Surface-treated silver powder for conductive paste and preparation method thereof

Abstract

The present invention provides a surface-treated silver powder for conductive paste and a preparation method thereof. The preparation method comprises: first, mixing a silver-containing solution with a reducing agent to generate a solid silver suspension; then, mixing a nonionic surfactant with a solvent, heating the mixture to obtain a surfactant solution, adding water, and stirring to obtain a nonionic surfactant emulsion; adding the nonionic surfactant emulsion to the solid silver suspension, stirring, and filtering and drying to obtain the surface-treated silver powder; wherein the nonionic surfactant is a compound of cardanol polyoxyalkyl ether and polyoxyethylene stearyl alcohol ether. The silver powder of the present invention has good dispersibility and maintains its dispersibility well during long-term storage, thus having good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and in particular to surface-treated silver powder for conductive paste and a preparation method thereof. Background Art

[0002] Nano silver powder is an important conductive filler in conductive pastes. Silver powder is usually prepared by wet reduction. After drying, the prepared silver powder is very easy to agglomerate due to its large specific surface area and has poor dispersion.

[0003] In the prior art, the silver-containing paste formed is usually subjected to surface modification treatment during or after the wet reduction process to improve the dispersibility of the silver powder particles in the silver paste. Currently, various additives for surface treatment of silver powder include dispersants, surfactants, and other additives. Although a variety of different surface treatment additives have been developed in the prior art to improve the dispersibility of silver powder, during the long-term storage of silver powder, these surface modification components will cause the silver powder to aggregate again under the influence of the environment or natural failure, and the problem of reduced dispersibility will easily occur when the silver powder is reused.

[0004] In view of this, how to develop a silver powder preparation method to improve the stability of the silver powder's dispersion and maintain good dispersion of the silver powder after long-term storage has become one of the technical problems that need to be solved urgently. Summary of the Invention

[0005] In view of this, the present invention provides a surface-treated silver powder for conductive paste and a preparation method thereof. The silver powder prepared by the preparation method of the present invention has good dispersion effect and good storage stability.

[0006] The technical solution of the present invention is achieved as follows: The present invention provides a method for preparing surface-treated silver powder for conductive paste, which comprises the following steps:

[0007] Step 1: mixing a silver-containing solution with a reducing agent to generate a solid silver suspension;

[0008] Step 2: mixing a nonionic surfactant with a solvent, heating to obtain a surfactant solution, adding water, and stirring to obtain an emulsion of the nonionic surfactant;

[0009] Step 3: adding the nonionic surfactant emulsion to the solid silver suspension, stirring, filtering and drying to obtain surface-treated silver powder;

[0010] The nonionic surfactant is obtained by compounding cardanol polyoxyalkyl ether and polyoxyethylene stearyl alcohol ether.

[0011] In some embodiments, the structural formula of cardanol polyoxyalkyl ether is as shown in formula (I):

[0012] Wherein, R is one or more of -(CH2)7CH=CH(CH2)2CH3, -(CH2)7CH=CHCH2CH3, and -(CH2)7CH=CHCH3.

[0013] In some embodiments, in the nonionic surfactant, the mass ratio of cardanol polyoxyalkyl ether to polyoxyethylene stearyl alcohol ether is 1:(2-4).

[0014] In some embodiments, the silver-containing solution is one of a silver ammonia solution, an Ag2O suspension, or an Ag2CO3 suspension, and the reducing agent is one of glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium isoascorbate, and p-diphenol.

[0015] In some embodiments, the solvent is silicone oil.

[0016] In some embodiments, in step 1, after generating the solid silver suspension, the process further includes adding a dispersant, wherein the dispersant is sodium alginate.

[0017] In some embodiments, the amount of dispersant used is 0.1-0.5% by weight of the solid silver.

[0018] In some embodiments, in step 2, the heating temperature is 50-100° C., the temperature of the added water is 50-100° C., the stirring speed is 10,000-20,000 rpm, and the stirring time is 5-10 min.

[0019] In some embodiments, the amount of nonionic surfactant used is 1-4% of the mass of solid silver, the mass ratio of nonionic surfactant to solvent is 1:(20-40), and the mass ratio of nonionic surfactant to water is 1:(5-20).

[0020] In a second aspect, the present invention further provides silver powder for conductive paste, which is prepared by the above-mentioned preparation method.

