JPS5921529A - Manufacture of magnetic iron oxide powder for magnetic recording material - Google Patents

Abstract

PURPOSE:To develop magnetic iron oxide powder for a magnetic recording medium having high coercive force and undergoing little changes in the coercive force with the passage of time by depositing Co,Fe (II), and Ba or Sr to magnetite particles contg. solubilized Co. CONSTITUTION:To a dispersion of magnetite particles contg. solubilized Co are added an aqueous soln. of a Co salt such as cobalt sulfate, an aqueous soln. of a ferrous salt such as ferrous sulfate, ferrous chloride or ferrous nitrate, and an aqueous soln. of a Ba salt such as Ba chloride, sulfide or carbonate or an Sr salt such as Sr chloride, sulfate or carbonate. The concn. of OH groups in the prepared liq. is adjusted to 0.05-3.0mol/l by adding an aqueous soln. of an alkali such as NaOH, and the liq. is mixed by stirring at 50-100 deg.C in a nonoxidizing atmosphere to deposit 0.1-10wt% Co, 0.1-15wt% Fe as Fe<++>, and 0.05- 10wt% Ba or Sr on the surfaces of the magnetite particles. The resulting magnetic iron oxide powder has superior stability and can be utilized as a magnetic material for high sensitivity, high output and high density recording.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides magnetic iron oxide particles for magnetic recording particles, particularly cobalt solid solution magnets 4) K7''p Nicohart, m-
This article relates to a method for producing magnetic iron oxide particles coated with iron and barium or strontium, and details 1. <
relates to a method for producing magnetic iron oxide particles that have a high coercive force, have little change in coercive force over time, and do not deteriorate transfer characteristics when used as a magnetic recording medium.

In recent years, as magnetic recording and reproducing equipment has become smaller and lighter, there has been an increasing need for higher performance magnetic recording media such as magnetic recording media and magnetic disks. There is a demand for improvements in performance such as high recording density characteristics, high output characteristics, and high sensitivity characteristics.

The characteristics of magnetic iron oxide particles suitable for satisfying the above-mentioned requirements for magnetic recording media are that they have high coercive force He and high saturation magnetization σS in their magnetic properties.

For this reason, cobalt-containing magnetite particle powder obtained by modifying magnetic iron oxide particles used in magnetic recording media with cobalt or the like has not been proposed.

This -J balt-containing magnetite particle powder can be roughly classified into the following 21] depending on the method of transforming -1 balt.

(1) By adding 1 balt at the stage of forming hydrated ferric oxide particles! 1 belt to a hydrous oxidation containing a concentration like -' ~ diiron I'/-f-? 4I, a method for reducing the particles, a method for producing so-called '-1 bar/l, l solid solution magnetite particles.

(For example, Special Publication No. 3'7-9457 Bow Publication, Special Publication No. 49
-4264 Publication) (2) Is it special to add =1 balt or cobalt and ferrous iron to macnetite particles? (☆) is the so-called cobalt-coated manetite particle generation Jj method. (For example,
Japanese Patent Publication No. 47-22707-” (', Publication, 1)
-20098 Kano Publication, Visit ff14B-46899 Kano Publication, Ekikai 49-1118599''r'i Publication, Special Publication 47-27719';3 Publication, Special Publication Sho/1B-N'1
Publication No. 99.1, Special Publication No. 49-49475, Special Publication No. 2,17-7, Special Publication No. 52-28238
Nikkeiho, 1゛IC Kimiaki! 32-56751 yen, Public bulletin,
The '-1 baltic solid solution magnetite particles obtained by the method described in (1) in Japanese Patent Publication No. 52-686 Roshi J. Publication) have a high coercive force.
It has been pointed out that it is extremely unstable thermally and over time due to heating demagnetization, pressurization demagnetization, etc.

On the other hand, cobalt-coated magnetite particles obtained by the method (2) show little change in coercive force over time, but a coercive force of only about 500 to 6000 e can be obtained, which is currently required in the F1 industry. It is difficult to obtain a high coercive force in the past.

In addition, recently, the method (1) above, that is, an improved technique in which cobalt is further deposited on the particle surface of cobalt solid solution magnetic iron oxide particles (for example, JP-A-54-122664, JP-A-55-72009) Publication No. 2) has also been proposed.

