Carboxylic acid-containing nickel powder and method for producing carboxylic acid-containing nickel powder

Abstract

The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, and the surface of the aforementioned nickel particles has a carboxylic acid. The peak of the molecular ion of the aforementioned carboxylic acid is detected by TG-MS under an inert atmosphere when the temperature is increased from 38°C to 600°C at a heating rate of 20°C / min. When the boiling point of the aforementioned carboxylic acid is set to Tbp [°C], the peak of the aforementioned carboxylic acid is located in the range of (Tbp+100)°C to 600°C. The content of the aforementioned carboxylic acid per 1 m² surface area of ​​the aforementioned nickel particles constituting the carboxylic acid-containing nickel powder is 155 μg to 450 μg. This invention provides a carboxylic acid-containing nickel powder with high dispersibility in the gas phase and high dispersibility in the paste when mixed with organic solvents, etc.

Description

Technical Field

[0001] This invention relates to a nickel powder containing carboxylic acid and a method for manufacturing the nickel powder containing carboxylic acid. Prior Technology

[0002] Traditionally, conductive metal powders have been used as conductive materials for electronic components. In laminated ceramic capacitors (MCLLs), the thinning of both the ceramic layer and the internal electrode layer is rapidly developing, creating a need for internal electrode layers with thin and uniform thickness. Therefore, the conductive metal powder used as the internal electrode in MCLLs requires the following: a narrow particle size distribution, free from large particles that could potentially short-circuit by encasing the dielectric layer and contacting adjacent internal electrodes; and uniform dispersion in the paste when mixed with organic solvents to form a paste.

[0003] To date, methods for classifying powders manufactured using various methods have been employed to produce powders with desired particle size distributions. These classification methods include, for example, classifying powders based on differences in particle sedimentation rates in the gas or liquid phase, according to particle size. Classification performed in the gas phase is called dry classification, while classification performed in the liquid phase is called wet classification. Although wet classification offers superior accuracy, it requires a liquid as the dispersion medium, and furthermore, drying and pulverization are necessary after classification. Therefore, dry classification is significantly less expensive.

[0004] However, in the past, when performing this dry classification, the powder would adhere to various parts of the classifier and block the powder supply port or the inside of the piping, making it difficult to operate for a long time. Furthermore, due to the low classification accuracy, the yield rate was low.

[0005] As a method aimed at solving such problems, Patent Document 1 discloses a method of dry classifying powder by mixing powder with an additive composed of alcohols such as ethanol with a boiling point of less than 200°C, and by vaporizing the additive while the powder is dry-classified.

[0006] In another invention patent document 2, a method is disclosed in which powder is mixed with an additive consisting of an aqueous solution of alcohols such as ethanol containing 10% to 50% by mass, and the powder is dry-classified while the additive is vaporized.

[0007] Furthermore, Patent Document 3 discloses a method for dry-classifying powder composed of nickel (Ni) with an additive composed of an organic solvent such as diethylene glycol with a flash point above 80°C, while simultaneously vaporizing the additive. It also discloses a method for dry-classifying powder composed of nickel with an additive composed of water, while simultaneously vaporizing the additive.

[0008] Furthermore, in Patent Document 4, a method for dry classification of powder is disclosed by mixing powder with diethylene glycol monomethyl ether as a liquid additive. [Previous Technical Documents] [Invention 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

[0010] [The problem that the invention aims to solve]

[0011] However, the inventors of this case discovered the following problems during their research: For example, although dry classification by adsorbing additives such as ethanol onto the powder allows the classifier to operate for extended periods, the resulting powder contains a large number of coarse particles, necessitating repeated classification to reduce the number of these coarse particles. Furthermore, the following problem was also discovered: while repeated classification reduces the number of coarse particles, the time and cost involved reduce productivity, leading to a significant decrease in the yield of the obtained powder.

[0012] Furthermore, the powder obtained in the above manner is difficult to disperse evenly in a paste obtained by mixing with organic solvents, etc.

[0013] Therefore, the object of the present invention is to provide a nickel powder containing carboxylic acid that has high dispersibility in the gas phase and high dispersibility in the paste when mixed with organic solvents, etc., and a method thereof. [Technical means to solve the problem]

[0014] The above-mentioned objective is achieved by the present invention described in (1) to (9) below. (1) A nickel powder containing carboxylic acid, comprising a plurality of nickel particles, wherein the nickel particles have carboxylic acid on their surface, wherein: The peaks in the mass chromatogram of the molecular ion of the aforementioned carboxylic acid were detected by TG-MS under an inert atmosphere when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min. When the boiling point of the aforementioned carboxylic acid was set to Tbp [°C], the peak tops were found to be located in the range of (Tbp +100)°C to 600°C. The content of the aforementioned carboxylic acid per 1 m2 surface area of ​​the aforementioned nickel particles constituting the carboxylic acid-containing nickel powder is between 155 μg and 450 μg.

[0015] (2) The nickel powder containing carboxylic acid as described in (1) above, wherein when heated from 38°C to 600°C by TG-MS at a heating rate of 20°C / min under an inert atmosphere, the peak of the molecular ion of the aforementioned carboxylic acid is not present in the mass chromatography chromatogram within the range of (Tbp -50)°C to (Tbp +50)°C.

[0016] (3) Nickel powder containing carboxylic acid as described in (1) or (2) above, wherein the boiling point of the aforementioned carboxylic acid is between 100°C and 270°C.

[0017] (4) Nickel powder containing carboxylic acid as described in any of (1) to (3) above, wherein the molecular weight of the aforementioned carboxylic acid is 40 or more and 160 or less.

[0018] (5) Nickel powder containing carboxylic acid as described in any of (1) to (4) above, wherein the number of carbon atoms in the aforementioned carboxylic acid is 2 or more and 9 or less.

[0019] (6) Nickel powder containing carboxylic acid as described in any one of (3) to (5) above, wherein the aforementioned carboxylic acid is selected from at least one of the group consisting of acetic acid and propionic acid.

[0020] (7) A method for manufacturing nickel powder containing carboxylic acid, comprising the method for manufacturing nickel powder containing carboxylic acid as described in any one of (1) to (6) above, wherein the method comprises: The step of contacting gaseous carboxylic acid with nickel powder dispersed in the gas phase.

[0021] (8) The method for manufacturing nickel powder containing carboxylic acid as described in (7) above involves dispersing the aforementioned nickel powder in an atmosphere containing the aforementioned carboxylic acid in a gaseous state.

