JPS60195023A - Preparation of needle-like goethite - Google Patents

Abstract

PURPOSE:To prepare needle-like goethite fittest as fine magnetic powder for magnetic tape, having sharp particle size distribution, by adding Sr<2+> to a reaction system, neutralizing a ferrous salt with an alkali, oxidizing prepared Fe(OH)2 with air. CONSTITUTION:In preparation of needle-like goethite by neutralizing a ferrous salt (e.g., FeCl2, FeSO4, etc.) with an alkali of give Fe(OH)2, oxidizing it with air, 0.2-20wt% Sr<2+> is added to the reaction system. Needle-like goethite fittest as the fine magnetic powder for magnetic tape, having sharp particle size distribution, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides magnetic powder for magnetic tape (for example, r-Fe20
The present invention relates to a method for producing acicular goethite, which is a raw material for co-Fe'203 and metal magnetic powder.

In recent years, magnetic powder for magnetic tapes is required to be fine particles in order to increase the density of magnetic recording media and improve the S/N ratio. Especially V
T RJn magnetic powder has better dispersibility and more fine particle powder. Although various studies have been made to create a game site that meets the following objectives, the current situation is that it has not yet been completed.

The traditional manufacturing method for gamesite is Daiichi Tetsu i! ! (
For example, ferrous chloride, ferrous sulfate, etc.) in an alkaline solution (
For example, a method of air oxidizing ferrous hydroxide obtained by adding sodium hydroxide, ammonium hydroxide, etc. is known. In addition, the magnetic powder obtained by using goethite as a starting material and reducing it in a gas phase in a reducing atmosphere depends largely on the particle shape of the starting material, goethite, so the shape of the raw goethite is extremely important. It is. The planned goethite produced by the conventional method (1) is synthesized under synthetic conditions (for example, F
It is extremely difficult to obtain goethite with a uniform particle shape with good reproducibility, as it is greatly influenced by factors such as e2+ concentration, alkali content, and oxidation rate.

According to the present invention, by simply adjusting the amount of Sr2+ ions added, not only can the shape of the particles be arbitrarily controlled, but also it is possible to flexibly produce goethite particles with no branching and an extremely sharp particle size distribution. .

The production of goethite is so-called crystal growth, and it becomes acicular crystals through a series of processes of nucleation and growth. Generally, during crystal growth, impurities present in the system induce nucleation. In the present invention, metal ions are used as nucleation inducers, and the growth can also be controlled by attaching the metal ions to the surface of goethite particles. As a result of testing various metals, it was found that strontium ion (Sr2+) is the most effective.

That is, in the present invention, when producing sword-shaped goethite obtained by air oxidizing ferrous hydroxide, which is obtained by neutralizing a ferrous salt with an alkali, strontium ions (Sr2+) are added to the reaction system. 0.2-20 fold IH.

The present invention provides a method for producing goethite, which is most suitable as a magnetic powder for magnetic tapes, and is characterized by adding %.

The method for manufacturing goethite according to the present invention will be explained in detail as follows.

When mixing ferrous iron salt and an alkaline solution to produce ferrous hydroxide, Sr2+ ions are added in advance. Add it to the solution or add it for 5 hours after ferrous hydroxide is formed.
2 (Ions may be added. After heating a suspension of ferrous hydroxide containing Sr2+ ions to 40 to 50°C, goethite with a uniform shape is obtained by introducing air. As a ferrous salt, 41H ferrous (Fe(,1
2) Ferrous sulfate (Feso4), ferrous nitrate (Fe,
(NO3)' 2 ) and other water-soluble ferrous salts. In addition, as an alkaline component, sodium hydroxide (N
aOH), potassium hydroxide (KOH), ammonium hydroxide (NH40H), etc. can be used, and thorium hydroxide is particularly suitable. In addition, Sr2+ ions include strontium chloride (Src12), strontium sulfate (SrsO4), and strontium nitrate (Sr2+).
Water-soluble strontium fields such as r(NC)s)2) may be used, among others j1! Strontium chloride is preferred.

