JPS6317886B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal powder mainly composed of iron and suitable as a magnetic material. More specifically, the particle length (long axis) of the present invention is 0.05
The present invention relates to a method for producing metal powder with a narrow particle size distribution range of ~0.5 μm and excellent dispersibility. When using metal powder as a magnetic material, the metal powder must have high dispersibility in various paints (inks), including its particle shape, the particles must be well aligned, and the particle length must be as small as possible. The following characteristics are required. In order to meet these characteristics, it is necessary that the particles of iron oxyhydroxide, which is the precursor of metal powder, are well aligned, that these particles do not aggregate, and that they are not sintered during the heat reduction treatment. The essential condition is that it has not happened. On the other hand, in order to align the iron oxyhydroxide particles and improve their dispersibility, it is necessary to control the growth of the particles during the production of iron oxyhydroxide.
At ~0.5 μm, the particle size distribution width is narrow, and it is extremely difficult to control the axial ratio (major axis/minor axis). Regarding the production of conventional metal powder, for example,
Many proposals have already been made, including JP-A No. 58-15930, JP-A-58-159315, JP-A-58-176903, and JP-A-58-192307. However, the metal powder obtained by these methods has problems such as a wide particle size distribution, irregular particles, and poor dispersibility when made into a paint. Further, for example, Japanese Patent Publication No. 59-562 describes a method of producing metal powder by hydrothermal treatment, but only one with a low coercive force can be obtained. The first object of the present invention is a method for producing magnetic metal powder that can produce metal powder that has excellent magnetic properties such as coercive force, has a narrow particle size distribution, and has good dispersibility when made into paints. Our goal is to provide the following. A second object of the present invention is to provide a method for producing magnetic metal powder that can overcome the drawbacks of conventional metal powder production methods. The purpose of the present invention is to produce iron and nickel hydroxides by reacting ferrous salts and nickel salts with caustic alkali, and after adding carbonate to this, oxygen-containing supply gas, produce nickel-containing iron oxyhydroxide, then 100
After hydrothermal treatment at a temperature of ~250°C, sodium silicate is deposited on the particle surface, filtered, and dried.
This is achieved by a method for producing magnetic metal powder, which is characterized in that it is heated and reduced with a reducing gas to produce a nickel-containing metal iron powder. In the present invention, ferrous sulfate, ferrous chloride, etc. are used as the ferrous salt, and nickel sulfate, nickel nitrate, etc. are used as the nickel salt.
The addition of nickel, in other words, the use of nickel salt, is effective in controlling the magnetic properties of metal powder, and also contributes to improving the dispersibility in coating. Ferrous salts and nickel salts are generally used as aqueous solutions by dissolving them in water. The appropriate concentration of the ferrous salt in the aqueous solution is about 0.1 to 1 mol/. The amount of nickel salt used is determined by the Ni/Fe (atomic ratio)
It is desirable that the amount is from 0.001 to 0.1; if the amount used is too small, there will be no effect of addition, and if it is too large, the particle size distribution will become wide and the dispersibility, magnetic properties, etc. will be adversely affected. As the caustic alkali, sodium hydroxide, potassium hydroxide, etc. are used, and sodium hydroxide is usually preferred. Caustic alkali is generally used in the form of an aqueous solution. The amount of caustic alkali used is
An appropriate amount is 1 to 2 equivalents relative to the ferrous salt. The temperature when reacting ferrous salts and nickel salts with caustic alkali is preferably 70°C or lower, preferably 10 to 50°C, as particles tend to become long if the temperature is too high. Oxides are formed. The carbonate added after producing iron and nickel hydroxides is not particularly limited as long as it can convert iron and nickel hydroxides into carbonates, but sodium carbonate, sodium bicarbonate, carbonate, etc. Sodium or ammonia carbonates such as ammonium, ammonium bicarbonate are preferably used. The appropriate amount of carbonate to be used is 1 to 2 equivalents, preferably 1.1 to 1.5 equivalents, relative to the hydroxide. By adding carbonate, iron and nickel hydroxides become ferrous carbonate, nickel carbonate, etc., but if too little carbonate is used, ferrous carbonate, nickel carbonate, etc. are produced. It is difficult to use, and even if there is too much, there is no particular advantage to increasing it. A suitable temperature for adding carbonate is 20 to 70°C; higher temperatures tend to have an adverse effect on particle size distribution. The oxygen-containing gas is generally supplied by blowing it into a slurry in which ferrous carbonate, nickel carbonate, etc. are produced by adding carbonate. Air is conveniently used as oxygen-containing gas. Oxygen-containing gases affect the oxidation rate of Fe ⁺² and the size of the particles produced, and Fe ⁺²
If the oxidation rate is too fast, the particles tend to become minute, and if it is too slow, the particles tend to become long and large. Therefore, it is desirable to appropriately control the particle size by adjusting the supply amount. The temperature when supplying oxygen-containing gas to produce nickel-containing iron oxyhydroxide is 20 to 70°C, preferably 30°C, in order to produce particles with good symmetry and shape.