[0021] The surface-treated silver powder for conductive paste and the preparation method thereof of the present invention have the following beneficial effects compared with the prior art:

[0022] The present invention adopts a compounded nonionic surfactant. Both cardanol polyoxyethylene ether and polyoxyethylene stearyl alcohol ether can form an adsorption layer on the surface of the silver powder, thereby providing a physical barrier to prevent the aggregation of silver powder particles. At the same time, through experimental verification, it is found that after some specific cardanol polyoxyethylene ethers and polyoxyethylene stearyl alcohol ethers are compounded in a certain proportion, the stability of the dispersion of the silver powder during long-term storage is significantly improved, and the storage time of the silver powder in the dry powder state is effectively extended. When the silver powder is reconfigured into a slurry, the dispersibility is maintained well. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0025] A method for preparing surface-treated silver powder for conductive paste comprises the following steps: reducing a silver-containing solution with a reducing agent to obtain a solid silver suspension, adding a prepared nonionic surfactant emulsion to the solid silver suspension, stirring the mixture for surface treatment reaction, and filtering and drying the mixture to obtain the surface-treated silver powder.

[0026] The nonionic surfactant is prepared by compounding cardanol polyoxyalkyl ether and polyoxyethylene stearyl alcohol ether.

[0027] The preferred structure of the cardanol polyoxyalkyl ether is shown in formula (I):

[0028] Wherein, R is one or more of -(CH2)7CH=CH(CH2)2CH3, -(CH2)7CH=CHCH2CH3, and -(CH2)7CH=CHCH3.

[0029] Preferably, in the nonionic surfactant, the mass ratio of cardanol polyoxyalkyl ether to polyoxyethylene stearyl alcohol ether is 1:(2-4).

[0030] The silver-containing solution is one of silver ammonia solution, Ag2O suspension or Ag2CO3 suspension, and the reducing agent is one of glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium isoascorbate and p-diphenol.

[0031] The solvent used is silicone oil.

[0032] In some embodiments, sodium alginate may be added after the solid silver suspension is generated.

[0033] The amount of the sodium alginate is preferably 0.1-0.5% of the mass of the generated solid silver. The mass of the solid silver can be obtained by theoretical calculation, based on the complete reduction of the silver in the silver-containing solution.

[0034] In step 2, the heating temperature is 50-100° C., the temperature of the added water is 50-100° C., the stirring speed is 10000-20000 rpm, and the stirring time is 5-10 min.

[0035] The dosage of the surfactant is 1-4% of the mass of the solid silver, the mass ratio of the surfactant to the solvent is 1:(20-40), and the mass ratio of the surfactant to water is 1:(5-20).

[0036] Example 1

[0037] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0038] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0039] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0040] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0041] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0042] Example 2

[0043] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0044] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0045] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0046] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CHCH2CH3.

[0047] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0048] Example 3

[0049] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0050] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0051] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0052] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CHCH3.

[0053] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0054] Example 4

[0055] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0056] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0057] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0058] The structure of cardanol polyoxyalkyl ether is: Where R is -(CH2) 14 CH3.

[0059] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0060] Example 5

[0061] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0062] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0063] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0064] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)5CH3.

[0065] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0066] Example 6

[0067] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0068] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0069] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0070] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0071] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 2% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0072] Example 7

[0073] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0074] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0075] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0076] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0077] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant used is 4% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0078] Example 8

[0079] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0080] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0081] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0082] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0083] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:2, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0084] Example 9

[0085] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0086] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0087] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0088] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0089] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:4, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0090] Example 10

[0091] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0092] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0093] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0094] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0095] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:40, and the mass ratio of nonionic surfactant to added hot water is 1:20.

[0096] Example 11

[0097] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0098] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, added with 80° C. water, and stirred in a homogenizer at 20,000 rpm for 80 minutes to obtain a nonionic surfactant emulsion.

[0099] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0100] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0101] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:2, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0102] Example 12

[0103] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution and stirred until the reaction is complete to obtain a suspension of solid silver.

[0104] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 100° C. water was added, and stirred at 30,000 rpm in a homogenizer for 50 minutes to obtain a nonionic surfactant emulsion.

[0105] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0106] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0107] The mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:2, the amount of nonionic surfactant is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0108] Example 13

[0109] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution, and stirred until the reaction is complete to obtain a solid silver suspension, and sodium alginate is added to the solid silver suspension.

[0110] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0111] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0112] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0113] The amount of sodium alginate used is 0.1% of the mass of solid silver in the solid silver suspension, the mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant used is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0114] Example 14

[0115] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution, and stirred until the reaction is complete to obtain a solid silver suspension, and sodium alginate is added to the solid silver suspension.

[0116] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0117] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0118] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0119] The amount of sodium alginate used is 0.3% of the mass of solid silver in the solid silver suspension, the mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant used is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0120] Example 15

[0121] A certain amount of silver ammonia solution is mixed with a sufficient amount of glucose solution, and stirred until the reaction is complete to obtain a solid silver suspension, and sodium alginate is added to the solid silver suspension.

