JPS59153810A - Production of ferromagnetic fine metallic particle - Google Patents

Abstract

PURPOSE:To obtain ferromagnetic fine metallic particles having uniform particles and an improved magnetic characteristic by adding a different metallic compd. and ferrous salt to a suspension of alpha-iron oxyhydroxide to cause an oxidation reaction and to deposit the compd. thereon then subjecting the suspension to a reduction treatment. CONSTITUTION:An aq. soln. of a compd. of a different metal except iron, for example, NiSO4 and an aq. soln. of ferrous salt such as FeSO4 are added to an aq. suspension of alpha-iron oxhydroxide and the particles of the compd. of the different metal are deposited on the surface of the alpha-iron oxyhydroxide by the oxidation reaction. The particles are then filtered, washed, dried and reduced by heating, etc. and the ferromagnetic fine metallic particles are obtd. Since the fine metallic particles have excellent magnetic characteristics such as high coercive force, high magnetic flux density or the like, the particles contribute to an improvement in the performance of an audio cassette tape, etc. when used for the same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ferromagnetic metal fine particles, and more specifically, the present invention relates to a method for producing ferromagnetic metal fine particles, and more specifically, a method for producing ferromagnetic metal particles, and more specifically, a method for producing ferromagnetic metal particles, and more specifically, a method for producing ferromagnetic metal particles, and more specifically, a method for producing ferromagnetic metal fine particles, in which a salt of a metal different from iron (hereinafter referred to as "different metal"), etc. is added to an aqueous suspension of α-iron oxyhydroxide. The present invention relates to a method for producing fine particles of a ferromagnetic metal obtained by adding a-ferromagnetic metal, adhering a compound of a different metal to an a-iron oxyhydroxide trap, and then reducing the compound.

Ferromagnetic metallic iron particles with high coercive force and high magnetic flux density improve the performance of audio cassette tapes (Kombaku) VT
It has been attracting attention due to the development of the videotague for R. In order to improve the performance of these tapes, the magnetic powder is becoming finer.

However, as the magnetic powder becomes finer, the coercive force is higher, and the dispersibility, weather resistance, orientation, etc. of the magnetic powder tend to deteriorate. deterioration is more likely to occur. Therefore, there is a known method of adding different metal compounds to α-iron oxyhydroxide in order to improve the various properties of magnetic powder while taking into consideration the relationship between the magnetic powder and the magnetic head. .

Methods of adding a compound of a different metal include (1) adding a salt of a different metal together with ferrous hydroxide during the synthesis of α-iron oxyhydroxide to cause coprecipitation, or adding a salt of a different metal to the reaction solution. A method of dissolving and performing an oxidation reaction (hereinafter referred to as doping method).

), and υ (2) The produced a-iron oxyhydroxide powder or wet cake is suspended in water, made acidic or alkaline as necessary, and then an aqueous solution of a salt of a different metal is added, and as necessary. A method of depositing precipitation by neutralizing a suspension (
Hereinafter, this method will be referred to as the adhesion method. ) etc. are known. ,.

In the doping method, α-iron oxyhydroxide particles with greatly different particle shapes are produced depending on the type, amount, and method of addition of the metal compound added, and the characteristics of the metal fine particles obtained by reducing this also differ from those of different metal compounds. Compared to the case without adding , the difference in all characteristics is large. Further, depending on the amount of the additive, which varies depending on the type of the different metal compound added, branched particles may be formed or the sword-like shape of the α-iron oxyhydroxide particles may be lost. Although the doping method is also a promising method for improving the properties of metal fine particles, the deposition method is suitable for improving the desired properties.

The adhesion method is to suspend α-iron oxyhydroxide powder or wet cake in water and then add an aqueous solution of a different metal salt, etc.; add an acid or alkali to the aqueous suspension. Once α-iron oxyhydroxide is sufficiently dispersed between aggregates, an aqueous solution such as a salt of a different metal is added, and an alkali or acid is added to neutralize it, thereby depositing a different metal compound, and then filtering. There are methods etc. These methods have the disadvantage that the adhesion between α-iron oxyhydroxide and the metal compound is weak, and the particles tend to break down during the reduction process. In order to strengthen the adhesion between α-iron oxyhydroxide and the metal compound and reduce particle breakage during the reduction process, heat treatment is performed at 70°C or higher, preferably 90°C or higher after adding an aqueous solution of a different metal salt, etc. It is necessary to apply Although the heat treatment reduces particle breakage during the reduction process, deterioration of magnetic properties is observed due to the influence of coexisting anions.

Although the coexisting anions are removed to some extent by washing with water after heat treatment, less than several ten percent of the anions before washing remain in the a-iron oxyhydroxide, and the influence of anions cannot be completely removed. If water washing is performed without heat treatment, some of the metal compound intended for deposition will inevitably flow out. In addition, when deposited by these methods, Ni, Cot Ct, M
Only limited metals such as n+ Mg can be deposited.