[0022] (9) The method for manufacturing nickel powder containing carboxylic acid as described in (7) above involves supplying the aforementioned carboxylic acid in a gaseous state to the nickel powder which is in a dispersed state in the gas phase during generation. [Benefits of the Invention]

[0023] According to the present invention, there is a method for manufacturing a carboxylic acid-containing nickel powder that has high dispersibility in the gas phase and high dispersibility in the paste when mixed with organic solvents, etc. Simple Explanation of the Diagram

[0024] [Figure 1] Figure 1 is a diagram showing an example of the structure of a classifier used to obtain fine powder with a very small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention. Implementation

[0025] The following is a detailed description of a preferred embodiment of the present invention. [1] Nickel powder containing carboxylic acid First, the nickel powder containing carboxylic acid of the present invention will be described.

[0026] The carboxylic acid-containing nickel powder of the present invention contains a plurality of nickel particles, and the surface of the aforementioned nickel particles has carboxylic acid. In other words, the carboxylic acid-containing nickel powder of the present invention contains adsorbed carboxylic acid nickel particles on the surface of the nickel particles that serve as parent particles.

[0027] Next, the nickel powder containing carboxylic acid of the present invention was detected by TG-MS (Thermogravimetry Mass Spectrometer) under an inert atmosphere. The peak of the molecular ion of the aforementioned carboxylic acid was detected by heating at a rate of 20°C / min from 38°C to 600°C. When the boiling point of the aforementioned carboxylic acid was set to Tbp [°C], the peak of the aforementioned carboxylic acid was in the range of (Tbp +100)°C to 600°C. The content of the aforementioned carboxylic acid per 1 m2 surface area of ​​the aforementioned nickel particles was 155 μg to 450 μg.

[0028] By satisfying this condition, a carboxylic acid-containing nickel powder with high dispersibility in the gas phase and high dispersibility in the paste when mixed with organic solvents can be provided. Furthermore, due to the excellent dispersibility of this carboxylic acid-containing nickel powder in the gas phase, coarse particles can be appropriately removed through dry classification, and fine powders with a narrow particle size distribution can be obtained smoothly and with excellent yield through dry classification. Moreover, the excellent dispersibility of the carboxylic acid-containing nickel powder in the paste results in excellent smoothness of the coating film formed using this paste.

[0029] Furthermore, the peak value of the mass chromatogram of the carboxylic acid molecular ion detected by TG-MS can be adjusted, for example, according to the adsorption morphology of the carboxylic acid on nickel particles. More specifically, the peak value of the mass chromatogram of the carboxylic acid molecular ion detected by TG-MS can be appropriately adjusted by adjusting, for example, the adsorption method, adsorption treatment conditions, and adsorption amount of the carboxylic acid on nickel particles.

[0030] In this specification, coarse particles refer to particles with a very large particle size relative to the target powder, such as the cumulative 50% particle size (D50) of the powder obtained by the grading as described above. These particles can be set to, for example, particles with a particle size of 1.5 times or more than the D50 of the target powder; particles can be set to, for example, particles with a particle size of 2.0 times or more than the D50 of the target powder; or particles can be set to, for example, particles with a particle size of 2.5 times or more than the D50 of the target powder.

[0031] Furthermore, in this specification, the cumulative 50% particle size (D50) of the volume reference, unless otherwise stated, refers to the 50% integral fraction of the volume reference particle size distribution measured using a laser particle size distribution measuring device, which can be obtained by measurement using, for example, a laser diffraction / scattering type particle size distribution measuring device LA-960 (manufactured by HORIBA).

[0032] Regarding TG-MS, for example, the NETZSCH STA2500 Regulus can be used as a TG-DTA (Thermogravimetry-Differential Thermal Analysis) instrument for heating the sample, and the JES-Q1500GC can be used as an MS (Mass Spectrometer) instrument for mass analysis of substances vaporized by heating the sample.

[0033] In addition, the content of carboxylic acid per 1 m2 surface area of ​​nickel particles constituting carboxylic acid-containing nickel powder can be determined by using a CS (carbon and sulfur) analysis device (such as the EMIA-320V manufactured by HORIBA).

[0034] As described above, the nickel powder containing carboxylic acid of the present invention exhibits a peak in a predetermined region ((Tbp +100)°C to 600°C) different from the boiling point of the carboxylic acid in the mass chromatography diagram of the molecular ion of the carboxylic acid, as analyzed by TG-MS. This is believed to be due to the adsorption of the carboxylic acid onto the nickel particles in a specific form. Although the detailed mechanism is not yet clear, the inventors speculate that, for example, the carboxylic acid is chemically adsorbed onto the nickel particles, and therefore the adsorption is more robust than in the case of physical adsorption. Consequently, a peak appears in the high-temperature region above the boiling point of the carboxylic acid (+100°C). Furthermore, it is believed that while the carboxylic acid is adsorbed onto the nickel particles in this specific form, it is also adsorbed onto the surface of the nickel particles in an appropriate proportion, thereby achieving the excellent effects described above, namely, improved dispersibility in the gas phase and enhanced dispersibility in the paste when mixed with organic solvents.

[0035] Furthermore, by ensuring that the content of carboxylic acid per 1 m² surface area of ​​nickel particles is above the aforementioned lower limit, the dispersibility of nickel powder containing carboxylic acid in the gas phase becomes excellent.

[0036] Furthermore, by ensuring that the content of carboxylic acid per 1 m² surface area of ​​nickel particles is below the aforementioned upper limit, the dispersibility of the carboxylic acid-containing nickel powder in the paste becomes excellent when it is mixed with organic solvents to form a paste.

[0037] It should be noted that, unless otherwise stated, the term "boiling point" in this specification refers to the boiling point at one atmosphere, i.e., the standard boiling point.

[0038] Furthermore, although in the case of nickel powder containing carboxylic acids containing multiple carboxylic acids, it is sufficient for at least one carboxylic acid to meet the above conditions, it is particularly preferable that the carboxylic acid system with the highest content among the multiple carboxylic acids meets the above conditions, and even more preferably that all types of carboxylic acid systems contained in the nickel powder containing carboxylic acids meet the above conditions.

[0039] As described above, although in the nickel powder containing carboxylic acid of the present invention, the peak of the molecular ion of carboxylic acid detected by analysis by TG-MS as described above only needs to be in the range of (Tbp +100)°C to 600°C, it is more preferably in the range of (Tbp +120)°C to 580°C, more preferably in the range of (Tbp +150)°C to 560°C, even more preferably in the range of (Tbp +200)°C to 540°C, and most preferably in the range of (Tbp +230)°C to 520°C. In this way, the aforementioned effects are brought into full play.

[0040] Furthermore, although in the carboxylic acid-containing nickel powder of the present invention, the content of carboxylic acid per 1 m² surface area of ​​nickel particles is only required to be 155 μg or more and 450 μg or less, more 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. Specifically, in the carboxylic acid-containing nickel powder of the present invention, the content of carboxylic acid per 1 m² surface area of ​​nickel particles 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. In this way, the aforementioned effects are brought into full play.

