KR940005273B1 - Method of manufacturing magnetic iron oxide powder - Google Patents

Abstract

The ferromagnetic ferric oxide ceramics for magnetic recording is prepared by (a) manufacturing geothite (alpha-FeOOH) reacted with alkali and iron ionic salt solution, (b) making magnetite by hydrogen reduction at 250-400 deg.C for 1-2 hrs. in hydrogen atmosphere after coating geothite with solution including 0.5-5.0 wt.% aluminum hydroxide, (c) adding 5-10 wt.% iron and 5-7 wt.% cobalt ionic salt solution, respectively to a coating solution, reacting with alkali and their salt solution, (d) coating magnetite with the coating solution to be coated with cobalt.

Description

Method of manufacturing iron oxide for magnetic recording

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing iron oxide for magnetic recording, and in particular, to solve the change with time due to air and heat of magnetite, to produce a magnetic body having excellent weather resistance and corrosion resistance, stable magnetic properties and excellent stability.

As various kinds of information and projection equipment are miniaturized and lightened, the information and video recording media used therein are getting higher quality and higher quality.

In order to pursue such high quality sound and high image quality, the recording density and characteristics of magnetic recording media can be improved only by improving the materials of magnetic recording media. Among them, the selection of magnetic materials is the most important and to improve the characteristics of recording media. Development of excellent magnetic material is in progress.

Suspension in which γ-Fe ₂ O ₃ is dispersed in water in order to deposit Co oxide on the surface of Co-containing γ-Fe ₂ O ₃ having improved properties since γ-Fe ₂ O ₃ has been used as a recording magnetic material used in the related art. Co ⁺² salt solution, Fe ⁺² salt solution and alkaline solution were added at a constant Mol ratio, and then oxidized in air at a temperature of 100 ℃ or lower, or the salt solution was reacted under heating and pressure in an autoclave at 100-300 ℃. Co-containing γ-Fe ₂ O ₃ is manufactured by hydrothermal reaction to obtain a precipitated product. In order to improve the properties of the prepared magnetic body, fine pores or materials inside the magnetic body of the conventional magnetic body are twigs outside the surface. In order to manufacture Co-containing γ-Fe ₂ O ₃ having excellent magnetic properties while coating with SiO ₂ or removing particle size to remove dendrite that has grown into crystal shape, etc. o nophi ⁺² content, or there is research being conducted in the direction to increase the Fe ⁺² content.

However, such a conventional recording magnetic material is superior to the conventional magnetic material when Co-containing γ-Fe ₂ O ₃ having excellent surface properties by coating SiO ₂ on the surface of the magnetic material is superior to the conventional magnetic material. The higher the quality, the higher quality of sound can be realized. However, since Co-containing γ-Fe ₂ O ₃ hardly raises the magnetic property by more than 800 Oe, it is difficult to realize a high quality and high quality magnetic recording medium. Increasing the Co ⁺² content in order to produce a good magnetic material increases the crystal magnetic anisotropy of Co ⁺² ions, that is, the energy required when the magnetic material is magnetized depends on the direction of the crystal. the aging phenomenon results in a change in the magnetic properties which blossomed and, because of changes in the magnetic recording medium according to the output attribute is temperature Co ⁺² The content was usually forced to be adjusted within the 4% range.

In addition, as the Fe ⁺² content increases during the preparation of the magnetic material by increasing the Fe ⁺² content, the magnetic properties and the appearance color of the magnetic material are yellow, brown, black gray, and the black γ-Fe ₂ O ₃ in black is black gray or black. Although the blackness of the black color of the appearance color is improved, the magnetic properties of the magnetic material change easily due to the change of Fe ⁺² to Fe ⁺³ and the magnetic properties of the magnetic material change with time. When the medium is manufactured, there is a disadvantage in that the output characteristics of the tape increase the risk of change over time due to the influence of temperature and the magnetic characteristics deteriorate with time.

The present invention improves the prior art by reacting a problem of magnetic material of the Fe ⁺² salt solution with an alkali to be for the production of magnetic iron oxide for the excellent magnetic properties than Co-containing γ-FeO ₃ was used for recording, such as the conventional ingot tight (α-FeOOH) to synthesize was prepared after the deposition process in Al ₂ O ₃ in the magnetic material surface is reduced by deposition treatment with Al ₂ O ₃ Fe ₃ O _4, i.e. magnetite (magnetite) after a certain amount of the Fe ^{+ It} is to produce ferromagnetic iron oxide with excellent corrosion resistance and surface properties and good magnetic properties by adding Co, ² , Co ^{+ 2} and alkali to the Co ₃ coating on Fe ₃ O ₄ surface.

