JP5969354B2 - Method for producing dispersible nickel fine particle slurry - Google Patents

Description

  The present invention relates to a nickel fine particle slurry having improved dispersibility, and more particularly to a dispersible nickel fine particle slurry that can be suitably used for, for example, a conductive paste for forming an internal electrode of a multilayer ceramic capacitor (MLCC).

  Since the metal fine particles have physical and chemical characteristics different from those of bulk metals, various materials such as electrode materials such as conductive pastes and transparent conductive films, high-density recording materials, catalyst materials, and ink-jet ink materials are used. It is used for industrial materials. In recent years, with the miniaturization of electronic devices, multilayer ceramic capacitor electrodes have been made thin and multilayer, and with this, metal fine particles such as nickel fine particles used for the material of the electrode layer are also about several tens to several hundreds of nanometers. The micronization is progressing.

  As described above, the metal fine particles used for industrial materials are required to have a particle diameter as small as, for example, less than 150 nm, a uniform particle diameter, and excellent dispersibility. However, with the progress of micronization, there is a problem that the metal microparticles easily aggregate due to an increase in surface energy.

  As a dispersant used for dispersing metal fine particles, for example, an anionic dispersant (for example, Patent Document 1) containing a fatty acid containing polyvalent carboxylic acid, an unsaturated fatty acid, or the like, or a polymeric ionic dispersant (for example, a patent) Document 2), phosphoric ester compounds (for example, Patent Document 3), and ethylene oxide adducts of carboxylic acids such as polyoxyethylene lauryl ether carboxylic acid (for example, Patent Document 4) are known. Although these dispersants can achieve a certain degree of dispersion effect, with the progress of micronization, it is not possible to sufficiently suppress aggregation of metal fine particles of about several tens to several hundreds of nanometers. It is. Accordingly, there is a demand for a dispersant exhibiting high dispersibility corresponding to further micronization of metal fine particles.

JP 2001-066951 A JP 2010-135180 A JP 1998-092226 A Japanese Patent No. 4020764

  An object of the present invention is to provide a dispersible nickel fine particle slurry containing metallic nickel fine particles in a dispersed state.

The method for producing the dispersible nickel fine particle slurry of the present invention includes the following steps A to C;
A) preparing a slurry containing raw metal nickel fine particles and an organic solvent at least partially coated with a primary amine and elemental sulfur or a sulfur-containing compound;
B) A phthalocyanine-modified metal that is partially coated with the phthalocyanine compound by adding a phthalocyanine compound to the slurry and replacing at least a portion of the primary amine with the phthalocyanine compound on the surface of the raw material nickel metal fine particles Obtaining nickel fine particles,
C) adding polyoxyethylene alkyl ether carboxylic acid or a salt thereof to the phthalocyanine-modified metal nickel fine particles to form a carboxylate with the phthalocyanine compound;
It has.

  In the method for producing a dispersible nickel fine particle slurry of the present invention, the primary amine covering the surface of the raw metal nickel fine particles may be an aliphatic primary amine.

  In the method for producing a dispersible nickel fine particle slurry of the present invention, the raw metal nickel fine particles may be crushed in advance in an organic solvent using a wet pulverizer.

In the method for producing a dispersible nickel fine particle slurry of the present invention, the raw metal nickel fine particles are
Next steps I and II;
I) a step of heating a mixture of nickel carboxylate and primary amine to a temperature in the range of 100 ° C. to 165 ° C. to obtain a complexing reaction solution;
II) A step of heating the complexing reaction solution to a temperature of 170 ° C. or higher by microwave irradiation to reduce nickel ions in the complexing reaction solution to obtain metallic nickel fine particles coated with a primary amine.
III) A step of obtaining raw material nickel fine particles by mixing elemental sulfur or a sulfur-containing compound with metallic nickel fine particles coated with a primary amine,
It may be prepared by a method comprising

  The phthalocyanine compound used in the dispersible nickel fine particle slurry of the present invention easily substitutes at least a part of the primary amine on the surface of the metal nickel fine particles. And the carboxylate formed by the reaction of this phthalocyanine compound and polyoxyethylene alkyl ether carboxylic acid or its salt has a strong anti-aggregation effect on the metallic nickel fine particles, so an excellent dispersion effect even in a small amount Can be expected. Therefore, according to the method for producing a dispersible nickel fine particle slurry of the present invention, for example, even for fine metal nickel fine particles having a particle size of 150 nm or less, agglomeration is suppressed, and a metal having a sharp particle size distribution in which single particles are dispersed. An aggregate of nickel fine particles can be obtained.

The method for producing dispersible nickel fine particles according to the present embodiment includes the following steps A to C;
A) preparing a slurry containing raw metal nickel fine particles and an organic solvent at least partially coated with a primary amine and elemental sulfur or a sulfur-containing compound;
B) A phthalocyanine compound is added to the slurry, and at least a part of the primary amine and the phthalocyanine compound are substituted on the surface of the raw metal nickel fine particles to obtain phthalocyanine-modified metal nickel fine particles coated with the phthalocyanine compound. Process,
C) adding polyoxyethylene alkyl ether carboxylic acid or a salt thereof to the phthalocyanine-modified metal nickel fine particles to form a carboxylate with the phthalocyanine compound;
It has.

Process A:
The raw metal nickel fine particles are obtained by at least partially covering the surface of the metal nickel fine particles with a primary amine and a sulfur element or sulfur-containing compound. Here, the term “coating” refers to a state in which primary amine and elemental sulfur or sulfur-containing compound are physically adsorbed or adhered to at least a part of the surface of the metal nickel fine particle, or chemically applied to at least a part of the surface of the metal nickel fine particle. Includes combined state.

  The raw metal nickel fine particles can be produced by a known method. For example, a method of mixing a primary amine and elemental sulfur or a sulfur-containing compound with metallic nickel fine particles obtained by a vapor phase method or a liquid phase method, or a primary amine with a nickel salt that is a precursor of metallic nickel fine particles. Examples thereof include a method in which after mixing, metal nickel fine particles coated with a primary amine are obtained by heating, and elemental sulfur or a sulfur-containing compound is mixed with the metal nickel fine particles.