[0041] When the nickel powder containing carboxylic acid of the present invention is analyzed by TG-MS as described above, the peak of the mass chromatogram of the molecular ion of carboxylic acid only needs to be in the range of (Tbp +100)°C to 600°C. Although the peak of the molecular ion of carboxylic acid in the mass chromatogram may also be outside the above range, it is preferable that the peak of the molecular ion of carboxylic acid in the mass chromatogram does not exist in the range of (Tbp -50)°C to (Tbp +50)°C.

[0042] This allows for better dispersibility of carboxylic acid-containing nickel powder in the gas phase. When the carboxylic acid-containing nickel powder contains multiple carboxylic acids, it is preferable that at least one carboxylic acid satisfies the above conditions; more preferably, the carboxylic acid system with the highest content among the multiple carboxylic acids satisfies the above conditions; and even more preferably, all types of carboxylic acids contained in the carboxylic acid-containing nickel powder satisfy the above conditions.

[0043] The cumulative 50% particle size D50 of the carboxylic acid-containing nickel powder, based on volume, is preferably greater than 0.01 μm and less than 10 μm, more preferably greater than 0.03 μm and less than 2.5 μm, even more preferably greater than 0.05 μm and less than 1.2 μm, and most preferably greater than 0.10 μm and less than 0.80 μm.

[0044] [1-1] Nickel particles Nickel particles constitute the main component of nickel powder containing carboxylic acid, and are mainly composed of nickel.

[0045] Nickel particles can be composed primarily of nickel, either as an elemental metal or as nickel alloys. While nickel is the most abundant component in nickel particles, the content of components other than nickel in the nickel particles is preferably below 40% by mass, more preferably below 30% by mass, and even more preferably below 20% by mass. Specifically, the content of components other than nickel in the nickel particles is preferably below 10% by mass, more preferably below 5% by mass, and even more preferably below 1% by mass. In particular, the components other than nickel in the nickel particles are preferably only those that are unavoidable, and the content of components other than nickel in the nickel particles is preferably below 1000 ppm.

[0046] Although the shape of nickel particles is not specifically limited, various shapes such as spherical, flake, and granular can be listed, and one or more of these shapes can be selected for combination.

[0047] It should be noted that, in this specification, "spherical" refers to the shape of particles with a major axis to minor axis ratio of 2 or less. "Plate-like" refers to a shape with a major axis to minor axis ratio exceeding 2.

[0048] While not specifically limited, methods for manufacturing nickel particles include, for example, electrolysis, atomization, mechanical grinding, wet reduction, spray pyrolysis, chemical vapor deposition, and physical vapor deposition.

[0049] [1-2] Carboxylic acids Nickel powder containing carboxylic acid contains carboxylic acid in addition to the aforementioned nickel particles.

[0050] Most of the carboxylic acid system contained in the nickel powder containing carboxylic acid is adsorbed on the surface of the nickel particles, which serve as the parent particles. In other words, most of the carboxylic acid system contained in the nickel powder containing carboxylic acid is contained as a component of the adsorbed carboxylic acid nickel particles.

[0051] As a form of adsorption of nickel particles by carboxylic acids, it can be either physical adsorption or chemical adsorption.

[0052] As a carboxylic acid, it is not specifically limited to any compound that has a carboxyl group.

[0053] The boiling point of the carboxylic acid is preferably between 100°C and 270°C, more preferably between 105°C and 250°C, even more preferably between 110°C and 200°C, and most preferably between 115°C and 170°C.

[0054] This allows for better dispersibility of carboxylic acid-containing nickel powder in the gas phase, and further improves its dispersibility when mixed with organic solvents to form a paste. Moreover, in manufacturing the carboxylic acid-containing nickel powder, the carboxylic acid used as a raw material can be appropriately treated in a liquid state, improving workability. Furthermore, when the carboxylic acid is adsorbed onto the nickel powder in a vaporized state, it can be adsorbed onto the nickel powder in a more favorable state.

[0055] In addition, the carboxylic acid system is preferably monocarboxylic acid. This allows for better dispersibility of nickel powder containing carboxylic acid in the gas phase, and further enhances the dispersibility of the nickel powder containing carboxylic acid in the paste when it is mixed with organic solvents to form a paste.

[0056] The molecular weight of the carboxylic acid is preferably between 40 and 160, more preferably between 50 and 120, and even more preferably between 55 and 100.

[0057] This allows for better dispersibility of nickel powder containing carboxylic acid in the gas phase, and further enhances the dispersibility of the nickel powder containing carboxylic acid in the paste when it is mixed with organic solvents to form a paste.

[0058] The carbon number of the carboxylic acid is preferably 2 to 9, more preferably 2 to 7, and even more preferably 2 to 5.

[0059] This allows for better dispersibility of nickel powder containing carboxylic acid in the gas phase, and further enhances the dispersibility of the nickel powder containing carboxylic acid in the paste when it is mixed with organic solvents to form a paste.

[0060] While 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, and one or more of these can be selected for combination, it is preferable to select at least one from the group consisting of acetic acid and propionic acid, and more preferably acetic acid.

[0061] This allows for better dispersibility of nickel powder containing carboxylic acid in the gas phase, and further enhances the dispersibility of the nickel powder containing carboxylic acid in the paste when it is mixed with organic solvents to form a paste.

[0062] [1-3] Uses of nickel powder containing carboxylic acid While the applications of the carboxylic acid-containing nickel powder of the present invention are not particularly limited, it can be used as a conductive powder, and more preferably as a conductive powder for conductive pastes. Due to its high dispersibility, its dispersibility in pastes is also easily increased. Furthermore, the carboxylic acid-containing nickel powder of the present invention, after being fed to the classification step described later, particularly after being fed to the dry classification step, is preferably used as a conductive powder, and more preferably as a conductive powder for conductive pastes. Moreover, because the carboxylic acid-containing nickel powder of the present invention has high flowability and excellent operability, it can be easily processed for various applications.

[0063] By feeding the carboxylic acid-containing nickel powder of the present invention into the dry classification step described later, micropowders with small average particle size, narrow particle size distribution, and almost no coarse particles can be successfully obtained. Because such micropowders have a narrower particle size distribution than the carboxylic acid-containing nickel powder of the present invention before classification, they can form a coating with superior smoothness. Therefore, when the aforementioned micropowders are used in internal electrodes, a uniform electrode layer can be formed. Furthermore, because they contain almost no coarse particles, short circuits caused by conductive powder particles contacting both sides of the internal electrode can be appropriately prevented. Therefore, even in applications requiring such high reliability, satisfactory performance can be obtained. Thus, when the aforementioned micropowders are 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 aforementioned effects can be even more significantly achieved.

