JP2860928B2 - Manufacturing method of oxide magnetic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an oxide magnetic material having a predetermined value of saturation magnetization from hematite powder.

[0002] Single-phase magnetite powder, which is an oxide magnetic material, is widely used for magnetic fluids, electric resistance elements, toners and carriers for electrophotography, etc. It is desired to produce what has.

[0003]

2. Description of the Related Art Conventionally, the following three methods have been known for producing magnetite powder as an oxide magnetic material.

(1) Wet method (coprecipitation method): Fe ²⁺ + 2F
The aqueous solution of e ³⁺ is made alkaline and the magnetite powder Fe ₃
O ₄ is produced by coprecipitation. (2) Dry method: Hematite α-Fe ₂ O ₃ is heated and reduced in hydrogen / carbon monoxide or steam to produce magnetite powder Fe ₃ O ₄ .

(3) Pulverization method: Magnetite powder is produced by crushing naturally occurring magnetite. Also, the inventor of the present application
It is described in Japanese Patent Application Laid-Open No. 5-14733 filed earlier.
To convert magnetite from hematite
There is a method of manufacturing it.

[0006]

The magnetite powder produced by the above-mentioned conventional production method has a higher saturation magnetization than the value of general spinel ferrite, and the saturation magnetization cannot be adjusted by the composition. There is a problem that it cannot be applied to applications that are difficult to use with a specific saturation magnetization value. The value of the intrinsic saturation magnetization of this magnetite powder (fixed value shown in the experimental example of FIG.
At 1 emu / g), only a small portion was used for applications such as carriers for electrophotographic development. Also,
Japanese Patent Application Laid-Open No. 5-14733 filed earlier by the inventor of the present application
The stated "Hematite powder has a single bond between carbon atoms.
Liquid or powdered substance having
After adding 4.0% by weight and mixing almost uniformly, an inert gas
Characterized by heat treatment at 1200-1450 ° C
Manufacturing method of single phase magnetite powder "
Magnetite cannot adjust the saturation magnetization.
Magnetic properties such as saturation magnetization of the manufactured magnetite
It is desired to improve.

[0007] The present invention solves these problems,
A substance having a single bond or a double bond between carbon atoms is mixed with hematite powder and fired to generate a magnetite powder, which is then fired again in an oxygen atmosphere to obtain an oxide magnetic material having a desired saturation magnetization. It is intended to be simple, inexpensive, and mass-produced.

[0008]

Means for solving the problem will be described with reference to FIG. In FIG. 1, in the mixing step 2, a liquid substance or a powdery substance having -C-C- or -C = C- in a molecule is added to a hematite powder in 0.1.
This is a step of mixing ｗｔ4.0 wt%.

[0009] Granulation step 4 is a step of converting hematite powder into spherical granules. Firing step 5 is performed in an inert gas at 120
This is a step of generating magnetite powder by performing a baking treatment at 0 to 1450 ° C.

In the re-firing step 7, the magnetite powder produced in the firing step 5 has an oxygen concentration of 0.1 to 21%.
This is a step of performing a baking treatment in the range of 350 to 1100 ° C.

[0011]

According to the present invention, as shown in FIG. 1, in a mixing step 2, a liquid substance or a powdery substance having -CC- or -C = C- in a molecule is contained in a hematite powder in an amount of 0.1 to 4%. .0
wt%, and sintering 12
The magnetite powder is generated by firing at 00 to 1450 ° C., and the magnetite powder is re-fired at 350 to 1100 ° C. in an oxygen concentration of 0.1 to 21% in a re-firing step 7 to obtain an arbitrary value. An oxide magnetic material having a saturation magnetization is manufactured.

At this time, the hematite powder is made into spherical granules and the oxide magnetic material is made into spherical by the granulation step 4 before the firing step 5. Therefore, a substance having a single bond or a double bond between carbon atoms is mixed with the hematite powder, and the mixture is fired to generate a magnetite powder. It is possible to easily, inexpensively, and mass produce magnetic materials.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of an embodiment of the present invention will be described in order with reference to FIGS.

FIG. 1 is a block diagram showing one embodiment of the present invention.
In FIG. 1, the blending step 1 is performed at a predetermined particle size (for example,
This is a step of blending the hematite powder of m) and various additives as necessary.

In the mixing step 2, -C-C-
Alternatively, this is a step of mixing 0.1 to 4.0 wt% of a compound having -C = C- in the molecule (liquid substance or solid substance). For example, 2 wt% of polyvinyl alcohol and 1 wt% of a polycarboxylate as a dispersant are added to hematite powder, and water for granulation into spherical granules is further added. Here, water is added in a range of 30% to 70%. If it is less than 30%, the viscosity of the slurry at the time of kneading is too high to form a spheroid. If it was more than 70%, the slurry concentration was too low to obtain dense spherical granules.

