JPS58164706A - Production of acicular ferromagnetic iron powder - Google Patents

Abstract

PURPOSE:To produce acicular ferromagnetic iron powder having large coercive force in high satd. magnetization by adding an aq. soln. of water soluble silicate in an aq. suspension of acicular crystal-contg. iron hydroxide and making the same acidic then maintaining the pH constant with a pH buffer and aging the mixture. CONSTITUTION:An aq. soln. of water soluble silicate is added to an aq. suspension prepd. by dispersing acicular crystal-contg. iron hydroxide in 20-100g/l slurry, whereafter a mineral acid is added thereto to make the suspension neutral and acidic. A pH buffer is added thereto and the suspension is held and aged for >=2hr in a 5.1-6.9pH range at 60-100 deg.C. The acicular crystal-contg. iron hydroxide coated with the hydrous silicic acid gel obtd. in the above- mentioned way is dehydrated by heating by a conventional method, whereby the particles of the acicular ferric oxide coated with silicic acid are obtained. The particles are brought into contact with a reducing gas by a conventional method to cause reduction reaction, whereby the acicular ferromagnetic iron powder is produced.

Description

Detailed Description of the Invention This invention-lj1 is a method for producing acicular ferromagnetic iron powder, particularly a method for producing acicular ferromagnetic iron powder, which is a modified method of coating with acicular crystal hydrated iron oxide O hydrated silicon. Regarding.

Needle-like strong III iron powder molded into a treadmill, highly saturated.
It is a superimposed substance that can be used as a magnetic material for magnetic recording medium that can be expected to be used for a large magnetic coercive crab Hc (Eruska, Koki Brass writing).

The general manufacturing method of acicular magnetic iron powder that is currently being produced is as follows: 0) A process of oxidizing raw iron salt in a basic aqueous solution to produce acicular crystalline hydrated iron oxide (1.oon)← ) 0) Step fj of applying silicate etc. to the iron hydroxide obtained in the factory.
By heating and dehydrating Yoshihydroxide iron, ferric oxide (α-11'e,
0. It consists of a factory that reduces the ferric wire (ToIP Town 01) obtained in the step (c) to produce needle iron powder (Fe).

The saturation magnetism and coercive force magnetic properties of the acicular magnetic iron powder depend on its shape anisotropy (acicularity). A major challenge is how to maintain the properties of the target material, acicular magnetic iron powder, through the long embroidery process, especially through the processes of heating dehydration and high-temperature reduction. Many proposals have been made.

In particular, the coating of acicular crystal hydrated iron oxide in step (b) is
) It has been proposed as an indispensable substance for maintaining the acicularity of hydrated iron oxide obtained in the process through heating dehydration and reduction.

Covering with if, sio, ] method is 轡public 11
No. 56-9005, Japanese Patent Application Publication No. 1856-134. i1 publication, tatami-1856-2゜105 publication, and opening/closing ogo 7
No. 793□, Report, etc., ': A method of coating with Mut and B1 compounds is described in Special-1i56-
Publication No. 156706 describes a method of coating with TlO2.
It is described in the 1Hcfh15 method tl*Wla@54-37297 newsletter. The magnetic properties of the magnetic iron powder finally obtained by taking into account the elements of these knee-improving O effects, or the magnetic properties of the magnetic recording medium that is coated with the magnetic iron 11 as a paint. It can be expressed as For example, JP-A-Shoki-1567G6
The M1-containing α-iron oxyhydroxide trunk wheel described in the 18th report was dispersed in sodium silicate and aluminum sulfate mixed water, treated by blowing carbon dioxide gas, washed with water and dried, and placed on a quartz plate with hydrogen gas. The magnetic properties of the magnetic iron powder obtained by reducing the magnetic iron powder by contacting it at a temperature of 4(x)°C are as follows: saturation magnetization: a@-148~1!
$4 Coercive force at reduction rate of @1nlh/f; IC■
11gG -1315 Oersted, and square ratio Jr/
Js -0.48 to 0.51. Generally B8 a
150・mu/f O 1 to #I&-I saturation magnetization can be easily achieved by performing the reduction in t minutes), but at the same time, large retention, cuff t & □shi: -1400xtvx f
y Y tlllltf h t is full of 1a Kinka: Js$
1, while coercive force; H
On the contrary, C often shows a decreasing tendency, and it is extremely difficult to
It is rare to find a document describing Js≧150・mu/y, Ha≧1400 Oersted O11mIIEFC110, and the method described in the scissors document involves an extremely complicated process, making it unsuitable for use as an industrial manufacturing method. It's a roar.

