Carboxylic acid-containing nickel powder and method for producing the same

Abstract

This carboxylic acid-containing nickel powder contains a plurality of nickel particles, and comprises carboxylic acid on the surface of each of the nickel particles. Through TG-MS, when the temperature is raised from 38°C to 600°C at a heating rate of 20°C / min under an inert atmosphere, a peak is detected in a mass chromatogram of the carboxylic acid molecular ions, and when the boiling point of the carboxylic acid is represented by Tbp[°C], the peak top of the peak falls within the range of between (Tbp + 100) °C and 600°C inclusive. The carboxylic acid content per 1 m2 surface area of the nickel particles constituting the carboxylic acid-containing nickel powder is between 155 μg and 450 μg inclusive. The present invention allows a carboxylic acid-containing nickel powder to be provided, having high dispersibility in the gas phase, and having high dispersibility in a paste when mixed with an organic solvent, or the like, and used for forming a paste.

Description

[Technical Field]

[0001] The present invention relates to a carboxylic acid-containing nickel powder and a method for producing the carboxylic acid-containing nickel powder. [Background technology]

[0002] Conductive metal powders have traditionally been used as conductive materials in electronic components. In multilayer ceramic capacitors, both ceramic layers and internal electrode layers are rapidly becoming thinner, creating a demand for thin, uniformly thick internal electrode layers. Therefore, conductive metal powders for the internal electrodes of multilayer ceramic capacitors are required to have a narrow particle size distribution, to be free of coarse particles that could contact both adjacent internal electrodes across the dielectric layer and cause short-circuiting, and to be uniformly dispersed in a paste when mixed with an organic solvent or the like.

[0003] To date, methods for producing powders with a desired particle size distribution have involved classifying powders produced by various production methods. For example, one classification method utilizes the difference in particle sedimentation velocity in a gas or liquid phase to classify powders based on their particle size. Classification performed in a gas phase is called dry classification, while classification performed in a liquid phase is called wet classification. While wet classification offers excellent classification accuracy, it requires the use of a liquid as a dispersion medium and requires drying and crushing after classification. Therefore, dry classification is significantly less expensive.

[0004] However, conventional dry classification has had the problem that it is difficult to operate for long periods of time because powder adheres to various parts inside the classifier, causing blockages in the powder supply port and inside the piping, etc., and that the yield is low due to low classification accuracy.

[0005] As a method aimed at solving such problems, Patent Document 1 discloses a method in which a powder is mixed with an auxiliary agent made of an alcohol such as ethanol having a boiling point of less than 200°C, and the powder is dry-classified while the auxiliary agent is vaporized.

[0006] Patent Document 2 discloses a method of mixing powder with an auxiliary agent made of an aqueous alcohol solution containing 10 to 50 mass % of alcohol such as ethanol, and dry classifying the powder while vaporizing the auxiliary agent.

[0007] Patent Document 3 discloses a method of mixing nickel powder with an auxiliary agent made of an organic solvent such as diethylene glycol having a flash point of 80°C or higher, and dry classifying the powder while vaporizing the auxiliary agent. Patent Document 3 also discloses a method of mixing nickel powder with an auxiliary agent made of water, and dry classifying the powder while vaporizing the auxiliary agent.

[0008] Furthermore, Patent Document 4 discloses a method in which powder is mixed with diethylene glycol monomethyl ether, which is a liquid auxiliary agent, and the powder is dry-classified. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2010 / 047175 [Patent Document 2] International Publication No. 2010 / 057206 [Patent Document 3] International Publication No. 2010 / 106716 [Patent Document 4] International Publication No. 2012 / 124453 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the inventors of the present invention have found that, although dry classification, in which an auxiliary agent such as ethanol is adsorbed onto a powder, allows the classifier to operate for a long period of time, the resulting powder contains many coarse particles, and the classification must be repeated many times to reduce the number of coarse particles. Furthermore, although repeated classification can sometimes reduce the number of coarse particles, it takes time and money, which reduces productivity, and furthermore, the yield of the resulting powder is significantly reduced.

[0011] Furthermore, it was sometimes difficult to uniformly disperse the powder obtained as described above in a paste obtained by mixing it with an organic solvent or the like.

[0012] Therefore, an object of the present invention is to provide a carboxylic acid-containing nickel powder that has high dispersibility in the gas phase and, when mixed with an organic solvent or the like and used to form a paste, has high dispersibility in the paste, and a method for producing the same. [Means for solving the problem]

[0013] Such objectives are as follows: (1) 5 This is achieved by the present invention described in (1) A carboxylic acid-containing nickel powder containing a plurality of nickel particles, the nickel particles having carboxylic acids on their surfaces, the carboxylic acid is at least one selected from the group consisting of acetic acid and propionic acid, By TG-MS, a peak was detected in the mass chromatogram of the molecular ion of the carboxylic acid when the temperature was increased from 38°C to 600°C at a rate of 20°C / min under an inert atmosphere, and the boiling point of the carboxylic acid was determined to be T bp [°C], the peak top of the peak is (T bp +100)℃ or higher and 600℃ or lower. The surface area of ​​the nickel particles constituting the carboxylic acid-containing nickel powder is 1 m 2 The carboxylic acid-containing nickel powder has a content of the carboxylic acid of 155 μg or more and 450 μg or less per unit weight.

[0014] (2) TG-MS revealed that when the temperature was increased from 38°C to 600°C at a rate of 20°C / min under an inert atmosphere, (T bp -50)℃ or higher (T bp The carboxylic acid-containing nickel powder according to (1) above, wherein the peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid does not exist within a range of +50°C or less.

[0019] ( 3 ) (1) above or (2) A method for producing the carboxylic acid-containing nickel powder according to claim 1, A method for producing a carboxylic acid-containing nickel powder, comprising a step of contacting a gaseous carboxylic acid with nickel powder dispersed in a gas phase.

[0020] ( 4 ) The nickel powder is dispersed in an atmosphere containing the carboxylic acid in a gaseous state. 3 ) A method for producing a carboxylic acid-containing nickel powder according to the above.

[0021] ( 5 ) The nickel powder, which is dispersed in the gas phase at the time of production, is dispersed in the gas phase, and the carboxylic acid in the gas state is supplied to the gas phase. 3 ) A method for producing a carboxylic acid-containing nickel powder according to the above. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a carboxylic acid-containing nickel powder that has high dispersibility in the gas phase and, when mixed with an organic solvent or the like and used to form a paste, has high dispersibility in the paste, and a method for producing the same. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a classifier used to obtain a fine powder containing an extremely small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Preferred embodiments of the present invention will be described in detail below. [1] Carboxylic acid-containing nickel powder First, the carboxylic acid-containing nickel powder of the present invention will be described.