[0064] Conductive powder can also be used, for example, as a conductive paste made by mixing glass frit and an organic vehicle to form conductive parts of electronic components.

[0065] [2] Method for manufacturing nickel powder containing carboxylic acid Next, the method for manufacturing the carboxylic acid-containing nickel powder of the present invention will be described.

[0066] The method for manufacturing nickel powder containing carboxylic acid of the present invention is the same as the method for manufacturing nickel powder containing carboxylic acid of the present invention described above, which includes the step of contacting a carboxylic acid in a gaseous state with a plurality of nickel particles dispersed in a gas phase to form nickel powder.

[0067] This provides a method for manufacturing carboxylic acid-containing nickel powder, as described above, which exhibits high dispersibility in the gas phase and, when mixed with organic solvents to form a paste, also exhibits high dispersibility in the paste. Furthermore, compared to the case where gaseous carboxylic acid is contacted with nickel powder in a static state, the former method results in a lower concentration of carboxylic acid, allowing the carboxylic acid to be adsorbed onto the surface of the nickel particles in an overwhelmingly short time. Therefore, it is advantageous in terms of reducing carboxylic acid consumption or shortening the time required for adsorption.

[0068] Although the method for manufacturing nickel powder containing carboxylic acid of the present invention only requires the step of contacting nickel powder dispersed in the gas phase with carboxylic acid in a gaseous state, it is preferable, for example, to disperse nickel powder containing an aggregate of multiple nickel particles in an atmosphere containing carboxylic acid in a gaseous state.

[0069] Furthermore, in the method for manufacturing nickel powder containing carboxylic acid of the present invention, the step of contacting the nickel powder with the carboxylic acid in a gaseous state can also be performed by supplying the aforementioned carboxylic acid in a gaseous state to the nickel powder while the nickel powder is in a dispersed state in the gaseous state during generation.

[0070] Therefore, since carboxylic acid gas can be introduced into the nickel powder before it is recovered after nickel powder is generated in the gas phase, the carboxylic acid gas can come into contact with the nickel powder with a better dispersion state, thus making the adsorption of carboxylic acid more uniform.

[0071] Methods for generating nickel powder that is dispersed in the gas phase during generation include, for example, gas-phase methods such as chemical vapor deposition and physical vapor deposition, or atomization and spray pyrolysis. In particular, when generating the aforementioned nickel powder using gas-phase methods or spray pyrolysis, it is easier to adjust the particle size of the aforementioned nickel powder to better conditions.

[0072] Furthermore, in the method for manufacturing nickel powder containing carboxylic acid of the present invention, it is only necessary to have a step of contacting the gaseous carboxylic acid with nickel powder dispersed in the gas phase, and it is not limited to contacting the gaseous carboxylic acid with freshly generated nickel powder, or, for example, contacting the gaseous carboxylic acid with nickel powder that has been recycled once.

[0073] [3] Method for manufacturing micro powder containing carboxylic acid nickel powder using the present invention Next, a method for manufacturing micro powder using the aforementioned nickel powder containing carboxylic acid of the present invention will be described.

[0074] The method for manufacturing micro powder of this embodiment is a method for manufacturing micro powder with a cumulative 50% particle size D50 on a volume basis in the range of 0.01 μm to 5.0 μm. It includes a step of generating classified powder by dispersing nickel powder containing carboxylic acid with D50 greater than 0.01 μm and less than 10 μm in the gas phase to obtain classified powder; and a dry classification step of dry classification of the aforementioned classified powder.

[0075] This provides a method for manufacturing micropowders that can produce micropowders with a very small number of coarse particles and a cumulative 50% particle size D50 on a volume basis of 0.01 μm to 5.0 μm with high productivity.

[0076] The superior performance achieved is attributed to the following factors: Compared to dry classification using additives such as ethanol adsorbed onto the powder, using nickel powder containing carboxylic acid, where carboxylic acid is adsorbed onto nickel particles under predetermined conditions, improves the powder's dispersibility in the gas phase and enhances classification accuracy. This significantly reduces the number of coarse particles in the manufactured fine powder. Furthermore, it reduces the number of classification steps, thereby increasing productivity.

[0077] Furthermore, the micro-powder obtained in the above manner exhibits particularly excellent dispersibility in the paste when mixed with organic solvents, etc. Therefore, the smoothness of the coating film formed using this paste becomes excellent.

[0078] Furthermore, by using the carboxylic acid-containing nickel powder of the present invention, the powder's flowability is improved, and the powder's adhesion within the classifier is reduced, thereby increasing the yield. Also, by reducing adhesion within the classifier, the powder supply port or piping of the classifier becomes less prone to blockage, thus extending the classifier's operating time and improving productivity.

[0079] Furthermore, in this embodiment, since carboxylic acid-containing nickel powder that has been pre-adsorbed onto nickel particles under predetermined conditions is used, it is beneficial to simplify and miniaturize the structure of the apparatus for manufacturing micro-powders. Also, because carboxylic acid-containing nickel powder that has been pre-adsorbed onto nickel particles under predetermined conditions is used, compared to adding nickel powder without adsorbed carboxylic acid to the classifier, the former has higher powder flowability and is less prone to adhesion within the classifier, resulting in smoother powder movement within the classifier.

[0080] In this specification, grading refers to the process of grouping relatively larger particles into one group (in other words, coarse powder) and relatively smaller particles into another group (in other words, fine powder) based on their size. Specifically, in this specification, fine powder refers to a group of particles whose cumulative 50% particle size D50 on a volume basis is between 0.01 μm and 5.0 μm, while coarse powder refers to a group of particles with a D50 greater than that of fine powder.

[0081] [3-1] Classifier Figure 1 is a diagram showing an example of the structure of a classifier used to obtain a fine powder with a very small number of coarse particles using the carboxylic acid-containing nickel powder of the present invention. Furthermore, in the following explanation, the upper side of Figure 1 will be referred to as "upper" and the lower side as "lower".

[0082] The classifier 1 is an airflow classifier that uses centrifugal force acting on powder to classify it, and it has a housing 3 for forming the classification chamber 10.

[0083] Upstream of the classification chamber (classification area) 10, there is a dispersion area 11 for dispersing the carboxylic acid-containing nickel powder before classification. The classification chamber 10 is the area for classifying the dispersed carboxylic acid-containing nickel powder.

[0084] Furthermore, the classifier 1 has: an inlet 4 for introducing nickel powder containing carboxylic acid 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 allowing secondary air to flow into the classification chamber 10 to form a swirling airflow in the classification chamber 10; a fine powder outlet 7 opening at the upper center of the classification chamber 10; and a coarse powder outlet 8 opening along the lower periphery of the classification chamber 10.

