JPS5864223A - Treatment of magnetic iron oxide - Google Patents

Abstract

PURPOSE:To increase the coercive force of magnetic iron oxide by dispersing the iron oxide in an aqueous medium, removing water soluble substances contained in the iron oxide with an ion exchange resin, and depositing a Co-base metallic compound on the surface of the iron oxide. CONSTITUTION:Magnetic iron oxide such as gamma-Fe2O3 is dispersed in an aqueous medium such as water or acohol to prepare a slurry, and by adding an ion exchange resin to the slurry, water-soluble substances contained in the iron oxide are removed. As the ion exchange resin a cation exchange resin or an anion exchange resin is used, and the amount of the resin is about 0.5-100 times the theoretical amount required to exchange ions produced from the water soluble substances. A Co-base metallic compound is then deposited on the surface of the magnetic iron oxide. Metals to be deposited includes Co, Fe, Mn, Zn, Ni, Cr, Pb and Sn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating the surface of magnetic iron oxide prior to depositing a metal compound containing cobalt as a main component on the surface of the magnetic iron oxide.

In recent years, there has been a demand for higher performance in magnetic recording media, and along with this, magnetic iron oxides with high coercive force and magnetic iron oxides with high filling properties are required as magnetic materials. As magnetic recording media, household video tapes and high-performance audio tapes are becoming increasingly popular, but acicular magnetic iron oxide alone can no longer be used as the magnetic material used in these fields, and cobalt-containing magnetic iron oxide is now being used. There is. Various improved methods have been proposed for the production of cobalt-containing magnetic iron oxide in order to improve the performance of magnetic recording media 1-.
There have been few attempts to pre-treat the surface of magnetic iron oxide to make it more effective for adhesion of metal compounds mainly composed of cobalt. A method in which a silica film is applied to the surface of magnetic iron oxide as a barrier to prevent the deposited cobalt atoms from dispersing into the core (Japanese Patent Application Laid-Open No. 56/26729). A method of uniformly dissolving cobalt inside particles of ferromagnetic iron oxide by dispersing ferromagnetic iron oxide in a solution consisting of a cobalt salt soluble in this organic solvent and subjecting it to wet heat treatment (Japanese Unexamined Patent Publication No. 54 -85
198, Japanese Unexamined Patent Publication No. 54-84298).

As a result of various studies on how to treat acicular magnetic iron oxide, which is the core when depositing a cobalt compound, the present inventors found that
An ion exchange resin is added to a slurry in which magnetic iron oxide is dispersed in an aqueous medium to remove water-soluble substances contained in the magnetic iron oxide, and then cobalt as a main component is added to the surface of the magnetic iron oxide. The present invention was completed based on the discovery that a magnetic iron oxide having excellent magnetic properties, especially a high coercive force, can be obtained by depositing a metal compound having the following properties. .

That is, in the present invention, an ion exchange resin is present in a slurry in which magnetic iron oxide is dispersed in an aqueous medium to remove water-soluble substances contained in the magnetic iron oxide, and then the magnetic iron oxide is dispersed. This is a method for treating magnetic iron oxide, which is characterized by depositing a metal compound containing cobalt as a main component on the surface.

The magnetic iron oxide treated in the present invention includes γ-F C20
-, magnetite, γ-Fe20. Examples include bertolide compounds, which are Φ-containing oxides of magnetite and magnetite, and 7-elite.

As the aqueous medium, water or an aqueous solution of a water-soluble organic substance such as furfur or 7setone is used.

Ion exchange resins used in the present invention include cation exchange resins and anion exchange resins. Cation exchange I!
Regardless of whether the fat or the anion exchange resin is present in the slurry, or both, there is an effect of promoting the removal of water-soluble substances contained in the magnetic powder. The amount of ion exchange resin present in the slurry is preferably 0.5 to 100 times the theoretical amount for ion exchange of cations or anions generated by dissolving water-soluble substances contained in magnetic iron oxide. is 1 to 10 times larger. If the amount of ion exchange resin exceeds 100 times the theoretical amount, the time required for ion exchange will be shortened, but it will be difficult to filter and separate the used ion exchange resin from the slurry.
It is not suitable for industrial operations such as regeneration because it becomes difficult. When the amount is less than 0.5 times the theoretical amount, the effect of the presence of the ion exchange resin in the slurry is not sufficient. The water-soluble substances mentioned here are not particularly limited, but magnetic iron oxides usually contain cations of Na, Zn, and Ca, and anions of C1τSO, PO, etc. These include salts and hydroxides.

