Method and device for preparing metal powder using high-dispersion synthesis reactor

Abstract

The present invention provides a method for preparing metal powder by using a high-dispersion synthesis reactor and a high-dispersion metal powder preparation device. The method comprises: adding a base liquid into a circulation regulating reactor, and performing internal and external circulation through a high-dispersion synthesis reactor connected to the circulation regulating reactor to achieve a stable circulation; after the stable circulation meets the predetermined requirements, continuously adding an oxidizing liquid and a reducing liquid into the high-dispersion synthesis reactor for a synthesis reaction, during the synthesis reaction, the reaction liquid is continuously sent into the high-dispersion synthesis reactor for forced dispersion, and performs a synthesis reaction therein with the oxidizing liquid and reducing liquid that are continuously newly added to the high-dispersion synthesis reactor; sampling analysis and testing are performed, and when the particle size of the metal powder generated by the synthesis reaction meets the requirements, the addition of the oxidizing liquid and the reducing liquid is stopped to stop the synthesis reaction; after the reaction liquid is discharged from the circulation regulating reactor, solid-liquid separation, cleaning, post-treatment, and drying are performed to obtain a highly dispersed metal powder.

Description

Technical Field

[0001] The invention relates to the technical field of synthetic metal powders, and in particular to a method for preparing metal powders by utilizing a high-dispersion synthesis reactor and a device for preparing high-dispersion metal powders. Background Art

[0002] The dispersibility, particle size distribution and particle uniformity of metal powder synthesized by chemical reduction method have a decisive influence on the performance of metal powder. The production equipment and synthesis process of metal powder affect the morphology, dispersibility, particle size distribution, width and other parameters of metal powder, and ultimately affect its application performance. The high-performance metal powder used in the photovoltaic industry must have the characteristics of excellent dispersion, concentrated particle size distribution and high sphericity.

[0003] At present, the existing method for preparing metal powder is basically to synthesize the metal powder by placing an oxidizing solution, a reducing solution and / or a dispersing solution in the same reactor; during the synthesis process, the type and stirring speed of the agitator and / or ultrasonic device on the reactor are generally controlled to make the reaction liquid as uniform as possible. This method has obvious defects.

[0004] Due to the large volume of the production reactor, there are dead corners for stirring, and the distance attenuation of ultrasonic intensity, the agglomerated powder produced in the reaction system cannot be deagglomerated in time, and silver particles are easy to grow on the agglomerated powder to produce irregular particles; the concentration and pH value of the dispersant in the reaction system are constantly changing with the progress of the reaction, and this change will cause problems such as poor dispersion of metal particles, low sphericity, excessive irregular powder, and wide particle size distribution. The slurry prepared directly using this powder is prone to poor printing, uneven lines, poor electrical performance, etc. during the printing process, and various powder post-treatments are required to achieve better application performance. Summary of the invention

[0005] In order to solve the above-mentioned existing technical problems or part thereof, the object of the present invention is to provide a method for preparing metal powder using a high-dispersion synthesis reactor and a high-dispersion metal powder preparation device, which uses a high-dispersion synthesis reactor with a forced external circulation having a high-dispersion function and in such a small reaction vessel IB2024BC0052Y (OA1)

[0006] The reaction synthesis is carried out in the device to prepare metal powder with high dispersion, narrow particle size distribution and high uniformity.

[0007] According to one aspect of the present invention, there is provided a method for preparing metal powder using a high-dispersion synthesis reactor, the method comprising the following steps:

[0008] Step (1) adding the bottom liquid into a circulation regulating reactor, and performing internal and external circulation through a high-dispersion synthesis reactor connected to the circulation regulating reactor to achieve a stable circulation;

[0009] Step (2) after the stable circulation meets the predetermined requirements, the oxidizing liquid and the reducing liquid are continuously added to the high-dispersion synthesis reactor to carry out a synthesis reaction and generate a reaction liquid. During the synthesis reaction, the reaction liquid is continuously sent to the high-dispersion synthesis reactor for forced dispersion, and the synthesis reaction is carried out therein with the oxidizing liquid and the reducing liquid that are continuously newly added to the high-dispersion synthesis reactor;

[0010] Step (3) sampling, analyzing and testing are performed during the synthesis reaction. When the particle size of the metal powder generated by the synthesis reaction meets the requirements, the addition of the oxidizing liquid and the reducing liquid is stopped to stop the synthesis reaction;

[0011] Step (4) After the reaction liquid is discharged from the circulation regulating reactor, it is subjected to solid-liquid separation, washing, post-treatment and drying to obtain highly dispersed metal powder.

[0012] According to a second aspect of the present invention, there is provided a device for preparing highly dispersed metal powder using the above method, comprising:

[0013] Circulation adjustment reactor;

[0014] A high-dispersion synthesis reactor, wherein the high-dispersion synthesis reactor is connected to a circulation regulating reactor pipeline, and the bottom liquid or the reaction liquid is forcibly dispersed in the high-dispersion synthesis reactor;

[0015] The circulation device is connected to the circulation regulating reactor and the high-dispersion synthesis reactor pipeline respectively, so that the base liquid or the reaction liquid can be continuously circulated in the high-dispersion metal powder preparation device.

[0016] The method for preparing metal powder by using a high-dispersion synthesis reactor and the device for preparing high-dispersion metal powder according to the embodiments of the present invention have at least one of the following advantages or part of one of the advantages:

[0017] 1. The oxidizing liquid and reducing liquid are passed through a small high-dispersion synthesis reactor for synthesis reaction, and the liquid after the reaction is sent to a circulation adjustment reactor for reaction parameter adjustment. The adjusted reaction liquid is recycled and sent to the high-dispersion synthesis reactor to react with the newly added oxidizing liquid and reducing liquid until the particle size of the prepared metal powder reaches the target value. The circulating adjustment reactor is added with dispersion liquid and / or pH regulator under stirring to ensure that the reduction reaction is carried out at a basically constant dispersant concentration and pH value, so as to achieve the synthesis of highly dispersed and highly uniform metal powder. This method has good repeatability and strong operability. The metal powder prepared by this method has the advantages of high dispersion, narrow particle size distribution and high uniformity, which solves the shortcomings of existing metal powders such as poor dispersibility, wide particle size distribution and poor uniformity; it is suitable for conductive slurries, conductive adhesives and other fields that have high requirements for the dispersibility, particle size distribution and uniformity of metal powders.

