JPS59107503A - Method of manufacturing magnetic powders with iron as main constituent for magnetic recording - Google Patents

Abstract

PURPOSE:To provide magnetic powders with sufficiently large coercive force and improve saturated magnetic flux density, by a method wherein Co, Ni or the like is adhered to iron oxyhydroxide with specified major axis length and minor axis lenght or to that doped by Co, Ni or the like, and then reduction is performed in a reducing gas atmosphere. CONSTITUTION:Iron oxyhydroxide such as alpha-FeOOH having mean major axis length of 0.2-2mum perferably 0.5-1.5mum and mean minor axis length of 0.01- 0.1mum preferably 0.03-0.08mum, iron oxide such as alpha-Fe2O3, and doped substance of metal such as Ni, Co or alloy thereof onto above-mentioned iron oxyhydroxide or iron oxide are used. Hydroxide or oxide of Co, Ni is adhered, adsorbed or deposited to iron oxyoxide or iron oxide and the surface coating treatment is performed. The treated substance is dried and then reduced in a reducing gas atmosphere such as hydrogen at a temperature of 600 deg.C or less. In this constitution, magnetic powders are obtained at iron content 70-98wt% and coercive force of 160Oe or more.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing magnetic powder for magnetic recording with high coercive force and saturation magnetic flux density suitable for high-density recording, particularly magnetic powder for master tapes. 5. By contact transfer method. In the magnetic recording duplication method, the master tape is required to have a much larger coercive force than the magnetic tape to which magnetic transfer is performed, and the magnetic powder used in the master tape is required to have a coercive force of 16,000 e or more6. Furthermore, excellent magnetic properties such as low noise (and high BlN ratio) are also required. Therefore, in addition to high coercive force, the magnetic powder used for the master tape is also required to have high saturation magnetic flux density and high dispersion. .

An object of the present invention is to provide a method for producing magnetic powder for a master tape that satisfies the above conditions and has a sufficiently large coercive force, a high saturation magnetic flux density, and excellent dispersibility.

As a method for producing magnetic powder for master tapes having a coercive force of 16,000 e or more, the following methods have been considered.

(1) A method in which ferromagnetic metals and alloys are evaporated in an inert gas.

(2) A method of wet reduction of a ferromagnetic metal salt with sodium borohydride in its solution.

However, none of these methods can be considered definitive from an industrial or practical standpoint. That is (1)
The evaporation method requires complicated equipment and operations, making it unsuitable for large-scale implementation, and (2)
In the wet reduction method, the magnetic powder obtained has a high surface activity, so it is highly self-combustible, and it is also weak against oxygen and moisture in the air, resulting in a decrease in magnetic properties.
The individual particles are filamentous, and during the mixing process with the binder, the particle shape is destroyed, the magnetic field orientation deteriorates, and the magnetic properties of the magnetic recording medium, especially the squareness ratio, deteriorate. are doing. - Compared to these methods, the dry heel method using iron beoxyhydroxide as a starting material is suitable for mass production and is economically advantageous; Not manufactured in the name.

The reason for this is that reduction is usually carried out at high temperatures in a hydrogen stream;
This is because a magnetic powder suitable for use in master tapes could not be obtained because volume reduction, porosity, shape change, and sintering occurred.

The present inventors have arrived at the present invention as a result of intensive research in order to solve the drawbacks of the above reduction method and obtain magnetic powder suitable for use in master tapes. That is, in the present invention, the average major axis length is 0.2 to
Iron oxyhydroxide, iron oxide, or co-co
Doped with metals such as Ni, Mn, and z'n, treated with one or more compounds selected from compounds of oo, Ni, Mn, and Zn to attach, adsorb, or precipitate them. After that, the treated product is dried and then reduced at a temperature of 200 to 600°C in a reducing gas atmosphere, and the magnetic powder for magnetic recording has a coercive force of f6000O or more and contains 70 to 98% iron by weight. The present invention provides a method for manufacturing.

The starting material of the present invention has an average major axis length of 0.2 to 2 μm and an average minor axis length of 0.01 to 0.1 μm%, more preferably an average major axis length of 0.5 to 1.5 μm. .

