CN115519129A - Preparation method of silver powder for conductive paste - Google Patents

Abstract

The invention discloses a method for preparing silver powder for conductive paste. The wet silver powder is prepared from a silver-containing solution and a reducing agent solution, and a surface treatment agent is prepared by emulsifying an organic solvent obtained by mixing a hydrophobic surfactant and a solvent with water. Silver powder is obtained by coating the surface treatment agent with wet silver powder. The surface treatment agent uses a hydrophobic surfactant and is emulsified to form a water-in-oil emulsion. The surface treatment agent is added after the preparation of the wet silver powder, which can completely cover the silver powder, so that the prepared silver powder particles have good dispersion and no agglomeration. Re-dispersed in a non-polar solvent, the particle size of the silver powder is uniform, the particle size distribution is narrow, the average particle size is small, the yield of the silver powder is high, and the production cycle is short.

Description

Preparation method of silver powder for conductive paste

technical field

The invention relates to a method for preparing silver powder, in particular to a method for preparing silver powder for conductive paste.

Background technique

A nano-silver and its synthesis method (country: China, publication number: 109079154B, publication date: 2022-03-01), which discloses that wet silver powder added with a hydrophilic surface treatment agent is heated in an oil bath Stir to form a nano-silver sol, and then add a sedimentation agent to make the surface of the silver powder a hydrophobic structure.

A surface treatment liquid and its addition method in the preparation process of silver powder (country: China, publication number: 112024906A, publication date: 2020-12-04), which discloses that a lipophilic surfactant, a hydrophobic defoamer and an organic solvent are processed mixing to obtain a surface treatment solution, and then adding the surface treatment solution to the silver powder synthesis system, stirring and mixing, and then washing and drying. The surface treatment liquid overcomes the problem of poor dispersion and easy agglomeration of silver powder in the prior art, and at the same time saves the cumbersome heating of the surface treatment agent multiple times, improves operation efficiency, reduces operation errors, and saves time and effort. In the silver synthesis system, the hydrophobic defoamer will attract the hydrophobic end of the surfactant, making the hydrophobic defoamer hydrophilic, thereby reducing the concentration and tension of the surfactant in the foam film in the silver synthesis system , and then play a defoaming effect; the organic solvent can dissolve the lipophilic surfactant and the hydrophobic defoamer, thereby reducing the melting point of the two lipophilic surfactants and the hydrophobic defoamer.

But the silver powder surface treatment agent in the above method is easy to separate out, floats on the surface layer, and the coating is incomplete, and the particle size distribution of the finished silver powder is wide, and the average particle size is large.

Contents of the invention

Purpose of the invention: the purpose of this invention is to provide a kind of preparation method of silver powder for conductive paste, obtain the finished silver powder with narrow particle size distribution and uniform particle size.

Technical solution: a method for preparing silver powder for conductive paste, comprising the following steps:

Step S10, preparing wet silver powder: reacting the silver-containing solution with the reducing agent solution to form silver precipitates to form wet silver powder;

Step S20, preparing a surface treatment agent: mixing a hydrophobic surfactant and a solvent to form an organic solvent, generating a solution under heating conditions, adding hot water, and stirring to form an emulsion surface treatment agent;

Step S30, coating: adding a surface treatment agent into the wet silver powder, performing coating treatment, and drying to obtain silver powder.

Further, in step S10, the silver-containing solution is one of silver ammonia solution, Ag ₂ O suspension or Ag ₂ CO ₃ suspension, and the reducing agent solution is glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium erythorbate, para One of the diphenols.

Further, in step S10, after the silver precipitate is formed, a dispersant is added and mixed evenly to form wet silver powder.

Further, the dispersant is one or a mixture of two or more of polyvinylpyrrolidone, citrate, oleylamine, and organic compounds with methylsiloxy functional groups.

Further, the amount of the dispersant is 0.01-5% of the silver content of the wet silver powder, the mole percentage.

Further, in step S20: the amount of the hydrophobic surfactant is 0.0001 to 20% of the silver content of the wet silver powder, in mass percent; the hydrophobic surfactant and the solvent are mixed in a mass ratio of 1:80 to 10:80 into an organic solvent; hot water and hydrophobic surfactants are used in a mass ratio of 1:1 to 10:1.

