JPS6265307A - Manufacture of magnetic iron powder - Google Patents

Abstract

PURPOSE:To contrive improvement in the efficiency of a tape by giving a high orientational property and a high filling adaptability by a method wherein iron oxyhydroxide is formed into the Geothite containing the two components of Al and P as a coprecipitated component. CONSTITUTION:When magnetic iron powder is formed by performing a reduction by heating after a magnetically regulated component and/or a configulation retaining component are coated on the surface of grains of washed iron oxyhydroxide, iron oxyhydroxide is formed into the Geothite containing two components of Al and P. A kind or two or more kinds of an oxide, a hydroxide, a nitrate and a carbonate, corresponding to each element of Ni, Cu, Co and Zn, are combined and used as the magnetically regulated component. A kind or two or more kinds of an oxide, a hydroxide, a nitrate and a carbonate, corresponding to each element of P, Si, Al, b, Cr, Mn and Ti, are combined and used as a configulation retaining component.

Description

[Detailed description of the invention] The present invention relates to a method for producing magnetic iron powder for magnetic recording.

In magnetic recording, there is a strong trend toward higher density, and the requirements for magnetic materials are becoming increasingly strict in response to this trend. 8II
l To give an overview of video applications, magnetic tape continues to be improved to increase output and reduce noise.As for magnetic powder, due to the requirement of high σS, unlike conventional iron oxide-based magnetic powder, so-called so-called high reduction degree magnetic powder is used. Magnetic iron powder is used.

Magnetic iron powder is generally produced by a method of heating and reducing acicular iron oxyhydroxide. An overview of known methods is as follows.

It is known that the properties of iron oxyhydroxide, which is the starting material for magnetic iron powder, have a great effect on the performance of magnetic iron powder.

In other words, in order to produce high-performance magnetic iron powder, it is desirable to reduce the particle size distribution of the acicular iron oxyhydroxide, which is the starting material, to eliminate branch crystals and to have an appropriate acicular ratio. is being carried out.

Acicular iron oxyhydroxide undergoes an alkali neutralization reaction with an aqueous ferrous salt solution, and has a pH of 60
It can be obtained by air oxidation at a concentration below °C. In this case, Ni, Go.

Zn, Mn, Cr, AI, P, Ti, Si
, Go, Sn 1Ca 1Mg, Bi, etc. are added during the neutralization reaction between the ferrous salt and the alkali, and the pH is adjusted to 1.
Empty% I at a temperature below 60℃ in an alkaline region of 2 or more
Convert 't 6 Koto Ic Yori, Ni, Go, Zn
N Mn %Cr, AI, P, Ti, Si
, Ge, 3n, Ca, Mg, Bi, etc. as co-precipitated components.Acicular iron oxyhydroxide can be obtained.

If the solution is acidic, the soluble aqueous solution corresponding to the coprecipitated component may be used by mixing it with a ferrous base aqueous solution, or it may be neutralized with an alkali before the neutralization reaction between the ferrous salt and the alkali. After that, the ferrous salt may be added. Alternatively, it may be added after the neutralization reaction between the ferrous salt and the alkali. If the soluble aqueous solution corresponding to the coprecipitated component is alkaline, it may be used by mixing the ferrous salt with an alkali to neutralize it, or it may be added to simulate the neutralization reaction between the ferrous salt and the alkali. Also good. In short, it is sufficient to add the coprecipitated component before air oxidation.

It is known that the particle size and acicular ratio of acicular iron oxyhydroxide can generally be adjusted by introducing a co-precipitation component. Furthermore, a method for producing coprecipitated iron oxyhydroxide is also known, which reduces the formation of branch crystals of acicular iron oxyhydroxide, which adversely affects filling properties and orientation.

Furthermore, a method for producing coprecipitated iron oxyhydroxide is also known in which the particle size distribution of acicular iron oxyhydroxide is narrowed by introducing a coprecipitated component.

Specific examples of these known techniques include JP-A No. 56-3605 regarding CO coprecipitation and JP-A No. 56-23201 regarding ZN coprecipitation. JP 56-23202 on Co, Zn, Si heavy coprecipitation; JP 56-169132 on Mg coprecipitation; JP 53-Showa 53 on Si coprecipitation.
75199, JP-A-47 on AI, Ge, Sn co-precipitation
-30477, AI, JP-A-59 regarding Ni heavy coprecipitation
-19169 etc.

