Nickel powder containing carboxylic acid and method for producing nickel powder containing carboxylic acid

Abstract

The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, and the surfaces of the nickel particles have carboxylic acid. When the temperature is increased from 38°C to 600°C at a heating rate of 20°C / min under an inert atmosphere, a peak is detected in the mass chromatogram of the molecular ion of the carboxylic acid by TG-MS, and the boiling point of the carboxylic acid is set as T bp [℃], the peak top of the peak exists at (T bp In the range of 100°C to 600°C, the nickel particles constituting the carboxylic acid-containing nickel powder have a thickness of 1 m 2 The content of the carboxylic acid per surface area is 155 μg to 450 μg. The present invention provides a carboxylic acid-containing nickel powder having high dispersibility in the gas phase and, when mixed with an organic solvent or the like to form a paste, high dispersibility in the paste.

Description

Technical Field

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

[0002] Conductive metal powders have traditionally been used as conductive materials for electronic components. In multilayer ceramic capacitors, the rapid progress in thinning both ceramic and internal electrode layers has necessitated the formation of thin, uniform internal electrode layers. Therefore, conductive metal powders used in multilayer ceramic capacitor internal electrodes must have a narrow particle size distribution, be free of coarse particles that could contact adjacent internal electrodes sandwiching the dielectric layer and cause a short circuit, and be able to be uniformly dispersed in a paste when mixed with an organic solvent or the like.

[0003] Until now, methods for producing powders with a desired particle size distribution have used methods of classifying powders produced by various manufacturing methods. Examples of such classification methods include methods that utilize the difference in sedimentation velocity of particles in the gas phase or liquid phase to classify powders based on particle size differences. Classification performed in the gas phase is called dry classification, while classification performed in the liquid phase is called wet classification. Wet classification offers excellent classification accuracy, but requires the use of a liquid as a dispersion medium, and drying and pulverization are required after classification. Therefore, dry classification offers significantly lower costs.

[0004] However, conventional dry classification has the following problems: powder adheres to various locations inside the classifier, clogging the powder supply port and the inside of the piping, making it difficult to operate for a long time; and the classification accuracy is low, resulting in a low yield.

[0005] As a method for solving such a problem, Patent Document 1 discloses a method of mixing a powder with an auxiliary agent containing an alcohol having a boiling point lower than 200° C., such as ethanol, and dry-classifying the powder while vaporizing the auxiliary agent.

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

[0007] Patent Document 3 discloses a method for dry-classifying a powder containing nickel by mixing it with an auxiliary agent containing an organic solvent having a flash point of 80°C or higher, such as diethylene glycol, and vaporizing the auxiliary agent. Furthermore, a method for dry-classifying a powder containing nickel by mixing it with an auxiliary agent containing water and vaporizing the auxiliary agent is disclosed.

[0008] Furthermore, Patent Document 4 discloses a method of mixing a powder with diethylene glycol monomethyl ether as a liquid auxiliary agent and subjecting the powder to dry classification.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication No. 2010 / 047175

[0012] Patent Document 2: International Publication No. 2010 / 057206

[0013] Patent Document 3: International Publication No. 2010 / 106716

[0014] Patent Document 4: International Publication No. 2012 / 124453 Summary of the Invention

[0015] Technical problem solved by the invention

[0016] However, the inventors of this application have discovered the following problems: For example, dry classification by adsorbing an auxiliary agent such as ethanol onto the powder allows the classifier to operate for extended periods of time. However, the resulting powder contains a large number of coarse particles, necessitating repeated classification to reduce the number of these coarse particles. Furthermore, while repeated classification can sometimes reduce the number of coarse particles, this is time-consuming and costly, resulting in reduced productivity and a significant decrease in the yield of the resulting powder.

[0017] Furthermore, the powder obtained as described above may be difficult to uniformly disperse in a paste obtained by mixing with an organic solvent or the like.

[0018] Therefore, an object of the present invention is to provide a carboxylic acid-containing nickel powder having high dispersibility in a gas phase and, when mixed with an organic solvent or the like and used to form a paste, high dispersibility in the paste and a method for producing the same.

[0019] Technical means to solve the problem

[0020] Such an object is achieved by the present invention described in the following (1) to (9).

[0021] (1) A carboxylic acid-containing nickel powder comprising a plurality of nickel particles, wherein the nickel particles have carboxylic acid on their surfaces, wherein:

[0022] By TG-MS, when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere, a peak was detected in the mass chromatogram of the molecular ion of the carboxylic acid, and the boiling point of the carboxylic acid was set as T bp[℃], the peak top of the peak exists at (T bp In the range of above +100)℃ and below 600℃,

[0023] The nickel particles constituting the carboxylic acid-containing nickel powder have a 2 The content of the carboxylic acid per surface area is 155 μg or more and 450 μg or less.

[0024] (2) The carboxylic acid-containing nickel powder according to (1), wherein, when heated from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere, the bp -50)℃ or above (T bp In the range of +50)°C or lower, there is no peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid.

[0025] (3) The carboxylic acid-containing nickel powder according to (1) or (2), wherein the boiling point of the carboxylic acid is 100° C. to 270° C.

[0026] (4) The carboxylic acid-containing nickel powder according to any one of (1) to (3), wherein the molecular weight of the carboxylic acid is 40 or more and 160 or less.

[0027] (5) The carboxylic acid-containing nickel powder according to any one of (1) to (4), wherein the carboxylic acid has a carbon number of 2 or more and 9 or less.

[0028] (6) The carboxylic acid-containing nickel powder according to any one of (3) to (5), wherein the carboxylic acid is at least one selected from acetic acid and propionic acid.

[0029] (7) A method for producing a carboxylic acid-containing nickel powder, which is a method for producing the carboxylic acid-containing nickel powder according to any one of (1) to (6), wherein:

[0030] The method includes a step of bringing gaseous carboxylic acid into contact with nickel powder dispersed in a gas phase.

[0031] (8) The method for producing a carboxylic acid-containing nickel powder according to (7), wherein the nickel powder is dispersed in an atmosphere containing the carboxylic acid in a gaseous state.

[0032] (9) The method for producing carboxylic acid-containing nickel powder according to (7), wherein the carboxylic acid in a gaseous state is supplied to the gas phase while the nickel powder, which is dispersed in the gas phase during production, is dispersed in the gas phase.