Further, in step S20, the hydrophobic surfactant is C ₆ -C ₂₂ saturated fatty acids, C ₆ -C ₂₂ unsaturated fatty acids, C ₆ -C ₂₂ esters, C ₆ -C ₂₂ amines, C ₆ -C 22 ₂₂ One or a mixture of fatty amines and C ₆ -C ₂₂ fatty amides, and the solvent is one or a mixture of at least two of ethanol, acetone, ethylene glycol, and toluene.

Further, in step S20, the heating condition is 30°C-100°C, and the temperature of the hot water is 30°C-100°C.

Further, in step S20, stirring is performed with a homogenizer at a speed of 1000-30000 r/min for 1-3 minutes to form an emulsion, and the stirring speed is preferably such that the emulsion can be formed and the liquid does not splash.

Further, in step S30, the surface treatment agent is first cooled to the temperature of the wet silver powder, and then added to the wet silver powder.

Beneficial effects: the advantages of the present invention are: the surface treatment agent used in the preparation of silver powder adopts hydrophobic surfactant and emulsifies to form a water-in-oil emulsion, and the surface treatment agent is added after the preparation of wet silver powder, which can completely coat the silver powder , so that the prepared silver powder particles have good dispersibility and no agglomeration, and can be redispersed in non-polar solvents. The particle size of the silver powder particles is uniform, the particle size distribution is narrow, the average particle size is small, the yield of the silver powder is high, and the production cycle is short.

Description of drawings

Fig. 1 is the micrograph of the silver powder that embodiment 1 makes;

Fig. 2 is the microscope picture of the silver powder that comparative example 1 makes.

detailed description

The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments.

A method for preparing silver powder for conductive paste. The wet silver powder is prepared from a silver-containing solution and a reducing agent solution. When preparing the wet silver powder, a dispersant can also be added, and water is added to an organic solvent formed by mixing a hydrophobic surfactant and a solvent. The surface treatment agent is obtained by emulsification, and the surface treatment agent is coated with wet silver powder to obtain silver powder.

The silver-containing solution is one of silver ammonia solution, Ag ₂ O suspension or Ag ₂ CO ₃ suspension, and the reducing agent solution is one of glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium erythorbate, hydroquinone, etc. . The dispersant is one of polyvinylpyrrolidone, citrate, oleylamine, and organic compounds with methylsiloxy functional groups or a mixture of two or more. The organic compounds with methylsiloxy functional groups can be BYK-167, BYK- 191, BYK-230, etc. Hydrophobic surfactants are C ₆ ~C ₂₂ saturated fatty acids, C ₆ ~C ₂₂ unsaturated fatty acids, C ₆ ~C ₂₂ esters, C ₆ ~C ₂₂ amines, C ₆ ~C ₂₂ fatty amines, C ₆ ~ One or at least two mixtures of _C22 fatty amides, specifically oleylamine, oleic acid amide, erucamide, dodecylamine, octadecylamine, triethanolamine, stearic acid, glycerol monostearate ester, sorbitan laurate, polyoxyethylene sorbitan monostearate, etc., the solvent is one of ethanol, acetone, ethylene glycol, toluene or a mixture of at least two.

The dosage of the dispersant is 0.01-5% of the silver content of the wet silver powder, which is the mole percentage. The dosage of the hydrophobic surfactant is 0.0001-20% of the silver content of the wet silver powder, which is the percentage by mass. The hydrophobic surfactant and the solvent are mixed in a mass ratio of 1:80 to 10:80 to form an organic solvent. Hot water and hydrophobic surfactant are used in a mass ratio of 1:1 to 10:1.

Following each embodiment, based on above-mentioned raw material selection.

Example 1

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ O suspension with a sufficient amount of glucose solution, redox reaction occurs, silver precipitates are formed, and wet silver powder is formed.

Step S20, preparing a surface treatment agent: adding ethanol to oleic acid amide, mixing and stirring at 80°C until completely dissolved to obtain an organic solvent, then adding hot water at 80°C to the organic solvent, using a homogenizer at 10,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The consumption of oleic acid amide is 0.01% of the silver content of the wet silver powder, the oleic acid amide and ethanol are mixed into an organic solvent in a mass ratio of 10:80, and the consumption of hot water and oleic acid amide is in a mass ratio of 1:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 2

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of silver ammonia solution with a sufficient amount of glucose solution to cause a redox reaction to form silver precipitates, then add polyvinylpyrrolidone, and mix evenly to form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to oleic acid amide, mixing and stirring at 80°C until completely dissolved to obtain an organic solvent, then adding hot water at 80°C to the organic solvent, using a homogenizer at 10,000r/min Speed agitation for 1 minute to form an emulsion of the surface treatment agent.