When obtaining magnetic iron powder by thermally reducing needle-shaped iron oxyhydroxide, shape-retaining components and final particles are added to prevent the starting material iron oxyhydroxide from losing its shape or sintering. It is a common practice to deposit a component that adjusts the magnetic properties of the magnetic iron powder obtained in the above process onto the surface of iron oxyhydroxide before thermal reduction of the iron oxyhydroxide. Shape-retaining components include P, Si, AI, B, Cr,
Ti.

Oxides such as Mn, hydroxides, nitrates, carbonates, etc. are used. In addition, the magnetic adjustment components include Ni, Cu,
Oxides, hydroxides, nitrates, carbonates, etc. of Co, Zn, etc. are used. Methods for depositing these compounds on the surface of iron oxyhydroxide include a method in which iron oxyhydroxide is made into a water-containing paste using a soaking machine or the like, and the above-mentioned adhesion components are added and mixed; A method in which iron oxide is made into a slurry, a water-soluble salt as an adhering component is added to a similar slurry, and then the water-soluble salt is deposited on the surface of iron oxyhydroxide by adjusting H with caustic soda or acid, or both. Methods that combine the two are known.

Next, we will discuss the thermal reduction treatment of iron oxyhydroxide or iron oxyhydroxide that has been subjected to adhesion treatment. Direct reduction with C may be used, but iron oxyhydroxide or iron oxyhydroxide which has been subjected to adhesion treatment in a non-reducing atmosphere before reduction with hydrogen can be reduced to 300 to 9
A method of firing at 00° C. to form an oxide containing α-Fe 203 as a main component and then reducing it using hydrogen at 300 to 500° C. is preferable because it is easy to obtain fired magnetic iron powder.

In order to meet the demand for increased tape output, magnetic iron powder is required to have high orientation and filling properties, that is, powder that provides a high Br /Bm value of 5r (l) when made into a tape. In addition, in response to the demand for low-noise tapes, there is also a demand for finer magnetic iron powder.If this is expressed in terms of the specific surface area of magnetic iron powder, the current commercially available 81 tapes have a surface area of approximately 501/(l). However, due to the demand for low noise, a fine magnetic iron powder of 60i + 10 is desired.Furthermore, in order to reduce noise, it is not enough to make it fine. Instead, the magnetic layer of the tape must be filled with finely divided magnetic iron powder to a high degree of filling.

As mentioned above, imparting high orientation and high filling properties to magnetic iron powder are extremely important characteristics for improving tape performance.

With this background in mind, the present inventors conducted intensive studies to obtain high-performance (magnetic iron powder), and as a result, the present invention was completed.

According to the present invention, iron oxyhydroxide is added to the surface of washed iron oxyhydroxide in a method for producing magnetic iron powder, in which a magnetic adjustment component and/or a shape-retaining component are added to the surface of washed iron oxyhydroxide. A method of reporting magnetic iron powder is provided, which is characterized by two components of Al and P (gut bisite contained as coprecipitated components).

Magnetic adjustment components include Ni, Cu, and Go.

It is sufficient to use one type or a combination of two or more of oxides, hydroxides, nitrates, and carbonates corresponding to each element of zn, and as a shape-retaining component, P % S + x
One or more combinations of oxides, hydroxides, nitrates, and carbonates corresponding to the σ elements of Al, BsCr, and MnsTi may be used.

The present inventors previously disclosed in JP-A-56-114833 (Reporting method of ferromagnetic iron compound fine particles) that fine acicular oxyhydroxide iron fine particles containing AI and P elements are an extremely good raw material. The present invention discloses the fact that particle shape damage, destruction, and even sintering hardly occur due to reduction and/or oxidation reactions.

That is, it has been found that the composite component of Al and P has a remarkable shape retention effect during thermal reduction. Furthermore,
The same patent application also discloses the fact that even if Al and P are introduced as coprecipitated substances during the synthesis of acicular iron oxyhydroxide, the shape retention effect during thermal reduction is the same. Regarding this method for synthesizing acicular iron oxyhydroxide co-precipitated with AI and P, in comparison with a known method for synthesizing iron oxyhydroxide that does not use FAI or P-containing compounds, neutralization Set the oxidation reaction 5 to 10℃ higher, and in some cases increase the air supply rate by 20 to 4℃.
The fact is disclosed that iron oxyhydroxide having almost the same particle morphology can be produced by increasing the amount by 0%□.