α-Fe with an average minor axis length of 0.03 to 0.08 pm
20H.

iron oxyhydroxides such as β-FeOOH and y-FeOOH,
α-Fe20. ,7-Pa,,O,,re,O,,7
-Fe,,O,-Fe,0Ll(BerthOri(l
iron oxides such as e compounds) and these with Ni and Co
, doped with one or more of metals such as Mn and Zll, or compounds thereof.

In addition, Oo, Ni, Mn and z used in the present invention
Any compound n can be used as long as it is water-soluble or colloidal. Preferably used compounds include co O4T Ni cZ2 t Mn 0
4 and Zn Oh-like chlorides%0oSO,,N15
O,, salts such as sulfates and nitrates such as Mn80° and Zn S Ou, 00 (0H) x a! 2-x
+ N1 (oH)x cA2- XT MnX(o
H) x c! 2-x and Zn(0H)Xc-”2-x
Examples include hydroxides or partial hydroxides such as (x is 1 or 2), colloidal compounds, and the like.

Regarding the magnetic powder obtained in the present invention, the iron content and
70-98 wt% when analyzed by atomic absorption spectrometry
It must be. The coercive force of magnetic powder varies depending on its alloy composition, magnetocrystalline anisotropy, shape anisotropy, etc., but in the magnetic powder of the present invention whose main component is iron, the iron content outside the above range is Then, the coercive force becomes less than 16,000O.

Next, preferred embodiments of the method for obtaining magnetic powder of the present invention will be explained.

First, when treating a compound of Oo, Ni, Mn, or Zn to iron oxyhydroxide or iron oxide, when a water-soluble salt is used as the compound of Co, Ni, Mn, or Zn, the above-mentioned oxyhydroxide is added to the solution. Disperse ZFia iron.

The effect can be seen just by stirring for a certain period of time and making sufficient contact with the soluble salt, but to increase the effect even more, after dispersing iron oxyhydroxide or iron oxide, if the soluble salt is alkaline, add hydrochloric acid, sulfuric acid, nitric acid, With acids such as phosphoric acid, father,
If the soluble salt is acidic, it is completely or partially neutralized with one or more alkalis selected from alkalis such as caustic soda, caustic potash, or ammonia;
One or more of the hydroxides or oxides of Ni, Mn, and Zn are deposited, adsorbed, or precipitated on iron oxyhydroxide or iron oxide, and treated to form a surface coating. In addition, in order to improve the dispersion of the iron oxyhydroxide or iron oxide in this treatment, sodium oleate,
Use of a surfactant such as sodium alginate can also further improve the effects of the present invention.

Subsequently, after drying the iron oxyhydroxide or iron oxide subjected to these treatments, the temperature preferably does not exceed 500°C.
Reduction is carried out in an atmosphere of a reducing gas such as hydrogen at a temperature not exceeding 00°C. There is actually no lower limit to the reduction temperature, but since the reaction proceeds very slowly at low temperatures, it is practically preferable to carry out the reduction at a temperature of 200°C or higher, preferably 250°C or higher.

After the reduction, the reducer is cooled, and a mixed gas of 14 air and 99 ml of soybean is introduced into the reducer, and the air content of this gas is increased stepwise or gradually until it becomes only air after 4 to 5 hours.
Take out the ferromagnetic powder.

Next, the present invention will be explained in more detail with reference to Examples.
This example does not limit the invention.

Example-1 The average long axis length is 1.0 μm and the average short axis length is 0.0 μm.
03μm needle a-Fe0OH80f 6! Suspend in water and disperse with a stirrer. Cobalt chloride IM/
Add 45 cc of solution A and stir. Then another 2 N
-NaOH45 (!c) is added, stirred for about 30 minutes after addition, filtered and washed to obtain a wet α-FeOOH cake. This is dried overnight at a temperature of about 150°C. Take 10F of this dry cake and A ferromagnetic powder with an iron content of 95% by weight was obtained by centrifugation for about 7 hours at a hydrogen flow rate of 5!/min at ℃.The magnetic properties of the obtained magnetic powder are as follows (values measured with IQKOe). .

Similarly, Ho is coercive force, σ is residual magnetic flux density, σB is saturation magnetic flux density, and σr/σ8 is squareness ratio.