[0122] Cardanol polyoxyalkyl ether, polyoxyethylene stearyl alcohol ether and silicone oil were mixed, heated to 50° C., stirred until dissolved, 50° C. water was added, and stirred at 10,000 rpm in a homogenizer for 10 minutes to obtain a nonionic surfactant emulsion.

[0123] The nonionic surfactant emulsion is added into the suspension of solid silver, stirred, filtered and dried to obtain the surface-treated silver powder.

[0124] The structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0125] The amount of sodium alginate used is 0.5% of the mass of solid silver in the solid silver suspension, the mass ratio of cardanol polyoxyalkyl ether: polyoxyethylene stearyl ether is 1:3, the amount of nonionic surfactant used is 1% of the mass of solid silver in the solid silver suspension, the mass ratio of nonionic surfactant: silicone oil is 1:20, and the mass ratio of nonionic surfactant to added hot water is 1:5.

[0126] Comparative Example 1

[0127] On the basis of Example 1, other conditions remain unchanged, except that the nonionic surfactant is cardanol polyoxyalkyl ether, and the structure of cardanol polyoxyalkyl ether is: Wherein, R is -(CH2)7CH=CH(CH2)2CH3.

[0128] Comparative Example 2

[0129] On the basis of Example 1, other conditions remain unchanged, except that the nonionic surfactant is polyoxyethylene stearyl ether.

[0130] Comparative Example 3

[0131] On the basis of Example 1, other conditions remain unchanged, except that polyoxyethylene stearyl ether is replaced by polyethylene glycol.

[0132] Comparative Example 4

[0133] On the basis of Example 1, other conditions remained unchanged, except that cardanol polyoxyalkyl ether was replaced by polyethylene glycol.

[0134] Comparative Example 5

[0135] On the basis of Example 1, other conditions remain unchanged, except that the amount of the nonionic surfactant is 0.5% of the mass of the solid silver in the solid silver suspension.

[0136] Comparative Example 6

[0137] On the basis of Example 1, other conditions remain unchanged, except that the amount of the nonionic surfactant is 5% of the mass of the solid silver in the solid silver suspension.

[0138] Comparative Example 7

[0139] On the basis of Example 1, other conditions remain unchanged, except that the mass ratio of cardanol polyoxyalkyl ether:polyoxyethylene stearyl ether is 1:1.

[0140] Comparative Example 8

[0141] On the basis of Example 1, other conditions remain unchanged, except that the mass ratio of cardanol polyoxyalkyl ether:polyoxyethylene stearyl ether is 1:5.

[0142] Comparative Example 9

[0143] On the basis of Example 14, other conditions remained unchanged, except that polyvinyl pyrrolidone was used instead of sodium alginate.

[0144] Comparative Example 10

[0145] On the basis of Comparative Example 3, sodium alginate was added to the solid silver suspension, and the amount of sodium alginate was 0.1% of the mass of the solid silver in the solid silver suspension.

[0146] The morphology of the silver powder prepared in the fir tree embodiment and the comparative example was tested, and the results were shown in the following table:

[0147] Grouping Average particle size / μm <![CDATA[Specific surface area m 2 / g]]> <![CDATA[Tap density g / cm 3 > Example 1 0.4 2.1 6.8 Example 2 0.4 2.2 7.1 Example 3 0.4 2.0 6.7 Example 4 0.7 1.6 6.3 Example 5 0.8 1.4 6.2 Example 6 0.5 1.9 6.4 Example 7 0.4 2.1 6.7 Example 8 0.5 2.0 6.4 Example 9 0.5 1.9 6.5 Example 10 0.4 2.1 6.6 Example 11 0.4 2.2 6.9 Example 12 0.4 2.0 6.7 Example 13 0.4 2.2 6.7 Example 14 0.3 2.3 6.8 Example 15 0.4 2.1 6.7 Comparative Example 1 1.6 0.9 5.3 Comparative Example 2 1.9 1.1 5.4 Comparative Example 3 1.4 1.3 5.5 Comparative Example 4 1.7 0.8 5.2 Comparative Example 5 0.7 1.7 6.1 Comparative Example 6 0.5 1.8 6.0 Comparative Example 7 0.6 1.7 6.1 Comparative Example 8 0.6 1.7 6.1 Comparative Example 9 0.4 2.5 6.7 Comparative Example 10 1.4 1.3 5.5