The present inventors have discovered the Al
The specific surface area of 60
An attempt was made to obtain a fine magnetic iron powder of 1'/iII, but it was discovered that as the particles become finer, it becomes extremely difficult to maintain the shape.

However, the present inventors have discovered that by applying a shape-retaining component to the surface of acicular P and AI co-precipitated iron oxyhydroxide, the starting material, acicular P1Al co-precipitated iron oxyhydroxide, can be heated and reduced. The specific surface area without sintering is 60m, closely inheriting the shape of
It is possible to obtain fine magnetic iron powder of about 10 mm, and IWla
It has been found that the magnetic layer of the tape can be filled with high density iron powder.

The present inventors further investigated iron oxyhydroxide containing no coprecipitated components, P coprecipitated iron oxyhydroxide, Al coprecipitated iron oxyhydroxide, and N1 coprecipitated iron oxyhydroxide as a comparison of P and AI coprecipitated iron oxyhydroxide. A comparison with magnetic iron powder obtained by applying the same shape-retaining component as in the case of P, Al co-precipitated iron oxyhydroxide to precipitated goethite and then reducing it by heating revealed that the filling ability of magnetic iron powder into tape was It has been found that magnetic iron powder made from 1% Al co-precipitated acicular iron oxyhydroxide as a starting material is visually superior to others in terms of orientation and orientation. The reason for this is not necessarily clear, but P.
The fact that the shape retention effect is uniquely excellent due to the combined effect of AI, and the fact that the synthesized P.

It is thought that there is a combined effect such that the Al coprecipitated acicular iron oxyhydroxide has fewer shape factors such as branch crystals that adversely affect the dispersibility.

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

Example 1 (1) Goethite synthesis F13804・7H2050ko and AI (N
Os)s・9H! 02790Q @Wed 10001
The solution temperature was adjusted to 40°C (this is referred to as solution processing). Also, Naot-145kg and (Na P0
s33(2) was dissolved in water 5001, and the liquid temperature was adjusted to 35°C (this is referred to as solution ①).

Prepare the solution in a reactor with an internal volume of 3M3 equipped with a stirrer, then add the solution (1) all at once, stir and mix for 5 minutes to complete the neutralization reaction, and then blow air at a feed rate of 10M''/1ain for 40 minutes. By saponification at ℃, yellow-brown goethite was obtained as precipitated particles.

When the goethite was washed with water, dried, and analyzed, it was found that the axial ratio was 1.
6. The goethite was acicular particles with a specific surface area of 761"/Q, no branch crystals, and uniform particle size.Furthermore, fluorescence xm analysis revealed that the goethite had a weight ratio of AI/Fe-1,9/100, P/ F
It had a composition of e-0.09/100 (the goethite is referred to as Gl).

(2) Adhesion Treatment A slurry 1001 in which Goethite GI was adjusted to a weight ratio of Goethite+Water of 100 was put into a container equipped with a stirrer. After washing: ■Aqueous solution in which 52 g of sodium metaphosphate was dissolved in 11 of water; ■Aqueous solution in which 1.13 klJ of No. 03 water glass stock solution was dissolved in 51 of water; ■Aqueous solution in which 01.57 kg of Nt(NOx>2.6Hξ) was dissolved in 51 of water. , 01M4 constant NaOH aqueous solution 1. and ■1MA constant H
An NOs aqueous solution was prepared, and to the above slurry, first, (1) was added, and then (2) and (2) were added simultaneously over 1 hour each. When adding (2) and (2), (2) was added as appropriate so that the pH of the solution did not fall below 8.

Finally, the l)H of the slurry was adjusted to 8 using (1) or (2), and then the slurry was washed with water and dried.

When a part of the dry powder was separated and analyzed, the adhering powder had a weight ratio of Ni/Fe-9,5/100, P/Fe-0,
45/100. Si/Fe-4,7/100, AI
/Fe-1,9/100.

(3) Calcining/reduction treatment The adhered powder obtained in the above (2) adhesion treatment was pulverized so as to pass through a 16' mesh sieve, and heated to 650°C in air.
The powder was heated and dehydrated for 4 hours to obtain a baked powder.

2.5 ka of this calcined powder was charged into a stirred fluidized bed reactor, and while supplying Hξ at 8ONm'/H, the concentration in the reactor was raised to 400°C and maintained for 3 hours, and then the gas was changed to Nt. It was then cooled down to ambient temperature.

