JP2013108141A - Metal particulate composition and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal particulate composition including a metal particulate excellent in dispersibility and oxidation resistance.SOLUTION: The metal particulate composition includes (A) a metal particulate containing nickel and having a particle size in the range of 1-150 nm, and (B) abietic acid, and is obtained by blending the component (B) in the range of 0.1-40 pts.mass with 100 pts.mass of the component (A). Preferably, the metal particulate is an alloy of nickel and copper, the amount of the nickel element is in the range of 5-50 pts.wt. and the amount of the copper element is in the range of 50-95 pts.wt. relative to 100 pts.mass of the metal particulate.

Description

  The present invention relates to a metal fine particle composition containing metal fine particles having excellent dispersibility and oxidation resistance, and a method for producing the same.

  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 downsizing and thinning of electronic devices, the particle size of metal fine particles has been reduced to about several tens to several hundreds of nanometers. For example, with the downsizing of electronic devices, the multilayer ceramic capacitor electrodes are becoming thinner and more multilayered, and as a material for the electrode layers, metal particles such as nickel particles are used.

  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), phosphate ester compounds (for example, Patent Document 3) and the like are known. Although these dispersants can achieve a certain degree of dispersion effect, with the progress of micronization, aggregation of metal fine particles having a particle diameter of about several tens to several hundreds of nanometers is not sufficiently achieved. is the current situation. Accordingly, there is a demand for a dispersant exhibiting high dispersibility corresponding to the formation of fine metal particles.

It is known that metal fine particles can be obtained by solid phase reaction or liquid phase reaction. Taking nickel nanoparticles as an example, solid phase reactions include chemical vapor deposition of nickel chloride and thermal decomposition of nickel formate. In the liquid phase reaction, a nickel salt such as nickel chloride is directly reduced with a strong reducing agent such as sodium borohydride, a reducing agent such as hydrazine is added in the presence of NaOH, and the precursor [Ni (H ₂ NNH _{2 2} ] Method of thermal decomposition after forming SO ₄ · 2H ₂ O, Method of hydrothermal synthesis by putting nickel complex such as nickel chloride and nickel complex containing organic ligand into pressure vessel with solvent, nickel formate Examples thereof include a method of adding a reducing agent such as a primary amine to a salt or nickel acetate salt and irradiating with microwaves.

  Conventionally, when producing pastes for internal electrodes such as multilayer ceramic capacitors from nickel particles obtained by solid phase reaction, nickel particles are kneaded in a vehicle, and cationic dispersants and nonionic dispersions are prepared at a predetermined timing. A nickel paste was prepared by adding and dispersing a dispersing agent such as an agent and a zwitterionic system. However, since this production method includes agglomerated nickel particles, coating with a dispersant is performed in the agglomerated state, and a sufficient dispersion effect cannot be obtained. In addition, a method has been proposed in which nickel powder is pulverized using a jet mill or a high-pressure homogenizer, and an organic solvent and a saturated fatty acid are added and dispersed in the organic solvent (for example, Patent Document 4). However, even with this method, the present situation is that aggregation caused by micronization cannot be suppressed.

  Regarding the technique of the liquid phase reaction, a technique of obtaining nickel fine particles by mixing a nickel precursor, an organic amine, and a reducing agent and then heating is disclosed (for example, Patent Document 5). According to this technique, it is said that the control of the size and shape of the nickel fine particles is easy. Although the reason is not certain, it is mentioned that the dispersibility in an organic solvent is improved by coating nickel fine particles with an organic amine. However, when a strong reducing agent is used in this production method, it is difficult to control the reaction, and nickel fine particles having a high dispersibility are not necessarily obtained suitably. On the other hand, when a reducing agent having a weak reducing power is used, it is necessary to heat to high temperature in order to reduce nickel metal having a negative oxidation-reduction potential, and accordingly, reaction control is required.

  A step of producing a mixed solution by adding a reducing agent, a dispersing agent and a nickel salt to the polyol solution; a step of stirring and heating the mixed solution; and a step of reacting the mixed solution to produce nickel fine particles; , A method for producing nickel fine particles is disclosed (for example, Patent Document 6). In this case, although the above-described strong reducing agent is used as the reducing agent, it is said that nickel fine particles having a uniform particle size and excellent dispersibility can be obtained without agglomeration. As the dispersant, a cationic surfactant, an anionic surfactant, a cellulose derivative and the like are described.

  By the way, development of metal fine particles containing copper, which is inexpensive and excellent in conductivity and migration resistance, has been underway as conductive metal fine particles. However, since copper is easily oxidized, there is a problem that the oxidation resistance of the metal fine particles decreases as the copper content increases, and a proposal has been made to provide a gradient in the concentration of copper in the metal fine particles (for example, Patent Document 7).