[0148] The silver powders prepared in Examples 1-15 and Comparative Examples 1-8 were subjected to aging treatment, respectively. The aging treatment environment was 30% in humidity and 20-30° C. in temperature. The aging treatment time was 30 days, 60 days, and 180 days, respectively. The average particle size of the silver powders after aging treatment was measured, and the data shown in the following table were obtained:

[0149] Grouping Average particle size after 30 days / μm Average particle size after 60 days / μm Average particle size after 180 days / μm Example 1 0.4 0.4 0.5 Example 2 0.4 0.4 0.4 Example 3 0.4 0.4 0.5 Example 4 0.7 0.8 1.1 Example 5 0.8 0.8 0.9 Example 6 0.5 0.5 0.5 Example 7 0.4 0.4 0.4 Example 8 0.5 0.6 0.8 Example 9 0.5 0.5 0.5 Example 10 0.4 0.4 0.5 Example 11 0.4 0.4 0.5 Example 12 0.4 0.4 0.5 Example 13 0.4 0.4 0.4 Example 14 0.3 0.3 0.3 Example 15 0.4 0.4 0.4 Comparative Example 1 1.9 2.4 3.1 Comparative Example 2 2.2 2.7 3.4 Comparative Example 3 1.5 1.7 2.0 Comparative Example 4 1.9 2.2 2.8 Comparative Example 5 0.8 0.9 1.2 Comparative Example 6 0.5 0.6 0.7 Comparative Example 7 0.7 0.9 1.2 Comparative Example 8 0.6 0.6 0.7 Comparative Example 9 0.4 0.5 0.7 Comparative Example 10 1.5 1.6 1.7

[0150] It can be seen from the above examples and comparative examples that the silver powder obtained by the preparation method of the present invention has good dispersion stability, especially dispersion stability after long-term storage in a dry state.

[0151] Comparison of the experimental data of Examples 1-3, 4, and 5 shows that when some R-group cardanol polyoxyalkyl ethers are used, the silver powder has a small size, good dispersibility, and good storage stability. Moreover, according to the data of Comparative Examples 1-4, it can be seen that the combination of the specific nonionic surfactants in this application achieves an unexpected improvement effect. Secondly, comparing the data of Example 1 with Examples 13-15 and Comparative Example 9, it can be seen that when sodium alginate is added as a dispersant on the basis of the specific nonionic surfactants in this application, the long-term storage stability of the silver powder is also enhanced. However, according to the data of Comparative Examples 3 and 10, even the combination of other nonionic surfactants does not produce a synergistic effect after the use of sodium alginate.

[0152] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing surface-treated silver powder for conductive paste, characterized in that: The steps include: Step 1: mixing a silver-containing solution with a reducing agent to generate a solid silver suspension; Step 2: mixing a nonionic surfactant with a solvent, heating to obtain a surfactant solution, adding water, and stirring to obtain an emulsion of the nonionic surfactant; Step 3: adding the nonionic surfactant emulsion to the solid silver suspension, stirring, filtering and drying to obtain surface-treated silver powder; The nonionic surfactant is obtained by compounding cardanol polyoxyalkyl ether and polyoxyethylene stearyl alcohol ether, and the mass ratio of cardanol polyoxyalkyl ether to polyoxyethylene stearyl alcohol ether is 1:(2-4).

2. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: The structural formula of the cardanol polyoxyalkyl ether is shown in formula (I): Wherein, R is one or more of -(CH2)7CH=CH(CH2)2CH3, -(CH2)7CH=CHCH2CH3, and -(CH2)7CH=CHCH3.

3. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: The silver-containing solution is one of silver ammonia solution, Ag2O suspension or Ag2CO3 suspension, and the reducing agent is one of glucose, formaldehyde, hydrazine hydrate, ascorbic acid, sodium isoascorbate and p-diphenol.

4. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: The solvent is silicone oil.

5. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: In step 1, after the solid silver suspension is generated, the method further comprises adding a dispersant, wherein the dispersant is sodium alginate.

6. The method for preparing surface-treated silver powder for conductive paste according to claim 5, wherein: The amount of the dispersant used is 0.1-0.5% of the mass of the solid silver.

7. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: In step 2, the heating temperature is 50-100° C., the temperature of the added water is 50-100° C., the stirring speed is 10000-20000 rpm, and the stirring time is 5-10 min.

8. The method for preparing surface-treated silver powder for conductive paste according to claim 1, wherein: The dosage of the nonionic surfactant is 1-4% of the mass of the solid silver, the mass ratio of the nonionic surfactant to the solvent is 1:(20-40), and the mass ratio of the nonionic surfactant to water is 1:(5-20).

9. A silver powder surface treated with a conductive paste, characterized in that: The silver powder is prepared by the preparation method described in any one of claims 1 to 8.

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