JP6687697B2 - Cuprous oxide particles, cuprous oxide particle slurry, and method for producing cuprous oxide particles - Google Patents

Description

  The present invention relates to cuprous oxide particles, a cuprous oxide particle slurry, and a method for producing cuprous oxide particles, and particularly to a technique for obtaining suitable cuprous oxide particles for use in producing fine copper powder or the like. It is a thing.

  So-called submicron copper powder is a powder composed of fine copper particles having a particle size of 1 μm or less, and is used, for example, as a material for internal / external electrodes of multilayer ceramic capacitors, inductors and other electronic parts, and for ink jet wiring. Is expected.

  This kind of copper powder can be produced from a slurry in which cuprous oxide powder containing cuprous oxide particles is dispersed, by using a chemical reduction method or a disproportionation method.

  As a method for producing copper powder, for example, Patent Document 1 discloses that “a process A to a process F described below is provided, and a chlorine concentration of 0.1 mol is added to 1 mol of copper in a solution in any of the processes A to D. A method for producing copper particles, characterized in that the amount is 05 mol or more Step A: a copper salt-containing solution preparation step of dissolving a copper salt in warm water to obtain a copper salt-containing solution Step B: adding a chelating agent to the copper salt-containing solution Component adjusting step of adding to obtain a component adjusting solution Step C: pH adjusting step of adding a pH adjusting agent to the above component preparing solution to perform pH adjusting operation to obtain a pH adjusting solution Step D: First adding to the pH adjusting solution A first reduction step in which a reducing agent is added to carry out a reducing treatment to produce cuprous oxide particles Step E: Further, a second reducing agent is added to carry out a reducing treatment to convert the cuprous oxide particles into copper particles. Second reduction step Step F: Wash copper particles and dry And it was collected, washed and dried obtaining a copper particle. "Is described as.

  Further, in Patent Document 2, as a method for producing cuprous oxide particles which is a raw material for producing copper powder, "suboxidation by adding an alkaline solution and a reducing agent solution to an aqueous solution containing divalent copper ions is described. In the method for producing cuprous oxide powder for reducing and precipitating copper particles, the alkali solution is an alkali solution containing no carbon and chlorine, and the reducing agent solution is a reducing agent solution containing no carbon or chlorine. A method for producing a cuprous oxide powder, which is characterized by the above.

JP, 2007-169770, A JP, 2010-59001, A

By the way, in order to produce a copper powder from a cuprous oxide powder, whichever method such as a chemical reduction method or a disproportionation method is adopted, in order to realize a uniform reaction from the viewpoint of refining the copper powder, It is necessary to sufficiently disperse the cuprous oxide particles in the slurry containing the copper oxide powder. This is important because the larger the reaction vessel, such as a large-scale production facility for mass-producing copper powder, the more likely the cuprous oxide powder will aggregate or settle.
However, it cannot be said that the dispersibility of the cuprous oxide particles in such a slurry has been sufficiently studied so far.

  This invention is intended to solve such a problem, and its object is cuprous oxide particles, which can effectively improve the dispersibility of cuprous oxide particles in the slurry, suboxide It is intended to provide a copper particle slurry and a method for producing cuprous oxide particles.

  As a result of diligent studies, the inventor has found that a copper sulfate aqueous solution for producing cuprous oxide particles contains a predetermined polymer compound as a modification inhibitor for preventing modification of a copper compound, and by adding an alkali. It has been found that the dispersibility of cuprous oxide particles can be effectively improved by keeping the pH within a predetermined range.

Under these findings, cuprous oxide particles of this invention state, and are zeta potential -10mV less when dispersed in pure water, but average particle diameter measured by SEM image observation is 1μm or less There is .
The cuprous oxide particles of this invention, it is preferable that the carbon deposition amount was measured by a combustion method is 0.1 wt% to 5 wt%.

