JPS6018131B2 - ferromagnetic metal powder - Google Patents

Description

Detailed Description of the Invention The present invention relates to a ferromagnetic metal powder and a magnetic recording medium using the same, and in particular to a ferromagnetic metal having high coercive force, high saturation magnetization, and excellent oxidation resistance. Concerning powder and magnetic recording media subjected to high-density recording.

Ferromagnetic powders conventionally used in magnetic recording media include:
These included maghemite, cobalt-doped maghemite, magnetite, cobalt-doped magnetite, bertolide compounds of maghemite and magnetite, bertolide compounds of cobalt-doped maghemite and magnetite, and chromium dioxide.

However, the magnetic properties of these ferromagnetic powders, such as coercive force (Hc) and maximum residual magnetic flux density (Br), are insufficient for use in so-called high-density recording. (below), the narrowed one in the truck (approximately 100
It was not very suitable for magnetic recording below the mountain surface.
Recently, ferromagnetic powders with characteristics suitable for high-density recording have been actively developed, and 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.

[For example, Japanese Patent Publication No. 36-11412, Japanese Patent Publication No. 36-11412,
Ichimatsu Publication No. 23, Publication No. 14809, Special Publication No. 39-3807, Publication No. 8026-8026, Special Publication No. 8027-1977, Publication No. 1516-1977
No. 7, Japanese Patent Publication No. 40-1689 (U.S. Patent No. 318682y specification), Hakama Koketsu No. 41-12096, Japanese Patent Publication No. 41-14818 (U.S. Patent No. 31)
90748 Specification), Japanese Patent Publication No. 42-24032, Japanese Patent Publication No. 43-3 Matsu No. 1, Japanese Patent Publication No. 43-22394
Publication number, Samurai Publication No. 43-292 Iso Publication, Special Publication No. 44-14
Publication No. 471, Special Publication No. 44-27942, Publication No. 755 of Special Publication No. 46-Sho, Publication No. 417 of Taruko No. 47-1,
Samurai Publication No. 47-411, Tsubaki Publication No. 48-2928, Japanese Unexamined Patent Publication No. 47-38523, etc.] 2) Acicular oxyhydroxides or those containing pond metals, or these Method Z for reducing acicular iron oxide obtained from oxyhydroxide.

[For example, Japanese Patent Publication No. 35 General Publication No. 62, Special Publication No. 37-1
Publication No. 152, Hakama Kosho No. 39-20335, Hakama Kosho No. 39-20939, Special Publication No. 46-24833, Special Publication No. 47-29706, Special Publication No. 47-3
Publication No. 0477 Z (U.S. Patent No. 35985 Congee Specification)
, Tsubaki Koukai No. 47-39477, Mochikai Sho 46-505
7 (U.S. Patent No. 36340), JP-A-46-71, JP-A-48-24952,
Japanese Unexamined Patent Publication No. 48-79153, Special Publication No. 48-8239
Publication (U.S. Patent No. 2360721 specification), U.S. Patent No. 360722 specification, U.S. Patent No. 37027
3) A method of vaporizing a ferromagnetic metal in a low-pressure inert gas.

2 [For example, Japanese Patent Publication No. 46-2562, Japanese Patent Publication No. 47-4131, Japanese Patent Publication No. 47-27718, Japanese Patent Publication No. 48-256
No. 62-25665, Mochiseki No. 48-31166, Tokbatsu No. 55400, Samurai Kai No. 48-81
Publication No. 092, Hakama Kosho No. 49-1532, etc.]
34) A method of thermally decomposing a metal carbonyl compound. [For example, Mochiko Sho 39-1004 Publication, Special Publication Floor 40-3
No. 415, Japanese Patent Publication No. 45-1 Madaraji, US Pat. 49-2679y, etc.] 5) A method in which ferromagnetic metal powder is electrically folded using a mercury cathode and then separated from mercury.

