2. SPAN detection method: calculated according to the particle size test results, the calculation method is SPAN=(D90-D10) / D50.

[0037] 3. Loose bulk density and tap density detection method: GB / T 1479.1-2011 Loose bulk density meter / funnel method; GB / T 5162-2021 Tap density meter / tap method.

[0038] 4. Specific surface area detection method: GB / T 13390-2008 Specific surface area analyzer / nitrogen adsorption method.

[0039] III. Analysis of test results of each embodiment and comparative example (1) The silver powder prepared in examples 1~2 and comparative examples 1~2 was subjected to SEM detection, and the results are as follows: Figures 1-4 As can be seen from the figure, the particle size distribution of the silver powder prepared in examples 1~2 is narrow, the particle size is uniform, and the sphericity is good. The particle size distribution of the silver powder prepared in comparative examples 1 and 2 is wide, and more large particle silver powder has poor sphericity.

[0040] (2) The silver powder prepared in Examples 1-2 and Comparative Examples 1-2 was subjected to particle size and density detection, and the detection results are shown in Table 1.

[0041] Table 1: Detection results of various physical data of the silver powder prepared in Examples 1-2 and Comparative Examples 1-2

[0042] As can be seen from Table 1, compared with Comparative Example 1, in Example 1, after the PVP feeding method was segmented and the reaction temperature was controlled, the silver powder had better dispersion effect, the SPAN value of the silver powder particle size distribution was reduced from 1.03 to 0.92, the distribution was narrower, the tap density result was larger, and the packing was tighter. In Comparative Example 2, the method of adding the oxidation liquid and the reducing liquid in sections was adopted, and the dispersion effect and particle size distribution of the produced silver powder were not as good as the method of PVP segmented addition and temperature control. The reason is that when the PVP is added in sections, the reactants are mixed rapidly and react rapidly, explosive nucleation occurs, and a large number of primary particles are generated. This process consumes a large amount of solute. After that, the concentration of the reactants is greatly reduced, and the reaction rate is slowed down, entering the process of not nucleating but only growing, so that the nucleation and growth processes are basically separated. Because the solute concentration is high at the beginning of the reaction, a large number of primary particles tend to grow into spherical particles by aggregation, and the dispersion effect of PVP and temperature control during the growth process inhibit excessive nucleation at high temperature, so that silver powder with good dispersion can be finally prepared. When the oxidation liquid and the reducing liquid are added in sections into the PVP, the concentration of silver ions and ascorbic acid in the reaction system is maintained at a relatively low level, the reaction rate is slow, and the solute concentration in the solution is very low, the nucleation rate and the growth rate are both small. Under this condition, the growth of silver particles tends to be diffusion growth, and the uniformity of silver powder is poor.

[0043] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other ways constructed by combining part of the components in the embodiments are also included in the scope of the present application.

Claims

1. A method for producing silver powder having a narrow particle size distribution, characterized by, The method comprises the following steps: dispersing silver nitrate in deionized water to obtain solution A; dispersing a reducing agent in deionized water to obtain solution B; dispersing a dispersing agent in deionized water to obtain solution C; dispersing a coating agent in anhydrous ethanol to obtain solution D; mixing solution A and a set amount of solution C, and heating to 60-70°C to obtain a mixed solution, and adding solution B into the mixed solution at a set flow rate, and stirring to react; When Ag in the mixture + Concentration reduced to initial Ag + When the concentration is 40% to 60%, add the remaining solution C, lower the temperature of the mixture to 40 to 50°C, and continue to add solution B at the set flow rate until the addition is complete to obtain the reaction solution; adding solution D into the reaction solution, and after the reaction is completed, performing solid-liquid separation and cleaning to obtain silver powder with narrow particle size distribution.

2. The method of claim 1, wherein the silver powder having a narrow particle size distribution is prepared by adding the silver salt to the solvent and the reducing agent. The concentration of silver nitrate in solution A is 0.8-1.2 mol / L.

3. The method of claim 1, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The concentration of the reducing agent in solution B is 0.5-0.6 mol / L, and the reducing agent comprises at least one of ascorbic acid, glucose, formaldehyde, triethanolamine and hydrazine hydrate.

4. The method of claim 1, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The dispersing agent in solution C accounts for 5%-20% of the mass of silver nitrate, and the dispersing agent is at least one of PVP, gelatin and polyethylene glycol.

5. The method of claim 4, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The K value of the PVP is 31.5-33, the moisture content is less than 4%, the pH value is 3-4, the peroxide content is less than or equal to 200 mg / L, and the weight average molecular weight is 25000-40000.

6. The method of claim 1, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The coating agent comprises at least one of oleic acid, lauric acid, stearic acid and palmitic acid, and the mass ratio of the coating agent to silver nitrate is (0.8-1.2):

100.

7. The method of claim 1, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The pH of solution B is adjusted to 4-6 by using lye.

8. The method of claim 1, wherein the silver powder has a narrow particle size distribution. The addition amount of the set amount of solution C is 40-60 wt%.

9. The method of claim 1, wherein the silver powder has a particle size distribution of 0.1 to 0.5 μm. The set flow rate of solution B added into the mixed solution is 95 mL / min.

10. A silver powder having a narrow particle size distribution, characterized in that, The silver powder is prepared by using the preparation method in any one of claims 1-9. The silver powder is prepared by using the preparation method in any one of claims 1-9.

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