The consumption of polyvinylpyrrolidone is 0.01% of the silver content of wet silver powder, the consumption of oleic acid amide is 0.01% of the silver content of wet silver powder, oleic acid amide and ethanol are mixed into organic solvent by mass ratio 10:80, hot water It is used with oleic acid amide in a mass ratio of 4:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 3

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ CO ₃ suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then adding sodium citrate, and mixing evenly to form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to oleic acid amide, mixing and stirring at 100°C until completely dissolved to obtain an organic solvent, then adding hot water at 100°C to the organic solvent, using a homogenizer at 10,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The consumption of sodium citrate is 0.01% of the silver content of wet silver powder, the consumption of oleic acid amide is 0.01% of the silver content of wet silver powder, oleic acid amide and ethanol are mixed into organic solvent by mass ratio 10:80, hot water The dosage with oleic acid amide is 6:1 in mass ratio.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 4

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ CO ₃ suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then adding sodium citrate, and mixing evenly to form wet silver powder.

Step S20, preparing a surface treatment agent: adding acetone to dodecylamine, mixing and stirring at 90°C until completely dissolved to obtain an organic solvent, then adding hot water at 90°C to the organic solvent, using a homogenizer at 10,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The consumption of sodium citrate is 0.01% of the silver content of wet silver powder, the consumption of dodecylamine is 0.01% of the silver content of wet silver powder, dodecylamine and acetone are mixed into organic solvent by mass ratio 10:80, hot water The dosage is 8:1 with dodecylamine in mass ratio.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 5

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ O suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then add BYK-167, mix evenly, and form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to stearic acid, mixing and stirring at 80°C until completely dissolved to obtain an organic solvent, then adding hot water at 80°C to the organic solvent, using a homogenizer at 30,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The amount of BYK-167 is 0.01% of the silver content of the wet silver powder, and the amount of stearic acid is 0.01% of the silver content of the wet silver powder. Stearic acid and ethanol are mixed into an organic solvent at a mass ratio of 10:80, and hot water The dosage is 10:1 with stearic acid in mass ratio.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 6

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ CO ₃ suspension with a sufficient amount of glucose solution to cause redox reaction to form silver precipitates, then add BYK-191, mix evenly, and form wet silver powder.

Step S20, preparing the surface treatment agent: adding acetone to triethanolamine, mixing and stirring at 90°C until completely dissolved to obtain an organic solvent, then adding hot water at 90°C to the organic solvent, using a homogenizer at a speed of 10,000r/min Stir treatment for 3 minutes to form an emulsion of the surface treatment agent.

The dosage of BYK-191 is 0.01% of the silver content of the wet silver powder, the consumption of triethanolamine is 0.0001% of the silver content of the wet silver powder, the triethanolamine and acetone are mixed into an organic solvent according to the mass ratio of 10:80, hot water and three Ethanolamine is used in a mass ratio of 8:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Embodiment 7 A kind of preparation method of silver powder for conductive paste, specifically comprises the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of silver ammonia solution with a sufficient amount of glucose solution to cause a redox reaction to form silver precipitates, then add BYK-230, mix evenly, and form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to oleic acid amide, mixing and stirring at 80°C until completely dissolved to obtain an organic solvent, then adding hot water at 80°C to the organic solvent, using a homogenizer at 10,000r/min Speed agitation for 1 minute to form an emulsion of the surface treatment agent.

The amount of BYK-230 is 5% of the silver content of the wet silver powder, the amount of oleic acid amide is 0.01% of the silver content of the wet silver powder, the oleic acid amide and ethanol are mixed into an organic solvent at a mass ratio of 10:80, and hot water It is used with oleic acid amide in a mass ratio of 4:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 8

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ CO ₃ suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then adding sodium citrate, and mixing evenly to form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to oleic acid amide, mixing and stirring at 100°C until completely dissolved to obtain an organic solvent, then adding hot water at 100°C to the organic solvent, using a homogenizer at 10,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The consumption of sodium citrate is 0.01% of the silver content of wet silver powder, the consumption of oleic acid amide is 20% of the silver content of wet silver powder, oleic acid amide and ethanol are mixed into organic solvent by mass ratio 10:80, hot water The dosage with oleic acid amide is 6:1 in mass ratio.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 9

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ O suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then add BYK-167, mix evenly, and form wet silver powder.