The pulverizing step 3 is a step in which the mixture obtained in the mixing step 2 is wet-pulverized with an attrition mill to prepare a slurry having a hematite concentration of about 50% by weight. The granulation step 4 is a step for producing spherical granules. Here, the slurry is stirred for 1 hour with an attritor and then dried with hot air using a spray drier to form spherical granules.

In the calcination step 5, the granules obtained in the granulation step 4 are mixed with each other in an inert gas (for example, in a nitrogen gas) from 1200 to 14%.
This is a step of performing heat treatment at a temperature in the range of 50 ° C. for 2 hours to obtain a single-phase magnetite powder. Here, in addition to the thermal transition from hematite to magnetite in an inert gas (in a weak reducing atmosphere), an organic substance mixed with hematite powder is heated in an inert gas to an incomplete combustion state, During thermal decomposition, it deprives hematite of oxygen and reduces it, greatly promoting magnetite formation.

The crushing step 6 is a step of peeling off the grains baked in the firing step 5. In the re-firing step 7, the generated single-phase magnetite powder is subjected to an oxygen concentration of 0.1 to 21%.
This is a step of performing reheating treatment in the range of 350 to 1100 ° C. for 2 hours in (oxygen concentration in air) to oxidize the surface of the magnetite powder and adjust the saturation magnetization (see the saturation magnetization in FIG. 3). .

The crushing step 8 is a step of crushing the refired mixed powder of magnetite and hematite to finish the product. According to the above process, the hematite powder is -C-C-
Alternatively, -C = C- and water are mixed, kneaded well, dried with hot air, granulated into a sphere, and then 1200 g in an inert gas.
After sintering in the range of 〜1450 ° C. to produce a single-phase hematite powder, the sintering is carried out at a concentration of 350 to 150% in an oxygen gas concentration of 0.1 to 21%.
The surface of the single-phase hematite powder is oxidized by re-baking in the range of 1100 ° C., and a spherical magnetite-hematite mixed powder (having a desired saturation magnetization (〜91 emu / g according to the experimental example in FIG. 3)) Oxide magnetic powder). This has made it possible to produce oxide magnetic powder having a desired saturation magnetization inexpensively, in large quantities, and safely.
This will be described sequentially below.

FIG. 2 shows an example of the results of a firing experiment of the present invention.
This is obtained by adding PVA (polyvinyl alcohol) to the hematite powder in the amount shown in the figure and adding water to 1 wt% of a polycarboxylate as a dispersant, mixing and granulating the resultant, and then firing at the heating temperature shown in the figure. 3 is a qualitative analysis result by powder X-ray diffraction. The comparative example is an experimental example for comparison. The embodiment is an embodiment of the present invention. The following was found from this experimental example.

(1) When only hematite powder was used without adding PVA (sample numbers 1 to 8), single-phase magnetite was not obtained even when the heating temperature was changed. According to the result of the X-ray diffraction, a phase of α-Fe ₂ O ₃ or FeO is present.

(2) The amount of PVA added is 2 wt%,
When the heating temperature was changed, single-phase magnetite was obtained in the range of 1200 to 1450 ° C (sample numbers 13 to 1).
5). At 1150 ° C or lower, α-Fe ₂ O ₃ coexisted (sample numbers 9 to 12), and at 1500 ° C or higher, FeO coexisted (sample number 16). Therefore, the heating temperature is 1200
５０1450 ° C. (Sample No. 13
To 15).

(3) When the heating temperature was fixed at 1300 ° C. and the amount of PVA added was changed from 0.1 to 3.0 wt%, all single-phase magnetite was obtained (Sample No. 17).
~ 22).

From the above experimental results, PVA was added to the hematite powder.
It was found that firing at a heating temperature in the range of 1200 to 1450 ° C. with an addition amount of 0.1 to 3 wt% (4 wt%) can produce all single-phase magnetite.

FIG. 3 shows an example of the results of a refiring experiment according to the present invention. This is because the saturation magnetization of the single-phase magnetite powder fired in the range shown in the firing experiment result example of FIG. 2 when refired for 2 hours at the heating temperature shown in the atmosphere of the constant oxygen concentration shown, It was measured with a vibrating magnetometer (see FIGS. 4 and 5). The oxygen concentration in the gas was measured with a zirconia oxygen concentration meter.

(1) In the case where re-firing was not performed (Sample No. 1), the saturation magnetization was 91 emu / g. (2) When the atmosphere is 21% O ₂ (oxygen concentration of air), baking is performed at a heating temperature of 300 to 900 ° C., and magnetite powder having a saturation magnetization of 91 to 1.3 emu / g as shown in the figure. A mixed powder of magnetite and hematite with the surface oxidized was obtained.