[0025] The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, and the nickel particles have carboxylic acids on their surfaces. In other words, the carboxylic acid-containing nickel powder of the present invention comprises carboxylic acid-adsorbed nickel particles in which carboxylic acids are adsorbed on the surfaces of nickel particles as mother particles.

[0026] The carboxylic acid-containing nickel powder of the present invention was subjected to TG-MS (thermogravimetry-mass spectrometry) to detect a peak in the mass chromatogram of the molecular ion of the carboxylic acid when heated from 38°C to 600°C at a heating rate of 20°C / min under an inert atmosphere, and the boiling point of the carboxylic acid was determined to be T bp [°C], the peak top of the peak is (T bp +100)°C or more and 600°C or less, and the surface area of ​​the nickel particles is 1 m 2 The content of the carboxylic acid per unit weight is 155 μg or more and 450 μg or less.

[0027] By satisfying these conditions, it is possible to provide a carboxylic acid-containing nickel powder that has high dispersibility in a gas phase and that, when mixed with an organic solvent or the like and used to form a paste, has high dispersibility in the paste. Furthermore, because the carboxylic acid-containing nickel powder has such excellent dispersibility in a gas phase, coarse particles can be suitably removed by dry classification, and, for example, a fine powder with a sharp particle size distribution can be suitably obtained by dry classification with an excellent yield. Furthermore, because the carboxylic acid-containing nickel powder has excellent dispersibility in a paste containing the carboxylic acid-containing nickel powder, the smoothness of a coating film formed using the paste can be excellent.

[0028] The peak top value of the peak in the mass chromatogram of the carboxylic acid molecular ion detected by TG-MS can be adjusted, for example, by the form of adsorption of the carboxylic acid onto nickel particles. More specifically, the peak top value of the peak in the mass chromatogram of the carboxylic acid molecular ion detected by TG-MS can be suitably adjusted by adjusting, for example, the method of adsorption of the carboxylic acid onto nickel particles, the conditions of the adsorption treatment, the amount of adsorption, etc.

[0029] In this specification, the term "coarse particles" refers to particles having a cumulative 50% particle diameter (D) based on the volume of the target powder, for example, the powder obtained by the above-mentioned classification. 50 ) refers to particles with a particle size that is large enough to 50 For example, the particle size can be 1.5 times or more than the D of the target powder. 50 For example, the particle size can be 2.0 times or more of the D of the target powder. 50 The particles can be 2.5 times larger than the original size.

[0030] In this specification, the volume-based cumulative 50% particle diameter (D 50) refers to the 50% volume-based cumulative fraction of particle size distribution measured using a laser particle size distribution analyzer, unless otherwise specified, and can be determined, for example, by measurement using a laser diffraction / scattering particle size distribution analyzer LA-960 (manufactured by HORIBA Corporation).

[0031] In addition, for the TG-MS, for example, a STA2500 Regulus manufactured by NETZSCH can be used as a TG-DTA for heating the sample, and a JMS-Q1500GC manufactured by JEOL Ltd. can be used as an MS for mass spectrometry of substances vaporized by heating the sample.

[0032] In addition, the surface area of ​​the nickel particles that make up the carboxylic acid-containing nickel powder is 1 m 2 The carboxylic acid content per unit weight can be determined by measurement using a CS (carbon-sulfur) analyzer (for example, EMIA-320V manufactured by HORIBA Corporation).

[0033] As described above, in the carboxylate-containing nickel powder of the present invention, in the mass chromatogram of the molecular ion of the carboxylic acid, a predetermined region (T bp A peak appears in the range of temperatures above +100°C (range of 100°C or higher and 600°C or lower). This is thought to be due to the adsorption of carboxylic acid to the nickel particles in a specific form. Although the detailed mechanism is unknown, the inventors speculate that, for example, because carboxylic acid is chemically adsorbed to the nickel particles, it is more strongly adsorbed than when it is physically adsorbed, and therefore, a peak appears in the high-temperature region of 100°C (the boiling point of carboxylic acid) or higher. It is thought that the adsorption of carboxylic acid to the nickel particles in this specific form and in an appropriate ratio on the surface of the nickel particles results in the above-mentioned excellent effects, namely, improved dispersibility in the gas phase and improved dispersibility in the paste when mixed with an organic solvent or the like and used to form a paste.

[0034] In addition, the surface area of ​​a nickel particle is 1 m 2When the content of the carboxylic acid per 1000g is equal to or greater than the lower limit, the dispersibility of the carboxylic acid-containing nickel powder in the gas phase can be made sufficiently excellent.

[0035] In addition, the surface area of ​​a nickel particle is 1 m 2 When the carboxylic acid content per 1000g is equal to or less than the upper limit, the dispersibility of the carboxylic acid-containing nickel powder in the paste can be made sufficiently excellent when the powder is mixed with an organic solvent or the like and used to form a paste.

[0036] In this specification, unless otherwise specified, the term "boiling point" refers to the boiling point under 1 atmospheric pressure, that is, the standard boiling point.

[0037] Furthermore, when the carboxylic acid-containing nickel powder contains multiple types of carboxylic acids, it is sufficient that at least one of the carboxylic acids satisfies the above-mentioned conditions, but it is particularly preferable that the carboxylic acid with the highest content among the multiple types of carboxylic acids satisfies the above-mentioned conditions, and it is even more preferable that all types of carboxylic acids contained in the carboxylic acid-containing nickel powder satisfy the above-mentioned conditions.

[0038] As described above, in the carboxylic acid-containing nickel powder of the present invention, the peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid detected by the above-mentioned TG-MS analysis is (T bp +100)℃ or higher and 600℃ or lower, but (T bp It is preferable that the temperature of the crystal is in the range of (Tb+120)°C or more and 580°C or less, and more preferable that the temperature of the crystal is in the range of (Tb+150)°C or more and 560°C or less, and it is ... more preferable that the temperature of the crystal is in the range of (T bp It is more preferable that the temperature is in the range of (T bp It is most preferable that the temperature is in the range of +230°C to 520°C. This makes the above-mentioned effects more pronounced.

[0039] In addition, in the carboxylic acid-containing nickel powder of the present invention, the surface area of ​​the nickel particles is 2 The content of carboxylic acid per unit area is sufficient as long as it is 155 μg or more and 450 μg or less, but is preferably 155 μg or more and 400 μg or less, more preferably 155 μg or more and 380 μg or less, and even more preferably 155 μg or more and 350 μg or less. 2 The carboxylic acid content per unit mass is preferably 160 μg or more and 350 μg or less, more preferably 170 μg or more and 350 μg or less, and even more preferably 250 μg or more and 350 μg or less. This makes the above-mentioned effects more pronounced.

