Reduction device for continuously preparing superfine silver powder and continuous preparation method of superfine silver powder

Abstract

The invention provides a reduction device for continuously preparing superfine silver powder and a continuous preparation method of the superfine silver powder, and belongs to the technical field of silver powder preparation. The reduction device comprises a reaction shell and a temperature adjusting component wrapping the reaction shell; the upper end of the reaction shell is provided with a feeding hole part for independently feeding a plurality of raw materials; a discharge hole part is arranged at the lower end of the reaction shell; a snake-shaped reaction pipeline is arranged in the reaction shell, the snake-shaped reaction pipeline comprises a plurality of horizontal pipelines which are arranged at intervals in the height direction of the reaction shell, and one ends of every two adjacent horizontal pipelines are connected through a V-shaped corner; the upper end of the snake-shaped reaction pipeline is connected with the feed port component, and the lower end of the snake-shaped reaction pipeline is connected with the discharge port component; and the temperature adjusting part adjusts the reaction temperature in the snake-shaped reaction pipeline through flowing liquid. Continuous production of the superfine silver powder with the uniform particle size can be achieved, the yield is high, and the service life of the reaction pipeline is long.

Description

Technical Field

[0001] This invention belongs to the field of silver powder preparation technology, and particularly relates to a reduction device for continuous preparation of ultrafine silver powder and a continuous preparation method for ultrafine silver powder. Background Technology

[0002] Ultrafine silver powder possesses excellent electrical and thermal conductivity, chemical stability, and good processing properties, making it widely used in electronics, electrical appliances, electroplating, chemicals, and medical fields. Ultrafine silver powder refers to ultrafine silver powder with a silver content of 99.95% or higher. It is a high-purity ultrafine silver powder with a particle size range typically between 0.5 and 4.0 μm. Different particle size ranges are used in different fields, such as solders, contacts, jewelry, catalysts, medical applications, and electronic pastes. Furthermore, it is a major component of the silver paste on the front side of the metal electrode in crystalline silicon solar cells.

[0003] Ultrafine silver powder is typically prepared using the traditional liquid-phase reduction method. This involves adding an alkali solution and a reducing agent to a soluble silver salt solution under specific stirring conditions. After a period of reaction, the ultrafine silver powder is washed with pure water, separated from the liquid, dispersed using a disperser, and finally dried in an oven. This process offers numerous advantages, including low manual operation, low cost, simple equipment, and ease of large-scale industrial production. Furthermore, different reduction reaction parameters can produce ultrafine silver powder with varying particle morphologies and sizes. However, while the traditional liquid-phase reduction method has many advantages, it is primarily a batch process, resulting in low production efficiency, small output, and high labor intensity.

[0004] Continuous production methods offer advantages such as high efficiency, large output, and low labor intensity; however, existing continuous production methods are performed in circular pipelines (e.g.,...). Figure 1 The reaction is completed in the ring pipe. Because the reaction material flows without resistance in the ring pipe, it is impossible to ensure that the reaction raw materials are mixed evenly or that the stirring intensity required for the entire reaction process is guaranteed. As a result, the silver powder particles cannot be fully dispersed and grown during the reaction, resulting in poor particle size uniformity of ultrafine silver powder, low yield, and severe corrosion of the ring pipe, resulting in a short service life. Summary of the Invention

[0005] One of the objectives of this invention is to provide a reduction device for the continuous preparation of ultrafine silver powder. This reduction device can achieve continuous production of ultrafine silver powder with uniform particle size, and has high yield, high output, low operating intensity, high silver powder quality stability, high quality, and long service life of the reaction pipeline.

[0006] The second objective of this invention is to provide a continuous preparation method for ultrafine silver powder.

[0007] To achieve one of the above objectives, the present invention employs the following technical solution:

[0008] A reduction apparatus for the continuous preparation of ultrafine silver powder, the reduction apparatus comprising a reaction shell and a temperature control component wrapped around the outside of the reaction shell;

[0009] The upper end of the reaction shell is provided with an inlet component for independently feeding multiple raw materials; the lower end of the reaction shell is provided with an outlet component.