[0085] Next, a method for dispersing and classifying nickel powder containing carboxylic acid using this classifier 1 will be described.

[0086] Nickel powder containing carboxylic acid is introduced into dispersion zone 11 through inlet 4. The nickel powder containing carboxylic acid is dispersed by a dispersing force applied by primary air injected into dispersion zone 11. Then, the dispersed nickel powder is introduced into classification chamber 10.

[0087] In the classification chamber 10, secondary air is introduced into the classification chamber 10 through the guide vane 6, causing the airflow to vortex within the classification chamber 10 and exhausting from the upper center of the classification chamber 10. Through the outward centrifugal force acting through this airflow vortex and the flow of gas moving towards the center, the nickel powder containing carboxylic acid in the solid-gas mixture is separated into coarse powder and fine powder.

[0088] That is, the coarse powder is moved to the radially outer side within the classification chamber 10 by the outward centrifugal force generated by the vortex of the airflow, and is recovered from the coarse powder outlet 8 at the lower periphery of the classification chamber 10. On the other hand, the fine powder is moved to the radially inner side within the classification chamber 10 by the flow of gas moving towards the center, and is recovered from the fine powder outlet 7 at the upper center of the classification chamber 10.

[0089] The micro powder outlet 7 is connected to a suction pump (not shown), and the micro powder is discharged and recycled together with the air (exhaust) in the classification chamber 10.

[0090] The powder generation 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. That is, the nickel powder containing carboxylic acid that is dispersed in the dispersion region 11, in other words, the nickel powder containing carboxylic acid that is introduced into the classification chamber 10 is the classified powder as referred to in this specification.

[0091] Furthermore, although the above description provides examples of airflow classifiers that utilize centrifugal force generated by vortex airflow for classification, the classification method of the classifier is not specifically limited. For example, it could utilize centrifugal force generated by rotor rotation, gravity, or inertial force for classification.

[0092] Furthermore, in this invention, the powder generation step and the dry classification step are not limited to using the same apparatus; they can also be performed using separate apparatuses. That is, after dispersing the nickel powder containing carboxylic acid using a disperser to obtain the powder to be classified, a dry classifier can be used to classify the powder.

[0093] [3-2] Steps for generating graded powder In the step of generating the graded powder, the graded powder is obtained by dispersing nickel powder containing carboxylic acid in the gas phase.

[0094] Although the speed at which the nickel powder containing carboxylic acid is supplied to the classifier, i.e., in the classifier 1 shown in Figure 1, the speed at which the nickel powder containing carboxylic acid is supplied from the inlet 4 to the dispersion area 11 also depends on the size (capacity) of the classifier, it is preferably between 1 kg / hour and 20 kg / hour, more preferably between 3 kg / hour and 15 kg / hour, and even more preferably between 5 kg / hour and 12 kg / hour.

[0095] This improves both the dispersibility of nickel powder containing carboxylic acid and the productivity of micronized powders.

[0096] The dispersion pressure supplied during dispersion, that is, the pressure of the dispersion air injected from the air nozzle 5 into the dispersion area 11 in the classifier 1 shown in Figure 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.

[0097] This improves both the dispersibility of nickel powder containing carboxylic acid and the productivity of micronized powders.

[0098] [3-2] Dry classification steps In the dry classification step, the powder to be classified obtained in the powder to be classified generation step is dry classified.

[0099] Because the powder being classified is properly dispersed in the gas phase, the classification accuracy of the dry classification process is improved. This results in a significantly reduced number of coarse particles in the produced fine powder. Furthermore, by improving classification accuracy, fewer classification steps are required, thus increasing productivity.

[0100] Furthermore, by increasing the flowability of the powder being classified, the adhesion of the powder within the classifier is reduced, thereby improving the yield. Also, the reduced adhesion within the classifier makes it less prone to clogging at the powder supply inlet or inside the piping, thus extending the classifier's operating time and improving productivity.

[0101] This enables the production of fine powders with a very small number of coarse particles with high productivity.

[0102] Although the gas phase temperature for the dry classification step is not specifically limited, it is preferably above 60°C and below 300°C, more preferably above 100°C and below 250°C, and even more preferably above 150°C and below 200°C.

[0103] This method effectively prevents particle deformation or deterioration of particle components caused by heat. Furthermore, the increased airflow velocity enhances centrifugal force and prevents water vapor from adhering to the particles, thus further improving classification accuracy. It also improves productivity. Moreover, it significantly reduces the number of coarse particles in the fine powder.

[0104] The air volume during the dry grading step, that is, the air volume generated by the suction pump connected to the micro powder outlet 7 in the classifier 1 shown in Figure 1, is not specifically limited, but is preferably between 5.0 m3 / min and 30 m3 / min, more preferably between 6.0 m3 / min and 20 m3 / min, and even more preferably between 7.0 m3 / min and 9.0 m3 / min. This allows for more effective classification of the powder being classified.

[0105] The suction pressure for dry classification, that is, in the classifier 1 shown in Figure 1, the suction pressure generated by the suction pump connected to the micro powder outlet 7, is not particularly limited, but is preferably above -60 kPa and below -5 kPa, more preferably above -50 kPa and below -10 kPa, and even more preferably above -40 kPa and below -15 kPa. This allows for more appropriate classification of the powder being classified.

[0106] By dry classification of the powder to be classified, the powder is separated into fine powder and coarse powder. The powder to be classified is, for example, fine powder with a cumulative 50% particle size D50 on a volume basis ranging from 0.01 μm to 5.0 μm, and coarse powder with a D50 greater than that of the fine powder. The fine powder is then recovered as the aforementioned fine powder.

[0107] The above method can be used to manufacture micro powders with a cumulative 50% particle size D50 on a volume basis ranging from 0.01 μm to 5.0 μm.

[0108] The number of coarse particles in the micro-powder produced in this way is extremely small. Furthermore, by adsorbing carboxylic acids in a better state on the micro-powder, secondary agglomeration is also prevented.

[0109] Furthermore, according to the above method, the number of classification steps can be reduced due to the improved classification accuracy. Additionally, the adhesion of the powder being classified within the classifier is reduced, thereby improving yield. Moreover, by reducing adhesion within the classifier, the powder supply port and piping of the classifier become less prone to clogging, thus extending the classifier's operating time and improving productivity.

[0110] Furthermore, although the dry classification step can be performed only once, it can also be repeated multiple times. This allows for further improvement in classification accuracy.

[0111] Although the yield of fine powder in the dry classification step is not specifically limited, it is preferably above 80%, more preferably above 81%, even more preferably above 82%, and most preferably above 83%. This makes the effectiveness of the present invention even more significant.

