JPS5932523B2 - Manufacturing method of metal magnetic powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing metal magnetic powder mainly composed of metal iron.

Generally, magnetic powder mainly composed of metallic iron is Fe3o4
It has the advantage of superior magnetic properties such as coercive force (Hc) compared to iron oxide-based magnetic powders such as Fe2O3, and is in the spotlight as a recording element for various magnetic recording media including magnetic tapes. is bathed in

However, this type of magnetic powder is usually produced by heating reduction in the gas phase of a powder consisting of needle-like particles of iron oxyhydroxide or iron oxide obtained by heating and dehydrating it, so during heating reduction, the particles It is easy to lose its shape due to mutual sintering or partial melting of individual particles, and it has the disadvantage that magnetic properties are significantly deteriorated due to non-uniformity of particle size and loss of obliqueness. Furthermore, iron oxyhydroxide, which is the raw material mentioned above, is normally produced by blowing oxygen-containing gas into a suspension of iron hydroxide to oxidize it, but in addition to needle-like particles, dendritic particles are also produced. It tends to be a by-product and the particle size tends to be non-uniform.

The presence of such dendritic particles and non-uniformity in particle size not only directly affect the magnetic properties, but also become a factor that makes the sintering between particles more noticeable during the above-mentioned thermal reduction. Therefore, in order to obtain magnetic powder with excellent magnetic properties, it is necessary to suppress the by-product of dendritic particles in the production stage of α-iron oxyhydroxide, make the particle size uniform, and reduce the sintering of the particles during thermal reduction. Although it is necessary to prevent knots and deformation, there is no known method that is fully satisfactory. The inventors have discovered that according to a method of introducing an oxygen-containing gas into a suspension of ferrous hydroxide adjusted to an alkaline region, a metal can be finally obtained using the produced α-iron oxyhydroxide as a raw material. It has already been found that magnetic powder mainly composed of iron becomes dense particles and its magnetic properties are improved.

In the course of further research, this invention was developed in a method of carrying out the above-mentioned α-iron oxyhydroxide production reaction in an alkaline region, in which nickel hydroxide is present in a suspension of ferrous hydroxide, and the production reaction is carried out in an alkaline region. When thermally reducing α-iron oxyhydroxide or iron oxide obtained by heating and dehydrating it, a lower layer containing at least one compound selected from an aluminum compound and a zinc compound and an upper layer containing a silicon compound are formed on the particle surface of the reductant. When a double coating layer consisting of We discovered that it is possible to obtain magnetic powder that effectively prevents knotting and deformation and has excellent magnetic properties.
It has been reached.

There are various ways to make nickel hydroxide present in a suspension of ferrous hydroxide. For example, nickel hydroxide itself may be added to the suspension, but usually nickel hydroxide is present in the suspension or in water. It can be added in the form of various water-soluble nickel salts to the reaction system that produces ferrous oxide, and converted to hydroxide by adjusting the pH. In particular, hydroxide can be produced by the reaction of ferrous salt with an alkali. A method is recommended in which nickel hydroxide is simultaneously precipitated when ferrous iron is precipitated to form a coprecipitate.

By being present in a suspension of ferrous hydroxide, nickel hydroxide introduces an oxygen-containing gas into this suspension and α
- In the reaction for producing iron oxyhydroxide, it has the effect of suppressing the production of dendritic particles and making the particle size of precipitated particles uniform.

The amount is 0 in the atomic ratio of NlAe to ferrous hydroxide.
．． An amount of 0.001 to 0.15 is suitable; if it is too small, no substantial effect can be expected, and if it is too large, no further increase in effect can be expected, and there is also an adverse effect on magnetic properties. In addition, in this invention, one or more compounds selected from aluminum compounds, zinc compounds, and silicon compounds may be contained in the suspension of ferrous hydroxide together with the above-mentioned nickel hydroxide.