[For example, Special Publication No. 35-1291, Special Publication No. 36
Ichishi No. 6bi Publication, Special Publication No. 36-5513, Publication No. 787-1987, Publication No. 15525-1971,
Japanese Patent Publication No. 40-18123, Japanese Patent Publication No. 40-9605 (U.S. Patent No. 3198717), Publication of Tsubaki Publication No. 4
5-19661 (U.S. Patent No. 315665 specification), U.S. Patent No. 3262812 specification, etc.] 6)
A method of reducing a solution containing a ferromagnetic metal salt by adding a reducing agent.

[For example, Hakama Kosho Sou-2052 P Publication, Hakama Kosho Soichi 2
Publication No. 6555, Publication No. 43-20116 of Fin Kosho, Publication No. 45-149 of Tsubaki Kouki, Publication No. 45-149 of Hakama Kosho,
Hakama Publication No. 47-17820, Special Publication No. 47-16052
Publication No., Hakama Publication No. 47-41718, Special Publication No. 47-47-
No. 41719 (U.S. Patent No. 3607218), U.S. Patent No. 47-1353 (U.S. Pat. No. 375-66), U.S. Pat.
Publication No. 7-42252, Special Publication No. 47-42253, Publication No. 48-44194, Publication No. 48-44194, Publication No. 48-797
Private publication, Bikansho No. 48-82396, U.S. Patent No. 320 General Specification, U.S. Patent No. 76 Patent Specification,
U.S. Patent No. 3,535,104, U.S. Patent No. 356
No. 7525, US Pat. No. 3,661,556, US Pat. No. 3,663,318, US Pat. No. 36
No. 69643, U.S. Pat. No. 3,672,867, U.S. Pat. No. 3,726,664, etc.] The ferromagnetic metal powder of the present invention can be obtained by any method among the above-mentioned methods, but in particular, 6). The method is preferred.

In general, ferromagnetic metal powder obtained by each of the above methods has the disadvantage that fine particles with a particle size of less than a micron, which is suitable for magnetic recording media, are oxidized in the air, especially as humidity increases, and in particular, the main component is Fe. The trend was significantly larger around this time. Furthermore, the mirror orientation was also more likely to be oxidized as the magnetic resistance was higher. Therefore, high saturation magnetization is one of the outstanding characteristics of ferromagnetic metal particles. s was not saved. In addition, the surface of the particles was very active and tended to have poor dispersibility with the binder. Various studies have been made to solve these problems. For example, examples of attempts to make the composition oxidation resistant by adding non-magnetic elements include Tsubaki Kosho No. 38-2052, No. 47-782, Mochikasho 48-128 Nebemura No. 48, 11
28 Funabaya Specification, U.S. Pat. No. 3,535,104, 36
There are proposals such as the specification of No. 3672867 in 6964. However, it is still not enough. The present invention was developed to eliminate the above-mentioned drawbacks.

An object of the present invention is to provide a ferromagnetic metal powder with high coercive force.

The second object of the present invention is high saturation magnetization.

An object of the present invention is to provide a ferromagnetic metal powder exhibiting s. A third object of the present invention is to provide a ferromagnetic powder with excellent oxidation resistance.

A fourth object of the present invention is to provide a ferromagnetic metal powder that has excellent dispersibility with a binder.

The fifth object of the present invention is to have high coercive force, high Bm, and high squareness ratio (B
r/Bm). A sixth object of the present invention is to provide a magnetic recording medium with an excellent S/N ratio.

The above objective is to obtain at least 7
5% by weight is metal, at least 8% by weight of said metal
is Fe, Fe-Co, Fe-Ni or Fe-Co-Ni
The remainder consists of Cr, Cn and B, and Cro. 1-4.
Weight % of Cuo. 1-2. Weight % of BO. 5-8.
This can be achieved by using a ferromagnetic metal powder for magnetic recording media which is contained in a proportion by weight of .

