JP7430664B2 - metal particles - Google Patents

Description

The present invention relates to a method for producing metal particles and metal particles using a wet reduction method.

Metal particles have physical and chemical properties different from those of bulk metals, so they can be used, for example, as electrode materials such as conductive pastes and transparent conductive films, high-density recording materials, catalyst materials, bonding materials for semiconductor devices, and ink jets. It is used in various industrial materials such as industrial ink materials.

It is known that metal particles can be obtained by solid phase reaction or liquid phase reaction. As solid phase reactions, chemical vapor deposition of nickel chloride, thermal decomposition of nickel formate, etc. are known. Liquid phase reactions include a method in which a metal salt is directly reduced with a strong reducing agent such as sodium borohydride (for example, Patent Document 1), and a method in which a reducing agent such as hydrazine is added in the presence of a strong alkali to reduce the precursor. There are methods of thermally decomposing the metal complex after formation (for example, Patent Document 2), and methods of synthesizing by thermal decomposition by placing a metal complex containing a metal salt and an organic ligand in a pressure vessel together with a solvent (for example, Patent Document 3). Can be mentioned.

In order to suitably use metal particles for applications such as electrode materials such as conductive pastes and transparent conductive films, high-density recording materials, catalyst materials, and inkjet ink materials, it is necessary to control fine particles with uniform particle diameters. .

However, in the case of a method using chemical vapor deposition among solid phase reactions, particles tend to enlarge from submicron to micron order. Furthermore, in the case of a method using thermal decomposition, particles tend to aggregate due to the high reaction temperature. These manufacturing methods using solid phase reactions tend to be more expensive than manufacturing methods using liquid phase reactions.

On the other hand, in the case of a liquid phase reaction that uses a strong reducing agent, particles are immediately reduced, making it difficult to control the reaction to obtain desired particles. In addition, in the case of the method of passing through the precursor, the precursor forms a gel, making the subsequent reduction reaction non-uniform, and in the case of hydrogen synthesis, the reaction temperature is high, so aggregation cannot be avoided in either case. .

Furthermore, a technique has been proposed in which fine nickel particles are obtained by adding a reducing agent such as a primary amine to a metal salt and heating the mixture by irradiating it with microwaves (for example, Patent Document 4). According to this technique, the particle size of metal particles can be controlled by adjusting the length of the carbon chain of the aliphatic primary amine or by adding a noble metal salt to the complexing reaction solution. Although this method allows metal particles with the desired particle size to be obtained, it cannot be applied to metal complexes that have excellent crystallinity but low reducibility, such as nickel chloride-amine complexes and nickel sulfate-amine complexes. However, since noble metal salts are used for the purpose of accelerating the reaction, the manufacturing cost tends to be high. Further, silver and the like tend to undergo migration in wiring materials and electronic devices such as batteries, and have an adverse effect on electrical properties, so that their usage is likely to be restricted.

Japanese Patent Application Publication No. 2003-193118 Japanese Patent Application Publication No. 2008-95146 Japanese Patent Application Publication No. 2010-105149 Re-publication WO2011/115213 publication

For example, bonding materials for power semiconductors such as SiC installed in automobiles are required to have electrical conductivity, thermal conductivity, mechanical strength, durability, etc. In order to meet these requirements, The bonding condition of the bonding material that bonds the power semiconductor and the electrode is extremely important. Specifically, it is preferable that the bonding area between the bonding materials or between the bonding material and the object to be bonded be large. However, if the bonding material paste has poor dispersibility and causes agglomeration or sedimentation, it may not be possible to apply the bonding material paste evenly on the power semiconductor or electrode, resulting in a large bonding area. The problem was that it was difficult.

An object of the present invention is to provide a method for producing metal particles that can control the particle size of metal particles by a simple method and at low cost, has excellent dispersibility, and is unlikely to cause aggregation or sedimentation, and to provide metal particles. be.

