JPS5931204B2 - Method for producing ferromagnetic metal powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ferromagnetic metal powder,
In particular, the present invention relates to a method for producing ferromagnetic metal powder for magnetic recording media, which is suitable for high-density recording.

Ferromagnetic powders conventionally used in magnetic recording media include γ-Fe2O3 and Co-containing γ-Fe2o3Fe3o.
4. Co-containing Fe3o4, cro2, etc. were found. However, these ferromagnetic powders are not well suited for magnetic recording of signals with short recording wavelengths (approximately 10 microns or less). In other words, for use in so-called high-density recording,
Magnetic properties such as coercive force (Hc) and maximum residual magnetic flux density (Br) were insufficient. Recently, ferromagnetic powders with properties suitable for high-density recording have been actively developed. One of the target materials is ferromagnetic metal powder. The following methods are known as methods for producing ferromagnetic metal powder.

1) A method of thermally decomposing an organic acid salt of a ferromagnetic metal and reducing it with a reducing gas [e.g.
Publication No. 3807, Special Publication No. 1987-42 using phthalate
Publication No. 86, etc.].

2) A method of reducing acicular oxyhydroxides, those containing other metals, or acicular iron oxides obtained from these oxyhydroxides.

[For example, Japanese Patent Publication No. 39-20939]. 3) A method in which ferromagnetic metal is evaporated in a low pressure inert gas.

[Parable (Yo, Special Publication No. 47-27718]).4)
A method for thermally decomposing metal carbonyl compounds.

[For example, Japanese Patent Publication No. 40-3414 (US Pat. No. 3,228,882)] 05) A method in which ferromagnetic metal powder is electrodeposited using a mercury cathode and then separated from mercury.

[For example, Japanese Patent Publication No. 45-19661 (US Pat. No. 3,156,650). 6) A method in which a reducing agent is added to a solution containing a salt of a ferromagnetic metal for reduction.

[For example, Japanese Patent Publication No. 47-41718 using a phosphinate as a reducing agent, US Pat. No. 3,206,338 using a borohydride method, etc.]. The present invention relates to the dry reduction reactions shown in 1), 2), and 3) above, 4), and 5.
), 6).

Ferromagnetic metal powders obtained by dry and wet reduction reactions have the following problems.

It has poor magnetic stability and is particularly sensitive to moisture, and is gradually oxidized in the presence of moisture even at room temperature, and powders mainly composed of Fe often lose their magnetic properties. Therefore, oxidation occurs gradually in the post-treatment step after the reduction reaction, and the high Bm property, which is one of the excellent characteristics of ferromagnetic metal powder, tends to be lost. Various studies have been made to improve this problem.

For example, there are methods in which improvements are made by adding non-magnetic elements to the reaction bath, and methods in which additives such as organic compounds are added to the reaction bath.

On the other hand, the ferromagnetic metal powder obtained by wet reduction reaction was improved by heat treatment.
It is known from Publication No. 555 and the like.

The present invention provides ferromagnetic metal powder suitable for preventing oxidation in the post-treatment process of ferromagnetic metal powder and for use in magnetic recording media using a very simple method.

That is, it is obtained by treating a ferromagnetic metal powder obtained by a reduction reaction by adding a reducing substance to the powder when washing it in water or an organic solvent.

The first object of the present invention is to provide a method for preventing oxidation of ferromagnetic metal powder during the manufacturing process.

The second object is to provide a ferromagnetic metal powder with excellent moisture resistance.

The third objective is to provide a ferromagnetic metal powder with high coercive force (Hc).

A fourth object is to provide a ferromagnetic metal powder that has magnetic stability over time.

The fifth object is to provide a ferromagnetic powder that has excellent dispersibility with a binder.

The sixth object is to provide a ferromagnetic metal powder that has excellent properties as a magnetic recording medium for high-density recording.

Seventhly, it is an object of the present invention to provide a magnetic powder that can be used in permanent magnets, magnetic cores, magnetic fluid suspensions, and the like.