[0018] 2. The growth of silver powder is carried out in a small-scale highly dispersed synthesis reactor. After the silver powder particles synthesized in the small-scale highly dispersed reactor are refluxed into the circulation adjustment reactor and various parameters are adjusted, they are sent to the small-scale highly dispersed synthesis reactor again to participate in the synthesis. The silver particles contained in the reaction liquid sent to the small-scale highly dispersed synthesis reactor will participate in the further synthesis and growth of silver powder in the small-scale highly dispersed synthesis reactor as crystal nuclei. During the production process, the quantitative ratio between the silver powder as the crystal nucleus and the oxidizing liquid and the reducing liquid is adjusted by controlling the flow rate of the adjusted mixed reaction liquid containing particles entering the small-scale highly dispersed synthesis reactor, and the generation of silver powder is further controlled, thereby ensuring the achievement of product goals.

[0019] 3. The technology of the present invention utilizes the characteristics of a small-scale high-dispersion synthesis reactor, which has small volume, strong dispersion and stirring, and no dead corners, thereby avoiding the agglomeration of silver powder during the silver powder synthesis reaction.

[0020] 4. The silver particles formed after the mixed reaction of the oxidizing solution and the reducing solution will continue to participate in the next cycle of synthesis reaction as seeds. The newly generated silver particles will grow and adjust the microcrystalline morphology on the original silver particles, and the cycle will be repeated until the particle size of the silver powder meets the requirements. Using this method, when synthesizing silver powder, in addition to adjusting the parameters of the oxidizing solution and the reducing solution to control the particle size of the silver powder, the particle size and morphology of the silver powder can also be controlled by controlling the amount of silver source during the reaction cycle.

[0021] 5. The present invention uses a small high-dispersion synthesis reactor and a large circulation regulating reactor to work together to achieve large-scale production and reduce the amplification effect of production. The use of a small high-dispersion synthesis reactor is mainly to fully ensure the dispersion and uniformity of the silver powder due to its small size and the absence of a stirring dead angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0023] Figure 1 A flow chart of a method for preparing metal powder using a high-dispersion synthesis reactor according to one embodiment of the present invention;

[0024] Figure 2 It is a schematic structural diagram of a device for preparing highly dispersed metal powder according to another embodiment of the present invention;

[0025] Figure 3-Figure 7 is a scanning electron microscope image of the silver powder prepared according to the method shown in Examples 1-5 of the present invention;

[0026] Figure 8-Figure 9 is a scanning electron microscope image of the silver powder prepared according to the method shown in Comparative Example 1-2 of the present invention. DETAILED DESCRIPTION

[0027] The features of the present invention are further described below through specific embodiments. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall concept of the present invention and should not be construed as a limitation of the present invention.

[0028] See also Figure 1 , shows a flow chart of a method for preparing metal powder using a high-dispersion synthesis reactor according to an embodiment of the present invention. As shown in the figure, the preparation method mainly includes the following four steps.

[0029] Specifically, the method comprises the following steps:

[0030] Step (1) adding the bottom liquid into a circulation regulating reactor, and performing internal and external circulation through a high-dispersion synthesis reactor connected to the circulation regulating reactor to achieve a stable circulation;

[0031] Step (2) after the stable circulation meets the predetermined requirements, the oxidizing liquid and the reducing liquid are continuously added to the high-dispersion synthesis reactor for synthesis reaction. During the synthesis reaction, the reaction liquid is continuously sent to the high-dispersion synthesis reactor for forced dispersion, and the synthesis reaction is carried out therein with the oxidizing liquid and the reducing liquid that are continuously newly added to the high-dispersion synthesis reactor;

[0032] Step (3) sampling, analyzing and testing are performed during the synthesis reaction. When the particle size of the metal powder generated by the synthesis reaction meets the requirements, the addition of the oxidizing liquid and the reducing liquid is stopped to stop the synthesis reaction;

[0033] Step (4) After the reaction liquid is discharged from the circulation regulating reactor, it is subjected to solid-liquid separation, washing, post-treatment and drying to obtain highly dispersed metal powder.

[0034] The high dispersion in the present application can refer to any of the following two types: one is that when observed under a scanning electron microscope, there are basically no more than two single silver powder particles bonded together in the silver powder, and the particle size distribution of the silver powder is uniform; the other is measured by the particle size distribution width, which is measured by testing the particle size D10, D50, and D90 on a laser diffraction particle size analyzer, and then calculated according to the following formula: particle size distribution width = (D90-D10) / D50. When the value is below 1, it means that the silver powder is basically not agglomerated, and the particle size of the silver powder is uniform, and the dispersion of the silver powder is high, which is high dispersion. When it is between 1 and 1.2, it is relatively high dispersion, and when it is greater than 1.2, it means that the dispersion of the silver powder is poor, the particle size of the silver powder is uneven, the distribution is wide, or the silver powder is seriously agglomerated.

[0035] The "post-treatment" mentioned here refers to coating the surface of the silver powder with a layer of organic matter to modify the surface of the powder. The organic matter can be one or a mixture of fatty acid salts, fatty acid ammonium amides, organic acids, fatty amines, fatty enamines, surfactants, and organosilicon compounds.

