JPH11214208A - Method for manufacturing anisotropic oxide magnetic body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide magnetic body of high characteristics by improving magnetic field orientation characteristics at wet molding which, advantageous in environment and cost, uses water, related to a manufacturing process for an oxide magnetic body such as anisotropic ferrite magnet. SOLUTION: A molding process wherein a a molding material comprising oxide magnetic body particles, water, and dispersing agent is molded in a magnetic field to obtain a molded body is provided. Here, the dispersing agent is either organic compound comprising hydroxyl group and carboxyl group or its neutralization salt or its lactone, organic compound comprising hylodoxymethylcarbonyl, or organic compound comprising enol form hydroxyl group which can be dissociated as acid ot its neutralization salt. The organic compound is of carbon numbers 3-20, wherein 50% or above of carbon atom except for such carbon atom as double-bonded to oxygen atom is combined to hydroxyl group. The molding material is further added with fine powder, the average particle size of fine powder in the molded body is smaller than that of the oxide magnetic body while the fine powder is added by 1-100 vol.% relative to the oxide magnetic body particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an anisotropic oxide magnetic material such as an anisotropic ferrite magnet.

[0002]

2. Description of the Related Art At present, hexagonal Sr ferrite and Ba ferrite are used as oxide permanent magnet materials, and these magnets are widely anisotropic by pressing in a magnetic field in order to improve magnet performance. Is being done. Factors that greatly affect magnet performance include residual magnetic flux density. The residual magnetic flux density Br has the following relationship.
Note that the saturation magnetization per unit weight (σ
s) is a value specific to the substance.

Formula Br = (constant) × (saturation magnetization per unit weight) × (density) × (degree of orientation)

[0004] Therefore, in manufacturing anisotropic sintered ferrite magnets, the sintered density and the degree of orientation are very important. In order to obtain a high degree of orientation, a so-called wet forming method of forming a slurry in which ferrite particles are dispersed in water has been conventionally performed. On the other hand, in order to obtain a large coercive force, the particle size of the ferrite is set to 1 μm, which is the critical diameter of a single magnetic domain.
Although it is necessary to form a single magnetic domain as m or less, such particles have a problem that the degree of orientation generally decreases even when a wet molding method is used. The causes include an increase in magnetic cohesion due to the formation of a single magnetic domain of the particles, a decrease in torque toward the magnetic field direction, an increase in frictional force due to an increase in surface area, and the like.

[0005] To solve these problems, the present inventors can reduce the magnetic cohesion by introducing grinding strain into submicron ferrite particles to temporarily reduce the coercive force of the particles. (Japanese Patent Laid-Open No. 6-5 / 1994)
No. 3064).

Further, by using an organic solvent such as toluene or xylene instead of water, and adding a surfactant such as oleic acid, the use of ferrite particles of submicron size is the highest. It has been found that a high degree of magnetic orientation of about 98% can be obtained (also Japanese Patent Application Laid-Open No. 6-53064). However, this method has an adverse effect on the human body and the environment because it uses an organic solvent, and in order to solve this problem, a large-scale facility such as a recovery device is required, and the cost is increased.

On the other hand, in order to improve the degree of orientation in a wet magnetic field molding method using water, conventionally, a polymer dispersant represented by, for example, a polycarboxylic acid (salt) is added, and this is added to the surface of the magnetic particles. Attempts have been made to improve the degree of orientation by adsorbing and dispersing by the effects of steric hindrance and electrical repulsion (Japanese Patent Laid-Open No. 6-112029). However, the obtained degree of orientation and residual magnetic flux density Br are not high.

[0008] The problem that the orientation is deteriorated when the particle size is reduced is not limited to the case of manufacturing a ferrite magnet, and other magnetic oxide particles such as acicular soft magnetic ferrite are magnetically oriented. The same applies to the case.

In the present specification, the degree of magnetic orientation is a ratio (Ir / Is) of the residual magnetization (Ir) to the saturation magnetization (Is).