The present invention is characterized in that a ferromagnetic metal powder obtained by a wet or dry reduction reaction is brought into contact with a solvent containing a reducing substance. In the present invention, the reducing substance does not actively reduce the ferromagnetic particles, but rather prevents the oxidation of the ferromagnetic particles and stabilizes them by bringing them into contact with a liquid containing the reducing substance (activating the particles). It is used to gradually press down on the

This treatment provides good magnetic properties and stability over time. Specifically, it maintains high Hc, prevents deterioration of δs over time, and improves dispersibility with the binder. The reducing substance used in the present invention is partially or completely soluble in the solvent, and the redox potential is the same as the activity of (H+) in the solution.
When the activity of ``1'' or (0H-) is expressed as ``1,'' it is preferably expressed as a negative potential (±0 V or less). Specific examples include acids and salts containing phosphinate ions (alkali metals such as Li, Na, and K; Be, Ca,
Alkaline earth metals such as Mg and Ba; Al, Fe, CO
, metal salts such as Zn; ammonium salts, etc.); hydrides such as borohydride compounds such as sodium borohydroxide, potassium borohydride, diethylaminoborane, and methyldiborane, and their derivatives; hydrazine, hydrazine hydrate, hydrazine sulfate, etc. hydrazine and its derivatives; at least one or more salts of dithionite with alkali metals such as Li, Na, and K or alkaline earth metals such as Be, Ca, Mg, and Ba, hydroquinone, formalin, formic acid, etc. is used. The solvent used in the present invention is at least one or a mixture of two or more selected from water and organic solvents.

As the organic solvent, a polar organic solvent is preferred.

Polar organic solvents include alcohols, ketones, etc. that are completely or partially miscible with water. Specific examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, dimethyl sulfoxide, dimethyl formamide, tetrahydrofuran, and dioxane. The amount of the reducing substance contained in the solvent is practically preferably in the range of 0.00001 mol to 10 mol, particularly in the range of 0.0001 to 1 mol, based on the solvent 11.

It has been found that if the concentration is less than 0.00001 mol/11, the concentration becomes too thin and it is difficult to obtain the effects of the present invention.

It has also been found that if it exceeds 10 mol/l, it is not practical because it makes the ferromagnetic metal powder more active than necessary and imparts natural properties. The treatment temperature is preferably in the range of -10 to +120°C, particularly 10 to 80°C.

At temperatures below -10° C., even if a solution containing a reducing substance is used, the effects of the present invention cannot be obtained. That is, the slow reduction reaction for preventing oxidation performed in the present invention does not occur at this temperature, and the ferromagnetic powder cannot be stabilized. At temperatures above 120° C., the reduction reaction is not only a slow reduction reaction for preventing oxidation as performed in the present invention, but is further accelerated.

In the subsequent steps, it becomes more likely to be oxidized, making it impossible to obtain the effects of the present invention. The processing time and the ratio of powder to solvent are not limited and can be selected as appropriate, but 10 seconds to 24 hours, particularly preferably 1 minute to 10 hours, is suitable, and for storage. It may be left in the solvent for an even longer period of time. Further, although the pressure is atmospheric pressure, a change of about 0 atm to 5 atm does not pose a problem. When the solvent is an aqueous solution, it is preferable that the hydrogen ion concentration is less than 10-2 grams. If the amount exceeds that amount, the ferromagnetic metal powder may be dissolved. Among the reducing substances, those containing phosphinate ions or hydrazine are particularly preferred.

This is because phosphinate ions have a relatively strong reducing power.
It is thought that a trace amount of phosphorus is adsorbed to the ferromagnetic metal powder, and that the behavior of phosphorus is affected, but it is not certain. The method for producing the ferromagnetic metal powder used in the present invention is as follows: 1. A method of thermally decomposing organic acid salts of ferromagnetic metals and reducing them with reducing gas.