[0112] Furthermore, in this specification, the yield of the micronized powder in the dry classification step is a value obtained by using the following formula based on the weight of the powder before classification (i.e., the weight of the nickel powder containing carboxylic acid) and the weight of the powder after classification (i.e., the weight of the micronized powder): Yield (%) = (Weight of powder after grading / Weight of powder before grading) × 100

[0113] Although the micro powder produced by the method of the present invention described above only needs to have a cumulative 50% particle size D50 on a volume basis in the range of 0.01 μm to 5.0 μm, the D50 of the micro powder is preferably 0.03 μm to 2.0 μm, more preferably 0.05 μm to 1.0 μm, and even more preferably 0.10 μm to 0.60 μm.

[0114] This allows for the production of fine powders with a more desirable particle size distribution. Furthermore, in conventional techniques, when D50 is within this range, coarse particles tend to become a problem, and the adverse effects caused by coarse particles are particularly likely to occur. In contrast, in this invention, even when D50 is within this range, the aforementioned problems can be prevented more effectively. That is, when the D50 of the fine powder is within the aforementioned range, the effectiveness of this invention is more significantly realized.

[0115] Regarding the micro powder produced by the method of the present invention described above, when the volume fraction of the particle size distribution measured by the laser particle size distribution measuring device is set to 10% as D10 [μm], 50% as D50 [μm], and 90% as D90 [μm], the value of (D90 - D10) / D50 is preferably 0.30 to 0.90, more preferably 0.35 to 0.80, and even more preferably 0.40 to 0.75.

[0116] (D90 - D10) / D50 is an index representing the uniformity of particle size distribution. The smaller the value of (D90 - D10) / D50, the narrower the particle size distribution, which means that the particle size is more uniform.

[0117] This results in a more uniform particle size for the micro powder, making it suitable for various applications.

[0118] Furthermore, in the method for manufacturing micro powder, the number of coarse particles obtained by the following measurement is preferably less than 30, more preferably less than 25, and even more preferably less than 20.

[0119] This allows for a more effective prevention of various problems caused by coarse particles in the micro powder.

[0120] The number of coarse particles mentioned above can be determined, for example, in the following manner. First, 1.0 g of micronized powder was mixed with 20 mL of ethanol and treated with an ultrasonic cleaner (e.g., Honda Electric Corporation, W-113) for 1 minute to prepare a dispersion. 30 μL of this dispersion was weighed and dropped onto an aluminum sample stage, then dried to remove the dispersion medium, thus preparing the sample for analysis. The sample was observed using a scanning electron microscope (SEM) (e.g., Hitachi High-Tech Corporation, SU-1510) at 10,000x magnification with 50 visual fields. The total number of particles with a diameter greater than 1.5 times the cumulative 50% particle size D50 (by volume) of the micronized powder was determined, and this value was taken as the number of coarse particles.

[0121] While the above description pertains to preferred embodiments of the present invention, the present invention is not limited thereto.

[0122] For example, the apparatus used in the manufacturing method of micro powders is not limited to those described in the foregoing embodiments. [Example]

[0123] Although specific embodiments are listed below to illustrate the invention in more detail, the invention is not limited to the embodiments described below. Furthermore, in the following description, unless otherwise specified, temperature and humidity conditions are applied at room temperature (25°C) and 50% relative humidity. Also, for various measurement conditions, unless otherwise specified, the values ​​are also taken at room temperature (25°C) and 50% relative humidity. Moreover, the 10% integral fraction D10, 50% integral fraction D50, and 90% integral fraction D90 of the volume fraction of nickel powder and micro-powder containing carboxylic acid are obtained by measurement using a laser diffraction / scattering type particle size distribution measuring device LA-960 (manufactured by HORIBA). In addition, the conditions for the carboxylic acids used in the various embodiments described below are summarized in Table 1.

[0124] [Table 1]

[0125] [4] Manufacturing of nickel powder containing carboxylic acid (Example 1) First, nickel powder with a cumulative 50% particle size D50 of 0.31 μm on a volume basis was prepared. The nickel powder was dispersed in an atmosphere containing acetic acid (a carboxylic acid) for 10 seconds to obtain a nickel powder containing carboxylic acid that adsorbed nickel acetate powder. Furthermore, the acetic acid used was of near 100% purity (manufactured by FUJIFILM Wako Pure Chemical Corporation, premium grade 99.7+%). Additionally, the temperature of the acetic acid atmosphere was adjusted to 100°C during the dispersion of the nickel powder. Furthermore, the partial pressure of acetic acid in the aforementioned atmosphere was 6.6 × 10⁻⁵ atm.

[0126] (Example 2) Except that the partial pressure of acetic acid in the atmosphere containing acetic acid (which is a carboxylic acid) was changed to 6.6 × 10⁻⁶ atm when the nickel powder was dispersed in the atmosphere, the carboxylic acid-containing nickel powder that adsorbed nickel acetate powder was obtained in the same manner as in Example 1 above.

[0127] (Example 3) Except for using propionic acid instead of acetic acid as the carboxylic acid and changing the dispersion conditions in an atmosphere containing carboxylic acid to those shown in Table 2, nickel powder containing carboxylic acid was obtained in the same manner as in Example 1 above.

[0128] (Example 4) First, nickel acetate tetrahydrate (NAT) powder was prepared. This NAT powder was sprayed and heated to 1500°C in the gas phase to obtain nickel powder dispersed in the gas phase. The temperature of the gas phase was adjusted to 300°C while the nickel powder was dispersed. Acetic acid, a carboxylic acid, was supplied to the gas phase containing the dispersed nickel powder and treated for 10 seconds to obtain nickel powder containing carboxylic acid adsorbed with nickel acetate powder. Acetic acid with a purity close to 100% (manufactured by FUJIFILM Wako Pure Chemical Corporation, premium grade 99.7+%) was used. Furthermore, the partial pressure of acetic acid in the gas phase during the treatment with acetic acid as a carboxylic acid was set to 6.6 × 10⁻⁵ atm. In addition, the cumulative 50% particle size D50 on a volume basis, measured when recovering the nickel powder before supplying acetic acid as a carboxylic acid, was 0.31 μm.

[0129] (Example 5) Except for changing the temperature of the gas phase when supplying carboxylic acid to 500°C and changing the partial pressure of acetic acid in the gas phase when treating acetic acid as carboxylic acid to 1.3 × 10⁻⁵ atm, nickel powder containing carboxylic acid adsorbed with nickel acetate powder was obtained in the same manner as in Example 4 above.

[0130] (Example 6) Except that 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, nickel powder containing carboxylic acid that adsorbed nickel acetate powder was obtained in the same manner as in Example 5 above.

[0131] (Comparative Example 1) The powder used in this comparative example is the nickel powder used as the raw material powder in Example 1 above, without being treated with carboxylic acid. That is, the powder in this comparative example is nickel powder that has not been treated with carboxylic acid.