Referring to the production method of the present invention in more detail, it works like Fe ⁺² by reacting the salt solution and alkali solution Fe (OH) ₂ to prepare the Fe ⁺² salt as FeCl _2, FeSO ₄ in a nitrogen atmosphere and KOHNaOH etc. can be used as an alkali. At this time, the ratio of Fe ^{+ 2} / (OH) ^- = R added is 2.5 to 6, more preferably 4 to 5, the coercive force at the time of gothite synthesis is the maximum. The prepared Fe (OH) ₂ was heated to 45 ° C. to 60 ° C. in a nitrogen atmosphere, and the precipitates were aged while stirring for 2 to 4 hours, followed by air oxidation at 50 ° C. to 80 ° C., preferably at 50 ° C. to 60 ° C., to give α- FeOOH is synthesized.

At this time, in order to find the end point of air oxidation, nitrogen treated with dilute hydrochloric acid at pH = 1∼6, and 5 ml of air oxidized slurries were collected at 10 min intervals, dissolved in dilute hydrochloric acid treated with nitrogen, and detected by Fe ⁺² detection paper. The end point is the reaction at the time when Fe ^{+ 2} is not detected. In this manner, α-FeOOH (Goatite) synthesized by air oxidation is washed with water and then added to distilled water to form a suspension. At this time, the concentration may be 5-100 g of gootite per 1 L of water, and then a small amount of surfactant may be added to assist the dispersion of the gootite, or a small amount of water glass may be added during surface deposition with a new compound. At this time, Al water-soluble compounds such as FeCl ₃ , Al ₂ (SO ₄ ) ₃ , NaAlO _2, etc. are added as the Al compound to be added. The amount is added in an amount of about 0.5% to 5.0% based on the weight of Fe of gothite. It is set to 8.5-10. If the pH is less than 8.5, the dispersibility of gothite is not good. If the pH is 11 or more, the adsorption of Al hydroxide compound is suppressed and the needle accommodating property is reduced during reduction. In this case, the temperature of the Al water-soluble compound is 10 to 50 ° C. At 10 ° C or lower, the adsorption rate of the Al hydroxide is slow and the adsorption is uneven, and at 50 ° C or higher, Al (OH) is used. ) ₃ is glass precipitated.

The addition time of the Al water-soluble compound is 1 hour or more, but if less than 1 hour, the adhesion of Al hydroxide becomes uneven. In addition, the viscosity of the suspension is kept constant at the time of addition, and the addition of the Al compound is stopped when the viscosity is increased. As such, the Al hydroxide is adsorbed on the surface of the gothite, filtered, dried in a spray dryer, and then reduced in a hydrogen atmosphere at 250 to ₄₀₀ ° C. for 1 to 2 hours, thereby γ-FeOOH is converted into Fe ₃ O ₄ (Magnetite). In turn, the hydroxide adsorbed on the surface is converted to Al ₂ O ₃ . The thus Magnetite after the powder was dispersed in water and then treated with nitrogen was added to NaOH of 2mol charged into the Fe ⁺² salt solution of about 5 to 10 weight% of the Fe in magnetite Fe (OH) ₂ hydroxide formed by the Into the included magnetite slurry, Co ^{+ 2} saline solution of 3-7% of the Fe weight of the magnetite is added and aged for 30 minutes to 3 hours. At this time, the pH of the added alkali is fixed to 11 and kept constant. After aging, the slurry was filtered and washed with water, and then the filtered magnetic material was poured into an automatic high pressure cooker with water, treated with nitrogen, sealed, heated at 150 to 250 ° C. under steam pressure for 1 to 10 hours, and then filtered and dried to form Fe _3. O ₄ will be prepared. Specific embodiments of the present invention are as follows.

Example 1

5L each of aqueous solution of 300g of FeCl ₂ and NaOH solution of 1kg of NaOH was prepared and reacted under nitrogen atmosphere to form Fe (OH) ₂ precipitate. Then, air was blown at 40 ° C. at 4ℓ / min for 3 hours to add α-FeOOH. After preparing, washing with water, NaOH was added thereto, the pH was fixed at pH 9.5, and an aqueous solution of sodium aluminum acid was added at 7 ° C. for 4 hours at 20 ° C. At this time, a small amount of 0.5mol HCl aqueous solution was added to suppress the increase of pH, and the pH was maintained at 9.5. Al hydroxide was adsorbed onto the α-FeOOH surface with a viscosity of 20 CPS, and then filtered and sprayed in a spray dryer. After drying for 1 day at 40 ℃ or less and reducing for 1 hour at 350 ℃ hydrogen atmosphere to synthesize Al ₂ O ₃ adsorbed magnetite (Fe ₃ O ₄ ) 100g of this magnetic material was dispersed in water to 800ml slurry ( slurry) was added aqueous NaOH solution and then made 100ml of 10mol FeCl ₂ was added to an aqueous solution of nitrogen and then treated 0.9mol Fe (OH) ₂ and magnetite (Fe ₃ O ₄₎ to 0.85mol 50ml CoCl ₂ aqueous solution to a slurry containing the After the addition, the slurry was filtered and washed with water after 2 hours of aging while maintaining the pH = 11, and then the washed slurry was put in an autoclave and subjected to nitrogen treatment, heated at 250 ° C. for 5 hours under saturated steam pressure, and then dried at 50 ° C. By then producing the magnetic body to the Co-containing Fe ₃ O _4, by using this magnetic material creating a magnetic paint was applied to polyester film was measured for magnetic properties.