[0010] The reaction shell is provided with a "snake" shaped reaction pipe, which includes multiple horizontal pipes arranged at intervals along the height direction of the reaction shell. One end of two adjacent horizontal pipes is connected by a V-shaped bend. The upper end of the "snake" shaped reaction pipe is connected to the feed inlet component, and the lower end of the "snake" shaped reaction pipe is connected to the discharge outlet component.

[0011] The temperature control component regulates the reaction temperature within the "snake"-shaped reaction pipe by flowing liquid.

[0012] Furthermore, the "snake"-shaped reaction pipeline includes a liquid preheating and mixing section, a liquid reaction section, and a liquid discharge section connected in sequence. The liquid preheating and mixing section is connected to the inlet component, and the liquid discharge section is connected to the outlet component.

[0013] The angles of the corners in the liquid preheating and mixing section, the liquid reaction section, and the liquid discharge section are 55–65°, 35–45°, and 75–85°, respectively.

[0014] Furthermore, the ratio of the pipe lengths of the liquid preheating and mixing section, the liquid reaction section, and the liquid discharge section is 1-2:150-200:1-2.

[0015] Furthermore, the temperature regulating component is a U-shaped jacket;

[0016] The inlet and outlet of the U-shaped jacket are both located at the upper part of the reaction shell.

[0017] Furthermore, the feed inlet component is a four-way valve;

[0018] The three pipe inlets on the same side of the four-way valve are located outside the reaction shell and are respectively connected to the silver nitrate solution pipe, the reducing agent pipe, and the alkali solution pipe;

[0019] The pipe outlet on the other side of the four-way valve is located inside the reaction housing and is connected to the "snake" shaped reaction pipe.

[0020] Furthermore, the discharge port component is a ball valve.

[0021] Furthermore, the flowing liquid is water.

[0022] To achieve the second objective mentioned above, the present invention employs the following technical solution:

[0023] A continuous preparation method for ultrafine silver powder, wherein the continuous preparation method uses the reduction apparatus described above and includes the following steps:

[0024] Step S1: Prepare silver nitrate solution, alkali solution and reducing agent solution, and put them into silver nitrate solution constant temperature tank, alkali solution constant temperature tank and reducing agent solution constant temperature tank respectively, and keep them at 25-35℃.

[0025] Step S2: Continuously introduce a flowing liquid at a temperature of 45-50°C into the temperature control component to maintain the temperature of the "snake"-shaped reaction pipe located in the reaction shell.

[0026] Step S3: Control the silver nitrate solution, alkaline solution and reducing agent solution to flow continuously into the feed inlet component at the same time through their respective corresponding pipes at a flow rate ratio of 38-42:3.8-4.2:1, then into the "snake" shaped reaction pipe, and finally out through the discharge outlet component to obtain ultrafine silver powder slurry;

[0027] Step S4: The ultrafine silver powder slurry is washed, dispersed and dried in sequence to obtain ultrafine silver powder.

[0028] Furthermore, in step S1, the mass-volume concentration of the silver nitrate solution is 1.1–1.4 g / cm³. 3 ;

[0029] The mass concentrations of the alkaline solution and the reducing agent solution are 30-50% and 30-40%, respectively.

[0030] Furthermore, in step S1, the alkaline solution includes either a sodium hydroxide solution or a sodium carbonate solution;

[0031] The reducing agent includes one or more of glucose, lactic acid, sucrose, and formaldehyde.

[0032] In summary, the technical solution of the present invention has the following technical effects:

[0033] This invention utilizes the vortex generated by the resistance at the corner of the "snake"-shaped reaction pipe to achieve the mixing effect without the need for additional stirring equipment, ensuring thorough mixing and reaction of materials, improving the uniformity of ultrafine silver powder particle size, and achieving high output, low cost, low labor intensity, and simple operation; the ultrafine silver powder of this invention has good quality consistency and excellent performance.