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic field orientation in wet molding using water, which is advantageous in terms of environment and cost in the process of producing an oxide magnetic material such as an anisotropic ferrite magnet. An object of the present invention is to obtain an oxide magnetic material having high characteristics by improving the properties.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (14). (1) A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing magnetic oxide particles, water and a dispersant in a magnetic field to obtain a molded body, The agent is an organic compound having a hydroxyl group and a carboxyl group or a neutralized salt thereof or a lactone thereof, or an organic compound having a hydroxymethylcarbonyl group,
An organic compound having an enol-type hydroxyl group which can be dissociated as an acid or a neutralized salt thereof, wherein the organic compound has 3 to 20 carbon atoms and is 50% or more of carbon atoms other than carbon atoms double-bonded to oxygen atoms. A fine powder is further added to the molding material, and the average particle size of the fine powder in the molded product is smaller than the average particle size of the oxide magnetic material; A method for producing an anisotropic oxide magnetic material, wherein a powder is added in an amount of 1 to 100% by volume based on the oxide magnetic material particles. (2) The fine powder in the compact is
The method for producing an anisotropic oxide magnetic material according to the above (1), wherein the average particle size is 0.01 to 2 μm. (3) The method for producing an anisotropic oxide magnetic material according to (1) or (2), wherein the fine powder contains a ferrite constituent element. (4) The method for producing an anisotropic oxide magnetic material according to any one of (1) to (3), wherein the organic compound having a hydroxyl group and a carboxyl group is gluconic acid. (5) The above-mentioned (1) to (1), wherein the organic compound having an enol-type hydroxyl group which can be dissociated as the acid is ascorbic acid.
(3) The method for producing an anisotropic oxide magnetic material according to any of (3). (6) A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing magnetic oxide particles, water and a dispersant in a magnetic field to obtain a molded product, The agent is citric acid or a neutralized salt thereof, fine powder is further added to the molding material, the average particle diameter of the fine powder in the molded body is smaller than the average particle diameter of the oxide magnetic material, A method for producing an anisotropic oxide magnetic material, wherein 1 to 100% by volume is added to the oxide magnetic material particles. (7) The method for producing an anisotropic oxide magnetic material according to any one of (1) to (6), wherein a basic compound is added to the molding material. (8) The above (1) to (1), wherein the dispersant is a calcium salt.
(7) The method for producing an anisotropic oxide magnetic material according to any of (7). (9) The method for producing an anisotropic oxide magnetic material according to any one of the above (1) to (8), further comprising a wet pulverizing step before the forming step. (10) The method for producing an anisotropic oxide magnetic material according to (9), wherein at least a part of the dispersant is added in the wet grinding step. (11) The method for producing an anisotropic oxide magnetic material according to the above (9) or (10), further comprising a dry coarse grinding step before the wet powder step. (12) The method for producing an anisotropic oxide magnetic material according to (11), wherein at least a part of the dispersant is added in the dry coarse pulverization step. (13) The amount of the dispersant added (when the dispersant can be ionized in an aqueous solution, the amount in terms of ions) is 0.05 to 3.
The method for producing an anisotropic oxide magnetic material according to any one of the above (1) to (12), which is 0% by weight. (14) A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing magnetic oxide particles, water and a dispersant in a magnetic field to obtain a molded product, The agent is a saccharide having a carboxyl group or a derivative thereof, or an organic substance which is a salt thereof, and a fine powder is further added to the molding material. A method for producing an anisotropic oxide magnetic material, which is smaller than the average particle size of the oxide magnetic material and is added in an amount of 1 to 100% by volume based on the oxide magnetic material particles.

[0012]

The present inventors have studied conditions under which a high degree of orientation can be obtained even when an aqueous dispersion medium is used.
No. 37445 found a method of improving the degree of orientation by using a specific dispersant such as gluconic acid (salt).
Specifically, the degree of magnetic orientation when submicron ferrite particles are wet-pulverized and molded using water as a dispersion medium and sintered is 93 to 94% when no dispersant is added.
It is about 94% when a polycarboxylic acid type compound conventionally used as a dispersant is used, but becomes 95 to 96% when gluconic acid is used as a dispersant.

However, this method also uses an organic solvent (xylene) as a dispersion medium and oleic acid as a dispersant, and has a magnetic orientation of 97 to 98%. The degree of magnetic orientation was not sufficiently satisfactory.

On the other hand, in the method according to the present invention, the degree of magnetic orientation is drastically improved by further including fine powder in the molding slurry and regulating the average particle size in the final state of the slurry. In addition, even in an aqueous system, a high degree of orientation of 96 to 98%, which is as high as that of the organic solvent system, can be obtained.

This fine powder is added to the compact, particularly to the slurry immediately before the compaction, and needs to have an average particle size smaller than that of the oxide magnetic material. The magnetic properties of the fine powder are not particularly limited, and may be soft magnetic, hard magnetic, or non-magnetic. When sintering an oxide magnetic material, it is preferable that the magnetic characteristics of the oxide magnetic material do not deteriorate after sintering. For example, when producing ferrite as an oxide magnetic material, the fine powder contains the main components of ferrite (Fe, Sr, La, Co).
Etc.).

Most of the conventionally used aqueous polymer dispersants are artificially synthesized and are not easily biodegradable and have a problem of drainage treatment. It is naturally occurring, is safe for the human body and the environment, and has the advantage that it can be decomposed by microorganisms and the like.

Among the dispersants used in the present invention, substances which have been confirmed to have a particularly high effect of improving the degree of orientation include, for example, hydroxycarboxylic acids such as gluconic acid, neutralized salts thereof, and lactones thereof. However, glycolic acid (C = 2; OH = 1; COOH = 1) had no effect. In addition, ascorbic acid (C = 6; OH =
The same effect as in the above hydroxycarboxylic acid was also observed in 4).

In the present invention, when a dispersant (such as hydroxycarboxylic acid) having an acid property in an aqueous solution is used, the degree of orientation is further improved by adding a basic compound to raise the pH of the slurry supernatant. .

In the ferrite magnet manufacturing process, SiO ₂ and CaCO ₃ are added as subcomponents. When hydroxycarboxylic acid or its lactone is used as a dispersant, SiO ₂ and CaCO ₃ are used in the forming slurry preparation process and the wet forming process. ₂ and a part of CaCO ₃ flow out. In addition, when the above-mentioned basic compound is added for adjusting pH in addition to hydroxycarboxylic acid and its lactone, the amount of outflow becomes larger. On the other hand, when the calcium salt of hydroxycarboxylic acid is used as the dispersant, the outflow of SiO ₂ and CaCO ₃ is avoided, and the deterioration of characteristics such as a decrease in HcJ due to this is suppressed.