Here, it is preferable to further add 6% by weight or less of P. In the ferromagnetic metal powder for magnetic recording media of the present invention, at least 75% by weight, preferably 8% by weight.
is a metal, and at least 8% by weight of this metal is Fe.
, Fe--Co, Fe--Ni, or Fe--Co--Nj is the main component. Particularly preferably at least 4% by weight of the metal is iron. In addition to these metals, it is necessary to contain at least Cr, C, and B as described above, and containing P brings even better results (in the present invention, B
and P are also treated as metals). Through research by the inventors,
If Cr is less than the above range, the saturation magnetization of the particles (〇s)
If Cu is lowered, the oxidation resistance deteriorates, and if it exceeds the above range, the coercive force of the particles decreases.If Cu is less than the above range, the coercive force decreases, and if it increases, the oxidation resistance deteriorates extremely. If B is less than the above range, the coercive force will be lowered, and if B is larger than the above range, the coercive force will be lowered.

It was found that s and oxidation resistance significantly decreased. Therefore, in the ferromagnetic metal powder for magnetic recording media of the present invention, a balance can usually be achieved only when Cr, Cu, and B are within the above ranges (i.e., high Hc, high 〇s, and excellent oxidation resistance). ferromagnetic metal powder). Furthermore, the present inventors have found that when P is additionally added in a range of 6% by weight or less, the oxidation resistance is further improved without affecting the coercive force. P is 6. If the weight percentage exceeds , the OS tends to decrease and the particle uniformity decreases.
It was found that the distribution of coercive force became wide, making it unsuitable as a ferromagnetic metal powder for magnetic recording. The size of the ferromagnetic metal powder is 50 to 1000 A in the minor axis direction, preferably 2
00 to 500 A, 100 A to 2 mm in the direction of the long mirror, preferably 400 A to lr. However, it is preferred that the particle size be as uniform as possible. The ferromagnetic metal powder for magnetic recording media of the present invention contains metal oxides, metal hydroxides, or water in addition to the above-mentioned metal components. Although the ferromagnetic metal powder of the present invention can be prepared by each of the methods described above, it is particularly easily obtained by method 6).

That is, a ferromagnetic metal powder can be obtained by adding a reducing agent to a solution containing a salt of a ferromagnetic metal and reducing the solution. Specifically, acids and salts containing phosphinate ions as reducing agents, sodium borohydride, borohydride compounds such as dietylaminoborane and their derivatives, hydrazine and its derivatives, Md, Ca, A
Reduction is performed using such metal powder. In particular, it is preferable to use a borohydride compound as a reducing agent, since the ferromagnetic metal powder obtained inevitably contains boron. In this case, it is important to suppress the amount of boron contained to 8% or less; if it exceeds 8%, the tendency to generate hard non-magnetic borides as a separate phase increases and Not desirable as a powder. As binders used in conjunction with the production of magnetic recording media using the ferromagnetic metal powder according to the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. Thermoplastic resins include those with a softening temperature of 150 pm or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 100, 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, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer polymer,
Methacrylic acid ester styrene copolymer, polyvinyl chloride, pinylidene chloride acrylonitrile copolymer, putadiene 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/resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof.

Examples of these resins are Hakama Kosho 37-Fuku No. 77, 39-1
No. 2528, No. 39-19282, No. 40-534y,
40-20907, 41-948, 41-1405
Clock number, 41-16 spot 5, 42-6428, 42-1
No. 1521, No. 43-4623, No. 43-15206,
44-12 Isokou No. 7, 44-17 Group No. 7, 44-18232
No. 45-1402 pi, 45-14500, 47-18573, 47-ichimono 063, 47-ichimatsu 064,
47 Ichimatsu 0suji No. 47-Matsu 069 No. 47-22070
No. 47-27886, U.S. Pat. No. 3,144,352,
It is described in the same No. 3419420, the same No. 99789, the same No. 3713 No. 7, etc.