In view of the above-mentioned problems, the present inventors have conducted extensive research and have focused on the ligands of metal complexes, and by using organometallic compounds with nucleophilic properties, they have been able to remove metal complexes with low reducibility. It was discovered that not only metal particles could be obtained, but also metal particles whose particle diameter could be controlled by adjusting the amount of the organometallic compound added, leading to the completion of the present invention.

That is, the method for producing metal particles of the present invention includes the following steps A and B;
A) A step of mixing a metal salt and a reducing agent to obtain a metal complexing reaction solution,
B) heating the metal complexing reaction liquid to reduce metal ions in the metal complexing reaction liquid to obtain a slurry of metal particles;
Contains. In the method for producing metal particles of the present invention, an alkali metal organic metal compound or an alkaline earth An organometallic compound selected from metal-based organometallic compounds is added.

In the method for producing metal particles of the present invention, the organometallic compound may have nucleophilicity.

In the method for producing metal particles of the present invention, the organometallic compound may be an organomagnesium halide or an organolithium.

In the method for producing metal particles of the present invention, the metal salt may be a nickel salt, a copper salt, or a cobalt salt.

In the method for producing metal particles of the present invention, the average particle diameter of the metal particles may be within a range of 5 to 1000 nm.

In the method for producing metal particles of the present invention, metal particles may be added to the metal complexing reaction solution obtained in step A above.

The metal particles of the present invention are metal particles containing a metal species selected from base metals and/or noble metals as a main component, and have an alkali metal or alkaline earth metal content of 0.1 mg/ kg or more and 2,000 mg/kg or less.

The metal particles of the present invention may have an average particle diameter within the range of 5 to 1000 nm.

In the metal particles of the present invention, the metal species may be one or more metals selected from nickel, titanium, cobalt, copper, gold, silver, and platinum.

The metal particles of the present invention are characterized by containing a trace amount of an alkali metal or an alkaline earth metal, and according to the manufacturing method thereof, the metal particles can be easily manufactured by adding a predetermined amount of an organometallic compound. In addition, it has good dispersibility when made into a paste, slurry, or dispersion, and metal particles having a desired particle size can be produced. When the metal particles of the present invention are used, for example, as a bonding material, they have excellent dispersibility and are resistant to agglomeration and sedimentation, allowing the bonding material paste to be uniformly spread over objects to be bonded such as power semiconductors and electrodes. It becomes possible to apply it to As a result, the bonding area between the bonding material and the objects to be bonded can be increased, and the reliability of the electronic device can be improved.

Embodiments of the present invention will be described below. The method for manufacturing metal particles of this embodiment includes the following steps A and B;
A) A step of mixing a metal salt and a reducing agent to obtain a metal complexing reaction solution,
B) heating the metal complexing reaction liquid to reduce metal ions in the metal complexing reaction liquid to obtain a slurry of metal particles;
Contains. In the method for producing metal particles according to the present embodiment, the organometallic compound is added at any timing from step A to heating the metal complexing reaction solution in step B.

[Process A]
Step A is a step of mixing a metal salt and a reducing agent to obtain a metal complexing reaction solution.

<Metal salt>
Examples of the metal salt include known salts of base metals and salts of noble metals. Here, examples of base metals include nickel, titanium, cobalt, copper, chromium, manganese, iron, zirconium, tin, tungsten, molybdenum, and vanadium. Examples of the noble metal include gold, silver, platinum, palladium, iridium, osmium, ruthenium, rhodium, and rhenium. Among the above base metals or noble metals, it is easy to apply to various industrial materials such as electrode materials such as conductive pastes and transparent conductive films, high-density recording materials, catalyst materials, bonding materials for semiconductor devices, and ink materials for inkjet. , nickel, titanium, cobalt, copper, gold, silver, and platinum are preferred. The metal salt may contain one or more of the above metal elements. Examples of metal salts include organic acid metal salts such as carboxylic acid metal salts, and inorganic metal salts such as chloride metal salts, sulfate metal salts, nitrate metal salts, and carbonate metal salts. Among these, chloride metal salts and carboxylic acid metal salts having 1 to 12 carbon atoms in the portion excluding the COOH group are preferred because they allow easy control of the particle size and particle size distribution of the metal particles. Among these, nickel chloride, nickel acetate, copper acetate, and cobalt acetate are more preferred.

