Preparation method of sphere-like superfine copper powder

Abstract

The invention discloses a preparation method of sphere-like superfine copper powder. The preparation method comprises the following construction steps that raw materials are subjected to extraction, replacement, primary centrifugal separation, primary reduction, secondary centrifugal separation, secondary reduction, tertiary centrifugal separation, antioxidant coating and drying operation, and then the sphere-like superfine copper powder is finally obtained. The method solves the problems of large powder particle size and easy introduction of impurities in various existing superfine copper powder processing technologies, or the problems of expensive equipment, high cost, low yield and easy oxidation of prepared copper powder in preparation. According to the method, the traditional copper powder preparation process is improved, the reaction system is simplified, the reaction is more stable and controllable, the cuprous oxide and the copper are prepared by sequentially reducing the bivalent copper salt, the reaction protective gas is added in the secondary reduction, and the antioxidant is added, so that the prepared superfine copper powder is prevented from being oxidized in the air.

Description

Technical Field

[0001] The invention relates to the field of preparation of quasi-spherical ultrafine copper powder, and in particular to a preparation method of quasi-spherical ultrafine copper powder. Background Art

[0002] As an emerging functional powder material, ultrafine copper powder is widely used in catalysts, electronics industry, and lubricants due to its large specific surface area and excellent thermal and electrical conductivity. Ultrafine copper powder is a key raw material for manufacturing high-performance electronic pastes. These electronic pastes are widely used in the terminal manufacturing of multilayer ceramic capacitors and play an important role in improving the performance of electronic components. As a lubricant additive, it has excellent anti-wear properties.

[0003] Traditional copper powder preparation methods include: 1. Mechanical grinding method for preparing copper powder has the problem of large powder particle size and easy introduction of impurities; 2. Electrolytic method for preparing copper powder has the characteristics of high purity, but its powder particle size is also large, and spherical / quasi-spherical powder cannot be produced; 3. Gas phase method for preparing ultrafine copper powder has high purity and narrow particle size distribution, but its equipment is expensive, requires argon as a protective gas, and the output is small; 4. Liquid phase reduction method for preparing copper powder has low equipment requirements and is easy to operate, but has problems such as fast reaction rate, easy powder agglomeration, wide particle size distribution, and easy oxidation.

[0004] The reaction system of the traditional liquid phase method for preparing copper powder is relatively complex, and there are many factors that affect the morphology and particle size of the copper powder, making the reaction difficult to control and unable to obtain a product with stable quality. For example, patent CN100544861C discloses "a method for preparing ultrafine copper powder", in which a divalent copper compound solution is reacted at a certain temperature using a reducing agent such as formaldehyde, sodium hypophosphite, and hydrazine hydrate, and ultrafine copper powder is obtained by two reductions. The method uses divalent copper ions as precursors, and the reducing agents all have strong reducing properties. The products obtained by the first reduction of the method are copper and cuprous oxide. Since the solution contains a large amount of divalent copper ions, there is also a reaction Cu2++Cu=Cu2O, which makes the reaction product difficult to control; and the divalent copper ions directly react with the strong reducing agent to generate copper. Due to the fast nucleation speed, the particle size distribution of the copper powder particles is very wide, the dispersibility is poor, and the agglomeration is serious. The agglomerates formed will be transformed into hard agglomerates after the second reduction, which affects the product morphology, and it is impossible to obtain copper powder with stable quality.

[0005] For example, patent CN101524763A discloses "a method for preparing submicron spherical copper powder", in which a divalent copper salt solution is added to a mixture of glucose, sodium hydroxide and a dispersant to obtain cuprous oxide, and finally hydrazine hydrate is added for reduction to obtain copper powder. In the first reduction process of the invention, divalent copper ions are added to the glucose and sodium hydroxide mixture, and the free copper ions instantly combine with hydroxide to form copper hydroxide. Copper hydroxide has poor stability. Under alkaline conditions, when the temperature is greater than 35°C, it will gradually dehydrate and decompose into copper oxide. Therefore, the reduced reactants have free divalent copper ions, copper hydroxide and copper oxide. At the same time, there is a hydrolysis reaction of copper hydroxide, which affects the formation of cuprous oxide. There are multiple reactions in the system, and the process is complicated and difficult to control. In addition, in the invention, glucose has strong reducing properties in high-concentration hydrogenation, and the secondary reducing agent hydrazine hydrate also has strong reducing properties, so the nucleation rate is fast, which will lead to a wide particle size distribution of copper powder particles, poor dispersibility, and serious agglomeration.

[0006] In addition, for example, the patent CN101524763A "A method for preparing submicron spherical copper powder" and the patent CN117483779A "A method for preparing submicron polyhedral copper powder" are not subjected to antioxidant treatment. Due to oxidation occurring during the reaction and the reaction Cu2++Cu=Cu2O, the final product is a mixture of copper, cupric oxide and cuprous oxide, and copper powder with stable quality cannot be obtained. The present invention eliminates the oxidizing effect of copper ions on copper powder by sequentially reducing divalent copper salt to prepare cuprous oxide and copper, increases the reaction protective atmosphere in the secondary reduction, and adds an antioxidant to solve the problem of oxidation of ultrafine copper powder in the air.