[0040] When the carboxylic acid-containing nickel powder of the present invention is analyzed by TG-MS as described above, (T bp It is sufficient that the peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid is within the range of (T +100) ° C or more and 600 ° C or less, and the peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid may also be outside the above range. bp -50)℃ or higher (T bp It is preferable that the peak top of the peak in the mass chromatogram of the carboxylic acid molecular ion does not exist within the range of +50°C or less.

[0041] This can improve the dispersibility of the carboxylic acid-containing nickel powder in the gas phase. When the carboxylic acid-containing nickel powder contains multiple types of carboxylic acids, it is preferable that at least one type of carboxylic acid satisfies the above-mentioned conditions, and it is particularly preferable that the carboxylic acid with the highest content among the multiple types of carboxylic acids satisfies the above-mentioned conditions, and it is even more preferable that all types of carboxylic acids contained in the carboxylic acid-containing nickel powder satisfy the above-mentioned conditions.

[0042] Cumulative 50% particle size D of nickel powder containing carboxylic acid 50is preferably more than 0.01 μm and not more than 10 μm, more preferably more than 0.03 μm and not more than 2.5 μm, even more preferably more than 0.05 μm and not more than 1.2 μm, and most preferably more than 0.10 μm and not more than 0.80 μm.

[0043] [1-1] Nickel particles The nickel particles are the main component of the carboxylic acid-containing nickel powder and are mainly composed of nickel.

[0044] The nickel particles may be any particles as long as they are mainly composed of nickel, and may be, for example, composed of nickel as a simple metal or may be composed of a nickel alloy. The nickel particles may contain nickel as the component with the highest content, but the content of components other than nickel in the nickel particles is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. Of these, the content of components other than nickel in the nickel particles is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. In particular, it is preferable that components other than nickel in the nickel particles are only those that are unavoidably contained, and the content of components other than nickel in the nickel particles is preferably 1000 ppm or less.

[0045] The shape of the nickel particles is not particularly limited, and examples thereof include various shapes such as spherical, flake, and granular shapes, and one or more types selected from these may be used in combination.

[0046] In this specification, the term "spherical" refers to a particle shape in which the ratio of major axis to minor axis is 2 or less, and the term "flaky" refers to a shape in which the ratio of major axis to minor axis is more than 2.

[0047] The method for producing nickel particles is not particularly limited, but examples thereof include electrolysis, atomization, mechanical pulverization, wet reduction, spray pyrolysis, chemical vapor deposition, and physical vapor deposition.

[0048] [1-2]Carboxylic Acid The carboxylic acid-containing nickel powder contains a carboxylic acid in addition to the above-mentioned nickel particles.

[0049] Most of the carboxylic acid contained in the carboxylic acid-containing nickel powder is adsorbed onto the surface of the nickel particles as the base particles, in other words, most of the carboxylic acid contained in the carboxylic acid-containing nickel powder is contained as a constituent of the carboxylic acid-adsorbed nickel particles.

[0050] The adsorption of carboxylic acid onto nickel particles can be either physical adsorption or chemical adsorption.

[0051] The carboxylic acid is not particularly limited as long as it is a compound having a carboxyl group.

[0052] The carboxylic acid preferably has a boiling point of 100°C or higher and 270°C or lower, more preferably 105°C or higher and 250°C or lower, even more preferably 110°C or higher and 200°C or lower, and most preferably 115°C or higher and 170°C or lower.

[0053] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder in a gas phase, and the dispersibility of the carboxylic acid-containing nickel powder in a paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like and used to form a paste. Furthermore, during the production of the carboxylic acid-containing nickel powder, the carboxylic acid as a raw material can be handled suitably in a liquid state, improving handleability, and when the carboxylic acid is adsorbed onto the nickel powder in a vaporized state, the carboxylic acid can be adsorbed onto the nickel powder in a more suitable state.

[0054] The carboxylic acid is preferably a monocarboxylic acid. This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder in the gas phase, and the dispersibility of the carboxylic acid-containing nickel powder in the paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like and used to form a paste.

[0055] The molecular weight of the carboxylic acid is preferably 40 or more and 160 or less, more preferably 50 or more and 120 or less, and even more preferably 55 or more and 100 or less.

[0056] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder in the gas phase, and the dispersibility of the carboxylic acid-containing nickel powder in the paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like and used to form a paste.

[0057] The carboxylic acid preferably has 2 or more and 9 or less carbon atoms, more preferably 2 or more and 7 or less carbon atoms, and even more preferably 2 or more and 5 or less carbon atoms.

[0058] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder in the gas phase, and the dispersibility of the carboxylic acid-containing nickel powder in the paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like and used to form a paste.

[0059] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, isobutyric acid, butyric acid, crotonic acid, isovaleric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, lactic acid, oxalic acid, succinic acid, oleic acid, acrylic acid, and methacrylic acid. One or a combination of two or more selected from these may be used, but at least one selected from the group consisting of acetic acid and propionic acid is preferred, and acetic acid is more preferred.

[0060] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder in the gas phase, and the dispersibility of the carboxylic acid-containing nickel powder in the paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like and used to form a paste.

[0061] [1-3] Uses of carboxylic acid-containing nickel powder The use of the carboxylic acid-containing nickel powder of the present invention is not particularly limited, but it can be used as a conductive powder, and is particularly preferably used as a conductive powder for conductive paste. Because of its high dispersibility as a powder, its dispersibility in a paste is also likely to be high. Furthermore, the carboxylic acid-containing nickel powder of the present invention is particularly preferably used as a conductive powder after being subjected to a classification process, such as that described below, particularly a dry classification process, and is more preferably used as a conductive powder for a conductive paste. Furthermore, the carboxylic acid-containing nickel powder of the present invention has high fluidity and excellent handleability, making it easy to handle when used for various applications.

[0062] By subjecting the carboxylic acid-containing nickel powder of the present invention to a dry classification process as described below, it is possible to obtain a fine powder having a small average particle size, a narrow particle size distribution, and almost no coarse particles. Because such a fine powder has a narrower particle size distribution than the carboxylic acid-containing nickel powder of the present invention before classification, it is possible to form a coating film with superior smoothness. When the fine powder is used for an internal electrode, it is possible to form an electrode layer with a uniform thickness. Furthermore, because it contains almost no coarse particles, it is possible to effectively prevent conductive powder particles from contacting both internal electrodes and causing short circuits. Therefore, even in applications requiring particularly high reliability, it is possible to obtain a fully satisfactory effect. Therefore, when the fine powder is used to form internal conductors (internal electrodes) or terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, and multilayer piezoelectric actuators, the above-mentioned effects are even more pronounced.

