JP6771636B1 - Copper powder manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce coarse powder in a method for producing metal powder by a vapor phase method, in which chlorine gas supplied to a chlorination furnace does not react with a metal raw material but is supplied to a reduction furnace as unreacted chlorine gas. To provide a manufacturing method that can suppress this. SOLUTION: In a method for producing a metal powder, which produces a metal powder by reacting a metal raw material with a chlorine gas in a chlorination furnace to obtain a metal chloride and reacting the metal chloride with a reducing gas. The ratio (s / S) of the cross-sectional area (s) perpendicular to the direction of the metal raw material to the cross-sectional area (S) perpendicular to the traveling direction of the chlorine gas in the chloride furnace is 0.5 or more and 0.95 or less. is there. [Selection diagram] Fig. 1

Description

One embodiment of the present invention relates to a method for producing a metal powder.

Conductive paste containing metal powder or metal powder, which is an aggregate of fine metal particles, can be used for wiring and terminals of low-temperature co-fired ceramics (LTCC) substrates, internal electrodes and external electrodes of multilayer ceramic capacitors (MLCC), etc. It is widely used as a raw material for manufacturing various electronic parts. In particular, copper powder has been widely used in the past because of the high conductivity of copper, which enables thinning of the internal electrode of MLCC, miniaturization of the external electrode, and significant improvement of frequency characteristics. It is expected as a material to replace nickel powder and silver powder.

As a method for producing a metal powder, a wet method, a vapor phase growth method, or the like is known. Compared to the wet method, the vapor phase growth method has a simpler manufacturing process, so it is suitable for mass production, and by appropriately controlling the manufacturing conditions, it is possible to manufacture metal powders with excellent characteristics. It is possible. The vapor phase growth method is based on reducing a metal chloride gas with a reducing gas to obtain a metal powder. As a method of obtaining the metal chloride gas, there is also a method of heating the metal chloride, but in this method, it is difficult to control the amount of the metal chloride gas produced, so that the supply amount becomes unstable and the particle size becomes large. There is a drawback that the particle size distribution becomes broad as the control becomes difficult. On the other hand, there is a method in which a metal is used as a raw material and the metal is reacted with chlorine gas to generate a metal chloride gas. This method has the advantages that a metal raw material that is cheaper than metal chloride can be used and that the supply amount of metal chloride gas can be stabilized.

However, the metal and chlorine gas may not react properly. For example, the metal raw material is not uniformly chloride as the reaction progresses, and only the central part or the peripheral part of the metal raw material installed in the chlorination furnace is selected. The metal raw material may be partially reduced due to chlorination. When such a thing occurs, a part of chlorine supplied to the chlorination furnace is supplied to the reduction furnace without reacting with the metal raw material, and the reaction temperature of the reduction furnace rises or the metal supplied to the reduction furnace. There is a problem that coarse powder is generated due to the decrease in the partial pressure of the chloride gas.

Prior literature on the formation of metal chlorides in the vapor deposition method includes the following.
Patent Document 1 discloses a technique for accommodating a plurality of spherical metals in a row in a reaction tube. By accommodating the metal raw materials in a row, the metal does not accumulate on the inner wall side of the reaction tube, the phenomenon called shelf suspension in which the metals fuse with each other does not occur, and the metal thermally expands due to heating. However, since the pressure acting on the reaction tube is zero or extremely small, the reaction tube is cracked or damaged due to the periodic pressure of the reaction tube expanding from the metal, and the service life is short. The problem will be solved. However, if the metals are stored in a single row, the productivity is inferior because the amount of metal to be reacted is small, and if a large number of reaction tubes are arranged, the apparatus becomes complicated and the cost increases.

According to Patent Document 2, when a metal raw material is reacted with chlorine gas to continuously generate metal chloride vapor in a chlorination furnace, the weight of the chlorination furnace is weighed, and the metal raw material is based on the weighing result. The technology for controlling the supply of chlorinated furnaces is disclosed. However, this content only shows the technology related to weighing the chlorination furnace so that various measures can be taken if a problem occurs in the result, and no problem occurs in the first place. The technique for doing so is not disclosed.