The purpose of this invention is to provide an industrial method for producing acicular iron powder having a large coercive force at a high saturation magnetization and a high saturation magnetization.

As a result of intensive research to achieve the above object, the inventor, Hiromu,
Coating reaction of acicular crystalline hydrated iron oxide with hydrated silicate glue
! By adding a buffering agent j) By maintaining the pig within a certain range and aging it in a coating solution], the needle-like nature of the acicular crystal hydrated iron oxide is reduced to needles obtained through a heating dehydration and reduction factory. We completed this book by discovering that a good coating that could be maintained with magnetic iron of 11Kt could be obtained.

The present invention is based on the acicular magnetic iron 5osaat method, which consists of coating acicular hydrated iron oxide, heating dehydration, and reduction. There,
Acicular crystal hydrated iron oxide in water at 20 f/l to 100 f/l
To the suspension, water-soluble silica salt O water ini was added, and then mineral acid was added to neutralize and acidify. After that, hydrogen ion l was added to the slurry at 11 degrees Celsius, and the mixture was heated at 0°C. At a temperature of 5.1 to 6.90 at a temperature of 1 to 100°C
This is a method for producing acicular ferromagnetic iron powder, which is characterized in that acicular ferromagnetic iron powder is coated with hydrous silicate glue on iron hydroxide in axillary acicular crystals by holding and aging for 2 hours or more.

At Motoya@i, we are producing acicular hydrated iron oxide (i・0
0H) is substantially acicular, preferably with an axial ratio (major axis/minor axis) of 5 to 1, and a major axis length of 0.3 μm to 2.0 μm. Oll
wa's a-telon, β-? eOOH, and r
-Pe0OH () alone, 19 is a mixture of two or more types, and there are no restrictions on the manufacturing method. For example, N1, C01
Even if it is manufactured using a system in which metals other than # such as Or, Zn, and # are added, it is acceptable as long as it is recognized that 1.OOH is the main component. Water-soluble silicate, which is one of the raw materials, is a silicate that is submersible in water. Anything that generates guru is fine,
For example, sodium metasilicate, sodium sesquisilicate, No. 1 to No. 3 water glass, etc. can be used. Hydrogen ion 111 degree buffer has p115.1 to 6.94 DI
For example, acetic acid-sodium acetate system, phthalate@1sodium-7thal@disodium system, phosphorus@2water volume sodium-disodium hydrogen phosphate system can be used. .

In the present invention, acicular crystal hydrated iron oxide is used to form 7OII.
Adhering water-soluble solids, such as sodium sulfate and sodium hydroxide*, are removed by washing with water and then dispersed in water. Dispersion in water is carried out by applying sufficient stirring power to prevent the individual scissor-like crystalline iron hydroxide particles from agglomerating, but a dispersant is used to improve dispersibility in water: □ 1
'L is an anionic or nonionic surfactant.
(is 4 lyrin salts, such as FF thorium trilyphosphate, potassium birophosphate, hexametallic acid''-sodium, etc.)
It is preferable to add the kernels to the water in advance so that the temperature becomes t7t. Dispersion of acicular crystal hydrated iron oxide in water11m
Although it depends on the type and capacity of the stirring device used, whether or not a dispersant is used, and the type of 111i, it is preferably 20 f/l to 100 f/l. When the scissor-acicular crystal iron hydroxide is reduced to acicular ferromagnetic iron powder in the ζO needle-shaped ice hydroxide iron hydroxide suspension, 0 .6 to 9 weight - 1 preferably 2 to 6 weight - 810. Pre-distributed castable silicate is added as water** in an amount such that a l1lI11 solution can be formed. Specifically, the iron content in the iron hydroxide in the axillary needle crystals is 810.8%, assuming that 90% of the added water-soluble silicate is coated. 1 to 10 parts by weight of a water-soluble silicate is added as water to the suspension of acicular hydrous iron oxide. If the amount of silicate added is too small, a coating film that can withstand high temperatures will not be formed, and if too much silicate is added, the saturation magnetization of the iron powder obtained after reduction may not reach the target. be. Then, a dilute solution of 2 to 8 N, such as sulfuric acid or hydrochloric acid, is added to this suspension to neutralize and acidify it so that the final hydrogen ion concentration becomes pns, i~6.9. 11. To form a hydrous silica and then maintain the above pH range, add the hydrogen ion concentration slowing agent and heat at a temperature of 100° C. to 100° C. for 2 hours or more, preferably 11. < is 2
By aging for several hours, the acicular crystal hydrated iron oxide can maintain its acicular properties even through heat dehydration and high temperature reduction.
When using IJun Shunshio) 115.5. T-Ishi 6
．． Use a salt-based buffer that is adjusted to □ so that it is 4.
It is preferable to It is known that the gluing rate of silicic acid hydrogen ion 11m force PH 7.0 vs. Since mutual aggregation is likely to occur, it is preferable to use less than avh, and the gluing rate is too slow to provide a good coating.