“C” “” Oee σy =82.1 em
u / tσ days = 161 θmu/f l σr/
σ8 = 0.51 Example The average major axis length is 1.0 μm and the average minor axis length is 0.0
4 μm needle-like a-Fe0OH80t 6! Suspend in water and disperse with a stirrer. In this, nickel chloride IM/A
Add 45 cc of solution and stir. Then another 2N-N
Add 45 cc of aOH, stir for about 30 minutes after addition, and filter and wash to obtain a wet α-FeOOH cake. This film is dried overnight at a temperature of about 150°C. This dried cake 10
Take V and hydrogen flow rate is 3 at 350 ℃! A ferromagnetic powder having an iron content of 95% by weight was obtained by dispersing the powder at a rate of 1/min for about 7 hours. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOθ).

Hc=18100θ, σr=76.5 emu, /
1clB = 155 emu/j' I dr/elB
= [1,50 Examples The average major axis length is 1.2 μm and the average minor axis length is 0.0
4μm) Needle-shaped a-Fe0O■80f is added to the water in step 6) and dispersed using a stirrer. In this, manganese chloride IM/i
Add 45 cc of solution and stir. Then another 2N-N
Add aOH45c'c, stir for about 30 minutes after addition, and filter and wash to obtain a wet α-FθOOH cake. This is dried overnight at a temperature of about 150°C. This dried cake 10
ft1" was taken and centrifuged at 350°C for about 7 hours at a water ice flow rate of 3!/min to obtain a ferromagnetic powder with an iron content of 96% by weight. The magnetic properties of the obtained magnetic powder are as follows ( Measured value at 10KOe).

He” 19300e, (11” 72.58
mu/lσB = 148 emu/r, dr/
dB =, 0.49 Example-4 The average major axis length is 0.6 μm and the average minor axis length is 0.0
Suspend 2 μm needle-shaped (z -Fe0OH80f in 6! of water and disperse with a stirrer. Add 45 cc of zinc chloride 1M/7 solution and stir. Then add 2 N -N
Add 45 cc of aOH, stir for about 30 minutes after addition, and filter and wash to obtain a wet α-FeOOH cake. This is dried overnight at a temperature of about 150°C. This dried cake IQf
At 350℃, hydrogen flow rate is 3! A ferromagnetic powder with an iron content of 95% by weight was obtained by spinning for about 7 hours at a speed of 100%. The magnetic properties of the obtained magnetic powder are as follows (values measured at 10 KO).

He = 18700e, σl = 72.5
emu/rσ, = 145 emu/l +σr/
σ8 = 0.50 Example-5 The average major axis length is 0.8 μm and the average minor axis length is 0.0
5 μm cobalt-doped needles a-Fe0OH(O.

/Fθ=11) 80f is 6! Suspend in water and disperse with a stirrer. 90 cc of cobalt sulfate IM/A solution is added to this and stirred. After that, 90cc of 2N-NaOH
After the addition, the mixture was stirred for about 130 minutes and then filtered and washed to obtain a wet α-FθOOH cake. This is dried overnight at a temperature of about 150°C.

Take 1Qr of this dry cake and heat it to 550°C with a hydrogen flow rate of 3!
A ferromagnetic powder having an iron content of 90% by weight was obtained by dispersing the powder at a rate of 1/min for about 7 hours. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOθ).

Hc = 1980 0e, (y, = 80,6
emu/rσB = 155 emu/r,
σr/σ, = 0.52 Example-6 Average major axis length is 0.7 μm''' and average minor axis length is 0
．． 0+μm acicular a-Fe,, 0.80 f 6! Suspend in water and disperse with a stirrer. In this, cobalt chloride 1'
Add 200 cc of M/A solution and stir. After that, 2N-NaOH200QC was further added, and after the addition, about 3
After stirring for 0 minutes, the mixture was filtered and washed to obtain a wet α-Fθ20° cake. This is dried overnight at a temperature of about 150°C. Take this dry cake 102 and heat it to 350°C with a hydrogen flow rate of 3! /min for about 7 hours to obtain ferromagnetic powder with an iron content of 84N. The magnetic properties of the obtained magnetic powder are as follows (1
Measured value at 0KO,).

Hc = 18500e, a, = 79,9e
mu/f6B = 163 emu/r t' (1
rhB = 0.49 Example-7 The average major axis length is 1.5 μm and the average minor axis length is 0.0
6 μm needle-like a-Felon 80f is suspended in 61/ml of water and dispersed with a stirrer. Cobalt chloride 1/
I! /45cc of solution and nickel chloride AtIM/j
Add 45 cc of solution and stir. Then another 2N-N
Add 90 cc of aOH, stir for about 50 minutes after addition, and filter and wash to obtain a wet α-FeOOH cake. This is dried overnight at a temperature of about 150°C.