[0033] Effects of the Invention

[0034] The present invention can provide a carboxylic acid-containing nickel powder having high dispersibility in a gas phase and, when mixed with an organic solvent or the like to form a paste, high dispersibility in the paste, and a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a diagram showing a configuration example of a classifier used for obtaining a fine powder having an extremely small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention. DETAILED DESCRIPTION

[0036] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0037] [1] Nickel powder containing carboxylic acid

[0038] First, the carboxylic acid-containing nickel powder of the present invention will be described.

[0039] The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, each of which has carboxylic acid on its surface. In other words, the carboxylic acid-containing nickel powder of the present invention comprises carboxylic acid-adsorbed nickel particles, in which carboxylic acid is adsorbed on the surface of nickel particles serving as base particles.

[0040] Furthermore, regarding the nickel powder containing carboxylic acid of the present invention, when the temperature is increased from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere, 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 set as T bp [℃], the peak top of the peak exists at (T bp The nickel particles are within the range of 600°C to 100°C, and the ... 2 The content of the carboxylic acid per surface area is 155 μg or more and 450 μg or less.

[0041] By satisfying these conditions, 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 to form a paste, has high dispersibility in the paste. Furthermore, by ensuring excellent dispersibility of the carboxylic acid-containing nickel powder in the gas phase, coarse particles can be suitably removed by dry classification, and, for example, fine powders with excellent yields and sharp particle size distribution can be suitably obtained by dry classification. Furthermore, by ensuring excellent dispersibility of the carboxylic acid-containing nickel powder in a paste containing the carboxylic acid-containing nickel powder, the smoothness of a coating film formed using the paste can be improved.

[0042] It should be noted that the peak top value of the peak in the mass chromatogram of the molecular ions of the carboxylic acid detected by TG-MS can be adjusted, for example, by adjusting the adsorption method of the carboxylic acid on the nickel particles. More specifically, the peak top value of the peak in the mass chromatogram of the molecular ions of the carboxylic acid detected by TG-MS can be appropriately adjusted by adjusting, for example, the adsorption method of the carboxylic acid on the nickel particles, the adsorption treatment conditions, the adsorption amount, and the like.

[0043] In this specification, the term "coarse particles" refers to a volume-based cumulative 50% particle size (D 50 ), particles having a sufficiently large particle size, for example, may be set to a particle size of D of the powder being the object. 50 The particles may be 1.5 times or more larger than the particle size of the powder to be tested, and for example, the particle size may be D 50 The particles may be 2.0 times or more in diameter, and for example, the particle size may be D of the powder being the object. 50 2.5 times more particles.

[0044] In this specification, the cumulative 50% particle size (D 50 ), unless otherwise specified, refers to the 50% value of the volume-based cumulative fraction of the particle size distribution obtained by using a laser particle size distribution measuring device, for example, it can be obtained by measuring using a laser diffraction / scattering particle size distribution measuring device LA-960 (manufactured by HORIBA).

[0045] In TG-MS, for example, STA2500 Regulus manufactured by NETZSCH can be used as a TG-DTA for heating a sample, and JMS-Q1500GC manufactured by JEOL Ltd. can be used as an MS for mass analysis of a substance vaporized by heating the sample.

[0046] In addition, the nickel particles constituting the carboxylic acid-containing nickel powder are 2 The content of carboxylic acid in the surface area can be determined by measurement using a CS (carbon-sulfur) analyzer (for example, EMIA-320V manufactured by HORIBA Corporation).

[0047] As described above, in the nickel powder containing carboxylic acid of the present invention, analysis based on TG-MS shows that in the mass chromatogram of the molecular ion of carboxylic acid, a predetermined region ((T bpA peak appears in the range of 600°C to 100°C (above +100°C). This is believed to be caused by the adsorption of carboxylic acid on nickel particles in a specific manner. The detailed mechanism is still unclear, but the inventors speculate that, for example, since carboxylic acid is chemically adsorbed on nickel particles, it is adsorbed more firmly than in the case of physical adsorption, so a peak appears in a high temperature range such as above +100°C, which is the boiling point of carboxylic acid. By making the nickel particles adsorb carboxylic acid in a specific manner and adsorbing carboxylic acid on the surface of the nickel particles in an appropriate proportion, the excellent effect described above can be obtained, namely, improving the dispersibility in the gas phase, and improving the dispersibility in the paste when mixed with an organic solvent or the like to form a paste.

[0048] In addition, by making nickel particles per 1m 2 When the content of the carboxylic acid in the surface area is equal to or greater than the above lower limit, the dispersibility of the carboxylic acid-containing nickel powder in the gas phase can be sufficiently excellent.

[0049] In addition, by making nickel particles per 1m 2 When the content of the carboxylic acid in the surface area is below the above upper limit, the carboxylic acid-containing nickel powder can have sufficiently excellent dispersibility in the paste when mixed with an organic solvent or the like to form a paste.

[0050] It should be noted that, in this specification, unless otherwise specified, "boiling point" refers to the boiling point at 1 atmosphere, that is, the normal boiling point.

[0051] When the carboxylic acid-containing nickel powder contains multiple carboxylic acids, it is sufficient that at least one carboxylic acid satisfies the above conditions. It is particularly preferred that the carboxylic acid with the highest content among the multiple carboxylic acids satisfies the above conditions. It is more preferred that all types of carboxylic acids contained in the carboxylic acid-containing nickel powder satisfy the above conditions.

[0052] 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 TG-MS analysis is present at (T bp It is sufficient to be within the range of (T bp The temperature is preferably in the range of (Tb+120)°C to 580°C, more preferably in the range of (Tb+150)°C to 560°C, and further preferably in the range of (Tb+150)°C to 560°C. bp In the range of (T bp Within the range of above +230)℃ and below 520℃.

[0053] Thereby, the above-mentioned effect is more significantly exerted.

[0054] In addition, in the carboxylic acid-containing nickel powder of the present invention, the nickel particles have a 2The content of carboxylic acid in the surface area may be 155 μg or more and 450 μg or less, 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 content of carboxylic acid per surface area is preferably 160 μg to 350 μg, more preferably 170 μg to 350 μg, and even more preferably 250 μg to 350 μg.

[0055] Thereby, the above-mentioned effect is more significantly exerted.

[0056] The nickel powder containing carboxylic acid of the present invention is subjected to the above-mentioned TG-MS analysis as long as (T bp The peak top of the peak in the mass chromatogram of the molecular ion of carboxylic acid may be present in the range of (T + 100) ° C to 600 ° C, and the peak top of the peak in the mass chromatogram of the molecular ion of carboxylic acid may be present outside the above range. bp -50)℃ or above (T bp The peak top of the peak in the mass chromatogram of the molecular ion of carboxylic acid does not exist in the range of +50)°C or less.