Step S20, preparing a surface treatment agent: adding ethanol to stearic acid, mixing and stirring at 80°C until completely dissolved to obtain an organic solvent, then adding hot water at 80°C to the organic solvent, using a homogenizer at 30,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The amount of BYK-167 is 0.01% of the silver content of the wet silver powder, and the amount of stearic acid is 0.01% of the silver content of the wet silver powder. Stearic acid and ethanol are mixed into an organic solvent at a mass ratio of 1:80, and hot water The dosage is 10:1 with stearic acid in mass ratio.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 10

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ CO ₃ suspension with a sufficient amount of glucose solution to cause oxidation-reduction reaction to form silver precipitates, then adding sodium citrate, and mixing evenly to form wet silver powder.

Step S20, preparing a surface treatment agent: adding acetone to octadecylamine, mixing and stirring at 90°C until completely dissolved to obtain an organic solvent, then adding hot water at 90°C to the organic solvent, using a homogenizer at 10,000r/min Speed stirring treatment for 3 minutes to form an emulsion of the surface treatment agent.

The consumption of sodium citrate is 0.01% of the silver content of the wet silver powder, the consumption of octadecylamine is 20% of the silver content of the wet silver powder, and octadecylamine and acetone are mixed into an organic solvent by mass ratio of 10:80, hot water With octadecylamine in a mass ratio of 8:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 11

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ O suspension with a sufficient amount of glucose solution, redox reaction occurs, silver precipitates are formed, and wet silver powder is formed.

Step S20, preparing a surface treatment agent: adding ethanol to sorbitan laurate, mixing and stirring at 30°C until completely dissolved to obtain an organic solvent, then adding hot water at 30°C to the organic solvent, using a homogenizer to Stirring at a speed of 10000r/min for 3 minutes to form an emulsion surface treatment agent.

The amount of sorbitan laurate is 0.01% of the silver content of the wet silver powder, sorbitan laurate and ethanol are mixed into an organic solvent in a mass ratio of 10:80, hot water and sorbitan laurate According to the mass ratio of 1:1 dosage.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added to the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Example 12

A preparation method of silver powder for conductive paste, specifically comprising the following steps:

Step S10, preparing wet silver powder: mixing a certain amount of Ag ₂ O suspension with a sufficient amount of glucose solution, redox reaction occurs, silver precipitates are formed, and wet silver powder is formed.

Step S20, preparing a surface treatment agent: adding ethanol to polyoxyethylene sorbitan monostearate, mixing and stirring at 70°C until completely dissolved to obtain an organic solvent, and then adding hot water at 70°C to the organic solvent, Use a homogenizer to stir at a speed of 10000r/min for 3 minutes to form an emulsion surface treatment agent.

The consumption of polyoxyethylene sorbitan monostearate is 0.01% of the silver content of wet state silver powder, polyoxyethylene sorbitan monostearate and ethanol are mixed into organic solvent by mass ratio 10: 80, Hot water and polyoxyethylene sorbitan monostearate are used in a mass ratio of 1:1.

Step S30, coating: after the surface treatment agent is cooled to the temperature of the wet silver powder system, it is added into the wet silver powder for coating treatment, and the silver powder is obtained after drying.

Comparative example 1

The difference from Example 1 is that the homogenizer was stirred at a speed of 400r/min for 3 minutes.

Comparative example 2

The difference from Example 1 is that the hydrophobic surfactant-oleic acid amide is replaced by the hydrophilic surfactant-polyvinyl alcohol.

Comparative example 3

The difference from Example 1 is that the amount of hot water and oleic acid amide is 0.5:1 by mass.

Comparative example 4

The difference from Example 5 is that the amount of hot water and stearic acid is 11:1 by mass.

Comparative example 5

The difference from Example 5 is that the homogenizer was stirred at a speed of 40000r/min for 3 minutes.

Comparative example 6

The difference from Example 5 is that the homogenizer was stirred at a speed of 30000r/min for 0.5 minutes.

Comparative example 7

The difference from Example 4 is that the homogenizer was stirred at a speed of 10000r/min for 5 minutes.

Comparative example 8

The difference from Example 1 is that in step S20, ethanol is added to oleic acid amide, and the organic solvent obtained by mixing and stirring at 80° C. until completely dissolved is used as a surface treatment agent, and water is not heated for emulsification in this step.

Comparative example 9

The difference from Example 3 is that the heating condition is 25°C, and the hot water temperature is 25°C.