<Reducing agent>
The reducing agent used in this embodiment is not particularly limited as long as it can form a complex with the metal, but for example, primary amines and aliphatic alcohols are preferably used. In particular, primary amines are preferable because they can form complexes with metals and can effectively exhibit the ability to reduce metal complexes. On the other hand, secondary amines have a large steric hindrance, which may inhibit the good formation of metal complexes, and tertiary amines do not have the ability to reduce metals, so they cannot be used alone, but primary amines In use, these may be used in combination as long as the shape of the metal particles to be produced is not affected. Moreover, a primary amine and an aliphatic alcohol can also be used together.

The reducing agent can be solid or liquid at room temperature. Here, normal temperature refers to 20°C±15°C. Primary amines that are liquid at room temperature also function as organic solvents when forming metal complexes. Note that even if the primary amine is solid at room temperature, there is no particular problem as long as it becomes liquid when heated to 100° C. or higher or dissolves using an organic solvent.

Although the primary amine may be an aromatic primary amine, an aliphatic primary amine is preferable from the viewpoint of ease of forming a nickel complex in the reaction solution. Aliphatic primary amines can control the dispersibility of metal particles produced by adjusting the length of their carbon chains, for example, and are advantageous in applications that require dispersibility. From the viewpoint of controlling the agglomeration of metal particles, it is preferable to use an aliphatic primary amine selected from those having about 6 to 20 carbon atoms. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine. Oleylamine and dodecylamine are particularly preferred because they exist in a liquid state under the temperature conditions during the metal particle production process, and therefore the reaction can proceed efficiently in a homogeneous solution. Most preferred is oleylamine.

Similarly, aliphatic alcohols can control the dispersibility of metal particles produced by adjusting the length of their carbon chains, for example, and are advantageous in applications where dispersibility is required. From the viewpoint of controlling agglomeration of metal particles, it is preferable to use an aliphatic alcohol selected from those having about 8 to 18 carbon atoms. Examples of such aliphatic alcohols include octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetotadecanol, pentadecanol, hexadecanol, heptadecanol, and octadecanol. Octanol, decanol, and dodecanol are particularly preferable because they exist in a liquid state under the temperature conditions in the metal particle production process, so that the reaction can proceed efficiently in a homogeneous solution.

Since the primary amine and aliphatic alcohol function as surface modifiers during the generation of metal particles, secondary aggregation can be suppressed even after the primary amine and aliphatic alcohol are removed. In addition, primary amines and aliphatic alcohols are easy to handle in the cleaning step to separate the solid components of the generated metal particles from the solvent or unreacted primary amines or aliphatic alcohols after the reduction reaction in step B. From this point of view, those that are liquid at room temperature are preferable. Furthermore, the primary amine and aliphatic alcohol preferably have a boiling point higher than the reduction temperature from the viewpoint of ease of reaction control when reducing the metal complex to obtain metal particles. The amount of the primary amine or aliphatic alcohol is preferably used at a ratio of 1 mol or more of the valence of the metal, more preferably 1.1 times the mol or more of the valence of the metal, per 1 mol of the metal. It is more preferable to use valence x 2 times the mol or more. If the amount of the primary amine or aliphatic alcohol is less than the valence of the metal x 1 times the mol, it will be difficult to control the particle size of the resulting metal particles, and the particle size will tend to vary. Further, although there is no particular upper limit to the amount of the primary amine or aliphatic alcohol, for example, from the viewpoint of productivity, it is preferably less than 10 times the valence of the metal in mol.