2. A method for reducing acicular oxyhydroxides, their compounds containing other metals, or acicular iron oxides obtained from these oxyhydroxides.

3. A method in which ferromagnetic metal is evaporated in an inert gas.

What was obtained by etc. As a wet method: 1. Method for decomposing metal carbonyl compounds 2. Electrodeposition of ferromagnetic metal powder using a mercury cathode. method of separating it from mercury.

3. A method of reducing a ferromagnetic metal salt in its solution.

etc. are used.

Particularly effective in the present invention are those obtained by a wet reaction method in which a ferromagnetic metal salt is reduced in its solution.

Specifically, acids and salts containing phosphinate ions as reducing agents; borohydride compounds and their derivatives such as sodium borohydride, diethylamineporan, and methyldiporan; hydrazine and its derivatives; metal powders such as Mg, Ca, Al, etc. It is a ferromagnetic metal powder obtained by reduction using

This ferromagnetic metal powder contains at least one of Fe, CO, and Ni.
Species, namely Fe, CO, Ni, Fe-CO, Fe-
The main components are Ni, CO-Ni, Fe-CO-Ni, and Al, Si, S, Sc, Tl, V,
Cr, Mn, Zn, Y, MO, Rh, Pd, Ag, Sn
, Sb, Te, Ba, Ta, W, Re, AU, Hg, P
Elements such as b, Bi, La, Ce, Pr, and Nd are added.

If the shape is granular, it is a chain of several to several dozen particles of about 100 to 1000 λ, and usually about 4 to several dozen particles.
A chain of 30 pieces is used.

If the shape is a token particle, the particle size is as described above and the ratio of the major axis to the minor axis is 3:1 or more.

In the present invention, a ferromagnetic metal powder obtained by such a method, for example, a ferromagnetic metal powder obtained by a redox reaction in an aqueous solution using sodium borohydride as a reducing agent, is separated from a reaction solution, By mixing and dispersing the powder with an aqueous solution containing sodium acid and washing the powder with water, oxidation during the washing process can be prevented.

Also, instead of water, a mixture of organic solvents that are miscible with water or
It is possible to use organic solvents. Furthermore, it is also possible to treat with water or a mixture of water and an organic solvent containing a reducing agent, and then replace the mixture with an organic solvent. At this time, it is an effective method to include a reducing agent in the organic solvent. )0
The thus treated ferromagnetic metal powder is directly dried in nitrogen, inert gas, or air.

Alternatively, it is immersed in an organic solvent. Usually a binder. (binder), mixed and dispersed, coated on the support, dried,
It is used as a magnetic recording medium in the form of tape, disk, sheet, card, etc. The reason why a high Bm value is obtained by treating the ferromagnetic metal powder with the solvent containing the reducing substance of the present invention is that the oxidation of the powder by oxygen dissolved in water during the washing process is prevented. This is thought to have the effect of stabilizing the unstable surface of the powder after reduction.

Adding the above-mentioned non-magnetic element or organic compound to a ferromagnetic metal salt and performing a reduction reaction to obtain a ferromagnetic powder with excellent oxidation resistance, etc., followed by treatment with a solvent containing a reducing agent according to the present invention. is a more effective method.

The ferromagnetic metal powder obtained by the present invention has a coercive force of 10 to 2
0000e or more and δS8Oemu/g or more have been obtained.

Heating the ferromagnetic powder obtained by these methods in a non-oxidizing atmosphere or in the presence of a trace amount of H2O or 02 is effective to further improve the effects of the present invention. This is a great method.

The present invention may be used in combination with these modification methods. As the binder used in combination with the ferromagnetic metal powder according to the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 15°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 2.
00 to 1,000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer,
Vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, wood acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid Ester styrene copolymer, urethane elastomer, nylon silicone resin, nitrocellulose
Polyamide resin, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene Copolymers, polyester resins, chlorovinyl ether acrylic acid ester copolymers, amino esters, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition.

Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, examples include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, nitrocellulose melamine resins, high molecular weight polyester resins, and isocyanate resins. mixtures of polymers, mixtures of methacrylate copolymers and diisocyanate polymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanates, polyamine resins and A mixture of these, etc. These binders may be used alone or in combination, and other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is in the range of 10 to 200 parts by weight per 100 parts by weight of the ferromagnetic powder. Are additives dispersants, lubricants, etc.? Polishing agents etc. are added.

As a dispersing agent or stabilizer, hydrofuric acid, capric acid,
Fatty acids with 12 to 18 carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid (
RlCOOH, Rl is an alkyl group having 11 to 17 carbon atoms); alkali metal of the above fatty acid (Li, Na, K, etc.)
Or metal soaps made of alkaline earth metals (Mg, Ca, Ba, etc.); lecithin, etc. are used for convenience. Ru.

In addition, Koken alcohols having 12 or more carbon atoms and their sulfuric esters can also be used. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. Lubricants include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of monobasic fatty acids with 12 to 16 carbon atoms and monohydric alcohols with 3 to 12 carbon atoms, and 17 carbon atoms.
Fatty acid esters made of monobasic fatty acids and monohydric alcohols having 21 to 23 carbon atoms in total can be used.

These lubricants are used in amounts of 0.2 to 100 parts by weight of binder.
It is added in an amount of 20 parts by weight. Commonly used abrasive materials include fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). These abrasives have an average particle diameter of 0.05 to 5 .mu.m, particularly preferably 0.1 to 2 .mu.m. These abrasives are added in an amount of 7 to 20 parts by weight based on 100 parts by weight of the binder. These are described in Japanese Patent Application No. 48-26749. The magnetic recording layer has the above composition dissolved in an organic solvent and applied as a coating solution onto a support. The thickness of the support is about 5 to 50 μm, preferably 10 to 40 μm.
It has a good μ degree, and the materials used include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and polycarbonate. However, a rigid base material of metal may be more suitable for some applications. Methods for coating the magnetic recording layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, truss sphere coating, gravure coating, scratch coating, cast coating,
Spray coating, etc. can be used, and other methods are also possible, and detailed explanations of these methods are given in [Coating Engineering], pages 253 to 277, published by Asakura Shoten (published on March 20, 1972). .

Organic solvents used during coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid. glycol,
Ester systems such as monoethyl ether; glycol ether systems such as ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; tar systems (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride ,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be used alone or in combination.

The effects and advantages of the present invention are as follows.

◎ Oxidation of the ferromagnetic metal powder during the process can be prevented and a powder exhibiting a high Bm value can be obtained. ◎ Moisture-resistant ferromagnetic metal powder can be obtained.

◎ Has magnetic stability. ◎ Coercive force (Hc) can be increased.

The present invention will be explained in more detail below using comparative examples and examples. It will be readily understood by those skilled in the art that the ingredients, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention. Therefore, the invention should not be limited to the following examples. Example 1 (Hereinafter, all parts indicate parts by weight) Solution B Sodium phosphinate 0.4M
/1C solution Sodium hydroxide (2N) 100 dA solution 11 and B solution 1/l were mixed and heated to 70° C. with gentle stirring.

Separately, A in a magnetic field (D.C) of 500°C at 30°C.
Solution C was added to a mixed solution of solution and solution B to perform an oxidation-reduction reaction. The reaction was completed in 15 minutes.

The liquid became transparent and black ferromagnetic metal powder was produced. The composition of this ferromagnetic powder was mainly CO, and contained about 2% by weight of P relative to CO. After separating this powder from the mother liquor using a Nutstie, N
After washing with an aBH4 aqueous solution of about 11 ml, the powder was washed with acetone and dried in a hot air dryer at 40° C. to obtain a ferromagnetic powder. (This sample is designated as P-1). Next, the following composition containing this powder was placed in a ball mill and sufficiently mixed and dispersed to obtain a magnetic coating material.