[0007] In order to solve the above problems, the present invention proposes a method for preparing spherical ultrafine copper powder with low equipment requirements, simple operation, low raw material cost, stable and controllable reaction, fast reaction rate and the ability to effectively prevent the finished copper powder from being oxidized.

[0008] Summary of the invention

[0009] (1) Technical issues to be solved

[0010] The purpose of the present invention is to improve the existing various ultrafine copper powder processing technologies, such as the problems of large powder particle size, inability to produce spherical / quasi-spherical powder, easy introduction of impurities, expensive equipment and high cost during preparation, but low output, and easy oxidation of copper powder after preparation. The present invention improves the traditional copper powder preparation process, simplifies the reaction system, makes the reaction more stable and controllable, and can set up multiple product lines of different specifications to meet the needs of customers. The method of preparing cuprous oxide and copper by reducing divalent copper salt in sequence eliminates the oxidation effect of copper ions on copper powder, adds reaction protection gas in the secondary reduction, and adds antioxidants to prevent the prepared ultrafine copper powder from being oxidized in the air, thereby solving the problems existing in the prior art.

[0011] (2) Technical solution

[0012] In order to solve the above technical problems, the present invention discloses a method for preparing spherical ultrafine copper powder, comprising the following steps:

[0013] 1) Extraction:

[0014] First, prepare the reagents: ① Feed solution: prepare the copper salt soluble solution into a solution with a copper ion concentration of 0.1-0.3 mol / L, and add sodium hydroxide solution to the acidic leaching solution / etching solution to adjust the pH to 2.5; ② Stripping solution: dilute the concentrated sulfuric acid to 1.8 mol / L with water; ③ Washing water: dilute the concentrated sulfuric acid to 0.1 mol / L, add 0.03 mol / L anhydrous copper sulfate and stir evenly; ④ Organic extraction solution: use a metal extraction agent for the extraction solution;

[0015] The extraction process is divided into three cycles, each of which is provided with one extraction, two washings and two stripping operations. Specifically, it is set to add organic extracts to separatory funnels A1, A2 and A3, add washing water to separatory funnels B1 and B2, and add stripping solutions to separatory funnels C1 and C2. In one cycle of operation, the feed liquid enters from A1, mixes with the organic extract in A1 for 3 minutes, stands for 2 minutes, and the organic extract after the reaction of A1 enters B1, and then enters B2, C1, and C2 respectively to mix; at this time, the feed liquid treated by A1 enters A2 to mix with the organic extract of A2, and the organic extract after the reaction in A2 enters the separatory funnel A1, mixes with the newly added feed liquid of A1, and then enters B2 from A1 respectively, C1, C2 are mixed; at this time, the feed liquid treated by A2 enters A3 and mixes with the organic extract of A3. After the reaction is allowed to stand, the raffinate is discharged. The organic extract after the reaction in A3 enters the separatory funnel A2 and mixes, then enters the separatory funnel A1 and mixes with the new feed liquid, and then enters B2, C1, and C2 from A1 to mix. In this process, the feed liquid always enters from the separatory funnel A1, is mixed with the wash water and then discharged, and the stripping liquid is mixed with the organic extract liquid for three cycles and then discharged. Then the discharge liquid is added to the new stripping liquid to form the extracted feed liquid, which is collected and then enters the next step. Among them, the ratio of the feed liquid extraction is 2-3, the ratio of the wash water is 10-20, and the ratio of the stripping is 2-3. The chemical reaction formula generated in this step is mainly:

[0016] Cu 2+ +2RH=CuR2+2H + ;

[0017] 2) Replacement:

[0018] The extracted liquid obtained in the extraction step is diluted, and the diluted extracted liquid is added to the reactor, and a dispersant is added simultaneously and stirred in the reactor for 5 minutes, and a sodium hydroxide solution is slowly added dropwise to adjust the pH to 6-7, and stirred for 30 minutes, and the reaction temperature is controlled to 40-50°C. The chemical reaction formula generated in this step is mainly:

[0019] 2NaOH+CuSO4=Cu(OH)2↓+Na2SO4;

[0020] 3) Primary centrifugation:

[0021] 2) separating the product in the replacement step by a centrifuge to obtain copper hydroxide;

[0022] 4) One-time restoration:

[0023] The copper hydroxide separated by centrifugation in step 3) is added to pure water and glucose solution, with glucose as a reducing agent, to obtain a copper hydroxide suspension, which is mixed and stirred in a reactor for 5 minutes, heated to 65°C, and then slowly added with sodium hydroxide solution until the reactant turns brick red, and the reaction is continued for 30 minutes. The chemical reaction formula generated in this step is mainly:

[0024] CH2OH(CHOH)4CHO+2Cu(OH)2=CH2OH(CHOH)4COOH+Cu2O↓+2H2O;

[0025] 5) Secondary centrifugation:

[0026] Centrifuge the liquid in step 4) to obtain a cuprous oxide suspension, add pure water, stir, wash with pure water, and centrifuge again to obtain cuprous oxide powder;

[0027] 6) Secondary reduction:

[0028] The cuprous oxide powder obtained in step 5) is added to pure water and a dispersant in a reactor and stirred for 5 minutes. Nitrogen is introduced into the reactor and the oxygen content is reduced to less than 10,000 ppm by exhausting air. The solution is heated to 50° C. and a portion of the reducing agent is added dropwise; the solution is heated to 60° C. and the remaining reducing agent is added dropwise. The reaction is continued at this temperature for 30 minutes.