[0057] 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 carboxylic acids, it is preferred that at least one carboxylic acid satisfies the above conditions. It is particularly preferred that the carboxylic acid with the highest content among the multiple carboxylic acids satisfies the above conditions. It is even more preferred that all carboxylic acids contained in the carboxylic acid-containing nickel powder satisfy the above conditions.

[0058] Volume-based cumulative 50% particle size D of carboxylic acid-containing nickel powder 50 , preferably more than 0.01 μm and 10 μm or less, more preferably more than 0.03 μm and 2.5 μm or less, further preferably more than 0.05 μm and 1.2 μm or less, and most preferably more than 0.10 μm and 0.80 μm or less.

[0059] [1-1] Nickel particles

[0060] Nickel particles constitute a main component of the carboxylic acid-containing nickel powder and are mainly composed of nickel.

[0061] The nickel particles may be mainly composed of nickel, for example, nickel as a single metal, or a nickel alloy.

[0062] The component with the highest content in the nickel particles may be nickel. 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. 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, components other than nickel in the nickel particles are preferably only components that are included as unavoidable components, and the content of components other than nickel in the nickel particles is preferably 1000 ppm or less.

[0063] The shape of the nickel particles is not particularly limited, and various shapes such as spherical, flaky, and granular are exemplified. One type selected from these may be used, or two or more types may be used in combination.

[0064] In this specification, the term "spherical shape" refers to a particle shape having a major axis / minor axis ratio of 2 or less. The term "flaky shape" refers to a particle shape having a major axis / minor axis ratio of more than 2.

[0065] The method for producing nickel particles is not particularly limited, and examples thereof include electrolysis, atomization, mechanical pulverization, wet reduction, spray pyrolysis, chemical vapor deposition, and physical vapor deposition.

[0066] [1-2]Carboxylic acid

[0067] The carboxylic acid-containing nickel powder contains carboxylic acid in addition to the above-mentioned nickel particles.

[0068] Most of the carboxylic acid contained in the carboxylic acid-containing nickel powder is adsorbed on the surface of the nickel particles serving as the mother particles. In other words, most of the carboxylic acid contained in the carboxylic acid-containing nickel powder is contained as a constituent component of the carboxylic acid-adsorbed nickel particles.

[0069] The adsorption of carboxylic acid on nickel particles can be in the form of either physical adsorption or chemical adsorption.

[0070] The carboxylic acid is not particularly limited as long as it is a compound having a carboxyl group.

[0071] The boiling point of the carboxylic acid is preferably 100°C to 270°C, more preferably 105°C to 250°C, further preferably 110°C to 200°C, and most preferably 115°C to 170°C.

[0072] This improves the dispersibility of the carboxylic acid-containing nickel powder in the gas phase and the dispersibility of the carboxylic acid-containing nickel powder in a paste formed by mixing the carboxylic acid-containing nickel powder with an organic solvent or the like. Furthermore, when producing the carboxylic acid-containing nickel powder, the carboxylic acid used as a raw material can be preferably handled in a liquid state, thereby improving workability. Furthermore, when the carboxylic acid is adsorbed on the nickel powder in a vaporized state, the carboxylic acid can be more preferably adsorbed on the nickel powder.

[0073] Furthermore, the carboxylic acid is preferably a monocarboxylic acid.

[0074] This can 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 a paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like to form the paste.

[0075] 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.

[0076] This can 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 a paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like to form the paste.

[0077] The number of carbon atoms in the carboxylic acid is preferably 2 or more and 9 or less, more preferably 2 or more and 7 or less, and even more preferably 2 or more and 5 or less.

[0078] This can 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 a paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like to form the paste.

[0079] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, isobutyric acid, butyric acid, crotonic acid, isovaleric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, lactic acid, oxalic acid, succinic acid, oleic acid, acrylic acid, and methacrylic acid. One or more of these can be used in combination. Preferably, at least one selected from acetic acid and propionic acid is used, and more preferably, acetic acid is used.

[0080] This can 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 a paste when the carboxylic acid-containing nickel powder is mixed with an organic solvent or the like to form the paste.

[0081] [1-3] Applications of Nickel Powder Containing Carboxylic Acid

[0082] The carboxylic acid-containing nickel powder of the present invention can be used for any purpose, but can be used as a conductive powder, particularly preferably as a conductive powder for use in conductive pastes. Due to its high dispersibility as a powder, its dispersibility in the paste is also easily increased. Furthermore, the carboxylic acid-containing nickel powder of the present invention is preferably used as a conductive powder after being subjected to the classification step described below, particularly after being subjected to the dry classification step, and more preferably as a conductive powder for use in conductive pastes. Furthermore, the carboxylic acid-containing nickel powder of the present invention has high fluidity and excellent handleability, making it easy to handle for various applications.

[0083] By subjecting the carboxylic acid-containing nickel powder of the present invention to a dry classification process described later, a fine powder having a small average particle size, a narrow particle size distribution, and almost no coarse particles can be suitably obtained. Compared with the carboxylic acid-containing nickel powder of the present invention before classification, such fine powder has a narrower particle size distribution, and therefore can form a coating film with better smoothness. When the fine powder is used for internal electrodes, an electrode layer with uniform thickness can be formed. In addition, since it almost does not contain coarse particles, it is possible to suitably prevent the conductive powder particles from contacting both sides of the internal electrode and causing a short circuit. Therefore, even for such applications requiring particularly high reliability, a fully satisfactory effect can be obtained. Therefore, when the fine powder is used to form internal conductors (internal electrodes) and terminal electrodes of multilayer ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, and multilayer piezoelectric actuators, the above-mentioned effect is more significantly exerted.

[0084] The conductive powder can be mixed with, for example, glass frit and an organic vehicle to form a conductive paste for forming a conductive portion of an electronic component.

[0085] [2] Method for producing carboxylic acid-containing nickel powder

[0086] Next, the method for producing the carboxylic acid-containing nickel powder of the present invention will be described.

[0087] The method for producing carboxylic acid-containing nickel powder of the present invention is a method for producing the carboxylic acid-containing nickel powder of the present invention, comprising the step of bringing gaseous carboxylic acid into contact with nickel powder, which is an aggregate of a plurality of nickel particles dispersed in a gas phase.