[0063] The conductive powder may be mixed with, for example, glass frit and an organic vehicle to form a conductive paste, which may be used to form conductive portions of electronic components.

[0064] [2] Manufacturing method for carboxylic acid-containing nickel powder Next, a method for producing the carboxylic acid-containing nickel powder of the present invention will be described.

[0065] The method for producing a carboxylic acid-containing nickel powder of the present invention is a method for producing the carboxylic acid-containing nickel powder of the present invention described above, and includes a step of contacting a gaseous carboxylic acid with nickel powder, which is an aggregate of multiple nickel particles dispersed in a gas phase.

[0066] This makes it possible to provide a method for producing a carboxylic acid-containing nickel powder that has high dispersibility in a gas phase and that has high dispersibility in a paste when mixed with an organic solvent or the like and used to form a paste, as described above. Furthermore, compared to contacting nickel powder in a stationary state with a carboxylic acid in a gaseous state, the concentration of the carboxylic acid is low and the carboxylic acid can be adsorbed onto the surfaces of the nickel particles in an extremely short time, which is advantageous in terms of carboxylic acid consumption and time reduction.

[0067] The method for producing a carboxylic acid-containing nickel powder of the present invention may include a step of contacting nickel powder dispersed in a gas phase with a gaseous carboxylic acid. For example, it is preferable to disperse nickel powder, which is an aggregate of multiple nickel particles, in an atmosphere containing gaseous carboxylic acid.

[0068] In addition, in the method for producing a carboxylic acid-containing nickel powder of the present invention, a step of contacting the nickel powder with the gaseous carboxylic acid may be carried out by supplying the gaseous carboxylic acid into the gas phase while the nickel powder is dispersed in the gas phase at the time of production.

[0069] In this way, by generating nickel powder in the gas phase and then feeding carboxylic acid gas before recovering the nickel powder, the carboxylic acid gas can be brought into contact with nickel powder in a better dispersed state, thereby allowing the carboxylic acid to be adsorbed more uniformly.

[0070] Examples of methods for producing the nickel powder that is dispersed in a gas phase during production include gas phase methods such as chemical vapor deposition and physical vapor deposition, atomization, spray pyrolysis, etc. In particular, by producing the nickel powder using a gas phase method or spray pyrolysis, the particle size of the nickel powder can be more easily adjusted to meet preferred conditions.

[0071] In addition, the method for producing a carboxylic acid-containing nickel powder of the present invention only needs to include a step of contacting a gaseous carboxylic acid with nickel powder dispersed in a gas phase, and is not limited to a method in which a gaseous carboxylic acid is contacted with nickel powder immediately after production.For example, a gaseous carboxylic acid may be contacted with nickel powder that has been recovered once.

[0072] [3] A method for producing a fine powder using the carboxylic acid-containing nickel powder of the present invention Next, a method for producing a fine powder using the carboxylic acid-containing nickel powder of the present invention will be described.

[0073] The method for producing the fine powder according to this embodiment is to obtain a volume-based cumulative 50% particle diameter D 50 A method for producing a fine powder having a particle size in the range of 0.01 μm to 5.0 μm, 50 The method includes a powder-to-be-classified production step of dispersing carboxylic acid-containing nickel powder having a size of more than 0.01 μm and not more than 10 μm in a gas phase to obtain a powder-to-be-classified, and a dry classification step of dry-classifying the powder-to-be-classified.

[0074] This results in an extremely small number of coarse particles, with a cumulative 50% particle diameter (D) based on volume. 50 It is possible to provide a method for producing fine powder that can produce fine powder having a particle size in the range of 0.01 μm to 5.0 μm with high productivity.

[0075] The reason for such excellent results is believed to be as follows. Compared to dry classification in which an auxiliary agent such as ethanol is adsorbed onto the powder, the use of carboxylic acid-containing nickel powder in which carboxylic acid is adsorbed onto nickel particles under specified conditions improves the dispersibility of the powder in the gas phase and increases classification accuracy. Therefore, the number of coarse particles contained in the produced fine powder can be significantly reduced. This also reduces the number of classifications, improving productivity.

[0076] Furthermore, when the fine powder obtained as described above is mixed with an organic solvent or the like and used to form a paste, it has particularly excellent dispersibility in the paste, and therefore the coating film formed using the paste can have excellent smoothness.

[0077] Furthermore, by using the carboxylic acid-containing nickel powder of the present invention, the fluidity of the powder is increased, the adhesion of the powder to the inside of the classifier is reduced, and the yield is improved. Furthermore, since the adhesion to the inside of the classifier is reduced, the powder supply port of the classifier and the inside of the piping are less likely to be clogged, so the operating time of the classifier can be extended and productivity is improved.

[0078] In addition, in this embodiment, a carboxylic acid-containing nickel powder in which a carboxylic acid has been adsorbed onto nickel particles under predetermined conditions is used, which is advantageous in simplifying and miniaturizing the configuration of the device used to produce the fine powder. Furthermore, since a carboxylic acid-containing nickel powder in which a carboxylic acid has been adsorbed onto nickel particles under predetermined conditions is used, the powder has higher fluidity than when nickel powder without carboxylic acid is placed in a disperser, and adhesion within the disperser is less likely to occur, resulting in smoother movement of the powder within the disperser.

[0079] In this specification, classification refers to the operation of dividing powder into a group of relatively large particles (in other words, coarse powder) and a group of relatively small particles (in other words, fine powder) according to their size. Specifically, in this specification, fine powder refers to a group of particles having a cumulative 50% particle diameter D50 refers to a group of particles with a diameter of 0.01 μm or more and 5.0 μm or less, and coarse particles are 50 refers to a group of particles that are larger than fine powder.

[0080] [3-1] Classifier FIG. 1 is a diagram showing an example of the configuration of a classifier used to obtain a fine powder containing an extremely small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention. In the following description, the upper side in FIG. 1 will be referred to as "top" and the lower side as "bottom."

[0081] The classifier 1 is an air current type classifier that performs classification by utilizing centrifugal force acting on powder, and includes a casing 3 that forms a classification chamber 10.

[0082] A dispersion zone 11 for dispersing the carboxylic acid-containing nickel powder prior to classification is provided upstream of the classification chamber (classification zone) 10. The classification chamber 10 is a region for classifying the dispersed carboxylic acid-containing nickel powder.

