JPH0471014B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing plate-shaped Ba ferrite fine particle powder for magnetic recording.
Ba ion and Ti () and divalent metal ion M ()
By adding glycerin in advance to an alkaline iron hydroxide () suspension containing at least Co() as a metal and performing hydrothermal treatment, plate-like BaO・n{(Fe _{1 -xy}
Ti _x M _y ) ₂ O ₃ } (However, x≦0.1 y≦0.1 4≦n≦6) The purpose is to obtain fine particle powder.

[Conventional technology]

In recent years, ferromagnetic non-acicular particles with suitable coercive force (Hc) and large magnetization value and good dispersibility have been desired as magnetic materials for recording, especially magnetic materials for perpendicular magnetic recording.

Generally, Ba ferrite particles are well known as ferromagnetic non-acicular particles.

Traditionally, as one of the manufacturing methods of Ba ferrite,
A method is known in which an alkaline suspension containing Ba ions and Fe() is hydrothermally treated using an autoclave as a reaction device (hereinafter, this is simply referred to as a hydrothermal treatment method).

First, the powder properties of the plate-shaped Ba ferrite fine particle powder for magnetic recording need to have improved dispersibility when made into a coating. (ratio of the average diameter of the C-plane to the thickness in the C-axis direction).

Next, regarding magnetic properties, the coercive force of plate-shaped Ba ferrite fine particle powder for magnetic recording is generally
About 300 to 1000 Oe is required, and in order to reduce the coercive force of the Ba ferrite fine particle powder produced in the above hydrothermal treatment method and achieve an appropriate coercive force, a part of the Fe () in the ferrite is replaced with Ti () and Co
() or Ti (), Co () and 2 such as Mn, Zn, etc.
It has been proposed to replace it with a valent metal ion M().

In addition, the magnetization value needs to be as large as possible, and this fact is reflected in, for example, JP-A No. 56-149328, which states, Magnetization... is required.''

[Problem that the invention seeks to solve]

Plate-shaped Ba ferrite fine particles with appropriate coercive force and excellent dispersibility are currently in high demand.As for coercive force, as mentioned above, Fe in ferrite is
Part of () is Ti() and Co() or Ti()
Appropriate coercive force can be achieved by substituting divalent metal ions M() such as Mn and Zn. Since the average diameter and thickness of the
It was difficult to obtain Ba ferrite fine particles.

Therefore, there is a strong demand for establishing a method for freely controlling the thickness of the plate-shaped Ba ferrite fine particles produced according to the average diameter.

[Means for solving problems]

The present inventor has arrived at the present invention as a result of various studies in order to easily obtain a plate-shaped Ba ferrite fine particle powder having an appropriate coercive force and excellent dispersibility.

That is, the present invention provides an alkaline iron hydroxide () suspension containing Ba ions, Ti (), and at least Co () as the divalent metal ion M ().
hydrothermally treated in a temperature range of 330°C, or
In the method for producing plate-shaped Ba ferrite fine particles powder by subsequent heat treatment, Fe () is added to the above alkaline iron hydroxide () suspension in advance.
By adding glycerin at a predetermined molar ratio within the range of 0.01 to 0.60 to
BaO・n {(Fe _1-xy Ti _x M _y ) ₂ O ₃ } (However, x≦0.1
y≦0.1 4≦n≦6) This is a method for producing plate-shaped Ba ferrite fine particles for magnetic recording, which comprises obtaining fine particles or then heat-treating the fine particles at a temperature of 900° C. or lower.

[Effect]

First, the most important point in the present invention is that an alkaline iron hydroxide () suspension containing Ba ions, Ti (), and at least Co () as the divalent metal ion M () is heated in a temperature range of 150 to 330°C. In the method for producing plate-shaped Ba ferrite fine particles by hydrothermal treatment, glycerin is added to the alkaline iron hydroxide () suspension in advance in a predetermined molar ratio of Fe () within the range of 0.01 to 0.60. When added, BaO・n {(Fe _1-xy Ti _x M _y ) ₂ O ₃ } is generated depending on the addition ratio of glycerin.
(However, x≦0.1 y≦0.1 4≦n≦6) The thickness of the fine particles can be freely controlled.

The following is an explanation of some of the many experimental examples conducted by the present inventor.

First, Figure 1 shows the addition ratio of glycerin and the plate-like BaO 4.8 {(Fe _0.854 Co _0.073
Ti _0.073 ) ₂ O ₃ } This shows the relationship with the value of D ₁₁₄ as a representative value of the thickness of fine particles measured by X-ray diffraction method.

As is clear from FIG. 1, the thickness of the particles tends to increase as the addition ratio of glycerin increases.

