JP6373055B2 - Spherical composite copper fine particles containing ultrafine carbon fiber and method for producing the same - Google Patents

Description

  The present invention relates to spherical composite copper fine particles containing ultrafine carbon fibers useful for bonding materials, contact materials, and thick film pastes in electronic and electrical equipment, and a method for producing the same.

Copper powder has excellent electrical conductivity (1.68 × 10 ⁻⁸ Ω · m) and thermal conductivity, so in the field of electronic equipment, it is a thick film for manufacturing components such as electronic circuits and capacitor electrodes. It is used as a conductor and resistance paste. It is also used as a sliding material for electrical contacts.

  In recent years, in the field of power semiconductors and the like, a bonding material using copper powder has attracted attention as an alternative material for high-temperature solder mainly composed of lead, which has been widely used as a bonding material. However, when a bonding material using copper powder is used for the power semiconductor, cracking and peeling at the bonded portion due to the generation of thermal stress due to the difference in the coefficient of thermal expansion of the constituent materials is a problem.

  Currently, methods for producing copper powder include wet reduction by applying a reducing agent to an aqueous solution of a copper compound, a method of atomizing a molten copper metal with gas or water, and evaporating the copper melt in a vacuum to solidify it. And a method of spraying a copper compound solvent and thermally decomposing it are known.

  Here, in order to obtain a dense and uniform film, the copper powder in the field of electronic equipment is excellent in dispersibility and filling properties in paint, has few impurities, has a particle size of 50 to 20000 nm, and has a spherical shape. Spray pyrolysis methods are known.

  However, the production of copper powder in the spray pyrolysis method tends to cause fusion and sintering of copper particles during pyrolysis due to uneven atomized droplet concentration and turbulent gas flow. Further, in the cooling process and the collection process, there is a problem that the copper particles are deposited and deposited to form agglomerates, the product recovery rate is lowered, and the continuous operation becomes difficult.

  A method of segregating refractory metals and oxides on the surface of the particles (Patent Document 1) to prevent fusion and sticking of the generated copper particles has been studied, but metals and oxides for preventing fusion are: Since it becomes an impurity of copper particles, it is not preferable depending on the application field.

  As a method of solving such a problem, in order to further enhance the effect of coexistence of copper and other metals and carbon, particularly copper particles and carbon materials, copper particles and ultrafine carbon fibers such as carbon nanotubes are used. A combination with is proposed. For example, a high thermal conductivity composite material obtained by mixing copper powder and carbon nanotubes and compacted by hot pressing (Patent Document 2), a transition metal-coated carbon material obtained by attaching conductive copper fine particles to carbon nanotubes (Patent Document 3) ), Carbon composite plated electric wire (Patent Document 4) in which a metal core wire is subjected to composite electroplating of copper and ultrafine carbon fiber has been tried, but it is convenient and ultrafine carbon fiber that can be used in a wide range of applications. No spherical copper fine particles compounded with synthesizer.

JP-A-10-102108 JP-A-10-168502 International Publication No. 2009/038048 JP 2006-265667 A

  In order to solve the above problems, the present invention is excellent in dispersibility and filling properties in bonding materials, electrode materials, contact materials, wiring materials, etc. of electronic and electrical parts, and further, thermal stress, which is a problem when using metallic copper Spherical composite copper fine particles aiming at reduction of wear, improvement of wear resistance, and improvement of sinterability as a contact material, and providing spherical composite copper fine particles containing a specific amount of ultrafine carbon fibers inside and on the surface . Further, in the production of the spherical composite copper fine particles, the copper fine particles are prevented from sticking and agglomerating, and the recovery rate is improved.

The present invention relates to spherical composite copper fine particles that have solved the above problems with the following configuration, and a method for producing the same.
[1] Spherical composite copper fine particles containing ultra fine carbon fibers therein, wherein the ultra fine carbon fibers are 0.1 to 15.0 parts by mass with respect to 100 parts by mass of the spherical composite copper fine particles.
[2] The spherical composite copper fine particles according to [1] or [2] above, wherein the spherical composite copper fine particles have a particle size of 1 nm or more and less than 20000 nm.
[3] The ultrafine carbon fiber is a hollow fiber, the fiber length: L is 50 nm or more, the outer diameter: D is 5-40 nm, the inner diameter: d is 2-30 nm, and the aspect ratio (L / D) is 5 The spherical composite copper fine particles according to [1] or [2], which are 1000.
[4] (A) A step of obtaining a dispersion solution in which the ultrafine carbon fibers are dispersed after adding the ultrafine carbon fiber aggregate and the dispersing agent to the dispersion solvent;
(B) After mixing a copper compound with the obtained dispersion solution, dissolving the copper compound to obtain a mixture, and (C) atomizing the obtained mixture into fine droplets, Heating the transformed droplets at 1083 ° C. or higher in a reducing atmosphere;
In this order, containing ultrafine carbon fibers inside, spherical composite copper fine particles having 0.1 to 15.0 parts by mass of ultrafine carbon fiber with respect to 100 parts by mass of spherical composite copper fine particles Manufacturing method.
[5] Gas phase by a gas containing carbon using a catalyst in which the ultrafine carbon fiber contains at least one element selected from the group consisting of Fe, Co, Ni, Mo, Al, Mg, Zn, Ti and Si The method for producing spherical composite copper fine particles according to [4], which is produced by a growth method.
[6] The method for producing spherical composite copper fine particles according to the above [4] or [5], wherein the dispersant is carboxymethyl cellulose, naphthalene sulfonate, or polyvinyl pyrrolidone.
[7] The method for producing spherical composite copper fine particles according to any one of the above [4] to [6], wherein the dispersion solvent contains at least one selected from the group consisting of water and a polar organic solvent.
[8] In the step (C), the reducing atmosphere for heating the atomized droplets is at least one selected from the group consisting of nitrogen gas, carbon dioxide gas, ammonia gas, alcohol, hydrocarbon gas, and hydrogen gas. The method for producing spherical composite copper fine particles according to any one of [4] to [7] above.

  According to the present invention [1], in the joining material, electrode material, contact material, wiring material, etc. of electronic and electrical parts, it is excellent in dispersibility and filling properties, and furthermore, thermal stress reduction is a problem when using metallic copper. Further, it is possible to provide spherical composite copper fine particles aimed at improving wear resistance and improving the sinterability as a contact material.

  According to the present invention [4], spherical composite copper fine particles containing ultrafine carbon fibers inside and on the surface thereof are produced at a high recovery rate while preventing the adhesion and aggregation of the spherical composite copper fine particles during the production process. Can do.

2 is a scanning electron microscope (SEM) photograph of spherical composite copper fine particles produced in Example 1. FIG. 2 is a SEM photograph of spherical composite copper fine particles produced in Example 1. It is a SEM photograph after etching the spherical composite copper fine particle manufactured in Example 1 for 120 second with 35 mass% nitric acid aqueous solution. It is a SEM photograph after etching the spherical composite copper fine particle manufactured in Example 1 for 120 second with 35 mass% nitric acid aqueous solution. It is a SEM photograph after etching the spherical composite copper fine particle manufactured in Example 1 for 120 second with 35 mass% nitric acid aqueous solution. It is a SEM photograph after etching the spherical composite copper fine particle manufactured in Example 1 for 420 seconds with 35 mass% nitric acid aqueous solution. It is a SEM photograph after etching the spherical composite copper fine particle manufactured in Example 1 for 420 seconds with 35 mass% nitric acid aqueous solution. It is a SEM photograph of the used ultrafine carbon fiber.

  Hereinafter, the present invention will be specifically described based on embodiments. Unless otherwise indicated, “%” means “% by mass” unless otherwise specified.

(Spherical composite copper fine particles)
The spherical composite copper fine particles (hereinafter referred to as spherical composite copper fine particles) of the present invention contain ultrafine carbon fibers inside, and the ultrafine carbon fibers are 0.1 to 15.0 masses per 100 mass parts of the spherical composite copper fine particles. It is a part. The spherical composite copper fine particles of the present invention are excellent in dispersibility and filling properties in bonding materials, electrode materials, contact materials, wiring materials, etc. of electronic and electrical parts, and also reduce thermal stress, which is a problem when using metallic copper. It has combined effects such as improved wear resistance and excellent sinterability as a contact material. The spherical composite copper fine particles can also be used as an anti-settling agent for solder (for example, Sn—Ag—Cu-based) powder in a lead-free solder paste. The ultrafine carbon fibers contained in the spherical composite copper fine particles are considered to form a network structure inside the spherical composite copper fine particles, and to give the composite effect to the spherical composite copper fine particles. The ultrafine carbon fiber may be present on the surface of the spherical composite copper fine particles.

  Here, the spherical shape may be a substantially spherical shape, and the aspect ratio (major axis / minor axis) in the scanning electron micrograph of the spherical composite copper fine particles is 1.0 to 1.4. Say. The aspect ratio of the spherical composite copper fine particles is preferably 1.0 to 1.2, and more preferably a true sphere (the aspect ratio is 1.05 or less).

  The particle diameter of the spherical composite copper fine particles is preferably 1 nm or more and less than 20000 nm. When the particle diameter of the spherical composite copper fine particles exceeds 20000 nm, the sinterability may be reduced, and the sintered density may be difficult to increase. On the other hand, when the particle diameter of the spherical composite copper fine particles is less than 1 nm, the ultrafine carbon fiber diameter approaches the spherical composite copper fine particle diameter, it becomes difficult to form a fine carbon fiber diameter network structure, and it is difficult to exert the composite effect. Conceivable. The average particle size of the spherical composite copper fine particles is preferably 50 nm or more and less than 10,000 nm, and more preferably 100 nm or more and 5000 nm or less from the viewpoint of sinterability and composite effect. Here, the particle diameter is an average diameter (n = 50) of the long diameter (the longest diameter of the spherical composite copper fine particles) in the scanning electron micrograph of the spherical composite copper fine particles. The average particle diameter is an average diameter of the long diameter (the longest diameter of the spherical composite copper fine particles) in the scanning electron micrograph of the spherical composite copper fine particles (n = 50).

  The ultrafine carbon fiber contained in the spherical composite copper fine particles is not particularly limited, but is a hollow fiber, the fiber length: L is 50 nm or more, the outer diameter: D is 5-40 nm, the inner diameter: d is 2-30 nm, It is preferable that the aspect ratio (L / D) is 5 to 1000 because the ultrafine carbon fibers can easily form a network structure. Here, the ultrafine carbon fiber refers to a carbon fiber having an outer diameter of 100 nm or less.

The ultrafine carbon fiber is a single layer or multiple layers deposited and grown by arc decomposition of a carbon electrode or by pyrolyzing a gaseous carbon-containing compound on a catalyst heated to 500 ° C. or higher with the catalyst floating or fixed. Of these, an ultrafine carbon fiber having a graphite layer is preferred. The following four nanostructured carbon materials have been reported mainly from the shape, form, and structure of ultrafine carbon fibers.
<1> Multi-walled carbon nanotubes (graphite layer is multi-layer concentric cylindrical, non-fishbone)
For example, those described in JP-B-3-64606, JP-A-3-77288, and JP-A-2004-299986 <2> Cup-stacked carbon nanotubes (fishbone)
For example, JP 2003-073928 A, JP 2004-36099 A; US Pat. No. 4,855,091; Endo, Y. et al. A. Kim etc. : Appl. Phys. Lett. , Vol 80 (2002) 1267-, <3> Nodal carbon nanofiber (non-fishbone structure)
For example, J. et al. P. Pinheiro, P.M. Gadelle etc. : Carbon, 41 (2003) 2949-2959; E. Nolan, M .; J. et al. Schabel, D.M. C. Lynch: Carbon, 33 [1] (1995) 79-85. <4> Platelet-type carbon nanofiber (Trump shape)
For example, JP-A-2004-300631; Murayama, T .; maeda,: Nature, vol345 [No28] (1990) 791-793.

  In the present invention, any ultrafine carbon fiber having the above-described nanostructure may be used, but when the knot-shaped carbon nanofiber is defibrated and dispersed, the fiber is appropriately cut at the knot and the fiber length can be adjusted. Particularly preferred.

  The ultrafine carbon fiber is 0.1 to 15.0 parts by mass with respect to 100 parts by mass of the spherical composite copper fine particles, and in order to contain the fine carbon fiber only inside, it is 1 part by mass or more and less than 6 parts by mass. Preferably, it is more than 2 parts by mass and less than 6 parts by mass. When the content of the ultrafine carbon fiber is 0.1 parts by mass or more, the composite effect is easily exhibited. In addition, when the ultrafine carbon fiber is 2 parts by mass or more with respect to 100 parts by mass of the spherical composite copper fine particles, the ultrafine carbon fiber present in the spherical composite copper fine particles can be easily observed with the SEM, and the above composite effect is obtained. It becomes easier to demonstrate. Furthermore, in order to contain the ultrafine carbon fiber in the inside and the surface of the spherical composite copper fine particles, the amount is preferably 6.0 to 20.0 parts by mass, and more preferably 7.0 to 15.0 parts by mass. 7.5 to 12.0 parts by mass is even more preferable. On the other hand, when the content of the ultrafine carbon fiber exceeds 15.0 parts by mass, the conductivity and sinterability of the spherical composite copper fine particles are remarkably lowered, and it becomes difficult to obtain spherical particles. From the viewpoint of the thermal expansion coefficient of the spherical composite copper fine particles, the content of the ultrafine carbon fiber is preferably 5.0 parts by mass or more, more preferably 6.0 parts by mass or more, and 7.0 masses. More preferably, it is at least part. On the other hand, from the viewpoint of the color of the spherical composite copper fine particles, since it is slightly blackish if it is 12.0 parts by mass or more, from the viewpoint of obtaining spherical composite copper fine particles of metallic luster, it is preferably 15 parts by mass or less, More preferably, it is 10 parts by mass or less.

[Method for producing spherical composite copper fine particles]
The spherical composite copper fine particles can be produced, for example, by spray pyrolysis. According to the method for producing the spherical composite copper fine particles of the present invention described below, the adhesion and aggregation of the spherical composite copper fine particles during the production process are prevented. However, it can be manufactured at a high recovery rate.

The method for producing spherical composite copper fine particles containing the ultra fine carbon fiber of the present invention inside, and the ultrafine carbon fiber is 0.1 to 15.0 parts by mass with respect to 100 parts by mass of the spherical composite copper fine particles,
(A) After adding the ultrafine carbon fiber aggregate and the dispersant to the dispersion solvent, obtaining a dispersion solution in which the ultrafine carbon fibers are dispersed;
(B) After mixing a copper compound with the obtained dispersion solution, dissolving the copper compound to obtain a mixture, and (C) atomizing the obtained mixture into fine droplets, Heating the transformed droplets at 1083 ° C. or higher in a reducing atmosphere;
Are included in this order.

  Here, first, a method for producing the ultrafine carbon fiber used in the step (A) will be described.

<Method for producing ultrafine carbon fiber>
Known methods for producing ultrafine carbon fibers include arc discharge method, vapor phase growth method, laser method, mold method, etc., but vapor phase growth method using a catalyst contributes to the shape and mass productivity of ultrafine carbon fiber. It is preferable because it is excellent. This catalyst preferably contains at least one element selected from the group consisting of Fe, Co, Ni, Mo, Al, Mg, Zn, Ti and Si. Specifically, Fe, Co, Ni, Mo, etc. A composite oxide catalyst made of an oxide of Al, Mg, Si, Zn, Ti or the like on which the metal nanoparticles are supported is used. The feed gas used in the gas phase method is preferably a gas containing carbon. As the gas containing carbon, for example, hydrocarbon gas such as methane, ethylene, acetylene and toluene, alcohols such as methanol and ethanol, and CO gas are generally used. In some cases, carbon-containing gas containing hydrogen gas is used. used. The nodal carbon nanofibers are obtained by vapor phase growth using a catalyst particle in which magnesium is replaced by a solid solution with an oxide having a spinel crystal structure of cobalt, and supplying a mixed gas containing CO and H ₂ to the catalyst particle. Can be manufactured easily. In addition, the ultrafine carbon fiber obtained by this manufacturing method is usually an aggregate.

<Process (A)>
In the step (A), after adding the ultrafine carbon fiber aggregate and the dispersant to the dispersion solvent, a dispersion solution in which the ultrafine carbon fibers are dispersed is obtained. In order to disperse the ultrafine carbon fibers in the dispersion solvent, first, the ultrafine carbon fiber aggregate is opened in the dispersion solvent and then dispersed. A dispersant is added to the dispersion solvent so that the opened ultrafine carbon fibers do not become aggregates (aggregates) again. The ultrafine carbon fiber aggregate is preferably 1 to 6 parts by mass with respect to 100 parts by mass of the dispersion solution from the viewpoint of dispersibility of the ultrafine carbon fibers, and 3 to 6 parts by mass from the viewpoint of productivity. More preferred.

  The dispersion solvent is not particularly limited, but is preferably at least one selected from the group consisting of water and polar organic solvents, and polar solvents such as water and alcohols are usually used. In addition, aromatic compounds such as xylene and toluene, and aprotic polar solvents such as N-methyl-2-pyrrolidone and dimethyl sulfoxide can also be used.

  Dispersants include surfactants such as sodium oleate, polyoxyethylene carboxylic acid ester, monoalcohol ester, ferrocene derivative; pyrene compound (pyrene ammonium), porphyrin compound (ZnPP, Hemin, PPEt), polyfluorene, cyclic glucan Cyclic / polycyclic aromatic compounds such as folic acid, lactam compound (—CONH—), and lactone compound (—CO—O—); linear conjugated polymers such as polythiophene, polyphenylene vinylene, and polyphenylene ethylene; Cyclic amides such as PVP); polystyrene sulfonic acid; polymer micelles; water-soluble pyrene-containing polymers; fructose, polysaccharides (such as carboxymethylcellulose), saccharides such as amylose; inclusion complexes such as lataxane; cholic acid analogs. When the dispersion solvent is a polar solvent such as water or alcohol, carboxymethyl cellulose and naphthalene sulfonate are preferable, and when the dispersion solvent is a non-proto polar solvent, polyvinyl pyrrolidone (PVP) is preferable. The dispersant is preferably added in an amount of 1 part by mass or more and 90 parts by mass or less with respect to a total of 100 parts by mass of the ultrafine carbon fiber aggregate and the dispersant. More preferable.

  The opening and dispersion of the ultrafine carbon fiber aggregate can be performed by adding a dispersing agent and the ultrafine carbon fiber aggregate to a dispersion solvent and stirring the mixture with a homomixer, a trimix, or the like. In order to more effectively open and disperse ultrafine carbon fiber assemblies, beads mills, paint shakers, centrifugal ball mills, planetary ball mills, and vibrating ball mills that use ultrasonic vibration by vibration shock waves, impact of beads and balls, and shaking are used. Further, an attritor type high-speed ball mill, a roll mill using a shearing force, or the like can be used.

  Further, by subjecting the ultrafine carbon fiber aggregate to an oxidation treatment before dispersing the ultrafine carbon fiber aggregate, the ultrafine carbon fiber can be easily adapted to the dispersion solvent. As this oxidation treatment method, for example, an ultrafine carbon fiber aggregate is formed by liquid phase oxidation with nitric acid / sulfuric acid mixed solution, ozone, supercritical water, supercritical carbon dioxide gas, etc., or gas phase oxidation with atmospheric firing, oxygen plasma, etc. The method of giving a hydrophilic treatment is mentioned.

  In the step (A), graphite, graphene, carbon black, acetylene black, which is a carbon material other than the ultrafine carbon fiber, or a carbon precursor may be used in combination with the ultrafine carbon fiber. As the carbon precursor, , Coal tar, coal tar pitch, petroleum heavy oil, petroleum pitch, sugars such as sucrose (sucrose), polyhydric alcohol, (water-soluble) phenol resin, furan resin, lignin and the like.

<(B) Process>
In the step (B), the copper compound is mixed with the dispersion obtained in the step (A), and then the copper compound is dissolved to obtain a mixture.

The copper compound mixed in the dispersion solution is a soluble copper compound that dissolves in water as a dispersion solvent and a polar organic solvent, and includes copper nitrate (Cu (NO ₃ ) ₂ , CuNO ₃ ), copper acetate (Cu (CH ₃ COO). ), Cu (CH ₃ COO) ₂ ), copper sulfate (CuSO ₄ , Cu ₂ SO ₄ ), copper phosphate (Cu ₃ (PO ₄ ) ₂ , Cu ₃ PO ₄ ) and the like. Insoluble copper compounds, such as copper halides such as copper chloride (CuCl), can be used as long as they can be atomized into droplets in step (C) without any inconvenience even if undissolved copper compounds coexist. . The copper compound is made to have a copper content after decomposition of 0.1 to 15.0 parts by mass with respect to 100 parts by mass of the spherical composite copper fine particles.

  The method for mixing and dissolving the copper compound in the dispersion solution is not particularly limited, and may be a known technique such as propeller stirring.

<Process (C)>
In the step (C), the mixture obtained in the step (B) is atomized into fine droplets, and then the atomized droplets are heated in a reducing atmosphere at 1083 ° C. or higher.

The reaction in step (C), as a dispersion solution, a water dispersion ultrafine carbon fibers are dispersed, an example using a copper compound copper nitrate _{(Cu (NO 3) 2)} , guess. First, in the atomized mixture droplets, the dispersion solvent evaporates and copper nitrate ((Cu (NO ₃ ) ₂ )) crystal particle aggregates in which ultrafine carbon fibers are entangled are formed. When the temperature of the copper nitrate ((Cu (NO ₃ ) ₂ )) crystal particle aggregate exceeds 115 ° C. (melting point of stable trihydrate), which is the melting point of copper nitrate, the copper nitrate particle aggregate is melted. Then, ultrafine carbon fibers are dispersed in the copper nitrate melt particles. Next, when the copper nitrate melt particles in which the ultrafine carbon fibers are dispersed exceed the decomposition temperature of 170 ° C., the copper nitrate particles decompose into metal copper, and the porous composite in which the copper fine particles and the ultrafine carbon fibers are intertwined. It becomes. Furthermore, as the temperature of the porous composite approaches 1083 ° C., which is the melting point of copper, the copper fine particles are sintered and densified, and converted to pseudo spherical copper particles in which ultrafine carbon fibers are combined. When the pseudo-spherical copper particles combined with ultrafine carbon fibers reach a temperature exceeding the melting point of copper of 1083 ° C. or higher, preferably 1100 ° C. or higher, the copper particles melt. The production of spherical crystalline copper particles is facilitated. The above reaction formula is shown below.
Cu (NO ₃ ) ₂ (S) → Cu (NO ₃ ) ₂ (l) → Cu + 2NO ₂ + O ₂
(In the formula, (S) represents a solid, and (l) represents a liquid.)

  In addition to copper, alloying with a metal different from copper or addition compounding with an oxide of a metal different from copper can also be achieved. Metals different from copper include palladium, silver, gold, platinum, ruthenium, rhodium, iridium, zinc, iron, nickel, cobalt, aluminum, indium, bismuth, tin, germanium, gallium, tungsten, molybdenum, alkali metal, alkaline earth Similar metals. In the case of alloying with copper and a different metal, or adding and compounding with an oxide, heating is performed at a temperature higher than the decomposition temperature of each metal compound, preferably at or above the melting point of each metal compound. And composite with copper particles and alloy or oxide.

  As the atomization device that generates droplets from the mixture obtained in the step (B), a normal device such as a two-fluid atomizer, a centrifugal atomizer, or an ultrasonic atomizer can be used. In any of the above apparatuses, operation is performed at a temperature lower than the boiling point of the dispersion solvent that does not cause trouble such as clogging due to precipitation of copper nitrate crystals, or a high boiling polar dispersion solvent such as ethylene glycol is added. It is preferable.

  In the step (C), the temperature at which the atomized droplet is heated is preferably 1085 ° C. or higher, which is a temperature exceeding the copper melting point, as described above. The temperature for heating the atomized droplets is preferably 1500 ° C. or lower. This is because energy is wasted.

  In step (C), the reducing atmosphere for heating the atomized droplets is an inert atmosphere of nitrogen gas, argon gas, carbon dioxide gas (carbon dioxide gas) in which the ultrafine carbon fiber does not react with oxygen, or monoxide Examples of the reducing gas such as carbon gas, hydrogen gas, ammonia gas, alcohol, hydrocarbon gas, or a mixed gas of the reducing gas and an inert atmosphere of nitrogen gas, argon gas, carbon dioxide gas, From the viewpoints of handling and safety, a mixed gas of nitrogen gas or carbon dioxide gas is preferable.

  The average particle size of the spherical composite copper particles produced depends on factors such as the composition of the dispersion solvent, the concentration of the copper compound in the dispersion solvent, the diameter of the atomized droplets, the heating temperature, and the atmospheric gas, and these factors are selected. By doing so, the particle diameter of the spherical composite copper fine particles can be controlled. When the concentration of the copper compound is low, the average particle diameter of the generated copper particles becomes small. In addition, when the boiling point of the dispersion solvent is low, if the heating is performed rapidly, the droplets are more likely to boil, and the droplets are split and made into fine particles.

  After the step (C), the obtained spherical composite copper fine particles are diluted and cooled to separate and collect the composite copper particles from the exhaust gas.

  The obtained spherical composite copper fine particles are immediately separated from the dew point of the dispersion solvent vapor immediately outside the heating furnace, in the case of an aqueous solution, diluted and cooled to 100 ° C. or higher, and then the copper particles combined with ultrafine carbon fibers are separated from the exhaust gas, For example, it collects with a filter, a cyclone, an electric dust collector, a vibrating bag filter, or the like. Even in any separator, in the case of metallic copper particles, the metal copper particles easily adhere to and condense on the separator, so that the recovery rate and dispersibility are unavoidable. On the other hand, the spherical composite copper fine particles combined with ultrafine carbon fibers achieve efficient collection and improve dispersibility.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.

[Example 1]
<Process (A)>
Nodal carbon nanofiber (Ube Industries, Ltd., trade name: AMC, fiber length: 160-1800 nm, outer diameter: 6-15 nm, inner diameter: 3-8 nm, aspect ratio: 40- 130), carboxymethylcellulose ammonium (CMC) salt (Daicel Finechem Co., Ltd. (trade name: NH4-CMCDN-10L), which is a dispersant, and ion-exchanged water in this order in a mass ratio of 3: 0.6: 96.7. Then, it was charged into a bead mill dispersing device (Ring Mill manufactured by Araki Iron Works Co., Ltd., vessel capacity: 2 dm ³ , zirconia bead diameter: 1 mm), and opened and dispersed for 120 minutes to prepare a dispersion solution in which ultrafine carbon fibers were dispersed. .

<(B) Process>
Next, copper nitrate (Cu (NO ₃ ) ₂ , first grade reagent manufactured by Kanto Chemical Co., Ltd.) is added to the prepared dispersion solution, and the mass ratio of ultrafine carbon fiber to metallic copper is 7.5: 92.5. was dissolved in a proportion, by diluting the copper nitrate concentration 2 mol / dm ^3, the mixture was prepared in a reaction vessel.

<Process (C)>
The prepared mixture was fed to a two-fluid atomizer atomizer using a metering pump (manufactured by Tokyo Rika Co., Ltd.) at a rate of 5 cm ³ / min, a nitrogen gas flow rate: 25 dm ³ / min and a hydrogen gas flow rate: 5 dm. Droplets were formed at ³ / min, and a carrier nitrogen gas was flowed at 40 dm ³ / min and charged into a mullite tube heated to 1150 ° C. The liquid droplets were volatilized and pyrolyzed in the heating area, and the product was separated and collected by a cyclone.

The particles collected by the cyclone had no agglomerates, showed good dispersibility, and the recovery rate was 95% by mass. Further, the collected particles were spherical composite copper fine particles having a particle diameter of 100 to 8000 μm. Table 1 shows these results. In Table 1, the particle shape, the minimum particle size, and the maximum particle size were observed with a scanning electron micrograph. The minimum particle diameter and the maximum particle diameter were determined from the long diameter (the longest diameter of the spherical composite copper fine particles) among the 50 spherical composite copper fine particles observed. A true sphere is an aspect ratio of 1.05 or less, and an irregular shape is a case where the aspect ratio is greater than 1.4. The recovery rate was calculated from [(mass of collected spherical composite copper fine particles) / (mass of theoretically obtained spherical composite copper fine particles) × 100]. The particle properties are “◎” when the aspect ratio is 1.0 or more and 1.1 or less, “◯” when the aspect ratio is more than 1.1 and 1.2 or less, and the aspect ratio is 1.2. “Δ” when exceeding 1.4 and not exceeding 1.4, and “x” when the aspect ratio exceeds 1.4 and when spherical composite copper fine particles adhered to the cyclone surface. As a result of quantitative analysis of the spherical composite copper fine particles produced in Example 1 by energy dispersive X-ray analysis (EDX), carbon was 8.0 parts by mass with respect to 100 parts by mass of the spherical composite copper fine particles. It was.

  1 and 2 show scanning electron microscope (SEM) photographs of the spherical composite copper fine particles produced in Example 1. FIG. 1 and 2, it was found that the composite copper fine particles produced in Example 1 were spherical. Further, it was found that the composite copper fine particles produced in Example 1 had finer composite copper fine particles having a particle diameter of 1 nm or more adhered to the surface. Next, FIG. 3, FIG. 4 and FIG. 5 show SEM photographs after etching the spherical composite copper fine particles produced in Example 1 with a 35 mass% nitric acid aqueous solution for 120 seconds. From FIG. 3, FIG. 4, and FIG. 5, it was confirmed that ultrafine carbon fibers were present on the surface of the spherical composite copper fine particles after etching. From this, it was confirmed that the spherical composite copper fine particles produced in Example 1 contained ultrafine carbon fibers inside. Next, FIG. 6 and FIG. 7 show SEM photographs after etching the spherical composite copper fine particles produced in Example 1 with a 35 mass% nitric acid aqueous solution for 420 seconds. 6 and FIG. 7 also confirm that ultrafine carbon fibers are present on the surface of the spherical composite copper fine particles after etching. From the comparison between FIGS. 3 to 5 and FIGS. It was found that ultrafine carbon fibers existed. For reference, FIG. 8 shows an SEM photograph of the used ultrafine carbon fiber.

[Examples 2-3]
In the step ( B ), spherical composite copper fine particles were produced in the same manner as in Example 1 except that the mass ratio of ultrafine carbon fiber: metal copper was 1:99, 4:96. Table 1 shows the preparation conditions of Examples 2-3, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

Example 4
In step (A), the dispersant is β-naphthalenesulfonic acid formalin condensate (naphthalene) (DEMOL-N manufactured by Kao Corporation), and the mass ratio of ultrafine carbon fiber: dispersant: ion exchanged water is 5: 2. : Spherical composite copper fine particles were produced in the same manner as in Example 1 except that the ratio was 93. Table 1 shows the preparation conditions of Example 4, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

Example 5
In step (C), spherical composite copper fine particles were produced in the same manner as in Example 4 except that hydrogen gas: 5 dm ³ / min was added to nitrogen gas to form droplets and the heating temperature was changed to 1090 ° C. Table 1 shows the preparation conditions of Example 5, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

[Examples 6 and 7]
<Process (A)>
Nodal carbon nanofiber (Ube Industries, Ltd., trade name: AMC, fiber length: 160-1800 nm, outer diameter: 6-15 nm, inner diameter: 3-8 nm, aspect ratio: 40- 130), β-naphthalenesulfonic acid formalin condensate (naphthalene) (DEMOL-N manufactured by Kao Corporation), which is a dispersant, and ion-exchanged water in this order at a mass ratio of 5: 2.5: 92.5, A bead mill dispersing apparatus (Ring Mill manufactured by Araki Iron Works Co., Ltd., vessel capacity: 2 dm ³ , zirconia bead diameter: 1 mm) was charged, opened and dispersed for 300 minutes to prepare a dispersion solution in which ultrafine carbon fibers were dispersed. Steps (B) and (C) were produced in the same manner as in Example 1 except that the formulation shown in Table 1 was used, to produce spherical composite copper fine particles. Table 1 shows the preparation conditions of Examples 6 to 7, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

Example 8
Spherical composite copper fine particles were produced in the same manner as in Example 1 except that the step (C) was made into droplets at a flow rate of carbon dioxide gas: 25 dm ³ / min and hydrogen gas: 5 dm ³ / min. Table 1 shows the preparation conditions of Example 8, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

Example 9
Spherical composite copper fine particles were produced in the same manner as in Example 1 except that the step (C) was made into droplets at an ammonia gas flow rate of 30 dm ³ / min. Table 1 shows the preparation conditions of Example 9, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

[Comparative Example 1]
Copper particles were produced in the same manner as in Example 1 except that the ultrafine carbon fiber of Example 1 was not added. Table 1 shows the results of Comparative Example 1.

[Comparative Example 2]
<Process (A)>
Nodal carbon nanofiber (Ube Industries, Ltd., trade name: AMC, fiber length: 160-1800 nm, outer diameter: 6-15 nm, inner diameter: 3-8 nm, aspect ratio: 40- 130), β-naphthalenesulfonic acid formalin condensate (naphthalene) (DEMOL-N manufactured by Kao Corporation), which is a dispersant, and ion-exchanged water in this order at a mass ratio of 5: 2.5: 92.5, A bead mill dispersing device (Araki Tekko Co., Ltd. ring mill, vessel capacity: 2 dm ³ , zirconia bead diameter: 1 mm) was charged, opened and dispersed for 300 minutes to prepare a dispersion solution in which ultrafine carbon fibers were dispersed. In the steps (B) and (C), spherical composite copper fine particles were produced in the same manner as in Example 1 except that the mass ratio of ultrafine carbon fiber: metal copper was 16.0: 84.0 . Table 1 shows the preparation conditions of Comparative Example 2, the physical properties of the produced spherical composite copper fine particles, and the recovery rate.

[Comparative Example 3]
Composite copper fine particles were prepared in the same manner as in Example 4 except that the mass ratio of ultrafine carbon fiber: metal copper was 21:79. Table 1 shows the results of Comparative Example 3.

  As can be seen from Table 1, in all of Examples 1 to 8, spherical composite copper fine particles having true spheres and 0.1 to 15.0 parts by mass of ultrafine carbon fibers were obtained. On the other hand, in the comparative example 1 of the spherical copper particles not containing ultrafine carbon fibers, the copper fine particles were fixed to the cyclone mirror surface in the recovery after the step (C), and the recovery rate was low. In addition, since the comparative example 1 does not contain an ultrafine carbon fiber, it is thought that it does not have the said composite effect. On the other hand, in Comparative Examples 2 and 3 in which the content of ultrafine carbon fibers is too large, spherical particles were not obtained.

Claims (8)

Containing ultrafine carbon fibers therein, with respect to 100 parts by weight of the spherical composite copper particles, ultrafine carbon fibers Ri 0.1-15.0 parts by der, and an aspect ratio of 1.0 to 1.2 A spherical composite copper fine particle characterized by the above.   The spherical composite copper fine particle according to claim 1, wherein the spherical composite copper fine particle has a particle diameter of 1 nm or more and less than 20000 nm.   The ultrafine carbon fiber is a hollow fiber, the fiber length: L is 50 nm or more, the outer diameter: D is 5-40 nm, the inner diameter: d is 2-30 nm, and the aspect ratio (L / D) is 5-1000. The spherical composite copper fine particles according to claim 1 or 2. (A) After adding the ultrafine carbon fiber aggregate and the dispersant to the dispersion solvent, obtaining a dispersion solution in which the ultrafine carbon fibers are dispersed;
(B) After mixing a copper compound with the obtained dispersion solution, dissolving the copper compound to obtain a mixture, and (C) atomizing the obtained mixture into fine droplets, Heating the transformed droplets at 1083 ° C. or higher in a reducing atmosphere;
In this order, containing ultrafine carbon fibers inside, spherical composite copper fine particles having 0.1 to 15.0 parts by mass of ultrafine carbon fiber with respect to 100 parts by mass of spherical composite copper fine particles Manufacturing method.   By using a catalyst containing at least one element selected from the group consisting of Fe, Co, Ni, Mo, Al, Mg, Zn, Ti, and Si as an ultrafine carbon fiber, by vapor phase growth method using a gas containing carbon The manufacturing method of the spherical composite copper fine particle of Claim 4 manufactured.   The method for producing spherical composite copper fine particles according to claim 4 or 5, wherein the dispersant is carboxymethyl cellulose, naphthalene sulfonate, or polyvinyl pyrrolidone.   The method for producing spherical composite copper fine particles according to any one of claims 4 to 6, wherein the dispersion solvent contains at least one selected from the group consisting of water and a polar organic solvent.   In the step (C), the reducing atmosphere for heating the atomized droplets is at least one selected from the group consisting of nitrogen gas, carbon dioxide gas, ammonia gas, alcohol, hydrocarbon gas and hydrogen gas. The manufacturing method of the spherical composite copper fine particle of any one of 4-7.