The silver powder that each embodiment, each comparative example make, detect quality, list as following table comparison:

serial number Average particle size μm Specific surface area m²/g Tap density g/cm³ Example 1 0.5 1.5 6.3 Example 2 0.8 1.1 6.2 Example 3 1.0 0.9 6.1 Example 4 1.5 0.4 5.8 Example 5 2 0.3 5.5 Example 6 1.6 0.4 5.6 Example 7 0.7 1.2 6.2 Example 8 0.9 1.0 6.1 Example 9 1.9 0.3 5.5 Example 10 1.2 0.6 6.0 Example 11 0.6 1.5 6.4 Example 12 0.6 1.5 6.3 Comparative example 1 2.2 0.3 5.2 Comparative example 2 2.5 0.2 5.1 Comparative example 3 2.1 0.3 5.5 Comparative example 4 2.8 0.15 5.1 Comparative example 5 2.3 0.3 5.2 Comparative example 6 2.4 0.3 5.2 Comparative example 7 1.5 0.4 5.8 Comparative example 8 3.0 0.15 5.0 Comparative example 9 2.8 0.15 5.5

The silver powder prepared by the present application can be used to prepare low-temperature curable conductive paste, which is applied to HJT batteries, membrane switches, medical PVC pipes, touch screens, mobile phone antennas, and can also be used to prepare high-temperature sintered conductive paste. Conductive pastes are used in TOPcon batteries, PERC batteries, piezoelectric ceramics, chip resistors, chip capacitors, chip inductors, automotive glass, and 5G antennas.

The action principle of the silver powder preparation method of the present application: the preparation of surface treatment agent adopts hydrophobic surfactant, and adds a small amount of water in the preparation process, forms water-in-oil type emulsion, and the prepared surface treatment agent is in the preparation wet state silver powder After the addition, the silver powder can be completely coated, so that the prepared silver powder particles have good dispersibility and no agglomeration, and can be re-dispersed in non-polar solvents. The particle size distribution of the silver powder particles is narrow and the average particle size is small.

The embodiment detection data analysis of the present application is specifically as follows:

1. By comparison of each embodiment, it can be seen that when preparing surface treatment agent, the mass ratio of emulsified hot water consumption and hydrophobic surfactant consumption increases, and the particle size of the silver powder obtained increases, and is mixed with hydrophobic surfactant to form organic solvent As the amount of solvent increases, the particle size of the prepared silver powder decreases. The silver powder prepared by the preparation method of the present application can be controlled in the particle size range of 0.5～2 μm, the particle size distribution of the silver powder particles is narrow, and the average particle size is small, and the smaller the particle size, the larger the specific surface area, the larger the tap density, and The surface area can reach 0.3-1.5m ² /g, and the tap density can reach 5.5-6.5g/cm ³ , reflecting the good particle dispersion.

2. From the comparison of Example 1 and Comparative Example 1, and the comparison of Example 5 and Comparative Example 5, it can be seen that when preparing the surface treatment agent, the emulsification stirring speed is lower than 1000r/min or higher than 30000r/min, and the quality of the silver powder obtained is obviously reduced . Accompanying drawing 1,2 are the micrographs of the silver powder that embodiment 1, comparative example 1 make respectively, and magnification is 10000 times, and the two compare visible, and the silver powder particle diameter that embodiment 1 makes is uniform, particle size distribution Narrow, small average particle size, good dispersion.

3. By comparison of Example 1 and Comparative Example 2, it can be seen that when the surface treatment agent is prepared, the activator used is a hydrophilic surfactant, and the quality of the obtained silver powder is obviously reduced.

4. From the comparison of Example 1 and Comparative Example 3, and the comparison of Example 5 and Comparative Example 4, it can be seen that when preparing the surface treatment agent, the amount of emulsified hot water and the amount of hydrophobic surfactant, the mass ratio is lower than 1: 1 or higher At a ratio of 10:1, the quality of the obtained silver powder is obviously reduced.

5. By comparison of Example 5 and Comparative Example 6, it can be seen that when the surface treatment agent is prepared, the emulsification and stirring time is lower than 1min, and the quality of the silver powder obtained is obviously reduced; , the emulsification and stirring time is higher than 3min, the quality of the prepared silver powder is equivalent, there is no improvement, but the cost of electricity and time is increased.

6. From the comparison of Example 1 and Comparative Example 8, it can be seen that when the surface treatment agent is prepared, the quality of the silver powder obtained is obviously reduced due to emulsification with unheated water.