Although the cobalt-containing magnetic iron oxide particles obtained by the above-mentioned improved technique exhibit particularly high coercive force characteristics, the above-mentioned (
Compared to the cobalt-coated magnetite particles obtained by method 2), the coercive force changes over time to a large extent, and it cannot be said that the particles are suitable for use as a magnetic recording medium.

The present invention belongs to an improvement technique of the method (1) above.

In order to obtain magnetic iron oxide particles having a property of high coercive force, the present inventor considered that cobalt solid solution magnetic iron oxide particles should be coated with cobalt and ferrous iron.

However, it is known that the larger the amount of cobalt and ferrous M, the more effective the coercive force is.
When used as a recording medium, the γf characteristics will deteriorate.

The present inventor has addressed the above-mentioned phenomena as follows: 9@, 7. , JDf research has been carried out in order to obtain magnetic iron oxide particles that have high coercive force, have little change in coercive force over time, and at the same time have improved transfer characteristics when used as a magnetic recording medium1. If barium or strontium is used at the same time when cobalt and ferrous are deposited on cobalt solid solution magnetite particles, the cobalt and ferrous will have a high coercive force even if the amount of deposited is small. In addition, magnetic iron oxide particles with a small change in coercive force over time can be obtained, and at the same time, when used as a magnetic recording medium such as magnetic deso, the transfer characteristics deteriorate due to the reduced amount of ferrous iron17. They discovered a phenomenon in which the

Based on the phenomenon described above, the present inventor conducted repeated autopsies on various conditions for coating cobalt solid-solubilized magnetite particles with cobalt, ferrous iron, and barium or strontium, and as a result, completed the present invention. It was.

In ff1J, the present invention uses cobalt solid-solubilized magnetite particles as precursor particles, adds a cobalt salt aqueous solution, a ferrous salt aqueous solution, and a barium or strontium salt to a dispersion of the precursor particles, and then adds an alkali. Cobalt, cobalt, After depositing ferrous iron and barium or strontium,
1. A method for producing a magnetically resistant iron particle powder for use in magnetic recording materials, which is characterized by drying.

Next, the present invention will be explained in detail.

The feature of the present invention is that cobalt solid-dissolved magnetite particles are used as precursor particles, and each of these cobalt particles is used as a precursor particle.
・By depositing ferrous iron and barium or strontium, obtain magnetic iron oxide particle powder that has high coercive force, has little change in coercive force over time, and does not deteriorate transfer characteristics when used as a magnetic recording medium. It is something. still,
In the method of the present invention, there is still insufficient theoretical consideration as to the mechanism by which Co/L/T, ferrous, and barium or strontium deposits occur on the surface of cobalt solid-solubilized magnetite grains. Although it has not been tested, cobalt, ferrous iron, and barium or strontium work synergistically to improve various magnetic properties, including obtaining a high coercive force. I think this is due to this. Moreover, since magnetic iron oxide particles with high coercive force were obtained even when the amount of ferrous iron was reduced, it is believed that magnetic iron oxide particles with less change in coercive force over time can be obtained.

Next, various conditions in the present invention will be explained.

First, the amounts of cobalt, ferrous iron, and barium or strontium to be deposited will be described.

The amount of cobalt deposited is desirably 1D to 1D weight % as Co based on the precursor particles (cobalt solid-solubilized magnetite particles). If the coating weight is less than 0.01 weight, the coating effect of cobalt will not be noticeable. If the amount is 10% by weight or more, the coercive force distribution of the obtained magnetic iron oxide particles tends to become large, which is not desirable.

As the cobalt salt used in the present invention, water-soluble salts such as cobalt sulfate and cobalt nitrate can be used.

The amount of ferrous iron deposited is desirably 01 to 15% by weight as Fe'+ based on the cobalt solid-dissolved magnetite particles of the precursor.
stomach. If it is less than 0.01% by weight, the effect of improving coercive force will be low and the electrical resistance will increase. On the other hand, when +5iij1% or more -L, a synergistic effect with barium or strontium appears, and the change over time in the coercive force of the obtained magnetic iron oxide particles increases, furthermore, the rolling effect worsens. Undesirable.