Among the dispersants used in the present invention, tartaric acid, L-ascorbic acid, and citric acid are known as dispersants for improving the formability in the slurry casting method ("Fine Ceramics"). Molding and Organic Materials, pp. 187-188, by Katsuyoshi Saito, published by CMC Corporation). However, the book states that 1
There are two types of classifications, including a polycarboxylic acid type anionic surfactant having a small effect of improving the degree of orientation. One of the categories includes organic acids, citric acid, tartaric acid and L-ascorbic acid, but again, not all organic acids are effective. In fact, succinic acid having a structure relatively close to tartaric acid has no effect of improving the degree of orientation and is outside the scope of the present invention. In the same book, there is no limited description that an acid having a large number of hydroxyl groups in the molecule is effective as in the present invention. The present invention is characterized in that among the known dispersants used for improving the formability in the slurry casting method, a dispersant that is particularly effective in improving the degree of orientation of the oxide magnetic material is selected. Things.

Among the dispersants used in the present invention, sodium gluconate is known as a dispersant in the concrete industry (see "Chemistry of Dispersion and Aggregation", ninth edition).
2-95 pages, by Noboru Moriyama, published by Sangyo Tosho). But,
The purpose of adding a dispersant in the concrete industry is to improve the fluidity and increase the strength by reducing water. No relationship. Even if a commercially available high-performance water reducing agent is applied to the production of an oxide magnetic material, few exhibit an effect of improving the degree of orientation, and even if there is an improvement, the degree is not so large.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applicable to the production of various oxide magnetic materials. For example, hexagonal M-type and W-type ferrite magnets, X-type, Y-type, and Z-type hexagonal ferrites, acicular γ-Fe ₂ O ₃ having shape anisotropy, and Co-containing γ-
Any of Fe ₂ O ₃ magnetite, CrO _{2 and the} like may be used. In this case, a particularly remarkable effect is obtained with an anisotropic ferrite magnet. Therefore, in the following description, an anisotropic ferrite magnet will be described.

The anisotropic ferrite magnet to which the present invention is applied is mainly a hexagonal M-type ferrite. Such ferrite, in _{particular, MO · nFe 2 O 3 (} M is one or more, preferably of Sr and Ba, n = 4.5 to 6.
5) is preferable. Such ferrites further include rare earth elements, Ca, Pb, Si, Al, G
a, Sn, Zn, In, Co, Ni, Ti, Cr, M
n, Cu, Ge, Nb, Zr, etc. may be contained.

More preferably, at least one element selected from Sr, Ba, Ca and Pb is A, and at least one element selected from rare earth elements (including Y) and Bi is R, Co and / or Z
When n is L, the total composition ratio of each metal element of A, R, Fe and L is: A: 1 to 13 atomic%, R: 0.05 to 10 atomic%, It is preferable that the main phase contains hexagonal magnetoplumbite (M-type) ferrite having an Fe content of 80 to 95 atomic% and an L content of 0.1 to 5 atomic%. In this case, R is preferably La, Pr, or Nd, particularly preferably La, and Bi may be used in combination. As L,
Co and / or Zn are preferred.

To manufacture such an anisotropic ferrite sintered magnet, first, ferrite particles (calcined body) are prepared. That is, preferably, a raw material of the ferrite composition, for example, an oxide such as A, R, Fe, L, or a compound which becomes an oxide by firing is mixed, and then calcined. The calcination is performed in the atmosphere at, for example, 1000 to 1350 ° C. for 1 second to
In order to obtain a fine calcined powder of M-type Sr ferrite for 10 hours, particularly at 1000 to 1200 ° C., it may be performed for about 1 second to 3 hours.

Such a calcined powder is substantially composed of granular particles having a ferrite structure of magnetoplumbite type, and the primary particles have an average particle size of 0.1 to 3 μm, especially 0.1 to 1 μm. More preferably, it is 0.1 to 0.5 μm. In this case, the average particle size is a number average with respect to the average value of the maximum particle size and the minimum particle size of the particles. If the average particle size is too large, it is difficult to obtain the effect of improving the degree of orientation. The average particle size may be measured by a scanning electron microscope (SEM), and usually an average of 100 or more particles is taken. The coefficient of variation C
V is preferably 80% or less, generally 10 to 70%. The average particle size in the case of a hexagonal crystal is as described above, but in the case of a needle shape, it is 0.1 to 3 μm, particularly 0.1 to 1 μm.
μm, and more preferably about 0.1 to 0.5 μm.

The saturation magnetization .sigma.s of the calcined body of the M-type ferrite is 65 to 80 emu / g, especially 65 to 71.5 emu / g for the M-type Sr ferrite, and the coercive force HcJ is 2000 to 800.
0 Oe, especially 4000-8000 for M-type Sr ferrite
Oe is preferred.

Among these magnetic properties, the coercive force (HcJ) is particularly affected by the distortion introduced in the subsequent pulverization step.
Greatly reduced. The HcJ of the calcined powder may be 3.5 kOe or less, more preferably 3. kOe, when formed into a molding slurry by dry pulverization and / or wet pulverization.
It is preferably 0 kOe or less, particularly preferably 2.5 kOe or less. By adjusting the coercive force to such a value, the magnetic cohesive force of the calcined ferrite particles can be reduced.