JP 2001-066951 A JP 2010-135180 A JP 1998-092226 A JP 2006-183066 A JP 2010-037647 A JP 2009-024254 A JP 2011-063828 A

  An object of the present invention is to provide a metal fine particle composition including metal fine particles containing nickel that are excellent in dispersibility and oxidation resistance.

The metal fine particle composition of the present invention comprises the following components (A) and (B),
(A) metal fine particles having a particle diameter of 1 to 150 nm containing nickel, and (B) abietic acid,
Is included. And it mix | blends the said (B) component so that it may become in the range of 0.1-40 mass parts with respect to 100 mass parts of said (A) component.

  In the metal fine particle composition of the present invention, the metal fine particles may be an alloy of nickel and copper. In this case, the metal fine particles have a nickel element amount in the range of 5 to 50 parts by weight and a copper element amount in the range of 50 to 95 parts by weight with respect to 100 parts by weight of the metal fine particles. It may be.

  The metal fine particle composition of the present invention may further contain a solvent. In this case, the solvent may be an alcohol solvent or an organic solvent containing as a main component one or more selected from the group consisting of terpineol, dihydroterpineol, terpinyl acetate and dihydroterpinyl acetate. There may be.

  In the metal fine particle composition of the present invention, the metal fine particles may be metal fine particles containing nickel obtained by microwave irradiation in a liquid phase.

The method for producing a metal fine particle composition of the present invention includes a first step of obtaining a complexing reaction liquid by heating a mixture of nickel formate, copper formate and primary amine to a temperature in the range of 100 ° C. to 165 ° C. ,
A second step of heating the complexing reaction solution to a temperature of 170 ° C. or higher by microwave irradiation to obtain a metal fine particle slurry containing nickel and copper. And in the manufacturing method of this metal microparticle composition, in the said 2nd process, it heats in the state which made abietic acid exist in the said complexing reaction liquid.

  The metal fine particle composition of the present invention contains abietic acid having a strong agglomeration suppressing action and an oxidation resistance, so that even if it is a fine metal fine particle having a particle diameter of 150 nm or less, the agglomeration is suppressed, An aggregate of metal fine particles having a sharp particle size distribution in which particles are dispersed can be obtained. In addition, since the metal fine particle composition of the present invention suppresses the oxidation of the metal fine particles, for example, a sintered body obtained by performing a heat treatment can achieve high conductivity.

It is a figure which shows the structure of a nickel complex, (a) shows a bidentate coordination, (b) shows a monodentate coordination, (c) shows the state which the carboxylate ion coordinated to the outer sphere, respectively. 4 is a view showing an SEM photograph of the metal fine particle composition obtained in Example 2. FIG. It is a figure which shows the SEM photograph which baked the metal fine particle composition obtained in Example 2. FIG.

[Metal fine particle composition]
The metal fine particle composition of the present embodiment contains the component (A) and the component (B). The component (A) is fine metal particles having a particle diameter of 1 to 150 nm containing nickel, and the component (B) is abietic acid.

[Metal fine particles]
The metal fine particles used in the present embodiment contain nickel. The content of nickel may be appropriately selected according to the purpose of use. Examples of metals other than nickel include titanium, cobalt, copper, chromium, manganese, iron, zirconium, tin, tungsten, molybdenum, vanadium, and the like. Base metals such as gold, silver, platinum, palladium, iridium, osmium, ruthenium, rhodium and rhenium. Among these, for example, metal fine particles containing titanium, cobalt, copper, gold, silver, platinum and the like are preferable. Among these, metal fine particles that can be produced by microwave irradiation in the liquid phase, which will be described later, are particularly preferred. As the metal species in that case, nickel is an essential component, for example, cobalt, copper, gold, Silver, platinum, etc. are mentioned. The fine metal particles may contain the above metal elements alone or in combination of two or more, and may contain elements other than metal elements such as hydrogen, carbon, nitrogen, sulfur, etc. An alloy may be used. Furthermore, the metal fine particles may be composed of a single metal fine particle, or may be a mixture of two or more kinds of metal fine particles.

  The metal fine particles used in the present embodiment preferably contain 5 to 100 parts by mass of nickel element with respect to 100 parts by mass of metal fine particles. In addition, when the metal fine particles used in this embodiment are imparted with high conductivity, for example, from the viewpoint of being inexpensive and excellent in conductivity and migration resistance, the amount of copper element is preferably set to 100 mass of metal fine particles. It is good to set it as 50 mass parts or more with respect to a part. However, in such an embodiment, for example, copper oxide is easily formed by storage in the air or heat treatment, so the amount of nickel element is preferably 5 parts by mass or more with respect to 100 parts by mass of the metal fine particles. Preferably the production of copper oxide can be suppressed by setting it to 25 parts by mass or more, more preferably 30 parts by mass or more. In this case, from the viewpoint of achieving both high conductivity and oxidation resistance, the amount of nickel element is preferably 5 to 50 parts by mass, more preferably 25 to 50 parts by mass, most preferably 100 parts by mass of the metal fine particles. The amount of copper element is preferably in the range of 30 to 50 parts by mass, and the amount of copper element is preferably 50 to 95 parts by mass, more preferably 50 to 75 parts by mass, and most preferably 50 to 70 parts by mass. .