Since the gas phase method tends to be expensive to produce compared to the liquid phase method, it is advantageous to apply the liquid phase method. Among the liquid phase methods, as a method for easily producing raw material metal nickel fine particles having a narrow particle size distribution in a short time, the following steps I to III;
I) a step of heating a mixture of nickel carboxylate and primary amine to a temperature in the range of 100 ° C. to 165 ° C. to obtain a complexing reaction solution;
II) A step of heating the complexing reaction solution to a temperature of 170 ° C. or higher by microwave irradiation to reduce nickel ions in the complexing reaction solution to obtain metallic nickel fine particles coated with a primary amine. ,
III) A step of obtaining raw material nickel fine particles by mixing elemental sulfur or a sulfur-containing compound with metallic nickel fine particles coated with a primary amine,
It is preferable to provide. Here, in Step II, it is preferable to obtain the metal nickel fine particles coated with the primary amine in the state of a slurry of an organic solvent (hereinafter sometimes referred to as “first organic solvent”).

The kind of nickel salt is not particularly limited, and examples thereof include nickel hydroxide, nickel chloride, nickel nitrate, nickel sulfate, nickel carbonate, nickel carboxylate, Ni (acac) ₂ (β-diketonato complex), nickel stearate and the like. However, among these, nickel chloride or nickel carboxylate is preferable, and it is advantageous to use nickel carboxylate having a relatively low dissociation temperature (decomposition temperature) in the reduction process. The nickel carboxylate may be used alone or in combination with other nickel salts.

  The primary amine is not particularly limited as long as it can form a complex with nickel ions, and can be a solid or liquid at room temperature. Here, room temperature means 20 ° C. ± 15 ° C. The primary amine that is liquid at room temperature also functions as an organic solvent for forming the nickel complex. Even if it is a primary organic amine that is solid at room temperature, there is no particular problem as long as it is liquid by heating or can be dissolved using an organic solvent.

  The primary amine may be an aromatic primary amine, but an aliphatic primary amine is preferred from the viewpoint of easy nickel complex formation in the reaction solution. The aliphatic primary amine can control the particle diameter of the metal nickel fine particles produced, for example, by adjusting the length of the carbon chain. From the viewpoint of controlling the particle diameter of the metal nickel fine particles, the aliphatic primary amine is preferably selected from those having about 6 to 20 carbon atoms. The larger the number of carbons, the smaller the particle diameter of the obtained metal nickel fine particles. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine.

  The primary amine is preferably liquid at room temperature from the viewpoint of ease of processing operation in the washing step of separating the solid component of the metallic nickel fine particles produced by the reduction reaction from the solvent or the unreacted primary amine. Further, the primary amine is preferably one having a boiling point higher than the reduction temperature from the viewpoint of easy reaction control when the nickel complex is reduced to obtain metallic nickel fine particles. The amount of the primary amine is preferably 2 mol or more, more preferably 2.2 mol or more, relative to 1 mol of the nickel salt. When the amount of the primary amine is less than 2 mol, it is difficult to control the particle diameter of the obtained metal nickel fine particles, and the particle diameter tends to vary. The upper limit of the amount of primary amine is not particularly limited, but is preferably 20 mol or less from the viewpoint of productivity, for example.

  The primary amine can proceed as a first organic solvent, but in order to proceed the reaction in a homogeneous solution more efficiently, an organic solvent other than the primary amine is newly added. Also good. The organic solvent that can be used is not particularly limited as long as it does not inhibit the complex formation between the primary amine and the nickel ion. For example, the organic solvent having 4 to 30 carbon atoms, 7 to 30 carbon atoms, and the like. A saturated or unsaturated hydrocarbon organic solvent, an alcohol organic solvent having 8 to 18 carbon atoms, or the like can be used. Moreover, from the viewpoint of enabling use even under heating conditions by microwave irradiation, it is preferable to select an organic solvent having a boiling point of 170 ° C. or higher, more preferably in the range of 200 to 300 ° C. It is better to choose one. Specific examples of such an organic solvent include tetraethylene glycol and n-octyl ether.

  Although the complex formation reaction can proceed even at room temperature, in order to perform a sufficient and more efficient complex formation reaction, for example, the reaction is performed by heating within a range of 100 ° C. to 165 ° C. This heating can be appropriately set from the viewpoint of separating from the subsequent heat reduction process by microwave irradiation of the nickel complex (or nickel ions) and completing the complex formation reaction. The heating method is not particularly limited, and may be heating by a heat medium such as an oil bath or heating by microwave irradiation.

  In Step II, the complexing reaction solution obtained by the complexation reaction between the nickel salt and the primary amine is heated by microwave irradiation to reduce the nickel ions in the complexing reaction solution, thereby reducing the first metal nickel fine particles. A slurry of the organic solvent is obtained. The temperature for heating by microwave irradiation is preferably 170 ° C. or higher, more preferably 180 ° C. or higher, from the viewpoint of suppressing variation in the shape of the obtained metal nickel fine particles. The upper limit of the heating temperature is not particularly limited, but is preferably set to 270 ° C. or less, for example, from the viewpoint of efficiently performing the treatment. In addition, the use wavelength of a microwave is not specifically limited, For example, it is 2.45 GHz.

  Heating of the complexing reaction solution by microwave irradiation enables uniform heating in the reaction solution and can directly apply energy to the medium, so that rapid heating can be performed. As a result, the entire reaction solution can be made uniform at a desired temperature, and the processes of reduction, nucleation, and nucleation of the nickel complex (or nickel ions) occur simultaneously in the entire solution. Narrow monodisperse particles can be easily produced in a short time. In particular, it is suitable for producing metallic nickel fine particles having an average particle diameter in the range of 20 to 150 nm.

  In order to generate metallic nickel fine particles having a uniform particle size, the heating temperature of the complexing reaction liquid generation step is adjusted within a specific range, and is surely lower than the heating temperature by microwave irradiation. Easily produce particles with a uniform particle size and shape. For example, if the heating temperature is too high in the complexing reaction solution generation process, the formation of nickel complex and the reduction reaction to nickel (zero valence) proceed simultaneously, and different types of metal are generated. There is a possibility that generation of fine particles may be difficult. In addition, if the heating temperature by microwave irradiation is too low, the reduction reaction rate to nickel (zero valence) becomes slow and the generation of nuclei is reduced, so that not only the particles become larger but also the size of the particles becomes uneven, This is also not preferable from the viewpoint of the yield of nickel fine particles.

  In Step III, the metal nickel fine particles obtained as described above are made into a slurry state, and sulfur powder or a sulfur-containing compound is added. In this case, from the viewpoint of controlling the carbon element contained in the metal nickel fine particles, it is preferable to use, as the sulfur-containing compound, a sulfur-containing organic compound having a functional group containing a sulfur atom that enables chemical bonding with a nickel atom. The sulfur powder or the sulfur-containing compound may be added in the state of a metal nickel fine particle slurry following the reduction reaction by microwave irradiation of the reaction solution, or from the metal nickel fine particle slurry obtained by the reduction reaction, once the metal After the nickel fine particles are isolated, the metal nickel fine particles may be dispersed in a liquid to form a slurry and then added. From the viewpoint of simplification of the process, it is preferable to add the sulfur powder or the sulfur-containing compound in the state of a metal nickel fine particle slurry following the reduction reaction by microwave irradiation of the reaction solution.