[0034] Furthermore, by using a temperature-regulating component located outside the reaction shell, this invention achieves constant temperature control of the reactants within the reaction pipeline, meeting the temperature requirements for full reaction of the materials. At the same time, it avoids corrosion caused by prolonged immersion of the reaction pipeline in flowing liquid, extends the service life of the reaction pipeline, and reduces production costs. Attached Figure Description

[0035] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of an existing ring-shaped pipe structure;

[0037] Figure 2 This is a schematic diagram of a reduction apparatus for the continuous preparation of ultrafine silver powder according to an embodiment of the present invention;

[0038] In the diagram: 1—Silver nitrate solution constant temperature tank, 2—Alkali solution constant temperature tank, 3—Reducing agent constant temperature tank, 4—Reaction shell, 5—"Snake" shaped reaction pipeline, 6—Corner, 7—Inlet component, 8—Outlet component, 9—Liquid inlet, 10—Preheating and mixing section of liquid, 11—Reaction section of liquid, 12—Discharge section of liquid, 13—Liquid outlet. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This embodiment provides a reduction apparatus for the continuous preparation of ultrafine silver powder, referencing... Figure 2 The reduction device includes a reaction shell 4 and a temperature control component (not shown in the figure) that surrounds the reaction shell 4. By placing the temperature control component outside the reaction shell 4, constant temperature control of the reaction pipeline is achieved, ensuring that the temperature inside the reaction pipeline meets the temperature requirements for sufficient material reaction. At the same time, it avoids corrosion of the "snake-shaped" reaction pipeline caused by prolonged immersion of the reaction pipeline in the flowing liquid inside the temperature control component, thus extending the service life of the reaction pipeline and reducing production costs.

[0041] In this embodiment, the temperature control component regulates the reaction temperature within the "snake"-shaped reaction pipe 5 via an internal flowing liquid (typically water). The temperature control component in this embodiment is a U-shaped jacket, with its inlet 9 and outlet 13 both located at the upper part of the reaction shell 4. This ensures that the temperature of the raw material remains constant at 45–50°C (i.e., the temperature of the flowing liquid) throughout the entire process from entering the "snake"-shaped reaction pipe to flowing out, resulting in more complete and efficient oxidation-reduction, thereby improving the yield and quality rate of the oxidation-reduction product (i.e., ultrafine silver powder).

[0042] In this embodiment, the upper end of the reaction shell 4 is provided with an inlet component 7 for feeding multiple raw materials independently, and the lower end of the reaction shell 4 is provided with an outlet component 8.

[0043] In this embodiment, a serpentine reaction pipe 5 is provided inside the reaction shell 4. This serpentine reaction pipe 5 includes multiple horizontal pipes spaced apart along the height of the reaction shell 4, with one end of each adjacent horizontal pipe connected by a V-shaped bend 6. The upper end of the serpentine reaction pipe 5 is connected to the inlet component 7, and the lower end is connected to the outlet component 8. The serpentine reaction pipe 5 includes a liquid preheating and mixing section 10, a liquid reaction section 11, and a liquid discharge section 12 connected in sequence. The liquid preheating and mixing section 10 is connected to the inlet component 7, and the liquid discharge section 12 is connected to the outlet component 8. In this embodiment, the vortex generated by the resistance at the corner 6 on the "snake"-shaped reaction pipe 5 ensures that the reaction raw materials (i.e., the silver nitrate solution stored in the silver nitrate solution constant temperature tank 1, the alkali solution stored in the alkali solution constant temperature tank 2, and the reducing agent solution stored in the reducing agent constant temperature tank 3) flow from the inlet component 7 to the outlet component 8 without the need for additional stirring equipment. This ensures that the mixing process of the reaction raw materials and the redox reaction process are both under stirring, guaranteeing sufficient mixing and reaction of the raw materials, and realizing the continuous preparation of ultrafine silver powder with uniform particle size.

