JPS6161404A - Manufacture of magnetic metal powder - Google Patents

Abstract

PURPOSE:To prevent generation of a sintering when a reducing process is performed as well as to obtain the magnetic metal powder maintaining the needle-like property of Geothite by a method wherein the Geothite is reduced after a surface treatment is performed thereon using silane coupling agent and carboxylic acid or metal carboxylate. CONSTITUTION:A surface treatment is performed in advance on Geothite, which is used as the material for the title magnetic powder, using a silane coupling agent and carboxylic acid, or the silane coupling agent and metal carboxylate, the above-mentioned material is rinsed and dried by performing an ordinary method. After it is dehydrated by heating, magnetic metal powder is manufactured by performing a hydrogen reducing treatment in hydrogen current at the temperature range of 200-500 deg.C or thereabout. As a result, the distance between Geothite grains is increased, and the carbon generated by the decomposition of carboxylic acid is left even when the reducing process is performed, thereby enabling to prevent the generation of sintering between said Geothite grains.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing metal magnetic powder mainly made of metal such as Fe or an alloy thereof.

[Conventional technology]

Conventionally, magnetic recording media such as magnetic tapes and magnetic disks have been produced using magnetic coatings manufactured by J4, which are made by mixing and dispersing magnetic powder, which is a fine powder of ferromagnetic material, resin binders, organic solvents, various additives, etc. Coating type magnetic recording media in which a magnetic layer is formed by coating are often used. In this type of r magnetic recording medium, in order to correspond to 1゛, S density recording and to achieve high performance, powder of ferromagnetic total bending material such as Fe or its alloy with large coercive force Hc or its alloy is used. is now used as magnetic powder.

By the way, metal magnetic powder mainly composed of Fe is generally
Goethite (α-FeOOH
) as a starting material and hydrogen reduction at 200 to 400°C, and it is known that the acicularity of the resulting metal magnetic powder greatly depends on the acicularity of the goethite. .

However, when the above goethite is simply exposed to 2 m of water at high temperature, these goethite particles undergo sintering (sintering).
It is difficult to produce metal magnetic powder while maintaining the acicular nature of goethite.

Conventionally, attempts have been made to prevent the sintering by pre-surface-treating the goethite with wood glass or a silane coupling agent, but it is difficult to adhere uniformly to the goethite with the water glass. In addition, although the acicularity of the goethite is maintained to some extent by the silane camping agent, it is difficult to say that the effect is sufficient, and it has been confirmed that sintering occurs particularly in adjacent particles [...]. Therefore, in the obtained metal magnetic powder, the shape anisotropy of the acicularity is significantly attenuated, causing deterioration of magnetic properties such as coercive force.

[Problem that the invention seeks to solve]

As described above, when attempting to produce metal magnetic powder using goethite as a hydrogen compound, sintering between goethite particles poses a major obstacle.

Therefore, the present invention makes it possible to prevent sintering of goethite particles during the above-mentioned reduction process and to produce metal magnetic powder while maintaining the shape of the goethite particles.
Therefore, it is possible to create metal magnetic powder with excellent magnetic properties! ! The purpose is to provide a way to send money.

[Means for Solving the Problem] As a result of intensive research to achieve the above-mentioned object, the present inventors discovered that carboxylic acid or carboxylic acid metal salt is effective in preventing the above-mentioned sintering, and published this book. This invention has been completed and is characterized by reducing goethite surface-treated with a silane coupling agent and a carboxylic acid or a silane coupling agent and a carboxylic acid metal salt.

That is, in the present invention, goethite, which is a raw material, is surface-treated in advance with a silane coupling agent and a carboxylic acid, or a silane coupling agent and a carboxylic acid metal salt, and then this is treated by the usual method 1, such as washing with water and drying.
After heating and dehydration, a metal magnetic powder is produced by hydrogen reduction treatment at a temperature of about 200 to 500° C. in a hydrogen stream.

A characteristic feature of the present invention is that a silane coupling agent and a carboxylic acid or carboxylic acid metal salt are used together as a surface treatment agent for goethite, which increases the distance between goethite particles and further reduces the reduction process. Also, by leaving behind the carbon produced by the decomposition of carboxylic acid, sintering between these goethite particles is prevented.

Examples of the carboxylic acids used in the present invention include saturated fatty acids having 3 or more carbon atoms, unsaturated fatty acids, oxycarphonic acids, etc., such as oleic acid, elaidic acid, linoleic acid, linoleic acid, lactic acid, apple alcoholic acid, tartaric acid, and citric acid. Examples include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, and stearic acid. Also,
As the carboxylic acid metal salt, the above-mentioned alkali metal salts of carboxylic acids, alkaline earth metal salts, etc. can be used.

The amount of the carboxylic acid or carboxylic acid metal salt to be added is 5 to 3 parts per 100rrXffi parts.
Preferably, it is 0 parts by weight.