In addition, in the present invention, the plate-shaped Ba ferrite particle powder produced from the aqueous solution has a magnetization value of at most
Although the magnetization value is approximately 38 emu/g, the magnetization value can be further improved by heat-treating the particles at a temperature of 900° C. or lower.

Next, various conditions for carrying out the method of the present invention will be described.

The Fe() salt in the present invention includes iron nitrate,
Iron chloride etc. can be used.

As Ti() in the present invention, titanium chloride, titanium oxysulfate, and alkali titanium can be used.

The divalent metal ion M in the present invention is Co
() or Co() and Mn() other than Co(), Zn
() etc., and chlorides and nitrates of these divalent metals can be used.

As Ba ions in the present invention, barium hydroxide, barium chloride, and barium nitrate can be used.

The hydrothermal treatment temperature in the present invention is 150°C to 330°C.
It is.

If the temperature is less than 150°C, it is difficult to generate plate-like ferrite particles.

Although it is possible to generate plate-shaped Ba ferrite particles at temperatures exceeding 330°C, the upper limit of the temperature is 330°C when considering equipment safety.

The amount of glycerin added in the present invention is Fe
The molar ratio to ( ) is 0.01 to 0.60.

If it is less than 0.01, the effect of controlling the particle thickness, which is the objective of the present invention, cannot be achieved.

Even if it exceeds 0.60, the purpose of the present invention can be achieved, but the effect of increasing the particle thickness reaches almost saturation, and there is no point in adding more than necessary.

Glycerin is involved in the thickness of the plate-shaped Ba ferrite fine particles that are produced, and therefore
It must be added before the Ba ferrite fine particle production reaction starts, and it can be added to either Ba raw material, Fe () raw material, M () raw material, Ti () raw material, or alkaline iron hydroxide (2). be able to.

The heat treatment temperature in the present invention is 900°C or lower.

When the temperature exceeds 900°C, sintering of particles and particles among themselves is significant.

When considering the magnetization value and powder characteristics of the plate-shaped Ba ferrite particles, the temperature is preferably 700°C to 900°C.

In the heat treatment in the present invention, it is preferable to coat the surface of the plate-shaped Ba ferrite fine particles with a water-soluble silicate or the like having a sintering prevention effect in advance.

〔Example〕

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

In addition, the average diameter of the particles in the above experimental examples, the following examples, and comparative examples is a value measured from an electron micrograph, and the thickness of the particles is indicated by the half-width D ₁₁₄ determined by X-ray diffraction method. , the specific surface area value is N ₂
This shows the value measured by the BET method using

In addition, the magnetization value and coercive force are
This was measured in a magnetic field of 10KOe.

Example 1 14 mol of Fe(NO ₃ ) ₃ , 0.4 mol each of Co(NO ₃ ) ₂ and TiOSO ₄ , 1.56 mol of BaCl ₂ , 36 g of glycerin
(This corresponds to a molar ratio of 0.028 to Fe().)
164 mol of NaOH was added to 20 ml of water in an autoclave, heated to 300°C, and maintained at this temperature for 5 hours with mechanical stirring to form a ferromagnetic brown precipitate. After cooling to room temperature, the ferromagnetic brown precipitate was separated, thoroughly washed with water, and dried.

The obtained ferromagnetic brown powder has an average diameter of 0.1 μm,
It is a plate-shaped particle with a thickness of 223 Å and a specific surface area (S) value of 49.1 m ² g ^-1 , and as a result of fluorescent X-ray analysis,
The composition was BaO.4.7 {(Fe _0.95 Co _0.027 Ti _0.027 ) ₂ O ₃ }.

In addition, regarding magnetism, the magnetization (M) value is 34.1 emug ^-1 ,
The coercive force (Hc) value was 568 Oe.

Example 2 A ferromagnetic brown precipitate was obtained in the same manner as in Example 1, except that the amount of glycerin added was 181 g (corresponding to a molar ratio of 0.14 to Fe()).

The obtained ferromagnetic brown powder has an average diameter of 0.1 μm,
It is a plate-shaped particle with a thickness of 268 Å and a specific surface area (S) value of 42.1 m ² g ^-1 , and as a result of fluorescent X-ray analysis,
The composition was BaO.4.7 {(Fe _0.95 Co _0.027 Ti _0.027 ) ₂ O ₃ }.

In addition, regarding magnetism, the magnetization (M) value is 35.6emug ^-1 ,
The coercive force (Hc) value was 621 Oe.

Example 3 A ferromagnetic brown precipitate was obtained in the same manner as in Example 1, except that the amount of glycerin added was 542 g (corresponding to a molar ratio of 0.42 to Fe()).

The obtained ferromagnetic brown powder has an average diameter of 0.1 μm,
It is a plate-shaped particle with a thickness of 306 Å and a specific surface area (S) value of 37.4 m ² g ^-1 , and as a result of fluorescent X-ray analysis,
The composition was BaO.4.7 {(Fe _0.95 Co _0.027 Ti _0.027 ) ₂ O ₃ }.