In view of these shortcomings of conventional methods, the present inventors have developed a method for firmly adhering arbitrary amounts of most metals even at low temperatures, removing anions that cause deterioration of magnetic properties, and preventing particles from collapsing during the reduction process. The present invention was achieved as a result of intensive research to find a method for producing metal fine particles that are hardly recognized.

That is, the present invention provides an aqueous solution (including an acidic or alkaline aqueous solution) of a compound such as a salt, a metal acid salt, or an oxide of a different metal, and a ferrous iron aqueous suspension in an aqueous suspension of α-iron oxyhydroxide. The gist is a method for producing ferromagnetic metal fine particles by adding an aqueous salt solution to perform an oxidation reaction, washing with water, drying, and reducing.

The aqueous suspension of α-iron oxyhydroxide is obtained by suspending in water an α-iron oxyhydroxide synthesis reaction product slurry and a wet cake or dry powder of α-iron oxyhydroxide obtained therefrom. includes. This aqueous suspension may be acidic, alkaline or neutral. Therefore, unlike the conventional method, the present invention has the advantage that the slurry produced by the α-iron oxyhydroxide synthesis reaction can be used as is.

The aqueous solution of the compound such as the salt of a different metal to be added can be used as a neutral, acidic or alkaline aqueous solution. In this case, the choice between neutral, acidic, and alkaline depends on the solubility of the dissimilar metal salt, etc. in the aqueous solution, and the desired level when added to the aqueous suspension of a-iron oxyhydroxide. It is determined by taking into account whether or not adhesion occurs uniformly over the entire surface. These adrenal glands can be treated by dissolving acidic or JjM-based rostrum.

A45 The ratio of the compound such as the temperature of the different metal (M) to be added and the ferrous salt is "ferrous iron (Fe) / different metal (M)"
It is preferable that the atomic ratio (hereinafter referred to as atomic ratio) is 0.5 or more. If it is less than 0.5, the adhesion strength between the σ-iron oxyhydroxide and the chemical compound will not be strong enough, which is not preferable.

The upper limit of this ratio is not particularly limited, but if it is larger than 3, if the amount of the different metal added is 0.1 or more in terms of atomic and molecular ratio to α-iron oxyhydroxide, [ferrous iron] (F
If the atomic-molecular ratio (referred to as "number of atoms/number of molecules"; the same applies hereinafter) of e(II)/α-iron oxyhydroxide (F'e00H) is greater than 0.3, in this case, α - No good welfare [2] as agglomeration of iron oxyhydroxide particles becomes significant. Therefore, "ferrous iron (Fe)/different metal (M)" is particularly preferably 0.5 to B1. After adding the salt of the different metal, etc., an appropriate p
When adjusted to H, a part or most of the foreign metal becomes a compound such as hydroxide, its hydrate, or oxide together with ferrous ions, and precipitates on the periphery of α-iron oxyhydroxide or alone. Or gel. However, the precipitates at this stage either do not yet adhere to the α-iron oxyhydroxide, or even if they do, they do not adhere to the α-iron oxyhydroxide.
If the adhesion strength is low, the particles tend to collapse during the reduction process. Then, the oxidation reaction is performed. Through this oxidation reaction, the precipitated ferrous iron is oxidized and precipitated as α-iron oxyhydroxide on the surface of α-iron oxyhydroxide.
It is presumed that at that time, a different metal is injected into the material, and strong adhesion (adhesion) of the different metal to the α-iron oxyhydroxide is realized. Then, in the reduction process, the particles become less likely to collapse.

To specifically explain the present invention, (1) a wet cake or powder of α-iron oxyhydroxide is suspended in water. It is preferable to add an acid such as acetic acid to this aqueous suspension to adjust the pH to 4 or lower to sufficiently disperse α-iron oxyhydroxide. To this, g≦g of an aqueous solution (neutral or acidic aqueous solution) of a different metal salt, etc. is added, and then an aqueous ferrous salt solution is added. Add an aqueous solution of a basic substance such as NaOH, ammonia, Na2CO, etc. or ammonia gas, taking into account the amount of neutralization of the added acid (~chemical equivalent or more for the ferrous salt and the salt of a different metal). Expressed in the formula, “(added iQ group negative)≧
(8 Neutralization amount) + (Additional ferrous salt amount) + (Additional metal salt amount)
”). Subsequently, an oxidation reaction is performed by blowing in an oxygen-containing gas such as air or adding a li&oxidation agent.

After the oxidation is completed, it is washed with water, dried, and heated to reduce to produce metal fine particles.