Cuprous oxide particle slurry of the present invention, the zeta potential is Ri der less -10 mV, the average particle diameter of the cuprous oxide particles after drying was measured by SEM image observation is not more 1μm or less.
The cuprous oxide particle slurry of this invention, when the cuprous oxide particles after drying was measured by a combustion method, it is preferable amount of carbon deposited is 0.1% to 5% by weight.

The method for producing cuprous oxide particles of the present invention is an aqueous copper sulfate solution containing a reducing sugar, a denaturing agent and an alkali, wherein the denaturing agent is selected from the group consisting of polysaccharides, glue and collagen peptides. In order to obtain the above-mentioned copper sulfate aqueous solution, the reducing sugar is added to the aqueous solution in which the copper sulfate is dissolved and the reducing sugar is added, and then the alkali is added. And to maintain the above pH .

Further, in the method for producing cuprous oxide particles according to the present invention, it is preferable that the reducing sugar contains glucose.
And, in the method for producing cuprous oxide particles of the present invention, by adding the modification inhibitor to the copper sulfate aqueous solution, the amount of carbon adhesion derived from the modification agent in the cuprous oxide particles is 0.1 mass. % To 5 mass% is preferable.

In obtaining the copper sulfate aqueous solution, when the copper sulfate is dissolved in the solvent, stirring can be performed at 50 rpm to 1000 rpm.
Moreover, in obtaining the copper sulfate aqueous solution, when the copper sulfate is dissolved in the solvent, heating can be performed so that the liquid temperature is 50 ° C. to 90 ° C.

  According to this invention, the dispersibility of the cuprous oxide particles in the slurry can be effectively improved.

5 is a graph showing the analysis result by XRD of Example 1. 3 is an SEM image of Example 1. 5 is an SEM image of Comparative Example 1.

Hereinafter, embodiments of the present invention will be described in detail.
The cuprous oxide particles of the embodiment of the present invention have a zeta potential of −10 mV or less when dispersed in pure water, and are excellent in dispersibility.

(Zeta potential)
The zeta potential means the potential of the sliding surface when the potential of a region which is sufficiently neutral from the particles and is electrically neutral is zero and the zero point is used as a reference. This sliding surface is a conceptual boundary surface that is supposed to exist between the fixed layer of ions formed around the particle and the diffusion layer of ions outside the fixed layer. Zeta potential is sometimes referred to as electrokinetic potential.

  Since the zeta potential when the cuprous oxide particles are dispersed in pure water is -10 mV or less, the repulsion between the cuprous oxide particles is sufficiently large and the cuprous oxide particles are effectively dispersed in the slurry. You can As a result, if copper powder is produced by a chemical reduction method or a disproportionation method using the cuprous oxide particles, it is possible to obtain copper powder having desired fine copper particles.

With cuprous oxide particles having a zeta potential of greater than −10 mV and close to zero when dispersed in pure water, the cuprous oxide particle slurry is not sufficiently dispersed, and the chemical reduction method or the disproportionation method is used. Therefore, fine copper powder cannot be obtained. On the other hand, if the zeta potential is too small, there is a concern that the reaction may be difficult to proceed by repelling the reducing agent or dilute sulfuric acid.
From this viewpoint, the zeta potential when the cuprous oxide particles are dispersed in pure water is preferably −10 mV to −200 mV, and more preferably −10 mV to −100 mV.

  The above-mentioned zeta potential is measured by adding cuprous oxide particles to pure water, sufficiently dispersing the cuprous oxide particles in pure water to form a slurry, and using a zeta potential measuring device for this slurry. The pure water used in this case may be RO water, that is, water that has been treated with a reverse osmosis membrane. Details of detailed measurement conditions of the zeta potential will be described later in Examples.

(Average particle size)
The cuprous oxide particles preferably have an average particle size measured by SEM image observation of 1 μm or less, and more preferably 0.7 μm or less. If the average particle size of the cuprous oxide particles is small, due to the increase in the specific surface area, the particle size of the copper particles of the copper powder produced using it will also be small, making it easier to obtain fine copper powder. Become. Although there is no particular problem due to the average particle size of the cuprous oxide particles being too small, the average particle size of the cuprous oxide particles is, for example, 0.05 μm or more, typically 0.1 μm or more.