In addition, regarding magnetism, the magnetization (M) value is 38.3emug ^-1 ,
The coercive force (Hc) value was 706 Oe.

Example 4 Each of 14 mol of FeCl ₃ , CoCl ₂ and TiCl ₄
1.2mol, BaCl ₂ 1.65mol, glycerin 542g (Fe
() corresponds to a molar ratio of 0.14. )and
170 mol of NaOH was added to 20 ml of water in an autoclave, heated to 200°C, and maintained at this temperature for 5 hours with mechanical stirring to form a ferromagnetic brown precipitate. After cooling to room temperature, the ferromagnetic brown precipitate was separated, thoroughly washed with water, and dried.

The obtained ferromagnetic brown powder has an average diameter of 0.1 μm,
It is a plate-shaped particle with a thickness of 281 Å and a specific surface area (S) value of 43.2 m ² g ^-1 , and as a result of fluorescent X-ray analysis,
The composition was BaO.5.0 {(Fe _0.85 Co _0.073 Ti _0.073 ) ₂ O ₃ }.

Further, the magnetization (M) value was 34.7 emug ^-1 .

Next, the above ferromagnetic brown powder was coated with sodium silicate No. 3 (28.55% by weight of SiO ₂ ) of 3.0% by weight in terms of SiO ₂ based on Fe(), and then heated at 830°C in air.
Heat treated at ℃.

Ferromagnetic properties obtained by heat treatment
BaO・5.0 {(Fe _0.85 Co _0.073 Ti _0.073 ) ₂ O ₃ } fine particle powder has an average diameter of 0.1 μm, a thickness of 289 Å, and a specific surface area (S).
The value was 32.3 m ² g ^-1 .

Regarding magnetism, the magnetization (M) value was 54.2 emug ^-1 and the coercive force (Hc) value was 901 Oe.

Furthermore, as a result of electron microscopy, it was found that the plate-shaped particles were prevented from sintering.

Comparative Example 1 A ferromagnetic brown precipitate was produced from an aqueous solution in the same manner as in Example 4, except that glycerin was not present.

The ferromagnetic brown particles obtained by treatment in the same manner as in Example 4 are plate-shaped particles having an average diameter of 0.1 μm, a thickness of 173 Å, and a specific surface area (S) value of 77.1 m ² g ^-1 . As a result of line analysis, BaO・5.0 {(Fe _0.85
Co _0.073 Ti _0.073 ) ₂ O ₃ }.

〔effect〕

According to the manufacturing method of the plate-shaped Ba ferrite fine particle powder of the present invention, as shown in the previous example, BaO.
{(Fe _1-xy Ti _x M _y ) ₂ O ₃ } (However, x≦0.1 y≦0.1
4≦n≦6) Due to the ability to generate fine particles, it is possible to obtain plate-shaped Ba ferrite fine particles with appropriate coercive force (Hc) and good dispersibility, so it is a magnetic material powder for magnetic recording. It is suitable as

[Brief explanation of drawings]

Figure 1 shows the amount of glycerin added and _{the plate -} like BaO produced from the _aqueous solution _.
As a representative value of the thickness of fine particles by X-ray diffraction method
This shows the relationship with the value of _D114 .

Claims (1)

[Claims] 1 Ba ion, Ti () and divalent metal ion M
In the method of producing a plate-shaped Ba ferrite fine particle powder by hydrothermally treating an alkaline iron hydroxide () suspension containing at least Co () as () in a temperature range of 150 to 330°C, the alkaline iron hydroxide () in advance into suspension
By adding glycerin at a predetermined molar ratio within the range of 0.01 to 0.60 to Fe(), plate-like BaO・n{(Fe _{1 -xy} Ti _x M _y ) ₂ O ₃ } (However, x
≦0.1 y≦0.1 4≦n≦6) A method for producing a plate-shaped Ba ferrite fine particle powder for magnetic recording, characterized in that fine particles are obtained. 2 Ba ion, Ti () and divalent metal ion M
In the method of producing a plate-shaped Ba ferrite fine particle powder by hydrothermally treating an alkaline iron hydroxide () suspension containing at least Co () as () in a temperature range of 150 to 330°C, the alkaline iron hydroxide () in advance into suspension
By adding glycerin at a predetermined molar ratio within the range of 0.01 to 0.60 to Fe(), plate-like BaO・n{(Fe _{1 -xy} Ti _x M _y ) ₂ O ₃ } (However, x
≦0.1 y≦0.1 4≦n≦6) Generate fine particles,
1. A method for producing plate-shaped Ba ferrite fine particles for magnetic recording, which comprises heat-treating the fine particles at a temperature of 900° C. or lower.