The ferrous salts used in the present invention include ferrous sulfate, ferrous chloride, and ferrous nitrate.

The amount of barium or strontium deposited is preferably 0.05 to 10% by weight as J3a or Sr based on the precursor cobalt solid solution magnetite particles. If the amount is 0.05% by weight or more, no adhesion effect, ie, an effect of improving coercive force, can be expected. On the other hand, if it is 10% by weight or more, the saturation magnetization decreases, and it is preferable that I7<<.

As the barium salt, barium chloride, barium sulfate, barium carbonate, etc. can be used, and as the salt, for example, strontium chloride, strontium sulfate, carbonate, etc. can be used.

Next, cobalt solid solution magnesium as precursor particles (7)
・Particles are obtained by adding a cobalt salt aqueous solution during a wet reaction with an aqueous solution of a ferrous sulfate salt to obtain a ferric oxide (JO) containing hydrated ferric oxide particles. IJI
I thermal dehydration 1-, then 1-1 treatment,
Alternatively, it refers to particles in which cobalt is adsorbed on ferric oxide grains in the form of field-like hydrous acid fIS or particles 11r1 of 1,000 Φ1-shaped ferric oxide grains, which are then subjected to reduction treatment 11. From the IH+ perspective of the present invention, it is sufficient for the cobalt-containing fi*et to be 01 to 25 atomic % in terms of C○ compared to FθG.

Next, 01 of 11 maids (base concentration is D, 0.5-roTJ
J Tll○r7”e must be y (i.005m
off, in the case of i to t'', the configuration does not occur for 1 minute.On the other hand, in the case of 3.1 m o l!/, ) to -I, C=-,
This is not preferred because cobalt hydroxide begins to dissolve.

The liquid temperature needs to be in the range of 50-100°C.

5 (If the temperature is higher than 100°C, it is difficult to produce the target product of the present invention, and even if it is produced, it will require extremely long processing times.On the other hand, if the temperature is higher than 100°C, special equipment is required. Requires.

Also, is the present invention non-intoxicating and intoxicating? What you can do with 1 tortoise is:
Cobalt hydroxide IL, ) and iron hydroxide remain stable in solution.
1: I am here to study. That is, in the 345 cases of the chemically oxidizing atmosphere (-, 1 fraction y (cobalt hydroxide and water 1), the chemical transforms the precursor ＼ν (- and 7I゛< 14 Then, Somama-1/,) Pardon Hit C (-Zanzai Ark Meho 1: 1.Bei ↓゛Igara-(There is.

History cJ-1 [) IJ Book (7) t) +-+ g, ia
J! V, solution 11A l-'J5, non-rVIization $
Stir 7J with 1jll air σ)-Hj and article f'1? , coalescence 4
This is because the precursor particles, cobalt hydroxide, iron hydroxide, burrs, and salt are uniformly brought into contact with each other, and the adhesion layer becomes clear. This is to reduce the crystal growth of 11-.

The present invention, which has the same structure in the layer, has the following effects (σ)
Out.

That is, according to the present invention, cobalt solid solution magenta (%')
＞' Child: 1 Baltic, ferrous and barium or str
Magnet which has high coercive force by depositing with 1 inch /1: rV! Iron chloride particles can be used as a magnetic H material for high sensitivity, high output, and high density recording with excellent stability, which is currently the most stable.

Historically, the magnetic iron oxide particles obtained by the method σ) of the present invention have a coercive force of about 10% compared to the case of depositing with cobalt and ferrous iron when trying to obtain the same level of coercive force. Only a small amount of iron is needed, the coercive force changes less over time, and the magnetic properties can be stabilized by improving the transfer properties when used as a magnetic recording medium such as a magnetic tape.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1゜CO solid solution gold monoform magnetite particles (coercive force HC: 384
0e, saturation magnetization 6q: B7. Aθmu/g, Oo
/p e :03 at%) as the precursor particles, and the particles 1
kg in 11]61 of water, and the dispersion (this
SO4・7H,,095,4g4 dissolved aqueous solution500
Solution 1XFeSO4・7075. Aqueous solution containing OQ dissolved 207m/! and SrO/! 2.6H,,030,4g
3,410 gf of an aqueous solution in which the dispersion was dissolved was added to prevent air from entering, and 1,185 ml of a 1B-N NaOH aqueous solution was added while stirring and mixing.Next, the crystallinity of the dispersion was adjusted to 95° (-) (maintaining this). 7. To prevent the contamination of empty °C, stir and mix again.Then, take out the slurry, add 5'l' of water and add 1.'0°C.
Dry the eaves at a temperature of 1. Example 1: Cobalt solid solution magnetite particle powder coated with 11 balt, ferrous iron and strontium 11.