  The sulfur-containing organic compound is an organic compound containing a sulfur atom in the molecule. Examples of such an organic compound include thiol compounds, sulfide compounds, thiophene compounds, sulfoxide compounds, sulfone compounds, and thioketone compounds. Examples thereof include compounds and sulfuran compounds. Among these compounds, thiol compounds (containing mercapto groups) and sulfide compounds (containing sulfide groups or disulfide groups) have high reactivity due to the high activity of sulfur atoms. It can be coated with a Ni—S chemical bond, and for example, surface oxidation of the metal nickel fine particles can be suppressed even by rapid heating of the metal nickel fine particles, which is preferable. In order to improve the dispersibility of the metallic nickel fine particles, an aliphatic sulfur-containing organic compound is preferable.

  As the sulfur-containing organic compound containing a mercapto group, an aliphatic thiol compound having a hydrocarbon group is preferable in order to improve the dispersibility of the dispersible nickel fine particles, and more preferably in the range of 1 to 18 carbon atoms. Aliphatic thiol compounds are preferred.

The sulfur-containing organic compound containing a sulfide group is preferably an aliphatic methyl sulfide compound having a hydrocarbon group, more preferably within the range of 2 to 18 carbon atoms, in order to improve the dispersibility of the dispersible nickel fine particles. Some aliphatic methyl sulfide compounds are preferred. Such an aliphatic methyl sulfide compound is represented by R ₁ —S—CH ₃ . Here, R ₁ is a monovalent substituent selected from an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an alkenyl group, and an alkynyl group.

The sulfur-containing organic compound containing a disulfide group is preferably an aliphatic disulfide compound having a hydrocarbon group, more preferably in the range of 2 to 40 carbon atoms, in order to improve the dispersibility of the dispersible nickel fine particles. Aliphatic disulfide compounds are preferred. Such an aliphatic disulfide compound is represented by R ₁ —S—S—R ₁ ′. Here, R ₁ and R ₁ ′ are monovalent substituents independently selected from an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an alkenyl group, and an alkynyl group.

  Preferable specific examples of the aliphatic sulfur-containing organic compound include, for example, methylthiol, ethylthiol, propylthiol, butylthiol, heptylthiol, hexylthiol, octylthiol, nonylthiol, decylthiol (decanethiol), undecylthiol , Dodecylthiol (dodecanethiol), tetradecylthiol (tetradecanethiol), hexadecanethiol, octadecylthiol, tert-dodecylmercaptan, cyclohexylthiol, benzylthiol, ethylphenylthiol, 2-mercaptomethyl-1,3-dithiolane, 2- Mercaptomethyl-1,4-dithiane, 1-mercapto-2,3-epithiopropane, 1-mercaptomethylthio-2,3-epithiopropane, 1-mercapto Tylthio-2,3-epithiopropane, 3-mercaptothietane, 2-mercaptothietane, 3-mercaptomethylthiothietane, 2-mercaptomethylthiothietane, 3-mercaptoethylthiothietane, 2-mercaptoethylthiothi Monovalent aliphatic thiol compounds such as ethane, 2-mercaptoethanol, 3-mercapto-1,2-propanediol, 1,1-methanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol, 1, 2-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanedithiol, 1,10-decanedithiol, 1,2,3-propanetrithiol, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol, 2,2-dimethylpropane 1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol, 2-methylcyclohexane-2,3-dithiol, 1,1-bis (mercaptomethyl) cyclohexane, bis-thiomalate (2-mercaptoethyl ester) ), 2,3-dimercapto-1-propanol (2-mercaptoacetate), 2,3-dimercapto-1-propanol (3-mercaptopropionate), diethylene glycol bis (2-mercaptoacetate), diethylene glycol bis (3- Mercaptopropionate), 1,2-dimercaptopropyl methyl ether, 2,3-dimercaptopropyl methyl ether, 2,2-bis (mercaptomethyl) -1,3-propanedithiol, bis (2-mercaptoethyl) Ether, ethylene glycol Rubis (2-mercaptoacetate), ethylene glycol bis (3-mercaptopropionate), trimethylolpropane bis (2-mercaptoacetate), trimethylolpropane bis (3-mercaptopropionate), pentaerythritol tetrakis (2- Mercaptoacetate), pentaerythritol tetrakis (3-mercaptopropionate), tetrakis (mercaptomethyl) methane, 1,1,1,1-tetrakis (mercaptomethyl) methane, bis (mercaptomethyl) sulfide, bis (mercaptomethyl) Disulfide, bis (mercaptoethyl) sulfide, bis (mercaptoethyl) disulfide, bis (mercaptopropyl) sulfide, bis (mercaptomethylthio) methane, bis (2-mercapto) Tilthio) methane, bis (3-mercaptopropylthio) methane, 1,2-bis (mercaptomethylthio) ethane, 1,2-bis (2-mercaptoethylthio) ethane, 1,2-bis (3-mercaptopropyl) Ethane, 1,3-bis (mercaptomethylthio) propane, 1,3-bis (2-mercaptoethylthio) propane, 1,3-bis (3-mercaptopropylthio) propane, 1,2,3-tris (mercapto) Methylthio) propane, 1,2,3-tris (2-mercaptoethylthio) propane, 1,2,3-tris (3-mercaptopropylthio) propane, 1,2-bis [(2-mercaptoethyl) thio] -3-mercaptopropane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, tetrakis ( Mercaptomethylthiomethyl) methane, tetrakis (2-mercaptoethylthiomethyl) methane, tetrakis (3-mercaptopropylthiomethyl) methane, bis (2,3-dimercaptopropyl) sulfide, bis (1,3-dimercaptopropyl) Sulfide, 2,5-dimercapto-1,4-dithiane, 2,5-bis (mercaptomethyl) -1,4-dithiane, 2,5-dimercaptomethyl-2,5-dimethyl-1,4-dithiane, Bis (mercaptomethyl) disulfide, bis (mercaptoethyl) disulfide, bis (mercapto) Propyl) disulfide, 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, hydroxymethyl sulfide bis (2-mercaptoacetate), hydroxymethyl sulfide bis (3-mercaptopropionate), hydroxyethyl sulfide bis ( 2-mercaptoacetate), hydroxyethyl sulfide bis (3-mercaptopropionate), hydroxypropyl sulfide bis (2-mercaptoacetate), hydroxypropyl sulfide bis (3-mercaptopropionate), hydroxymethyl disulfide bis (2- Mercaptoacetate), hydroxymethyl disulfide bis (3-mercaptopropionate), hydroxyethyl disulfide bis (2-mercaptoacetate), hydroxy Ethyl disulfide bis (3-mercaptopropionate), hydroxypropyl disulfide bis (2-mercaptoacetate), hydroxypropyl disulfide bis (3-mercaptopropionate), 2-mercaptoethyl ether bis (2-mercaptoacetate), 2 -Mercaptoethyl ether bis (3-mercaptopropionate), 1,4-dithian-2,5-diol bis (2-mercaptoacetate), 1,4-dithian-2,5-diol bis (3-mercaptopropionate) ), Thiodiglycolic acid bis (2-mercaptoethyl ester), thiodipropionic acid bis (2-mercaptoethyl ester), 4,4-thiodibutyric acid bis (2-mercaptoethyl ester), dithiodiglycolic acid bis (2 -Merca Toethyl ester), dithiodipropionic acid bis (2-mercaptoethyl ester), 4,4-dithiodibutyric acid bis (2-mercaptoethyl ester), thiodiglycolic acid bis (2,3-dimercaptopropyl ester), Aliphatic acids such as bis (2,3-dimercaptopropyl ester) thiodipropionate, bis (2,3-dimercaptopropyl ester) dithioglycolate, bis (2,3-dimercaptopropyl ester) dithiodipropionate Examples include polythiol compounds, aliphatic sulfides such as dodecylmethyl sulfide and n-decyl sulfide, and aliphatic disulfides such as decane disulfide. In addition, these are not specifically limited, It can use individually or in combination of 2 or more types.