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 phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy polyamide resin, nitrocellulose melamine resin, and high molecular weight polyester resin. mixtures of soocyanate brepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycol/high molecular weight diol not triphenylmethane triisocyanates, These include polyamine resins and mixtures thereof. Examples of these resins are given in Japanese Patent Publication No. 39-1810.
No. 3, No. 40-9779, No. 41-7192, No. 41-8
No. 016, No. 41-14275, No. 42-1817y,
43-12081, 44-28023, 45-14
No. 501, No. 45-24912, No. 46-13103,
47-Shigeru No. 065, 47-22066, 47-220
No. 67, No. 47-22072, No. 47-22073, 4
7. -28045, 47-28048, 47-28
No. 922, U.S. Patent No. 3144353, U.S. Patent No. 332009
No. 0, No. 3751, No. 3597273, No. 37
It is described in No. 81210, No. 3781211, etc.

These binders may be used alone or in combination;
Other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is 10 to 20 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder. Additives include dispersants, lubricants, abrasives, and the like.

As a dispersant or stabilizer, caprylic acid, capric acid,
Fatty acids with 12 to 1 carbon atoms such as lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid (
R, COO day, R, is an alkyl group having 11 to 17 carbonates): alkali metal of the above fatty acid (Li, Na, K, etc.)
Alternatively, metal soaps made of alkali metals (Mg, Ca, Ba, etc.); lecithin, etc. are used.

In addition, higher alcohols having a carbon number of la or more, and sulfuric acid esters thereof, etc. can also be used. These dispersants are added in an amount of 1 to 2 parts by weight based on 10 parts by weight of the binder. Lubricants include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of a hard monobasic fatty acid with 12 to 1 carbon atoms and a monohydric alcohol with 3 to 12 carbon atoms, and carbon atoms. 17
A fatty acid ester or the like can be used, which is composed of one or more monobasic fatty acids and one alcohol having 21 to 23 carbon atoms in total. These lubricants are added in an amount of 0.2 to 20 parts by weight based on the weight of the binder 10. Regarding these, Hakama Kosho 43-2 Shigebara y issue, Tokuiso Sho 42-28647, Tokusawa Sho 43-8154
3, U.S. Patent No. 3470021, U.S. Patent No. 9 Matsu No. 35, U.S. Patent No. 97411, U.S. Patent No. 3523086, U.S. Patent No. 3
No. 625760, No. 3630772, No. 3 Wipe 2
Specifications of No. 53, No. 3 No. 7539, No. 3 No. 7725, BM Techica I Disclosure
e B mountain letion Vol. 9. M-7, Pag
e779, 0ece kite r, 1966 and ELECTRO
NIKI961, M. 12, Pa trout 380, etc. Commonly used abrasive materials include fused alumina, silicon carbide, chromium oxide, corundum,
Artificial corundum, diamond, artificial diamond, garnet, gemery (main components: corundum and magnetite), etc. are used. These abrasives have an average particle size of 0.05~
A size of 5 mm is used, particularly preferably 0.1 mm.
~2r. These abrasives are added in an amount of 7 to 2 parts by weight based on 10 parts by weight of the binder. Regarding these, Japanese Patent Application No. 48-26749 and U.S. Patent No. 300
No. 7807, No. 3041196, No. 3293066, No. 363091, No. 3687725, British Patent No. 1145 Milk No. 9, West German Patent No. 8 $211, etc. 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 r, preferably about 10 to 40 r, and materials used include polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and polycarbonate. be done. However, a rigid base material of metal may be more suitable for some applications. Methods for applying the magnetic recording layer onto the support include air doctor coating, play coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, Spray coat etc. can be used, and other methods are also possible.
These specific explanations are described in detail in "Coating Engineering" published by Asakura Shoten, pages 2 to 27 (Published in 1964, Section 2).

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. Ester series such as glycomonoethyl ether; ether, glycol dimethyl ether, glycol monoethyl ether,
Glycol ethers such as dioxane; tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; chlorine such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Carbonized hydrocarbons and the like can be used alone or in combination. By such a method, the magnetic layer coated on the support is optionally treated to orient the magnetic powder in the layer, and then the formed magnetic layer is dried. Further, if necessary, the magnetic recording medium of the present invention is obtained by subjecting it to surface smoothing processing or cutting it into a desired shape. The effects and advantages of the present invention are as follows.