[0036] As discussed in the background technology section of the present invention, in order to at least partially solve the proposed technical problem, the solution adopted in the embodiment of the present invention is: the oxidizing liquid and the reducing liquid are passed through a small-scale high-dispersion synthesis reactor (for example, with an ultrasonic device and / or a shearing disperser) for synthesis reaction, and the reaction liquid after the reaction is sent to a circulation adjustment reactor for reaction parameter adjustment. The adjusted reaction liquid is recycled and sent to the small-scale high-dispersion synthesis reactor to react with the newly added oxidizing liquid and reducing liquid until the particle size of the prepared metal powder reaches the target value.

[0037] The circulating regulating reactor is added with dispersion liquid and / or pH regulator or regulating liquid under stirring conditions to ensure that the reduction reaction is carried out at a substantially constant dispersant concentration and pH value, thereby achieving the synthesis of highly dispersed and highly uniform metal powders.

[0038] Due to the small volume of the small high-dispersion synthesis reactor, the problem of ultrasonic power attenuation caused by distance can be effectively solved, and the dispersion dead corner of the shear disperser in the large-volume reactor can also be fully solved.

[0039] The speed of the redox reaction is very fast. When the reaction liquid leaves the small-scale high-dispersion synthesis reactor, the synthesis reaction has been completed to generate metal particles. When the reaction liquid containing metal particles is sent to the circulation adjustment reactor to adjust the dispersant concentration and pH value and then sent to the small-scale high-dispersion synthesis reactor, the metal particles in the reaction liquid can be regarded as seeds that are further grown. As the cycle continues, the particle size can grow to the required size.

[0040] First, I will introduce the preparation of the base liquid (or dispersion liquid), pH adjustment liquid, oxidizing liquid, and reducing liquid. I will not introduce them in detail later.

[0041] 1. Preparation of oxidizing solution: Add a certain amount or a predetermined amount of metal salt to a certain amount of pure water, stir and dissolve, and keep the temperature at 15°C-45°C. The metal salt in the oxidizing solution includes any one of oxalates, carbonates, sulfates, citrates, nitrates, metal oxides, and metal ammonia complexes, or any combination thereof. The concentration of the metal salt is 30g / L-300g / L, preferably 120g / L-240g / L. In one example, when preparing the oxidizing solution with silver nitrate, ammonia water can also be added to prepare it into a silver ammonia complex solution for use.

[0042] 2. Preparation of reducing solution: Add a certain amount or a predetermined amount of reducing agent to a certain amount of pure water, stir and dissolve, and keep the temperature at 15°C-45°C. The reducing agent in the reducing solution includes any one of hydrazine hydrate, formaldehyde, formic acid, ammonium formate, ascorbic acid, hydrogen peroxide, triethanolamine, glycerol, glucose, hydroxylamine or any combination thereof. The concentration of the reducing agent is 20g / L-200g / L, preferably 50g / L-150g / L.

[0043] 3. Preparation of dispersion: Add a certain amount or a predetermined amount of dispersant into a certain amount of pure water, stir and dissolve, and keep the temperature at 15℃-45℃. The dispersant in the dispersion includes polyvinyl alcohol, guar gum, Arabic IB2024BC0052Y (OA1)

[0044] Resin, polyvinyl pyrrolidone, fatty acid, copper nitrate, magnesium nitrate or any combination thereof. The concentration of the dispersant is 0g / L-500g / L, preferably 5g / L-100g / L.

[0045] 4. Preparation of acid-base regulating solution: It can be any one of ammonia water, ethanolamine, diethanolamine, triethanolamine, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc. or any combination thereof.

[0046] In step (3), an acid-base adjustment liquid is added according to the change of the pH value in the online monitoring reaction liquid; when the particle size requirement of the metal powder is reached, a surface coating treatment agent is added to the circulating adjustment reactor to treat the surface of the powder. The surface coating treatment agent refers to one or a mixture of several selected from the group consisting of fatty acid salts, fatty acid amides, organic acids, fatty amines, fatty enamines, surfactants, and organosilicon compounds.

[0047] The surface coating treatment refers to adding a surface coating treatment agent in the form of an emulsion or an alcohol solution into a reaction solution to perform surface modification treatment on the silver powder.

[0048] See also Figure 2 , shows a schematic structural diagram of a highly dispersed metal powder preparation device according to an embodiment of the present invention.

[0049] The highly dispersed metal powder preparation device 100 includes a circulation regulating reactor 10, a highly dispersed synthesis reactor 20, and a circulation device 30. The highly dispersed synthesis reactor 20 is connected to the circulation regulating reactor 10 by a pipeline, and the bottom liquid or the reaction liquid is forcibly dispersed in the highly dispersed synthesis reactor 20. The circulation device (such as a circulation pump) 30 is respectively connected to the circulation regulating reactor 10 and the highly dispersed synthesis reactor 20 by pipelines, so that the bottom liquid or the reaction liquid is continuously circulated in the highly dispersed metal powder preparation device 100.

[0050] like Figure 2 As shown, the outlet of the circulation regulating reactor 10 is connected to the first pipeline 51, and the first pipeline 51 is branched into two flow paths. The first flow path 52 of the two flow paths passes through the first valve 53, the circulation device 30, the second valve 54, the high-dispersion synthesis reactor 20 in sequence and is connected to the inlet 55 of the circulation regulating reactor 10 through the second pipeline 59.

[0051] The second flow path 56 of the two flow paths is provided with a third valve 57 to discharge the reaction liquid after the synthesis reaction is stopped, and form the final product.

[0052] In addition, a stirring rod 11 is also provided in the circulation regulating reactor 10, for example, extending from the top to the center thereof.

[0053] In an actual preparation process, the bottom liquid (dispersion liquid or pure water, and pre-synthesized seed crystals can also be added) is added to the circulation adjustment reactor 10, and the circulation pump 30 arranged at the bottom of the circulation adjustment reactor 10 is turned on to circulate the bottom liquid inside and outside through the high-dispersion synthesis reactor 20.

