JPS6388806A - Highly dispersible magnetic iron powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture magnetic paints having high dispersion by attaching a basic gaseous component physically or chemically onto the surfaces of ferromagnetic metallic powder consisting of iron or mainly comprising iron. CONSTITUTION:A basic gas diluted with a non-oxidizing gas is brought into contact with ferromagnetic metallic powder composed of iron or mainly comprising iron. Ammonia, methylamine, pyridine, etc., can be used as the basic gas and nitrogen, helium, argon, etc., as the non-oxidizing gas. 0.05-2.0mueq/m<2> is sufficient as the quantity of the basic gas adhering on the surfaces of magnetic powder. The magnetic iron powder has extremely excellent dispersion, few holes and uniform particle size distribution, and the surfaces of the magnetic iron powder can display chemically superior interaction with a bonding agent and additives when mixing paints.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ferromagnetic powder mainly composed of metallic iron and a method for producing the same. More specifically, the present invention relates to iron or iron-based ferromagnetic powder that makes it possible to manufacture a highly dispersible magnetic paint, and a method for manufacturing the same.

The physical form of iron or iron-based ferromagnetic powder that makes it possible to manufacture highly dispersible magnetic paints is that the particles are not sintered together, and the particles are baked with few holes. , the particle size distribution must be uniform, and there must be little fine powder due to deformation, etc. In addition, from the viewpoint of chemical interaction, the surface of the magnetic particles must exhibit good chemical interaction with the binder and various additives used in preparing the magnetic paint.

In severe cases where good chemical interactions are not developed, the surface species of the magnetic powder can gel the binder used as the magnetic paint.

Furthermore, if magnetic powder is immersed in an organic solvent for a long time, the organic solvent may change in quality. For example, the trimerization reaction of methyl ethyl ketone is exemplified.

As mentioned above, iron or a proprietary powder characterized by iron, which makes it possible to produce highly dispersible magnetic paints, has a good physical form and binders and various additives used when formulating magnetic paints. It must also have surface properties that provide good chemical interaction with the agent.

Next, a commonly used method for producing iron or iron-based ferromagnetic powder will be exemplified.

Magnetic iron powder is generally produced by a method of thermally reducing acicular iron oxyhydroxide. Acicular iron oxyhydroxide is known to have α, β, and γ transformations, and the manufacturing method differs depending on each transformation type, but α-F is the starting material for magnetic iron powder for magnetic recording. e OOH is excellent because it has few twins and resin components and has a large acicular ratio of 1() after bending. More specifically, α on the alkali side in which oxygen-containing gas is passed through a suspension containing Fe(OH)2 and having a pH of 11 or more obtained by reacting a ferrous salt aqueous solution and an alkaline aqueous solution.
-1・'eo 0 H synthesis method is particularly excellent, and α-F″eoOH synthesized exclusively on the alkaline side is used as the starting material for magnetic iron powder.
i, Co, Mn, Cr5Zn, AI, Sl, Ca.

It is often the case that α-F eo OH is synthesized by co-precipitating these metal components in the presence of hydroxides such as Ti, Cu, Mg5Bi, Sn, etc., and used as a starting material.

To obtain magnetic iron powder mainly composed of metallic iron by thermally reducing acicular α-FeOOH, first, a-FeOOH is heated and dehydrated in a non-reducing atmosphere such as air to form iron oxide. There are known methods in which the iron oxide is thermally reduced in a reducing atmosphere such as hydrogen, and a method in which the step of converting into iron oxide is omitted and α-FeOOH is directly thermally reduced in a reducing atmosphere such as hydrogen.

During the above-mentioned thermal dehydration or thermal reduction, the acicular particles sinter or collapse, and the magnetic properties of the finally obtained magnetic iron powder, mainly composed of metallic iron, tend to deteriorate significantly. It is in.

Therefore, it is widely practiced to coat the surface of iron oxyhydroxide or iron oxide with a compound having a sintering prevention effect before thermal dehydration or thermal reduction.

The adhesion type is Si, AI, P, 8%Cr, Zn1C.
Compounds such as hydroxides, oxides, nitrates, and carbonates of a, Ti, and Zr may be used alone or in combination. Also,
During deposition, magnetic properties and thermal reduction properties are adjusted. N1, Co, Cu, AI? Compounds such as the above may be used in combination with the sintering prevention component.