  The addition amount of the sulfur-containing organic compound is determined in consideration of the surface area of the metal nickel fine particles. As the sulfur element with respect to 100 parts by mass of the nickel element of the metal nickel salt at the time of preparation, for example, 0.01 to 3 What is necessary is just to make it become in the range of the mass part, Preferably it is in the range of 0.05-1 mass part.

  By adding the sulfur-containing organic compound, raw material nickel metal fine particles coated with the sulfur-containing organic compound can be obtained even at room temperature, but preferably in the range of 100 ° C. to 300 ° C. in order to carry out reliably and more efficiently. Then, heat treatment is performed within a range of 1 minute to 1 hour. This heating method is not particularly limited, and may be heating by a heat medium such as an oil bath or heating by microwave irradiation, and is not particularly limited. As described above, the sulfur powder or the sulfur-containing compound is preferably added to the metal nickel fine particle slurry following the reduction reaction by microwave irradiation of the complexing reaction liquid in Step II, and the formation of nickel sulfide is facilitated. From this viewpoint, it is more preferable to add the slurry in a heated state immediately after the reduction reaction.

  From the viewpoint of forming a Ni—S chemical bond by a sulfur-containing organic compound, the raw material nickel metal fine particles used in the present embodiment preferably control the density of the hydroxide or oxide film to a medium level. . More specifically, the content of metallic nickel measured by X-ray photoelectron spectroscopy (hereinafter sometimes abbreviated as “XPS”) for identifying metallic nickel with X-rays transmitted through the coating is preferably 25. It is preferable to be within a range of ˜75 atm%, more preferably within a range of 40 to 60 atm%. XPS can identify and quantify nickel atoms resulting from metallic nickel, nickel hydroxide and nickel oxide, but there is a correlation between the density of the hydroxide or oxide coating and the content of metallic nickel. The ratio of metallic nickel is high when the density of the coating is low, and the ratio of metallic nickel is low when the density is high.

  The raw material metallic nickel fine particles of the present embodiment are those in which the surface of the metallic nickel fine particles is coated with a sulfur-containing compound or sulfur element. The oxygen element is contained in the range of 0.5 to 2.0% by mass and the oxygen element is contained in the range of 0.1 to 2.5% by mass. Content) is in the range of 0.2 to 1.0.

  In the raw metal nickel fine particles of the present embodiment, the metal nickel fine particles contain nickel element. The content of nickel element may be appropriately selected according to the purpose of use, but the amount of nickel element is preferably 90 parts by mass or more, more preferably 95 parts by mass or more with respect to 100 parts by mass of the raw metal nickel fine particles. It is good to do. Examples of metals other than nickel include titanium, cobalt, copper, chromium, manganese, iron, aluminum, sodium, potassium, magnesium, zirconium, tin, tungsten, molybdenum, vanadium, barium, calcium, and strontium. Examples include base metals such as silicon, aluminum and phosphorus, noble metals such as gold, silver, platinum, palladium, iridium, osmium, ruthenium, rhodium, rhenium, neodymium, niobium, holonium, dysprodium, yttrium, and rare earth metals. Or it may contain 2 or more types, and may contain elements other than metal elements, such as hydrogen, carbon, nitrogen, sulfur, and boron, and these alloys may be sufficient.

  A preferable covering form of the sulfur-containing compound or the elemental sulfur in the raw metal nickel fine particles is preferably in a state where the sulfur-containing compound or the elemental sulfur is chemically bonded to at least a part of the surface of the metal nickel fine particles. Further, it is particularly preferable to have a nickel sulfide coating layer without covering at least a part and the whole of the surface of the nickel metal fine particles. The coating layer of nickel sulfide can suppress the surface activity of the metal nickel fine particles, and can suppress low-temperature combustion or thermal decomposition of the binder in the binder removal step. The state of the coating of the sulfur-containing compound or sulfur element can be confirmed by, for example, a transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), or the like. Moreover, the thickness of the coating layer is not particularly limited, but is preferably about 2 to 20 nm, for example.

  From another viewpoint, the amount of elemental sulfur in the raw metal nickel fine particles (including those contained in the state of sulfur-containing compounds) is within the range of 0.01 to 0.5 mass% with respect to the raw metal nickel fine particles, Preferably it is good to contain in the range of 0.05-0.5 mass%. If the elemental sulfur is less than 0.01% by mass, the effect of suppressing oxidation of the raw material nickel metal fine particles during heating in an oxygen atmosphere is reduced, and if it exceeds 0.5% by mass, hydrogen sulfide gas is generated in a reducing atmosphere. It causes the accompanying swelling of the particles.

  There is no restriction | limiting in particular in the particle diameter of raw material nickel metal microparticles | fine-particles, For example, according to the use purpose, it selects from the range of 1-200 nm. For example, metal nickel fine particles having a particle diameter of 150 nm or less are preferable, and metal nickel fine particles having a particle size of 100 nm or less are more preferable. From another viewpoint, the average particle diameter of the raw metal nickel fine particles is preferably in the range of 10 to 150 nm, more preferably in the range of 20 to 120 nm.