[0088] This method provides a method for producing 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. Furthermore, compared to contacting gaseous carboxylic acid with stationary nickel powder, the concentration of the carboxylic acid is lower, and the carboxylic acid can be adsorbed on the surface of the nickel particles in a significantly shorter time, which is advantageous from the perspectives of reduced carboxylic acid consumption and shortened production time.

[0089] The method for producing carboxylic acid-containing nickel powder of the present invention only needs to include a step of contacting gaseous carboxylic acid with nickel powder dispersed in a gas phase. For example, it is preferred to disperse nickel powder as an aggregate of multiple nickel particles in an atmosphere containing gaseous carboxylic acid.

[0090] In addition, in the method for producing carboxylic acid-containing nickel powder of the present invention, the process of bringing the gaseous carboxylic acid into contact with the nickel powder can be carried out by supplying the gaseous carboxylic acid into the gas phase while the nickel powder, which is in a dispersed state in the gas phase during generation, is dispersed in the gas phase.

[0091] By introducing the carboxylic acid gas after the nickel powder is generated in the gas phase and before the nickel powder is recovered, the carboxylic acid gas can be brought into contact with the nickel powder in a better dispersed state, thereby allowing the carboxylic acid to be adsorbed more uniformly.

[0092] Examples of methods for producing the nickel powder dispersed in the gas phase include gas phase methods such as chemical vapor deposition and physical vapor deposition, atomization, and spray pyrolysis. 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 an appropriate condition.

[0093] It should be noted that the method for producing carboxylic acid-containing nickel powder of the present invention only needs to include a step of bringing gaseous carboxylic acid into contact with nickel powder dispersed in a gas phase. The method is not limited to a method of bringing gaseous carboxylic acid into contact with nickel powder just after it is produced. For example, gaseous carboxylic acid may also be brought into contact with nickel powder that has been recovered once.

[0094] [3] Method for producing fine powder using the carboxylic acid-containing nickel powder of the present invention

[0095] Next, a method for producing fine powder using the carboxylic acid-containing nickel powder of the present invention will be described.

[0096] The method for producing fine powder of this embodiment is to obtain a volume-based cumulative 50% particle size D 50 A method for producing fine powder having a diameter of 0.01 μm or more and 5.0 μm or less, comprising: making D 50 A step of generating classified powder by dispersing carboxylic acid-containing nickel powder having a size of more than 0.01 μm and less than 10 μm in a gas phase to obtain classified powder to be classified; and a step of dry-classifying the classified powder.

[0097] This can provide a method for producing a particle with a volume-based cumulative 50% particle diameter D having a very small number of coarse particles with high productivity. 50 A method for producing fine powder having a particle size within the range of 0.01 μm to 5.0 μm.

[0098] This excellent effect is believed to be due to the following reasons. Specifically, by using carboxylic acid-containing nickel powder, obtained by adsorbing carboxylic acid onto nickel particles under specific conditions, the powder's dispersibility in the gas phase is improved, thereby enhancing classification accuracy, compared to dry classification methods in which an auxiliary agent such as ethanol is adsorbed onto the powder. Consequently, the number of coarse particles in the produced fine powder can be significantly reduced. Furthermore, this reduces the number of classification cycles, improving productivity.

[0099] 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, so that a coating film formed using the paste can have excellent smoothness.

[0100] Furthermore, the use of the carboxylic acid-containing nickel powder of the present invention improves powder fluidity, reduces powder adhesion to the classifier, and improves yield. Furthermore, by reducing powder adhesion to the classifier, the classifier's powder supply port and piping are less likely to become clogged, thereby extending the classifier's operating time and improving productivity.

[0101] Furthermore, in this embodiment, the use of carboxylic acid-containing nickel powder, obtained by pre-adsorbing carboxylic acid onto nickel particles under predetermined conditions, is advantageous in simplifying and miniaturizing the structure of the apparatus used for producing the fine powder. Furthermore, the use of carboxylic acid-containing nickel powder, obtained by pre-adsorbing carboxylic acid onto nickel particles under predetermined conditions, results in a higher fluidity of the powder compared to the case of adding nickel powder to a disperser without adsorbing carboxylic acid, making it less likely to adhere to the interior of the disperser, and thus allowing for smoother movement of the powder within the disperser.

[0102] It should be noted that, in this specification, classification refers to the operation of dividing powder into a group of larger particles (i.e., coarse powder) and a group of smaller particles (i.e., fine powder) according to their size. Specifically, in this specification, fine powder refers to the cumulative 50% particle size D based on volume. 50 The group of particles with a diameter of 0.01 μm or more and 5.0 μm or less, coarse powder refers to D 50 A group of particles larger than micropowder.

[0103] [3-1] Classifier

[0104] Figure 1 This is a diagram showing a configuration example of a classifier used for obtaining a fine powder having an extremely small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention.

[0105] It should be noted that in the following description, Figure 1 The description will be given with the upper side in the figure being referred to as “upper” and the lower side being referred to as “lower”.

[0106] The classifier 1 is an airflow classifier that performs classification using centrifugal force acting on powder, and includes a housing 3 forming a classification chamber 10 .

[0107] A dispersion zone 11 for dispersing the carboxylic acid-containing nickel powder before classification is provided upstream of the classification chamber (classification zone) 10. The classification chamber 10 is a zone for classifying the dispersed carboxylic acid-containing nickel powder.

[0108] The classifier 1 also includes an inlet 4 for introducing carboxylic acid-containing nickel powder into the dispersion zone 11; an air nozzle 5 for ejecting high-pressure air (primary air) into the dispersion zone 11; guide vanes 6 for flowing secondary air into the classification chamber 10 to form a swirling airflow within the classification chamber 10; a fine powder discharge port 7 opening in the center of the upper portion of the classification chamber 10; and a coarse powder discharge port 8 opening along the outer periphery of the lower portion of the classification chamber 10.

[0109] Next, a method of dispersing and classifying the carboxylic acid-containing nickel powder using such a classifier 1 will be described.

[0110] The carboxylic acid-containing nickel powder is introduced into the dispersion zone 11 from the inlet 4. The carboxylic acid-containing nickel powder is dispersed by the primary air injected into the dispersion zone 11. The carboxylic acid-containing nickel powder is then introduced into the classification chamber 10 in a dispersed state.

[0111] In the classification chamber 10, secondary air is caused to flow into the classification chamber 10 through the guide vanes 6, causing the airflow to rotate in the classification chamber 10 and be discharged from the upper center of the classification chamber 10. The outward centrifugal force generated by the rotation of the airflow and the flow of gas moving toward the center separate the carboxylic acid-containing nickel powder in the solid-gas mixed fluid into coarse powder and fine powder.