[0029] 7) Three times centrifugation:

[0030] Centrifuge the liquid in step 6) to obtain a copper powder suspension, add anhydrous ethanol for washing, and then centrifuge to obtain copper powder;

[0031] 8) Antioxidant coating:

[0032] A certain amount of antioxidant is prepared into a solution, mixed with the copper powder obtained in step 7) in pure water or anhydrous ethanol, and stirred by ultrasound for 10-20 minutes, and centrifuged to obtain spherical ultrafine copper powder.

[0033] Preferably, the extracting liquid in step 1) is 25% of Mextral5640H metal extractant.

[0034] Preferably, the dispersant in step 2) and step 6) is polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS, and the mass ratio of the dispersant to copper ions is 0.05-0.2.

[0035] Preferably, in step 2), sodium hydroxide solution is slowly added dropwise to adjust the pH value to 6.7.

[0036] Preferably, in the first reduction step 4), the molar ratio of copper hydroxide to copper ions is: n(NaOH): n(Cu 2+)=1.2:1, the molar ratio of glucose to copper ion in the first reduction is: n(CH2OH(CHOH)4CHO):n(Cu 2+ )=1—2:1.

[0037] Preferably, in the step 2), the extraction solution is diluted to a copper ion concentration in the range of 0.1-0.2 mol / L.

[0038] Preferably, the concentration of the sodium hydroxide solution added in step 1), step 2) and step 4) is 10 mol / L, and the concentration of the glucose solution added in step 4) is 2.5 mol / L.

[0039] Preferably, in step 6), the reducing agent is hydrazine hydrate or sodium hypophosphite. If hydrazine hydrate is the secondary reducing agent, the concentration is 6.6 mol / L. The molar ratio of hydrazine hydrate to copper ions in the secondary reduction is: n(N2H4·H2O): n(Cu 2+ )=0.2-0.4:1, the chemical reaction formula produced in this step is mainly:

[0040] 2Cu2O+N2H4=4Cu+N2↑+2H2O;

[0041] If sodium hypophosphite is used as the secondary reducing agent with a concentration of 5.6 mol / L, the molar ratio of sodium hypophosphite to copper ions in the secondary reduction is: n(NaH2PO2): n(Cu 2+ )=0.4-0.8:1, the chemical reaction formula produced in this step is mainly:

[0042] Cu2O+NaH2PO2=2Cu+NaH2PO3.

[0043] Preferably, the antioxidant in step 8) is one or more of benzotriazole BTA, oleic acid or gelatin, and the mass ratio of the antioxidant to copper ions is 1%-5%.

[0044] Preferably, the step 5) secondary centrifugation and the step 7) tertiary centrifugation are repeated multiple times.

[0045] Preferably, the copper salt soluble solution can extract copper from copper-containing ore leaching solution, circuit etching solution, and waste and waste water.

[0046] (3) Beneficial effects

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] 1. Low equipment requirements and easy operation: Compared with traditional copper powder manufacturing methods such as physical vapor deposition and grinding methods, the liquid phase reduction method uses relatively simple equipment. The product can be obtained using a separatory funnel and a reactor. The process is short and easy to operate. It only needs to be operated at room temperature and pressure, which is easy to control and will not introduce impurities. This makes the production process more flexible and adaptable, and easy to industrialize.

[0049] 2. Low cost of raw materials: Traditional methods use expensive copper materials as raw materials, and the raw materials used in the liquid phase method are mostly cheap soluble copper salts. The present invention also combines an extraction process, not only using soluble copper salts as raw materials, but also extracting copper elements from copper-containing ore leachate, circuit etching solution, waste and wastewater, thereby achieving efficient recovery of copper resources. Compared with the traditional liquid phase method, the copper salt after extraction has high purity and controllable quality, which improves product stability, further reduces material costs, and reduces environmental pollution.

[0050] 3. The reaction is stable and controllable: The present invention has simple equipment, short process flow, convenient operation, simple reaction conditions, and the raw materials are ensured to have stable concentration and chemical element content through extraction process. The liquid phase reduction method can control the morphology and particle size of copper powder through the concentration of precursor, the type of secondary reducing agent, reaction temperature and time reaction conditions;

[0051] The traditional liquid phase method for preparing copper powder has a relatively complex reaction system, and many factors affect the morphology and particle size of the prepared copper powder, making the reaction difficult to control and unable to obtain a product with stable quality. The present invention improves the traditional copper powder preparation process, simplifies the reaction system, and makes the reaction more stable and controllable.

[0052] The present invention uses glucose for pre-reduction. Since glucose has weak reducing property, it can only reduce divalent copper ions to cuprous oxide. By using glucose pre-reduction and hydrazine hydrate addition in two steps, the reaction process is prolonged, the complexity of the reaction in the system is reduced, and cuprous oxide with good dispersibility and uniform particle size can be obtained. As a precursor for secondary reduction, the morphology of the powder can be retained to a certain extent, and finally copper powder with uniform particle size is obtained.