The surface of heat-reduced iron or ferromagnetic powder mainly composed of iron is oxidized with an oxidizing gas with adjusted oxygen partial pressure to give it oxidative stability, and then it is made into a product. Methods for oxidizing the surface in a gas phase and methods in which iron or ferromagnetic powder mainly composed of iron is dipped in an organic solvent such as toluene and oxidizing gas is passed therethrough are known.

In order to obtain iron or iron-based ferromagnetic powder that makes it possible to manufacture highly dispersible magnetic paints using conventional technology, the key points in production are (1) particle size uniformity and resinous crystal 7
17- Production of needle-shaped iron oxyhydroxide, ■ Addition of adhesion components for the purpose of avoiding sintering and deformation of particles during heat dehydration and heat reduction processes, ■ Addition of adhesion components to prevent sintering and deformation. As you can see, from the perspective of producing highly dispersible magnetic powder, most emphasis is placed on producing magnetic iron powder with good physical form. It's dark.

The adjustment of the chemical aspects mentioned above is similar to the type and amount of the deposited components in the above item (①), so the type and amount of the deposited components are adjusted within a range that maintains good physical form and good magnetic properties. However, there is a limit to the ability to satisfy both of the two completely different characteristics of maintaining physical properties and adjusting the wR of chemical properties by simply changing the type and amount of the adhered components.
At present, conventional magnetic powders have insufficient dispersibility during the production of magnetic paints.

In the process of studying iron or iron-based ferromagnetic metal powder that provides high dispersibility and a method for producing the same, the present inventor discovered that the chemical properties of the magnetic powder surface could be changed to change the magnetic properties and physical form of the magnetic powder. The present invention was completed by discovering a method for independently aligning 14 directions in a preferable direction.

Thus, according to the present invention, magnetic iron powder has a basic gas component physically or chemically attached to the surface of iron or ferromagnetic metal powder containing iron as a main component, and magnetic iron powder is diluted with a non-oxidizing gas. Provided is a method for producing iron or a ferromagnetic metal powder containing iron as a main component, which comprises bringing a basic gas obtained by the above process into contact with iron or a ferromagnetic metal powder containing iron as a main component.

In the present invention, as basic gases, ammonia, methylamine, methylamine, trimethylamine, ethylamine, lopropylamine, 190-propylamine, n-butylamine, S-butylamine, 1-butylamine, aniline, pyridine, etc. are effective. It is. Examples of non-oxidizing gases that dilute basic gases include nitrogen,
Helium, argon, etc. can be used.

The amount of basic gas deposited on the surface of iron or ferromagnetic metal powder mainly composed of iron is determined by the dilution concentration at which the non-oxidizing property of the basic gas reaches a high level, the contact temperature and time between the diluted gas and the magnetic powder, and furthermore, The temperature and time at which the magnetic powder that has been brought into contact with the diluent gas is subsequently brought into contact with only the non-oxidizing gas can be freely controlled, and the conditions can be selected as appropriate depending on the type of basic gas used. The amount of basic gas adhering to the surface of the magnetic powder is not necessarily as large as it is good, but the amount of adhesion of basic gas evaluated by the change in acidity after treatment with basic gas on the surface of the magnetic iron powder is 0. 05
~2.0 μsq/m2 is sufficient.

As shown in Examples, the amount of attached basic gas can be quantitatively determined by analyzing the acidic groups on the surface of the magnetic powder.

It is not clear why the adhesion of a very small amount of basic gas significantly improves the dispersibility of magnetic powder, but it is known in the field of catalysts that adsorption of basic gas occurs selectively from strongly acidic sites. It is thought that too strong acidic groups have an adverse effect on dispersibility, and that this is the result of selective masking with basic gas. In order to reduce the amount of basic gas adhering to the surface of the magnetic powder, it is necessary to reduce the concentration of basic gas/non-oxidizing basic gas = 7- and to reduce the contact temperature between the magnetic powder and the mixed gas. One or a combination of two or more of the following methods may be used: increasing the treatment temperature, and further increasing the processing temperature when passing only the non-oxidizing gas through the magnetic powder after contact with the mixed gas.