○ Ferromagnetic metal particles exhibiting high coercive force can be obtained. ○
Ferromagnetic metal particles exhibiting high saturation magnetization are obtained.

○ Oxidation-resistant ferromagnetic metal particles can be obtained.

○ Ferromagnetic metal particles with good dispersibility with the binder can be obtained. A magnetic recording medium having high Hc, high squareness ratio (Br/Bm), and high Bm can be obtained. ○ A magnetic recording medium with an excellent S/N ratio can be obtained.

The present invention has embodiments as described below.

i Ferromagnetic metal particles obtained by adding a reducing agent to a solution containing a salt of a ferromagnetic metal to reduce the solution.

5. In Embodiment i, ferromagnetic metal particles obtained using at least one of a borohydride compound and a derivative thereof as a reducing agent.

Cup Embodiment d' Ferromagnetic metal particles obtained using sodium borohydride as a reducing agent.

iv. A magnetic recording medium obtained by dispersing and mixing the ferromagnetic metal powder according to the claims with a binder and coating the mixture on a non-magnetic support.

The present invention will be explained in more detail below using examples.

It will be readily understood by those skilled in the art that the components, 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 examples below.

Example 1 R, liquid sodium borohydride 1-OM.

Yu/Z However, (M, liquid solvent is water R, liquid solvent is 0.01N NaOH aqueous solution) the above M,
The liquid was added to 10 Ikari-kaku stainless steel containers, a DC magnetic field with an average ratio of 60 was applied, and the liquid was added to 10 Ikari-gun 3 cram schools while rotating at a rotational speed of 100 pm.

A rapid reaction occurred and was almost complete after 2 minutes. After separating the reaction mother liquor, it was washed with water, and a portion of the particles was taken and dried. Other particles were replaced with acetone and further replaced with butyl acetate.
Analysis of the dried sample revealed Fe58.6M%, Co
26.1 wt%, Crl. 4wt%, Cuo. Mochi%,
B3.2% (i.e. total metal content 89.0%)
Expressed as a relative ratio to %, Fe65.2Wt%, C
. 29-bi Wt%, Cr1.6M%, Cu○-7Wt%
, B3.6M%).

Also. s was 11 $mu/evening. 60q of this powder
After being left in 090%RH for 7 days, the OS is 101e.
It was mu/evening. The size of this particle is the average short axis (
When observed with an electron microscope, the diameter (approximately the same as that of one spherical particle) was 250△.

Also, the average long axis (1500A formed by tightly connecting spherical particles)
Met. Next, add 30 parts of this powder to 120 parts of butyl acetate.
Add butyl acetate so that the total amount is 0 parts, and then add 6 parts of oleic acid.
2 hours at 40 qo.

After that, the mixture was placed in a ball mill and kneaded for 1 hour, and then 22 parts of a triisocyanate compound (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added, followed by high-speed shear dispersion for 1 hour to obtain a magnetic paint.

This paint 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 magnetic tape thus obtained was supercalendered and slit into 1'2 inch pieces to obtain a videotape. The surface properties of the obtained tape were extremely good. The obtained tape had an Hc of 125 e, a B'/m of 0.86, and a Bm of 3400 Gauss.

Even after this tape was left in an atmosphere of 60% RH for 7 days, the surface properties were extremely good. Comparative Example-1 In Example-1, the M solution was mixed with 0.0% ferrous sulfate. Cobalt sulfate 0.308Mo/Z was used.