[0132] (Comparative Example 2) First, nickel powder with a cumulative 50% particle size D50 of 0.31 μm on a volume basis was prepared. The nickel powder was dispersed in an atmosphere containing ethanol (an alcohol) for 10 seconds to obtain adsorbed alcohol-treated nickel powder. The temperature of the alcohol-containing atmosphere during nickel powder dispersion was adjusted to 25°C. Furthermore, the partial pressure of the alcohol in the aforementioned atmosphere was set to 9.6 × 10⁻⁶ atm.

[0133] (Comparative Example 3) Except that isopropanol was used instead of ethanol as the alcohol and the partial pressure of the alcohol in the atmosphere during treatment with the alcohol was set to 8.8 × 10⁻⁶ atm, the alcohol-treated powder was manufactured in the same manner as in Comparative Example 2 above.

[0134] (Comparative Example 4) First, nickel powder with a cumulative 50% particle size D50 of 0.31 μm on a volume basis was prepared. The nickel powder was placed in an atmosphere containing acetic acid, which is a carboxylic acid, thereby obtaining a nickel powder containing carboxylic acid that adsorbs nickel acetate powder. Furthermore, the acetic acid used was of near 100% purity (manufactured by FUJIFILM Wako Pure Chemical Corporation, premium grade 99.7+%). The treatment time with acetic acid was set to 30 minutes, the treatment temperature was set to 50°C, and the partial pressure of acetic acid in the atmosphere during treatment was set to 1.0 × 10⁻¹ atm.

[0135] (Comparative Examples 5 and 6) Except for changing the conditions for dispersing nickel powder in an atmosphere containing acetic acid, which is a carboxylic acid, to those shown in Table 2, the carboxylic acid-containing nickel powder that adsorbed nickel acetate powder was obtained in the same manner as in Example 1 above.

[0136] (Comparative Example 7) Except that propionic acid was used instead of acetic acid as the carboxylic acid, the processing time through the carboxylic acid was set to 60 minutes, the processing temperature during the processing through the carboxylic acid was set to 120°C, and the partial pressure of the carboxylic acid in the atmosphere during the processing through the carboxylic acid was set to 5.0 × 10⁻¹ atm, the nickel powder containing carboxylic acid was obtained in the same manner as in Comparative Example 4 above.

[0137] The manufacturing conditions of the powders in the aforementioned examples and comparative examples, along with the peak temperatures of the molecular ions of carboxylic acids (m / z = 60 for acetic acid and m / z = 74 for propionic acid) in the mass chromatography (GC-MS) obtained by detecting these powders under an inert helium atmosphere at a heating rate of 20°C / min from 38°C to 600°C, and the content of carboxylic acids per 1 m² surface area of ​​the nickel particles constituting the obtained powders, are summarized and presented in Table 2. Furthermore, the ionization method used in the MS was EI (Electron Ionization). Table 2 also shows the presence or absence of peaks in the mass chromatography of the molecular ions of carboxylic acids in the range of (Tbp +100)°C to 600°C when the boiling point of the carboxylic acids used in the aforementioned examples and Comparative Examples 4 to 7 is set to Tbp [°C]. It also shows the presence or absence of peaks in the mass chromatography of the molecular ions of carboxylic acids in the range of (Tbp -50)°C to (Tbp +50)°C. Regarding TG-MS, a NETZSCH STA2500 Regulus was used as the TG-DTA for heating the sample, and a JMS-Q1500GC was used as the MS for mass analysis of substances vaporized by heating the sample. Furthermore, the content of carboxylic acid per 1 m² surface area of ​​the nickel particles constituting the powder was determined using a CS (carbon and sulfur) analyzer (HORIBA, EMIA-320V) to measure (1) the amount of carbon in the nickel powder before the carboxylic acid adsorption treatment, and (2) the amount of carbon in the nickel powder after the carboxylic acid adsorption treatment. The value obtained by subtracting (1) from (2) was taken as the amount of carbon increased by the carboxylic acid adsorption treatment. This value, the proportion of carbon in the carboxylic acid, and the specific surface area of ​​the nickel powder before the carboxylic acid adsorption treatment were used to calculate the amount of carbon increased by the carboxylic acid adsorption treatment. In addition, in Table 2, acetic acid is represented as "AA", propionic acid as "PA", ethanol as "EtOH", and isopropanol as "IPA".

[0138] [Table 2]

[0139] [5] Manufacturing of micro powders by dry classification 10 kg of powder from each of the aforementioned examples and comparative examples, i.e., 10 kg of nickel powder containing carboxylic acid from each of the aforementioned examples and comparative examples 4 to 7, nickel powder from comparative example 1, and alcohol-treated powder from examples 2 and 3, are fed into the dry classifier shown in FIG1 per hour, and the supply dispersion pressure is set to 0.6 MPa to obtain the classified powder.

[0140] Next, the powder to be classified is introduced into the classification chamber, and the temperature inside the classifier is set to 25°C, the air volume is set to 8.5 m3 / min, and the suction pressure is set to -35 kPa, so as to produce micro powder by dry classification.

[0141] Secondly, the obtained micro powder was further subjected to dry classification in the same manner as described above, that is, a total of two dry classifications were performed, and the final micro powder was obtained.

[0142] [6] Evaluation [6-1] Yield The powder weight before and after grading in the aforementioned embodiments and comparative examples, i.e., the weight of the micro powder obtained by performing two grading processes, was measured, and the yield was calculated according to the following formula. Yield (%) = (Weight of powder after grading / Weight of powder before grading) × 100

[0143] [6-2] Evaluation of particle size distribution Based on measurements using a laser diffraction / scattering type particle size distribution measuring device LA-960 (manufactured by HORIBA), the particle size distribution of the nickel powder and the obtained micro powder of the raw material powder were obtained for each of the aforementioned examples and comparative examples. The volume fraction values ​​of the particle size distribution, specifically the 10% value (D10) [μm], 50% value (D50) [μm], and 90% value (D90) [μm], were then calculated.

[0144] Then, using the values ​​of D10 [μm], D50 [μm], and D90 [μm] obtained in the above manner, calculate (D90 - D10) / D50.

[0145] [6-3] Evaluation of coarse particle number For each of the aforementioned embodiments and comparative examples, 20 mL of ethanol as the dispersion medium was mixed with 1 g of the secondary fractionated powder, and the mixture was treated with an ultrasonic cleaner (Honda Electronics Co., Ltd., W-113) for 1 minute to prepare a dispersion. 30 μL of the prepared dispersion was weighed and dropped onto an aluminum sample stage, then dried to remove the dispersion medium, thereby preparing a sample for measurement. The sample was observed using a scanning electron microscope (Hitachi High-Tech Corporation, SU-1510) at 10,000x magnification with 50 fields of view. Using the particle size obtained in the above [6-2] method, particles with a D50 greater than 2.0 times that of the target micro-powder were considered coarse particles, and the number of coarse particles was determined.