Adjusting these contents makes it possible to adjust the particle size of the α-iron oxyhydroxide that precipitates, making it possible to adjust the magnetic powder mainly composed of metallic iron that is finally obtained through thermal reduction to suit the application and desired performance. A suitable particle size can be obtained. moreover,
These particles remain trapped in an ionic state inside or on the surface of precipitated α-iron oxyhydroxide particles, and also exhibit the effect of suppressing sintering and deformation of particles during heat treatment steps such as thermal reduction and thermal dehydration. The aluminum compounds used above include aluminum sulfate, aluminum nitrate, and aluminum chloride; the zinc compounds used include zinc sulfate, zinc nitrate,
Silicon compounds such as zinc chloride include water-soluble silicates such as sodium orthosilicate, sodium metasilicate, potassium metasilicate, and water glass of various compositions.
When Me is the atom of aluminum, zinc, and silicon, the recommended amount is such that the atomic ratio of Me/Fe is 0.1 or less, and too much is not desirable because it causes deterioration of the magnetic properties.

In this invention, an oxygen-containing gas is introduced into a suspension of ferrous hydroxide to produce α-iron oxyhydroxide, and the reaction is carried out in an alkaline region, but there are various means for achieving an alkaline region. For example, in the common method of reacting an aqueous solution of a ferrous salt such as ferrous sulfate with an alkaline component such as sodium hydroxide to produce ferrous hydroxide, an excessive amount of an alkaline component is used; An alkaline component may be added later to the suspension of ferrous hydroxide obtained by various methods. In either case, it is sufficient that the pH of the suspension before introducing the oxygen-containing gas is in a highly alkaline region of 1 L or more, and the main component is metallic iron, which is finally obtained by the reaction in such an alkaline region. The magnetic powder particles become highly dense. The generated α-iron oxyhydroxide is washed with water,
After P filtration and drying, it is directly or heated and dehydrated to form iron oxide, which is heated to 300 to 60% in a reducing atmosphere such as in a hydrogen stream.
If heated at about 0°C, it becomes a magnetic powder mainly composed of metallic iron, but in this invention, a lower layer containing at least one compound selected from an aluminum compound and a zinc compound and a silicon compound are formed on the particle surface of the reductant. A double covering layer is formed, consisting of an upper layer containing: Due to the presence of this coating layer and the fact that the substance to be reduced is uniform and contains almost no dendritic particles, sintering and deformation of the particles during thermal reduction are effectively suppressed. To form the above coating layer,
For aluminum compounds, water-soluble salts such as aluminum sulfate, aluminum chloride, aluminum nitrate, or water-soluble aluminates such as sodium aluminate,
For zinc compounds, use zinc sulfate, zinc chloride, zinc nitrate, etc. For silicon compounds, use water-soluble silicates such as sodium orthosilicate, sodium metasilicate, potassium metasilicate, and water glass of various compositions, and create alkaline aqueous solutions containing these. It is also possible to disperse the reductant powder in the suspension and simply adsorb it on the particle surface, but preferably, by blowing carbon dioxide into the suspension or adding an acid, the aluminum component is made into a crystalline or It is deposited on the particle surface as amorphous hydroxide or alumina sol, hydroxide for zinc component, and silicate sol for silicon component.

The process of depositing the aluminum compound and/or zinc compound and the process of depositing the silicon compound take a step-by-step process in which the lower layer is deposited, followed by heat treatment, and then the upper layer is deposited. In addition, when iron oxide obtained by heat dehydration of α-iron oxyhydroxide is used as the reductant, both of the above adhesion treatments may be applied to α-iron oxyhydroxide before heat dehydration. However, it is also possible to perform the other deposition treatment on the iron oxide obtained by performing only one deposition treatment and then heating and dehydrating the iron oxide. In particular, when performing both deposition treatments in stages, heat treatment is performed at a temperature of 150°C or higher after deposition of the aluminum compound and/or zinc compound to change the composition of the coating layer to an oxide or hydrous oxide. Next, a method is recommended in which a water-soluble silicate is dispersed in an alkaline aqueous solution to neutralize the liquid and form a double coating layer on the particle surface. In addition to preventing the layer from leaching into the liquid during the latter deposition process, the magnetic properties of the resulting metallic iron-based magnetic powder are improved compared to simultaneous deposition processes and reverse order deposition processes. is good. The heat treatment in this case may also serve as the heat dehydration step for converting α-iron oxyhydroxide into iron oxide. The amount of the aluminum compound or/and zinc compound deposited is preferably 0.01 to 10 wt% in terms of (Al/Zn)/Fe atomic weight%; if it is too little, no substantial effect can be expected; if it is too much, On the contrary, there is a risk that the particles may become porous or lose their shape, and there are also problems in terms of magnetic properties. Also, is the amount of silicon compound adhered to the atomic weight of S1/Fe? 0.1 to 10wt01), preferably 0.1
The amount is ~5wt(f), and if it is too small, no substantial effect can be expected, and if it is too large, the saturation magnetization (σS′X)
5 tends to decrease. This invention will be specifically illustrated in Examples below.