[0083] The classifier 1 also has an inlet 4 for introducing carboxylic acid-containing nickel powder into the dispersion zone 11, an air nozzle 5 for injecting high-pressure air (primary air) into the dispersion zone 11, a guide vane 6 for injecting secondary air into the classification chamber 10 to form a swirling airflow within the classification chamber 10, a fine powder discharge outlet 7 opening at the top center of the classification chamber 10, and a coarse powder discharge outlet 8 opening along the bottom outer periphery of the classification chamber 10.

[0084] Next, a method for dispersing and classifying a carboxylic acid-containing nickel powder using such a classifier 1 will be described.

[0085] The carboxylic acid-containing nickel powder is introduced into the dispersion zone 11 from the inlet 4. The carboxylic acid-containing nickel powder is given a dispersing force by the primary air injected into the dispersion zone 11, and is dispersed. The carboxylic acid-containing nickel powder is then introduced into the classification chamber 10 in a dispersed state.

[0086] In the classification chamber 10, secondary air is introduced into the classification chamber 10 from the guide vane 6, causing the airflow to swirl in the classification chamber 10 and be exhausted from the upper center of the classification chamber 10. The carboxylate-containing nickel powder in the solid-gas mixture fluid is separated into coarse powder and fine powder by the outward centrifugal force acting due to the swirling airflow and the gas flow moving toward the center.

[0087] That is, the coarse particles move radially outward within the classification chamber 10 due to the outward centrifugal force caused by the swirling airflow, and are collected from the coarse particle outlet 8 on the lower outer periphery of the classification chamber 10. On the other hand, the fine particles move radially inward within the classification chamber 10 due to the gas flow moving toward the center, and are collected from the fine particle outlet 7 in the upper center of the classification chamber 10.

[0088] A suction pump (not shown) is connected to the fine powder discharge port 7, and the fine powder is discharged and collected together with the air (exhaust air) in the classification chamber 10.

[0089] The powder to be classified production step corresponds to the step carried out in the dispersion zone 11, and the dry classification step corresponds to the step carried out in the classification chamber (classification zone) 10. That is, the carboxylic acid-containing nickel powder dispersed in the dispersion zone 11, in other words, the carboxylic acid-containing nickel powder introduced into the classification chamber 10, is the powder to be classified as referred to in this specification.

[0090] In the above description, an air classifier that performs classification by utilizing centrifugal force caused by a swirling air current has been used as an example, but the classification method of the classifier is not particularly limited. For example, it may be a method that performs classification by utilizing centrifugal force caused by the rotation of a rotor, a method that performs classification by utilizing gravity, or a method that performs classification by utilizing inertial force.

[0091] In the present invention, the step of producing a powder to be classified and the step of dry classification are not limited to being performed using the same apparatus, and may be performed using separate apparatuses. That is, the carboxylic acid-containing nickel powder may be dispersed in a disperser to obtain a powder to be classified, and then the powder to be classified may be classified in a dry classifier.

[0092] [3-2] Classified powder generation process In the powder to be classified producing step, the powder to be classified is obtained by dispersing the carboxylic acid-containing nickel powder in a gas phase.

[0093] The supply rate of the carboxylic acid-containing nickel powder to the classifier, i.e., for example, in the classifier 1 shown in FIG. 1, the supply rate of the carboxylic acid-containing nickel powder from the inlet 4 to the dispersion zone 11 depends on the size (capacity) of the classifier, but is preferably 1 kg / hour or more and 20 kg / hour or less, more preferably 3 kg / hour or more and 15 kg / hour or less, and even more preferably 5 kg / hour or more and 12 kg / hour or less.

[0094] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder and also improve the productivity of the fine powder.

[0095] The supply dispersion pressure during dispersion, i.e., for example, the pressure of the dispersion air sprayed from the air nozzle 5 into the dispersion zone 11 in the classifier 1 shown in FIG. 1, is not particularly limited, but is preferably 0.2 MPa or more and 1.0 MPa or less, more preferably 0.4 MPa or more and 0.8 MPa or less, and even more preferably 0.5 MPa or more and 0.7 MPa or less.

[0096] This makes it possible to improve the dispersibility of the carboxylic acid-containing nickel powder and also improve the productivity of the fine powder.

[0097] [3-2]Dry classification process In the dry classification step, the powder to be classified obtained in the powder to be classified production step is dry classified.

[0098] Since the powder to be classified is suitably dispersed in the gas phase, the classification accuracy in the dry classification process is improved. As a result, the number of coarse particles contained in the produced fine powder can be reduced significantly. Furthermore, the improved classification accuracy allows the number of classifications to be reduced, thereby improving productivity.

[0099] Furthermore, the increased fluidity of the powder to be classified reduces adhesion of the powder to the inside of the classifier, improving yield. Furthermore, the reduced adhesion to the inside of the classifier reduces clogging of the powder supply port and the inside of the piping of the classifier, extending the operating time of the classifier and improving productivity.

[0100] This allows for the production of fine powder with an extremely small number of coarse particles with high productivity.

[0101] The gas phase temperature at which the dry classification step is carried out is not particularly limited, but is preferably 60°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 150°C or higher and 200°C or lower.

[0102] This effectively prevents problems such as particle deformation due to heat and deterioration of the particle's constituent materials, while increasing the airflow speed to increase centrifugal force and prevent water vapor from adhering to the particles, further improving classification accuracy. It also further improves productivity. It also significantly reduces the number of coarse particles in the fine powder.

[0103] The suction air volume during the dry classification step, i.e., for example, in the classifier 1 shown in FIG. 1, the suction air volume by the suction pump connected to the fine powder outlet 7 is not particularly limited, but is preferably 5.0 m 3 / min more than 30m 3 / min or less is preferable, and 6.0m 3 / min or more 20m 3 / min or less is more preferable, and 7.0m 3 / min or more 9.0m 3 More preferably, it is equal to or less than 1 / min. This allows the powder to be classified more efficiently.

[0104] The suction pressure used for dry classification, i.e., for example, the suction pressure applied by the suction pump connected to the fine powder outlet 7 in the classifier 1 shown in FIG. 1, is not particularly limited, but is preferably −60 kPa or more and −5 kPa or less, more preferably −50 kPa or more and −10 kPa or less, and even more preferably −40 kPa or more and −15 kPa or less. This allows the powder to be classified more suitably.

[0105] By dry classifying the powder to be classified, the powder to be classified is classified into fine powder and coarse powder. The powder to be classified has a cumulative 50% particle diameter D 50 Fine particles with a diameter of 0.01 μm or more and 5.0 μm or less, and fine particles with a diameter of D 50 The fine powder is recovered as the above-mentioned fine powder.