[0044] To further ensure thorough mixing and reaction of the materials and achieve continuous production of ultrafine silver powder with uniform particle size, in this embodiment, the corner angles 6 of the liquid preheating mixing section 10, the liquid reaction section 11, and the liquid discharge section 12 are 55-65°, 35-45°, and 75-85°, respectively.

[0045] To ensure thorough mixing and reaction of the raw materials while avoiding excessively long residence time that could lead to sedimentation and blockage of the pipes by silver powder particles, this embodiment sets the pipe length ratio of the liquid preheating mixing section 10, the liquid reaction section 11, and the liquid discharge section 12 to 1-2:150-200:1-2. The liquid preheating mixing section 10 and the liquid discharge section 12 each have 5-8 corners 6, while the liquid reaction section 11 has 40-60 corners 6.

[0046] In this embodiment, the feed inlet component 7 is a four-way valve. The three pipe inlets on the same side of the four-way valve are located outside the reaction shell 4 and are connected to the silver nitrate solution pipe, the reducing agent pipe, and the alkali solution pipe, respectively. The pipe outlet on the other side of the four-way valve is located inside the reaction shell 4 and is connected to the "snake"-shaped reaction pipe 5. In this embodiment, the discharge outlet component 8 is a ball valve.

[0047] To facilitate the control of the flow rate of each material (such as silver nitrate solution, alkali solution, and reducing agent solution), this embodiment is equipped with regulating valves (not shown in the figure) in the silver nitrate solution pipeline, reducing agent pipeline, and alkali solution pipeline.

[0048] To prevent pipe blockage caused by silver powder material due to prolonged use, this embodiment can clean the constant temperature tank of reducing agent solution, add concentrated nitric acid, and pass it into the "snake"-shaped reaction pipe 5. After heating and soaking for 12-24 hours through the temperature control component (not shown in the figure), it can be discharged from the discharge port component 8 and rinsed clean with pure water.

[0049] This embodiment utilizes the vortex generated by the resistance at the corner of the "snake"-shaped reaction pipe to achieve the mixing effect without the need for additional stirring equipment. This ensures thorough mixing and reaction of the materials, improves the uniformity of ultrafine silver powder particle size, and results in high output, low cost, low labor intensity, and simple operation. The ultrafine silver powder in this embodiment exhibits good consistency and excellent performance. Furthermore, by using a temperature control component located outside the reaction shell, this embodiment achieves constant temperature control of the reactants within the reaction pipe, meeting the temperature requirements for full reaction. This also prevents corrosion caused by prolonged immersion of the reaction pipe in flowing liquid, extends the service life of the reaction pipe, and reduces production costs.

[0050] Example 1:

[0051] Step S1: Prepare a mass-volume concentration of 1.2 g / cm³. 3 Silver nitrate solution, sodium hydroxide solution with a mass concentration of 40% and glucose with a mass concentration of 30% were respectively placed in a silver nitrate solution constant temperature tank, an alkali solution constant temperature tank and a reducing agent solution constant temperature tank, and kept at 30°C.

[0052] Step S2: By continuously supplying water at a temperature of 50°C into the temperature control component located outside the reaction shell, the temperature of the "snake" shaped reaction pipe located inside the reaction shell is kept constant.

[0053] Step S3: Control the silver nitrate solution, sodium hydroxide solution and glucose to flow continuously into the feed inlet component located at the upper end of the reaction shell through their respective corresponding pipes at a flow rate ratio of 40:4:1. Then, they pass through the preheating and mixing section, reaction section and discharge section of the "snake" shaped reaction pipe in sequence, and finally flow out through the discharge outlet component located at the lower end of the reaction shell to obtain ultrafine silver powder slurry.