Particles and tape were obtained using the same formulation as in Example-1. Particle composition is Fe57.5M/%, Co25.1w
t% and B3.1wt%. 〇s is 10&mu/evening, 6 days after being left in a 090℃RH atmosphere for 7 days. s is 6
It was 2mu/evening. The size of the particles was 250 A on average short axis and 1000 A on average long axis. The shape was similar to that of the particles of Example 11, in which spherical particles were tightly connected in a chain. On the other hand, the Hc of the tape is 105e, Br/B
m was 0.83 and Bm was 2400 Gauss. After this tape was left in an atmosphere of 60q○ and 90% RH for 7 days, some rust had formed on the surface. Example-2 R, liquid Sodium borohydride 1.0 Mo/Yu (however, the solvent for M solution is water and the solvent for R2 solution is 0.01N NaOH aqueous solution) Example-1
In M, a sole liquid was used instead of the liquid, and in R, the same liquid was used.

Particles and tape were obtained in accordance with Example-1. The composition of the particles is OFe 58.5 wt%. Co25.9Wt%, C
rl. 4V 9%, Cuo. 6wt%, PO. 5M%, B
3.2wt% (i.e., total metal content 90.1w
Expressed as a relative ratio to t%, Fe64.9wt%,
Co28.7wt%, Crl. Removal%, Cu0.7wt
%, P0, Sakaki t%, B3.6wt%). OS is 12&m
After being left in a 90% RH atmosphere for 7 days. s was 11 mu/night. The particle shape and size were the same as in Example-1. The Hc of the tape is 125 e
, Br/Bm was 0.87, and Bm was 3600 Gauss.

Even after this tape was left in an atmosphere of 60q090% RHO for 7 days, the surface properties were extremely good. Comparative Examples 2 to 6 In Example 2, the amounts of potassium chromium sulfate and sodium steel sulfate phosphinate added were changed to obtain particles having the compositions shown in Table 1.

Table 1 (Shigeru is a member of the Japan Society of Weight Management) () Values in parentheses indicate relative ratios to the total metal content The properties of the particles and tapes obtained in Comparative Examples 2 to 6 were as shown in Table 2.

Table 2 *.

s'. ．． ．． Based on these results, Comparative Example 12 is an example in which Cu was added in addition to Fe and Co. The value of s' is low and the oxidation resistance is poor. Moreover, when it was made into a tape, high Bm could not be obtained. Comparative example-3
is an example in which Cr was added in addition to Fe and Co, but Hc was lower than in Examples 1 and 2, and the oxidation resistance was poor. Therefore, the Bm of the tape was also less than 3000 Gauss. Comparative Example 4 is an example in which Cu was contained in an amount of about 8.5% of the metal. s, os' and Br/Bm values become worse. Comparative Example 5 is an example in which Cr was contained in an amount of about 4.2% of the metal, but the decrease in Hc was particularly significant, and the squareness ratio when formed into a tape was slightly deteriorated. Comparative Example 6 is an example in which P is contained in an amount of about 6.6% of the metal, but the oxidation resistance deteriorates and the Br/Bm value deteriorates.

From the results of Examples 1 to 2 and Comparative Examples 1 to 6, the effects of the present invention are excellent due to the synergistic effect of Cr and Cu and the adjustment of the content.

Example-3 R3 liquid Sodium borohydride 0.9 added o〆/Z
Diethylamine borane 0.18Mo evening/evening (however
Dove liquid uses water as a solvent) R3 liquid uses a solvent of 0.01NNa○
5 solution) M in Example-1, M3 instead of the solution
Particles and tape were obtained in the same manner as in Example 11 except that R3 liquid was used instead of R liquid.

The composition of this powder is Fe69. Skin t%, Co3.7M%,
Njo. 7wt%, Crl. lwt%, Cuo. % of happiness
, B was 2.9 Wt% (that is, expressed as a relative ratio to the total metal content of 78 t%).
4. Wt%, Nio. 9 Wt%, Crl. 4M%, Cu
l. Owt%, B3.7wt%).

〇s is 125.2 mu/evening after being left in a 60q090%RH atmosphere for 7 days. s is 104. It was Tomomu/Yuu.
The Hc of the tape is 105, Br/Bmo. 80 Bm
It was 3500 Gauss.