Japanese Unexamined Patent Publication No. 2000-351621 Japanese Unexamined Patent Publication No. 2004-027422

As described above, in the method for producing metal powder by the vapor phase growth method, although the technique for producing metal chloride satisfactorily is important, it has hardly been studied so far.

In view of such a background, in one embodiment of the present invention, the metal raw material and chlorine gas do not react appropriately, or a part of the metal raw material selectively reacts and partially decreases as the reaction progresses. Then, it is necessary to provide a manufacturing method capable of suppressing the chlorine gas supplied to the chlorination furnace from being supplied to the reduction furnace as unreacted chlorine gas without reacting with the metal raw material and producing coarse powder. The purpose.

In the method for producing a metal powder according to an embodiment of the present invention, a metal raw material and a chlorine gas are reacted in a chloride furnace to obtain a metal chloride, and the metal chloride is reacted with a reducing gas to obtain a metal powder. It is a method of generating a body, and the ratio of the cross-sectional area (s) of the metal raw material in the cross section perpendicular to the traveling direction of chlorine gas to the cross-sectional area (S) of the chloride furnace in the cross section perpendicular to the traveling direction of chlorine gas (s). s / S) is set to be 0.5 or more and 0.95 or less.

In the method for producing a metal powder according to an embodiment of the present invention, one embodiment is that the sphericity (minor axis / major axis) defined by the ratio of the major axis to the minor axis of the metal raw material is 0.8 or more. Illustrated.

In the method for producing a metal powder according to an embodiment of the present invention, the ratio of the average diameter (d) of the metal raw material to the diameter (D) of the cross section of the chlorination furnace in the cross section perpendicular to the traveling direction of chlorine gas ( An example is that d / D) is 0.03 or more and 0.2 or less.

In the method for producing a metal powder according to an embodiment of the present invention, an example is that the average diameter (d) of the metal raw material is 6 mm or more and 30 mm or less.

In the method for producing a metal powder according to an embodiment of the present invention, the cross-sectional area of the metal raw material at any two cross sections perpendicular to the traveling direction of the chlorine gas (s1 and s2, where s2 ≧ s1). The ratio (s1 / s2) of is 0.6 or more, as an example.

According to the production method according to the embodiment of the present invention, the reaction between the metal raw material and chlorine gas in the chlorination furnace can be appropriately performed, and the appropriateness of the reaction can be maintained even if the reaction proceeds. Therefore, it is possible to suppress the supply of unreacted chlorine gas to the reduction furnace, and it is possible to suppress the production of coarse powder.

It is a figure which shows the schematic structure of the metal powder production apparatus which concerns on one Embodiment of this invention. It is a figure which shows typically the relationship between the cross-sectional area S of the chloride furnace of the metal powder production apparatus which concerns on one Embodiment of this invention, and the cross-sectional area s of a metal raw material.

Hereinafter, the contents of the embodiment of the present invention will be described with reference to the drawings and the like. However, the present invention includes many different aspects and is not construed as being limited to the contents of the embodiments exemplified below. In order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment, but this is merely an example and limits the content of the present invention. It's not something to do. Further, in the present specification, when a certain element described in a certain drawing and a certain element described in another drawing have the same or corresponding relationship, the same reference numerals are given and the description is repeated. It may be omitted as appropriate. Further, the characters added with "first" and "second" for each element are convenient markers used to distinguish each element, and have no further meaning unless otherwise specified.

1. 1. Method for Producing Copper Powder Copper powder is produced by using metallic copper as a metal raw material, reacting the metallic copper with chlorine gas, and reacting the produced copper chloride gas with a reducing gas. The copper powder thus produced is appropriately subjected to a treatment for reducing chlorine components and oxygen components, and a surface treatment. Hereinafter, each stage of the manufacturing method will be described.

1-1. Generation of Copper Chloride Gas Copper chloride gas is generated by using metallic copper as a metal raw material and reacting the metallic copper with chlorine gas. This method is not only cost-effective in that metallic copper, which is cheaper than copper chloride, can be used, but also can stabilize the supply amount of copper chloride gas. As a specific method for producing copper chloride gas, copper chloride gas can be produced by reacting metallic copper with chlorine gas at a melting point or lower (for example, 800 ° C. or higher and 1000 ° C. or lower). The chlorine gas may be a gas containing substantially only chlorine, or may be a mixed gas of chlorine containing an inert gas for dilution and an inert gas for dilution. By using a mixed gas, it is possible to easily and precisely control the amount of chlorine that reacts with metallic copper. The specific shape and installation method of metallic copper will be described in detail later.

1-2. Reduction of Copper Chloride The produced copper chloride gas is reacted with the reducing gas to produce copper powder. As the reducing gas, for example, hydrogen, hydrazine, ammonia, methane and the like can be used. The reducing gas can be used in a stoichiometric amount or more with respect to the copper chloride gas. For example, when the copper chloride gas is entirely composed of monovalent copper chloride and the reducing gas is hydrogen, the amount of the reducing gas introduced is 50 mol% or more and 10000 mol% or less, 500 mol% with respect to the copper chloride gas. It can be 10000 mol% or more, or 1000 mol% or more and 10000 mol% or less. By this reaction, copper chloride is reduced to copper, and the copper element grows into copper particles to become copper powder as an aggregate.

1-3. Reduction of chlorine component In order to reduce the chlorine component contained in the copper powder, the copper powder obtained by the above production method is treated with an aqueous solution or suspension of a base to remove the chlorine component. May be done.

1-4. Reduction of oxygen component The copper powder obtained by the above production method was treated with a solution or suspension containing ascorbic acid, hydrazine, citric acid, etc. as a cleaning solution in order to reduce the oxygen component. After that, it may be washed with water, filtered, and dried.

1-5. Surface treatment A predetermined surface treatment may be applied to the copper powder obtained by the above production method. Examples of the surface treatment material include nitrogen-containing heteroaromatic compounds such as benzotriazole and its derivatives, triazole and its derivatives, thiazole and its derivatives, benzothiazole and its derivatives, imidazole and its derivatives, and benzimidazole and its derivatives. Materials can be used.

1-6. Other Treatments The copper powder obtained by the above production method may be subjected to treatments such as drying, classification, crushing, and sieving. The classification may be dry classification or wet classification, and in the dry classification, any method such as air flow classification, gravitational field classification, inertial force field classification, and centrifugal force field classification can be adopted. Similarly, in wet classification, methods such as gravitational field classification and centrifugal force field classification can be adopted. Crushing can be performed using, for example, a jet mill. Sieve separation can be performed by vibrating a sieve having a desired mesh size and passing copper powder through the sieve. It is possible to reduce the particle size distribution of copper powder by performing classification, crushing, and sieving.

2. Characteristics of copper powder 2-1. Copper powder produced by a process having an average particle size or larger has a small average particle size and a narrow distribution due to the production of primary powder by the vapor phase growth method. Here, the average particle size of the copper powder means the particle size when the cumulative frequency in the volume-based particle size histogram of the copper powder becomes 50%. The volume-based particle size of the copper powder is a particle size weighted by the volume of each particle contained in the copper powder. As expressed by the following formula, the particles are obtained by dividing the total volume of particles having a particle diameter di (i is a natural number from 1 to k, i ≦ k) by the total volume of all particles contained in the powder. The frequency F of the particles having a diameter di is obtained. The particle diameter when the frequency F is accumulated and reaches 50% is the median diameter D ₅₀ . Here, the average particle size is also expressed as D ₅₀ .

ここでＶｉは、粒子径ｄｉを有する銅粒子の体積であり、ｎｉは粒子径ｄｉを有する銅粒子の個数である。

Here, Vi is the volume of copper particles having a particle diameter di, and ni is the number of copper particles having a particle diameter di.

The method of calculating the volume Vi and the particle diameter di will be described below. In a micrograph of copper powder observed with an optical microscope or an electron microscope, copper particles having confirmed contours (for example, 100 to 10,000, typically 500) are visually observed. Next, the particle diameter of the copper particles is calculated from the surface area Si of the copper particles visually observed as the diameter of an assumed circle having the same area as the surface area. Specifically, the particle size di is calculated by the following formula.
Si = π (di) ²

Next, the volume Vi of the copper particles is calculated from the calculated particle diameter di by the following formula.
^{Vi = 4π (di / 2)} 3/3

The copper powder produced by the method for producing a copper powder according to an embodiment of the present invention has an average particle diameter D ₅₀ of 100 nm or more and 500 nm or less, specifically 100 nm or more and 300 nm or less, and the proportion of coarse powder. Very few are obtained. By sintering this copper powder that satisfies this range, a metal film with a small thickness can be provided. Therefore, for example, thinning of MLCC electrodes, miniaturization of wiring and terminals of electronic components such as LTCC substrates, etc. Can contribute to. The copper powder having an average particle size D ₅₀ as described above can be obtained by the arrangement of the chlorine gas and the metal raw material in the copper powder production apparatus shown in Section 3 and the chloride furnace described in Section 4.

2-2. In one embodiment of the coarse powder present invention, it defines the copper particles having a particle size of more than 2 times the average particle diameter D ₅₀ and coarse powder. For example, when the average particle diameter D ₅₀ of the copper powder is 300 nm, the copper particles having a particle diameter of 600 nm or more are classified as coarse powder.

3. 3. Copper powder manufacturing apparatus FIG. 1 shows an outline of the copper powder manufacturing apparatus 100. The manufacturing apparatus 100 includes a metal chloride generating apparatus 110 and a reducing apparatus 150 as a main configuration. The metal chloride generator 110 and the reduction apparatus 150 have a chloride furnace 112 and a reduction furnace 152, respectively. Although not shown, the manufacturing apparatus 100 may further include a separation device connected to the reduction furnace 152 and a recovery device such as a reduction furnace 152 or a bag filter connected to the separation device. The chlorination furnace 112 and the reduction furnace 152 are connected by a first transport pipe 120, and the reduction furnace 152 and the separator or bag filter are connected by a second transport pipe 156.

One of the functions of the chlorination furnace 112 is to produce a metal chloride by the reaction of a metal (zero-valent metal) and chlorine (Cl ₂ ) gas. As the metal raw material, metallic copper is used, but silver, nickel and the like can also be used. The shape of the metal raw material is not limited, and for example, granular, pellet-shaped, wire-shaped, and plate-shaped metals can be used. In the present embodiment, as the metal raw material, preferably a spherical one is used.

The metal chloride generator 110 has a heater 114 for heating the chloride furnace 112, and the metal raw material reacts with chlorine gas in the heated chloride furnace 112 to generate metal chloride. The chlorination furnace 112 has a gas introduction pipe 122 for introducing chlorine gas at one end, and a first transport ship 120 for transporting metal chloride to the reduction furnace 152 at the other end. The chlorine gas supplied from the gas introduction pipe 126 fills the chlorination furnace 112 and flows in the direction of the first transport pipe 120 by a natural flow. The chlorination furnace 112 is further provided with an opening 116 for charging a metal raw material.

The generated metal chloride exists as a gas or liquid in the chlorination furnace 112, and the metal chloride gas is introduced into the reduction furnace 152 through the first transport pipe 120. The reduction furnace 152 includes a gas introduction pipe 158 for introducing hydrogen, hydrazine, ammonia, methane, and the like, which are reducing gases for reducing metal chloride. The reduction device 150 has a heater 154 for heating the reduction furnace 152, and the metal chloride is reduced in the heated reduction furnace 152, whereby a metal powder is produced. An inert gas such as nitrogen gas is introduced into the reduction furnace 152 from the outside through a gas introduction pipe (not shown), the metal powder produced thereby is cooled, and a separation device or a recovery device is introduced through the second transport pipe 156. Will be transported to.

In FIG. 1, the metal chloride generator 110 is drawn so as to be located above the reduction apparatus 150, but there is no limitation on the positional relationship between them. For example, the metal chloride generator 110 and the reduction apparatus 150 are horizontally arranged. It may be placed in.

Although detailed description is omitted, the separation device has a function of purifying the metal powder by removing the agglomerates contained in the metal powder and the sintered metal produced as a by-product in the reduction furnace 152. A recovery device is provided to isolate the purified metal powder from nitrogen gas.

4. Chlorine gas and metal raw materials in the chlorination furnace The details of chlorine gas in the chlorination furnace will be described below.

4-1. Chlorine gas In one embodiment of the present invention, the traveling direction of chlorine gas is the direction in which chlorine gas travels in the chlorination furnace as a whole, regardless of the local direction of chlorine gas in the chlorination furnace. Means. Therefore, depending on the arrangement of the metal raw materials, chlorine gas may travel in various directions microscopically, but as a whole, it travels in the direction corresponding to the structure of the chlorination furnace, which is the direction of chlorine gas travel. Means such a direction.

For example, as shown in FIG. 1, the chloride furnace 112 is a vertical type, chlorine gas is introduced from a gas introduction pipe 122 above the chloride furnace 112, and metal chloride produced as a result of a reaction between a metal raw material and chlorine gas. In the case of a structure in which the physical gas is discharged from the first transport pipe 120 provided in the lower part of the chlorination furnace 112, the traveling direction F of the chlorine gas is vertically downward as shown by an arrow in FIG.

The cross-sectional area of the chloride furnace in the cross section perpendicular to the traveling direction F of chlorine gas is the area of the virtual cut surface when the chloride furnace is cut in the cross section perpendicular to the traveling direction of chlorine gas defined above. To say. For example, in the chloride furnace 112 shown in FIG. 1, the virtual cross-sectional area obtained from the cross section cut along the dotted line is referred to as the cross-sectional area of the chloride furnace. If the chlorination furnace has a cylindrical shape, the cut cross section will be circular.

4-2. Metal raw material The cross-sectional area of the metal raw material in the cross section perpendicular to the traveling direction of chlorine gas is the cross section perpendicular to the traveling direction of chlorine gas and is the region filled with the metal raw material of the chloride furnace (hereinafter referred to as the above). , Refers to the area of the virtual cut surface when cutting an arbitrary place of the packed layer). Since the packed bed is mostly composed of a small metal raw material with respect to the chlorination furnace, the gap portion of the individual particles (or pellets, etc.) of the metal raw material is not included in the area.

For example, as shown in FIG. 2, when the chlorination furnace 112 is tubular and the traveling direction F of the chlorination furnace 112 is parallel to the longitudinal direction of the chlorine gas, the cross-sectional area S perpendicular to the traveling direction F is the chlorination furnace. It is equal to the cross-sectional area of the inner diameter of 112. The chlorination furnace 112 has a packing layer 104 filled with a plurality of metal raw materials 102. The packed bed 104 is the total cross-sectional area s (s) of the cross sections s11, s12, s13, ..., S1n of the individual metal raw materials 102 in the vertical cross section in the traveling direction F of the chlorine gas at a position of the chlorination furnace 112. = S11 + s12 + s13 + ... + s1n).

The ratio of the cross-sectional area S of the chlorination furnace to the cross-sectional area s of the metal raw material, s / S, is an index corresponding to the filling rate in the cross section of the packed bed. Here, if the s / S is less than 0.5, the gap between the metal raw materials is too large, so that the reaction proceeds unevenly as the reaction progresses, and only a part of the metal raw materials is excessively consumed. It is likely that unreacted chlorine will be generated. On the other hand, when the s / S exceeds 0.95, the gap between the metal raw materials is too small, so that the reaction between the metal raw material and the chlorine gas becomes insufficient, and the reaction proceeds unevenly as the reaction progresses. As a result, only a part of the metal raw material is excessively consumed and reduced, and unreacted chlorine is likely to be generated.

Granular metal raw materials are used, and the sphericality (minor axis / major axis) defined by the ratio of the major axis to the minor axis is preferably 0.8 or more. Since the sphericity is a value defined by the minor axis / major axis, the maximum value is 1, which is a perfect sphere, which is the upper limit of the sphericity. The shape of the metal raw material is basically arbitrary, but if it is completely disjointed or has a cubic shape, it is not easy to form a packed layer so as to satisfy the above filling rate requirements. Therefore, in one embodiment of the present invention, it is desirable that the metal raw material is close to a sphere.

In one embodiment of the present invention, the diameter of the metal raw material is defined as the average value of the major axis and the minor axis when the sphericity of the metal raw material is 0.8 or more. The average diameter of the metal raw material is defined as the average diameter of the metal raw material used as the raw material. The ratio (d / D) of the average diameter (d / D) of the cross section perpendicular to the vertical cross section and the cross section parallel to the vertical cross section of the metal raw material is 0.03 or more and 0 to the diameter (D) of the cross section perpendicular to the traveling direction of chlorine gas in the chloride furnace. It is preferably 2 or less. If this ratio (d / D) is less than 0.03, the average diameter of the metal raw material becomes very small compared to the cross-sectional area of the chlorination furnace, and many small metal raw materials are installed. In such a case, it becomes difficult to satisfy the above-mentioned filling rate requirement. On the other hand, when the ratio (d / D) exceeds 0.2, the average diameter of the metal raw material becomes relatively large compared to the cross-sectional area of the chlorination furnace, and a small number of large metal raw materials are installed. In such a case, it becomes difficult to satisfy the requirement of claim 1.

In one embodiment of the present invention, the sphericity of the metal raw material is preferably 0.8 or more, the average diameter (d) of the metal raw material is preferably 6 mm or more and 30 mm or less, and more preferably 11 mm or more and 27 mm or less. .. If the cross-sectional area of the chlorination furnace is too small, the productivity will be poor, and conversely, if it is too large, a uniform reaction will be difficult. Therefore, since the cross-sectional area of the chlorination furnace is preferably 150 cm ² or more and 250 cm ² or less, the average diameter (d) of the metal raw material is preferably 6 mm or more and 30 mm or less. If it is out of this range, it becomes difficult to satisfy the filling rate requirement as described above.

In one embodiment of the present invention, the ratio (s1 / s2) of the cross-sectional areas (s1 and s2, where s2 ≧ s1) of the metal raw material is in any two cross sections perpendicular to the traveling direction of chlorine gas. , 0.6 or more is preferable. Even if the cross-sectional area of the metal raw material in the cross section perpendicular to the traveling direction of chlorine gas is within the range of the filling rate, if the values are significantly different, unreacted chlorine is likely to be generated.

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to the Examples.

[Example 1]
Metallic copper as a metal raw material was installed in the chlorination furnace, and the temperature of the chlorination furnace was set to 900 ° C. The volume ratio of chlorine gas introduced from the chlorine introduction pipe at the top of the chlorination furnace to the volume ratio of chlorine gas introduced from the chlorine introduction pipe at the bottom of the chlorination furnace is 1: 0.17, from the chlorine introduction pipe at the top of the chlorination furnace. Chlorine furnace so that the volume ratio of chlorine gas to be introduced is 29:61 and the volume ratio of chlorine gas to nitrogen gas introduced from the chlorine introduction pipe at the bottom of the chlorine gas is 2:98. Chlorine gas and nitrogen gas were introduced into the mixture to react metallic copper with chlorine gas to generate copper chloride gas. At this time, the cross-sectional area S of the chloride furnace, the cross-sectional area s of the metal raw material, the ratio of the cross-sectional area of the chloride furnace to the cross-sectional area of the metal raw material (s / S), the diameter D of the cross section of the chloride furnace, and the average diameter d of the metal raw material , The ratio (d / D) of the cross section diameter D of the chloride furnace to the average diameter d of the metal raw material in the cross section perpendicular to the traveling direction of the chlorine gas, the sphericality of the metal raw material, and any arbitrary perpendicular to the traveling direction of the chlorine gas. Table 1 shows the ratio (s1 / s2) of the cross-sectional area of the metal raw material to the two cross sections of.

The generated copper chloride gas is guided to a reduction furnace heated to 1150 ° C., and the hydrogen gas and the hydrogen gas and the nitrogen gas are 24600 mol% with respect to the copper chloride gas so that the hydrogen gas is 4600 mol% with respect to the copper chloride gas. Nitrogen gas is introduced into a reduction furnace to reduce copper chloride to produce copper, and the produced copper is cooled with nitrogen gas to obtain individual copper particles, and copper powder is produced as an aggregate of copper particles. Obtained.

Using a scanning electron microscope (SEM: Hitachi High-Technologies Co., Ltd., SU5000), the obtained copper powder is image-analyzed software for 500 copper particles existing in one field of view of an SEM image at a magnification of 15,000. As a result of analysis using (Macview 4.0 manufactured by Mountech Co., Ltd.), the average particle size D ₅₀ was 246 nm.

Define the copper particles having a particle size of more than 2 times the average particle diameter D ₅₀ and coarse powder, 500 copper particles present in one of the field of view of the SEM image in Zendokotai (magnification 15000 times described above ), The abundance ratio (%) of the crude powder was evaluated, and the abundance ratio of the crude powder was 0.6%.

The abundance ratio of coarse powder is ⊚ for 1.0% or less, 〇 for more than 1.0% and 2.5% or less, Δ for more than 2.5% and 3.0% or less, and × for more than 3.0%. The evaluation results based on this standard are also shown in Table 1. In Example 1, since the abundance ratio of the crude powder was 0.6%, very good results were obtained.
The above results are shown in Table 1.

[Example 2]
Copper powder was produced under the same conditions as in Example 1 except that the ratio of the cross-sectional area S of the chlorination furnace to the cross-sectional area s of the metal raw material and the s / S were 0.75.

The obtained copper powder, as a result of evaluating in the same manner as in Example 1, the average particle diameter D ₅₀ is 249 nm, the abundance ratio is 0.8% very good results of the coarse powder was obtained.
The above results are shown in Table 1.

[Example 3]
Copper powder was produced under the same conditions as in Example 1 except that the ratio of the cross-sectional area S of the chlorination furnace to the cross-sectional area s of the metal raw material and the s / S were set to 0.90.

As a result of evaluating the obtained copper powder by the same method as in Example 1, the average particle size D ₅₀ was 251 nm and the abundance ratio of the coarse powder was 0.7%, and very good results were obtained.
The above results are shown in Table 1.

[Example 4]
The average diameter d of the metal raw material is 1.52 mm, and the ratio of the average diameter (d) of the cross section perpendicular to the vertical cross section and the parallel cross section of the metal raw material to the diameter (D) of the cross section perpendicular to the traveling direction of the chlorine gas of the chloride furnace ( A copper powder was produced under the same conditions as in Example 2 except that d / D) was set to 0.01.

As a result of evaluating the obtained copper powder by the same method as in Example 1, the average particle size D ₅₀ was 245 nm and the abundance ratio of the coarse powder was 1.5%, and good results were obtained.
The above results are shown in Table 1.

[Example 5]
Copper powder was produced under the same conditions as in Example 2 except that a cubic metal material was used instead of the spherical metal material.

The obtained copper powder, as a result of evaluating in the same manner as in Example 1, the average particle diameter D ₅₀ is 263 nm, the abundance ratio is 2.7% acceptable results of the coarse powder was obtained.
The above results are shown in Table 1.

[Example 6]
Except that the ratio (s1 / s2) of the cross-sectional area (s1 and s2, where s2 ≧ s1) of the metal raw material in any two cross sections perpendicular to the traveling direction of chlorine gas was set to 0.50. A copper powder was prepared under the same conditions as in Example 2.

As a result of evaluating the obtained copper powder by the same method as in Example 1, the average particle size D ₅₀ was 252 nm and the abundance ratio of the coarse powder was 3.0%, and acceptable results were obtained.
The above results are shown in Table 1.

[Comparison example]
As a comparative example, when the ratio of the cross-sectional area S of the chlorination furnace to the cross-sectional area s of the metal raw material, s / S is 0.99 (Comparative Example 1), and 0.30 (Comparative Example 2). The copper powder produced in the above was evaluated.

As a result of evaluating the obtained copper powder by the same method as in Example 1, the average particle diameter D ₅₀ of Comparative Example 1 was 332 nm, the abundance ratio of the crude powder was 3.9%, and the average particles of Comparative Example 2 were obtained. The diameter D ₅₀ was 325 nm, and the abundance ratio of the coarse powder was 4.2%.
The above results are shown in Table 1.

According to the present invention, the reaction between the metal raw material and chlorine gas in the chlorination furnace can be appropriately performed, and the appropriateness of the reaction can be maintained even if the reaction proceeds, so that the unreacted chlorine gas is reduced. The supply to the furnace can be suppressed, and the production of coarse powder can be suppressed. The present invention is an industrially useful invention.

100 ... Manufacturing equipment, 102 ... Metal raw material, 104 ... Filling layer , 110 ... Metal chloride generator, 112 ... Chloride furnace, 114 ... Heater, 116 ... Opening, 120 ... 1st transport pipe, 122 ... 1st gas introduction pipe, 150 ... reduction device, 152 ... reduction furnace, 154 ... heater, 156 ... second transport pipe 158 ... Third gas introduction pipe

Claims (4)

Production of metal powder that produces copper powder by reacting spherical metallic copper, which is a metal raw material, with chlorine gas in a chloride furnace to obtain copper chloride gas, and then reacting the copper chloride gas with a reducing gas. In the method
The chloride furnace has a cylindrical shape
The ratio of the maximum total cross-sectional area (s) of the spherical metallic copper in the cross section perpendicular to the traveling direction of the chlorine gas to the cross-sectional area (S) of the chloride furnace in the cross section perpendicular to the traveling direction of the chlorine gas. s / S) is 0.60 or more and 0.90 or less in the entire area of the chlorination furnace filled with the metal raw material .
The ratio (d / D) of the average diameter (d) of the spherical metallic copper to the diameter (d / D) of the cross section of the chlorination furnace in the cross section perpendicular to the traveling direction of the chlorine gas is 0.03 or more and 0. .. A method for producing a copper powder, which is characterized by being 2 or less. The method for producing copper powder according to claim 1, wherein the sphericity (minor axis / major axis) defined by the ratio of the major axis to the minor axis of the metallic copper is 0.8 or more. The method for producing copper powder according to claim 1 or 2, wherein the average diameter (d) of the spherical metallic copper is 6 mm or more and 30 mm or less. The ratio (s1 / s2) of the cross-sectional area (s1 and s2, where s2 ≧ s1) of the spherical metallic copper in any two cross sections perpendicular to the traveling direction of the chlorine gas is 0.6 or more. The method for producing a copper powder according to any one of claims 1 to 3, wherein the copper powder is produced.

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