As an alternative method, (2) add an aqueous solution of a salt of a different metal (which may contain an acid or a base) to the α-iron hydroxide synthesis reaction slurry, and at the same time, before or after adding ferrous Add salt solution. Here, it is preferable that the elephant acceleration of the aqueous solution of the gold fiA salt and the like and the aqueous ferrous salt solution be as small as possible. The above-mentioned metal salts and ferrous salts can be used in combination without precipitation, even if 'I+;A is added as a mixed solution. It is also possible to produce fine metal particles with almost the same powder magnetic property. However, in these cases, fine grains tend to form, so it is preferable to add an aqueous solution of a metal salt or the like and then add an aqueous solution of ferrous rings. After addition of the ferrous salt aqueous solution, an oxygen-containing gas such as chlorine gas is blown into the aqueous solution and a β-forming agent is added to carry out the β-forming reaction. After the oxidation is completed, the product is dried using an r-hydrogen method and reduced by heating to produce metal fine particles. Can this method (2) also be applied to the above moisture? 1
When deposited from an aqueous suspension such as '1'5 cake, fine metal particles having magnetic properties similar to those in (1) can be obtained.

According to the method of the present invention, any one or a combination of two or more of salts of most metals such as J+T of metals other than alkali metals that are soluble in water or an aqueous solution of an acid or base can be used. It can be deposited on α-iron oxyhydroxide at a certain value. The bond between the deposited metal compound (this compound is often different from the compound such as metal salt at the time of addition) and σ-iron oxyhydroxide is strong, and it can be easily removed by washing with water. No outflow was observed, and the anion which has a weak adhesion to α-iron oxyhydroxide and causes deterioration of its magnetic properties was selectively removed. β3 is recognized, and compared to the conventional 112-point method, there is a significant difference in both papers t ().

In the σ-iron oxyhydroxide synthesized by the conventional method, microparticles that deviate greatly from the average iron oxide size, which is the cause of the transfer characteristics, the spread of the I(c distribution, and the deterioration of the NIJ and SFD) are observed. According to the method of the present invention, the microparticles disappear by combining with larger particles, and the total 1,1 compound l(/J) coated a-oxywater 1′1 after the jl·2 reaction The particle size of the iron ceride particles is very large. Even through the Y-element reaction, the fine particles bonded to each other do not separate from the larger particles and change the particle shape of the α-iron oxyhydroxide after deposition. Well-held metal particles are swallowed.

Hereinafter, the present invention will be explained with reference to actual examples, but it goes without saying that the present invention is not limited to these examples. .

Example 1 12.6 g of 6 mat/l NaOH aqueous solution was added with 0.0.
34rnot/ l F'eSO4 water 1=rtasxi
Added and kept at 40°C with air flow t201/min to α
- 2,500 g of wet cake obtained by synthesizing iron oxyhydroxide 7 and washing with water (α-iron oxyhydroxide dry)
10.001 and 241 of water were added, and after stirring for 1 hour, acetic acid was added to a PL of 8.5, and the mixture was stirred for 30 minutes. , 0.5 mat/II NiSO4 water bath solution 1
After adding 112 liters of water bath solution and stirring for 15 minutes, 5 moA
7' INaOH water bath solution 1400 * l' (H) was added. After a 30-minute pause, air was completely blown in at a flow rate of 1/min, and the temperature was kept at 25°C and oxidation reaction was carried out for 5 hours. Reaction completed. After washing with water and drying, it was heated and retained in the ferromagnetic metal granulated iron, and no Ni was detected in the J solution and the washing solution. The obtained Ni coating %i (1-iron oxyhydroxide contains the α-oxyhydroxide fi (microparticles existing in the iron oxide) before adhesion. was not observed, and the particle size was <4Ii11.Reduction was performed using Ni-coated iron oxyhydroxide (500 g).
The reaction was carried out for 5 hours at a hydrogen flow rate of 201/min and a reduction temperature of 500°C to obtain ferromagnetic goldfish fine particles that well maintained the particle shape of Ni-coated iron oxyhydroxide. This magnetic powder magnetic cow tea ll7J:Hc: 1 5880
e. as: 1 59 emu/f,
ar/as': 0. 5 8 The characteristic value of an oriented sheet using this magnetic powder is Hc: 14680e.

Br: 2 9 8 4 gauss, Br/B
m: 0. 8 4 6 + SF■): 0.4
;32, and the He content was about 1000e higher than that of the metal fine particles obtained by the method of the comparative example described later, and the SFD was improved.

Examples 2 to 10 Magnetic powders were produced according to Example 1, except that the type and amount of the salt of the added different metal and the atomic ratio of the different metal and ferrous iron were changed. Similar to Example 1, the additive metal content is approximately 100%a00%
It is retained in Meoxy, and almost no anions and Na+ are observed. Strong (j4j metal fine particles) which well maintained the particle shape of J a-iron oxyhydroxide were obtained.