[0112] That is, the coarse powder moves radially outward within the classification chamber 10 due to the outward centrifugal force generated by the rotation of the airflow and is recovered from the coarse powder discharge port 8 at the lower periphery of the classification chamber 10. On the other hand, the fine powder moves radially inward within the classification chamber 10 due to the flow of the gas moving toward the center and is recovered from the fine powder discharge port 7 at the upper center of the classification chamber 10.

[0113] A suction pump (not shown) is connected to the fine powder discharge port 7 , and the fine powder is discharged and recovered together with the air (exhaust gas) in the classification chamber 10 .

[0114] The classified powder generating step corresponds to the step performed in the dispersion zone 11 , and the dry classification step corresponds to the step performed in the classification chamber (classification zone) 10 .

[0115] That is, the carboxylic acid-containing nickel powder dispersed in the dispersion area 11, that is, the carboxylic acid-containing nickel powder introduced into the classification chamber 10, is referred to as a powder to be classified in this specification.

[0116] It should be noted that, in the above description, an airflow classifier that utilizes the centrifugal force generated by a rotating airflow for classification is used as an example. However, the classification method of the classifier is not particularly limited. For example, classification using the centrifugal force generated by the rotation of the rotor, classification using gravity, or classification using inertial force may also be used.

[0117] In the present invention, the step of generating the classified powder and the step of dry classification are not limited to being performed using the same apparatus, and may be performed using separate apparatuses. Specifically, the carboxylic acid-containing nickel powder may be dispersed in a disperser to obtain the classified powder, and then the classified powder may be classified using a dry classifier.

[0118] [3-2] Classified powder generation process

[0119] In the classified powder generating step, a classified powder is obtained in which the carboxylic acid-containing nickel powder is dispersed in a gas phase.

[0120] The feeding rate of the carboxylic acid-containing nickel powder to the classifier, i.e., for example, Figure 1 In the classifier 1 shown, the supply rate of the carboxylic acid-containing nickel powder from the inlet 4 to the dispersion zone 11, although it also depends on the size (capacity) of the classifier, is preferably from 1 kg / hour to 20 kg / hour, more preferably from 3 kg / hour to 15 kg / hour, and even more preferably from 5 kg / hour to 12 kg / hour.

[0121] This can further improve the dispersibility of the carboxylic acid-containing nickel powder and the productivity of the fine powder.

[0122] Supply dispersion pressure during dispersion, i.e., for example Figure 1 In the classifier 1 shown, the pressure of the dispersion air injected from the air nozzle 5 into the dispersion zone 11 is not particularly limited, but is preferably 0.2 MPa to 1.0 MPa, more preferably 0.4 MPa to 0.8 MPa, and even more preferably 0.5 MPa to 0.7 MPa.

[0123] This can further improve the dispersibility of the carboxylic acid-containing nickel powder and the productivity of the fine powder.

[0124] [3-2] Dry Classification Process

[0125] In the dry classification step, the powder to be classified obtained in the powder to be classified generating step is dry classified.

[0126] Because the powder being classified is optimally dispersed in the gas phase, the classification accuracy during the dry classification process is improved. Consequently, the number of coarse particles contained in the resulting fine powder can be significantly reduced. Furthermore, by improving classification accuracy, the number of classification cycles can be reduced, thereby improving productivity.

[0127] Furthermore, due to the improved fluidity of the classified powder, the adhesion of classified powder to the classifier is reduced, thus improving the yield. Furthermore, by reducing the adhesion of classified powder to the classifier, the classifier's powder supply port and the interior of the piping are less likely to become clogged, thereby extending the classifier's operating time and improving productivity.

[0128] This makes it possible to produce fine powder containing an extremely small number of coarse particles with high productivity.

[0129] The gas phase temperature during the dry classification step is not particularly limited, but is preferably 60°C to 300°C, more preferably 100°C to 250°C, and even more preferably 150°C to 200°C.

[0130] This more effectively prevents problems such as heat-induced particle deformation and deterioration of the particle's constituent materials. The increased airflow velocity increases centrifugal force and prevents water vapor from adhering to the particles, further improving classification accuracy. Furthermore, productivity can be further enhanced. Furthermore, the number of coarse particles in the fine powder can be significantly reduced.

[0131] The suction air volume during the dry classification process, i.e., Figure 1 In the classifier 1 shown, the suction air volume of the suction pump connected to the fine powder discharge port 7 is not particularly limited, but is preferably 5.0 m 3 / min over 30m 3 / minute or less, more preferably 6.0m 3 / min more than 20m 3 / minute or less, more preferably 7.0m 3 / min above 9.0m 3 / min or less.

[0132] Thereby, the powder to be classified can be classified more efficiently.

[0133] The suction pressure for dry classification, i.e. Figure 1 In the classifier 1 shown, the suction pressure of the suction pump connected to the fine powder discharge port 7 is not particularly limited, but is preferably -60 kPa to 5 kPa, more preferably -50 kPa to 10 kPa, and even more preferably -40 kPa to 15 kPa.

[0134] Thereby, the powder to be classified can be classified more appropriately.

[0135] The powder to be classified is classified into fine powder and coarse powder by dry classification. The powder to be classified is classified into, for example, a volume-based cumulative 50% particle size D 50 Fine powder in the range of 0.01 μm to 5.0 μm, and D 50 A coarse powder larger than a fine powder, wherein the fine powder is recovered as the fine powder.

[0136] In the above manner, a volume-based cumulative 50% particle size D is produced. 50 It is a fine powder in the range of 0.01 μm to 5.0 μm.

[0137] The number of coarse particles in the fine powder thus produced is extremely small. In addition, secondary aggregation can be prevented by adsorbing carboxylic acid in an appropriate state on the fine powder.

[0138] Furthermore, the above method improves classification accuracy, reducing the number of classification cycles. Furthermore, the adhesion of classified powder to the classifier is reduced, thereby improving yield. Furthermore, by reducing adhesion to the classifier, the classifier's powder supply port, the interior of the piping, and other components are less likely to become clogged, thereby extending the classifier's operating time and improving productivity.

[0139] It should be noted that the dry classification process may be performed only once, or may be repeated multiple times, thereby further improving the classification accuracy.

[0140] The yield of fine powder in the dry classification step is not particularly limited, but is preferably 80% or higher, more preferably 81% or higher, further preferably 82% or higher, and most preferably 83% or higher.

[0141] Therefore, the effect of the present invention is more significant.