In the present invention, molding is performed using a molding material containing magnetic oxide particles, water as a dispersion medium, and a dispersant. In order to increase the degree of orientation, wet molding is preferable. In order to further enhance the effect of the dispersant, it is preferable to provide a wet pulverization step before the wet molding step.
Further, when calcined particles are used as the oxide magnetic particles, the calcined particles are generally in a granular form. It is preferable to provide a pulverizing step. In addition, when the oxide magnetic particles are manufactured by a coprecipitation method or a hydrothermal synthesis method, the dry coarse pulverizing step is not usually provided, and the wet pulverizing step is not essential. Is preferably provided with a wet grinding step. Hereinafter, a case where the calcined particles are used as the oxide magnetic particles and a dry coarse pulverization step and a wet pulverization step are provided will be described.

In the dry coarse pulverization step, pulverization is usually performed until the BET specific surface area becomes about 2 to 10 times. The average particle size after pulverization is about 0.1-1 μm, and the BET specific surface area is 4-1
It is preferably about 0 m ² / g, and the CV of the particle size is 80%.
Hereinafter, it is particularly preferable to maintain the content at 10 to 70%. The pulverizing means is not particularly limited. For example, a dry vibrating mill, a dry attritor (medium stirring type mill), a dry ball mill and the like can be used, and it is particularly preferable to use a dry vibrating mill. The pulverization time may be appropriately determined according to the pulverization means.

The dry coarse pulverization also has an effect of reducing the coercive force HcB and HcJ by introducing crystal strain into the calcined particles. Due to the decrease in coercive force, magnetic aggregation of particles is suppressed,
The dispersibility is improved, and the degree of orientation is improved. The crystal strain introduced into the particles is released in a later sintering step, and the coercive force is restored, so that the particles can be made permanent magnets.

In the case of dry coarse pulverization, usually, SiO
₂ and CaCO ₃ which becomes CaO upon firing are added. SiO ₂ and CaCO ₃ may be partially added before calcination, in which case the improvement in properties is observed.

After the dry rough pulverization, a pulverization slurry containing the calcined particles and water is prepared, and wet pulverization is performed using the slurry. The content of the calcined particles in the slurry for pulverization is 10 to
It is preferably about 70% by weight. The grinding means used for wet grinding is not particularly limited, but is usually a ball mill,
It is preferable to use an attritor, a vibration mill or the like. The pulverization time may be appropriately determined according to the pulverization means.

After the wet pulverization, the pulverizing slurry is concentrated to prepare a molding slurry. Concentration may be performed by centrifugation, suction filtration, a filter press, or the like. The content of the calcined particles and the additive particles in the molding slurry is
Preferably 60-95% by weight, more preferably 70-8%.
It is about 5% by weight. If the content is too small, dehydration requires time, so that the molding time is prolonged and the productivity is reduced. On the other hand, if the content is too large, the degree of orientation decreases.

In the wet molding step, molding in a magnetic field is performed using a molding slurry. Molding pressure is 0.1-0.5ton / cm
^The applied magnetic field may be about ² to 15 kOe.

In the present invention, a molding material in which fine powder and a dispersant are added to water as a solvent is used. The molding material is preferably in the form of a slurry, but is not particularly limited. The fine powder used in the present invention needs to be one that does not hinder the properties of the ferrite magnet after firing, and is usually a material that can constitute ferrite. That is, it is an oxide of a ferrite constituent element or a compound which becomes an oxide by firing. Also preferably, rare earth oxides such as iron oxide, alumina, strontium carbonate, and lanthanum oxide; cobalt oxide, barium carbonate, silica, and the like are preferable; and rare earth oxides such as iron oxide, alumina, and lanthanum oxide; and cobalt oxide are preferable. . These fine particles may be used alone or in combination of two or more. When two or more kinds are used in combination, the mixing ratio is arbitrary. The shape of the fine powder may be spherical, flat, irregular, or the like.

The size of the fine powder is not particularly limited at the time of dry pulverization, wet pulverization or when added to a molding slurry, but the average particle size is 0.01 to 10%.
μm, more preferably 0.05 to 5 μm, particularly 0.05 to
It is preferably 1 μm. The specific surface area by the nitrogen adsorption method is 0.1 to 100 m ² / g, more preferably 0.1 to 100 m ² / g.
5 to 50 m ² / g, especially 1 to 30 m ² / g, furthermore 2-3
It is preferably 0 m ² / g. The average particle size of the fine particles is
It is a number average with respect to the average value of the maximum and minimum diameters of the particles,
It is preferable that the average particle size of the calcined powder used is 1/100 to 10, more preferably 5/100 to 1. After the fine powder is added to the slurry for molding, it is pulverized and adjusted to a predetermined size. Therefore, even if it is within the above range or deviates from the above range at the time of the addition, the average particle size of the oxide magnetic material (calcined body) after pulverization may be smaller than the average particle size of the oxide magnetic material (calcined body). .