The surface remained very good even after being left in 60°C 90%RH for 7 days.

Comparative Example 7 Particles and tape were obtained in the same manner as in Example 3 except that chromium potassium sulfate and copper sulfate were removed from the M3 solution.

The OS of this particle is 116. Eclipse mu/evening, 60℃90%R
After being left in an H atmosphere for 7 days. s is 60. It was Danmu/Yu. The Hc of the tape is 90 ratio, Br/Bm' is 0.8
It was 4Bm' or 2500 Gauss. Comparing Example 3 and Comparative Example 7, it is found that Cu and Cr are contained. It can be seen that particles with high s and improved oxidation resistance are obtained. Also, from the results of the tape, it is recognized that Hc increases and the tape has high Br/Bm and Bm values. Comparative Example-8 In Example-1, M, the sulfuric acid steel concentration in the liquid was 0.01Mo
A dry magnetic material was obtained by carrying out the reaction in the same manner as in Example 1, except that the reaction time was changed to evening/evening.

The analysis result of this sample is Fe57. Egg t%, Co26 skin t
%, Crl. 4wt%, Cu2.4M%, B3.1wt
%,Met. Hcl02e, osl04. ratio mu/
It was evening. After this powder was left for 7 days in 60 o 90% RH, the OS was 7 emu/night. Compared to the particles obtained in Example-1, the content of Cu was four times higher, and other factors were approximately the same, but the particles had poor moisture resistance and were easily oxidized. Example 14 Using M4 liquid instead of M liquid in Example 11, R,
The same liquid was used.

Particles and tape were obtained in accordance with Example-1. The composition of these particles is 82. 91 of the metal content in Sakaki t%
．． Skin t% is Fe, 3.7Wt% is Ni, 1.4M% is C
r. - 7 Wt% was Cu and 3.0 Wt% was B.
(However, mixed metals with a content of 0.1 wt% or less in the composition were excluded.) Hiss was 11 $mu/night at 60°C.
After being left in a 90% RH atmosphere for 7 days. s is 102. &m
u/It was evening. The Hc of the obtained tape was 109e,
Br/Bm was 0.82, and Bm was 60 Gauss at the base.
No change in the tape surface was observed even after it was left in an atmosphere of 60q090% RH for 7 days.

Example 5 However, water was used as the solvent. M5 solution was used instead of M solution in Example 1, R,
The same liquid was used.

Particles and tape were obtained in accordance with Example-1. The composition of these particles is 81% by weight of metals and 95% by weight of metals. % of the enemy is Fe, 1.3 Wt% is Cr.・7Wt% is Cu
, 3.Wt% of the enemy was B. (However, the content in the composition is 0
．． Contaminated metals of 1 wt% or less were excluded from the metal content. ).

s is 132. Danmu/evening, 6pi 090%RH atmosphere 7
OS after being left alone for several days is 101. It was planned/evening. The obtained tape had an Hc of 71 e, a Br/Bm' of 0.8 or more, and a Bm of 3610 Gauss. No change in the tape surface was observed even after it was left in an atmosphere of 60° C. and 90% RH for 7 days.

Claims (1)

[Scope of Claims] 1. In the ferromagnetic metal powder, at least 75% by weight is metal, and at least 80% by weight of the metal is Fe, F.
e-Co, Fe-Ni or Fe-Co-Ni, the balance being 0.1-4.0% by weight of Cr, 0.1-2.0% by weight of Cu and 0.5-8.0% by weight % B ferromagnetic metal powder for magnetic recording media. 2 In the ferromagnetic metal powder, at least 75% by weight is metal, and at least 80% by weight of the metal is Fe, F
e-Co, Fe-Ni or Fe-Co-Ni, the balance being 0.1-4.0% by weight of Cr, 0.1-2.0% by weight of Cu, 0.5-8.0% by weight %B and 6.0% by weight
A ferromagnetic metal powder for magnetic recording media consisting of the following P.