[0054] In one example, the flow rate of the circulation pump 30 is adjusted so that the bottom liquid flows in the high-dispersion synthesis reactor in a piston flow state. Specifically, the bottom liquid enters the high-dispersion synthesis reactor 20 from bottom to top in a piston flow state, and after forced dispersion by the high-dispersion synthesis reactor 20, it flows into the circulation adjustment reactor 10 along the tangent direction of the reactor wall of the circulation adjustment reactor 10, and achieves a stable circulation.

[0055] In one example, the bottom liquid continuously circulates between the circulation adjustment reactor 10 and the high-dispersion synthesis reactor 20 and completes a cycle within a period of 1-10 minutes, that is, a stable cycle is achieved.

[0056] In step (2), the reaction liquid, the oxidizing liquid and the reducing liquid are also respectively fed into the high-dispersion synthesis reactor 20 in a plug flow state, and the details are not further described.

[0057] The volume of the high-dispersion synthesis reactor 20 is smaller than the volume of the circulation adjustment reactor 10. Usually, the volume of the high-dispersion synthesis reactor 20 is 1L-50L, preferably 3L-20L. The volume of the high-dispersion synthesis reactor 20 needs to be controlled within a certain range. If the volume of the high-dispersion synthesis reactor 20 is too large or too small, the reaction liquid will not achieve the ideal dispersion effect when passing through the high-dispersion synthesis reactor 20 due to its too large or too small volume, causing the metal powder to easily agglomerate. The volume ratio of the high-dispersion synthesis reactor 20 to the circulation adjustment reactor 10 is 1 to 2000, preferably 1 to 500. Of course, those skilled in the art can also make a choice according to actual needs. In one embodiment, an ultrasonic device 40 is arranged on the outer wall or inside the high-dispersion synthesis reactor 20, and of course, a shear disperser 40 can also be arranged inside it.

[0058] When an ultrasonic device or a shearing disperser 40 is provided, the bottom liquid or the reaction liquid is forcibly dispersed by the ultrasonic device or the shearing disperser 40 on the high-dispersion synthesis reactor 20 and then returns to the reaction liquid system along the tangential direction of the inner wall of the circulation adjustment reactor 10 through the outlet of the high-dispersion synthesis reactor 20.

[0059] It should be noted that the high-dispersion synthesis reactor can adopt any principle of forced dispersion, and there is no limitation here. The ultrasonic device can be set in the form of an ultrasonic dispersion rod, and the high-dispersion synthesis reactor with a shearing disperser can be set as a high-speed dispersion homogenizer, for example, the ultrasonic dispersion rod or the shearing disperser can be set as an integrated or powdered one, and set at the center of the high-dispersion synthesis reactor.

[0060] In order to further enhance the dispersion of the metal powder in the reaction solution in the high-dispersion synthesis reactor 20, an ultrasonic device is installed on the high-dispersion synthesis reactor 20. When the ultrasonic vibration rod and / or the high-speed dispersion homogenizer are installed inside the high-dispersion synthesis reactor 20, the distance d from the outer wall of the ultrasonic vibration rod and / or the high-speed dispersion homogenizer to the inner wall of the high-dispersion synthesis reactor 20 is 1-30 cm, preferably 2-10 cm.

[0061] In one example, the ultrasonic device 40 installed inside the high-dispersion synthesis reactor 20 is a slender ultrasonic rod. Its ultrasonic frequency is 20KHz-100KHz, preferably 40KHz-80KHz. If it is installed outside the high-dispersion synthesis reactor 20, a ring ultrasonic device is selected.

[0062] In addition, a high-speed dispersing homogenizer may be installed inside the high-dispersing synthesis reactor 20, and the rotation speed of the high-speed dispersing homogenizer is 3000rpm-5000rpm.

[0063] When performing forced external circulation, a combination of ultrasonic waves and high-speed dispersing homogenizers can also be used simultaneously to further achieve high dispersion of metal powders and concentrated distribution of particle sizes.

[0064] In one example, in order to ensure that the reaction liquid is fully dispersed in the high-dispersion synthesis reactor 20, the shape setting of the high-dispersion synthesis reactor or the dispersion device 20 is very important. The high-dispersion synthesis reactor 20 itself cannot have dead corners, and its joints should be connected at a certain curvature to ensure that the reaction liquid flows from bottom to top through the high-dispersion synthesis reactor 20 in a piston-like manner without backflow. Therefore, the structure of the high-dispersion synthesis reactor 20 in the present invention is set to a (slender) cylindrical shape with curvature heads at both ends and a polished interior, and is connected to the circulation adjustment reactor 10 through a curvature joint.

[0065] In one example, the high-dispersion synthesis reactor 20 is designed with a larger aspect ratio. To achieve a good synthesis effect and prevent clogging, the aspect ratio of the high-dispersion synthesis reactor should be controlled within a certain range (aspect ratio of 2-20, preferably 3-8).

[0066] In the present invention, the metal powder has a spherical or quasi-spherical shape. In the present invention, by adding a high-dispersion synthesis reactor 20, the forced dispersion effect of the reactor makes the prepared metal powder have high dispersion and uniformity.

[0067] In addition, the metal powder prepared by the present invention also has a narrow distribution width, and the particle size distribution width (D90-D10 / D50) of the metal powder is below 0.9; the metal powder includes powder of any one of silver, copper, tin and nickel or any combination thereof.

[0068] Characterization method of particle size distribution width: Test the particle size D10, D50, and D90 on a laser diffraction particle size analyzer, and then calculate according to the following formula:

[0069] Particle size distribution width = (D90-D10) / D50

[0070] The smaller the particle size distribution width value, the better the dispersion and uniformity of the metal powder (such as silver powder); the larger the value, the worse the dispersion and uniformity of the silver powder.