The conditions for forming the metal complexing reaction solution in step A, that is, the conditions for mixing the metal salt and reducing agent, vary depending on the metal salt and reducing agent used, so appropriate conditions may be selected depending on the raw materials used. Here, an example will be described in which a nickel carboxylate is used as the metal salt and a primary amine is used as the reducing agent. In this case, the complex formation reaction can proceed at room temperature, but in order to carry out a sufficient and more efficient complex formation reaction, it is heated to a temperature within the range of 100°C to 165°C, for example. Preferably, the reaction is carried out. By setting the heating temperature to preferably a temperature exceeding 100°C, more preferably a temperature of 105°C or higher, the ligand substitution reaction between the coordinated water coordinated to the nickel carboxylate and the primary amine can be efficiently carried out. This allows water molecules as complex ligands to be dissociated, and furthermore, the water can be taken out of the system, so that complexes with amines can be efficiently formed. In addition, when nickel formate dihydrate is used as nickel carboxylate, at room temperature it has a complex structure in which two coordinating waters and two formic acids, which are bidentate ligands, exist. In order to efficiently form a complex by substitution of two coordinated waters and a primary amine with a ligand, it is preferable to heat at a temperature higher than 100° C. to dissociate water molecules as complex ligands. The heating time can be appropriately determined depending on the heating temperature and the content of each raw material. Although there is no particular upper limit to the heating time, unnecessarily long heat treatment is wasteful from the viewpoint of saving energy consumption and process time.

The heating method in step A is not particularly limited, and may be, for example, heating using a heat medium such as an oil bath, or heating using microwave irradiation or ultrasonic irradiation.

In step A, an organic solvent other than the primary amine may be newly added in order to advance the reaction in a homogeneous solution more efficiently. When using an organic solvent, the organic solvent may be mixed at the same time as the metal salt and the reducing agent, but if the metal salt and reducing agent are first mixed to form a complex and then the organic solvent is added, the reducing agent will efficiently convert the metal atoms. It is more preferable because it coordinates with The organic solvent that can be used is not particularly limited as long as it does not inhibit the complex formation between the metal salt and the reducing agent. For example, ether organic solvents having 4 to 30 carbon atoms, saturated organic solvents having 7 to 30 carbon atoms, Alternatively, an unsaturated hydrocarbon organic solvent or the like can be used. Further, from the viewpoint of enabling use even under heating conditions, it is preferable to select an organic solvent having a boiling point of 170° C. or higher. Specific examples of such organic solvents include tetraethylene glycol, n-octyl ether, and lauryl alcohol.

[Process B]
In step B, the metal complexing reaction liquid obtained by the complexing reaction is heated to reduce the metal in the metal complexing reaction liquid to obtain a slurry of metal particles. The heating temperature in step B varies depending on the metal species, particle size, particle size distribution, etc. of the metal particles to be obtained.

For example, when synthesizing nickel particles with an average particle size of 5 to 100 nm, the temperature is preferably 170° C. or higher, more preferably 180° C. or higher, from the viewpoint of suppressing shape variations. In this case, there is no particular upper limit to the heating temperature, but from the viewpoint of efficient processing, it is preferably 270° C. or lower, for example.

Further, for example, when synthesizing copper particles having an average particle diameter of 300 to 600 nm, the temperature is preferably 200° C. or higher, more preferably 220° C. or higher, from the viewpoint of suppressing shape variations. In this case, there is no particular upper limit to the heating temperature, but from the viewpoint of efficient processing, it is preferably 270° C. or lower, for example.

Examples of the heating means in step B include heating methods using a heat medium such as an oil bath, electricity, microwaves, and ultrasonic waves. From the viewpoint of production cost, a heating method using a heat medium such as an oil bath or electricity is preferably used.

In step B, a dispersant or functional additive may be added to improve the dispersibility of metal particles or to provide functions such as a rust preventive agent to prevent oxidation. .