Therefore, after pulverization, the average particle size of the fine powder immediately before molding is 0.01 to 2 μm, more preferably 0.05 to 2 μm.
It is preferably 1 μm, particularly preferably 0.05 to 0.6 μm. As a result, the average particle size of the fine powder in the compact is preferably 1/100 to 9/10, more preferably 5/100 to 7/10 of the average particle size of the calcined body. In addition,
When there are a plurality of types of fine powder, the average particle diameter is obtained by multiplying the average particle diameter of each powder by a weight ratio and averaging. The specific surface area of the mixture of the calcined particles and the fine powder by the nitrogen adsorption method is 0.1.
１００100 m ² / g, more preferably 1 to 50 m ² / g
It is particularly preferably 5 to 10 m ² / g. And as the size of the fine powder in the molded body, the average particle size is 0.01 to 2 μm, more preferably 0.03 to 1 μm,
Particularly, the thickness is preferably 0.05 to 7 μm.

If the primary particle size of the fine powder is too large, the effect of improving the degree of orientation cannot be obtained. If the particle size is too small, wet molding becomes difficult.

The amount of the fine powder to be added is 1 to 100% by volume, preferably 5 to 70% by volume based on the oxide magnetic particles.
%, More preferably 10 to 50% by volume. If the amount is too small, the effect of improving the degree of orientation cannot be obtained. If the amount is too large, molding becomes difficult and sintering is adversely affected.

The timing of adding the fine powder is not particularly limited, and may be added at the time of dry coarse pulverization, may be added at the time of preparing a slurry for wet pulverization, or may be partially added at the time of dry coarse pulverization. And the remainder may be added during wet grinding. Alternatively, it may be added by stirring after wet pulverization. In any case, since the fine powder is present in the molding slurry, the effect of the present invention is realized. However, the effect of improving the degree of orientation is higher at the time of pulverization, particularly at the time of dry coarse pulverization. When the fine powder is added in a plurality of times, the amount of each addition may be set so that the total amount of addition is within the above range.

In the present invention, a molding slurry to which a dispersant is added is preferably used. Dispersant used in the present invention,
An organic compound having a hydroxyl group and a carboxyl group, a neutralized salt thereof, a lactone thereof, an organic compound having a hydroxymethylcarbonyl group, or an enol-type hydroxyl group capable of dissociating as an acid It is an organic compound or a neutralized salt thereof.

Each of the above organic compounds has 3 to 20 carbon atoms,
It is preferably 4 to 12, and a hydroxyl group is bonded to 50% or more of carbon atoms other than the carbon atom double-bonded to the oxygen atom. If the number of carbon atoms is 2 or less, the effects of the present invention cannot be realized. Further, even when the number of carbon atoms is 3 or more, the effect of the present invention cannot be realized if the bonding ratio of the hydroxyl group to carbon atoms other than the carbon atom double-bonded to the oxygen atom is less than 50%. The bonding ratio of the hydroxyl group is limited for the above-mentioned organic compound, and is not limited for the dispersant itself. For example, when a lactone of an organic compound (hydroxycarboxylic acid) having a hydroxyl group and a carboxyl group is used as the dispersant, the limitation of the bonding ratio of the hydroxyl group is applied to the hydroxycarboxylic acid itself, not to the lactone.

The basic skeleton of the organic compound may be a chain or a cyclic, and may be saturated or contain an unsaturated bond.

As the dispersant, specifically, a hydroxycarboxylic acid or a neutralized salt thereof or a lactone thereof is preferable. Particularly, gluconic acid (C = 6; OH = 5; COOH
= 1) or a neutralized salt thereof or a lactone thereof, lactobionic acid (C = 12; OH = 8; COOH = 1), tartaric acid (C = 4; OH = 2; COOH = 2) or a neutralized salt thereof, glucoheptone Acid γ-lactone (C = 7; OH
= 5) is preferred. Among these, gluconic acid or its neutralized salt or its lactone is preferable because it has a high effect of improving the degree of orientation and is inexpensive.

As the organic compound having a hydroxymethylcarbonyl group, sorbose is preferred.

Ascorbic acid is preferred as the organic compound having an enol-type hydroxyl group that can be dissociated as an acid.

In the present invention, citric acid or a neutralized salt thereof can also be used as a dispersant. Citric acid has a hydroxyl group and a carboxyl group, but does not satisfy the condition that a hydroxyl group is bonded to 50% or more of carbon atoms other than a carbon atom double-bonded to an oxygen atom. However, the effect of improving the degree of orientation is recognized.

For some of the above preferred dispersants,
The structure is shown below.

[0050]

Embedded image

The degree of orientation by magnetic field orientation is determined by the pH of the slurry.
Affected by Specifically, if the pH is too low, the degree of orientation decreases, which affects the residual magnetic flux density after sintering. When a compound exhibiting an acid property in an aqueous solution, such as hydroxycarboxylic acid, is used as the dispersant, the pH of the slurry becomes low. Therefore,
For example, it is preferable to adjust the pH of the slurry by adding a basic compound together with the dispersant. As the basic compound, ammonia and sodium hydroxide are preferable. Ammonia may be added as aqueous ammonia. In addition, by using the sodium salt of hydroxycarboxylic acid, the pH can be prevented from lowering.