A preferable treatment with a basic gas is to bring the basic gas diluted with a non-oxidizing gas into contact with iron or a ferromagnetic metal powder containing iron as a main component at a temperature of 0 to 200°C, and then to the non-oxidizing gas. This is achieved by contacting at a temperature of 0 to 500°C. Here, the degree of dilution of the basic gas with the non-oxidizing gas is preferably about 0.01 to 5%.

The magnetic iron powder of the present invention has extremely good dispersibility, and has extremely valuable properties when used in actual applications such as making magnetic iron powder into a tape.

A1 with a needle ratio of 15 and a specific surface area of 81 m2/g!
, F'e100 on the surface of α-Fe 00
atom! = 1.8 Si atoms, Nil atoms and Ca
O, 1) Deposition was performed in an amount equivalent to the JRT child.

The pH of 3% aqueous souffle of α-F”eo OH was adjusted to 1 (
), add the entire amount of No. 3 water glass, then add the entire amount of nickel nitrate while adjusting the pH of the slurry to 10 with 1N NaOH, and then The p I-1 was adjusted to 8 with 1N HN 03.

Next, an aqueous calcium nitrate solution was added, washed with water, and filtered to obtain a deposited powder.

The adhered powder was placed in an electric furnace set at 700° C. and treated for 4 hours to be heated and dehydrated to form hematite, and then treated in an H2 stream at 380° C. for 4 hours to form a ferromagnetic metal powder mainly composed of iron.

Next, the ferromagnetic metal powder is cooled to room temperature in a N2 flow mode, and a mixed gas of air/N2 whose partial pressure is adjusted to 0.1% is passed through to oxidize the surface of the ferromagnetic metal powder. A film was formed (the magnetic iron powder on which the oxide film was formed is hereinafter referred to as magnetic iron powder A).

When the magnetic properties of magnetic iron powder A were measured by applying a magnetic field of 10K (le), Hc 1550 0eσ9
1 28 eIIlu/gσr/σs
O151, the specific surface area is 53 m2/g, and the transmission type set r
- Microscopic observation revealed good physical shape with no sintering or particle collapse.

Mix ammonia gas diluted to 11,000 pp with nitrogen to magnetic iron powder A, and mix 5 gas per 1 kg of magnetic iron powder A.
After contacting at 100°C for 1 hour, the system was switched to nitrogen gas and the system was heated for 2 hours under nitrogen flow.
The temperature was raised to 50° C., treated at this temperature for 1 hour, and cooled to room temperature (the treated powder is hereinafter referred to as magnetic iron powder B).

When the magnetic properties of magnetic iron powder B were measured under the same conditions as magnetic iron powder A, Hc 1.550 0e 1,26 eIau/g σr/σs O,51 (i.e., almost the same as magnetic iron powder A). The specific surface area was 53 m27 g, and when observed with a transmission electron microscope, it had exactly the same image as magnetic iron powder A, and no change was observed in the physical form.

[Measurement of acidity on the surface of magnetic iron powder 1 The acidity on the surface of magnetic iron powder was measured by using vacuum-dried magnetic iron powder with a particle size of 80 mesh passes at N/. It can be determined by shaking the 11-butylamine-benzene solution and measuring the concentration of lobethylamine in the supernatant.

The acidity of magnetic iron powder A and magnetic iron powder B is 3°6 μeq each.
/m2.3.1μeq/fi12k.

It is thought that part of the surface acidic groups of the magnetic iron powder A is coated with the basic gas in the magnetic iron powder 13, and the amount of basic gas attached at this time is 0.5 μf! q/m2.

[Evaluation of sheet physical properties 1 300 parts of magnetic iron powder, VAGH (salt/vinyl acid heavy polymer, UC
After stirring and dispersing a mixture of 45 parts (trade name, manufactured by Company C), 175 parts of toluene, and 175 parts of methyl isobutyl ketone in a ball mill for 24 hours, a mixture of Takenate L-1
007 (urethane brevolimer, 2 [l Yakuhin product name)
2 parts, 15 parts of toluene and 15 parts of methyl isobutyl ketone.
1 part was added to a ball mill and stirred and dispersed for 1 hour to prepare a magnetic paint.