[0054] The feed preheating and mixing section has 7 corners, the feed reaction section has 50 corners, and the feed discharge section has 6 corners. Each corner in the feed preheating and mixing section, the feed reaction section, and the feed discharge section has an angle of 60°, 40°, and 80°, respectively. The pipe length ratio of the feed preheating and mixing section, the feed reaction section, and the feed discharge section is 2:200:1.

[0055] Step S4: The ultrafine silver powder slurry is washed, dispersed and dried in sequence to obtain ultrafine silver powder.

[0056] In this embodiment, a single redox device can produce 410 kg of ultrafine silver powder per day, and the average particle size of the ultrafine silver powder is 1.8 μm.

[0057] Example 2:

[0058] Step S1: Prepare a mass-volume concentration of 1.4 g / cm³. 3 Silver nitrate solution, sodium carbonate solution with a mass concentration of 50%, and lactic acid with a mass concentration of 35% were respectively placed into a silver nitrate solution constant temperature tank, an alkali solution constant temperature tank, and a reducing agent solution constant temperature tank, and kept at a constant temperature of 25°C.

[0059] Step S2: By continuously supplying water at a temperature of 45°C into the temperature control component located outside the reaction shell, the temperature of the "snake" shaped reaction pipe located inside the reaction shell is kept constant.

[0060] Step S3: Control the silver nitrate solution, sodium hydroxide solution and glucose to flow continuously into the feed inlet component located at the upper end of the reaction shell through their respective corresponding pipes at a flow rate ratio of 42:4.2:1. Then, they sequentially pass through the preheating and mixing section, reaction section and discharge section of the "snake" shaped reaction pipe, and finally flow out through the discharge outlet component located at the lower end of the reaction shell to obtain ultrafine silver powder slurry.

[0061] The feed preheating and mixing section has 8 corners, the feed reaction section has 60 corners, and the feed discharge section has 8 corners. Each corner in the feed preheating and mixing section, the feed reaction section, and the feed discharge section has an angle of 65°, 45°, and 85°, respectively. The pipe length ratio of the feed preheating and mixing section, the feed reaction section, and the feed discharge section is 1:150:2.

[0062] Step S4: The ultrafine silver powder slurry is washed, dispersed and dried in sequence to obtain ultrafine silver powder.

[0063] In this embodiment, a single redox device can produce 420 kg of ultrafine silver powder per day, and the average particle size of the ultrafine silver powder is 2.3 μm.

[0064] Example 3:

[0065] Step S1: Prepare a mass-volume concentration of 1.1 g / cm³. 3 Silver nitrate solution, sodium carbonate solution with a mass concentration of 30%, and sucrose solution with a mass concentration of 4% were respectively placed in a silver nitrate solution constant temperature tank, an alkali solution constant temperature tank, and a reducing agent solution constant temperature tank, and kept at a constant temperature of 35°C.

[0066] Step S2: By continuously supplying water at a temperature of 48°C into the temperature control component located outside the reaction shell, the temperature of the "snake" shaped reaction pipe located inside the reaction shell is kept constant.

[0067] Step S3: Control the silver nitrate solution, sodium hydroxide solution and glucose to flow continuously into the feed inlet component located at the upper end of the reaction shell through their respective corresponding pipes at a flow rate ratio of 38:3.8:1. Then, they sequentially pass through the preheating and mixing section, reaction section and discharge section of the "snake" shaped reaction pipe, and finally flow out through the discharge outlet component located at the lower end of the reaction shell to obtain ultrafine silver powder slurry.

[0068] The feed preheating and mixing section has 5 corners, the feed reaction section has 40 corners, and the feed discharge section has 5 corners. Each corner in the feed preheating and mixing section, the feed reaction section, and the feed discharge section has an angle of 55°, 35°, and 75°, respectively. The pipe length ratio of the feed preheating and mixing section, the feed reaction section, and the feed discharge section is 2:180:1.

[0069] Step S4: The ultrafine silver powder slurry is washed, dispersed and dried in sequence to obtain ultrafine silver powder.