Like a ferrite magnet, Si
When adding O ₂ and CaCO ₃ , if hydroxycarboxylic acid or its lactone is used as a dispersing agent, SiO ₂ and CaCO ₃ are mainly used during preparation of a molding slurry.
Leaks out, and the desired performance cannot be obtained such as a decrease in HcJ. Further, when the pH is increased by adding the above basic compound or the like, SiO ₂ and CaCO 3
_3. More outflow. On the other hand, if the calcium salt of hydroxycarboxylic acid is used as a dispersant, Si
Outflow of O ₂ and CaCO ₃ is suppressed. However, when the basic compound is added or a sodium salt is used as a dispersant, if the SiO ₂ and CaCO ₃ are added excessively to the target composition, the amount of SiO ₂ and CaO in the magnet becomes insufficient. Can be prevented. When ascorbic acid is used, SiO ₂ and CaCO 3
The spill of ₃ is hardly noticeable.

For the above reasons, the pH of the slurry is preferably 8 or more, more preferably 9 to 11.

The type of the neutralizing salt used as the dispersing agent is not particularly limited, and may be any of a calcium salt and a sodium salt. For the above-mentioned reason, the calcium salt is preferably used. When a sodium salt is used as the dispersant or when ammonia water is added, there is a problem that, in addition to the outflow of subcomponents, cracks are easily generated in the formed body and the sintered body.

Incidentally, two or more dispersants may be used in combination.

The amount of the dispersant added is preferably 0.05 to 3.0% by weight, more preferably 0.10 to 2.0% by weight, based on the calcined particles which are oxide magnetic particles. . If the amount of the dispersant is too small, the degree of orientation will not be sufficiently improved. On the other hand, if the amount of the dispersing agent is too large, cracks are likely to occur in the molded body and the sintered body.

When the dispersant is one that can be ionized in an aqueous solution, for example, an acid or a metal salt, the amount of the dispersant to be added is an ion equivalent. That is, the amount of addition is determined in terms of organic components excluding hydrogen ions and metal ions.
When the dispersant is a hydrate, the amount of addition is determined excluding water of crystallization. For example, when the dispersant is calcium gluconate monohydrate, the amount to be added is calculated in terms of gluconate ions.

When the dispersant is made of lactone or contains lactone, the amount of addition is determined in terms of hydroxycarboxylic acid ions, assuming that all of the lactone is opened to form hydroxycarboxylic acid.

The dispersant used in the present invention may be a saccharide having a carboxyl group, a derivative thereof, or an organic compound which is a salt thereof. The dispersant has a carbon number of 21 or more.

The saccharides having a basic skeleton in the dispersant include polysaccharides such as cellulose and starch, as well as their reduced derivatives, oxidized derivatives, dehydrated derivatives and the like, and a wider range of derivatives such as amino sugars and thio sugars. And the like.

Examples of the saccharide having a carboxyl group include O
It is preferable that at least a part of the H group forms an ether bond with an organic compound having a carboxyl group. As such a compound, an ether of a saccharide and glycolic acid is preferable, and specifically, carboxymethyl cellulose or carboxymethyl starch is preferable. In these compounds, the degree of substitution of the carboxymethyl group, that is, the degree of ether becomes 3 at the maximum, and the degree of etherification is preferably 0.4 or more. If the degree of etherification is too small, it becomes difficult to dissolve in water. Note that carboxymethylcellulose is usually synthesized in the form of a sodium salt, and this sodium salt can also be used as a dispersant in the present invention. However, an ammonium salt is preferably used because it has little adverse effect on magnetic properties. Also,
Oxidized starch is also a saccharide having a carboxyl group in the molecule and is a dispersant preferably used in the present invention.

The timing of adding the dispersant is not particularly limited, and it may be added together with the fine powder, or both may be added separately. That is, it may be added during dry coarse pulverization,
It may be added when preparing a slurry for wet pulverization, a part may be added during dry coarse pulverization, and the remainder may be added during wet pulverization. Alternatively, it may be added by stirring after wet pulverization. In any case, the effect of the present invention is realized because the dispersant is present in the molding slurry. However, the effect of improving the degree of orientation is higher at the time of pulverization, particularly at the time of dry coarse pulverization. In a vibration mill or the like used for dry coarse pulverization, larger energy is given to the particles than in a ball mill or the like used for wet pulverization, and the temperature of the particles increases, so that the chemical reaction is likely to proceed. Therefore, if a dispersant is added at the time of dry coarse pulverization, the amount of the dispersant adsorbed on the particle surface increases, and as a result, a higher degree of orientation is considered to be obtained. Actually, when the residual amount of the dispersing agent in the molding slurry (which is considered to be almost equal to the adsorption amount) is measured, the amount of the dispersing agent added during the dry coarse grinding is larger than that when the dispersing agent is added during the wet grinding. The ratio of the residual amount to is increased. When the dispersant is added in a plurality of times, the amount of each addition may be set so that the total amount is within the above-described preferable range.

In the present invention, the content of additive particles such as calcined particles and fine powder in the molding slurry is 70%.
The content is preferably about 85% by weight, but the content can be increased as compared with a conventional production method in which gluconic acid or the like is not added. Therefore, it is possible to shorten the molding time while maintaining a high degree of orientation, and it is possible to approach the case of dry molding.

After the molding step, the molded body is heat-treated at a temperature of 100 to 500 ° C. in the air or in nitrogen to sufficiently decompose and remove the added dispersant. Next, in the sintering step, the molded body is preferably for example 1150-12 in air.
Sintering is performed at a temperature of 50 ° C., more preferably 1160 to 1220 ° C. for about 0.5 to 3 hours to obtain an anisotropic ferrite magnet.