The Sr2+ ions in the present invention are considered to have the following functions. Sr2+ ions are present in the ferrous hydroxide floc and are thought to serve as the nucleus for the production of goethite when air is introduced. In addition, the Sr2+ ions present in the system suppress excessive crystal growth of goethite particles by adhering to particles in the growing process, and provide a uniform particle size distribution.

In the present invention, the magnetic force l-1 of Sr2+ ions is 0.2 to 20 times j, with respect to the generated goethite particles thousand stars,
in the range of 1%, preferably 0.5 to l 5 @
-7-IH%. When the amount of Sr9+ ions added is 0.
When 2% by weight is ungrooved, there is no effect of adding Sr2+ ions,
20 nails! -% or more, the acicularity of Gesai I/particles (
This is because the long axis/ltf axis ratio) becomes too small and the adverse effect of lowering the saturation magnetization becomes large. It has been confirmed by electron W3 microscopy and specific surface area that the goethite prepared by the present invention is fine and has a sharp particle size distribution, and it is explained by examples that it is an excellent magnetic recording material. do.

Next, the present invention will be specifically explained using examples.

[Example 1] 0.813 g of strontium chloride (SrC
fL2 ・6H20) dissolved in 0,4+wol/!
;L ferrous chloride (FeC12) solution 1-51 and 168
Ferrous hydroxide was obtained by mixing 1.5 g of an alkaline solution in which g of sodium hydroxide (NaOH) was dissolved, stirred in a nitrogen gas atmosphere for 2 hours, heated to 40°C, and then mixed with 1.5 g of an alkaline solution containing 5 g of sodium hydroxide (NaOH). Win air was introduced to obtain quaternary goethite.

[Example 2] Addition amount of Si-rontium JiA was 1.62Ei g
Goethite was obtained under the same conditions as in Example 1 except for the following.

[Example 3] Goethite was obtained under the same conditions as in Example 1 except that the amount of strontium chloride added was 2.439 g.

[Example 4] Goethite was obtained under the same conditions as in Example 1, except that the amount of strontium chloride added was 5.890 g.

[Example 5] Goethite was obtained under the same conditions as in Example 1, except that the amount of strontium chloride added was 13.813 g.

[Example 6] Goethite was obtained under the same conditions as in Example 1, except that the amount of strontium jIA chloride was changed to 25.188 g.

[Ratio-bite example] Goethite was obtained under the same conditions as in Example 1 except that strontium chloride was not added.

50% of the goethite obtained in the above-mentioned Examples and Comparative Examples
Dehydration for 3 hours at 0°C J, II! Table 1 shows the magnetic properties of the metal magnetic powder obtained by subjecting it to a mass treatment in H2 gas at 425°C for 6 hours.

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s''↑゛Chaos!rContinuation-?rOrthograph (Method) June 1981 281 1, Display of IG Patent Application No. 48822 of 19822, Title of Invention 4 Method for producing gamesite 3 , Relationship with the case of the person making the amendment Patent applicant address 1-1-28 Kitahonmachi-dori, Chuo-ku, Kobe, Hyogo Prefecture
1 Name (125) Kawasaki Steel Corporation 4, Agent 101 Telephone 864-4498 Address
Chiyo I, Tokyo: IJ-ku Iwamotocho 3-rl, 12W2 No. 5,
The date of the amendment order is June 26, 1980, 6, and the IgJ specification subject to amendment, ``Brief explanation of the drawings'', No. 7, and the detailed statement of contents of the amendment, No. 9, are amended as shown in the attached sheet.

[Brief explanation of the drawing]

1. Figures 1 and 2 are photographs substituted for drawings showing the crystal structure. Figure 1 shows the 30.00% of goethite obtained in Example 2.
0x, electron micrograph, Figure 2 is a comparative example of 30,000
The double electron W4 micrograph, FIG. 3, is a graph showing the relationship between Sr2+ ion charge and particle size. Patent applicant Kawasaki Steel Co., Ltd. Representative Patent attorney Minoru Watanabe

Claims (1)

[Claims] When producing acicular goethite obtained by air oxidizing ferrous hydroxide obtained by neutralizing ferrous salt with alkali, 0.2. A method for producing sword-shaped goethite, characterized by adding ~20% by weight.