Example 2

1 l of distilled water was added to 100 g of α-FeOOH prepared in the same manner as in [Example 1], and 2 g of water glass was added thereto, a small amount of hydrochloric acid was added thereto, stirred at pH 2 to 7 for 30 minutes, and caustic soda was added thereto. Acid soda and hydrochloric acid were added and stirred in the same manner as in [Example 1], and deposited and treated with SiO ₂ and Al ₂ O ₃ on the surface of α-FeOOH, followed by Co-containing Magnetite (Fe) in the same manner as in [Example 1]. ₃ O ₄ ) were synthesized, magnetic paints were made, and the magnetic properties were analyzed after application to the pulley film.

Comparative Example 1

Α-FeOOH prepared in Example 1 was reduced in a hydrogen atmosphere at 350 ° C. for 1 hour to synthesize magnesium titanate (Fe ₃ O ₄ ), which was not deposited on aluminum, and then water was added to 100 g of the prepared magnetic material. After the slurry was prepared, 100 ml of 10 mol of NaOH aqueous solution was added thereto, followed by nitrogen treatment. Then, 0.9 mol of FeCl ₂ aqueous solution was added to the slurry mixed with Fe (OH) ₂ and magnetite, 50 ml of Co aqueous solution was added dropwise to 50 ml, followed by pH = 11. After standing for 2 hours, the slurry was filtered, washed with water, placed in an autoclave, treated with nitrogen, dried at 250 ° C. for 5 hours under saturated steam pressure, and dried at 50 ° C. to prepare α-Fe ₂ O ₃ containing Co without Al and SiO ₂ deposition. Then, the magnetic coating was made using the magnetic material, and the magnetic properties were analyzed after coating on the polyester film.

Comparative Example 2

The magnesite prepared in [Comparative Example 1] was reoxidized at 250 ° C. for 5 hours to produce γ-Fe ₂ O ₃ , and then Co-containing γ-Fe in the same manner and conditions as in [Example 1] without Al deposition treatment. ₂ O ₃ was prepared, and then a magnetic paint was prepared as in [Comparative Example 1], and then coated on a polyester film to analyze magnetic properties as in [Example 1].

The magnetic paint prepared as in Examples and Comparative Examples described above is made of a magnetic paint with a composition consisting of a magnetic material 100g, a vinyl provider 10g, polyurethane 10g, dispersant 2g, toluene 122g, methyl aryl keron 111g, cyclohexanone 50g After coating on the polyester base film, the magnetic recording medium was made, and the magnetic properties were measured by using a vibrating magnetic measuring device. After standing at 60% at 90% RH for 15 days, the magnetic properties were analyzed and the weather resistance was measured. Table 2 shows.

TABLE 1

TABLE 2

According to the present invention, as described above, during the synthesis of magnetite (Fe ₃ O ₄ ), α-FeOOH was heated and dehydrated to prepare α-Fe ₂ O ₃ , followed by hydrogen reduction to produce magnetite, followed by Co deposition. In the present invention, by directly reducing the α-FeOOH to synthesize the magnetite (Fe ₃ O ₄ ), the surface and acicular properties of the particles are excellent, and the Al ₂ O ₃ surface treatment not only excellent corrosion resistance but also by Co coating A ferromagnetic iron oxide for recording having excellent magnetic properties can be made.

Claims (4)

Fe ^{+ 2} salt solution reacts with alkali to make gothite (α-FeOOH), and gothite (α-FeOOH) is deposited with aluminum hydroxide and hydrogen-reduced in a hydrogen atmosphere to give magnetite (Fe ₃ O ₄ ) And the ferromagnetic iron oxide manufacturing method of ferromagnetic iron oxide (Fe ₃ O ₄ ) prepared by Co-treated magnetite (Fe ₃ O ₄ ) by adding Fe ⁺² and Co ⁺² salt to react with alkali. . The method of manufacturing iron oxide for magnetic recording according to claim 1, wherein the aluminum hydroxide is reacted at 0.5 to 5.0% wt% with respect to the weight of Fe in the range of pH = 8.5 to 10. The method of claim 1, wherein the hydrogen reduction treatment is performed for 1 to 2 hours in a hydrogen atmosphere at 250 ° C to 400 ° C to produce magnetite (Fe ₃ O ₄ ). According to claim 1, Fe ^{+ 2} salt is 5 ~ 10% wt% based on the weight of Fe, Co ^{+ 2} salt is added 5 ~ 7% wt% and reacted with alkali to give a Co-deposited magnetite (Fe ₃ O ₄ ) manufacturing iron oxide for magnetic recording, characterized in that for producing.