Needs to be ~60℃. If the temperature is too high or too low, the dispersibility will be poor, the metal powder will tend to have a wide particle size distribution, and the magnetic properties will also tend to deteriorate. In the present invention, after supplying oxygen-containing gas to produce nickel-containing iron oxyhydroxide, it is necessary to perform hydrothermal treatment. etc. are further improved, and the dispersibility when made into metal powder becomes very good. If the temperature of hydrothermal treatment is too low, not only will it take a long time, but the effects of hydrothermal treatment will not be sufficiently expressed, and if the temperature is too high, α-Fe ₂ O ₃ will be produced.
The hydrothermal treatment temperature must be 100-250°C, especially 150-230°C. The hydrothermal treatment time is not particularly limited, but is generally selected from the range of 0.5 to 5 hours. Furthermore, in hydrothermal treatment, it is effective to maintain an alkaline pH of 10 or higher, preferably 10.5 or higher, and caustic alkalis such as sodium hydroxide and potassium hydroxide are preferably used to adjust the pH. . Autoclaves are generally used for hydrothermal treatment. Nickel-containing iron oxyhydroxide after hydrothermal treatment is
After coating the particle surface with sodium silicate, it is filtered and dried by a conventional method. When filtering, it is desirable to thoroughly wash with water until the pH reaches about 8 to remove impurities. A known thermal reduction method is employed to thermally reduce the nickel-containing iron oxyhydroxide, which has been subjected to hydrothermal treatment and has been over-dried, with a reducing gas to produce a nickel-containing metallic iron powder. A mixed gas of hydrogen and nitrogen is generally used as the reducing gas, but there is no particular restriction as long as it is a reducing gas. The reduction temperature is generally selected from the range 350-500°C. If the temperature is too low, it will take a long time; if the temperature is too high, the shape of the particles will deteriorate. As the reduction device, a rotary kiln, a retort furnace, a fluidized ring furnace, etc. are used. Next, the present invention will be explained by showing Examples and Comparative Examples. Example 1 In a cylindrical reactor with a content of 20, a solution of 520.9 g of ferrous sulfate [FeSO ₄ 7H ₂ O] and 16.0 g of nickel sulfate [NiSO ₄ 7H ₂ O] dissolved in 3 parts of distilled water ( A solution of 165 g of caustic soda [NaOH] dissolved in 1.5 g of distilled water was added dropwise to react while maintaining the temperature at 40°C.
Made into iron and nickel hydroxides. A solution of 255.8 g of ammonium carbonate [(NH ₄ ) ₂ CO ₃ ·H ₂ O] dissolved in 3 parts of distilled water was added to this hydroxide slurry, and the mixture was stirred at a temperature of 40°C for 6 hours.
Ferrous carbonate and nickel carbonate were prepared, the temperature was maintained at 50° C., and air was passed through at a flow rate of 4/min for 6 hours to produce nickel-containing iron oxyhydroxide. Next, 300g of caustic soda was dissolved in this slurry of nickel-containing iron oxyhydroxide.
