JPS6217363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing magnetic powder for magnetic recording media, which is composed of powder containing Fe as a main component.

Magnetic powder made of Fe powder has better magnetic properties than the currently used γ-Fe ₂ O ₃ type magnetic powder, and its practical use is expected, but it has the drawback of being susceptible to rust. In order to overcome the drawbacks of the prior art, an Fe-based powder is desired that maintains excellent magnetic properties and also has excellent corrosion resistance. An example of Fe-based powder is JP-A-53-84864, for example.

An object of the present invention is to solve the above-mentioned problems and provide a method for producing magnetic powder for magnetic recording media, which is made of Fe-based powder and has excellent corrosion resistance.

The production method of the present invention includes (i) one of Cu salt and Ni salt;
(ii) obtaining a suspension of ferrous hydroxide containing one or more of Cu and Ni by reacting an aqueous solution of divalent Fe salt containing at least one type of Fe salt with an aqueous solution of an alkali metal hydroxide; (iii) producing goethite powder by blowing oxygen-containing gas into the suspension; and (iii) reducing the goethite powder by a hydrogen reduction method to produce Cu, Ni.
The method includes a step of preparing an Fe alloy powder containing one or more of the above.

Further, a step may be inserted between the above steps (iii) and (iii) to dehydrate the goethite powder to obtain α-Fe ₂ O ₃ powder containing one or more of Cu and Ni. , even better results are obtained.

Furthermore, the obtained product after completing the above step (iii)
Fe alloy powder containing one or more of Cu and Ni is subjected to chromate treatment, alkaline treatment with NH ₄ OH, etc., or acid treatment with phosphoric acid etc., or the above alloy powder is brought into contact with metal powder that tends to be highly ionized. By doing so, corrosion resistance can be further improved.

The concentration of the divalent Fe salt aqueous solution in step (i) is 0.2
Good results can be obtained by setting the concentration of the alkali metal hydroxide aqueous solution to 1 to 10 mol/.

The corrosion resistance of the Fe alloy powder containing one or more of Cu and Ni produced by the production method of the present invention was compared to that produced by the conventionally known liquid phase reduction method.
It has better corrosion resistance and higher saturation magnetization than similar Fe alloy powders.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 1 mol of FeSO ₄ and 0.01 mol of CuSO ₄ were dissolved in 1 mol of water, and this was further dissolved in 10 mg of Fe powder and 6N.
A solution containing 20 ml of H ₂ SO ₄ is mixed with an aqueous solution of 11 moles of NaOH dissolved in 3.6 ml of oxygen-free water, and air is blown into the mixture at a flow rate of 0.2/min for 72 hours. The obtained yellow crystal α-FeOOH is thoroughly washed with water, the pH is adjusted to 8 or less, and then suction filtered and dried.

Next, 10 g of the yellow crystal α-FeOOH was added at a flow rate of 4
After dehydration at 400℃ for 2 hours in a _N2 flow at a flow rate of 10/min, dehydration was performed at 30℃ for 20 hours in a _H2 flow at a flow rate of 10/min.
Fe powder containing 1 at% Cu was prepared by hydrogen reduction for hours. The Fe(Cu) powder was immersed in the ethyl alcohol solution of 1, and air was blown into the toluene solution at a flow rate of 3/min for 3 hours.

This Fe (Cu) powder is heated at a temperature of 60℃ and a relative humidity of 90%.
When the powder was left in an atmosphere of 7 days, the saturation magnetization of the Fe(Cu) powder decreased by 7%.

Example 2 Instead of 0.01 mol of CuSO ₄ in Example 1
Fe was prepared in the same manner as in Example 1 using 0.02 mol of NiSO ₄ .
(Ni) powder was produced. This Fe(Ni) powder is heated to
When left in an atmosphere of 60°C and 90% relative humidity for 7 days, the saturation magnetization of the Fe(Ni) powder decreased by 9%.

Comparative Example 1 Instead of 0.01 mol of CuSO ₄ in Example 1
Fe was prepared using 0.01 mol of CoSO ₄ in the same manner as in Example 1.
(Co) powder was produced. When this Fe(Co) powder was left in an atmosphere with a temperature of 60°C and a relative humidity of 90% for 7 days, the saturation magnetization of the Fe(Co) powder decreased by 20%.

Example 3 Instead of 0.01 mol of CuSO ₄ in Example 1
Fe (Cu, Ni) powder was prepared in the same manner as in Example 1 by adding 0.01 mol of CuSO ₄ and 0.01 mol of NiSO ₄ at the same time. When this Fe (Cu, Ni) powder was left in an atmosphere with a temperature of 60℃ and a relative humidity of 90% for 7 days, Fe
The saturation magnetization of (Cu, Ni) powder decreased by 2%.

Comparative Example 2 Fe powder produced under the same conditions as Example 1 except that 0.01 mol of CuSO ₄ was not added was heated to a temperature of 60°C.
When it was left in an atmosphere at ℃ and 90% relative humidity for 7 days, the saturation magnetization of the Fe powder decreased by 40%.

As stated above, when compared with the comparative example,
The decrease in saturation magnetization of Fe alloy powders in Examples 1 to 3 was 20
% or more less. In other words, the corrosion resistance of Fe alloy powder containing one or more of Cu and Ni is higher than that of Fe alloy powder without additives.
Better corrosion resistance than powder.

In addition, the amount of Cu added is 0.1at% or more and 8at% or less,
The amount of Ni is preferably 0.5 at% or more and 10 at% or less.

If the amount added is less than these lower limits,
Almost no improvement in corrosion resistance is observed, and if it is larger than the upper limit, the saturation magnetization or coercive force becomes too small and the advantages of Fe magnetic powder are lost.

According to the present invention, a magnetic powder for magnetic recording media with excellent corrosion resistance can be obtained.

Claims (1)

[Claims] 1. Containing one or more of Cu salt and Ni salt. 2.
A ferrous hydroxide suspension containing one or more of Cu and Ni is obtained by reacting a valent Fe salt aqueous solution with an alkali metal hydroxide aqueous solution, and bringing an oxygen-containing gas into contact with the suspension. A method for producing magnetic powder for a magnetic recording medium, comprising reducing goethite powder obtained by oxidation by a hydrogen reduction method to obtain Fe alloy powder containing one or more of Cu and Ni. 2 Containing one or more of Cu salt and Ni salt 2
A ferrous hydroxide suspension containing one or more of Cu and Ni is obtained by reacting a valent Fe salt aqueous solution with an alkali metal hydroxide aqueous solution, and bringing an oxygen-containing gas into contact with the suspension. The goethite powder obtained by oxidation is dehydrated to obtain α-Fe ₂ O ₃ powder containing one or more _of Cu and Ni _.
A method for producing magnetic powder for magnetic recording media, which comprises reducing powder by a hydrogen reduction method to obtain Fe alloy powder containing one or more of Cu and Ni.