In the present invention, the 9-hydrated silicate-covered acicular ferric oxide obtained by the 07F method is heated and dehydrated (by a conventional method) to produce a silica-coated acicular ferric oxide ( α-ye, os)
The target acicular ferromagnetic iron powder is obtained by contact-electrifying the particles and a reducing gas under 1iLK at a temperature of 350°C to 500°C to carry out a reduction reaction. Manufacture.

Motoya provides a method for producing acicular ferromagnetic iron powder, which is an improved method for producing acicular ferromagnetic iron powder using acicular crystal hydrated iron silicic acid glue. As a result, a stable coating can be obtained that can maintain the acicularity of the acicular hydrated iron oxide even through the steps of heating dehydration and reduction, and by operating each step with a favorable exciter) , saturation magnetization; δ'
Holding power at 41'50emu/f; HC≧14
This is a method for obtaining 00 Oersted needle-like strong steel 1#O.

The present invention provides a method for manufacturing needle-shaped and perpendicular iron plates that can obtain a large coercive force in the production of high-grade steel plates, and is therefore of great significance.

Hereinafter, zero** will be explained in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 17 Obtained by ordinary method, nine average major axis 140 μ solution, average minor axis 0.05
11tm of acicular hydrated iron oxide (α-ν・00H1 hereinafter referred to as goethite) 2.214 was mixed with 504Kll of ion-exchanged water.
1I, add hexamethalin sodium chloride f as a dispersant, connect directly to 2@ induction motor, and make 9500%
Disperse for 0 minutes using a high-speed stirrer. Keep the liquid temperature at 1°C.
Flooding! 5, Ic (36,51s810.)
176F was dissolved in 140 ion-exchanged water and added, and the mixture was further stirred at 140°C for 1 hour. After this 411.1104
Neutralize to 111M to 6.3 and use 0.3M/L glue/acid 2water volume 1p aqueous solution 2t as a pH buffer for aging.
and 1 t of 0.3 M/l phosphorus disodium hydrogen water #I solution
added. The pH should be 6.0.

After aging at lead temperature for 3 hours, after death, P was removed using a filter press, washed with water, and further dried at 130°C.

The nine-coated goethite thus obtained is yxaG12
Quantitative silicon O analysis was performed by the method described in No. 12, and the iron content was 3.1% by weight, -0810%, and the coating was found to be 3.1% by weight. Also, this received 1Nr-Thai: Oath 1. □: When observed with an electron microscope, the dispersion state was good, and there were no tongs coated or agglomerated r-tite particles observed.

Furthermore, as a result of shadowing this coated goethite using a chromium vapor deposition method and observing it with an electronic microscope, it was found that #10. The chest was observed and it was found to be uniformly coated with a certain amount of dirt. This coated goethite 2.3k is SO
Dehydrated by heating at 0°C for 2 hours to obtain 810% coated hematite (hereinafter referred to as coated hematite). ζ011111 Matite with an electronic mirror! *As a result, the shape and dimensions of r-tight were maintained, and the particles were well dispersed without sintering. The obtained nine hematite is ■3
Reduced at 430°C under circulation, constant magnetic field l, saturation magnetization a8 = 155 mu/f in KOe, Hoki Kani H
a: 1480 Oersted squareness ratio; Jr/Js -0,
Obtained 530 Kisei Tetsuken.