[0071] When synthesizing the powder, the oxidizing liquid and the reducing liquid are simultaneously and continuously (in a piston flow state) added to the high-dispersion synthesis reactor 20, and the dispersing liquid and other regulating liquids are added to the continuous circulation regulating reactor 10.

[0072] Through the combined effect of the small-scale high-dispersion synthesis reactor 20 and the circulating regulating reactor 10, the advantages of the ultrasonic dispersing device and / or the high-speed dispersing homogenizer can be fully utilized, and large-scale industrial production can be realized; the prepared metal powder has a very high degree of dispersion and uniformity.

[0073] Returning to the method of the present invention, the bottom liquid or reaction liquid is forcibly dispersed by the ultrasonic dispersion rod and / or the shear disperser 40 on the high-dispersion synthesis reactor 20 and then returned to the reaction liquid system through the outlet of the high-dispersion synthesis reactor 20 along the tangent direction of the kettle wall of the circulation adjustment reactor 10.

[0074] The stirring speed in the circulation regulating reactor 10 needs to be controlled within a certain range so that the dispersion liquid and pH regulating liquid added to the circulation regulating reactor 10 during the reaction can be quickly mixed with the reaction liquid sent back from the high-dispersion synthesis reactor 20. Generally, the stirring speed is preferably controlled within a range of 50 rpm to 300 rpm, preferably 75 rpm to 200 rpm.

[0075] After the above operation reaches the required stability, the oxidizing liquid and the reducing liquid are sent to the high-dispersion synthesis reactor 20 at a certain flow rate for reduction synthesis reaction. During the entire synthesis reaction, the reaction liquid is continuously sent to the high-dispersion synthesis reactor 20 by the circulation pump 30 at the bottom of the kettle for strong dispersion without dead angles and without distinction. At the same time, the oxidizing liquid and the reducing liquid are also continuously sent to the high-dispersion synthesis reactor 20 to participate in the reduction synthesis reaction; during the entire synthesis reaction, the concentration of the dispersant during the reaction process is maintained stable by adding the dispersing liquid to the circulation adjustment reactor 10, and the acid-base regulator is added according to the online monitoring of the change of the pH value in the reaction liquid to maintain the stability of the pH value during the reaction. When the particle size of the metal powder reaches the required size, the surface coating treatment agent is added to the circulation adjustment reactor for powder surface treatment. Finally, the synthesis reaction liquid is subjected to solid-liquid separation, cleaning, post-treatment, drying and other processes to obtain a highly dispersed metal powder.

[0076] The method and device for preparing highly dispersed metal powder of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0077] Example 1

[0078] 1. Add 2kg of silver nitrate to 15kg of pure water at 15℃-45℃, stir and dissolve to obtain an oxidizing solution;

[0079] 2. Add 2 kg of ascorbic acid to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain a reducing solution;

[0080] 3. Add 80g of PVP K30 to 10kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion;

[0081] 4. Add 300g of PVP K30 to 5kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion adjustment solution;

[0082] 5. Acid-base regulating solution: 25% concentrated ammonia water;

[0083] 6. Add the dispersion as the reaction liquid (base liquid) into the circulation adjustment reactor 10, and start the agitator 11 of the circulation adjustment reactor 10.

[0084] 7. The reaction liquid is forced to pass through the high-dispersion synthesis reactor 20 through the circulation pump 30 for forced internal and external circulation. The reaction IB2024BC0052Y (OA1) is forced to pass through the high-dispersion synthesis reactor 20 and the temperature control device of the circulation regulating reactor 10.

[0085] The liquid temperature is adjusted to 20°C. The volume of the high-dispersion synthesis reactor 20 is 3L, and the aspect ratio is 3. An ultrasonic vibrating rod is installed in the high-dispersion synthesis reactor 20, and the frequency of the ultrasonic rod is 20kHz and the power is 2000W;

[0086] 8. The oxidizing liquid and the reducing liquid are fed into the high-dispersion synthesis reactor 20 for synthesis reaction. At the same time, the dispersion regulating liquid is added in the circulating regulating reactor 20 according to the feeding speed of the oxidizing liquid and the reducing liquid, and the acid-base regulating liquid is added according to the online pH monitoring of the reaction liquid to maintain the stability of the dispersant concentration and pH value. Sampling analysis and testing are carried out during the reaction process. When the particle size of the metal powder reaches the requirement, the dripping is stopped, and the stirring and circulation are continued for 10 minutes to stop the reaction. After the synthetic reaction liquid is processed by solid-liquid separation, cleaning, post-treatment, drying and other processes, a silver powder with a D50 of 1.52um and a particle size distribution width of 0.78 is obtained.

[0087] The particle size and particle size distribution of the silver powder prepared in Example 1 are shown in Table 1.

[0088] The scanning electron microscope image of the silver powder prepared in Example 1 is shown in Figure 3 The silver powder is basically spherical, with uniform morphology, excellent dispersion and high crystallinity.

[0089] Example 2

[0090] 1. Add 2.4 kg of silver nitrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain an oxidizing solution;

[0091] 2. Add 2 kg of ascorbic acid to 15 g of pure water at 15°C-45°C, stir and dissolve to obtain a reducing solution;

[0092] 3. Add 40 g of polyvinyl alcohol and 40 g of fatty acid salt to 10 kg of pure water at 15°C-45°C, stir and dissolve to obtain a dispersion.

[0093] 4. Add 150g of polyvinyl alcohol and 150g of fatty acid salt to 5kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion adjustment liquid;

[0094] 5. Acid-base regulating solution: 25% concentrated ammonia water;

[0095] 6. The subsequent reaction steps are the same as those in Example 1. The frequency of the ultrasonic rod in Example 2 is adjusted to 40 kHz.

[0096] 7. The prepared silver powder has a D50 of 1.54 um and a particle size distribution width of 0.68.

[0097] The particle size and particle size distribution results of the silver powder prepared in Example 2 of the present invention are shown in Table 1.