  When the raw material nickel fine particles obtained as described above are in a slurry state, for example, after standing and separating, removing the supernatant liquid, washing with an appropriate solvent, and drying, the raw material nickel metal Fine particles are obtained. Next, the obtained raw material nickel metal fine particles are made into a slurry state with a second organic solvent. The slurry can be produced, for example, by mixing the raw metal nickel fine particles and the second organic solvent and stirring them. When the raw material nickel metal fine particles are in the state of a slurry of the first organic solvent, they are replaced with the second organic solvent. When the first organic solvent is a primary amine, it can be used as it is as the second organic solvent.

Process B:
In step B, the phthalocyanine compound is added to the slurry obtained in step A. The phthalocyanine compound may be added in the form of a slurry in which the first organic solvent is replaced with the second organic solvent following the reduction reaction by microwave irradiation of the reaction solution, or the metallic nickel obtained by the reduction reaction After the metallic nickel fine particles are once isolated from the fine particle slurry, the metallic nickel fine particles may be dispersed again in the second organic solvent to form a slurry, and then added.

  The second organic solvent is not particularly limited as long as it can dissolve the phthalocyanine compound, and specific examples thereof include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, hexane, heptane, and the like. , Decane, octane, heptane, cyclohexane, methylcyclohexane, ethylcyclohexane, etc., aliphatic hydrocarbons, ethyl acetate, butyl acetate, etc., esters, α-terpineol, butyl carbitol, etc., long chain alcohols, long chain alcohols And an ester of carboxylic acid. Moreover, as long as the phthalocyanine compound does not aggregate, in addition to the above organic solvent, an organic solvent in which a part of the phthalocyanine compound is miscible with water, for example, a ketone system such as acetone, methyl ethyl ketone, and methyl isobutyl ketone can be used.

  As the phthalocyanine compound used in this embodiment, a phthalocyanine compound represented by the following general formula can be used.

［上記式中、Ｘ_１〜Ｘ_８は、それぞれ独立に、水素原子、あるいは直鎖もしくは枝分かれのアルキル基、環状アルキル基、アシル基、複素環残基、ニトロ基、シアノ基、スルホン酸基、カルボン酸基、−ＯＲ_１、−ＳＲ_２、−ＳＯ_２Ｒ_１、−ＣＯＯＲ_２、−ＮＲ_１Ｒ_２、−ＣＯＮＲ_１Ｒ_２、−ＳＯ_２Ｒ_１Ｒ_２、−ＮＨＣＯＲ_１、−Ｎ＝Ｎ−Ｒ_１、又は−Ｎ＝ＣＨＲ_１を表す。ここで、Ｒ_１及びＲ_２は、それぞれ独立に、水素原子、あるいは直鎖状もしくは枝分かれ状のアルキル基、環状アルキル基、アシル基、又はポリエーテル基を表し、また、Ｒ_１とＲ_２で４〜７員環を形成していてもよく、その際、ヘテロ原子を含む複素環であってもよい。Ｍは、Ｈ_２又は２価の遷移金属元素を表す。］

[In the above formula, X _{1 to} X ₈ are each independently a hydrogen atom or a linear or branched alkyl group, a cyclic alkyl group, an acyl group, a heterocyclic residue, a nitro group, a cyano group, a sulfonic acid group, a carboxylic acid _{group, -OR 1, -SR 2, -SO} 2 R 1, -COOR 2, -NR 1 R 2, -CONR 1 R 2, -SO 2 R 1 R 2, -NHCOR 1, -N = N -R _1, or an -N = CHR _1. Here, R ₁ and R ₂ each independently represent a hydrogen atom, or a linear or branched alkyl group, a cyclic alkyl group, an acyl group, or a polyether group, and R ₁ and R ₂ A 4- to 7-membered ring may be formed, and in this case, a heterocycle containing a heteroatom may be used. M represents H ₂ or a divalent transition metal element. ]

In the above general formula, as the divalent transition metal element represented by M, for example, Cu, Ni and the like are preferable. Among the phthalocyanine compounds represented by the above general formula, phthalocyanine in which X _{1 to} X ₈ are hydrogen atoms and M is H ₂ is most preferable.

  As the phthalocyanine compound, for example, commercially available products such as Solsperse 5000 (ammonium phthalocyanine sulfonate) manufactured by Japan Lubrizol Corporation can be used.

  The phthalocyanine compound substitutes at least a part of the primary amine on the surface of the raw material nickel metal fine particles. By replacing at least a part of the primary amine and the phthalocyanine compound, phthalocyanine-modified metallic nickel fine particles can be obtained. Since the phthalocyanine compound used in the present embodiment has the property of being easily bonded to a metal, it can be easily substituted with at least a portion of the primary amine immobilized on the surface of the metal nickel fine particles, and the metal nickel fine particles can be coated. It is done. However, when no primary amine is present on the surface of the metal nickel fine particles, even if a phthalocyanine compound is added, substitution with the primary amine does not easily occur, and an aggregation suppressing action and a dispersion effect cannot be obtained.

  In addition, the polyoxyethylene alkyl ether carboxylic acid or salt thereof used in Step C exhibits excellent dispersibility, but is directly applied to the raw material nickel metal fine particles at least partially coated with a primary amine and a sulfur element or sulfur-containing compound. However, a sufficient dispersion effect cannot be obtained. The reason for this is that polyoxyethylene alkyl ether carboxylic acid or a salt thereof has a low affinity with raw material nickel metal fine particles, so even if it is directly applied to raw metal nickel fine particles, the amount of adhesion to the surface is limited. It is thought that. However, by modifying the raw metal nickel fine particles with a phthalocyanine compound in advance, a sufficient amount of polyoxyethylene alkyl ether carboxylic acid or a salt thereof having a strong aggregation inhibitory action is attached to the metal nickel fine particles via phthalocyanine. And an excellent dispersion effect can be expected. In addition, although it is known that a phthalocyanine compound has an aggregation inhibitory action with respect to metal nickel fine particles, in this Embodiment, polyoxyethylene alkyl ether carboxylic acid or its salt used at the process C is made into primary amine and It functions as a binder for adhering to the raw material nickel metal fine particles at least partially coated with elemental sulfur or a sulfur-containing compound.

  The phthalocyanine compounds used in this embodiment can be used alone or in combination of two or more. Moreover, it can also be used in combination with the dispersing agent which consists of another compound in the range which does not impair the effect of invention.

  The addition amount of the phthalocyanine compound used in the present embodiment is in the range of 0.01 to 10 parts by mass, preferably in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the metallic nickel fine particles. When the addition amount is less than the above lower limit, the dispersibility tends to decrease, and when it exceeds the upper limit, aggregation tends to occur.