Next, the reduced powder is collected and immersed in toluene, spread on a flat plate, and brought into contact with air to form an oxide film on the surface of the reduced powder and stabilize it. Got 9 on 1.7.

(4) Evaluation of magnetic iron powder [Powder properties] As powder physical properties, magnetic properties, bulk density, and specific surface area were measured and the following values were obtained.

The magnetic properties were measured using a vibrating sample magnetometer (VSM) at a measurement magnetic field of 10 KOe.

Hc1585 0e as 127 emu/Q σ'/σs0.51 Specific surface area 571/J Moreover, when the C concentration in the magnetic iron powder was analyzed, it was found that the weight ratio was C/Fe-0.07/100.

[Measurement of sheet physical properties] 300 parts of magnetic iron powder, VAGH (vinyl hydrochloride polymer, UCC
After stirring and dispersing a mixture of 45 parts (product name), 175 parts of toluene, and 175 parts of methyl isobutyl ketone in a ball mill for 24 hours,
7 (Urethane prepolymer, Narita Pharmaceutical product name) 2 parts,
15 parts of toluene and 15 parts of methyl in butyl ketone were added to a ball mill and stirred and dispersed for 1 hour to prepare a magnetic coating material.

The obtained magnetic paint was applied to a polyester film with a thickness of 16 μm to a dry thickness of 3 μl, the metal powder was oriented in a magnetic field, and then dried. Then, the surface of the magnetic layer was calendered to give it an iron surface. The sample was then cut to a predetermined width to obtain a specimen.

The sample was measured with a VSM at a measurement magnetic field of 10 KOe to obtain the following sheet properties.

Hc1470 Qe Br2340 Gauss Sr /8m 0.77 Example 2 (1) Goethite synthesis Fe SO4.7H2050ko was dissolved in 10,001 parts of water, and the liquid temperature was adjusted to 40° C. This was used as solution (2).

Also, Na0845k(J, (NaPOs >466g
and 600g of sodium aluminate dissolved in 8001 of water,
The temperature of the solution was adjusted to 35°C (this will be referred to as solution ①).

Prepare the solution (■) in a reactor with an internal volume of 3M' equipped with a stirrer, then add the solution (■) all at once, and let it stand for 5 minutes! After the neutralization reaction was completed by Zen mixing, air was blown in at a feed rate of 10 M'/sin and oxidation was carried out at 40°C to obtain yellowish brown goethite as precipitated particles.

When the similar goethite was washed with water, dried, and a portion was separated and analyzed, it was found to be acicular particles with an axial ratio of 15, a specific surface area of 78n+''/9, no branch crystals, and a uniform particle size. Linear analysis revealed that the goethite had a weight ratio of AI/Fe-1,9
/100. The composition was P/Fe-0.16/100 (the goethite is referred to as GM).

(2) Adhesion Treatment Goethite of Gn was subjected to an adhesion treatment under the same conditions as the adhesion treatment described in (2) of Example 1 to obtain an adherend. The composition of the adherend is Ni/Fe-9,6/100 in weight ratio;
P/Fe-0,58/100,Si/)”e-4,9
/100SAI /Fe-1°9/100.

(3) Firing/Reduction Treatment Under the same conditions as the firing/reduction treatment described in (3) of Example 1, about 1.7 kg of magnetic iron powder was obtained.

(4) Evaluation of magnetic iron powder [powder properties] Powder properties were measured under the same conditions as in Example 1,
1590 0e σS 122 emu/.

σr/σso, 50 Specific surface area 58 1/(1 I got it.

[Measurement of sheet physical properties] The sheet properties were measured under the same conditions as in Example 1, HCl490 0e 8r2300 Gauss Sr　/Bi　0.76 I got it.

Comparative Example 1 Magnetic iron powder was obtained in the same manner as in Example 1 except that (2) deposition treatment and (3) firing in Example 1 were omitted.

The powder characteristics of the magnetic iron powder are: HCl380 Qe σS 126 emu/Q σr/σS0.45 Specific surface area 44m”/a and the sheet properties are Hc1310 0e 8r1520 Gauss Br　/Bu　0.66 Met.

Comparative Example 2 (1) 0501 g of goethite synthesis Fe SO4.7Ht was dissolved in 10001 g of water, and the liquid temperature was adjusted to 35°C (this is referred to as Solution I).
. In addition, 45 ml of NaOH was dissolved in 500 ml of water, and the solution temperature was adjusted to 35° C. (This was used as a solution ①).