[Addition of organometallic compound]
The organometallic compound used in this embodiment is not particularly limited as long as it has properties similar to the nucleophilic reagent (nucleophilicity) and acts on the metal complex. Preferred organometallic compounds are those in which an alkali metal is coordinated with an organic group such as an alkyl group or an alkoxy group, from the viewpoint of ease of controlling the particle size and particle size distribution of metal particles, safety, simplicity, and productivity. Examples include alkali metal-based organometallic compounds and alkaline-earth metal-based organometallic compounds in which the organic group is coordinated to an alkaline earth metal. Hereinafter, the alkali metal organic compound and the alkaline earth metal organic compound will be collectively referred to as "the present organometallic compound." The organometallic compound may be an organometallic halide containing halides such as chlorine, bromine, and iodine. In this case, they are also referred to as an alkali metal-based organometallic halide and an alkaline earth metal-based organometallic halide, respectively. Alkali metal-based organometallic halides are one form of alkali metal-based organometallic compounds, and alkaline earth metal-based organometallic halides are one form of alkaline earth metal-based organometallic compounds.

Examples of the alkali metal constituting the alkali metal-based organometallic compound include lithium, sodium, potassium, rubidium, and cesium, and organolithium containing highly reactive lithium is preferably used.
Examples of the alkaline earth metals constituting the alkaline earth metal-based organometallic compound include beryllium, magnesium, calcium, strontium, and barium, and organomagnesium halides containing magnesium, which have good reactivity, Suitably used. Note that alkylaluminum, in which an alkyl group is coordinated with aluminum, has strong flammability, so from the viewpoint of safety and convenience, alkali metal-based and alkaline earth metal-based organometallic compounds are more preferably used. .

The present organometallic compound is preferably used as a diluted solution diluted with an organic solvent such as tetrahydrofuran, hexane, toluene, cyclohexane, butyl ether, dibutyl ether, or the like. There is no limit to the concentration of the diluted solution, but if the particle size is affected by a small amount, a low concentration is preferable because it is easier to control.

As the alkali metal-based organometallic compound, cheap and general-purpose n-butyllithium and phenyllithium are suitably used, and solutions of these toluene and n-hexane are particularly suitable from the viewpoint of safety and convenience. .
Furthermore, as the alkaline earth metal-based organometallic compound, ethylmagnesium chloride, ethylmagnesium bromide, butylmagnesium chloride, 2-butylmagnesium chloride-lithium chloride complex, and butylmagnesium bromide are preferably used, and solutions of these in tetrahydrofuran are particularly preferable. used for.

The amount of the organometallic compound to be added is not particularly limited, as the amount to be added may be selected depending on the intended particle size. Specifically, the amount of the organometallic compound added is as exemplified below.

For example, when nickel particles are formed using a metal complex obtained by mixing nickel acetate and oleylamine (metal complexation reaction liquid) and a 2N-ethylene magnesium chloride tetrahydrofuran (containing 18% by weight ethylene magnesium chloride) solution. It is preferable to add ethylene magnesium chloride in an amount of 0.01 to 5 parts by weight per 100 parts by weight of nickel. In this case, if the amount added is less than 0.01 parts by weight, the effect of making the nickel particles finer is small, and the particle size distribution of the nickel particles tends to become larger. Moreover, when the amount added exceeds 5 parts by weight, ethylene magnesium chloride, which does not contribute to the formation of fine particles of nickel particles and becomes an impurity, tends to increase.

For example, when forming nickel particles using a butyl ether solution of about 1.6 mol/L phenyllithium (containing 16% by weight of phenyllithium) as the organometallic compound in a metal complex obtained by reacting nickel acetate and oleylamine, It is preferable to add phenyllithium in an amount of 0.03 to 5 parts by weight per 100 parts by weight of nickel. In this case, if the amount added is less than 0.03 parts by weight, the effect of making the nickel particles into fine particles is small, and the particle size distribution of the nickel particles tends to become large. Furthermore, when the amount added exceeds 5 parts by weight, phenyllithium, which does not contribute to the formation of fine particles of nickel particles and becomes an impurity, tends to increase.