Take 10 tons of this dried cake and heat it to 350°C with a hydrogen flow rate of 3!
A ferromagnetic powder having an iron content of 91% by weight was obtained by dispersing the powder for about 7 hours at a speed of 100% by weight. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOe).

Bo=17800e, (11=73.Oumu/
fσ, = 146 emu/f +σr/σ8=
0.50 Example-8 The average major axis length is 0.3 μm and the average minor axis length is 0.0
2 μm salivary lead-doped needles a-Fe0OH (Zn/Fe
= 1 section) 80t to 6! Suspend in water and disperse with a stirrer. To this were added 180 cc of cobal chloride IM/7 solution and 9 occ of manganese chloride 1 M/J solution, and the mixture was stirred. After that, 270 cc of 2N-NaOH was added, stirred for about 30 minutes after the addition, filtered and washed, and wet α-FθOOH
get cake. This is dried overnight at a temperature of about 150°C. Take 10r of this dry cake and heat it at 550°C with a hydrogen flow rate of 5
A ferromagnetic powder having an iron content of 77% by weight was obtained by spinning at a rate of 7/min for about 7 hours. The magnetic properties of the obtained magnetic powder are as follows (values measured by IQKOe).

H(B = 2050 oe, (7
y = 68.9emu/Fσ, = 150
emu/f, σr/σ8 = 0.55 Example-9 The average major axis length is 1.1 μm and the average minor axis length is 0.0
8 μm acicular a-Fe2O380f 6! Suspend in water and disperse with a stirrer. Nickel chloride 1/! 50cc of solution and 1M of zinc chloride/! Add 30 cc of solution and stir. After that, 80 cc of 2N-NaOH was added, and after the addition, the mixture was stirred for about 50 minutes, filtered and washed, and the wet α-
Fe20. get cake. This is dried overnight at a temperature of about 150°C.

Take this dry cake at 10F and heat it to 350℃ with a hydrogen flow rate of 5!
/min for about 7 hours to obtain ferromagnetic powder with an iron content of 93% by weight. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOe).

Ho=168008 r (II=71, Oe
mu/'σ, = 148 θmu/f, σr/σ,
= 0.48 Comparison Rely 1 The average major axis length is 0.1 μm and the average minor axis length is 0.0
80t of acicular a-Fe0OH with a diameter of 2 μm is suspended in 6 μm of water and dispersed with a stirrer. 45 cc of IM/A solution (cobal chloride) is added to this and stirred. 2 N- for its excellence
Add 45 cc of NaOH7, stir for about 30 minutes after addition, and filter and wash to obtain a wet α-FeOOH cake. This is dried overnight at a temperature of about 150°C. This dried cake 1
Take 0F and hydrogen flow rate is 5 at 350℃! A ferromagnetic powder with an iron content of 95% was obtained by centrifugation for about 7 hours at a speed of 100%. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOe).

Ho= 13200e, a, -= 64,6
emu/f6B = 170 emu/f I (l
iiroe = 0.5B Comparative Example-2 The average major axis length is 3.0 μm and ? Average short axis length is 0.1
Suspend 80t of 3 μm needles (z -Fe0OH in 6! of water and disperse with a stirrer. Contain chloride IM/
Add 7 solution ascc and stir. 2 N for that excellence
-NaOH45co is added, stirred for about 30 minutes after addition, and filtered and washed to obtain a wet α-FθOOH cake. The turtle is dried overnight at a temperature of approximately 150°C. Take this dry cake at 10F and heat it at 550℃ for about 7 hours at a hydrogen flow rate sp of 1 minute (
A ferromagnetic powder with an iron content of 95% by weight was obtained by reduction. The magnetic properties of the obtained magnetic powder are as follows (10KOe
).