[0142] It should be noted that, in this specification, the yield of fine powder in the dry classification step is a value obtained by the following formula based on 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:

[0143] Yield (%) = (weight of powder after classification / weight of powder before classification) × 100

[0144] The volume-based cumulative 50% particle size D of the fine powder produced by the method of the present invention is 50 The particle size can be within the range of 0.01μm to 5.0μm. 50 The thickness 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.

[0145] Thus, a fine powder with a more ideal particle size distribution can be obtained. 50 When the value is within such a range, coarse particles are likely to become a problem, and the adverse effects caused by coarse particles are particularly likely to occur. 50 When the value is within such a range, the above-mentioned problems can be more effectively prevented. 50 When the value is within the above range, the effects of the present invention are more significantly exhibited.

[0146] In the fine powder produced by the method of the present invention, the volume-based cumulative fraction 10% value of the particle size distribution measured using a laser particle size distribution analyzer is defined as D 10 [μm], set the cumulative score 50% value to D 50 [μm], set the cumulative score 90% value as 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.

[0147] (D 90 -D 10 ) / D 50 It is an indicator of the uniformity of particle size distribution. 90 -D 10 ) / D 50 The smaller the value, the narrower the particle size distribution, that is, the more uniform the particle size.

[0148] As a result, the particle size of the fine powder becomes more uniform and suitable for various applications.

[0149] Furthermore, 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.

[0150] This can more effectively prevent the occurrence of various problems caused by the inclusion of coarse particles in the fine powder.

[0151] The number of the coarse particles can be measured, for example, as follows.

[0152] First, 1.0 g of fine powder is mixed with 20 mL of ethanol, and then treated with an ultrasonic cleaning machine (e.g., W-113 manufactured by Honda Electronics Co., Ltd.) for 1 minute to prepare a dispersion. 30 μL of the dispersion prepared in this way is weighed, dropped onto an aluminum sample stand, dried, and the dispersion medium is removed to prepare a sample for measurement. For the sample for measurement, a scanning electron microscope (e.g., SU-1510 manufactured by HITACHI HIGH-TECHNOLOGIES) is used to observe 50 fields of view at a magnification of 10,000 times. Calculate the cumulative 50% particle size D of the volume basis of the fine powder. 50 The total number of particles having a particle size 1.5 times or more of the particle size of the coarse particles is taken as the number of coarse particles.

[0153] As mentioned above, although the preferred embodiment of the present invention was described, the present invention is not limited thereto.

[0154] For example, the apparatus applicable to the method for producing fine powder is not limited to the apparatus described in the above embodiment.

[0155] Example

[0156] The present invention is described in more detail below with reference to specific examples, but the present invention is not limited to the following examples. In the following description, the treatments without any particular temperature or humidity conditions are performed at room temperature (25°C) and a relative humidity of 50%. In addition, for various measurement conditions, the values ​​at room temperature (25°C) and a relative humidity of 50% are shown without any particular temperature or humidity conditions. In addition, the cumulative fraction 10% value D of the carboxylic acid-containing nickel powder and fine powder is based on the volume basis. 10 、Cumulative score 50% value D 50 , cumulative score 90% value D 90 , was determined by measurement using a laser diffraction / scattering particle size distribution analyzer LA-960 (manufactured by HORIBA Corporation).

[0157] In addition, the conditions of the carboxylic acids used in the following examples are summarized in Table 1.

[0158] [Table 1]

[0159] carboxylic acid Boiling point [℃] Molecular weight Number of carbon atoms Acetic acid (AA) 118.5 60.05 2 Propionic acid (PA) 141 74.08 3

[0160] [4] Production of nickel powder containing carboxylic acid

[0161] (Example 1)

[0162] First, prepare the volume-based cumulative 50% particle size D 50 It is nickel powder with a particle size of 0.31 μm.

[0163] The nickel powder was dispersed in an atmosphere containing acetic acid as a carboxylic acid for 10 seconds to obtain a carboxylic acid-containing nickel powder as an acetic acid-adsorbed nickel powder. It should be noted that the acetic acid used was acetic acid with a purity close to 100% (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7+%). Furthermore, when dispersing the nickel powder, the temperature of the atmosphere containing acetic acid was adjusted to 100° C. Furthermore, the partial pressure of acetic acid in the atmosphere was 6.6×10 -5 atm.

[0164] (Example 2)

[0165] 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 changed to 6.6×10 -6 Atm, a carboxylic acid-containing nickel powder as acetic acid-adsorbed nickel powder was obtained in the same manner as in Example 1 except that the above-mentioned conditions were met.

[0166] (Example 3)

[0167] A 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 the carboxylic acid-containing atmosphere were changed as shown in Table 2.

[0168] (Example 4)

[0169] First, prepare a powder of nickel acetate tetrahydrate. Spray the powder of nickel acetate tetrahydrate and heat it to 1500°C in a gas phase to obtain nickel powder dispersed in the gas phase. While the nickel powder is dispersed in the gas phase, adjust the temperature of the gas phase to 300°C. In the gas phase in which the nickel powder is dispersed, supply acetic acid as a carboxylic acid and treat for 10 seconds to obtain a carboxylic acid-containing nickel powder as acetic acid-adsorbed nickel powder. Acetic acid with a purity close to 100% (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7+%) is used. In addition, when the treatment with acetic acid as a carboxylic acid is performed, the partial pressure of acetic acid in the gas phase is 6.6×10 -5 In addition, the volume-based cumulative 50% particle size D was measured by recovering nickel powder before supplying acetic acid as carboxylic acid. 50 It is 0.31μm.

[0170] (Example 5)

[0171] The gas phase temperature during the supply of carboxylic acid was changed to 500°C, and the partial pressure of acetic acid in the gas phase during the treatment of acetic acid as the carboxylic acid was changed to 1.3×10 -5 Atm, a carboxylic acid-containing nickel powder as acetic acid-adsorbed nickel powder was obtained in the same manner as in Example 4 except that the above-mentioned conditions were met.

[0172] (Example 6)

[0173] The partial pressure of acetic acid in the gas phase during the treatment of acetic acid as a carboxylic acid was changed to 6.6×10 -5 Atm, a carboxylic acid-containing nickel powder as acetic acid-adsorbed nickel powder was obtained in the same manner as in Example 5 except that the above-mentioned conditions were met.

[0174] (Comparative Example 1)

[0175] The powder of this comparative example was the nickel powder used as the raw material powder in Example 1, but was not subjected to a treatment with carboxylic acid. In other words, the powder of this comparative example was a nickel powder that was not treated with carboxylic acid.