  When the metal fine particles used in the present embodiment contain copper, for example, the metal fine particles may have a double structure including copper in the center and a copper-nickel alloy in the periphery (outermost layer), The whole may be a solid solution of copper and nickel. In any case, for example, copper oxide is easily formed by storage in the air or heat treatment, and therefore, the formation of copper oxide is suppressed by blending abietic acid described later.

  The particle diameter of the metal fine particles is selected from a range of 1 to 150 nm. In the present embodiment, an excellent dispersion effect can be obtained even for metal fine particles having a particle diameter of 100 nm or less that are likely to cause aggregation. In other words, since a high aggregation suppressing effect is obtained, for example, it is more preferable to target metal fine particles having a particle diameter of 100 nm or less. From another viewpoint, the average particle size of the metal fine particles is preferably in the range of 10 to 120 nm, more preferably in the range of 20 to 100 nm.

[Abietic acid]
Abietic acid has three ring structures, a conjugated double bond, and a carboxyl group, and has a bulky structure rich in reactivity. These ring structures-carboxyl groups may be involved in the dispersing action. That is, the ring structure-carboxyl group causes an interaction with the metal fine particles, and the presence of abietic acid in the vicinity of the metal fine particles changes the electrical properties of the surface of the metal fine particles, or It is considered that the cohesion between the metal fine particles is suppressed due to a particular obstacle, and further, the dispersibility is imparted by the affinity with the solvent arbitrarily mixed in the metal fine particle composition. Here, as the interaction, for example, an ionic bond, a covalent bond, an electrostatic bond, a coordination bond, a hydrogen bond, and the like can be considered. Abietic acid is considered to exhibit oxidation resistance because the presence of copper changes the copper oxide on the surface of the metal fine particles to abienite copper.

  In the metal fine particle composition of the present embodiment, the content of abietic acid is in the range of 0.1 to 40 parts by mass, preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the metal fine particles. When the content of abietic acid with respect to 100 parts by mass of the metal fine particles is less than 0.1 parts by mass, the dispersibility of the metal fine particles tends to decrease, and when it exceeds 40 parts by mass, aggregation tends to occur. Moreover, when it is desired to suppress the oxidation of the metal fine particles, the amount of abietic acid is preferably 1 part by mass or more with respect to 100 parts by mass of the metal fine particles.

  Abietic acid can also be used in combination with other dispersible compounds as long as the effects of the invention are not impaired.

  Moreover, the metal fine particle composition of this Embodiment may contain the solvent as an arbitrary component. As the 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, and the like can be used. Specific examples of preferred solvents include isopropanol, tetraethylene glycol, n-octyl ether and the like. Moreover, as will be described later, the primary amine used for the liquid phase synthesis of the metal fine particles can be used as a solvent as it is.

  As the solvent other than the above, for example, an organic solvent containing as a main component one or more selected from the group consisting of terpineol, dihydroterpineol, terpinyl acetate and dihydroterpinyl acetate is preferable, and more preferably these are in the solvent. It is good to contain 95 weight% or more of 1 or more types of these. Since these organic solvents have relatively good solubility in organic binders such as ethyl cellulose, they are advantageous for applications such as conductive pastes. These organic solvents have a boiling point in the range of 200 to 300 ° C. and have an appropriate viscosity. For example, the metal fine particle composition of the present embodiment is made into a paste to sinter the metal fine particles. It is advantageously used for applications such as wiring materials. In the application through the process of sintering such metal fine particles, for example, after the metal fine particles are heat-treated at about 200 to 300 ° C., organic substances present on the surface of the metal fine particles are once eluted in the solvent. The organic substance can be discharged out of the system together with the solvent. Therefore, it is considered that the obtained sintered body has high conductivity without interfering with the fusion of the metal fine particles. In addition, content of a solvent can be suitably selected according to the use.