The case where the present invention is applied to the production of an anisotropic sintered ferrite magnet has been described above. However, other oxide magnetic materials such as a soft magnetic ferrite sintered body using acicular ferrite particles or the like have been described. Even in the case of applying to the production of, by adding a dispersant according to the above description, the dispersibility of the oxide magnetic particles in the molding slurry becomes good, and as a result, the oxide magnetic material with a high degree of orientation is obtained. can get.

When the fine powder is added in an appropriate amount together with a specific dispersant such as gluconic acid, the degree of orientation is improved. The mechanism has not been clearly elucidated,
When the compact or slurry is analyzed by a scanning electron microscope (SEM) or the like, it can be confirmed that the added fine powder is present in a state of being dispersed on the surface of the oxide magnetic particles. It is considered that the aggregation of the magnetic particles is suppressed, and as a result, the magnetic particles are easily aligned in the direction of the magnetic field.

By using the sintered ferrite of the present invention, the following effects can be generally obtained, and an excellent applied product can be obtained. In other words, if the shape is the same as that of a conventional ferrite product, the magnetic flux density generated from the magnet can be increased, so that a motor can achieve higher torque, etc., and if it is a speaker or headphone, the magnetic circuit can be strengthened. It can contribute to high performance of applied products, such as obtaining good sound quality with linearity. Further, if the same function as in the related art is sufficient, the size (thickness) of the magnet can be reduced (thinned), which contributes to downsizing and weight reduction (thinning).
Further, even in a motor in which a field magnet is conventionally a winding type electromagnet, this can be replaced with a ferrite magnet, which contributes to weight reduction, shortening of a production process, and cost reduction. In addition, because of its excellent coercive force (HcJ) temperature characteristics, it can be used even in low-temperature environments where there was a risk of low-temperature demagnetization (permanent demagnetization) of ferrite magnets, especially in cold regions and in the sky. The reliability of the manufactured product can be significantly increased.

The sintered ferrite magnet of the present invention is processed into a predetermined shape and used for a wide range of applications as described below.

For example, for fuel pump, power window, ABS, fan, wiper, power steering, active suspension, starter,
Automotive motors for door locks, electric mirrors, etc .; FD
For D spindle, VTR capstan, VTR rotary head, VTR reel, VTR loading, VT
For R camera capstan, VTR camera rotating head,
Motors for OA and AV equipment such as VTR camera zoom, VTR camera focus, boombox capstan, CD, LD, MD spindle, CD, LD, MD loading, CD, LD optical pickup, etc .; Motors for home appliances such as for refrigerator compressor, electric tool drive, electric fan, microwave oven fan, microwave plate rotation, mixer drive, dryer fan drive, shaver drive, electric toothbrush, etc .;
Motors for FA equipment such as robot axes, joint drive, robot main drive, machine tool table drive, machine tool belt drive, etc .; motor generators, magnets for speakers and headphones, magnetron tubes, magnetic field generation for MRI It is suitably used for devices, clampers for CD-ROMs, sensors for distributors, sensors for ABS, fuel / oil level sensors, magnet latches, and the like.

[0070]

The present invention will be described in more detail with reference to the following examples. Among the dispersants used in the examples, a commercially available 50% aqueous solution of gluconic acid was used, and other reagents used were commercially available reagents.

Example 1 Raw materials were mixed with an attritor so that the target composition was SrFe ₁₂ O ₁₉ . At that time, in addition to this compounding raw material, SiO ₂ : 0.2% by weight, CaCO 2
₃ : 0.15% by weight was added. After crushing, drying and sizing, calcination in air at 1200 ° C. for 3 hours,
A granulated calcined body was obtained.

With respect to the obtained calcined powder, when expressed as Sr _1-x La _x Fe _12-x Co _x O ₁₉ , x = 0.1, 0.2, 0.3, 0.4 La ₂ (CO ₃ ) ₃ .8H ₂ O, cobalt oxide reagent (Co content = 71% by weight), average particle diameter 0.3 μm
(Specific surface area 2.6 m ² / g) α-Fe ₂ O ₃ was added. Table 1 shows the volume ratio of each additive at this time. The calcined body had an average particle size of 0.6 μm and a specific surface area of 1.1 m ^2.
/ G.

[0073]

[Table 1]

[Preparation of Aqueous Slurry] After adding 0.4% by weight of SiO _2, 1.25% by weight of CaCO _{3 and} 0.6% by weight of calcium gluconate to the above calcined composition, a vibrating rod mill was used. Dry coarse pulverization was performed for 20 minutes. The obtained pulverized powder was wet-pulverized in water by a ball mill for 40 hours. The specific surface area after wet grinding was 8.5 m ² / g. After the wet pulverization, the slurry for pulverization was centrifuged to adjust the concentration of the calcined particles in the slurry to 78% by weight to obtain a slurry for molding. Similarly, a comparative sample slurry to which gluconic acid was not added was prepared. The average particle size of the calcined particles in the slurry with the addition of calcium _{gluconate: 0.5μm, La 2 (CO 3} ) 3 · 8H
Average particle size of ₂ O: 0.4 μm, average particle size of cobalt oxide reagent (Co content = 71% by weight): 0.3 μm, α-Fe ₂
Average particle size of O ₃ : 0.2 μm. The same was true for the sample to which calcium gluconate was not added.