[0176] (Comparative Example 2)

[0177] First, prepare the volume-based cumulative 50% particle size D 50 It is nickel powder with a particle size of 0.31 μm.

[0178] The nickel powder was dispersed in an atmosphere containing ethanol as an alcohol for 10 seconds to obtain alcohol-adsorbed nickel powder as an alcohol-treated powder. It should be noted that the temperature of the atmosphere containing alcohol was adjusted to 25°C when the nickel powder was dispersed. In addition, the partial pressure of alcohol in the above atmosphere was set to 9.6×10 -6 atm.

[0179] (Comparative Example 3)

[0180] As alcohol, isopropyl alcohol was used instead of ethanol. When the alcohol was used for treatment, the partial pressure of alcohol in the atmosphere was 8.8×10 - 6 atm, an organic compound treated powder, that is, an alcohol treated powder was produced in the same manner as in Comparative Example 2 except that the above-mentioned conditions were met.

[0181] (Comparative Example 4)

[0182] First, prepare the volume-based cumulative 50% particle size D 50 It is nickel powder with a particle size of 0.31 μm.

[0183] The nickel powder was allowed to stand in an atmosphere containing acetic acid as a carboxylic acid, thereby obtaining a carboxylic acid-containing nickel powder as an acetic acid-adsorbed nickel powder. It should be noted that the acetic acid used was acetic acid with a purity close to 100% (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., special grade 99.7+%). Furthermore, 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 was 1.0×10 -1 atm.

[0184] (Comparative Examples 5 and 6)

[0185] Except for changing the conditions as shown in Table 2 when dispersing the nickel powder in an atmosphere containing acetic acid as a carboxylic acid, the same procedure as in Example 1 was carried out to obtain a carboxylic acid-containing nickel powder as an acetic acid-adsorbing nickel powder.

[0186] (Comparative Example 7)

[0187] Propionic acid was used as the carboxylic acid instead of acetic acid. The treatment time with the carboxylic acid was 60 minutes. The treatment temperature was 120° C. The partial pressure of the carboxylic acid in the atmosphere was 5.0×10 -1 Atm, a carboxylic acid-containing nickel powder was obtained in the same manner as in Comparative Example 4.

[0188] Together with the production conditions of the powders of the above-mentioned Examples and Comparative Examples, the peak top temperature of the peak in the mass chromatogram of the molecular ions of carboxylic acid (molecular ion of acetic acid: m / z=60, molecular ion of propionic acid: m / z=74) detected when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min in a helium atmosphere as an inert atmosphere, and the nickel particles constituting the obtained powders were measured by TG-MS. 2 The content of carboxylic acid in the surface area is summarized in Table 2. It should be noted that the EI (Electron Ionization) method was used as the ionization method of MS. In addition, Table 2 shows that the boiling point of the carboxylic acid used in each of the above Examples and Comparative Examples 4 to 7 is set to T bp [℃], at (T bp The peak top of the mass chromatogram of the molecular ion of carboxylic acid is present in the range of (T bp -50)℃ or above (T bp Whether there is a peak top in the mass chromatogram of carboxylic acid molecular ions in the range below +50)°C. In TG-MS, a STA2500 Regulus manufactured by NETZSCH was used as a TG-DTA for heating the sample, and a JMS-Q1500GC manufactured by JEOL was used as an MS for mass analysis of the substance vaporized by heating the sample. In addition, the nickel particles constituting the powder were measured per 1m 2The content of carboxylic acid in the surface area was determined by measuring (1) the carbon content in the nickel powder before the carboxylic acid adsorption treatment and (2) the carbon content in the nickel powder after the carboxylic acid adsorption treatment using a CS (carbon-sulfur) analyzer (EMIA-320V, manufactured by HORIBA). The value obtained by subtracting (1) from (2) was taken as the carbon content increased by the carboxylic acid adsorption treatment. The carbon content was determined using the ratio of this value to the carbon in the carboxylic acid and the specific surface area of ​​the nickel powder before the carboxylic acid adsorption treatment. In Table 2, acetic acid is represented by "AA," propionic acid is represented by "PA," ethanol is represented by "EtOH," and isopropyl alcohol is represented by "IPA."

[0189]

[0190] [5] Production of micro powder based on dry classification

[0191] The powders of the above-mentioned examples and comparative examples, i.e., the carboxylic acid-containing nickel powders of the above-mentioned examples and comparative examples 4 to 7, the nickel powder of comparative example 1, and the alcohol-treated powders of the above-mentioned examples 2 and 3, were fed into the reaction mixture at a rate of 10 kg per hour. Figure 1 In the dry classifier shown, the supply dispersion pressure was set to 0.6 MPa to obtain a classified powder.

[0192] Next, the powder to be classified is introduced into the classification chamber, and the temperature inside the classifier is set to 25°C and the suction air volume is set to 8.5m 3 / min, and the suction pressure is set to -35kPa, and dry classification is performed to produce fine powder.

[0193] Then, the obtained fine powder was further dry-classified in the same manner as above, that is, dry-classified twice in total to obtain the final fine powder.

[0194] [6] Evaluation

[0195] [6-1] Yield

[0196] For each of the above Examples and Comparative Examples, the weight of the powder before classification and the weight of the powder after classification, that is, the weight of the fine powder obtained by performing the classification treatment twice, were measured, and the yield was calculated using the following formula.

[0197] Yield (%) = (weight of powder after classification / weight of powder before classification) × 100

[0198] [6-2] Evaluation of particle size distribution

[0199] The particle size distribution of the nickel powder as the raw material powder and the obtained fine powder was determined for each of the above Examples and Comparative Examples by using a laser diffraction / scattering particle size distribution measuring apparatus LA-960 (manufactured by HORIBA Corporation). Based on the results, the cumulative fraction 10% value (D ) of the particle size distribution on a volume basis was determined. 10 )[μm], cumulative score 50% value (D 50 )[μm], cumulative score 90% value (D 90 )[μm].

[0200] Furthermore, according to D obtained in the above manner 10 [μm], D 50 [μm], D 90 [μm] value, calculate (D 90 -D 10 ) / D 50 .