Alternatively, for example, a tetrahydrofuran solution of 2N-ethylenemagnesium chloride (containing 18% by weight of ethylenemagnesium chloride) as the organometallic compound is added to a metal complex obtained by reacting copper acetate (anhydride) with oleylamine to form copper particles. In this case, it is preferable to add 5 parts by weight or more of ethylene magnesium chloride to 100 parts by weight of copper. In this case, if the amount added is less than 5 parts by weight, particles with a diameter of 600 nm or less will not be produced, and irregularly shaped particles or fibrous copper may be contained.

The organometallic compound may be added at any timing from step A to heating the metal complexing reaction solution in step B. For example, the organometallic compound may be added after mixing the metal salt and reducing agent and removing excess water in step A, or may be added after preparing the metal complexing reaction solution. Further, since the present organometallic compound is easily deactivated by moisture and loses its effect, it is preferably added immediately before heating the metal complexing reaction solution in step B. By adding the present organometallic compound, the particle size of the metal particles can be significantly reduced. Although its mechanism of action is not yet clear, it is presumed that an organometallic compound with nucleophilic properties acts on the metal complex and promotes the generation of metal nuclei. It is preferable to add the organometallic compound immediately before heating the metal complexing reaction solution in step B, since the effect is lost due to the influence of moisture absorption, making it difficult to control the particle size distribution.

[Metal particles]
In the manner described above, a slurry containing metal particles can be obtained. Note that it is also possible to collect the dried metal particles by, for example, separating the obtained slurry of metal particles by standing, removing the supernatant liquid, washing with an appropriate solvent, and drying. good. The manufactured metal particles contain as a main component a base metal and/or a noble metal that is the same metal type as the above-mentioned metal salt as a raw material, and also contain an alkali metal or an alkaline earth metal contained in the organometallic compound used. Become something to do. Here, the "main component" refers to a total of 90% by weight or more, preferably 95% by weight or more, more preferably 97% by weight of base metals and/or noble metals derived from the metal salt, based on the total weight of the metal particles. % or more. Furthermore, the metal particles may contain elements other than metal elements such as oxygen, hydrogen, carbon, nitrogen, and sulfur, or may be alloys thereof. Furthermore, it may be composed of a single metal particle or a mixture of two or more types of metal particles. Further, the metal particles may have a multilayer structure of the same kind of metal or different kinds of metals, for example, a core-shell structure.

The alkali metal or alkaline earth metal contained in the metal particles varies depending on the amount of the organometallic compound added, but if the value measured by high frequency inductively coupled plasma mass spectrometry (ICP mass spectrometry) is 0.1 mg/kg or more, 2 ,000mg/kg or less. A more preferable lower limit is 0.3 mg/kg, and even more preferably 0.5 mg/kg or more. Further, the upper limit is more preferably 1,800 mg/kg or less, further preferably 1,000 mg/kg or less, particularly preferably 100 mg/kg or less, and most preferably 10 mg/kg or less. Within this range, metal particles with less sedimentation and aggregation and excellent dispersibility (hereinafter also simply referred to as "dispersibility") can be obtained when made into a paste, slurry, or dispersion. If it is less than 0.1 mg/kg, the desired particle size tends not to be obtained, especially in the range where the average particle size is 100 nm or less, while if it exceeds 2,000 mg/kg, dispersibility tends to be impaired. .