[0098] The scanning electron microscope image of the silver powder prepared in Example 2 of the present invention is shown in Figure 4 The silver powder is spherical, with uniform morphology, excellent dispersion, no agglomeration and high crystallinity.

[0099] Example 3

[0100] 1. Add 3kg of silver nitrate to 15kg of pure water at 15℃-45℃, stir and dissolve to obtain an oxidizing solution;

[0101] 2. Add 2.4 kg of ascorbic acid to 15 kg of pure water at 15°C-45°C, and stir to dissolve to obtain a reducing solution;

[0102] 3. Add 150g of PVP K30 to 10kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion;

[0103] 4. Add 10 g of PVP K306 to 5 kg of pure water at 15°C-45°C, stir and dissolve to obtain a dispersion adjustment solution;

[0104] 5. Acid-base regulating solution: 25% concentrated ammonia water;

[0105] 6. The subsequent reaction steps are the same as those in Example 1. The frequency of the ultrasonic rod is adjusted to 60 kHz.

[0106] 7. The D50 of the prepared silver powder is 1.52um, and the distribution width of the silver powder is 0.78.

[0107] The particle size and particle size distribution results of the silver powder prepared in Example 3 of the present invention are shown in Table 1.

[0108] The scanning electron microscope image of the silver powder prepared in Example 3 of the present invention is shown in Figure 5 The silver powder is spherical, with uniform morphology, excellent dispersion, no agglomeration and high crystallinity.

[0109] Example 4

[0110] 1. Add 2.4 kg of silver nitrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain an oxidizing solution;

[0111] 2. Add 1.5 kg of hydrazine hydrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain a reducing solution;

[0112] 3. Add 80g of PVP K30 to 10kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion;

[0113] 4. Add 300g of PVP K30 to 5kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion adjustment solution;

[0114] 5. Acid-base regulating solution: 25% concentrated ammonia water;

[0115] 6. The subsequent reaction steps are the same as those in Example 1. The high-dispersion synthesis reactor is replaced by a high-speed dispersing homogenizer, and the speed of the high-speed dispersing homogenizer is 4000 rpm;

[0116] 7. The D50 of the prepared silver powder is 1.46um, and the distribution width of the silver powder is 0.72;

[0117] The particle size and particle size distribution results of the silver powder prepared in Example 4 of the present invention are shown in Table 1.

[0118] The scanning electron microscope image of the silver powder prepared in Example 4 of the present invention is shown in Figure 6 The silver powder is spherical, with uniform morphology, excellent dispersion, no agglomeration and high crystallinity.

[0119] Example 5

[0120] 1. Add 2.4 kg of silver nitrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain an oxidizing solution;

[0121] 2. Add 1.5 kg of ascorbic acid to 15 kg of pure water at 15°C-45°C, and stir to dissolve to obtain a reducing solution;

[0122] 3. Add 100g of PVP K30 to 10kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion.

[0123] 4. Add 390 g of PVP K30 to 5 kg of pure water at 15°C-45°C, stir and dissolve to obtain a dispersion adjustment solution;

[0124] 5. Acid-base regulating solution: 25% concentrated ammonia water;

[0125] 6. The subsequent reaction steps are the same as those in Example 1. The high-dispersion synthesis reactor is replaced by a high-speed dispersing homogenizer, and the speed of the high-speed dispersing homogenizer is 3500 rpm;

[0126] 7. Prepare silver powder with a D50 of 1.46um and a distribution width of 0.88;

[0127] The particle size and particle size distribution results of the silver powder prepared in Example 5 of the present invention are shown in Table 1.

[0128] The scanning electron microscope image of the silver powder prepared in Example 5 of the present invention is shown in Figure 7 The silver powder is spherical, with uniform morphology, excellent dispersion, no agglomeration and high crystallinity.

[0129] Comparative Example 1

[0130] 1. Add 2.4 kg of silver nitrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain an oxidizing solution;

[0131] 2. Add 2 kg of ascorbic acid to 15 kg of pure water at 15°C-45°C, and stir to dissolve to obtain a reducing solution;

[0132] 3. Add 300 g of polyvinyl alcohol to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain a dispersion.

[0133] 4. The synthesis reaction is completed in one reactor without using a high-dispersion synthesis reactor. The dispersion is added to the reactor under stirring, and then the oxidizing liquid and the reducing liquid are added. After the reaction is completed, the surface is coated. Finally, the synthesis reaction liquid is subjected to solid-liquid separation, cleaning, post-treatment, drying and other processes to obtain a D50 of 1.51um and a distribution width of 1.2 for the silver powder.

[0134] The particle size and particle size distribution results of the silver powder prepared in Comparative Example 1 are shown in Table 1.

[0135] The scanning electron microscope image of the silver powder prepared in Comparative Example 1 is shown in Figure 8 The silver powder has irregular and spherical shapes, poor dispersion and serious agglomeration.

[0136] Comparative Example 2

[0137] 1. Add 2.4 kg of silver nitrate to 15 kg of pure water at 15°C-45°C, stir and dissolve to obtain an oxidizing solution;

[0138] 2. Add 2 kg of ascorbic acid to 15 kg of pure water at 15°C-45°C, and stir to dissolve to obtain a reducing solution;

[0139] 3. Add 500g of PVP K30 to 15kg of pure water at 15℃-45℃, stir and dissolve to obtain a dispersion.

[0140] 4. The subsequent reaction steps are the same as those in Comparative Example 1;

[0141] 5. The D50 of the prepared silver powder is 1.59um, and the distribution width of the silver powder is 1.21.

[0142] The particle size and particle size distribution results of the silver powder prepared in Comparative Example 2 are shown in Table 1.

[0143] The scanning electron microscope image of the silver powder prepared in Comparative Example 2 is shown in Fig. 9 The silver powder has an irregular, spherical shape, poor dispersion, and serious agglomeration.