Ho = 1180 Oe, (1r ” 7
5,5 emu/fσg = 175 emu/r
, σr/σ, = 0.43 Comparative Example-3 The average major axis length is 1.0 μm and the average minor axis length is 0.0
3μm needle-like a-Pe0OH80t 6! of water and disperse with a stirrer. In this, konol chloride) IM/J
270 cc of solution and 1 opening of nickel chloride/! solution 450
Add cc and stir. 2 N −Na for its excellence
Add 720 cc of OH, stir for about 50 minutes after addition, and filter and wash to obtain a wet α-FθOOH cake. This is dried overnight at a temperature of about 150°C.

Take 10f and i of this dry cake and heat it at 550°C with a hydrogen flow rate of 3
! /min for about 7 hours to obtain ferromagnetic powder with an iron content of 57 weight range. The magnetic properties of the obtained magnetic powder are as follows (values measured by IQKOe).

Hc = 8300e, σ1 == 55,4 em
u/rσ, = 154θmu/l, σr/dB ” O
j6 Comparative Example-4 The average major axis length is 0.1 μm and the average minor axis length is 0.0
2 μm needle a -Fe0OH8Q t 6! Suspend in water and disperse with a stirrer. Add nickel chloride to this /
! Add to 540 cc of solution and stir. Add 540 cc of 2N-NaOH to the well, and after adding about 3
After stirring for 0 minutes, the mixture is filtered and washed to obtain a wet α-FeOOH cake. This is dried overnight at a temperature of about 150°C. Take this dry cake at 10F and heat it to 350℃ with hydrogen flow f5! A ferromagnetic powder with an iron content of 63 times was obtained by centrifugation for about 7 hours at a speed of 100%. The magnetic percent strength of the obtained magnetic powder is as follows (I
Measured value at QKOe).

He = 4500e, ar = 56+B
emu/fσE! : 105 emu/r, ar
/aB = Oj5 Comparative Example-5 The average major axis length is 1.2 μm and the average minor axis length is 0.0
4 μm needle-like a-Fe0OH80t 6! of water and disperse with a stirrer. Add nickel chloride to this /
! Add 540 cc of solution and stir. That excellence 2
Add 540 cc of N-NaOH, stir for about 30 minutes after addition, and filter and wash to obtain a wet α-Fe OOH cake. This is dried overnight at a temperature of about 150°C. Take this dry cake at 10F and heat it to 350℃ with a hydrogen flow rate of 3! /min for about 7 hours to obtain ferromagnetic powder with an iron content of 63% by weight. The magnetic properties of the obtained magnetic powder are as follows (10
(measured value at ○θ).

HQ =4800ee (71=58, 18mu/'
σEl = 112 emu/r, σr/σ6=0.
34 Comparative Example-6 The average major axis length is 0.8 μm and the average minor axis length is 0.0
3μm needle α-F, OOH80f 6! Suspend in water and disperse with a stirrer. To this, zinc chloride 1M/7 solution 54
Add 0 cc and stir. Then another 2 N -N
Add 540 cc of aOH, stir for about 50 minutes after addition, and filter and wash to obtain a wet α-FθOOH cake. This is dried overnight at a temperature of about 150°C. This dried cake IQ
Take f and hydrogen flow rate is 3 at 350℃! A ferromagnetic powder having an iron content of 64% by weight was obtained by dispersing the powder at a speed of about 7 hours. The magnetic properties of the obtained magnetic powder are as follows (measured values at 10 KOe).

Hc=5200e t σj ”' 25. Oemu/
fσ day = 78 emu/r, σr/σ8 = 0.
32 Comparative Example-7 The average major axis length is 1.2 μm and the average minor axis length is 0.0
4 μm needle-like a-Fe0OH10t at 350℃ and hydrogen flow rate 5! /min for about 7 hours to obtain ferromagnetic powder with an iron content of 100%. The magnetic properties of the obtained magnetic powder are as follows (measured value of 10 KOe″r).

Claims (1)

[Claims] The average major axis length is 0.2 to 2 μm, and the average minor axis length is 0.01 to 0.1 μm. One or more compounds selected from Co, Ni, Mn, and Zn compounds are attached to iron oxyhydroxide, iron oxide, or these doped with metals such as Co, Ni, Mn, and Zn. , adsorption, or precipitation, the treated product is dried, and then treated in a reducing gas atmosphere for 2 hours.
1. A method for producing magnetic powder for magnetic recording which has a coercive force of 16,000 θ or more and contains iron in an amount of 70 to 98% by weight, the method comprising reducing the powder at a temperature of 00 to 600°C.