[0106] In this way, the cumulative 50% particle diameter D 50 A fine powder having a particle size in the range of 0.01 μm to 5.0 μm is produced.

[0107] The fine powder produced in this manner contains an extremely small number of coarse particles, and secondary aggregation is prevented by the carboxylic acid being adsorbed to the fine powder in a suitable state.

[0108] Furthermore, according to the above-described method, the accuracy of classification is improved, so the number of classifications can be reduced. Also, adhesion of the powder to be classified to the inside of the classifier is reduced, which improves yield. Furthermore, the reduction in adhesion to the inside of the classifier makes it less likely that the powder supply port of the classifier or the inside of the piping will become clogged, which extends the operating time of the classifier and improves productivity.

[0109] The dry classification step may be carried out only once, or may be repeated multiple times, thereby further improving classification accuracy.

[0110] The yield of fine powder in the dry classification step is not particularly limited, but is preferably 80% or more, more preferably 81% or more, even more preferably 82% or more, and most preferably 83% or more. This makes the effect of the present invention even more pronounced.

[0111] In this specification, the yield of the fine powder in the dry classification step is calculated from the weight of the powder before classification, i.e., the weight of the carboxylic acid-containing nickel powder, and the weight of the powder after classification, i.e., the weight of the fine powder, using the following formula: Yield (%) = (weight of powder after classification / weight of powder before classification) × 100 This is the value calculated by

[0112] The fine powder produced by the method of the present invention has a volume-based cumulative 50% particle diameter D 50 The particle size should be within the range of 0.01 μm to 5.0 μm, but the D 50 is preferably 0.03 μm or more and 2.0 μm or less, more preferably 0.05 μm or more and 1.0 μm or less, and even more preferably 0.10 μm or more and 0.60 μm or less.

[0113] This allows for the production of fine powder with a more ideal particle size distribution. 50 When D is within this range, coarse particles tend to become a problem, and the adverse effects of coarse particles tend to occur particularly easily. 50 Even if the value of D is within this range, the occurrence of the above problems can be more effectively prevented. 50 When the value is within the above range, the effect of the present invention is more pronounced.

[0114] The fine powder produced by the method of the present invention described above has a particle size distribution measured using a laser particle size distribution analyzer, and the volume-based cumulative fraction at 10% is D 10 [μm], and the cumulative fraction of 50% is D 50[μm], and the cumulative fraction of 90% is D 90 [μm] (D 90 -D 10 ) / D 50 The value of is preferably 0.30 or more and 0.90 or less, more preferably 0.35 or more and 0.80 or less, and even more preferably 0.40 or more and 0.75 or less.

[0115] (D 90 -D 10 ) / D 50 is an index that represents the uniformity of particle size distribution, and (D 90 -D 10 ) / D 50 The smaller the value, the narrower the particle size distribution, i.e., the more uniform the particle size.

[0116] This makes the fine powder have a more uniform particle size, making it suitable for use in a variety of applications.

[0117] In the method for producing fine powder, the number of coarse particles determined by the following measurement is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less.

[0118] This makes it possible to more effectively prevent various problems caused by the inclusion of coarse particles in the fine powder.

[0119] The number of coarse particles can be measured, for example, as follows. First, 1.0 g of fine powder is mixed with 20 mL of ethanol, and then treated for 1 minute using an ultrasonic cleaner (e.g., Honda Electronics Co., Ltd., W-113) to prepare a dispersion. 30 μL of the dispersion thus prepared is weighed out, dropped onto an aluminum sample stage, and dried to remove the dispersion medium, thereby preparing a measurement sample. This measurement sample is observed at 10,000x magnification in 50 fields of view using a scanning electron microscope (e.g., Hitachi High-Technologies Corporation, SU-1510). The volume-based cumulative 50% particle diameter D of the fine powder is 50The total number of particles having a particle size 1.5 times or more of the above is calculated, and this number is taken as the number of coarse particles.

[0120] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0121] For example, the apparatuses applicable to the method for producing fine powder are not limited to those described in the above-mentioned embodiments. [Example]

[0122] The present invention will be explained in more detail below with reference to specific examples, but the present invention is not limited to these examples. In the following explanation, treatments for which no particular temperature or humidity conditions are specified were carried out at room temperature (25°C) and a relative humidity of 50%. Furthermore, for various measurement conditions, values ​​for which no particular temperature or humidity conditions are specified are those at room temperature (25°C) and a relative humidity of 50%. Furthermore, the cumulative volume fraction (10%) values ​​D for carboxylic acid-containing nickel powder and fine powder are 10 , 50% cumulative value D 50 , 90% cumulative value D 90 was determined by measurement using a laser diffraction / scattering particle size distribution analyzer LA-960 (manufactured by HORIBA Corporation). The conditions for the carboxylic acids used in each of the examples described below are summarized in Table 1.

[0123] [Table 1]

[0124] [4] Production of carboxylic acid-containing nickel powder Example 1 First, the cumulative 50% particle diameter D 50 Nickel powder with a particle size of 0.31 μm was prepared. This nickel powder was dispersed for 10 seconds in an atmosphere containing acetic acid as a carboxylic acid to obtain a carboxylic acid-containing nickel powder, which is an acetic acid-adsorbed nickel powder. The acetic acid used was nearly 100% pure (Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7%+). The temperature of the acetic acid-containing atmosphere when dispersing the nickel powder was adjusted to 100°C. The partial pressure of acetic acid in the atmosphere was 6.6 x 10 -5 It was ATM.

[0125] Example 2 When nickel powder is dispersed in an atmosphere containing acetic acid as a carboxylic acid, the partial pressure of acetic acid in the atmosphere is set to 6.6 × 10 -6 A carboxylic acid-containing nickel powder, which is an acetic acid-adsorbed nickel powder, was obtained in the same manner as in Example 1, except that the temperature was changed to 1000 K atm.

[0126] Example 3 Carboxylic acid-containing nickel powder was obtained in the same manner as in Example 1, except that propionic acid was used instead of acetic acid as the carboxylic acid and the conditions for dispersing in an atmosphere containing carboxylic acid were changed as shown in Table 2.

[0127] Example 4 First, nickel acetate tetrahydrate powder was prepared. This nickel acetate tetrahydrate powder was sprayed and heated to 1500°C in the gas phase, obtaining nickel powder dispersed in the gas phase. With this nickel powder dispersed in the gas phase, the temperature of the gas phase was adjusted to 300°C. Acetic acid as a carboxylic acid was supplied to the gas phase in which this nickel powder was dispersed, and treatment was carried out for 10 seconds, obtaining a carboxylic acid-containing nickel powder, which is an acetate-adsorbed nickel powder. The acetic acid used was nearly 100% pure (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7%+). Furthermore, the partial pressure of acetic acid in the gas phase during treatment with acetic acid as the carboxylic acid was 6.6 x 10 -5 The cumulative 50% particle diameter D on a volume basis was measured by recovering nickel powder before supplying acetic acid as a carboxylic acid. 50 was 0.31 μm.