[0144] Table 1 Comparison of implementation results data

[0145]

[0146] The method for preparing metal powder by using a high-dispersion synthesis reactor and the device for preparing high-dispersion metal powder according to the embodiments of the present invention have at least one of the following advantages or part of one of the advantages:

[0147] 1. The oxidizing liquid and reducing liquid are passed through a small high-dispersion synthesis reactor for synthesis reaction, and the liquid after the reaction is sent to a circulation adjustment reactor for reaction parameter adjustment. The adjusted reaction is recycled and sent to the high-dispersion synthesis reactor to react with the oxidizing liquid reducing liquid until the particle size of the prepared metal powder reaches the target value. The circulating adjustment reactor adds a dispersant and / or a regulator under stirring to ensure that the reduction reaction is carried out at a basically constant dispersant concentration and pH value, so as to achieve the synthesis of highly dispersed and highly uniform metal powders. This method has good repeatability and strong operability. The metal powder prepared by this method has the advantages of high dispersion, narrow particle size distribution and high uniformity, which solves the shortcomings of existing metal powders such as poor dispersibility, wide particle size distribution and poor uniformity; it is suitable for conductive slurries, conductive adhesives and other fields that have high requirements for the dispersibility, particle size distribution and uniformity of metal powders.

[0148] 2. The growth of silver powder is carried out in a small-scale highly dispersed synthesis reactor. The silver powder particles synthesized in the small-scale highly dispersed synthesis reactor are refluxed into the circulation adjustment reactor, and various parameters are adjusted before being sent to the small-scale highly dispersed synthesis reactor again to participate in the synthesis. The silver particles contained in the reaction liquid sent to the small-scale highly dispersed synthesis reactor will participate in the further synthesis and growth of silver powder in the small-scale highly dispersed synthesis reactor as crystal nuclei. During the production process, the quantitative ratio between the silver powder as the crystal nucleus and the oxidizing liquid and the reducing liquid is adjusted by controlling the flow rate of the adjusted mixed reaction liquid containing particles entering the small-scale highly dispersed synthesis reactor, and the generation of silver powder is further controlled, thereby ensuring the achievement of product goals.

[0149] 3. The technology of the present invention utilizes the characteristics of a small-scale high-dispersion synthesis reactor, which has small volume, strong dispersion and stirring, and no dead corners, thereby avoiding the agglomeration of silver powder during the silver powder synthesis reaction.

[0150] 4. The silver particles formed after the mixed reaction of the oxidizing solution and the reducing solution will continue to participate in the next cycle of synthesis reaction as seeds. The newly generated silver particles will grow and adjust the microcrystalline morphology on the original silver particles, and the cycle will be repeated until the particle size of the silver powder meets the requirements. Using this method, when synthesizing silver powder, in addition to adjusting the parameters of the oxidizing solution and the reducing solution to control the particle size of the silver powder, the particle size and morphology of the silver powder can also be controlled by controlling the amount of silver source during the reaction cycle.

[0151] 5. The present invention uses a small high-dispersion synthesis reactor and a large-sized circulation regulating reactor to work together to achieve large-scale production and reduce the amplification effect of production. The use of a small high-dispersion synthesis reactor is mainly to fully ensure the dispersion and uniformity of the silver powder due to its small size and the absence of a stirring dead angle.

[0152] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Those skilled in the art will understand that these embodiments can be changed without departing from the principles and spirit of the overall concept of the present invention, and these changes should also be regarded as falling within the protection scope of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for preparing metal powder using a high-dispersion synthesis reactor, the method comprising the following steps: Step (1) adding the bottom liquid into a circulation regulating reactor, and performing internal and external circulation through a high-dispersion synthesis reactor connected to the circulation regulating reactor to achieve stable circulation, wherein an ultrasonic device is arranged on the outer wall or inside of the high-dispersion synthesis reactor; and / or a shearing disperser is arranged inside the high-dispersion synthesis reactor, and the volume ratio of the high-dispersion synthesis reactor to the circulation regulating reactor is 1:2000 to 1:500; Step (2) after the stable circulation meets the predetermined requirements, the oxidizing liquid and the reducing liquid are continuously added to the high-dispersion synthesis reactor to carry out a synthesis reaction and generate a reaction liquid. During the synthesis reaction, the reaction liquid is continuously sent to the high-dispersion synthesis reactor for forced dispersion, and the synthesis reaction is carried out therein with the oxidizing liquid and the reducing liquid that are continuously added to the high-dispersion synthesis reactor; Step (3) sampling, analyzing and testing are performed during the synthesis reaction. When the particle size of the metal powder generated by the synthesis reaction meets the requirements, the addition of the oxidizing liquid and the reducing liquid is stopped to stop the synthesis reaction; Step (4) After the reaction liquid is discharged from the circulating regulating reactor, it is subjected to solid-liquid separation, washing, post-treatment, and drying to obtain highly dispersed metal powder; In step (1) or step (2), at least one of the base liquid, reaction liquid, oxidation liquid and reduction liquid enters the high-dispersion synthesis reactor from bottom to top in a piston flow state, and after forced dispersion in the high-dispersion synthesis reactor, flows into the circulation regulating reactor along the tangent direction of the reactor wall of the circulation regulating reactor, and achieves stable circulation; or In step (2), at least one of the reaction liquid, the oxidizing liquid and the reducing liquid enters the highly dispersed synthesis reactor from bottom to top in a plug flow state.

2. The method according to claim 1, characterized in that The bottom liquid continuously circulates between the circulation adjustment reactor and the high-dispersion synthesis reactor and completes a cycle within a period of 1-10 minutes to achieve a stable cycle; In step (3), an acid-base adjustment liquid is added according to the change of the pH value in the reaction liquid under online monitoring; when the particle size requirement of the metal powder is reached, a surface coating treatment agent is added to the circulating adjustment reactor to perform surface treatment of the powder; When synthesizing silver powder, the particle size of the silver powder is controlled by adjusting the parameters of the oxidizing solution and the reducing solution, or the particle size and morphology of the silver powder are controlled by controlling the amount of silver source in the circulation process.