7. From the comparison of Example 3 and Comparative Example 9, it can be seen that the dispersibility of the prepared silver powder is closely related to the heating conditions and hot water temperature in the process of preparing the surface treatment agent. Among them, when the heating conditions and hot water temperature are in the range of 80°C to 100°C, the emulsification effect of the surface treatment agent is good, and the dispersion of silver powder is high; when the heating conditions and hot water temperature are in the range of 30°C to 80°C , the temperature contributes a lot to the emulsification effect of the surface treatment agent. Generally speaking, when the temperature rises, the liquid droplets wrapped in the material system of the surface treatment agent are smaller, and then fully coated with silver powder, the prepared silver powder has better dispersibility . That is to say, when the temperature is lower than 30°C, the size of the droplets formed during the emulsification process is relatively large, and emulsification may not be achieved.

8. For the step of preparing the surface treatment agent in the technical scheme of this application, the heating conditions are 30°C to 100°C and the hot water temperature is 30°C to 100°C, preferably under the heating conditions of 80°C to 100°C and the hot water temperature of 80°C to 100°C , and choose a hydrophobic surfactant with a hydrophilic-lipophilic balance (HLB) of 0-10, silver powder with good dispersibility and narrow particle size distribution can be prepared; At a temperature of 30°C to 80°C, and a hydrophobic surfactant (such as Example 11 and Example 12) with a hydrophilic-lipophilic balance (HLB) of 8 to 10 can be prepared to produce Narrowly distributed silver powder.

Claims (10)

1. a preparation method of silver powder for conductive paste, is characterized in that comprising the following steps: Step S10, preparing wet silver powder: reacting the silver-containing solution with the reducing agent solution to form silver precipitates to form wet silver powder; Step S20, preparing a surface treatment agent: mixing a hydrophobic surfactant and a solvent to form an organic solvent, generating a solution under heating conditions, adding hot water, and stirring to form an emulsion surface treatment agent; Step S30, coating: adding a surface treatment agent into the wet silver powder, performing coating treatment, and drying to obtain silver powder. 2. The preparation method of silver powder for conductive paste according to claim 1, characterized in that: in step S10, the silver _- containing solution is one _of silver ammonia solution, Ag2O suspension or _Ag2CO3 suspension The reducing agent solution is one of glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium erythorbate, and p-diphenol. 3 . The method for preparing silver powder for conductive paste according to claim 1 , characterized in that: in step S10 , after the silver precipitate is formed, a dispersant is added and mixed evenly to form wet silver powder. 4 . 4. the preparation method of silver powder for conductive paste according to claim 3 is characterized in that: dispersant is wherein one of polyvinylpyrrolidone, citrate, oleylamine, organic compound with methylsiloxy functional group or Mix two or more. 5. The preparation method of silver powder for conductive paste according to claim 3, characterized in that: the amount of the dispersant is 0.01-5% of the silver content of the wet silver powder, the mole percentage. 6. The preparation method of silver powder for conductive paste according to claim 1, characterized in that: in step S20: the amount of hydrophobic surfactant is 0.0001% to 20% of the silver content of the wet silver powder, and the mass percentage is ; The hydrophobic surfactant and the solvent are mixed into an organic solvent according to the mass ratio of 1:80-10:80; the hot water and the hydrophobic surfactant are used according to the mass ratio of 1:1-10:1. 7. The preparation method of silver powder for conductive paste according to claim 1, characterized in that: in step S20, the hydrophobic surfactant is _C6 ～ _C22 saturated fatty acid, _C6 ～ _C22 unsaturated fatty acid, C ₆ -C ₂₂ esters, C ₆ -C ₂₂ amines, C ₆ -C ₂₂ fatty amines, C ₆ -C ₂₂ fatty amides, or a mixture of at least two of them, solvents are ethanol, acetone, ethylene glycol Alcohol, toluene, or a mixture of at least two of them. 8. The method for preparing silver powder for conductive paste according to claim 1, characterized in that: in step S20, the heating condition is 30°C-100°C, and the temperature of the hot water is 30°C-100°C. 9 . The method for preparing silver powder for conductive paste according to claim 1 , characterized in that: in step S20 , stirring is performed with a homogenizer at a speed of 1000-30000 r/min for 1-3 minutes to form an emulsion. 10. The method for preparing silver powder for conductive paste according to claim 1, characterized in that: in step S30, the surface treatment agent is first cooled to the temperature of the wet silver powder, and then added to the wet silver powder.

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