  In the present embodiment, the application method of the phthalocyanine compound is not particularly limited. For example, a) After the raw metal nickel fine particles coated with primary amine and sulfur element or sulfur-containing compound are synthesized by a liquid phase method, A method of adding a predetermined amount of a phthalocyanine compound in a phase, b) raw material metal nickel fine particles coated with a primary amine and a sulfur element or a sulfur-containing compound using a dispersing machine such as a high-pressure homogenizer, an ultrasonic homogenizer, or a bead mill disperser Various methods such as a method of mechanically crushing and adding and dispersing a predetermined amount of a phthalocyanine compound before or after the crushing are exemplified.

  Metal nickel coated with primary amine and elemental sulfur or sulfur-containing compound from the viewpoint of improving the specific surface area of the metal nickel fine particles and more effectively exposing the primary amine coated on the surface of the metal nickel fine particles to the surface It is preferable to disintegrate the fine particles mechanically. In addition, from the viewpoint of changing the primary amine coating state present on the surface of the metal nickel fine particles as much as possible before and after crushing, the metal nickel fine particles coated with the primary amine and sulfur element or sulfur-containing compound are used. It is preferable to crush in advance in a slurry state with a third organic solvent.

  The slurry with the third organic solvent can be prepared, for example, by statically separating the raw material nickel metal fine particle slurry, removing the supernatant, washing with an appropriate solvent, and then adding the third organic solvent. it can. As the third organic solvent, for example, an ether organic solvent having 4 to 30 carbon atoms, a saturated or unsaturated hydrocarbon organic solvent having 7 to 30 carbon atoms, an alcohol solvent having 3 to 18 carbon atoms, or the like is used. Can do. The third organic solvent is preferably an alcoholic organic solvent. Preferable specific examples of such alcohol organic solvents include methanol, 1-octanol, isopropanol, tetraethylene glycol and the like. Although the primary amine used for the complex formation reaction can be used in place of the third organic solvent, reaggregation of the metallic nickel fine particles is likely to occur.

Process C:
In step C, polyoxyethylene alkyl ether carboxylic acid or a salt thereof is added to phthalocyanine-modified metallic nickel fine particles to form a carboxylate with the phthalocyanine compound.

Examples of the polyoxyethylene alkyl ether carboxylic acid or salt thereof used in Step C include the following general formula:
_{R 1 -O- (CH 2 CH 2} O) n-CH 2 -COOH
[Wherein R ₁ represents a linear or branched alkyl group having 12 to 26 carbon atoms, and n represents an average addition mole number of an oxyethylene group, and is within a range of 3 to 90] is there. ]
And a salt thereof. Further, as the polyoxyethylene alkyl ether carboxylic acid, those in which R ₁ contains a lauryl group having 12 carbon atoms and a mystil group having 14 carbon atoms are preferable in the above general formula. Examples of polyoxyethylene alkyl ether carboxylic acid salts include polyoxyethylene lauryl ether acetic acid.

  Examples of the polyoxyethylene alkyl ether carboxylic acid or a salt thereof include TYPOL SOFT (registered trademark) ECA-390, TYPOL SOFT (registered trademark) ECA-490, TYPOL SOFT (registered trademark) ECA-1090. (Nagoko Chemicals Co., Ltd.), Nikko Chemicals' NIKKOL AKYPO RLM45 (trade name) (Laureth-5 carboxylic acid), NIKKOL AKYPO RLM100 (trade name) (Laureth-11 carboxylic acid), NIKOL ECT -3 (trade name) (trideceth-4 carboxylic acid), NIKKOL ECT-7 (trade name) (trideceth-8 carboxylic acid) and the like can also be used.

  The polyoxyethylene alkyl ether carboxylic acid or a salt thereof used in the present embodiment has a property of being easily bonded to a phthalocyanine compound, so that it is considered that a salt can be formed with the phthalocyanine compound and the metal nickel fine particles can be coated. Since polyoxyethylene alkyl ether carboxylic acid or a salt thereof has a strong aggregation inhibitory action on the metal nickel fine particles, an excellent dispersion effect can be expected even in a small amount. However, when there is no phthalocyanine compound on the surface of the metal nickel fine particles, even if polyoxyethylene alkyl ether carboxylic acid or a salt thereof is added, it is difficult to bind to the surface of the metal nickel fine particles, and polyoxyethylene alkyl ether carboxylic acid Or the strong aggregation inhibitory effect and the outstanding dispersion effect by the salt are not acquired.

  The addition amount of the polyoxyethylene alkyl ether carboxylic acid or a salt thereof used in the present embodiment is within a range of 0.01 to 10 parts by mass, preferably 0.1 to 50 parts per 100 parts by mass of the phthalocyanine-modified metal nickel fine particles. Within the range of parts by mass is preferable. When the addition amount is less than the above lower limit, the dispersibility tends to decrease, and when it exceeds the upper limit, aggregation tends to occur.

  The polyoxyethylene alkyl ether carboxylic acid or salt thereof used in the present embodiment can be used alone or in combination of two or more. Moreover, it can also be used in combination with the dispersing agent which consists of another compound in the range which does not impair the effect of invention.

  In the present embodiment, the application method of the polyoxyethylene alkyl ether carboxylic acid or its salt is not particularly limited. For example, a) a predetermined amount of polyoxyethylene alkyl ether carboxylic acid or its B) a method of adding salt, b) mechanically crushing phthalocyanine-modified metal nickel fine particles using a disperser such as a high-pressure homogenizer, an ultrasonic homogenizer, a bead mill disperser, etc. Various methods such as a method of adding and dispersing oxyethylene alkyl ether carboxylic acid or a salt thereof may be mentioned.

  As described above, by carrying out Step A to Step C, a dispersible nickel fine particle slurry coated with polyoxyethylene alkyl ether carboxylic acid or a salt thereof having a strong aggregation suppressing action on the raw metal nickel fine particles is obtained. It is done. This dispersible nickel fine particle slurry is an aggregate of metal nickel fine particles having a sharp particle size distribution in which aggregation is suppressed and single particles are dispersed, for example, even for fine metal nickel fine particles having a particle size of 150 nm or less. It can be suitably used as a material for a conductive paste for forming an internal electrode of a multilayer ceramic capacitor (MLCC).

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of average particle size]
A photograph of the sample was taken with an SEM (scanning electron microscope), 200 samples were randomly extracted from the sample, and the respective particle sizes were determined to calculate the average particle size.