[0128] Example 5 The temperature of the gas phase when supplying carboxylic acid was changed to 500°C, and the partial pressure of acetic acid in the gas phase when treating with acetic acid as the carboxylic acid was changed to 1.3 × 10 -5 A carboxylic acid-containing nickel powder, which is an acetic acid-adsorbed nickel powder, was obtained in the same manner as in Example 4, except that the temperature was changed to 1000 K atm.

[0129] Example 6 When treating with acetic acid as the carboxylic acid, the partial pressure of acetic acid in the gas phase is 6.6 × 10 -5 A carboxylic acid-containing nickel powder, which is an acetic acid-adsorbed nickel powder, was obtained in the same manner as in Example 5, except that the temperature was changed to 1000 psi atm.

[0130] (Comparative Example 1) The powder of this comparative example was the nickel powder used as the raw material powder in Example 1 without being treated with carboxylic acid. In other words, the powder of this comparative example is nickel powder that has not been treated with carboxylic acid.

[0131] (Comparative Example 2) First, the cumulative 50% particle diameter D 50 Nickel powder with a particle size of 0.31 μm was prepared. This nickel powder was dispersed in an atmosphere containing ethanol as alcohol for 10 seconds to obtain alcohol-adsorbed nickel powder as an alcohol-treated powder. The temperature of the alcohol-containing atmosphere during dispersion of the nickel powder was adjusted to 25°C. The partial pressure of alcohol in the atmosphere was 9.6 x 10 -6 It was ATM.

[0132] (Comparative Example 3) When isopropanol is used instead of ethanol as the alcohol, the partial pressure of alcohol in the atmosphere during the alcohol treatment is 8.8 × 10 -6 An alcohol-treated powder, which was a powder treated with an organic compound, was produced in the same manner as in Comparative Example 2, except that the temperature was adjusted to 1000 kJ / cm 2 atm.

[0133] Comparative Example 4 First, the cumulative 50% particle diameter D 50 Nickel powder with a particle size of 0.31 μm was prepared. This nickel powder was left standing in an atmosphere containing acetic acid as a carboxylic acid to obtain carboxylic acid-containing nickel powder, which is acetic acid-adsorbed nickel powder. The acetic acid used was nearly 100% pure (Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7%+). The treatment time with acetic acid was 30 minutes, the treatment temperature was 50°C, and the partial pressure of acetic acid in the atmosphere during the treatment with acetic acid was 1.0 x 10 -1 It was ATM.

[0134] (Comparative Examples 5 and 6) Carboxylic acid-containing nickel powder, which is an acetic acid-adsorbed nickel powder, was obtained in the same manner as in Example 1, except that the conditions for dispersing the nickel powder in an atmosphere containing acetic acid as a carboxylic acid were changed as shown in Table 2.

[0135] (Comparative Example 7) Propionic acid was used instead of acetic acid as the carboxylic acid, the treatment time with the carboxylic acid was 60 minutes, the treatment temperature during the treatment with the carboxylic acid was 120°C, and the partial pressure of the carboxylic acid in the atmosphere during the treatment with the carboxylic acid was 5.0 × 10 -1 A carboxylic acid-containing nickel powder was obtained in the same manner as in Comparative Example 4, except that the temperature was adjusted to 1000 kJ / cm 2 atm.

[0136] The manufacturing conditions for the powders of each of the Examples and Comparative Examples were as follows: for these powders, the peak top temperatures of the peaks in the mass chromatogram of carboxylic acid molecular ions (molecular ions of acetic acid: m / z = 60, molecular ions of propionic acid: m / z = 74) detected when the powders were heated from 38°C to 600°C at a heating rate of 20°C / min in an inert helium atmosphere by TG-MS; the surface area of ​​the nickel particles constituting the obtained powders (1 m 2The content of carboxylic acid per unit volume is shown in Table 2. The ionization method for MS was EI (Electron Ionization). Table 2 also shows the boiling points of the carboxylic acids used in each of the Examples and Comparative Examples 4 to 7. bp [℃], (T bp +100)℃ or more and 600℃ or less, the presence or absence of a peak top in the mass chromatogram of the molecular ion of the carboxylic acid, (T bp -50)℃ or higher (T bp The presence or absence of peak tops in the mass chromatogram of the carboxylic acid molecular ion in the range of +50°C or less is also shown. For the TG-MS, a NETZSCH STA2500 Regulus was used as the TG-DTA for heating the sample, and a JEOL JMS-Q1500GC was used as the MS for mass spectrometry of the substances vaporized by heating the sample. In addition, the surface area of ​​the nickel particles that make up the powder was 1 m 2 The carboxylic acid content per unit weight was determined using a carbon-sulfur (CS) analyzer (HORIBA, EMIA-320V) by measuring (1) the carbon content in the nickel powder before carboxylic acid adsorption and (2) the carbon content in the nickel powder after carboxylic acid adsorption. The difference between (1) and (2) was used to calculate the carbon content increased by carboxylic acid adsorption. This difference was calculated using the carbon content in the carboxylic acid and the specific surface area of ​​the nickel powder before carboxylic acid adsorption. In Table 2, acetic acid is represented as "AA," propionic acid as "PA," ethanol as "EtOH," and isopropanol as "IPA."

[0137] [Table 2]

[0138] [5] Manufacturing fine powder by dry classification The powders of each of the Examples and Comparative Examples, i.e., carboxylic acid-containing nickel powder for each of the Examples and Comparative Examples 4 to 7, nickel powder for Comparative Example 1, and alcohol-treated powder for Examples 2 and 3, were fed into the dry classifier shown in FIG. 1 at a rate of 10 kg per hour, and the supply dispersion pressure was set to 0.6 MPa to obtain powders to be classified.

[0139] Next, the powder to be classified was introduced into the classification chamber, and the temperature inside the classifier was set to 25°C and the suction air volume was set to 8.5 m 3 / min and suction pressure was set at -35 kPa, and dry classification was carried out to produce a fine powder.

[0140] Thereafter, the obtained fine powder was further subjected to dry classification in the same manner as above, that is, dry classification was performed twice in total to obtain the final fine powder.