Example 12009/10 114g/10)N was added to an aqueous solution of 1.51g/12009/10FeS04/7H20 with stirring.
Aqueous solution 0.11 and 2 in which iSO4 6H20 was dissolved
0.009/l concentration of NaOH aqueous solution was added, and F
PHL containing a coprecipitate of e(0H)2 and Nl(0H)2
A suspension of 2 or more was obtained.

Next, the liquid temperature was raised to 40°C, and air was blown into the liquid at a rate of 1.61/min for 10 hours to form α-F in which Ni was dissolved as a solid solution.
eOOH was obtained. After washing, filtering and drying this α-FeOOH, 109 of the α-FeOOH was collected and dispersed in 800 ml of water.
A mixed solution of ZnsO4 with a concentration of
By blowing until the value of 7 to 8 was reached, α-FeOOH coated with Zn(0H)2 was obtained. This α-FeOOH was dehydrated and fired in air at 300° C. for 2 hours to obtain α-Fe2O3. Subsequently, this α-Fe2O3 was dispersed in 800 ml of water, and while stirring, 100 ml of 1N-NaOH aqueous solution and 20 ml of Na4SlO4 aqueous solution with a concentration of 1 mO1e were added.
Then, CO2 gas is blown into the liquid until the pH of the liquid becomes 7 to 8, followed by washing with water, filtration, and drying. Fe2O3 (Zn/Fe=4.9wt0I), Si
/Fe=2wt (I:/) was obtained. Obtained α-Fe2
O3 was reduced in an electric furnace at a H2 flow rate of 11/min under the temperature and time conditions listed in Table 1 to obtain metallic iron powder containing Ni, Zn, and S1. The magnetic properties of this powder are shown in Table 1.
Example 2 α- of Ni solid solution obtained by the same method as Example 1
Using FeOOHlO9, it was dispersed in 800 d of water, and 100 ml of 1N-NaOH aqueous solution and 0
．． Al2(SO4)3 aqueous solution 2 with a concentration of 01m01e/l
0ml was added and mixed, and then 002 gas was blown into the liquid until the pH of the liquid became 7 to 8, followed by washing with water, filtration, and drying to obtain α-FeOOH coated with Al(0H)3.

This α-FeOOH was dehydrated and fired in air at 300° C. for 2 hours to obtain α-Fe2O3. Next, this α-Fe2
Disperse O3 in 800ml of water and add 1N- while stirring.
NaOH aqueous solution 50d and 1r]]) Add and mix 20ml of Na4SiO4 aqueous solution with a concentration of 1e/l, then blow CO2 gas into the liquid until the pH of the liquid becomes 7 to 8, water calcination, filter drying, Upper layer is SlO2, lower layer is Al
α-Fe2O3 (Al
//1? e=0.2wt%). This 500Tn9
was collected and heated in an electric furnace at a H2 flow rate of 11/min and a temperature of 500°C.
The mixture was heated and reduced for 1 hour to obtain metallic iron powder containing Nl, All, and Sl. The magnetic properties of this powder are
Hc=14000e1σs=154emu/9, σr/
σs=0.51. Reference Example In the method of Example 1, 35
α-FeOOH was precipitated under the same conditions as in Example 1 by blending various amounts of aqueous solutions in which 9/l(7)Al2(SO4)3.17H20 was dissolved.