[Evaluation of dispersibility]
Evaluation of dispersibility was performed using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd., trade name: LA-950V2). A slurry solution (solid content concentration 10 wt%) in which the sample is dispersed in toluene is diluted to a predetermined concentration, and dispersed in the particle size distribution measuring apparatus with ultrasonic waves for 5 minutes, and the volume distribution is measured. The results of distribution were used for comparative evaluation of dispersibility.

  The dispersants and their abbreviations used to produce the dispersible nickel fine particle slurry are as follows.

Dispersant (1): polyoxyethylene alkyl ether carboxylic acid (Taiko Oil Chemical Co., Ltd., Taipol Soft (registered trademark) ECA-390)
Dispersant (2): polyoxyethylene alkyl ether carboxylic acid (Taiko Oil Chemical Co., Ltd., Taipol Soft (registered trademark) ECA-490)
Dispersant (3): polyoxyethylene alkyl ether carboxylic acid (Taiko Oil Chemical Co., Ltd., Taipol Soft (registered trademark) ECA-1090)
Dispersant (4): Polyester polymer dispersant (manufactured by Nippon Lubrizol, trade name: Solsperse 3000, polyester-terminal carboxylic acid)
Dispersant (5): Urethane polymer dispersant (manufactured by Nippon Lubrizol, trade name: Solsperse 55000, urethane-terminated carboxylic acid)

(Synthesis Example 1-1)
18.5 g of nickel formate dihydrate was added to 125.9 g of laurylamine and heated at 120 ° C. for 10 minutes under a nitrogen flow to dissolve nickel formate to obtain a complexing reaction solution. Next, 83.9 g of laurylamine was further added to the complexing reaction solution, and the mixture was heated at 180 ° C. for 10 minutes using a microwave to obtain a metal nickel fine particle slurry 1a ′.

  The obtained metallic nickel fine particle slurry 1a 'was allowed to stand and separated, and the supernatant was removed, followed by washing with a mixed solvent having a volume ratio of methanol to toluene of 1: 4. Then, the metal nickel fine particle 1a which the primary amine coat | covered was obtained by drying with the vacuum dryer maintained at 60 degreeC for 6 hours. The average particle diameter of the metallic nickel fine particles 1a thus obtained was 100 nm, and as a result of elemental analysis, C: 0.9, N; 0.06, O; 1.4 (unit: mass%) It was.

(Synthesis Example 1-2)
The metallic nickel fine particle slurry 1a ′ obtained in Synthesis Example 1-1 was left standing and separated, and the supernatant was removed, followed by washing with a mixed solvent having a volume ratio of methanol to toluene of 1: 4. Then, after further washing with isopropanol and adjusting the solid content concentration to 10 wt% with an isopropanol solvent, using a high-pressure homogenizer (manufactured by Sugino Machine Co., Ltd., trade name: Starburst HJP-25008), A metal nickel fine particle slurry 1b ′ in which metal nickel fine particles 1a are dispersed under a pressure of 200 MPa was prepared.

(Synthesis Example 2-1)
0.070 g of dodecanthiol is added to 100 g of the metal nickel fine particle slurry 1a ′ obtained by Synthesis Example 1-1 (adjusted to a solid content concentration of 4.0 wt%) and heated at 230 ° C. for 5 minutes. Thus, a metal nickel fine particle slurry 2a ′ coated with a primary amine and a sulfur-containing compound was obtained.

  The obtained metal nickel fine particle slurry 2a 'was separated and allowed to stand and separated, and the supernatant was removed, followed by washing with a mixed solvent of methanol and toluene in a volume ratio of 1: 4. Then, the metal nickel fine particle 2a which the primary amine and the sulfur containing compound coat | covered was obtained by drying for 6 hours with the vacuum dryer maintained at 60 degreeC. The average particle diameter of the metallic nickel fine particles 2a thus obtained is 100 nm. As a result of elemental analysis, C: 0.6, N: 0.05, O: 1.4, S: 0.4 (unit Was mass%).

(Synthesis Example 2-2)
The metallic nickel fine particle slurry 2a ′ obtained in Synthesis Example 2-1 was allowed to stand and separated, and after removing the supernatant, it was washed with a mixed solvent having a volume ratio of methanol and toluene of 1: 4, and isopropanol was further removed. The solid content concentration was adjusted to 10 wt% with an isopropanol solvent, and then the pressure was adjusted to 200 MPa using a high-pressure homogenizer (trade name: Starburst HJP-25008, manufactured by Sugino Machine Co., Ltd.). Thus, a metal nickel fine particle slurry 2b ′ in which the metal nickel fine particles 2a are dispersed was prepared.

(Comparative Example 1)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. Next, the dihydroterpinyl acetate solvent was substituted while washing with dihydroterpinyl acetate three times, and the particle size distribution was measured. The results are shown in Table 1.

(Comparative Example 2)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. To this, 0.05 g (0.5 wt%) of phthalocyanine was added, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained phthalocyanine-modified nickel fine particles were substituted with a dihydroterpinyl acetate solvent while washing with dihydroterpinyl acetate three times, and the particle size distribution was measured. The results are shown in Table 1.

(Reference Example 1)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. 0.2 g of dispersant (1) was added thereto, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained nickel fine particles were treated with a 50 kHz ultrasonic device for 15 minutes, then washed with dihydroterpinyl acetate three times, and then replaced with a dihydroterpinyl acetate solvent, and the particle size distribution was measured. . The results are shown in Table 1.

Example 1
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. To this, 0.05 g (0.5 wt%) of phthalocyanine was added, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. To about 1 g of the obtained phthalocyanine-modified nickel fine particles, 0.2 g of the dispersant (1) was added, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed with dihydroterpinyl acetate three times. The particle size distribution was measured by substituting with a nyl acetate solvent. The results are shown in Table 1.

(Comparative Example 3)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. 0.2 g of oleic acid was added thereto, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained nickel fine particles were treated with a 50 kHz ultrasonic device for 15 minutes, then washed with dihydroterpinyl acetate three times, and then replaced with a dihydroterpinyl acetate solvent, and the particle size distribution was measured. . The results are shown in Table 2.

(Comparative Example 4)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. 0.2 g of octanoic acid was added thereto, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained nickel fine particles were treated with a 50 kHz ultrasonic device for 15 minutes, then washed with dihydroterpinyl acetate three times, and then replaced with a dihydroterpinyl acetate solvent, and the particle size distribution was measured. . The results are shown in Table 2.

(Comparative Example 5)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. To this, 0.05 g (0.5 wt%) of phthalocyanine was added, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. 0.2 g of oleic acid is added to about 1 g of the obtained phthalocyanine-modified nickel fine particles, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed with dihydroterpinyl acetate three times to obtain a dihydroterpinyl acetate solvent. The particle size distribution was measured. The results are shown in Table 2.