On the other hand, as the above-mentioned silane coupling agent, the general formula % formula % [wherein Rr to R1 are H, CnH2n+l, C
nH,,SHI C,LH(1n+1)-,,IF+
n+ CnH+zn*+)-m' i, an atom or atomic group (R+-R may be the same or different), n is an integer of 1 to 20, m is 1 to (2n+
1) The integers, X, -X, are CM, I, -0-C.

H2, i, , -0-COCH, Ka9 selection hare 6 j
The g symbol represents an atomic group (X and -X3 may be the same or different), and i represents an integer from 1 to 6, respectively. ], specifically, dodecyltrichlorosilane, butyltrimethoxysilane, methyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,
Examples include methyl-3,3,3-)lifluoropropyldichlorosilane and 3.3.3-trifluoropropyltrimethoxysilane.

The amount of the silane coupling agent added is the Goethite 100! I! It is preferable that the amount is in the range of 10 to 50 parts by weight.

The silane coupling agent and the carboxylic acid (or carboxylic acid metal salt) may be added simultaneously or the silane coupling agent may be added first, but it is particularly preferable that the silane coupling agent be added first.

[Effect]

As mentioned above, by pre-surface-treating the raw material goethite with a silane cuff pulling agent and carboxylic acid or its metal salt, relatively long molecules of carboxylic acid adhere to the goethite surface, and therefore these goethite The spacing between the site particles increases, and carbon generated by the decomposition of the carboxylic acid or carboxylic acid metal salt molecules during the reduction process, etc., remains, resulting in sintering between goethites, that is, sintering of the metal magnetic powder. is prevented.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
It goes without saying that the present invention is not limited to these examples.

Example 1゜Long sleeve 0.25 tile acicular goethite (α-FeOOH) 1
Parts of 00i were dispersed using 2000 parts by weight of water.

Next, 30 parts by weight of a silane coupling agent and 5 gL part of sodium oleate were sequentially added to this dispersion.

The solution was stirred for 2 hours, then filtered, dried, and
Roasted in an atmosphere for 2 hours.

Further, the mixture was reduced in a H2 stream for 4 hours to obtain metal magnetic powder.

According to the above method, Samples 1 to 4 were obtained by changing the roasting temperature and reduction temperature.

For each sample obtained, magnetic properties (coercive force Hc,
Saturation magnetization σ6, squareness ratio Rs) and specific surface fis,s.

At-investigated. The results are shown in Table 1.

Table 1 Example 2 Samples 5 to 9 were obtained in the same manner as in Example 1 except that the amount of sodium oleate added was 10 parts by weight. The magnetic properties and specific surface area of each of these samples were also investigated. The results are shown in Table 2.

Table 2 Comparative Example Long Sleeve 0.25 River Acicular Goethite (α-FeOOH) 1
00 parts by weight were dispersed using 2000 parts by weight of water.

Next, 30 parts by weight of a silane coupling agent was added to this dispersion.

The solution was stirred for 2 hours, then filtered, dried, and
It was roasted in an atmosphere for 2 hours.

Furthermore, reduction was carried out for 4 hours in an H7 stream to obtain metal magnetic powder.

Samples 10 to 14 were obtained according to the above method by varying the roasting temperature and brewing temperature.

For each sample obtained, magnetic properties (coercive force Ha,
Saturation magnetization - monogonal ratio Rs) and specific surface area S, S.

I looked up eight. The results are shown in Table 3.

Table 3 A comparison of these tables shows that metal magnetic powder with a large specific surface area can be obtained by surface treating acicular goethite with a silane coupling agent and sodium oleate. It is also found that its magnetic properties are excellent, particularly in terms of coercive force and squareness ratio.

In order to make the above tendency clearer, FIG. 1 shows the relationship between the amount of sodium oleate added and the specific surface area. However, the reduction temperature is 380'C.

Furthermore, Figure 2 shows the relationship between reduction temperature and specific surface area for the cases where sodium oleate is not added, when 5 parts by weight of sodium oleate is added, and when 3 parts of sodium oleate is added. .

From these FIGS. 1 and 2, it can be seen that the specific surface area increases with the addition of sodium oleate regardless of changes in the reduction temperature.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, the starting material, goethite, is surface-treated in advance with a silane coupling agent and carboxylic acid (or carboxylic acid metal salt), and then reduced. The spacing between goethite particles becomes larger, and carbon produced by the decomposition of its molecules during the reduction process remains between the particles.
Sintering during the reduction process is prevented, and a metal magnetic powder that maintains the acicular nature of goethite can be obtained. Therefore, a metal magnetic powder having excellent magnetic properties such as coercive force can be obtained.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the amount of sodium oleate added and the specific surface area at a reduction temperature of 380'O, and Figure 2 shows the relationship between the amount of sodium oleate added and the specific surface area when 5 parts by weight of sodium oleate was added. FIG. 4 is a characteristic diagram showing the relationship between the binary temperature and the specific surface area for the case where 1 Oi of sodium oleate is added and the case where 1 part of 1Oi of sodium oleate is added.

Claims (1)

[Claims] A method for producing metal magnetic powder, comprising reducing goethite surface-treated with a silane coupling agent and a carboxylic acid or a silane coupling agent and a carboxylic acid metal salt.