This coating material was applied to one side of a polyethylene terephthalate film having a thickness of 25 microns while applying a magnetic field to a dry thickness of 5 microns, and was dried by heating. The wide magnetic web thus obtained was supercalendered and slit into 1/2 inch cloth to obtain a videotape. The surface properties of the obtained tape were extremely good. This is designated as sample #T-1.

Example 2 (0.01N NaOH solution) Add 80 parts of the above M2 solution to a non-magnetic container and add 10 parts to the entire container.
R2 while applying a DC magnetic field of 000e and stirring gently.
20 parts of the liquid was added over 10 seconds to carry out a reaction to obtain ferromagnetic powder (the reaction was carried out at a temperature of 20°C).

One composition of this ferromagnetic powder had iron as its main component, and contained 11% by weight of CO and several % of B relative to the iron. After this powder was separated from the mother liquor using a Nutsuie, it was treated with an aqueous solution containing sodium phosphinate at a ratio of 5 t/l at a ratio of 100 parts to 1 part of the powder. After washing with methyl alcohol containing sodium phosphinate at a ratio of 0.17/l to remove moisture, one part was dried (referred to as sample P-2) and the remaining part was further replaced with butyl acetate. To 300 parts of this powder (the following parts represent parts by weight) were added 1200 parts of butyl acetate and 15 parts of sodium oleate to give 40 parts.
After stirring at ℃ for 2 hours to adsorb the oleate on the powder surface, 22 parts of a triisocyanate compound (trade name: Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added to the mixture and dispersed at high speed for 1 hour to form a magnetic paint. did.

This coating material was applied to one side of a polyethylene terephthalate film having a thickness of 25 microns while applying a magnetic field to a dry thickness of 5 microns, and was dried by heating.

The wide magnetic web thus obtained was supercalendered, slit into 1/2 inch cloth, and used for video tape. The surface properties of the obtained tape were extremely good. This tape will be referred to as sample T-2. Example 3 After obtaining ferromagnetic metal powder by the same reaction as in Example-2, the powder was separated from the reaction mother liquor, and then 1 hydrazine hydroxide was added.
The sample was washed with a solvent containing 1:1 of ethyl alcohol and water in a ratio of 0.7/l (powder to solvent ratio of 1:50 parts), then washed with ethyl alcohol, and replaced with butyl acetate.

At this time, a part of the sample was dried from ethyl alcohol (P-3). A magnetic paint was prepared in the same manner as in Example-2 and made into a tape. (This tape was designated as sample T-3) The surface properties were extremely good. Example 4 Oxalate containing Fe, CO, Ba (average particle shape 0.
5×0.06 μ) was decomposed in a firing furnace at 360° C. in a N2 gas stream, and then reduced in a hydrogen stream to obtain a ferromagnetic metal powder.

This powder was cooled to about 100° C., immersed in a solvent containing 5 parts of ethyl alcohol to 1 part of water containing sodium phosphinate at a ratio of 1 y/l, and taken out from the furnace. Then, after replacing the bath with acetone, it was immersed in a butyl acetate solution. A portion was dried (referred to as P-4), and the remaining portion was formed into a tape in the same manner as in Example 1. (This tape is designated as sample T-4) The composition of this ferromagnetic metal powder is Fe6O%-CO35%
-BalO%. Analysis by solid mass spectrometry revealed that a trace amount of P was mixed in. The surface properties of the tape were extremely good. Comparative Example 1 A reaction was carried out in the same manner as in Example 1, and black ferromagnetic metal powder was produced.

The composition of this ferromagnetic powder is also mainly composed of CO;
It contained about 2% by weight of P relative to O. Then NaB
Powder and tape were obtained in the same manner as in Example-1 except that ordinary water was used instead of H4 solution. The powder sample is called P-5, and the tape sample is called T-5. Comparative Example 2 A reaction was carried out in the same manner as in Example 2 to obtain ferromagnetic powder.