FIG. 1 shows the relationship between the average major axis of the obtained α-FeOOH and the Al/Fe atomic ratio. Similarly, the above Al2(S
31.19/l(7)Zn instead of O4)3 aqueous solution
Average major axis and Zn of precipitated α-FeOOH particles when using an aqueous solution containing SO4 7H20 and when using a Na4SiO4 aqueous solution with a concentration of 20.09/l
The relationship between /Te and the atomic ratio of Sl/Fe is shown in the drawing. In the figure, curve A means All, curve B means Znl, and curve C means S1. Comparative Example 1 A metallic iron powder containing Nl and Si was obtained using the method of Example 1 and 7i62 without using the ZnsO4 aqueous solution and keeping all other conditions the same.

Hc of this powder = 9600e1σs = 156emu/9
, σr/0s=0.45. Comparative Example 2 In the method of Example 1 and Sample Waterfall 2, Zn and S
A metallic iron powder containing 1 was obtained.

Hc of this powder = 12500e1σs = 164emu/
9, σr/σs=0.49. Comparative Example 3 A metal iron powder containing Al and Ni was obtained using the method of Example 2 without performing the deposition treatment with the Na4SiO4 aqueous solution and keeping the other conditions the same.

Hc of this powder = 8000e1σs = 150emu/9
, σr/σs=0.43. Comparative Example 4 Metallic iron powder containing Ni was obtained using the method of Example 1, Sample 164, except that the deposition treatment with ZnsO4 aqueous solution and Na4SlO4 aqueous solution was not performed, and other conditions were the same.

Hc of this powder = 5600e1σs = 178emu/9
, σr/σs=0.28. As is clear from the results of the above Examples and Comparative Examples, according to the method of the present invention, α-iron oxyhydroxide with little contamination of dendritic particles and uniform powder size can be obtained, and α-iron oxyhydroxide can be directly or heated. When thermal reduction is performed using dehydrated iron oxide as a raw material, sintering and deformation of particles are extremely effectively suppressed, resulting in a magnetic powder mainly made of metallic iron with excellent magnetic properties.
Furthermore, if the production reaction of α-iron oxyhydroxide is carried out in the presence of aluminum compounds, zinc compounds, and silicon compounds, the particle size of the produced α-iron oxyhydroxide will change depending on the amount of the aluminum compound, zinc compound, and silicon compound, as shown in the drawing. It is possible to adjust the size to suit the purpose and performance.

[Brief explanation of drawings]

The drawing shows the amounts of aluminum compounds, zinc compounds, and silicon compounds used and the precipitated α-
FIG. 3 is a diagram showing the relationship with the average major axis of iron oxyhydroxide. A: Aluminum compound, B: Zinc compound, C: Silicon compound.

Claims (1)

[Claims] 1. Oxygen-containing gas is introduced into an alkaline suspension of ferrous hydroxide adjusted to a pH of 11 or more to produce α-iron oxyhydroxide or iron oxide obtained by heating and dehydrating it in the gas phase. When heat-reducing the powder to obtain a magnetic powder mainly composed of metallic iron, nickel hydroxide is present in the suspension, and aluminum compounds and A lower layer containing at least one compound selected from zinc compounds is applied and heat treated at a temperature of 150°C or higher, and then an upper layer containing a silicon compound is applied to form a double coating layer. A method for producing metal magnetic powder. 2 together with nickel hydroxide in a suspension of ferrous hydroxide,
The method for producing metal magnetic powder according to claim 1, which contains at least one selected from aluminum compounds, zinc compounds, and silicon compounds. 3. At least one compound selected from aluminum compounds and zinc compounds is deposited on the surface of iron oxyhydroxide or iron oxide particles to be subjected to thermal reduction, and this is heat-treated at a temperature of 150° C. or higher in a gas phase, The particles are then dispersed in an alkaline aqueous solution of a water-soluble silicate, the liquid is neutralized, and a silicic acid sol is deposited on the particle surface to form a double coating layer. 2. The method for producing metal magnetic powder according to item 2.