[0201] [6-3] Evaluation of the number of coarse particles

[0202] For each of the above embodiments and comparative examples, 20 mL of ethanol was mixed as a dispersion medium in 1 g of powder after secondary classification, and an ultrasonic cleaning machine (W-113 manufactured by Honda Electronics Co., Ltd.) was used to treat it for 1 minute to prepare a dispersion. 30 μL of the prepared dispersion was weighed and dropped onto an aluminum sample stand, and the dispersion medium was dried to remove the dispersion medium, thereby preparing a sample for measurement. The above sample was magnified 10,000 times using a scanning electron microscope (SU-1510 manufactured by HITACHI HIGH-TECHNOLOGIES) and 50 fields of view were observed. The particle size was set to D of the object fine powder obtained in [6-2] above. 50 The particles with a particle size of 2.0 times or more were considered as coarse particles, and the number of coarse particles was determined.

[0203] [6-4] Smoothness of coating film

[0204] 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, 3.0 parts by weight of ethyl cellulose resin (STD100 manufactured by Dow Chemical Co., Ltd.), and 100 parts by weight of dihydroterpineol acetate were mixed and mixed at 2000 rpm for 2 minutes using a mixer (ARE-310 manufactured by THINKY Co., Ltd.) to obtain a nickel paste. The obtained nickel paste was cast to a film thickness of 10 μm, and the surface roughness Ra was measured using a micro-profile measuring instrument (ET3000i manufactured by Kosaka Laboratory).

[0205] Furthermore, for the fine powders of the above-mentioned Examples and Comparative Examples obtained in [5], the preparation of a paste, the formation of a coating film using the paste, and the measurement of surface roughness were performed in the same manner as above.

[0206] These results are summarized in Table 3. In addition, for the fine powders obtained in each of the above examples, the cumulative 50% particle size D of each fine powder on a volume basis was determined by the method described in [6-3]. 50 The number of particles having a particle size 3.0 times or more of the particle size of the present invention was determined. As a result, no such particles were contained in any of the examples.

[0207]

[0208] As can be seen from Table 3, in each of the above examples, D 50 The powder is a fine powder with a particle size range of 0.01 μm to 5.0 μm and a very small number of coarse particles. Therefore, it can be said that the carboxylic acid-containing nickel powders of each of the above examples have excellent dispersibility in the gas phase. Furthermore, the coating films formed using the pastes in each of the above examples have low surface roughness and high smoothness. Therefore, it can be said that the carboxylic acid-containing nickel powders of each of the above examples have excellent dispersibility in the paste.

[0209] Industrial Applicability

[0210] The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, wherein the surfaces of the nickel particles have carboxylic acid. When the temperature is increased from 38°C to 600°C at a heating rate of 20°C / min under an inert atmosphere, a peak is detected in the mass chromatogram of the molecular ion of the carboxylic acid by TG-MS, and the boiling point of the carboxylic acid is set as T bp [℃], the peak top of the peak exists at (T bp In the range of 100°C to 600°C, the nickel particles constituting the carboxylic acid-containing nickel powder have a thickness of 1 m 2 The content of the carboxylic acid per surface area is 155 μg to 450 μg. Therefore, a carboxylic acid-containing nickel powder can be provided that has high dispersibility in the gas phase and, when mixed with an organic solvent or the like to form a paste, has high dispersibility in the 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, wherein the method comprises a step of bringing gaseous carboxylic acid into contact with nickel powder dispersed in the gas phase. Therefore, a method for producing a carboxylic acid-containing nickel powder that has high dispersibility in the gas phase and, when mixed with an organic solvent or the like to form a paste, has high dispersibility in the paste can be provided. 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.

[0211] Explanation of symbols

[0212] 1…Grading machine

[0213] 3…housing

[0214] 4…Inlet

[0215] 5…Air nozzle

[0216] 6…Guide blades

[0217] 7…Micro powder discharge outlet

[0218] 8…coarse powder discharge outlet

[0219] 10…Grading room (grading area)

[0220] 11…Dispersed Area

Claims

1. A carboxylic acid-containing nickel powder, comprising a plurality of nickel particles, wherein the surfaces of the nickel particles have carboxylic acid, By TG-MS, when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere, a peak was detected in the mass chromatogram of the molecular ion of the carboxylic acid, and the boiling point of the carboxylic acid was set as T bp [℃], the peak top of the peak exists at (T bp In the range of above +100)℃ and below 600℃, The carboxylic acid-containing nickel powder satisfies at least one of the following (1) and (2): (1) The carboxylic acid is at least one selected from acetic acid and propionic acid, and the nickel particles constituting the carboxylic acid-containing nickel powder have a relative density of 1 m 2 The content of the carboxylic acid in the surface area is not less than 155 μg and not more than 450 μg; (2) By TG-MS, in an inert atmosphere, when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min, the bp -50)℃ or above (T bp In the range below +50)°C, there is no peak top in the mass chromatogram of the molecular ion of the carboxylic acid, and the nickel particles constituting the carboxylic acid-containing nickel powder have a mass per 1m 2 The content of the carboxylic acid per surface area is 155 μg or more and 350 μg or less.

2. The carboxylic acid-containing nickel powder according to claim 1, wherein In the above (1), by TG-MS, when the temperature is raised from 38°C to 600°C at a heating rate of 20°C / min in an inert atmosphere, the bp -50)℃ or above (T bp In the range of +50)°C or lower, there is no peak top of the peak in the mass chromatogram of the molecular ion of the carboxylic acid.

3. The carboxylic acid-containing nickel powder according to claim 1 or 2, wherein In the above (2), the boiling point of the carboxylic acid is 100°C to 270°C.

4. The carboxylic acid-containing nickel powder according to claim 1 or 2, wherein In the above (2), the molecular weight of the carboxylic acid is 55 or more and 100 or less.

5. The carboxylic acid-containing nickel powder according to claim 1 or 2, wherein In the above (2), the carboxylic acid has 2 to 9 carbon atoms.

6. The carboxylic acid-containing nickel powder according to claim 1 or 2, wherein In the above (2), the carboxylic acid is at least one selected from acetic acid and propionic acid.

7. A method for producing a carboxylic acid-containing nickel powder, the method comprising producing the carboxylic acid-containing nickel powder according to any one of claims 1 to 6, wherein: The method includes a step of bringing gaseous carboxylic acid into contact with nickel powder dispersed in a gas phase.

8. The method for producing carboxylic acid-containing nickel powder according to claim 7, wherein The nickel powder is dispersed in an atmosphere containing the carboxylic acid in a gaseous state.

9. The method for producing carboxylic acid-containing nickel powder according to claim 7, wherein The carboxylic acid in a gaseous state is supplied to the gaseous phase while the nickel powder, which is dispersed in the gas phase during production, is dispersed in the gas phase.

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