? [I ran Cobalt, Daiichi Tetsu and Strongy
Cobalt solid solution magnetite particles/powder deposited with ?
As a result of determining the a time characteristic, the coercive force He:
6JIn (lie.

Saturation magnetization σ days: 78 em’ll/q.

Table 2 shows the coercive force when the cobalt solid-dissolved magnetite particles coated with Cobal I, Ferrous, and Ronchiu J were allowed to stand at room temperature (h).

1-] Using cobalt solid solution magnetite particle powder coated with cobalt, ferrous and strontium,
・After 7, mix the binder composition as shown and mix it to make a magnetic paint.

Magnetic iron oxide particle powder 100g Vinyl resin (vinyl acetate: vinyl chloride 20q-3+91 copolymer) 2) Lil rubber 5q Torudan 1009 Methyl ethyl ketone 75f7 Notyl isobutyl ketone
75 Q and 7 Shi Chin

Add a solvent (toluene: methyl imbutyl ketone = 1:1:1) to the magnetic paint containing 0.2 g < 1 and adjust it to the appropriate paint viscosity. A magnetic coating film was formed by coating it on a polyester resin film. Coercive force Hc of this magnetic coating film
was 6810θ.

Next, the magnetic coating film was cut into a predetermined width to form a magnetic deso, and the transfer effect of the magnetic deso was measured according to the JIS 05542 J magnetic recording tape test method-158 transfer method, and the result was 51.5 dE. Met.

Examples 2 to 7 Various conditions such as the type of precursor particles, the type and amount of cobalt salt, ferrous salt, barium or strontium salt, solution humidity, OH group concentration, stirring conditions, etc. Similarly, a cobalt solid solution magnetar coated with cobalt, ferrous, and variuno or strontylano particles was also used.

The main manufacturing conditions and characteristics are shown in Tables 1, 2, and 2.

Comparative Examples 1 and 2 Cobalt solid solution magnetite deposited with cobalt and ferrous iron in the same manner as in Example 1 except that barium or strontium salts were not added and the type of precursor particles was changed. Particle powder? (It's I.

The main manufacturing conditions and characteristics are shown in Tables 1 and 2.

Claims (1)

[Claims] 1) Cobalt solid-dissolved magnetite particles are used as precursor particles, and a cobalt salt aqueous solution, a ferrous salt aqueous solution, and a barium salt are added to the dispersion of the precursor particles. By stirring and mixing a dispersion liquid in which a ndium salt was added and then an alkali was added to adjust the OH group concentration in the liquid to 005 to 30 m01'/1 in a non-oxidizing atmosphere at a liquid temperature of 50 to 100'C. A method for producing magnetic iron oxide particles for magnetic recording materials, which comprises coating the precursor particles with cobalt, ferrous iron, and barium or strontium, and then drying the precursor particles. 2) The method for producing magnetic iron oxide particles for magnetic recording materials according to claim 1, wherein the amount of cobalt deposited is 01 to 10% by weight of Co based on the cobalt solid-dissolved magnetite particles. 3) The magnetic iron oxide particle powder for magnetic recording materials according to claim 1 or 2, wherein the amount of the -tA deposited is 01 to 15% by FeII binding based on the cobalt solid solution magnetite particles. 6.4) C') The amount of ram coated is: 05-10% by weight of Ba and UO per 1 Baltic solid solution mamagnetite particle, according to claims 1 to 5. A method for producing magnetic iron oxide particles for use in magnetic recording according to any one of the above. 5) The magnetic recording according to any one of claims 1 to 3, wherein the amount of strontium deposited is 5 to 10% by weight as Sr with respect to the cobalt/magite grains -f. A method for producing magnetic iron oxide particles for use.