The composition of this ferromagnetic powder was similarly iron-based, and contained 11% by weight of CO and several % of B based on iron. Next, powder and tape were obtained in the same manner as in Example 2, except that ordinary water and methyl alcohol were used instead of water containing sodium phosphinate and methyl alcohol. The powder sample is called P-6, and the tape sample is called T-6. Comparative Example 3 Powder and tape were obtained in the same manner as in Example 3, except that a solvent containing no hydrazine hydrogen hydride was used in Example 3.

The powder sample is called P-7, and the tape sample is called T-7. Comparative Example 4 Powder and tape were obtained in the same manner as in Example-4 except that a solvent containing no phosphinic acid was used.

The powder sample is called P-8, and the tape sample is called T-8.
●Tables 1 and 2 show the comparison results of various characteristics of the above examples and comparative examples.

(*Under room temperature conditions, using a histroscope manufactured by Nippon Kagaku Kogyo.
Measured with BH-403A model.

Measured magnetic field shows the value when old = 4,0000e) (*Under room temperature conditions, Histroscope BH4 manufactured by Nippon Kagaku Kogyo)
Measured with O3A type.

In Table 1, P-1 and P-5, P-2 and P-6, P-3 and P-
7 and P-4 and P-8, it is clear that by treating the ferromagnetic metal powder according to the method of the present invention with a solvent containing a reducing agent, the saturation magnetization of the powder can be increased. Furthermore, it can be seen that the saturation magnetization after being left in 6'C9O%RH is also improved.

On the other hand, T-1 and T-5, T-2 and T-6 in Table 2,
From the comparison results between T-3 and T-7 and T-4 and T-8, it is clear that all tapes made using this powder can increase coercive force (Hc), but have poor dispersibility. A square-shaped ratio of soil was observed to improve the quality of the soil. From these results, it can be said that the ferromagnetic metal powder obtained in the example is a ferromagnetic metal powder suitable for high-density recording. Example 5 Example-2
Powder and tape were obtained in the same manner as in Example 2, except that formalin was used instead of sodium phosphinate as the reducing substance.

The saturation magnetization of the powder was 105 emu/f.

Also, the saturation magnetization after being left at 60°C and 90% RH for 7 days is 75.
It was emu/7. Tape Hc is 11900eBr
/Bm was 0.83. Example 6 In Example-2, Cr alum 0.008M/l was added to the M solution.
Powder and tape were obtained in the same manner as in Example 2 except for using the added powder.

The saturation magnetization of the powder is determined by measuring magnetic field No. = 96.5 emu/y at 20000e. Also 60℃90%R
The saturation magnetization after being left in H for 7 days was 87.2 emu/v. Tape Hc is 9700eBr/Bm is 0.8
It was 5. The present invention includes the embodiments shown below.

I) A method for producing a ferromagnetic metal powder in which the liquid is a polar solvent in the claims.

...) A method for producing a ferromagnetic metal powder in the above (I), wherein the polar solvent is at least one of water and an organic solvent.

) In the claims, the reducing substance is phosphinic acid,
A method for producing a ferromagnetic metal powder made of at least one member selected from the group consisting of phosphinates, borohydride compounds, derivatives thereof, hydrazine, derivatives thereof, dithionites, hydroquinone, formalin, and formic acid.

) A ferromagnetic metal powder that is a metal or alloy powder obtained by adding a reducing agent to a solution containing a salt of a ferromagnetic metal and reducing the ferromagnetic metal powder obtained by a wet reduction reaction in the scope of the claims. .

V) The ferromagnetic metal powder in the above (self), wherein the reducing agent is at least one of a boron hydride compound and a derivative thereof.

Claims (1)

[Claims] 1 Ferromagnetic metal powder obtained by wet or dry reduction reaction is added in an amount of 0.00001 mol to 10 mol per liter of solvent.
1. A method for producing a ferromagnetic metal powder, which comprises bringing the powder into contact with a liquid containing a molar amount of a reducing substance at -10°C to 120°C.