The use of an ion exchange resin in the present invention has an excellent effect in removing water-soluble substances consisting of these cations and anions.

Regarding the method of depositing a metal compound containing cobalt on the surface of magnetic iron oxide from which water-soluble substances have been removed,
Although not particularly limited, a method is usually used in which a metal salt solution is neutralized or hydrolyzed and a product thereof is deposited. The metal species of the metal compound to be deposited include Co, Fe, Mn, Zn, Ni, Cr, Cd, and Pb.
, Sn, etc., but other metal species may also be included.

Magnetic properties of cobalt-containing magnetic iron oxide obtained by the present invention,
In particular, the coercive force is improved compared to that of magnetic iron oxide containing cobalt after being simply treated with an aqueous medium without the presence of an ion exchange resin.

It is not yet clear why the cobalt-containing magnetic iron oxide obtained by the present invention has excellent magnetic properties, but when an ion exchange resin is present in a slurry in which magnetic iron oxide is dispersed in an aqueous medium, Due to the action of ion exchange ability, water-soluble substances contained in the magnetic iron oxide that cannot be sufficiently removed by simply dispersing it in an aqueous medium are easily dissolved, and a highly pure magnetic iron oxide surface can be obtained. It is also presumed that this makes it easier for the metal compound whose main component is colt to be uniformly deposited.

-5・ Explaining embodiments of the invention to a dog.

Example 1 200 g of acicular γ-Fe20s (coercive force Hc: 360 oersted, saturation magnetization 73e u/g, flat shaft diameter 0.4 μm, needle ratio about 10:1) was dispersed in about 20% water. , the slurry concentration was adjusted to 100 g/# of magnetic iron oxide. 500ml of this slurry was taken into a beaker, and while stirring, 40cc of Diaion 5KIB (manufactured by Mitsubishi Chemical Industries, Ltd.), which is a styrene-based strongly acidic cation exchange resin, was added.
Cations are exchanged while stirring. After that, 8
Remove the ion exchange resin using a 0 mesh sieve and transfer the four magnetic iron oxide slurries to a flask. While stirring this slurry well at room temperature, the Co concentration was adjusted to 508/ρ.
o50. -Add 7H20 aqueous solution 35-〇. Add about 12-0.2 of a 5N Na0)I aqueous solution to this slurry.
-/min over 1 hour. Furthermore, Fe
An aqueous solution 70- of FeSO4.7H20 adjusted to a concentration of 50 g/Q is added at a constant rate over 1 hour. This slurry was heated to 90°C and held for 3 hours, and then filtered and washed using a Bunner funnel. The powder was dried at 60° C. for one day and crushed in a mortar to obtain magnetic powder S-1. A portion of this magnetic powder S-1 was heat-treated at 200° C. for 1 hour and is referred to as magnetic powder S-1'.

6- The coercive force of the magnetic powders S-1 and S-1' was measured using a DC magnetization characteristic automatic recording device (manufactured by l! Kawadeniso Co., Ltd.).

Example 2 The procedure was the same as in Example 1 except that 80 cc of Diaion 8AIOA (manufactured by Mitsubishi Chemical Industries, Ltd.), which is a styrene-based strongly basic anion exchange resin, was used instead of 40cc of Diaion 5KIB. Magnetic powder S-2, S
-2' was created.

Example 3 Magnetic powder S-3 was prepared in the same manner as in Example 1 except that 40 cc of Diamond Ion SA I OA in addition to lee was treated at the same time.
, S-3' was created.

Comparative Example Magnetic powder 1.1' was prepared in the same manner as in Example 1 except that Diamond Ion 5K)B was not present.

The results of measuring the coercive force of the magnetic powders prepared in Examples 1 to 3 and Comparative Example are shown in the following table.

As is clear from Table L, it can be seen that the coercive forces of the Fval Y-containing magnetic iron oxide obtained in the present invention are all self-recorded compared to those of the comparative examples.

patent applicant Ishihara Sangyo Co., Ltd. 8-

Claims (1)

[Claims] An ion exchange resin is added to a slurry in which magnetic iron oxide is dispersed in an aqueous medium to remove water-soluble substances contained in the magnetic iron oxide, and then cobalt is added to the surface of the magnetic iron oxide. A method for treating magnetic iron oxide, which is characterized by depositing a metal compound as the main component.