In the method for producing metal particles of the present invention, there is no particular restriction on the average particle size of the metal particles obtained, but by adding the present organometallic compound, the average particle size can be adjusted to a desired size within the range of, for example, 5 nm to 1000 nm. can be controlled. For example, in the case of nickel particles, the average particle diameter can be controlled within the range of 5 to 100 nm. Further, in the case of copper particles, the average particle diameter can be controlled within the range of 300 to 600 nm.
In addition, by adding metal particles (also referred to as "seed particles") to the metal complexing reaction solution obtained in step A, a metal layer is further formed on the surface of the seed particles, and the particle size is larger than that of the seed particles. Large metal particles can be obtained. In this case, the metal species constituting the seed particles and the metal species constituting the metal layer may be the same or different. For example, when the seed particles have an average particle size within the range of 20 nm to 40 nm, the average particle size can be increased by adding the seed particles to the metal complexing reaction solution obtained in step A and performing step B. Metal particles of 100 nm or more can be obtained.
Although the method for producing the seed particles is not limited, it is preferable to use metal particles obtained by the method for producing metal particles of the present invention from the viewpoint of ease of controlling the particle size and particle size distribution of the metal particles. .
Further, by adding the present organometallic compound, metal particles with a narrow particle size distribution can be obtained. Specifically, metal particles having a CV value, which is an index of particle size distribution, of 0.3 or less can be obtained.

In addition, when functions such as dispersibility, heat resistance, catalytic action, and electrical conductivity are required for metal particles, we apply dispersants, different metals, and electrical conductivity to the obtained metal particles depending on the purpose of use. Additives such as inorganic and organic substances having the following properties can be added within a range that does not inhibit the production of metal particles.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples in any way. In addition, in the following examples, measurements and evaluations are as follows unless otherwise specified.

[Measurement of average particle diameter]
To measure the average particle size, take a photo of the sample using a SEM (scanning electron microscope), randomly select 200 particles from the sample, calculate the area of each particle, and calculate the particle size when converted to a perfect sphere. The average particle diameter of primary particles was calculated as a number standard. Further, the CV value (coefficient of variation) was calculated by (standard deviation)÷(average particle diameter). Note that the smaller the CV value, the more uniform the particle diameter is.

[Organometallic compound]
Organometallic compound (1): Tokyo Chemical Industry Co., Ltd., approximately 10% tetrahydrofuran solution of ethylmagnesium chloride (approximately 1 mol/L)
Organometallic compound (2): Tokyo Chemical Industry Co., Ltd., approximately 15% hexane solution of butyllithium (1.6 mol/L)
Organometallic compound (3): manufactured by Tokyo Chemical Industry Co., Ltd., approximately 16% butyl ether solution of phenyllithium (approximately 1.6 mol/L)

(Synthesis example 1)
2466 g of nickel acetate tetrahydrate was added to 6000 g of oleylamine and heated at 140° C. for 4 hours under a nitrogen flow to obtain complex reaction solution 1 (nickel ion concentration: 7.5% by weight).

(Synthesis example 2)
78.7 g of nickel chloride hexahydrate was added to 200 g of oleylamine and heated at 140° C. for 4 hours under a nitrogen flow to obtain a complex reaction solution 2 (nickel ion concentration: 7.5% by weight).

(Synthesis example 3)
65.7 g of copper acetate/anhydride was added to 200 g of oleylamine and heated at 110° C. for 10 minutes under a nitrogen flow to obtain complex reaction solution 3 (copper ion concentration: 7.5% by weight).

(Synthesis example 4)
190.3 g of cobalt acetate tetrahydrate was added to 474.4 g of oleylamine and heated at 140°C for 4 hours under a nitrogen flow to form complexing reaction solution 4 (cobalt ion concentration: 7.5% by weight). Obtained.

(Example 1)
0.358 g of organometallic compound (1) was added to 600 g of complexing reaction solution 1, heated to 230° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form nickel particles 1 (average particles). A diameter of 51.4 nm and a CV value of 0.21) were obtained. 0.87 mg/kg of Mg was detected by ICP mass spectrometry.

(Example 2)
The same procedure as in Example 1 was carried out by adding 0.333 g of organometallic compound (2) to 600 g of complexing reaction solution 1, heating it to 230 ° C. using a mantle heater under a nitrogen flow, and allowing the reaction to occur for 20 minutes. As a result, nickel particles 2 (average particle diameter: 49.8 nm, CV value: 0.27) were obtained. 2.60 mg/kg of Li was detected by ICP mass spectrometry.