  The average particle size of the cuprous oxide particles is obtained by observing an image taken with a scanning electron microscope (SEM) and by an image analysis method.

(Amount of carbon deposited)
Although carbon may adhere to the cuprous oxide particles, the amount of carbon adhering thereto is preferably 0.1% by mass to 5% by mass. If the amount of carbon adhering to the cuprous oxide particles is less than 0.1% by mass, the alteration may proceed, while if the amount of carbon adhering exceeds 5% by mass, the copper is caused by this. The powder may also contain a relatively large amount of carbon, which may adversely affect the compactness of electrodes such as multilayer ceramic parts. Therefore, the carbon deposition amount of the cuprous oxide particles is more preferably 0.1% by mass to 5% by mass.

The carbon deposition amount of cuprous oxide particles is measured by a combustion method. The combustion method is a method in which oxygen is blown in to burn a certain amount of cuprous oxide particles and the amount of C is calculated from the amount of generated CO and CO ₂ .

(Copper oxide particle slurry)
The cuprous oxide particle slurry is a slurry containing cuprous oxide particles dispersed therein, and has a zeta potential of -10 mV or less. The zeta potential is as described above, and even in this cuprous oxide particle slurry, the preferable range of the zeta potential is −10 mV to −200 mV, and further −10 mV to −100 mV.

  The cuprous oxide particles described above are obtained by drying the cuprous oxide particle slurry. The cuprous oxide particles obtained by drying the cuprous oxide particle slurry have an average particle size measured by SEM image observation of 1 μm or less, more preferably 0.7 μm or less, and 0.05 μm or more, more preferably 0.1 μm or less. It may be 1 μm or more, and the carbon deposition amount of the cuprous oxide particles is preferably 0.1% by mass to 5% by mass as measured by a combustion method.

(Method for producing cuprous oxide particles)
The cuprous oxide particles as described above can be produced, for example, as follows.
In the manufacturing method of this embodiment, an aqueous solution of copper sulfate, which is an aqueous solution of copper sulfate containing a reducing sugar, a denaturing agent and an alkali, is used.

  Here, the type and amount of the denaturing inhibitor and the adjustment of the pH during the production of the cuprous oxide particles may affect the zeta potential when the produced cuprous oxide particles are dispersed in pure water. I got it. Based on this finding, in this embodiment, the denaturing inhibitor contains at least one selected from the group consisting of polysaccharides, glue and collagen peptide, and the pH of the copper sulfate aqueous solution is adjusted to 8 to 11 with alkali. Keep within the range of. This makes it possible to produce cuprous oxide particles having a low zeta potential and excellent dispersibility as described above.

  Explaining the manufacturing method of this embodiment in detail, first, a denaturing inhibitor is added to a solvent such as pure water, and then copper sulfate is added and dissolved to form an aqueous solution. Although copper sulfate may be added to the solvent to dissolve it first, a denaturing inhibitor may be added in advance.

  Here, as described above, the denaturation preventing agent includes at least one selected from the group consisting of polysaccharides, glue and collagen peptides. Among them, examples of the polysaccharides include gum arabic and dextrin.

  The modification inhibitor functions to prevent the cuprous oxide from being modified into copper oxide in the state of the subsequently obtained dry cuprous oxide particles or cuprous oxide particle slurry. If no modifier is used, cuprous oxide will be modified into copper oxide, and the zeta potential of a slurry containing such particles can approach 0 mV. The greater the charge of the denaturing agent in the liquid, the more the zeta potential of the cuprous oxide particles tends to decrease away from zero (that is, the absolute value tends to increase). Then, the charge of the modification inhibitor in the liquid depends on the functional group of the modification agent. Therefore, it is important to select the type of the denaturing agent in consideration of this fact.