The mixture was placed in a 20-degree autoclave and subjected to hydrothermal treatment at 180°C for 2 hours. After hydrothermal treatment, wash with distilled water until the pH of the slurry becomes 8, and add 20 g of sodium silicate [Na ₂ SiO ₃ ].
was gradually added to the surface of the nickel-containing iron oxyhydroxide and dried at 100°C for 10 hours to obtain a nickel-containing iron oxyhydroxide powder. Next, 100 g of nickel-containing iron oxyhydroxide powder was placed in a fluidized bed reduction furnace, and hydrogen gas was flowed at a flow rate of 4/min for 5 hours to reduce the mixture at 430° C. to obtain a nickel-containing metallic iron powder. The particle shape of the obtained nickel-containing metallic iron powder was observed using a transmission electron microscope (TEM). TEM
According to the photo, the average particle length (long axis) of 50 particles is
It was 0.18 μm. Furthermore, as a result of measuring the magnetic properties with a vibrating sample magnetometer (VSM), the coercive force (Hc) was 1440 Oe and the saturation magnetization (σs) was 135 emu/g. In addition, in order to examine the dispersibility and magnetic properties after forming into a paint, 20 parts by weight of nickel-containing metallic iron powder, 2.7 parts by weight of vinyl chloride-vinyl acetate copolymer, 16.7 parts by weight of methyl isobutyl ketone, 16.7 parts by weight of toluene, and a curing agent were used. (Product name: Coronate L) 0.8 parts by weight was mixed in a ball mill for 60 hours to form a paint, the resulting paint was passed through a sieve with a sieve mesh size of 3 μm, and the amount of nickel-containing metallic iron remaining on the sieve was examined ( (The pass rate is 100% when all of the material passes through the sieve.) The paint was also applied on a polyester film and the coercive force was measured. As a result, the accuracy was 97% and Hc was 1460 Oe. In addition, as a result of measuring the axial ratio (major axis/minor axis), specific surface area, and particle size distribution, the axial ratio was 7, and the specific surface area was 51.
m ² /g, and the particle size distribution was within the range of ± (plus or minus) 0.02 μm with respect to the average particle length. Examples 2 to 8 In Example 1, Ni/Fe (atomic ratio) was changed to 0.07 (Example 2), ammonium carbonate was changed to sodium carbonate (Example 3), and the amount of ammonium carbonate used was 299.1 g. (Example 4), the temperature during air circulation was changed to 50℃ (Example 5), the air flow rate was changed to 10/min (Example 6), the hydrothermal treatment temperature was changed to 230℃ (Example 7), and the reduction temperature and time were changed to 400°C for 6 hours (Example 8)
Otherwise, a nickel-containing metallic iron powder was produced in the same manner as in Example 1. The properties of the nickel-containing metallic iron powder were measured in the same manner as in Example 1, and the results are shown in Table 1. Comparative Examples 1 to 5 In Example 1, hydrothermal treatment was not performed (Comparative Example 1), nickel sulfate was not used (Comparative Example 2), and the temperature during air circulation was changed to 80 ° C. (Comparative Example 3) ), nickel-containing metallic iron powder (Comparative Example 2) was prepared in the same manner as in Example 1, except that ammonium carbonate was not used (Comparative Example 4), and the hydrothermal treatment temperature was changed to 280°C (Comparative Example 5). (does not contain nickel) was manufactured and its properties were measured in the same manner as in Example 1. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. Ferrous salts and nickel salts are reacted with caustic alkali to produce iron and nickel hydroxides, carbonate is added thereto, and oxygen-containing gas is supplied at a temperature of 20 to 70°C to produce nickel hydroxides. After producing iron oxyhydroxide containing iron oxyhydroxide and then hydrothermal treatment at a temperature of 100 to 250°C, coating the particle surface with sodium silicate, filtering, drying, and heating reduction with reducing gas to produce nickel-containing metal. A method for producing magnetic metal powder, characterized by making it into iron powder.