[0141] [6] Evaluation [6-1] Yield For each of the above examples and comparative examples, the weight of the powder before classification and the weight of the powder after classification, i.e., the weight of the fine powder obtained by performing the classification process twice, were measured, and the yield was calculated using the following formula. Yield (%) = (weight of powder after classification / weight of powder before classification) × 100

[0142] [6-2] Evaluation of particle size distribution The particle size distribution of the nickel powder as the raw material powder and the resulting fine powder was determined for each of the examples and comparative examples by measurement using a laser diffraction / scattering particle size distribution analyzer LA-960 (manufactured by HORIBA Corporation). From the results, the volume-based cumulative fraction 10% value of the particle size distribution (D 10 ) [μm], cumulative fraction 50% value (D 50 ) [μm], cumulative fraction 90% value (D 90 ) [μm] were calculated.

[0143] Also, the D calculated as above 10 [μm], D 50 [μm], D 90 From the value of [μm], (D 90 -D10 ) / D 50 was calculated.

[0144] [6-3] Evaluation of the number of coarse particles For each of the above Examples and Comparative Examples, 1 g of powder after two classifications was mixed with 20 mL of ethanol as a dispersion medium, and the mixture was treated for 1 minute using an ultrasonic cleaner (Honda Electronics Co., Ltd., W-113) to prepare a dispersion. 30 μL of the prepared dispersion was weighed out, dropped onto an aluminum sample stage, and dried to remove the dispersion medium, thereby preparing a measurement sample. The above sample was magnified 10,000 times using a scanning electron microscope (Hitachi High-Technologies Corporation, SU-1510), and 50 fields of view were observed. The particle size was calculated by dividing the D of the target fine powder obtained in [6-2] above. 50 Particles that are 2.0 times or more larger than the particle size were considered to be coarse particles, and the number of coarse particles was calculated.

[0145] [6-4] Smoothness of coating film 100 parts by weight of the powders of each of the Examples and Comparative Examples obtained in [4] above, i.e., the powders before classification, were mixed with 3.0 parts by weight of ethyl cellulose resin (Dow Chemical Company, STD100), and 100 parts by weight of dihydroterpineol acetate, and the mixture was mixed at 2000 rpm for 2 minutes using a hybrid mixer (THINKY Corporation, ARE-310) to obtain a nickel paste. The resulting nickel paste was cast to a film thickness of 10 μm, and the surface roughness (Ra) was measured using a microprofile measuring instrument (Kosaka Laboratory, ET3000i).

[0146] Furthermore, for the fine powders of each of the Examples and Comparative Examples obtained in [5] above, pastes were prepared, coating films were formed using the pastes, and the surface roughness was measured in the same manner as above.

[0147] These results are summarized in Table 3. In addition, the fine powders obtained in the above examples were measured for the volume-based cumulative 50% particle diameter D 50 The number of particles having a particle size 3.0 times or more of the above was determined, and no such particles were found in any of the Examples.

[0148] [Table 3]

[0149] As is clear from Table 3, in each of the above examples, D 50 In each of the examples, the surface roughness of the coating film formed using the paste was small and the surface smoothness was high. Therefore, it can be said that the carboxylic acid-containing nickel powder of each of the examples has excellent dispersibility in the paste. [Industrial Applicability]

[0150] The carboxylic acid-containing nickel powder of the present invention includes a plurality of nickel particles, and has carboxylic acid on the surface of the nickel particles. When the nickel particles are heated from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere by TG-MS, a peak is detected in the mass chromatogram of the molecular ion of the carboxylic acid, and the boiling point of the carboxylic acid is determined to be T bp [°C], the peak top of the peak is (T bp +100)°C or more and 600°C or less, and the surface area of ​​the nickel particles constituting the carboxylic acid-containing nickel powder is 1 m 2The content of the carboxylic acid per 1000g of nickel powder is 155 μg or more and 450 μg or less. Therefore, it is possible to provide a carboxylic acid-containing nickel powder that is highly dispersible in a gas phase and that exhibits high dispersibility in the paste when mixed with an organic solvent or the like and used to form a paste. Furthermore, the method for producing the carboxylic acid-containing nickel powder of the present invention is a method for producing the carboxylic acid-containing nickel powder of the present invention, which includes a step of contacting a gaseous carboxylic acid with nickel powder dispersed in a gas phase. Therefore, it is possible to provide a method for producing a carboxylic acid-containing nickel powder that is highly dispersible in a gas phase and that exhibits high dispersibility in the paste when mixed with an organic solvent or the like and used to form a paste. Therefore, the carboxylic acid-containing nickel powder and the method for producing the carboxylic acid-containing nickel powder of the present invention have industrial applicability. [Explanation of symbols]

[0151] 1...Classifier 3...Casing 4...Entry point 5...Air nozzle 6...Guide vane 7…Fine powder outlet 8…Coarse powder outlet 10...Classification room (classification zone) 11…Dispersion Zone

Claims

1. A carboxylic acid-containing nickel powder comprising a plurality of nickel particles and having carboxylic acid on the surface of the nickel particles, the carboxylic acid is at least one selected from the group consisting of acetic acid and propionic acid, By TG-MS, a peak was detected in the mass chromatogram of the molecular ion of the carboxylic acid when the temperature was raised from 38°C to 600°C at a heating rate of 20°C / min under an inert atmosphere, and the boiling point of the carboxylic acid was determined to be T ｂｐ [°C], the peak top of the peak is (T ｂｐ +100) ° C or more and 600 ° C or less, The surface area of ​​the nickel particles constituting the carboxylic acid-containing nickel powder is 1 m ２ The carboxylic acid-containing nickel powder has a content of the carboxylic acid of 155 μg or more and 450 μg or less per 1000g of the nickel powder.

2. TG-MS showed that when the temperature was increased from 38°C to 600°C at a rate of 20°C / min under an inert atmosphere, (T ｂｐ -50)℃ or higher (T ｂｐ 2. The carboxylic acid-containing nickel powder according to claim 1, wherein the peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid does not exist within a range of +50°C or less.

3. A method for producing the carboxylic acid-containing nickel powder according to claim 1 or 2, comprising: A method for producing a carboxylic acid-containing nickel powder, comprising a step of contacting a gaseous carboxylic acid with nickel powder dispersed in a gas phase.

4. The method for producing a carboxylic acid-containing nickel powder according to claim 3, wherein the nickel powder is dispersed in an atmosphere containing the carboxylic acid in a gaseous state.

5. 4. A method for producing a carboxylic acid-containing nickel powder according to claim 3, wherein the nickel powder is dispersed in the gas phase at the time of production, and the carboxylic acid in a gaseous state is supplied to the gas phase while the nickel powder is dispersed in the gas phase.

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