[0053] The present invention obtains stable copper hydroxide as a reduced precursor through a process, and no hydrolysis reaction occurs when heated, so that the reduction reaction is single, easy to control, and the product is stable. In the reduction reaction, glucose is first mixed with the precursor, and glucose does not have reducing property at this time, and then sodium hydroxide is slowly added, the system is alkaline, and the copper hydroxide is gradually reduced to cuprous oxide, so that the nucleation process is stabilized in this way, and cuprous oxide with good dispersibility and uniform particle size is obtained. The secondary reduction reaction is controlled by adding a reducing agent twice and controlling the temperature, and the problem that hydrazine hydrate has strong reducing property and fast nucleation speed is solved.

[0054] 4. Improvement of powder oxidation: Ultrafine copper powder is easy to react with oxygen in the air to generate copper oxide due to its large specific surface area, which seriously affects its performance. The present invention eliminates the oxidizing effect of copper ions on copper powder by reducing divalent copper salt in sequence to prepare cuprous oxide and copper, adds reaction protection gas in the secondary reduction, and adds antioxidants to solve the problem of ultrafine copper powder oxidation in the air. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Attached Figure 1 is a flow chart of the preparation process of the present invention;

[0056] Attached Figure 2 is a process flow chart of the extraction step of the present invention;

[0057] Attached Figure 3 A scanning electron microscope photograph of the ultrafine copper powder prepared in Example 1 of the present invention;

[0058] Attached Figure 4 This is a scanning electron microscope photograph of the ultrafine copper powder prepared in Example 2 of the present invention;

[0059] Attached Figure 5 This is a scanning electron microscope photograph of the ultrafine copper powder prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0060] The present invention is described in detail below using different manufacturing processes. The examples listed can help technicians in this field to better understand the present invention, but do not limit the present invention in any form. For example, the present invention can be expanded to be applied in the production of papermaking technology.

[0061] Embodiment 1:

[0062] A method for preparing spherical ultrafine copper powder comprises the following steps:

[0063] 1) Extraction:

[0064] First, the reagents are prepared: ① Feed solution: prepare the copper salt soluble solution into a solution with a copper ion concentration of 0.3 mol / L, and add 10 mol / L sodium hydroxide solution to the acidic leaching solution / etching solution to adjust the pH to 2.5; ② Stripping solution: dilute the concentrated sulfuric acid to 1.8 mol / L with water; ③ Washing water: dilute the concentrated sulfuric acid to 0.1 mol / L, add 0.03 mol / L anhydrous copper sulfate and stir evenly; ④ Organic extraction solution: use 25% Mextral5640H metal extraction agent as the extraction solution;

[0065] The extraction process is divided into three cycles, each of which is provided with one extraction, two washings and two stripping operations. Specifically, it is set to add organic extracts to separatory funnels A1, A2 and A3, add washing water to separatory funnels B1 and B2, and add stripping solutions to separatory funnels C1 and C2. In one cycle of operation, the feed liquid enters from A1, mixes with the organic extract in A1 for 3 minutes, stands for 2 minutes, and the organic extract after the reaction of A1 enters B1, and then enters B2, C1, and C2 respectively to mix; at this time, the feed liquid treated by A1 enters A2 to mix with the organic extract of A2, and the organic extract after the reaction in A2 enters the separatory funnel A1, mixes with the newly added feed liquid of A1, and then enters B2 from A1 respectively, C1, C2 are mixed; at this time, the feed liquid treated by A2 enters A3 and mixes with the organic extract of A3. After the reaction is allowed to stand, the raffinate is discharged. The organic extract after the reaction in A3 enters the separatory funnel A2 and mixes, then enters the separatory funnel A1 and mixes with the new feed liquid, and then enters B2, C1, and C2 from A1 to mix. In this process, the feed liquid always enters from the separatory funnel A1, is mixed with the wash water and then discharged, and the stripping liquid is mixed with the organic extract liquid for three cycles and then discharged. Then the discharge liquid is added to the new stripping liquid to form the extracted feed liquid, which is collected and then enters the next step. Among them, the ratio of the feed liquid extraction is 2-3, the ratio of the wash water is 10-20, and the ratio of the stripping is 2-3. The chemical reaction formula generated in this step is mainly:

[0066] Cu 2+ +2RH=CuR2+2H + ;

[0067] 2) Replacement:

[0068] The extracted liquid obtained in the extraction step is diluted to a copper ion concentration of 0.2 mol / s, the diluted extracted liquid is added to the reactor, polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS is added simultaneously, and the mixture is stirred and mixed in the reactor for 5 minutes, 10 mol / L sodium hydroxide solution is slowly added dropwise to adjust the pH to 6.7, and the mixture is stirred and mixed for 30 minutes, and the reaction temperature is controlled to 45°C;

[0069] 3) Primary centrifugation:

[0070] 2) separating the product in the replacement step by a centrifuge to obtain copper hydroxide;

[0071] 4) One-time restoration:

[0072] The copper hydroxide separated by centrifugation in step 3) is added with pure water and 2.5 mol / L glucose solution, with glucose as a reducing agent, to obtain a copper hydroxide suspension, which is mixed and stirred in a reactor for 5 minutes, heated to 65°C, and then slowly added with 10 mol / L sodium hydroxide solution until the reactant turns brick red, and the reaction is continued for 30 minutes, wherein the molar ratio of copper hydroxide to copper ion is: n(NaOH): n(Cu 2+ )=1.2:1, the molar ratio of glucose to copper ion in the first reduction is: n(CH2OH(CHOH)4CHO):n(Cu 2+ )=2:1;

[0073] 5) Secondary centrifugation:

[0074] Centrifuge the liquid in step 4) to obtain a cuprous oxide suspension, add pure water, stir, wash with pure water, and centrifuge again to obtain cuprous oxide powder. This step needs to be performed multiple times;

[0075] 6) Secondary reduction:

[0076] The cuprous oxide powder obtained in step 5) is added with pure water and polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS, and stirred and mixed in a reactor for 5 minutes. Nitrogen is introduced into the reactor, and the oxygen content is reduced to less than 10,000 ppm by exhausting air. The solution is heated to 50° C., and part of hydrazine hydrate or sodium hypophosphite is added dropwise; the temperature is raised to 60° C., and the remaining hydrazine hydrate or sodium hypophosphite is added dropwise, and the reaction is continued for 30 minutes of heat preservation, wherein the mass ratio of polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS to copper ions in steps 2) and 6) is 0.05:

[0077] 7) Three times centrifugation:

[0078] Centrifuge the liquid in step 6) to obtain a copper powder suspension, add anhydrous ethanol for washing, and then centrifuge to obtain copper powder. This step needs to be performed multiple times;

[0079] 8) Antioxidant coating:

[0080] Benzotriazole BTA, oleic acid or gelatin are prepared into a solution, and the solution is mixed with the copper powder obtained in step 7) in pure water or anhydrous ethanol, wherein the mass ratio of antioxidants such as benzotriazole BTA, oleic acid or gelatin to copper ions is 1%, and the solution is ultrasonically stirred for 20 minutes, and then centrifuged and dried to obtain spherical ultrafine copper powder.

[0081] Embodiment 2:

[0082] A method for preparing spherical ultrafine copper powder comprises the following steps:

[0083] 1) Extraction:

[0084] First, the reagents are prepared: ① Feed solution: prepare the copper salt soluble solution into a solution with a copper ion concentration of 0.15 mol / L, and add 10 mol / L sodium hydroxide solution to the acidic leaching solution / etching solution to adjust the pH to 2.5; ② Stripping solution: dilute the concentrated sulfuric acid to 1.8 mol / L with water; ③ Washing water: dilute the concentrated sulfuric acid to 0.1 mol / L, add 0.03 mol / L anhydrous copper sulfate and stir evenly; ④ Organic extract: use 25% Mextral5640H metal extractant as the extract;

[0085] The extraction process is divided into three cycles, each of which is provided with one extraction, two washings and two stripping operations. Specifically, it is set to add organic extracts to separatory funnels A1, A2 and A3, add washing water to separatory funnels B1 and B2, and add stripping solutions to separatory funnels C1 and C2. In one cycle of operation, the feed liquid enters from A1, mixes with the organic extract in A1 for 3 minutes, stands for 2 minutes, and the organic extract after the reaction of A1 enters B1, and then enters B2, C1, and C2 respectively to mix; at this time, the feed liquid treated by A1 enters A2 to mix with the organic extract of A2, and the organic extract after the reaction in A2 enters the separatory funnel A1, mixes with the newly added feed liquid of A1, and then enters B2 from A1 respectively, C1, C2 are mixed; at this time, the feed liquid treated by A2 enters A3 and mixes with the organic extract of A3. After the reaction is allowed to stand, the raffinate is discharged. The organic extract after the reaction in A3 enters the separatory funnel A2 and mixes, then enters the separatory funnel A1 and mixes with the new feed liquid, and then enters B2, C1, and C2 from A1 to mix. In this process, the feed liquid always enters from the separatory funnel A1, is mixed with the wash water and then discharged, and the stripping liquid is mixed with the organic extract liquid for three cycles and then discharged. Then the discharge liquid is added to the new stripping liquid to form the extracted feed liquid, which is collected and then enters the next step. Among them, the ratio of the feed liquid extraction is 2-3, the ratio of the wash water is 10-20, and the ratio of the stripping is 2-3. The chemical reaction formula generated in this step is mainly:

[0086] Cu 2+ +2RH=CuR2+2H + ;

[0087] 2) Replacement:

[0088] The extracted liquid obtained in the extraction step is diluted to a copper ion concentration of 0.1 mol / s, the diluted extracted liquid is added to the reactor, polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS is added simultaneously, and the mixture is stirred and mixed in the reactor for 5 minutes, 10 mol / L sodium hydroxide solution is slowly added dropwise to adjust the pH to 7, and the mixture is stirred and mixed for 30 minutes, and the reaction temperature is controlled to be 50°C;

[0089] 3) Primary centrifugation:

[0090] 2) separating the product in the replacement step by a centrifuge to obtain copper hydroxide;

[0091] 4) One-time restoration:

[0092] The copper hydroxide separated by centrifugation in step 3) is added with pure water and 2.5 mol / L glucose solution, with glucose as a reducing agent, to obtain a copper hydroxide suspension, which is mixed and stirred in a reactor for 5 minutes, heated to 65°C, and then slowly added with 10 mol / L sodium hydroxide solution until the reactant turns brick red, and the reaction is continued for 30 minutes, wherein the molar ratio of copper hydroxide to copper ion is: n(NaOH): n(Cu 2+ )=1.2:1, the molar ratio of glucose to copper ion in the first reduction is: n(CH2OH(CHOH)4CHO):n(Cu 2+ )=1:1;

[0093] 5) Secondary centrifugation:

[0094] Centrifuge the liquid in step 4) to obtain a cuprous oxide suspension, add pure water, stir, wash with pure water, and centrifuge again to obtain cuprous oxide powder. This step needs to be performed multiple times;

[0095] 6) Secondary reduction:

[0096] The cuprous oxide powder obtained in step 5) is added with pure water and polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS and stirred in a reactor for 5 minutes. Nitrogen is introduced into the reactor and the oxygen content is reduced to less than 10,000 ppm by exhausting air. The solution is heated to 50° C. and a portion of hydrazine hydrate or sodium hypophosphite is added dropwise; the temperature is raised to 60° C. and the remaining hydrazine hydrate or sodium hypophosphite is added dropwise. The reaction is continued at this temperature for 30 minutes. The mass ratio of polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS to copper ions in steps 2) and 6) is 0.2:

[0097] 7) Three times centrifugation:

[0098] Centrifuge the liquid in step 6) to obtain a copper powder suspension, add anhydrous ethanol for washing, and then centrifuge to obtain copper powder. This step needs to be performed multiple times;

[0099] 8) Antioxidant coating:

[0100] Benzotriazole BTA, oleic acid or gelatin are prepared into a solution, and the solution is mixed with the copper powder obtained in step 7) in pure water or anhydrous ethanol, wherein the mass ratio of antioxidants such as benzotriazole BTA, oleic acid or gelatin to copper ions is 5%, and the solution is ultrasonically stirred for 10 minutes and centrifuged to obtain spherical ultrafine copper powder.

[0101] Embodiment 3:

[0102] A method for preparing spherical ultrafine copper powder comprises the following steps:

[0103] 1) Extraction:

[0104] First, the reagents are prepared: ① Feed solution: prepare the copper salt soluble solution into a solution with a copper ion concentration of 0.4 mol / L, and add 10 mol / L sodium hydroxide solution to the acidic leaching solution / etching solution to adjust the pH to 2.5; ② Stripping solution: dilute the concentrated sulfuric acid to 1.8 mol / L with water; ③ Washing water: dilute the concentrated sulfuric acid to 0.1 mol / L, add 0.03 mol / L anhydrous copper sulfate and stir evenly; ④ Organic extraction solution: use 25% Mextral5640H metal extraction agent as the extraction solution;

[0105] The extraction process is divided into three cycles, each of which is provided with one extraction, two washings and two stripping operations. Specifically, it is set to add organic extracts to separatory funnels A1, A2 and A3, add washing water to separatory funnels B1 and B2, and add stripping solutions to separatory funnels C1 and C2. In one cycle of operation, the feed liquid enters from A1, mixes with the organic extract in A1 for 3 minutes, stands for 2 minutes, and the organic extract after the reaction of A1 enters B1, and then enters B2, C1, and C2 respectively to mix; at this time, the feed liquid treated by A1 enters A2 to mix with the organic extract of A2, and the organic extract after the reaction in A2 enters the separatory funnel A1, mixes with the newly added feed liquid of A1, and then enters B2 from A1 respectively, C1, C2 are mixed; at this time, the feed liquid treated by A2 enters A3 and mixes with the organic extract of A3. After the reaction is allowed to stand, the raffinate is discharged. The organic extract after the reaction in A3 enters the separatory funnel A2 and mixes, then enters the separatory funnel A1 and mixes with the new feed liquid, and then enters B2, C1, and C2 from A1 to mix. In this process, the feed liquid always enters from the separatory funnel A1, is mixed with the wash water and then discharged, and the stripping liquid is mixed with the organic extract liquid for three cycles and then discharged. Then the discharge liquid is added to the new stripping liquid to form the extracted feed liquid, which is collected and then enters the next step. Among them, the ratio of the feed liquid extraction is 2-3, the ratio of the wash water is 10-20, and the ratio of the stripping is 2-3. The chemical reaction formula generated in this step is mainly:

[0106] Cu 2+ +2RH=CuR2+2H + ;

[0107] 2) Replacement:

[0108] The extracted liquid obtained in the extraction step is diluted to a copper ion concentration of 0.15 mol / s, the diluted extracted liquid is added to the reactor, polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS is added simultaneously, and the mixture is stirred and mixed in the reactor for 5 minutes, 10 mol / L sodium hydroxide solution is slowly added dropwise to adjust the pH to 6, and the mixture is stirred and mixed for 30 minutes, and the reaction temperature is controlled to be 40°C;

[0109] 3) Primary centrifugation:

[0110] 2) separating the product in the replacement step by a centrifuge to obtain copper hydroxide;

[0111] 4) One-time restoration:

[0112] The copper hydroxide separated by centrifugation in step 3) is added with pure water and 2.5 mol / L glucose solution, with glucose as a reducing agent, to obtain a copper hydroxide suspension, which is mixed and stirred in a reactor for 5 minutes, heated to 65°C, and then slowly added with 10 mol / L sodium hydroxide solution until the reactant turns brick red, and the reaction is continued for 30 minutes, wherein the molar ratio of copper hydroxide to copper ion is: n(NaOH): n(Cu 2+ )=1.2:1, the molar ratio of glucose to copper ion in the first reduction is: n(CH2OH(CHOH)4CHO):n(Cu 2+ )=1.5:1;

[0113] 5) Secondary centrifugation:

[0114] Centrifuge the liquid in step 4) to obtain a cuprous oxide suspension, add pure water, stir, wash with pure water, and centrifuge again to obtain cuprous oxide powder. This step needs to be performed multiple times;

[0115] 6) Secondary reduction:

[0116] The cuprous oxide powder obtained in step 5) is added with pure water and polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS, and stirred and mixed in a reactor for 5 minutes. Nitrogen is introduced into the reactor, and the oxygen content is reduced to less than 10,000 ppm by exhausting air. The solution is heated to 50° C., and part of hydrazine hydrate or sodium hypophosphite is added dropwise; the temperature is raised to 60° C., and the remaining hydrazine hydrate or sodium hypophosphite is added dropwise, and the reaction is continued for 30 minutes of heat preservation, wherein the mass ratio of polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS to copper ions in steps 2) and 6) is 0.1:

[0117] 7) Three times centrifugation:

[0118] Centrifuge the liquid in step 6) to obtain a copper powder suspension, add anhydrous ethanol for washing, and then centrifuge to obtain copper powder. This step needs to be performed multiple times;

[0119] 8) Antioxidant coating:

[0120] Benzotriazole BTA, oleic acid or gelatin are prepared into a solution, and the solution is mixed with the copper powder obtained in step 7) in pure water or anhydrous ethanol, wherein the mass ratio of antioxidants such as benzotriazole BTA, oleic acid or gelatin to copper ions is 2.5%, and the solution is ultrasonically stirred for 15 minutes and centrifugally dried to obtain spherical ultrafine copper powder.

[0121] After obtaining the above products, we conducted tests and obtained the following comparative data:

[0122]

[0123] It can be concluded from the above experimental data that the spherical ultrafine copper powder prepared by the present invention has a small particle size, with an average particle size of 1 μm, and no impurities will be introduced during the operation.

[0124] After processing, the impurity content is less than 0.01%, and the purity of the sample is above 99.9%, which is relatively high.

[0125] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing spherical ultrafine copper powder, characterized in that: It includes the following steps: 1) Extraction: First, prepare the reagents: ① Feed solution: prepare the copper salt soluble solution into a solution with a copper ion concentration of 0.1-0.3 mol / L, and add sodium hydroxide solution to the acidic leaching solution / etching solution to adjust the pH to 2.5; ② Stripping solution: dilute the concentrated sulfuric acid to 1.8 mol / L with water; ③ Washing water: dilute the concentrated sulfuric acid to 0.1 mol / L, add 0.03 mol / L anhydrous copper sulfate and stir evenly; ④ Organic extraction solution: use a metal extraction agent for the extraction solution; The extraction process is divided into three cycles, each of which is provided with one extraction, two washings and two stripping operations. Specifically, it is set to add organic extracts to separatory funnels A1, A2 and A3, add washing water to separatory funnels B1 and B2, and add stripping solutions to separatory funnels C1 and C2. In one cycle of operation, the feed liquid enters from A1, mixes with the organic extract in A1 for 3 minutes, stands for 2 minutes, and the organic extract after the reaction of A1 enters B1, and then enters B2, C1, and C2 respectively to mix; at this time, the feed liquid treated by A1 enters A2 to mix with the organic extract of A2, and the organic extract after the reaction in A2 enters the separatory funnel A1, mixes with the newly added feed liquid of A1, and then enters B2 from A1 respectively, C1, C2 are mixed; at this time, the feed liquid treated by A2 enters A3 and mixes with the organic extract of A3. After the reaction is allowed to stand, the raffinate is discharged. The organic extract after the reaction in A3 enters the separatory funnel A2 and mixes, then enters the separatory funnel A1 and mixes with the new feed liquid, and then enters B2, C1, and C2 from A1 to mix. In this process, the feed liquid always enters from the separatory funnel A1, is mixed with the wash water and then discharged, and the stripping liquid is mixed with the organic extract liquid for three cycles and then discharged. Then the discharge liquid is added to the new stripping liquid to form the extracted feed liquid, which is collected and then enters the next step. Among them, the ratio of the feed liquid extraction is 2-3, the ratio of the wash water is 10-20, and the ratio of the stripping is 2-3. The chemical reaction formula generated in this step is mainly: <h2 style=";text-align:left;direction:ltr">Cu<h2 style=";text-align:left;direction:ltr"> 2+ <h2 style=";text-align:left;direction:ltr"> +2RH=CuR2+2H<h2 style=";text-align:left;direction:ltr"> + <h2 style=";text-align:left;direction:ltr"> ; 2) Replacement: The extracted liquid obtained in the extraction step is diluted, and the diluted extracted liquid is added to the reactor, and polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS is added simultaneously and stirred in the reactor for 5 minutes, and sodium hydroxide solution is slowly added dropwise to adjust the pH to 6-7, and stirred for 30 minutes, and the reaction temperature is controlled to 40-50°C. The chemical reaction formula generated in this step is mainly: 2NaOH+CuSO4=Cu(OH)2↓+Na2SO4; 3) Primary centrifugation: 2) separating the product in the replacement step by a centrifuge to obtain copper hydroxide; 4) One-time restoration: The copper hydroxide separated by centrifugation in step 3) is added to pure water and glucose solution, with glucose as a reducing agent, to obtain a copper hydroxide suspension, which is mixed and stirred in a reactor for 5 minutes, heated to 65°C, and then slowly added with sodium hydroxide solution until the reactant turns brick red, and the reaction is continued for 30 minutes. The chemical reaction formula generated in this step is mainly: CH2OH(CHOH)4CHO+2Cu(OH)2=CH2OH(CHOH)4COOH+Cu2O↓+2H2O; 5) Secondary centrifugation: Centrifuge the liquid in step 4) to obtain a cuprous oxide suspension, add pure water, stir, wash with pure water, and centrifuge again to obtain cuprous oxide powder; 6) Secondary reduction: The cuprous oxide powder obtained in step 5) is added to pure water and a dispersant in a reactor and stirred for 5 minutes. Nitrogen is introduced into the reactor and the oxygen content is reduced to less than 10,000 ppm by exhausting air. The solution is heated to 50° C. and a portion of the reducing agent is added dropwise; the solution is heated to 60° C. and the remaining reducing agent is added dropwise. The reaction is continued at this temperature for 30 minutes. 7) Three times centrifugation: Centrifuge the liquid in step 6) to obtain a copper powder suspension, add anhydrous ethanol for washing, and then centrifuge to obtain copper powder; 8) Antioxidant coating: A certain amount of antioxidant is prepared into a solution, mixed with the copper powder obtained in step 7) in pure water or anhydrous ethanol, and stirred by ultrasound for 10-20 minutes, and centrifuged to obtain spherical ultrafine copper powder.