[Production Method of Metal Fine Particle Composition]
The metal fine particle composition according to the present embodiment can be produced by blending the component (A) metal fine particles with the component (B) abietic acid at the predetermined mass ratio. The method of blending abietic acid into the metal fine particles is not particularly limited. For example, a) a method in which a predetermined amount of abietic acid is mixed and kneaded and dispersed in the metal fine particles, and b) metal fine particles are synthesized by a liquid phase method. A method of adding a predetermined amount of abietic acid into the liquid phase before or after, c) mechanically crushing the metal fine particles using a dispersing machine such as a high-pressure homogenizer, and abietic acid is placed before or after the crushing. Various methods such as a method of adding and dispersing a fixed amount are included. Since abietic acid is a solid (powder) at room temperature, it may be mixed with metal fine particles as it is, or may be mixed with metal fine particles in a state of being dissolved in an arbitrary solvent.

  After applying abietic acid to the metal fine particles, it is preferable to remove excess abietic acid by washing. The washing can be performed using, for example, an alcohol solvent such as isopropanol.

  The metal fine particle contained in the metal fine particle composition of the present invention is not particularly limited as long as it contains the above nickel, and further contains the above-exemplified metal species as necessary, but the effect of abietic acid is not limited. In order to fully exhibit, it is preferable that it is a metal microparticle with a particle diameter of 150 nm or less and a narrow particle size distribution (for example, CV value is 0.2 or less). Metal fine particles having such a particle size distribution can be produced by microwave irradiation in the liquid phase. Hereinafter, in the method b), a case where a predetermined amount of abietic acid is added to a liquid phase before synthesizing nickel fine particles as metal fine particles by a liquid phase method is taken as a representative example, and the metal according to the present embodiment The method for producing the fine particle composition will be described in detail.

The metal fine particle composition containing nickel includes the following first step and second step;
A first step of obtaining a complexing reaction solution by heating a mixture containing nickel carboxylate and a primary amine to a temperature in the range of 100 ° C. to 165 ° C. (complexing reaction solution producing step); and
Second step of obtaining a nickel fine particle slurry by 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 (nickel fine particle slurry producing step) ,
It can prepare by the liquid phase method by microwave irradiation containing. Here, in a 2nd process, it heats in the state which made abietic acid exist in a complexing reaction liquid. Abietic acid can be blended at any timing of the step of preparing the mixture, the step of the mixture, or the step of the complexing reaction solution before heating in the second step at the latest. In contrast to the metallic nickel fine particles produced in this way, the abietic acid of the present embodiment exhibits a very excellent dispersion effect as shown in the examples described later. The “nickel fine particles” may be nickel alloy fine particles containing a metal other than nickel. In this case, examples of metals other than nickel include copper and cobalt.

<First step; complexing reaction solution generation step>
In the first step, first, a mixture of nickel carboxylate and primary amine is prepared. As described above, in this step, abietic acid can be added at the stage of preparing the mixture or at the stage of the mixture. Therefore, the mixture may contain abietic acid together with nickel carboxylate and primary amine.

(Nickel carboxylate)
The nickel carboxylate (nickel salt of carboxylic acid) is not limited to the type of carboxylic acid. For example, the carboxyl group may be a monocarboxylic acid having one carboxyl group, or a carboxylic acid having two or more carboxyl groups. It may be. Moreover, acyclic carboxylic acid may be sufficient and cyclic carboxylic acid may be sufficient. As such nickel carboxylate, nickel acyclic monocarboxylate can be preferably used, and among nickel acyclic monocarboxylate, nickel formate, nickel acetate, nickel propionate, nickel oxalate, benzoic acid It is more preferable to use nickel or the like. By using these nickel acyclic monocarboxylates, the resulting nickel fine particles are less likely to have a variation in shape and are easily formed in a uniform shape. The nickel carboxylate may be an anhydride or a hydrate.

In addition, it is possible to use inorganic salts such as nickel chloride, nickel nitrate, nickel sulfate, nickel carbonate, nickel hydroxide instead of nickel carboxylate, but in the case of inorganic salts, dissociation (decomposition) is high temperature. In the process of reducing the dissociated nickel ions (or nickel complex), heating at a higher temperature is required, which is not preferable. It is also possible to use nickel salts composed of organic ligands such as Ni (acac) ₂ (β-diketonato complex) and nickel stearate, but using these nickel salts increases the raw material cost. It is not preferable.

(Primary amine)
The primary amine can form a complex with nickel ions, and effectively exhibits a reducing ability for nickel complexes (or nickel ions). On the other hand, secondary amines have great steric hindrance and may hinder the good formation of nickel complexes. Since tertiary amines do not have the ability to reduce nickel ions, none can be used alone. When these are used, they may be used in combination as long as the shape of the metallic nickel fine particles to be produced is not hindered. 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. In addition, even if it is a primary amine solid at normal temperature, there is no particular problem as long as it is liquid by heating at 100 ° C. or higher, 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. Aliphatic primary amines can control the particle diameter of nickel fine particles produced by adjusting the length of their carbon chains, for example, producing nickel fine particles having an average particle diameter in the range of 1 nm to 150 nm. This is advantageous. From the viewpoint of controlling the particle diameter of the nickel fine particles, the aliphatic primary amine is preferably selected from those having about 6 to 20 carbon atoms. The larger the carbon number, the smaller the particle size of the nickel fine particles obtained. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, laurylamine and the like. For example, oleylamine exists in a liquid state under the temperature conditions in the nickel fine particle production process, and therefore the reaction can proceed efficiently in a homogeneous solution.