  Also, the larger the amount of the denaturing inhibitor in the liquid, the smaller the zeta potential (that is, the larger the absolute value) tends to be. The modification inhibitor can be added to the solvent in an amount of preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass. When a plurality of types of modification inhibitors such as glue and gum arabic are added, this addition amount means the total of them. If the addition amount of the modification inhibitor is too large, the modification agent itself may aggregate, and this aggregate may cause aggregation of the cuprous oxide particles.

  When the copper sulfate is dissolved in the solvent, it can be stirred at preferably 50 rpm to 1000 rpm, more preferably 200 rpm to 1000 rpm, and the liquid temperature is preferably heated to 50 ° C to 90 ° C. can do. Thereby, copper sulfate can be easily dissolved. It should be noted that stirring can be performed at this speed and the liquid temperature can be maintained until the reaction is completed after the alkali addition described below.

Next, reducing sugar and alkali are added to the above aqueous solution, and the pH is maintained within the range of 8 to 11 by dropping the alkali.
The reducing sugar and the alkali may be added in any order, but it is preferable to add the reducing sugar and then the alkali. If the alkali is added first, the copper sulfate becomes an aggregate of copper hydroxide, and even if the reducing sugar is added thereafter, only the surface of the copper hydroxide existing as an aggregate is reduced. In this case, copper hydroxide remains as an impurity and the yield of cuprous oxide decreases. On the other hand, when the reducing sugar is added first, such inconvenience does not occur.

  Here, the reducing sugar may be of any type as long as it can be reduced to cuprous oxide. Examples thereof include reducing sugars such as glucose, fructose, glyceraldehyde, lactose, arabinose and maltose. Although sucrose itself is not a reducing sugar, invert sugar produced by hydrolysis of sucrose can also be used as a reducing sugar.

Examples of the alkali added to adjust the pH include sodium hydroxide, potassium hydroxide, ammonia water, a coupling agent having an amino group at the molecular end, monoethanolamine, diethanolamine, triethanolamine and the like. be able to.
The time for maintaining the pH in the predetermined range can be, for example, 0.1 hour to 10 hours, preferably 0.1 hour to 5 hours.

  The pH of the copper sulfate aqueous solution is maintained within the range of 8 to 11 by the addition of the alkali described above. When the pH of the copper sulfate aqueous solution is less than 8, the zeta potential increases and approaches zero, so that the dispersibility of the cuprous oxide particles is not sufficiently improved. On the other hand, if the pH is higher than 11, reduction may proceed to Cu. From this viewpoint, the pH of the copper sulfate aqueous solution is preferably 8 to 11, and more preferably 8 to 10.

After that, solid-liquid separation by decantation or the like, washing with pure water, and the like are performed to form a cuprous oxide particle slurry, and this is dried to obtain cuprous oxide particles.
In the cuprous oxide particles thus obtained, the amount of carbon adhering to the above-mentioned modification inhibitor is preferably 0.1% by mass to 5% by mass. The carbon derived from the reducing sugar can be confirmed by scooping a cuprous oxide slurry, washing with water on a filter paper, and mass spectrometric analysis of washing water collected by suction filtration. On the other hand, the carbon deposition amount derived from the modification inhibitor can be measured by the combustion method. The cuprous oxide particles obtained by washing with water until the increase in the reducing sugar-derived component in the wash water subsides becomes the target of the carbon deposition amount measurement.

  The cuprous oxide particles described above are dispersed in pure water or the like, and a known chemical reduction method or a disproportionation method is applied to produce a copper powder containing the copper particles. Since such cuprous powder can sufficiently disperse the cuprous oxide particles in the slurry at the time of its preparation, it becomes a fine particle having a small particle size. It is suitable for use as materials and inkjet wiring.

  Next, the present invention was carried out on a trial basis, and its effect was confirmed. However, the description here is merely for the purpose of illustration and is not intended to be limited thereto.