Prepare the solution in a reactor with an internal volume of 3 M' equipped with a stirrer, then add solution (1) all at once, stir and mix for 5 minutes (after completing the neutralization reaction, blow air at a feed rate of 12 M'/min). By carrying out oxidation at 35° C., -C was obtained as yellowish brown goonite as precipitated particles.

When the goethite was washed with water, filtered, and a portion of the filter cake was separated and analyzed, it was found that the goethite was acicular particles with an axial ratio of 14 and a specific surface area of 751/g, with branches scattered here and there. The goethite was confirmed to have a large particle size distribution by transmission type microscopic observation, so the goethite was measured as am).

(2) Using Goethite of Adhering Treatment G11l, an adhering powder was obtained under the same conditions as described in (2) of Example 1.

The composition of the MlM powder is Ni/Fe-9,
5/100. P/Fe-0,45/100%Si/F
It was e-4, 8/100.

(3) Firing/reduction treatment Approximately 1.7 kg of magnetic iron powder was obtained by treatment under the same conditions as described in (3) of Example 1.

(4) Evaluation of magnetic iron powder As a result of measurement under the same conditions as in Example 1, the powder properties were Hc1575 0e as 126 emulo σr/σS0.49 Specific surface area 551'10, and the sheet properties were as follows. ic14950e Br2050 Gauss Br/Bm o, 72.

Comparative example 3 1”e 804 ・7Ht 050kg and AI
(NO3)3.9 Ht O2-7909 to 1000% water
1 and adjust the liquid temperature to 35°C (this is called a solution process). In addition, 845 kg of Na was dissolved in 500 ml of water, and the solution temperature was adjusted to 35° C. (This was designated as solution ①). Hereinafter, acicular Al co-precipitated goethite and magnetic iron powder were obtained in the same manner as in Comparative Example 2. A'/Fe = 1.9/100F in II ratio by X-ray analysis
there were.

In addition, the powder physical properties of the magnetic iron powder are as follows: Hc1570 Qe as　123　emulo σr/σS0.49 Specific surface area 541/(+ And the sheet physical properties are Hc1460 0e 8r2020 Qauss Sr　/Bm　0.71 Met.

Comparative example 4 Fe 804 ・7H! 050kg to 1 oool of water
k: Dissolved and adjusted the liquid temperature to 35°C (this was dissolved in solution
). In addition, Na0845kO and (NaPOs
)b Dissolve 331J in water 5001 and heat solution 1 to 35℃
(This is called solution ■). Thereafter, in the same manner as in Comparative Example 2, acicular P coprecipitated goethite and magnetic iron powder were obtained.

! aP co-precipitated goethite has a specific surface area of 701/a and an axial ratio of 1
According to fluorescent X-ray analysis, the weight ratio is P/
The composition was Fe-0.08/100.

In addition, the powder physical properties of the magnetic iron powder are as follows: HQ1560 0e σS 126 emu/g σr/σs0.49 Specific surface area 531/J And the sheet physical properties are Hc1455 0e Br 1980 Gauss Br　/am　0.70 Met.

Comparative Example 5 Fe SO4・782050kO and N! SO4”
Dissolve 0,470 g of 6Hs in 10,001 ml of water and bring the liquid temperature to 35
The temperature was adjusted to ℃ (this will be referred to as solution ■). Also, Na08
45k (dissolve 1 in water 5001, and adjust the liquid temperature to 35°C, make this solution ①). Thereafter, acicular Ni co-precipitated goethite and magnetic iron powder were obtained in the same manner as in Comparative Example 2.

The N1 co-precipitated goethite is an acicular particle with a specific surface area of 77 m2/9 and an axial ratio of 16, and according to fluorescent X-ray analysis, the gravity ratio rN
The composition was i/Fe-1,05/100.

In addition, the powder physical properties of the magnetic iron powder are as follows: Hc1545 0e as　124　emu/g σr/σsO, 50 Specific surface area 551/g And the sheet physical properties are Hc1480 0e Br2040 Gauss Br 1F3III 0. 70 Met.

Claims (1)

[Claims] In a method for producing magnetic iron powder, in which a magnetic adjustment component and/or a shape-retaining component are deposited on the surface of washed iron oxyhydroxide particles, and then heated and reduced, the iron oxyhydroxide is mixed with Al and P.
A method for producing magnetic iron powder, characterized in that the powder is goethite containing two components as co-precipitated components.