Since the primary amine functions as a surface modifier during the production of the nickel fine particles, secondary aggregation can be suppressed even after removal of the primary amine. In addition, 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 generated nickel fine particles and the solvent or unreacted primary amine after the reduction reaction. . Further, the primary amine is preferably one having a boiling point higher than the reduction temperature from the viewpoint of ease of reaction control when the nickel complex is reduced to obtain nickel fine particles. That is, the aliphatic primary amine preferably has a boiling point of 180 ° C. or higher, more preferably 200 ° C. or higher, and preferably has 9 or more carbon atoms. Here, for example, the boiling point of aliphatic amine [C ₉ H ₂₁ N (nonylamine)] having 9 carbon atoms is 201 ° C. The amount of primary amine is preferably 2 mol or more, more preferably 2.2 mol or more, and more preferably 4 mol or more with respect to 1 mol of nickel. When the amount of primary amine is less than 2 mol, it is difficult to control the particle diameter of the obtained 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.

(Organic solvent)
In the first step, an organic solvent other than the primary amine may be newly added in order to allow the reaction in the homogeneous solution to proceed more efficiently. When an organic solvent is used, the organic solvent may be mixed simultaneously with the nickel carboxylate and the primary amine. However, when the organic solvent is added after first mixing the nickel carboxylate and the primary amine to form a complex, It is more preferable because it efficiently coordinates to a nickel atom. 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 1-octanol, tetraethylene glycol, n-octyl ether, and the like.

(Complex formation)
A divalent nickel ion is known as a ligand-substituted active species, and the ligand of the complex to be formed may easily change in complex formation by ligand exchange depending on temperature and concentration. For example, in step of heat treating the mixture of nickel carboxylate and primary amine to obtain a reaction solution, considering the steric hindrance of the carbon chain length of the amine or the like used, for example, as shown in FIG. 1, a carboxylate ion (R ₁ COO, R ₂ COO) may be coordinated by either bidentate coordination (a) or monodentate coordination (b), and when the amine concentration is excessive, carboxylate ions are present in the outer sphere. There are at least three possibilities of (c). In order to obtain a homogeneous solution at the target reaction temperature (reduction temperature), at least one of the ligands of at least A, B, C, D, E, and F in FIGS. The location needs to be coordinated by a primary amine. In order to take this state, it is necessary that the primary amine is excessively present in the reaction solution, and it is preferable that at least 2 mol per 1 mol of nickel ions is present, and 2.2 mol or more exist. It is more preferable that 4 mol or more is present.

  Although this complex formation reaction can proceed even at room temperature, the reaction is carried out by heating to a temperature in the range of 100 ° C. to 165 ° C. in order to perform a sufficient and more efficient complex formation reaction. This heating is particularly advantageous when nickel carboxylate hydrate such as nickel formate dihydrate or nickel acetate tetrahydrate is used as nickel carboxylate. The heating temperature is preferably a temperature exceeding 100 ° C., more preferably a temperature of 105 ° C. or more, so that the ligand substitution reaction between the coordinating water coordinated with nickel carboxylate and the primary amine is efficient. The water molecule as the complex ligand can be dissociated, and the water can be discharged out of the system, so that the complex with the amine can be efficiently formed. For example, nickel formate dihydrate has a complex structure in which two coordination waters and two formate ions as bidentate ligands exist at room temperature. In order to efficiently form a complex by substituting a ligand for a primary amine, it is preferable to dissociate the water molecule as the complex ligand by heating at a temperature higher than 100 ° C. In addition, the heat treatment in the complex formation reaction between nickel carboxylate and primary amine is surely separated from the subsequent heat reduction process by microwave irradiation of the nickel complex (or nickel ion) to complete the complex formation reaction. In view of the above, the temperature is set to the upper limit temperature or lower, preferably 160 ° C. or lower, more preferably 150 ° C. or lower.

  The heating time can be appropriately determined according to the heating temperature and the content of each raw material, but is preferably 10 minutes or more from the viewpoint of completing the complex formation reaction. There is no upper limit on the heating time, but heat treatment for a long time is useless from the viewpoint of saving energy consumption and process time. 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.