(3) When the atmosphere is 2.0% O ₂ ,
Similarly to (2), firing is performed at a heating temperature in the range of 300 to 900 ° C., and a saturation magnetization of 91 to 1.3 emu /
A mixed powder of magnetite and hematite obtained by oxidizing the surface of the magnetite powder in the range of g was obtained.

(4) When the atmosphere is 0.2% O ₂ , baking is performed at a heating temperature of 300 to 1150 ° C., and the surface of the magnetite powder having a saturation magnetization of 91 to 10 emu / g is removed as shown in the figure. A mixed powder of oxidized magnetite and hematite was obtained.

(5) When the atmosphere is 0.1% O ₂ , baking is performed at a heating temperature in the range of 300 to 1100 ° C., and the surface of the magnetite powder having a saturation magnetization of 91 to 35 emu / g as shown in FIG. A mixed powder of oxidized magnetite and hematite was obtained.

From the above experimental results, the single-phase magnetite powder obtained in the firing experiment shown in FIG. 2 was mixed with oxygen gas at 0.1 to 21% (oxygen concentration of air) at a heating temperature of 350 to 1100 °. It was found that mixed powder of magnetite and hematite having an arbitrary saturation magnetization (oxide magnetic material powder) can be generated by heating for a period of time.

FIG. 4 shows an example of a heating curve during refiring according to the present invention. This is an example of a heating curve at the heating temperature T ° C and 2Hr (heating at the heating temperature T ° C for 2 hours) in FIG. Initially, the temperature gradually rises from room temperature to T ° C, is maintained at T ° C for 2 hours, and then gradually returns to room temperature. Here, T ° C is
This is the heating temperature in FIG.

FIG. 5 is an explanatory diagram of the saturation magnetization of the present invention. This is an explanatory diagram when measuring the saturation magnetization of FIG. The horizontal axis represents the intensity H Oe of the applied magnetic field, and the vertical axis represents the magnetization intensity Memu at that time. As shown in the figure, the vibrating magnetometer measures the magnetization intensity Ms of the magnetite powder in a state where a magnetic field of, for example, 15 kOe is applied.
Measure emu. The saturation magnetization is calculated by the following equation: δs = Ms / (weight g of magnetite powder) [emu /
g] (1) The value obtained by the equation (1) is the saturation magnetization δs in FIG.

[0033]

As described above, according to the present invention,
Hematite powder is mixed with a substance having a single or double bond between carbon atoms, fired to produce magnetite powder, and then fired again in an oxygen atmosphere to obtain an oxide magnet with an arbitrary value of saturation magnetization. Since the material manufacturing configuration is adopted, the oxide magnetic material having the desired saturation magnetization can be easily manufactured.
Inexpensive and can be manufactured in large quantities. In particular, after a large amount of hematite powder is converted into a single-phase magnetite powder at the same time by the firing step 5, the surface of the magnetite powder is oxidized by the re-firing step 7 in an oxygen atmosphere to obtain a magnetite + hematite having any saturation magnetization. The inclusion (oxide magnetic material) could be manufactured in a simple process, easily and inexpensively.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention.

FIG. 2 is an example of a firing experiment result of the present invention.

FIG. 3 is an example of the results of a refiring experiment of the present invention.

FIG. 4 is an example of a heating curve during refiring according to the present invention.

FIG. 5 is an explanatory diagram of a saturation magnetization of the present invention.

[Explanation of symbols]

 1: Compounding step 2: Mixing step 3: Pulverizing step 4: Granulating step 5: Firing step 6: Disintegrating step 7: Refiring step 8: Disintegrating step

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Shimokawa 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (56) References JP-A-63-184764 (JP, A) (58 ) Surveyed field (Int.Cl. ⁶ , DB name) H01F 1/11

Claims (2)

(57) [Claims] (1) A hematite powder having -CC- or -C =
A liquid substance or a powdery substance having C- in a molecule is mixed in an amount of 0.1 to 4.0 wt%, and the mixture is mixed in an inert gas at 1200
A magnetite powder is generated by firing at ~ 1450 ° C, and the magnetite powder is refired at 350 to 1100 ° C in an oxygen concentration of 0.1 to 21% to obtain an oxide having a predetermined value of saturation magnetization. A method for producing an oxide magnetic material for producing a magnetic material. 2. A method for producing an oxide magnetic material according to claim 1, wherein the hematite powder is formed into spherical granules by a granulation treatment before the calcination treatment, and the oxide magnetic material is formed into a spherical shape. Method.