(b) The magnetic paint is applied to a polyester film with a thickness of 16 μI to a dry thickness of 3 μm, the metal powder is oriented in a magnetic field, and then dried. The surface of the magnetic layer is then calendered to a mirror-like finish. Process it and cut it to a predetermined width to obtain a specimen.

A sheet was prepared for magnetic iron powder A and magnetic iron powder B using the above recipe, and the sample was measured with a VSM in a magnetic field of 10 K ().
The results measured by e were as shown in the following table.

From Table 1, it is clear that magnetic iron powder in which part of the acidic groups on the surface of the magnetic powder is coated with basic gas provides high dispersibility.

X1j and L The needle ratio is approximately 15 and the specific surface area is 771112/g.
On the surface of Q-FeOOH containing i as a coprecipitated component of 1 atom to 00 Fe atoms, 4.5 Al atoms, Sil, O atoms, and Cab are present for each Fe1OO atom.

An amount corresponding to one atom was deposited.

No. 3 water glass and sodium aluminate were added to a 3% aqueous slurry of α-FeOOH whose pH was adjusted to 10, and then the p I-1 was adjusted to 8 with IN HNO3.

Next, after adding calcium nitrate water fB solution, wash with water,
A coated powder was obtained by filtration.

The adhered powder was placed in an electric furnace set at 700° C., treated for 4 hours, heated and dehydrated to form hematite, and then treated in an H2 stream at 450° C. for 3 hours to obtain a ferromagnetic metal powder mainly composed of iron.

Next, the ferromagnetic metal powder is cooled to room temperature under N2 flow, and the partial pressure is reduced to 0.1%. Conditioned air/N2
An oxide film was formed on the surface of the ferromagnetic metal powder by passing a mixed gas of (the magnetic iron powder with the oxide film formed thereon is hereinafter referred to as magnetic iron powder C).

When we measured the magnetic properties of magnetic iron powder C by applying a magnetic field of 10 KOe, we found that ! (c 1540 0e σs 121 evau/gσr/σs
0.50, and the specific surface area was 58112/g, and observation using a transmission type r-* microscope confirmed that the material had a good physical shape without sintering or particle collapse.

Magnetic iron powder ci = Mix 5N of methylamine gas diluted with nitrogen to 500 ppm per 1 kg of magnetic iron powder C.
After contacting at 200''C for 1 hour, the mixture was switched to nitrogen gas and cooled to room temperature (this treated powder is hereinafter referred to as magnetic iron powder).

When the magnetic properties of magnetic iron powder were measured under the same conditions as magnetic iron powder C, it was found that He 1550 0e σs 122 emu/gσr/σs
0.50 (that is, almost the same value as magnetic iron powder C), the specific surface area is 58 m2/g, and when observed with a transmission electron microscope, it has exactly the same image as magnetic iron powder C, and its physical form No change was observed.

[Measurement of acidity of magnetic iron powder surface] The acidity of magnetic powder measured by the same method described in Example 1 was 2°2 μeq/m2 for magnetic iron powder C and magnetic iron powder, respectively.
and 1.9 μeq/l112.

Therefore, it is considered that part of the surface acidic groups of the magnetic iron powder C is coated with the basic gas, and the amount of the basic gas attached is (), 3 μeq/m'.

In addition, a sheet was prepared in the same manner as in Example 1 and its magnetic properties were measured, and the results are shown in the following table.

From the table above, it is clear that magnetic iron powder in which part of the acidic groups on the surface of the magnetic powder are covered with basic gas brings about trade name dispersion.

Claims (1)

[Claims] 1. Magnetic iron powder in which a basic gas component is physically or chemically attached to the surface of iron or ferromagnetic metal powder containing iron as a main component. 2. A method for producing iron or a ferromagnetic metal powder containing iron as a main component, which comprises bringing a basic gas diluted with a non-oxidizing gas into contact with iron or a ferromagnetic metal powder containing iron as a main component. 3. A basic gas diluted with a non-oxidizing gas is brought into contact with iron or a ferromagnetic metal powder containing iron as a main component at a temperature of 0 to 200°C, and then the non-oxidizing gas is brought into contact at a temperature of 0 to 500°C. A method for producing iron or a ferromagnetic metal powder containing iron as a main component, characterized by contacting with iron or ferromagnetic metal powder containing iron as a main component.