  The complex formation reaction between nickel carboxylate and primary amine can be confirmed by a change in the color of the solution when a solution obtained by mixing nickel carboxylate and primary amine in an organic solvent is heated. . In addition, this complex formation reaction is carried out by measuring the absorption maximum wavelength of the absorption spectrum observed in the wavelength region of 300 nm to 750 nm using, for example, an ultraviolet / visible absorption spectrum measuring apparatus, and measuring the maximum absorption wavelength of the raw material (for example, nickel formate). In dihydrate, the maximum absorption wavelength is 710 nm, and in nickel acetate tetrahydrate, the maximum absorption wavelength is 710 nm.) The shift of the complexing reaction solution (the maximum absorption wavelength shifts to 600 nm) is observed. Can be confirmed.

  In addition, complex formation of metal ions other than nickel ions (for example, copper ions) can also be performed according to the above conditions.

  After the complex formation between nickel carboxylate and primary amine is performed, the resulting reaction solution is heated by microwave irradiation to reduce the nickel ions of the nickel complex as described below. At the same time, the carboxylate ions coordinated to the metal are decomposed, and finally metal nickel fine particles containing nickel having an oxidation number of 0 are generated. In general, nickel carboxylate is hardly soluble under conditions other than using water as a solvent, and a solution containing nickel carboxylate needs to be a homogeneous reaction solution as a pre-stage of the heat reduction reaction by microwave irradiation. On the other hand, the primary amine used in the present embodiment is liquid under the operating temperature conditions, and is considered to be liquefied by coordination with nickel ions to form a homogeneous reaction solution.

<Second step; nickel fine particle slurry generation step>
In this step, the complexing reaction solution obtained by the complexation reaction between nickel carboxylate and primary amine is heated to a temperature of 170 ° C. or higher by microwave irradiation to reduce nickel ions in the complexing reaction solution. To obtain a nickel fine particle slurry. The temperature for heating by microwave irradiation is preferably 180 ° C. or higher, more preferably 190 ° C. or higher, from the viewpoint of suppressing variation in the shape of the obtained 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. The heating temperature can be appropriately adjusted depending on, for example, the type of nickel carboxylate and the use of an additive that promotes the nucleation of nickel fine particles. And in a nickel fine particle slurry production | generation process, it heats in the state which made abietic acid exist in a complexing reaction liquid. Abietic acid may be added to the complexing reaction solution before heating by microwave irradiation.

  In this step, since microwaves penetrate into the reaction solution, uniform heating is performed, and energy can be directly applied 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 order to produce nickel fine particles having a uniform particle size, the nickel complex is uniformly and sufficiently produced in the complexing reaction liquid production step (step in which the nickel complex is produced), which is the first step, In the heat treatment by microwave irradiation in the second step, it is necessary to simultaneously generate and grow nickel (zero-valent) nuclei generated by reduction of the nickel complex (or nickel ion). In other words, by adjusting the heating temperature in the complexing reaction liquid production step within the above specific range and ensuring that it is lower than the microwave heating temperature in the nickel fine particle slurry production step, the particle size and shape are adjusted. Particles are easily generated. For example, if the heating temperature is too high in the complexing reaction liquid generation process, the formation of nickel complex and the reduction reaction to nickel (zero valence) proceed simultaneously, and different metal species are generated. There is a possibility that it is difficult to generate particles having a uniform particle shape. In addition, if the heating temperature of the nickel fine particle slurry generation process is too low, the reduction reaction rate to nickel (zero valence) is slowed and the generation of nuclei is reduced, so that not only the particles are enlarged, but also in terms of the yield of nickel fine particles Is also not preferred.

  The nickel fine particle slurry obtained by heating by microwave irradiation can be directly used as the nickel fine particle composition. Further, for example, the nickel fine particle slurry is allowed to stand and be separated, and the supernatant liquid is removed. Then, the nickel fine particle slurry is washed with an appropriate solvent and dried to obtain nickel fine particles. In the nickel fine particle slurry production step, the organic solvent described above may be added as necessary. As described above, the primary amine used for the complex formation reaction is preferably used as it is as the organic solvent.

  As described above, a nickel fine particle composition having an average particle diameter of 150 nm or less can be prepared. Note that not only the nickel fine particle composition but also a metal fine particle composition containing other metal species can be produced according to the above method.

  For example, when the fine metal particle composition according to the present embodiment contains fine metal particles of an alloy of nickel and copper, in the first step, a mixture of nickel carboxylate and primary amine and a copper salt added may be used. That's fine. When it is desired to suppress the formation of copper oxide in the metal fine particles of an alloy of nickel and copper, the following manufacturing method is preferable.

(Example of Ni-Cu alloy production method)
A first step of obtaining a complexing reaction solution by heating a mixture of nickel formate, copper formate and primary amine to a temperature within the range of 100 ° C. to 165 ° C., and this complexing reaction solution by microwave irradiation Heating to a temperature of 170 ° C. or higher to obtain a metal fine particle slurry containing nickel and copper. And in a 2nd process, it heats in the state which made abietic acid exist in the said complexing reaction liquid. Here, the abietic acid is blended at any timing of the step of preparing the mixture, the step of the mixture, or the step of the complexing reaction solution before heating in the second step at the latest.

  It is preferable to mix | blend abietic acid with the ratio of 0.1 mass part or more with respect to a total of 100 mass parts of the nickel element and copper element of metal conversion in nickel formate and copper formate. If the blending ratio of abietic acid is less than 0.1 parts by mass, the blending effect may not be sufficiently obtained. On the other hand, the upper limit of the mixing ratio of abietic acid is not particularly limited. However, as the ratio increases, abietic acid is likely to be precipitated.

  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]
The average particle size was measured by taking a photograph of the sample with an SEM (scanning electron microscope), randomly extracting 200 samples from the sample, obtaining each particle size, and calculating the average particle size. The CV value (coefficient of variation) was calculated by (standard deviation) / (average particle diameter). In addition, it shows that a particle diameter is so uniform that a CV value is small.

[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 metal fine particles are dispersed in isopropanol is diluted to a predetermined concentration, and dispersed in the particle size distribution measuring apparatus with ultrasonic waves for 5 minutes, and volume distribution is measured. A comparative evaluation of dispersibility was performed based on the results of the particle size distribution.

[5% heat shrink temperature]
The 5% heat shrink temperature is obtained by placing a sample in a 5Φ × 2 mm cylindrical molding machine and producing a molded product obtained by press molding, and then heating it in an atmosphere of nitrogen gas (containing 3% hydrogen gas). The temperature was 5% thermal yield measured by an analyzer (TMA).

(Synthesis Example 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 fine particle slurry 1.

  After separating the metal fine particle slurry 1 and removing the supernatant, it was washed with toluene, further washed with isopropanol, and then dried in a vacuum dryer maintained at 60 ° C. for 6 hours, Metal fine particles 1 (nickel content: 98% by mass, average particle size: 100 nm, CV value: 0.17, 5% heat shrinkage temperature: 295 ° C.) were obtained. As a result of elemental analysis, it was C; 0.5, N; 0.026, O; 2.2 (unit: mass%).

(Reference Example 1)
The metal fine particle slurry 1 obtained in Synthesis Example 1 was allowed to stand and separated, and after removing the supernatant, it was washed with toluene, and further washed with isopropanol. Name: Starburst) was used to prepare slurry solution 1 (solid content concentration: 10 wt%) in which metal fine particles were dispersed under a pressure of 200 MPa. The particle size distribution of the slurry solution 1 was measured. The results of the volume distribution were as follows.
D ₁₀ ; 0.115 μm, D ₃₀ ; 0.177 μm, D ₅₀ ; 0.238 μm, D ₉₀ ; 0.479 μm, D ₉₉ ; 1.151 μm

[Example 1]
10 g of the slurry solution 1 prepared in Reference Example 1 was collected, 0.3 g of abietic acid was added thereto, stirred for 15 minutes, and then washed with isopropanol to obtain a metal fine particle composition 1. The particle size distribution of the metal fine particle composition 1 was measured. The results of the volume distribution were as follows.
D ₁₀ ; 0.074 μm, D ₃₀ ; 0.111 μm, D ₅₀ ; 0.149 μm, D ₉₀ ; 0.300 μm, D ₉₉ ; 0.669 μm

[Example 2]
To 384 g of oleylamine, 17.79 g of nickel formate dihydrate and 26.7 g of copper formate tetrahydrate were added and heated at 120 ° C. for 20 minutes under a nitrogen flow to obtain nickel and copper salts. It was dissolved to obtain a complexing reaction solution. Next, 1.48 g of abietic acid and 290 g of 1-octanol were added to the complexing reaction solution, and the mixture was heated at 190 ° C. for 5 minutes using a microwave to obtain a metal fine particle slurry 2.

  After the metal fine particle slurry 2 is left and separated, the supernatant is removed, washed with methanol, and then dried in a vacuum dryer maintained at 70 ° C. for 6 hours to obtain the metal fine particle composition 2 (average particle Diameter: 10 nm, CV value: 0.12, 5% heat shrinkage temperature: 250 ° C.). The content of Ni and Cu in the metal fine particle composition 2 was 98% by mass, and the content ratio of Ni and Cu was Ni: Cu = 40: 60 (unit: mass%). An SEM photograph of the obtained metal fine particle composition 2 is shown in FIG.

  Identification of the obtained metal fine particle composition 2 was performed using a powder X-ray diffractometer (XRD) (trade name; RINT2500, manufactured by Rigaku Corporation). As a result of X-ray analysis, the obtained powder has peaks of crystal faces (111), (200), (220) of a solid solution of nickel and copper, and thus the obtained powder has nickel having a face-centered cubic structure (fcc) It was confirmed that it was a solid solution of copper, and copper oxide was not confirmed.

  After adding 400 g of dihydroterpinyl acetate to 20 g of the obtained metal fine particle composition 2, using a dispersion apparatus (trade name: Cleamix, manufactured by M Technique Co., Ltd.), 20 rpm at a rotation speed of 6,000 rpm. Dispersion was performed for a minute. Then, it concentrated by centrifugation (rotation speed 3,000 rpm, 10 minutes), and prepared slurry solution 2 '(solid content concentration 80 wt%) in which metal fine particle composition 2 was dispersed.

  Two pairs of glass plates were prepared, and Sample 2 was prepared by rubbing the slurry solution 2 'with two pairs of glass plates.

  Sample 2 was baked in hydrogen gas at 250 ° C. for 30 minutes. The SEM photograph at that time is shown in FIG. By firing at 250 ° C. for 30 minutes, it was confirmed that sintering was progressing, and conduction was also confirmed.

(Reference Example 2)
In Example 2, metal fine particles (mass ratio of Ni and Cu [%]; Ni: Cu = 40: 60, average particle size) were obtained in the same manner as in Example 2 except that 1.48 g of abietic acid was not used. Diameter: 10 nm, CV value: 0.12, 5% heat shrinkage temperature: 250 ° C.).

  As a result of X-ray analysis of the obtained metal fine particles, the obtained powder has a face-centered cubic structure (peak) of crystal planes (111), (200), and (220) of a solid solution of nickel and copper, respectively. fcc) was confirmed to be a solid solution of nickel and copper, but some peaks related to copper oxide were also confirmed.

[Example 3]
To 4280 g of oleylamine, 310 g of nickel formate dihydrate and 181 g of copper formate tetrahydrate are added and heated at 120 ° C. for 40 minutes under a nitrogen flow to dissolve the nickel salt and the copper salt to form a complex. The reaction solution was obtained. Next, 15 g of abietic acid and 3230 g of 1-octanol were added to the complexing reaction solution, and the mixture was heated at 190 ° C. for 5 minutes using a microwave to obtain a metal fine particle slurry 3.

  The fine metal particle slurry 3 was allowed to stand and separated, the supernatant was removed, washed with hexane and methanol, and then dried in a vacuum dryer maintained at 60 ° C. for 6 hours to obtain the fine metal particle composition 3 (average particle size) 40 nm, CV value; 0.16, 5% heat shrink temperature; 265 ° C.). The content of Ni and Cu in the metal fine particle composition 3 was 98% by mass, and the content ratio of Ni and Cu was Ni: Cu = 67: 33 (unit: mass%).

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 (8)

The following components (A) and (B),
(A) metal fine particles having a particle diameter of 1 to 150 nm containing nickel, and (B) abietic acid,
Including
A metal fine particle composition obtained by blending the component (B) so as to fall within the range of 0.1 to 40 parts by mass with respect to 100 parts by mass of the component (A).   The metal fine particle composition according to claim 1, wherein the metal fine particles are an alloy of nickel and copper.   The metal fine particles are metal fine particles in which the amount of nickel element is in the range of 5 to 50 parts by weight and the amount of copper element is in the range of 50 to 95 parts by weight with respect to 100 parts by mass of the metal fine particles. Item 3. The metal fine particle composition according to Item 2.   The metal fine particle composition according to any one of claims 1 to 3, further comprising a solvent.   The metal fine particle composition according to claim 4, wherein the solvent is an alcohol solvent.   The metal fine particle composition according to claim 4, wherein the solvent is an organic solvent containing as a main component one or more selected from the group consisting of terpineol, dihydroterpineol, terpinyl acetate, and dihydroterpinyl acetate.   The metal fine particle composition according to any one of claims 1 to 6, wherein the metal fine particle is a metal fine particle containing nickel obtained by microwave irradiation in a liquid phase. A first step of heating a mixture of nickel formate, copper formate and primary amine to a temperature in the range of 100 ° C. to 165 ° C. to obtain a complexing reaction solution;
A second step of heating the complexing reaction liquid to a temperature of 170 ° C. or higher by microwave irradiation to obtain a metal fine particle slurry containing nickel and copper, and
In the second step, a method for producing a metal fine particle composition, wherein heating is performed in a state where abietic acid is present in the complexing reaction solution.