2. The method for preparing spherical ultrafine copper powder according to claim 1, characterized in that: The extracting liquid in step 1) is 25% of Mextral5640H metal extractant.

3. The method for preparing spherical ultrafine copper powder according to claim 1, characterized in that: The dispersant in step 2) and step 6) is polyvinyl pyrrolidone PVP-k30 or sodium dodecyl sulfate SDS, and the mass ratio of the dispersant to copper ions is 0.05-0.

2.

4. The method for preparing spherical ultrafine copper powder according to claim 1, characterized in that: In the step 2), sodium hydroxide solution is slowly added dropwise to adjust the pH to 6.

7.

5. The method for preparing spherical ultrafine copper powder according to claim 1, characterized in that: In step 4), the molar ratio of copper hydroxide to copper ions is: n(NaOH): n(Cu 2+ )=1.2:1, the molar ratio of glucose to copper ion in the first reduction is: n(CH2OH(CHOH)4CHO):n(Cu 2+ )=1—2:

1.

6. A method for preparing spherical ultrafine copper powder according to any one of claims 1 to 5, characterized in that: In the step 2), the extracted solution is diluted to a copper ion concentration within the range of 0.1-0.2 mol / L.

7. The method for preparing spherical ultrafine copper powder according to claim 6, characterized in that: The concentration of the sodium hydroxide solution added in step 1), step 2) and step 4) is 10 mol / L, and the concentration of the glucose solution added in step 4) is 2.5 mol / L.

8. The method for preparing spherical ultrafine copper powder according to claim 7, characterized in that: In the step 6), the reducing agent is hydrazine hydrate or sodium hypophosphite. If hydrazine hydrate is used as the secondary reducing agent, the concentration is 6.6 mol / L. The molar ratio of hydrazine hydrate to copper ions in the secondary reduction is: n(N2H4·H2O): n(Cu 2+ )=0.2-0.4:1, the chemical reaction formula produced in this step is mainly: 2Cu2O+N2H4=4Cu+N2↑+2H2O; If sodium hypophosphite is used as the secondary reducing agent with a concentration of 5.6 mol / L, the molar ratio of sodium hypophosphite to copper ions in the secondary reduction is: n(NaH2PO2): n(Cu 2+ )=0.4-0.8:1, the chemical reaction formula produced in this step is mainly: Cu2O+NaH2PO2=2Cu+NaH2PO3.

9. The method for preparing spherical ultrafine copper powder according to claim 8, characterized in that: The antioxidant in step 8) is one or more of benzotriazole BTA, oleic acid or gelatin, and the mass ratio of the antioxidant to copper ions is 1%-5%.

10. The method for preparing spherical ultrafine copper powder according to claim 9, characterized in that: The step 5) secondary centrifugation and the step 7) tertiary centrifugation are repeated multiple times.

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