(Example 1)
Pure water (600 mL) and gum arabic (0.9 g) were added to a 5 L beaker and heated so that the liquid temperature in the hot bath was 70 ° C. To this, 349 g of copper sulfate pentahydrate was added, and it was visually confirmed that all the crystals of copper sulfate were dissolved while stirring at 350 rpm. D-glucose 138.5g was added here. A 5 wt% aqueous sodium hydroxide solution was added thereto at a rate of 30 mL / min until a pH of 5 was reached with a liquid feed pump. When the pH reached 5, a sodium hydroxide aqueous solution was added dropwise with a dropper to raise the pH to 8.4. From here, the liquid temperature was maintained at 70 ± 2 ° C. and pH 8.5 ± 0.1 for 3 hours. The pH was adjusted with an aqueous sodium hydroxide solution. After completion of the reaction, decantation, discharge of the supernatant, and washing with pure water were repeated until the pH of the supernatant fell below 8.0.

(Confirm powder composition by XRD)
The solid content of the slurry of Example 1 was scooped and dried in a nitrogen atmosphere at 70 ° C. for 2 hours, and the obtained powder was analyzed by X-ray diffraction (XRD). The result is shown in FIG. This confirmed that it was cuprous oxide.

(Measurement of zeta potential)
The cuprous oxide particle slurry of Example 1 was stirred overnight, diluted 200 times with RO water, sonicated for 3 minutes, and then injected with a micropipette into a Zetasizer ZS measurement cell manufactured by Malvern Panoramic Co., Ltd. When the electric potential was measured, it was −22.6 mV. Here, as the ultrasonic wave irradiation device, US-4R manufactured by As One was used, and the output was set to 180 W and the frequency was set to 40 kHz. The liquid temperature was adjusted to 25 ° C.

(Observation of cuprous oxide particles by SEM)
When the solid content of the slurry of Example 1 was scooped and dried in a nitrogen atmosphere at 70 ° C. for 2 hours, the obtained powder was observed by SEM, and it was confirmed that the average particle size was 1 μm or less. The SEM image is shown in FIG.

(Amount of carbon deposited)
When the solid content of the slurry of Example 1 was scooped and dried in a nitrogen atmosphere at 70 ° C. for 2 hours to measure the carbon deposition amount of the powder by a combustion method, the carbon deposition amount (C deposition amount) was 0. It was 92 mass%.

(Example 2)
The solid content of the slurry of Example 1 is scooped and dried in a nitrogen atmosphere at 70 ° C. for 2 hours, and the powder obtained is made into a slurry having a concentration of 1/300 with RO water, and the slurry is prepared for more than 3 minutes. After sonication, it was injected with a micropipette into a measuring cell of Malvern Panaltical Zetasizer ZS, and the zeta potential was measured and found to be -16.2 mV. As the ultrasonic irradiation device, US-4R manufactured by As One was used, and the output was set to 180 W and the frequency was set to 40 kHz. The liquid temperature was adjusted to 25 ° C.

(Examples 3 and 4)
Cuprous oxide particles were produced in the same procedure as in Example 1 except that the amounts of gum arabic added were 0.1 g and 4 g, respectively, and the zeta potential was measured in the same manner as in Example 1, and the average particle size by SEM was used. The diameter was measured and the carbon deposition amount was evaluated. The settling time of decantation tended to increase as the amount of gum arabic increased.

(Example 5)
Cuprous oxide particles were synthesized by the same procedure as in Example 1 except that an aqueous ammonia solution obtained by diluting 28% aqueous ammonia (reagent) into 1/2 was used in place of the 5 wt% aqueous sodium hydroxide solution. Then, in the same manner as in Example 1, the zeta potential was measured, the average particle size was measured by SEM, and the carbon deposition amount was evaluated.

(Example 6)
Cuprous oxide particles were synthesized by the same procedure as in Example 1 except that beef-derived glue having an average molecular weight of 20,000 was used instead of gum arabic, and zeta potential was measured and SEM was performed in the same manner as in Example 1. The average particle size was measured and the carbon deposition amount was evaluated.