[0070] In this embodiment, a single redox device can produce 400 kg of ultrafine silver powder per day, and the average particle size of the ultrafine silver powder is 1.4 μm.

[0071] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A reduction apparatus for the continuous preparation of ultrafine silver powder, characterized in that, The reduction device includes a reaction shell and a temperature control component that surrounds the outside of the reaction shell; The upper end of the reaction shell is provided with an inlet component for independently feeding multiple raw materials; the lower end of the reaction shell is provided with an outlet component. The reaction shell is provided with a "snake" shaped reaction pipe, which includes multiple horizontal pipes arranged at intervals along the height direction of the reaction shell. One end of two adjacent horizontal pipes is connected by a V-shaped bend. The upper end of the "snake" shaped reaction pipe is connected to the feed inlet component, and the lower end of the "snake" shaped reaction pipe is connected to the discharge outlet component. The temperature control component regulates the reaction temperature within the "snake"-shaped reaction pipe by flowing liquid.

2. The reduction apparatus according to claim 1, characterized in that, The "snake"-shaped reaction pipeline includes a liquid preheating and mixing section, a liquid reaction section, and a liquid discharge section connected in sequence. The liquid preheating and mixing section is connected to the inlet component, and the liquid discharge section is connected to the outlet component. The angles of the corners in the liquid preheating and mixing section, the liquid reaction section, and the liquid discharge section are 55–65°, 35–45°, and 75–85°, respectively.

3. The reduction apparatus according to claim 2, characterized in that, The ratio of the pipe lengths of the liquid preheating and mixing section, the liquid reaction section, and the liquid discharge section is 1-2:150-200:1-2.

4. The reduction apparatus according to any one of claims 1 to 3, characterized in that, The temperature regulating component is a U-shaped jacket; The inlet and outlet of the U-shaped jacket are both located at the upper part of the reaction shell.

5. The reduction apparatus according to claim 4, characterized in that, The feed inlet component is a four-way valve; The three pipe inlets on the same side of the four-way valve are located outside the reaction shell and are respectively connected to the silver nitrate solution pipe, the reducing agent pipe, and the alkali solution pipe; The pipe outlet on the other side of the four-way valve is located inside the reaction housing and is connected to the "snake" shaped reaction pipe.

6. The reduction apparatus according to claim 5, characterized in that, The discharge port component is a ball valve.

7. The reduction apparatus according to claim 6, characterized in that, The flowing liquid is water.

8. A continuous preparation method for ultrafine silver powder, characterized in that, The continuous preparation method uses the reduction apparatus described in any one of claims 1 to 7, and includes the following steps: Step S1: Prepare silver nitrate solution, alkali solution and reducing agent solution, and put them into silver nitrate solution constant temperature tank, alkali solution constant temperature tank and reducing agent solution constant temperature tank respectively, and keep them at 25-35℃. Step S2: Continuously introduce a flowing liquid at a temperature of 45-50°C into the temperature control component to maintain the temperature of the "snake"-shaped reaction pipe located in the reaction shell. Step S3: Control the silver nitrate solution, alkaline solution and reducing agent solution to flow continuously into the feed inlet component at the same time through their respective corresponding pipes at a flow rate ratio of 38-42:3.8-4.2:1, then into the "snake" shaped reaction pipe, and finally out through the discharge outlet component to obtain ultrafine silver powder slurry; Step S4: The ultrafine silver powder slurry is washed, dispersed and dried in sequence to obtain ultrafine silver powder.

9. The continuous preparation method according to claim 8, characterized in that, In step S1, the mass-volume concentration of the silver nitrate solution is 1.1–1.4 g / cm³. 3 ; The mass concentrations of the alkaline solution and the reducing agent solution are 30-50% and 30-40%, respectively.

10. The continuous preparation method according to claim 9, characterized in that, In step S1, the alkaline solution includes either a sodium hydroxide solution or a sodium carbonate solution; The reducing agent includes one or more of glucose, lactic acid, sucrose, and formaldehyde.

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