(Example 3)
6.0 g of organometallic compound (3) was added to 600 g of complexing reaction solution 1, heated to 210° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form nickel particles 3 (average particles). A diameter of 16.1 nm and a CV value of 0.13) were obtained. Li detected by ICP mass spectrometry was 1,500 mg/kg.

(Example 4)
0.285 g of organometallic compound (3) was added to 600 g of complexing reaction solution 1, heated to 220° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form nickel particles 4 (average particles). A diameter of 50.7 nm and a CV value of 0.20 were obtained. Li detected by ICP mass spectrometry was 3.3 mg/kg.

(Example 5)
0.122 g of organometallic compound (3) was added to 600 g of complexing reaction solution 1, heated to 230° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form nickel particles 5 (average particles). A diameter of 80.4 nm and a CV value of 0.16) were obtained. 1.80 mg/kg of Li was detected by ICP mass spectrometry.

(Comparative example 1)
Nickel particles 6 (average particle diameter: 132.9 nm, CV value: 0.16) were obtained in the same manner as in Example 1, except that the organometallic compound (1) was not added. No alkali metals or alkaline earth metals were detected by ICP mass spectrometry. The nickel particles 6 obtained in Comparative Example 1 could not have the desired particle size (average particle size of about 50 nm), although the raw material composition was the same as in Example 1.

(Example 6)
0.50 g of organometallic compound (1) was added to 240 g of complexing reaction solution 2, heated to 215° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form nickel particles 7 (average particles). Diameter: 54.5 nm, CV value: 0.17). 0.49 mg/kg of Mg was detected by ICP mass spectrometry.

(Comparative example 2)
Nickel particles 8 (average particle diameter: about 400 nm) were obtained by heating in the same manner as in Example 6, except that the organometallic compound (1) was not added, but the yield was low and the particle shape was It was angular.

(Example 7)
5 g of organometallic compound (1) was added to 265.7 g of complexing reaction solution 3, heated to 220° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form copper particles 9 (average particles). Diameter: 486 nm, CV value: 0.15). 5.02 mg/kg of Mg was detected by ICP mass spectrometry.

(Comparative example 3)
By heating 265.7 g of complexing reaction solution 3 to 220° C. using a mantle heater under a nitrogen flow and reacting for 10 minutes, a small number of copper particles 10 (average particle diameter: 1.37 μm, CV value; 0.18), as well as most amorphous and fibrous masses.

(Example 8)
22.5 g of the nickel particles 4 obtained in Example 4 were added to 600 g of the complexing reaction solution 4, heated to 210° C. using a mantle heater under nitrogen flow, and reacted for 20 minutes to form a nickel core, Multilayer cobalt nickel particles 11 (average particle diameter: 80.2 nm, CV value: 0.19) having a core-shell structure of cobalt shells were obtained. Li detected by ICP mass spectrometry was 0.51 mg/kg.

Although the embodiments of the present invention have been described above in detail for the purpose of illustration, the present invention is not limited to the above embodiments.

Claims (2)

A method for producing metal particles containing as a main component a metal species selected from base metals and/or noble metals,
The base metal is one or more selected from nickel, titanium, cobalt, copper, chromium, manganese, iron, zirconium, tin, tungsten, molybdenum or vanadium,
The noble metal is one or more selected from gold, silver, platinum, palladium, iridium, osmium, ruthenium, rhodium or rhenium,
The average particle diameter of the metal particles is within the range of 5 to 1000 nm, and the CV value, which is an index of particle size distribution, is 0.3 or less,
The metal particles have a total content of alkali metals and alkaline earth metals of 0.1 mg/kg or more and 2,000 mg/kg or less as determined by ICP mass spectrometry, and A method for producing metal particles, characterized in that the metal particles include those derived from an organometallic compound added during the production process of the metal particles. The method for producing metal particles according to claim 1, wherein the metal species is one or more metals selected from nickel, titanium, cobalt, copper, gold, silver, and platinum.