(Comparative Example 6)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. To this, 0.05 g (0.5 wt%) of phthalocyanine was added, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. 0.2 g of octanoic acid is added to about 1 g of the obtained phthalocyanine-modified nickel fine particles, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed with dihydroterpinyl acetate three times to obtain a dihydroterpinyl acetate solvent. The particle size distribution was measured. The results are shown in Table 2.

(Comparative Example 7)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. Next, the isopropyl alcohol solvent was substituted while washing with isopropyl alcohol three times, and the particle size distribution was measured. The results are shown in Table 3.

(Comparative Example 8)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. 0.2 g of the dispersant (2) was added thereto, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained nickel fine particles were treated with a 50 kHz ultrasonic device for 15 minutes and then replaced with an isopropyl alcohol solvent while washing with isopropyl alcohol three times, and the particle size distribution was measured. The results are shown in Table 3.

(Comparative Example 9)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. About 1 g of the nickel fine particles was added with 0.2 g of the dispersant (3), treated with a 50 kHz ultrasonic device for 15 minutes, and then replaced with isopropyl alcohol solvent while washing with isopropyl alcohol three times. Measurements were made. The results are shown in Table 3.

(Comparative Example 10)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. About 1 g of the nickel fine particles was added with 0.2 g of the dispersing agent (1), treated with a 50 kHz ultrasonic device for 15 minutes, and then replaced with an isopropyl alcohol solvent while washing with isopropyl alcohol three times. Measurements were made. The results are shown in Table 3.

(Comparative Example 11)
10 g of the metal nickel fine particle slurry 2b ′ prepared in Synthesis Example 2-2 was statically separated and the solvent was replaced with toluene, and then the solid content concentration was adjusted to 10 wt%. 0.2 g of oleyl sarcosine is added to about 1 g of the nickel fine particles, treated with a 50 kHz ultrasonic device for 15 minutes, then replaced with isopropyl alcohol solvent while washing with isopropyl alcohol three times, and the particle size distribution is measured. It was. The results are shown in Table 3.

(Reference Example 2)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. Next, the isopropyl alcohol solvent was substituted while washing with isopropyl alcohol three times, and the particle size distribution was measured. The results are shown in Table 4.

(Reference Example 3)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. 0.2 g of the dispersant (2) was added thereto, treated with a 50 kHz ultrasonic device for 15 minutes, and then washed twice with toluene. About 1 g of the obtained nickel fine particles were treated with a 50 kHz ultrasonic device for 15 minutes and then replaced with an isopropyl alcohol solvent while washing with isopropyl alcohol three times, and the particle size distribution was measured. The results are shown in Table 4.

(Reference Example 4)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. About 1 g of the nickel fine particles was added with 0.2 g of the dispersant (3), treated with a 50 kHz ultrasonic device for 15 minutes, and then replaced with isopropyl alcohol solvent while washing with isopropyl alcohol three times. Measurements were made. The results are shown in Table 4.

(Reference Example 5)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. About 1 g of the nickel fine particles was added with 0.2 g of the dispersing agent (1), treated with a 50 kHz ultrasonic device for 15 minutes, and then replaced with an isopropyl alcohol solvent while washing with isopropyl alcohol three times. Measurements were made. The results are shown in Table 4.

(Reference Example 6)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. 0.2g of SOLPERSE 3000 is added to about 1g of the nickel fine particles, treated with a 50kHz ultrasonic device for 15 minutes, then replaced with isopropyl alcohol solvent while washing with isopropyl alcohol three times, and the particle size distribution is measured. It was. The results are shown in Table 4.

(Reference Example 7)
10 g of the metal nickel fine particle slurry 1a ′ prepared in Synthesis Example 1-1 was allowed to stand and separated, and after the solvent was replaced with toluene, the solid content concentration was adjusted to 10 wt%. 0.2g of SOLPERSE 55000 is added to about 1g of the nickel fine particles, treated with a 50kHz ultrasonic device for 15 minutes, then replaced with isopropyl alcohol solvent while washing with isopropyl alcohol three times, and the particle size distribution is measured. It was. The results are shown in Table 4.

  As shown in Table 1, in Example 1, the volume distribution D50 [median diameter; the particle diameter at which the cumulative particle size distribution (volume basis) from the small particle diameter side becomes 50%] is sufficiently small. In the example, it was found that D50 was large, there were many aggregates, and the dispersibility was low. Further, examples of the volume distribution D90 [particle diameter at which the cumulative particle size distribution (volume basis) from the small particle diameter side becomes 90%] and D99 [particle diameter at 99% from the small particle diameter side], which are rough coarse agglomerated particles, are given as examples. It was confirmed that No. 1 was much smaller than the comparative example, there were few aggregated particles, the particle size distribution was sharp, and the dispersibility was good.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

Claims (4)

Next steps A to C;
A) preparing a slurry containing raw metal nickel fine particles and an organic solvent at least partially coated with a primary amine and elemental sulfur or a sulfur-containing compound;
B) A phthalocyanine-modified metal that is partially coated with the phthalocyanine compound by adding a phthalocyanine compound to the slurry and replacing at least a portion of the primary amine with the phthalocyanine compound on the surface of the raw material nickel metal fine particles Obtaining nickel fine particles,
C) adding polyoxyethylene alkyl ether carboxylic acid or a salt thereof to the phthalocyanine-modified metal nickel fine particles to form a carboxylate with the phthalocyanine compound;
A method for producing a dispersible nickel fine particle slurry.   The method for producing a dispersible nickel fine particle slurry according to claim 1, wherein the primary amine covering the surface of the raw metal nickel fine particles is an aliphatic primary amine.   The method for producing a dispersible nickel fine particle slurry according to claim 1 or 2, wherein the raw metal nickel fine particles are preliminarily pulverized in an organic solvent using a wet pulverizer. The raw metal nickel fine particles are
Next steps I and II;
I) a step of heating a mixture of nickel carboxylate and primary amine to a temperature in the range of 100 ° C. to 165 ° C. to obtain a complexing reaction solution;
II) A step of heating the complexing reaction solution to a temperature of 170 ° C. or higher by microwave irradiation to reduce nickel ions in the complexing reaction solution to obtain metallic nickel fine particles coated with a primary amine.
III) A step of obtaining raw material nickel fine particles by mixing elemental sulfur or a sulfur-containing compound with metallic nickel fine particles coated with a primary amine,
The method for producing a dispersible nickel fine particle slurry according to any one of claims 1 to 3, which is prepared by a method comprising: