JP2539761B2 - Method for producing metal fiber using metal powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metal fibers by mechanically deforming a metal powder, and in particular, imparts conductivity to a conductive paint, a conductive paste, a conductive plastic or the like. The present invention relates to a method for producing a metal suitable for a metal catalyst or an electrode material that requires a wide contact area with the metal filler.

[0002]

2. Description of the Related Art Recently, with the rapid increase in the use of electronic devices in general households and production sites of enterprises, the problem of operation disturbance due to the electromagnetic interference emitted from each electronic device has been seriously raised. Regulations regarding the extent of electromagnetic radiation from equipment are being tightened on a daily basis. The degree of electromagnetic wave emission can also be reduced by changing the circuit design and adopting special devices that suppress the emission.

However, it is difficult to prevent the inflow of electromagnetic waves from the outside unless the case of the equipment itself blocks the electromagnetic waves. In order for the case of a device to block the entry and exit of electromagnetic waves, how conductive the case must be. As a method for this, a method of coating zinc or a conductive paint on the inner wall of the case and a method of molding the case itself with a conductive plastic are carried out.Currently, the latter two methods are used. It is mainstream. The conductive paint and the conductive plastic are paints or resins mixed with a conductive filler, and as the filler, metal powder, metal flakes, metal fibers, metal-coated glass fibers and the like have been used. However, since the conductivity varies depending on the connectivity between the fillers, the filler in the fiber form, which has the best connectivity, is gradually becoming universal. On the other hand, the metal used as the catalyst and the electrode is required to have a high specific surface area in order to increase the reaction rate, and the specific surface area can be maximized by making the catalyst fibrous. Accordingly, various processes have been developed that can produce fine fibrous metal.

In order to utilize metal fibers as a conductive filler, the diameter of the fibers should be as small as possible (generally 50 μm).
m or less). This is because the smaller the diameter is, the lower the proportion of the filler to be mixed with the resin or the paint can be. Therefore, the required metal fibers cannot be manufactured by the simple wire drawing method which is a general wire rod processing method, and the following special method has been adopted.

An important method for producing the metal fiber for the conductive filler is a bundle drawing method.
g), vibration cutting method, molten metal radiation method in rotating water (in-r
oating water melt spinni
ng) etc. are raised. The bundle drawing method is a method of repeating a process of drawing a metal wire rod bundle to a sufficiently small diameter, then further solidifying the drawn wire into a bundle and drawing the bundle. This method is mainly used for producing long fibers with a diameter of 10 μm inside and outside, using stainless steel as a raw material. The vibration cutting method is a method of obtaining a fibrous cut material by periodically applying vibration to a cutting tool when cutting a material with a lathe, and a fiber such as a copper alloy, an aluminum alloy, or an iron alloy having a thickness of 50 μm or less is produced. Can be manufactured. The molten metal radiation method in rotating water is a method in which a molten metal is jetted into rotating water through a thin nozzle, and continuous long fibers having a diameter of 70 μm or more and short fibers having a diameter of 30 to 50 μm can be produced.

[0006]

However, the bundle drawing method can reduce the diameter of the fiber to 10 μm or less, and the fiber length can be freely changed through the cutting process in the future. Although there are advantages, there is a drawback that a considerable amount of cost is required in the processes of bundling the wire rods, the repeated wire drawing process and the wire drawing process after the final wire drawing. In addition, the vibration cutting method has a limitation that it is difficult to manufacture metal fibers having a diameter of 50 μm or less due to process control, although the process is simple and applicable to all materials. For example, although the fiber having a diameter of 10 μm produced by the wire-drawing method has sufficient conductivity even if only 5% by weight is mixed with plastic, the fiber produced by the vibration cutting method has a minimum content of 35% by weight or more. The required conductivity cannot be obtained without mixing. In the rotating water, the molten metal radiation method is a less expensive process than the previous two methods, but its diameter is 30% due to the surface tension of the molten metal injected.
Limited by μm or more. As described above, the existing metal fiber manufacturing technology is unavoidable in terms of the fiber diameter limit and manufacturing cost.

Generally, the optimum conductive fillers required are 100 to 20000 μm in length and 10 to 20 μm in diameter (in the case of conductive plastics, catalysts and electrodes). Alternatively, the length is 10 to 20 μm and the diameter is 5 μm inside and outside (conductive paint). The focus of the present invention is that the diameter of the metal powder produced by the spraying method is about 30-300 μm, and the diameter of the metal powder produced by the chemical method is generally 1-.
On the other hand, when the wire is manufactured by metal extrusion, the extrusion ratio can be up to several hundred to one. This is carried out by stretching metal powder of a suitable size by a drawing process such as extrusion at a suitable ratio to obtain a suitable diameter of 5-50 μm and a length of 10-50 for conductive plastics, catalysts, electrodes, etc.
This means that metal fibers of about 000 μm can be produced.

Therefore, the object of the present invention is to solve the problems of the above-mentioned conventional methods for producing metal fibers, and to reduce the production unit price as well as silver and copper which have been difficult to produce in the past. The present invention provides a method capable of producing most of plastically deformable metals, including aluminum, etc., into metal fibers.

However, it is difficult to produce metal fibers by extrusion processing of metal powders because the joining of metal particles occurs during extrusion, and it is difficult to separate individual fibers after extrusion. It is a thing.

Another object of the present invention is to provide a method for producing metal fibers, which prevents the joining of metal particles during plastic deformation of the metal powder and facilitates separation between individual fibers after drawing. It is provided.

[0011]

In order to achieve the above-mentioned object of the present invention, the method for producing a metal fiber according to the present invention provides a metal powder of a predetermined size, which can be finally separated from each other. In order to facilitate the pretreatment, the pretreated metal powder is compressed, molded and stretched at a predetermined processing ratio to obtain a wire rod, and the drawn metal fiber is separated from the processed wire rod. Including the step of obtaining.

Further, according to the present invention, as a treatment method for preventing the metal particles from being joined during the plastic deformation step of the metal powder and easily separating the metal fibers even after the drawing process, 1) A method of pre-oxidizing the surface of the metal powder. (2) A method of plating a different metal on the surface of the metal powder. (3) A method of mixing the metal powder with a salt, oxide or carbon black. Now, let's explain each of the above methods in detail.

In the case of (1), the surface-oxidized metal powder having an appropriate size is compression-molded at room temperature, and then the extrusion ratio is selected in consideration of the required length and diameter. Although the metal does not oxidize the extruded wire, the metal oxide is immersed in an acid solution that selectively oxidizes it to precipitate out the oxide remaining between the metal fibers. As a result, the individual metal fibers separated and sank. In the case of (2), the same process as in (1) is performed, but a solution is selected in which the plated layer is preferentially precipitated in the final fiber separation process. In the case of (3), after extrusion, treatment with a solution that selectively dissolves salts or oxides, or in the case of carbon black, this is oxidized and converted into CO, CO _2, etc. Therefore, the metal fibers can be easily separated.

In the above method, the diameter and length of the resulting metal fiber can be arbitrarily adjusted by adjusting the extrusion ratio and selecting the diameter of the powder to be charged, and the simple extrusion and separation process can be used to easily prepare the metal. In terms of being able to manufacture fibers, it has the advantage of being able to overcome the problems of shape limitation and manufacturing cost due to existing manufacturing processes.

The term "metal powder" referred to in the present specification is used as "containing a powder of elemental metal or its alloy", and the method for producing the powder itself has certain limitations. Nor. At the same time, although the present invention presents only the case where the drawing process is by extrusion, this is merely foreseeable, and it is not necessarily the case that other drawing processes such as drawing and rolling are excluded. .

[0016]

【Example】

Example 1: Manufacture of copper fiber using surface oxidation and extrusion of powder 1) Copper powder manufactured by a high-pressure spraying device is classified by a powder classifier to obtain powder having a size of 30-300 μm at 800 ° C.
It is oxidized for 0 minute to form a copper oxide (CuO, Cu ₂ O) layer of about 5 μm on the surface of the powder. 2) The surface-oxidized copper powder manufactured by the method of 1) is put into a mold and compressed and molded. The size of the mold is 70m in diameter
m, height 150 mm, molding pressure is 10 Kgf / m
It was m ² . 3) The compression-molded body of the surface-oxidized copper powder produced by the method of 2) is extruded at an extruding ratio of 200. The extruded material thus produced has a diameter of 5 mm. 4) The extruded material extruded in 3) is treated with 0.2 M sulfuric acid (H ₂ SO
₄ ) When immersed in an aqueous solution, the diameter is 2-20 μm and the length is 6
-50 mm copper fiber is extracted and exits.

Example 2: Manufacture of silver fiber using electroless plating and extrusion 1) Silver powder manufactured by a high-pressure spraying device is classified by a powder classifier into powder having a size of 30-300 μm, and electroless Nickel is plated by the plating method. At the time of electroless plating, the concentration of the plating solution is nickel sulfate (NiSO ₄ ) 0.1M, sodium hypophosphite sodium (NaH ₂ PO ₂ ) 0.3M, and lacsan 0.2.
M, the temperature of the solution is 90 degrees Celsius, and the plating time is 4 hours. The plating is performed twice under the same conditions to increase the thickness of the plating layer. The nickel layer plated by such a method has a thickness of about 8 μm. 2) For the nickel coating manufactured by the method of 1), the powder is put into a mold and compressed and molded. 3) The nickel coating prepared by the method of 2) is extruded from a powder compression molding at an extrusion ratio of 200. The extruded material thus produced has a diameter of 5 mm. 4) When the extruded material extruded in 3) is electrolyzed in a 0.2 M nickel sulfate aqueous solution using both electrodes, the diameter is 2 to 20 μm.
Silver fibers having a length of m and a length of 6 to 30 mm are extracted and emerge.

Example 3 Production of Silver Fibers Using Molten Sodium Chloride 1) Sodium chloride (NaCl, purity of 88% or more) was melted in a graphite crucible and maintained at 940 degrees Celsius. The crucible has an inner diameter of 50 mm and a height of 450 mm, and the inside is 5 to facilitate separation of the solidified body after solidification.
I leaned. 1 manufactured using a high pressure spray device
Pre-heat a silver powder of about 00 μm to 500 degrees Celsius, add about twice the weight of molten sodium chloride, and then add 30
It is held for a minute and then solidified to form a bar in the form of silver powder dispersed in sodium chloride. 2) Express the rod made in 1) with an extrusion ratio of 200. The extruded material thus produced has a diameter of 5 mm. 3) When the extruded material extruded in 2) is immersed in water at 80 degrees Celsius, sodium chloride is dissolved in the water and the diameter becomes 15-2.
Silver fibers having a diameter of 0 μm and a length of 10 to 30 mm are separated and emerge.

Example 4: Manufacture of silver fiber using a mixture of sodium chloride and silver powder in powder form 1) Sodium chloride (NaCl, purity of 88% or more) was ball-milled for about 10 hours. Grind to make a powder form with an average diameter of 30 μm. 2) The weight ratio of the sodium chloride powder prepared in 1) to the silver powder having an average diameter of 100 μm produced by a high pressure gas atomizer in a weight ratio of 1:
Mix in a ratio of 2 and knead with a V-cone type kneader for about 5 hours. 3) The mixture of sodium chloride and silver powder produced by the method of 2) is put into a mold and compressed and molded. 4) The mixed molded body of sodium chloride and silver powder prepared in 3) is extruded at an extruding ratio of 200. The extruded material thus produced has a diameter of 5 mm. 5) When the extruded material extruded in 4) is immersed in water at 80 degrees Celsius, sodium chloride is dissolved in water and the diameter becomes 15-20.
Silver fibers having a size of 10 μm and a length of 10-30 mm are separated and emerge.

Example 5: Production of silver fiber using a mixture of carbon black and silver powder 1) Carbon black and silver powder having an average diameter of 100 μm produced by a high pressure gas atomizer were mixed in a weight ratio of 1 :. Mix in a ratio of 4 and knead for about 5 hours with a V-cone type kneader. At this time, ethyl alcohol (C ₂
H ₅ OH) is added to about 1/2 of the weight of carbon black. 2) A mixture of carbon black and silver powder manufactured by the method of 1) is put into a mold and compressed and molded. 3) A mixture of carbon black and silver powder prepared in 2) is extruded at an extruding ratio of 200. The extruded material thus produced has a diameter of 5 mm. 4) When the extruded material extruded in 3) is heated to 550 degrees Celsius, carbon is oxidized and vaporized by carbon monoxide (CO) or carbon dioxide (CO ₂ ), with a diameter of 15-20 μm and a length of 10 The silver fibers, which are -30 mm, come out separately.

[0021]

Industrial Applicability When the metal fiber is manufactured by utilizing the plastic deformation of the metal powder as in the present invention, the manufacturing unit cost is not only considerably low compared with the existing method for manufacturing the metal fiber, but also the manufacturing is difficult until now. It is possible to make most of the plastically deformable metals including silver, aluminum, copper, etc. that have been described above into metal fibers. In addition, based on the fact that the ratio of fiber length to diameter in metal fibers can be freely adjusted, metal powder is substituted for metal powder in many fields, such as conductive paints that have used metal powder until now, and the final product The characteristics of can be improved.

 ─────────────────────────────────────────────────── ───Continued from the front page (73) Patent holder 594071642 Kim Mun Jin Korea, Seoul, Soda Emunuk, Yoon Dong, 182, Hong Kyung Apt 21-403 (73) Patent holder 594071653 Kim Ki Hong Republic of Korea, Kyunggyi-do, Yuijeongbushi, Yong-kyun-don, 241, Yong-kyun Apt 205-307 (72) Inventor Kim-don-ik Republic of Korea, Jun-rap-g-do, Khunsang-si, Naung-don, Lotte Apt 102 -1105 (No address) (72) Inventor Kim Seung Kyun South Korea, Junrapuk Doo, Khun San Si, Naung Dong, Lotte Apt 101-1003 (No address) (72) Inventor Kim Mun-jin South Korea ， Ur, Sodaemun - click, yo Nhi - Don, 182, Hongyon Epi Ti 21-403 (72) inventor Kim key - Hong Korea, Kyongi - dough, Yuijo Nbu - Shi, Yongyundon, 241, yo Ngyun by API tea 205-307

Claims (10)

(57) [Claims] 1. A step of pre-treating a metal powder of a predetermined size to facilitate separation between the finally obtained metal fibers,
Manufacture of a metal fiber including a step of compressing and molding the pretreated metal powder and stretching the metal powder at a predetermined processing ratio to obtain a wire rod, and a step of separating the stretched metal fiber from the processed wire rod. Method. 2. The method for producing a metal fiber using a metal powder according to claim 1, wherein the drawing process is an extruding process. 3. The metal powder according to claim 2, wherein the metal powder is Al.
And Al alloy powder, Ag and Ag alloy powder, Ni and N
i alloy powder, Cu and Cu alloy powder, Ti and Ti alloy powder, Co and Co alloy powder, Fe and Fe alloy powder,
And a method for producing a metal fiber using a metal powder, which is a powder obtained by plating these powders with Ni, Ag, Cu, Au, Pt, or one or more mixed powders. 4. The method according to claim 1, claim 2 or claim 3, wherein the pretreatment is to oxidize the surface of the metal powder to form a metal oxide layer. A method for producing metal fibers using metal powder, which comprises treating with a solution in which the metal oxide layer is selectively precipitated to separate the metal fibers. 5. The method according to claim 1, claim 2 or claim 3, wherein the pretreatment involves plating a surface of the metal powder with a different metal different from the powder metal, and A method for producing metal fibers using metal powder, which is characterized in that the metal layer is treated with a solution in which the plating layer of different metals is selectively precipitated in order to selectively separate the metal fibers. 6. The pretreatment according to claim 1, claim 2 or claim 3, wherein the pretreatment is a metal powder and a salt, oxide or carr.
A method for producing a metal fiber using a metal powder, which comprises mixing bon black. 7. The pretreatment according to claim 6, wherein the metal powder is added to the molten salt in a predetermined ratio and maintained for a certain period of time and then solidified to disperse the metal powder in the solid salt. A method for producing metal fibers using a metal powder, which comprises treating with a solution in which the salt is selectively dissolved in order to separate the metal fibers from the wire. 8. The metal powder according to claim 6, wherein the pretreatment comprises mixing metal powder and powder of salt, oxide or carbon black at a predetermined ratio to prepare a mixed powder. For producing a finished metal fiber. 9. The production of metal fiber using metal powder according to claim 6, wherein the salt is one of sodium chloride, barium chloride, potassium chloride, potassium carbonate and sodium carbonate. Method. 10. The salt according to claim 7 or 8, wherein the salt is sodium chloride, barium chloride, potassium chloride,
A method for producing metal fibers using metal powder, which is one of potassium carbonate and sodium carbonate.