(Example 7)
Instead of gum arabic, cuprous oxide particles were synthesized by the same procedure as in Example 1 except that a collagen peptide derived from pig having an average molecular weight of 3000 was used, and the zeta potential was measured in the same manner as in Example 1. The average particle diameter was measured by SEM and the carbon deposition amount was evaluated.

(Example 8)
Cuprous oxide particles were synthesized by the same procedure as in Example 1 except that the pH was kept at 8 ± 0.1, and the zeta potential was measured in the same manner as in Example 1, the average particle size was measured by SEM, and The carbon deposition amount was evaluated.

(Example 9)
Cuprous oxide particles were synthesized by the same procedure as in Example 1 except that the pH was maintained at 11 ± 0.1, and the zeta potential was measured in the same manner as in Example 1, the average particle size was measured by SEM, and The carbon deposition amount was evaluated.

(Comparative Example 1)
For cuprous oxide particles manufactured by Nisshin Chemco, the zeta potential was measured by the same procedure as in Example 1. When the slurry for measuring zeta potential was allowed to stand for 10 minutes, precipitation of cuprous oxide particles was visually confirmed on the bottom surface of the container only in Comparative Example. In addition, also in this comparative example, the measurement of the average particle diameter by SEM and the carbon deposition amount were similarly evaluated. The SEM image of the comparative example is shown in FIG.

(Comparative example 2)
Cuprous oxide particles were synthesized by the same procedure as in Example 1 except that the pH was kept at 7.5 ± 0.1, the zeta potential was measured in the same manner as in Example 1, and the average particle size by SEM was measured. The measurement and the carbon deposition amount were evaluated.

  Table 1 shows the main conditions and evaluation results of Examples 1 to 9 and Comparative Examples 1 and 2 described above.

As shown in Table 1, in all of Examples 1 to 9, the zeta potential was -10 mV or less and the dispersibility was excellent by using the predetermined denaturant and keeping the pH at the predetermined level. I understand. On the other hand, in Comparative Examples 1 and 2, the zeta potential was larger than −10 mV.
Therefore, according to the present invention, it is suggested that the dispersibility of the cuprous oxide particles in the slurry can be effectively improved.

Claims (9)

Pure water der zeta potential -10mV less when dispersed in is, cuprous oxide particles having an average particle diameter measured by SEM image observation is 1μm or less. The cuprous oxide particles according to claim 1, wherein the carbon deposition amount measured by the combustion method is 0.1% by mass to 5% by mass. Zeta potential Ri der less -10 mV, the average particle diameter of the cuprous oxide particles after drying was measured by SEM image observation is 1μm or less, cuprous oxide particle slurry. The cuprous oxide particle slurry according to claim 3 , wherein the carbon deposition amount is 0.1% by mass to 5% by mass when the dried cuprous oxide particles are measured by a combustion method. In a copper sulfate aqueous solution containing a reducing sugar, a denaturing agent and an alkali,
The denaturation inhibitor, at least one selected from the group consisting of polysaccharides, glue and collagen peptide,
The pH is maintained at 8 to 11 by the alkali,
A method for producing cuprous oxide particles , which comprises adding a reducing sugar to an aqueous solution containing a denaturing inhibitor and dissolving copper sulfate, and then adding an alkali to maintain the pH in obtaining the copper sulfate aqueous solution . The method for producing cuprous oxide particles according to claim 5 , wherein the reducing sugar contains glucose. By including the modified inhibitor in an aqueous copper sulfate solution, the cuprous oxide particles, the carbon deposition amount from the denaturing agents, and 0.1% to 5% by weight, according to claim 5 or 6 Method for producing cuprous oxide particles. Per To obtain the aqueous solution of copper sulfate, when dissolving the solvent copper sulfate, stirred at 50Rpm～1000rpm, the method for manufacturing a cuprous oxide-particles according to any one of claims 5-7. Per To obtain the aqueous solution of copper sulfate, when dissolving copper sulfate the solvent, the liquid temperature is heated so that the 50 ° C. to 90 ° C., cuprous oxide according to any one of claims 5-8 Method for producing particles.