When this iron powder was observed with an electron microscope, the average long axis was 0.5.
It has an acicular shape with a pm average minor axis of 0.03 IIs, and no baked koji is seen between the particles, and the iron particles in the coated cylinder are solid powder with little O remaining during the collapse of the shaft. It was. ・Mountain 11.(,.

Example 2. ) N1 produced according to the method of @55-23773 was mixed with 4 atoms (vs. ν atoms) and zntlJIA (vs. Pe).
average long axis 1.27 m average short axis 0.05
88 tons of 11 m of acicular hydrated iron oxide (gutai) were melted into distilled water, 0.5 f of potassium pyrophosphorus was added, and the mixture was thoroughly dispersed with stirring. (Capital) Bunki K1 Mizuga 9 X
(36-51$810*) 3.6 t t2Dm
The mixture was dissolved in distilled water and added to the mixture, heated to a temperature of about 100°C and stirred.

Hi 11 continuation @ 4M M, 804 water S* is placed in a basket with stirring, neutralized to a pH of only 6.6, and then 0-3 M/L 11gPO
4@ilE in advance SeaMail #Isuku pli 6
．． Produced by neutralizing to 0, adding 120-p buffer
It was aged for 3 hours at H6.4K.

This solution was left to stand overnight, washed briefly, and dried at 130°C to obtain a lIr-tight coating.The amount of coating was 91.
I was disappointed with the true weight of 7.

This 1r-tite was heated and dehydrated at 500°C to obtain matite, which was then reduced using H gas at 430°C to obtain magnetic iron powder.

The magnetic properties of this iron powder are -■168・Hoult% 卯■
1410 Oersted jr / Ja -0-51 (a
It was ll fixed place l o Kiroersted).

Comparative Example 1゜Using the same r-tite as in Example 1, without adding a buffering agent for ripening, and adding 41 if, 1104 from time to time during the 3 hour ripening period, The ar-tight T
lI9.

The results of quantitative analysis of silicon O were 3.2 weight - 810° and 411 (iron weight), which was hardly different from Example 1 (9).

As a result of observation with the electron mold 11i11, even though the speculum surface was sufficiently elevated and dispersed in an ultrasonic dispersion tank, the dispersion state was poor. was watched and mourned. According to the results of chrome shadowing, 69 irregularities were observed on the goethite-covered surface, and in one case, 60 inorganic spots were observed, and monosilicate glue lumps that were not caused by the goethite were scattered within the field of view.

Get this one! The magnetic properties of the iron powder obtained by heating, dehydrating and reducing in the same manner as in Example 1 were Ja-158emu/fBO.
ym 12IOx k Sf I' square ratio arlam
When the iron powder of -0.51 (glue jg-field l♂Oersted) was observed with an electronic mirror, it was found that there was a lot of sintering between the particles and there was collapse in the shaft, and it was recognized as defective.

Applicant: Nippon Soda Co., Ltd. Agent Haruyuki Ito

Claims (1)

[Claims] 1. Hydrous silicon of acicular crystal hydrate iron oxide @l”k model,
In the production method of acicular strong image test consisting of heating dehydration and reduction, 20 f/l of acicular crystal hydrated iron oxide is added to water.
L 1G0 f/lO sv-@directly dispersed as
Add 0 water and salt to Ni, then add mineral acid to neutralize and acidify, add 9 bags of hydrogen ion equipment buffer, and boil at 1/% L at 100℃. under temperature]
i5.1 M L 6J O Holds for more than 2 hours S*
p1 The needle crystal meeting water steel iron 0 meeting water Kei IRP
Needle-like 1lI characterized by a kernel coated with kpc
l-Method for producing iron powder. 2. The method described in the patent claim O@ajlll [wherein the water bulk ion@degree buffering agent is a vunshun-based buffering agent. 3. Kall dispersing acicular crystalline hydrated iron oxide in water, and a reasonable request for adding f-lyphosphate to water as a dispersant.
The method according to item 11.