The characteristic values of the obtained fine particles are shown below along with the manufacturing conditions, etc.

Example 11 To α-iron oxyhydroxide reaction slurry synthesized in the same manner as in Example 1, 0. 5 mot/R NiSO4 water soluble) Night 1
290*l was suspended at a speed of 20 ml/min), followed by 0. 5 mat/e Fe5O6 aqueous solution was added at a flow rate of 1290 ml<20 11 t/min. After addition, stir for 30 minutes and reduce to 0. 2 l/
The oxidation reaction was carried out for 6 hours through air at a flow rate of min. to obtain the same Ni-coated iron oxyhydroxide as in Example 1. Reduction was carried out in the same manner as in Example 1, and the ferromagnetic metal fine particles with the particle shape of Ni-coated iron oxyhydroxide well maintained were reduced to one digit.

The special values of ``1.'' are shown below along with the manufacturing conditions, etc.

Ability f'i j9su J2~1 fir5i force [15°4f・II/tsugen 1. ') The procedure was carried out in the same manner as in Example 1, except that a reduction temperature was added at the end of the first step, after the end of the shell, and at the end of the first turn. Real 1・i! A metal σ-iron oxyhydroxide similar to that in Example 1 was produced, and ferromagnetic gold A, ij (4 particles were toughened) which retained its particle shape well.

After checking the characteristic values and manufacturing conditions of the fine particles, etc.
2 and shown in ψ.

I Report 2 pH Practice 13 II 1 and turn σ-oxy water t;・N iron chloride wet 7
Leap cake 1250F/(dry iii 500 g) 1
24 degrees of water, after stirring for 1 hour 1:4 f, i'p r
; i2 k added pi a, 5 tol, 30 minutes)",
; Stir (~.0.5 mat / (l NiSO4
Add 562 yrti fA% aqueous solution and stir for 30 minutes, then add 28'y'6 ammonia water 1rN to pl-1! l
, 5, the temperature was raised to 90''C for 30 minutes, the temperature was raised to 90''C, the mixture was aged for 1 hour, and the mixture was dried under the same conditions as in Example 1.

0.32% SO was added to the Ni gradual loss of a-oxyhydroxide.
4”- is present, and particle collapse due to reduction is observed,
The magnetic properties of magnetic powder (c: 14650e; as21
55 e+nu/7 i ar/rys: 0.51, and the SFD of the oriented sheet is 0.612.
``Her appearance has changed significantly compared to ``h Will.''

Comparative Example 2 Ni was coated in the same manner as in Comparative Example 1, washed with water from r-through-hole 601, dried, and reduced under the same conditions as in Example 1.

Even though it was washed with water after being subjected to IF, 0.16% of SO4''- was present in α-iron oxyhydroxide, and the particles were observed to be broken due to oxidation. It became.

The characteristics of the absorbed fine particles and the manufacturing process are shown below.

Hichu father ten chestnuts 3 additives sej! The same procedure as Comparative Example I was carried out except that A4(SO<)q was used as the gold salt.

A/- flows out during ρj filtration and water washing, and α-oxy water 1
TF to cast iron, 1. Only about 30% of the added amount is retained,
SO42- was also translocated by 0.30%.

The characteristic values of the obtained fine particles, the manufacturing conditions, etc. are shown in the section below.

Claims (5)

[Claims] (1) An aqueous solution kl of a compound of a metal different from iron (hereinafter referred to as "different metal") in an aqueous suspension of iron oxyhydroxide
In the method of producing ferromagnetic metal fine particles by adding F5 to the α-iron oxyhydroxide particles, depositing a compound of a different metal on the α-iron oxyhydroxide particles, and then reducing the mixture, By adding ferrous salt together with a metal compound and performing an oxidation reaction, we decided to break the bond! +'f characteristic. (2) The method described above, wherein the aqueous suspension of iron oxyhydroxide is a slurry produced by an α-iron oxyhydroxide synthesis reaction. (3) The aqueous suspension of α-iron oxyhydroxide is a wet cake or dry powder of α-iron oxyhydroxide obtained by dehydrating the slurry produced by the α-iron oxyhydroxide synthesis reaction. The method as described above. (4) The ratio of the amount of the compound of the different metal (M) added to that of the ferrous salt is such that the atomic ratio of r F'e (1)/M J is 0.5 or more, preferably 0.5. 3. The method according to item (1), characterized in that: -3. (5) The amount of the ferrous salt added to the α-iron oxyhydroxide is calculated as r Fe (It)/ a -Fe OOHJ
The atomic-molecular ratio of (
The method described in paragraph 1) or paragraph (4).