3. The method according to claim 2, characterized in that The circulation regulating reactor and the high-dispersion synthesis reactor are connected in series through a pipeline, and the volume of the high-dispersion synthesis reactor is smaller than the volume of the circulation regulating reactor; The volume of the high-dispersion synthesis reactor is 1L-50L; The circulating regulating reactor is added with dispersion liquid and / or pH regulator under stirring.

4. The method according to claim 3, characterized in that The stirring speed in the circulation regulating reactor is controlled at 50 rpm to 300 rpm, so that the dispersion liquid and pH regulating liquid added to the circulation regulating reactor during the synthesis reaction can be quickly mixed with the reaction liquid sent back from the high-dispersion synthesis reactor; By controlling the flow rate of the mixed reaction liquid containing metal particles regulated by the circulation regulating reactor entering the high-dispersion synthesis reactor, the quantitative ratio between the silver powder as the crystal nucleus and the oxidizing liquid and the reducing liquid is adjusted, and the generation of the silver powder is further controlled.

5. The method according to claim 3, characterized in that: The aspect ratio of the high-dispersion synthesis reactor is in the range of 2-20. The structure of the high-dispersion synthesis reactor is a cylindrical shape with curved ends at both ends and a polished interior. The reactor is connected with the reactor through a curved joint.

6. The method according to claim 5, characterized in that An ultrasonic device is arranged on the outer wall or inside of the high-dispersion synthesis reactor; and / or The high-dispersion synthesis reactor is provided with a shear disperser inside. When at least one of the ultrasonic device and the shearing disperser is arranged in a high-dispersion synthesis reactor, the distance from the outer wall of at least one of the ultrasonic device and the shearing disperser to the inner wall of the high-dispersion synthesis reactor is in the range of 1-30 cm, and the ultrasonic frequency of the ultrasonic device is in the range of 20 KHz-100 KHz.

7. The method according to claim 6, characterized in that The distance between the outer wall of at least one of the ultrasonic device and the shear disperser and the inner wall of the high-dispersion synthesis reactor is in the range of 2-10 cm; The ultrasonic frequency range is 40KHz-80KHz; The rotation speed of the shear disperser is 3000rpm-5000rpm.

8. The method according to claim 7, characterized in that The metal powder has a spherical or quasi-spherical shape; The particle size distribution width of the metal powder is less than 0.9; The metal powder includes powder of any one of silver, copper, tin and nickel or any combination thereof.

9. The method according to any one of claims 1 to 8, characterized in that The base liquid is pure water or a dispersion or pre-synthesized seed crystals, the dispersion is an aqueous solution containing any one of polyvinyl alcohol, guar gum, arabic resin, polyvinyl pyrrolidone, fatty acid, copper nitrate, magnesium nitrate or any combination thereof, and the concentration of the dispersion is 10-100 g / L; Preparation of the oxidizing solution: Add the metal salt into pure water, stir and dissolve, and keep the temperature at 15°C-45°C. The metal salt in the oxidizing solution includes any one of oxalate, carbonate, sulfate, citrate, nitrate, metal oxide, and metal ammonia complex, or any combination thereof, and the concentration of the metal salt is 30 g / L-300 g / L. When the metal salt is silver nitrate, the oxidizing solution is a silver ammonia complex solution prepared by adding ammonia water to silver nitrate. Preparation of the reducing solution: adding a reducing agent into pure water, stirring and dissolving, and maintaining a constant temperature at 15° C.-45° C., wherein the reducing agent comprises any one of hydrazine hydrate, formaldehyde, formic acid, ammonium formate, ascorbic acid, hydrogen peroxide, triethanolamine, glycerol, glucose, and hydroxylamine, or any combination thereof, and the concentration of the reducing agent is 20 g / L-200 g / L.

10. The method according to claim 2, characterized in that The acid-base adjustment liquid is an aqueous solution of any one of ammonia water, ethanolamine, diethanolamine, triethanolamine, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, or any combination thereof.

11. A device for preparing highly dispersed metal powder using the method according to claim 1, comprising: Circulation adjustment reactor; A high-dispersion synthesis reactor, wherein the high-dispersion synthesis reactor is connected to a circulation regulating reactor pipeline, and the bottom liquid or the reaction liquid is forcibly dispersed in the high-dispersion synthesis reactor; The circulation device is connected to the circulation regulating reactor and the high-dispersion synthesis reactor pipeline respectively, so that the base liquid or the reaction liquid can be continuously circulated in the high-dispersion metal powder preparation device.

12. The device for preparing highly dispersed metal powder according to claim 11, characterized in that: When at least one of the ultrasonic device and the shearing disperser is arranged in the high-dispersion synthesis reactor, the distance from the outer wall of at least one of the ultrasonic device and the shearing disperser to the inner wall of the high-dispersion synthesis reactor is in the range of 1-30 cm.

13. The device for preparing highly dispersed metal powder according to claim 12, characterized in that: The high-dispersion synthesis reactor is cylindrical with curved ends at both ends and a polished interior, and is connected to the reaction kettle via a curved joint.

14. The device for preparing highly dispersed metal powder according to claim 13, characterized in that: The outlet of the circulation regulating reactor is connected to a first pipeline, the first pipeline is branched into two flow paths, the first flow path of the two flow paths passes through the first valve, the circulation device, the second valve, the high-dispersion synthesis reactor in sequence and is connected to the inlet of the circulation regulating reactor through a pipeline; A third valve is provided on the second flow path of the two flow paths to discharge the reaction liquid after the synthesis reaction is stopped. The circulation regulating reactor is also provided with a stirring rod.

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