[0146] [6-4] Smoothness of the coating film The powders obtained in the aforementioned examples and comparative examples [4], namely 100 parts by weight of the powder before grading, 3.0 parts by weight of ethyl cellulose resin (Dow Chemical Company, STD100), and 100 parts by weight of dihydroterpineol acetate, were mixed and stirred at 2000 rpm for 2 minutes using a hybrid mixer (THINKY Company, ARE-310) to obtain nickel paste. The obtained nickel paste was cast to a film thickness of 10 μm, and the surface roughness Ra was measured using a fine shape measuring instrument (Kosaka Research Institute, ET3000i).

[0147] Furthermore, the micro powders obtained in the aforementioned embodiments and comparative examples [5] were prepared in the same manner as described above, and the formation of the coating film using the paste and the determination of its surface roughness were also carried out.

[0148] These results are summarized and shown in Table 3. In addition, when the number of particles with a cumulative 50% particle size D50 of 3.0 or more based on volume was determined by the method shown in [6-3] for the micro powders obtained in the foregoing embodiments, no such particles were found in any of the embodiments.

[0149] [Table 3]

[0150] As can be clearly seen from Table 3, the aforementioned embodiments successfully produced fine powders with a D50 range of 0.01 μm to 5.0 μm and a very small number of coarse particles with high yield. Therefore, the carboxylic acid-containing nickel powders of the aforementioned embodiments exhibit excellent dispersibility in the gas phase. Furthermore, in the aforementioned embodiments, the coatings formed using the paste exhibit low surface roughness and high smoothness. Therefore, the carboxylic acid-containing nickel powders of the aforementioned embodiments exhibit excellent dispersibility in the paste. [Industry availability]

[0151] The carboxylic acid-containing nickel powder of the present invention comprises a plurality of nickel particles, and the surface of the aforementioned nickel particles has a carboxylic acid. The peak of the molecular ion of the aforementioned carboxylic acid is detected by TG-MS under an inert atmosphere when the temperature is increased from 38°C to 600°C at a heating rate of 20°C / min. When the boiling point of the aforementioned carboxylic acid is set to Tbp [°C], the peak of the aforementioned carboxylic acid is located in the range of (Tbp + 100)°C to 600°C, and the content of the aforementioned carboxylic acid per 1 m² surface area of ​​the aforementioned nickel particles constituting the carboxylic acid-containing nickel powder is 155 μg to 450 μg. This provides a carboxylic acid-containing nickel powder with high dispersibility in the gas phase and high dispersibility in the paste when mixed with organic solvents, etc. Furthermore, the manufacturing method of the carboxylic acid-containing nickel powder of the present invention includes a step of contacting the gaseous carboxylic acid with nickel powder dispersed in the gas phase. This provides a method for manufacturing a carboxylic acid-containing nickel powder that exhibits high dispersibility in the gas phase and, when mixed with organic solvents to form a paste, also exhibits high dispersibility in the paste. Therefore, the carboxylic acid-containing nickel powder and its manufacturing method of the present invention are industrially applicable.

[0152] 1: Grading machine 3: Shell 4: Inlet 5: Air nozzle 6: Guide vane 7: Micronized powder outlet 8: Coarse powder discharge outlet 10: Classification Room (Classification Area) 11: Dispersed Areas

Claims

1. A nickel powder containing carboxylic acid, comprising a plurality of nickel particles, wherein the nickel particles have carboxylic acid on their surface, wherein: The peak of the molecular ion of the aforementioned carboxylic acid was detected by TG-MS under an inert atmosphere when the temperature was increased from 38°C to 600°C at a heating rate of 20°C / min. When the boiling point of the aforementioned carboxylic acid was set to Tbp [°C], the peak of the aforementioned carboxylic acid was located in the range of (Tbp+100)°C to 600°C. The content of the aforementioned carboxylic acid per 1 m2 surface area of ​​the aforementioned nickel particles constituting the nickel powder containing carboxylic acid was 155 μg to 450 μg. The aforementioned nickel powder containing carboxylic acid satisfied at least one of the following (1), (2) and (3): (1) The number of carbon atoms of the aforementioned carboxylic acid was 2 to 3. (2) When the temperature is increased from 38°C to 600°C by TG-MS at a heating rate of 20°C / min under an inert atmosphere, the peak of the molecular ion of the aforementioned carboxylic acid is not present in the mass chromatography spectrum within the range of (Tbp-50)°C to (Tbp+50)°C; (3) The content of the aforementioned carboxylic acid per 1m2 surface area of ​​the aforementioned nickel particles constituting the nickel powder containing carboxylic acid is between 155 μg and 350 μg.

2. The nickel powder containing carboxylic acid as described in claim 1, wherein, When the temperature is increased from 38°C to 600°C by TG-MS at a heating rate of 20°C / min under an inert atmosphere, the peak of the molecular ion of the aforementioned carboxylic acid is absent in the mass chromatography spectrum within the range of (Tbp-50)°C to (Tbp+50)°C.

3. The nickel powder containing carboxylic acid as described in claim 1 or claim 2, wherein, The boiling points of the aforementioned carboxylic acids are between 100°C and 270°C.

4. The nickel powder containing carboxylic acid as described in claim 1 or claim 2, wherein, The molecular weight of the aforementioned carboxylic acids is between 55 and 100.

5. The nickel powder containing carboxylic acid as described in claim 1 or claim 2, wherein, The aforementioned carboxylic acids have a carbon number of 2 to 9.

6. The nickel powder containing carboxylic acid as described in claim 1 or claim 2, wherein, The aforementioned carboxylic acids are selected from at least one of the groups consisting of acetic acid and propionic acid.

7. A method for manufacturing nickel powder containing carboxylic acid, comprising the method for manufacturing nickel powder containing carboxylic acid as described in any one of claims 1 to 6, wherein the method comprises: a step of contacting nickel powder dispersed in a gaseous state with a carboxylic acid in a gaseous state.

8. The method for manufacturing nickel powder containing carboxylic acid as described in claim 7 involves dispersing the aforementioned nickel powder in an atmosphere containing the aforementioned carboxylic acid in a gaseous state.

9. The method for manufacturing nickel powder containing carboxylic acid as described in claim 7, wherein the nickel powder is in a dispersed state in the gas phase during generation, and the aforementioned carboxylic acid in a gaseous state is supplied in the gas phase while the nickel powder is in a dispersed state in the gas phase.

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