[Preparation of Organic Solvent-Based Slurry] (Comparative Example 1) SiO ₂ : 0.4% by weight, CaCO 2
₃ : After adding 1.25% by weight, dry coarse pulverization was performed for 20 minutes by a vibration rod mill. 1.3% by weight of oleic acid was added to the obtained pulverized powder, and wet pulverization was performed in xylene for 40 hours by a ball mill. The specific surface area after wet grinding was 8 to 10 m ² / g. After the wet pulverization, the slurry for pulverization is centrifuged, and the concentration of the calcined particles in the slurry is 8%.
It was adjusted to 3% by weight to obtain a molding slurry.
Average particle size of calcined body particles in slurry: 0.5 μm, La ₂
(CO ₃ ) ₃ .8H ₂ O: average particle size: 0.4 μm, cobalt oxide reagent (Co content = 71 wt%) average particle size: 0.1 μm
3 μm, average particle size of α-Fe ₂ O ₃ : 0.2 μm.

Each of the resulting molding slurries was weighed to about 13 kOe.
In the above magnetic field, wet magnetic field molding was performed so as to form a columnar shape having a diameter of 30Φ and a height of 15 mm. Next, the X-ray diffraction pattern of the c-plane of this molded body was measured, and the degree of orientation was determined by calculating the ratio of the sum of the diffraction intensities from the c-plane to the sum of all the diffraction intensities. That is, in the molded article, the value of the degree of magnetic orientation is also affected by the density of the molded article. The degree of crystallographic orientation (degree of X-ray orientation) was determined. The degree of X-ray orientation of the formed body controls the value of the degree of magnetic orientation of the sintered body to a considerable extent. In this specification, X
ΣI (00L) / ΣI (hkL) is used as the degree of linear orientation. (00L) is a general term for c-planes such as (004) and (006), and ΔI (00L) is the sum of all peak intensities of the (00L) plane. Also, (hkL)
Represents all detected peaks and ΔI (hkL)
Is the sum of their intensities. Therefore, ΣI (00
L) / ΣI (hkL) represents the degree of c-plane orientation. FIG.
The relationship between the amount of post-addition and the degree of orientation of the compact is shown in FIG.

As is clear from FIG. 1, when calcium gluconate was added in an aqueous system, the degree of orientation was improved as the amount of fine powder added increased, and the volume was 65% by volume (x
= 0.4), the organic solvent system (xylene +
A degree of orientation close to that of the sample of (oleic acid) was obtained.
The organic solvent-based sample also showed a tendency for the degree of orientation to increase as the amount of addition increased, but the ratio was extremely small.
On the other hand, in the comparative sample to which gluconic acid was not added even in an aqueous system, no improvement in the degree of orientation was observed even when the value of x was increased.

Example 2 (Type of Fine Powder) In Example 1, when the post-additive was added to the calcined composition, α-Fe ₂ O ₃ (iron oxide by Lusner method, : 0.3 μm, specific surface area 2.6 m ² / g, σs
= 0.7 emu / g, HcJ = 2180 Oe), γ-Fe ₂ O ₃
(Long axis: 0.7 μm, short axis: 0.1 μm, specific surface area 23 m
² / g), Fe ₃ O ₄ (average particle size: 0.1 μm, specific surface area 3)
5 m ² / g, σs = 70 emu / g, HcJ = 460 Oe), Sr
CO ₃ (average particle size: 3 μm, specific surface area: 4.2 m ² / g) was independently added to the calcined composition in an amount of 0 to 70% by volume. Each molded product was obtained in the same manner as in Experimental Example 1 except that the solvent was water and the dispersant was calcium gluconate.
FIG. 2 shows the relationship between the amount of fine powder of these compacts and the degree of orientation of the compacts. After the pulverization of the added fine powder, α-
Fe ₂ O ₃ has an average particle size of 0.2 μm, γ-Fe ₂ O ₃ has an average particle size of 0.2 μm, and Fe ₃ O ₄ has an average particle size of 0.1 μm.
μm and SrCO ₃ were 0.3 μm in average particle size, and the average particle size of the magnetic oxide (calcined) particles was 0.5 μm. Further, in the molded body, α-Fe ₂ O ₃
Average particle diameter: 0.2 μm, average particle diameter of γ-Fe ₂ O ₃ : 0.1.
2 μm, Fe ₃ O ₄ has an average particle size of 0.1 μm, SrCO ₃
However, the average particle diameter was 0.3 μm, and the average particle diameter of the oxide magnetic material (calcined body) particles was 0.5 μm.

As is clear from FIG. 2, the degree of orientation was improved in all the samples by adding the fine powder. That is, it turned out that it does not depend on the magnetic properties of the fine powder to be added.

Example 3 [Species of iron oxide (α-Fe ₂ O ₃ )
Class] In Example 1, iron oxide was used as a fine powder to be added, and the specific surface area was 0.9 m ² / g (iron oxide by the Lurugy method) [particle size: 0.2 to 8 μm (average: 1 μm)] ,
2.6 m ² / g (iron oxide by Lusner method) [particle size: 0.2
４4 μm (average: 0.5 μm)], 4.2 m ² / g (iron oxide by iron sulfate pyrolysis method) [particle size: 0.1 to 0.6 μm (average: 0.2 μm)], 6.0 m ² / g (iron oxide by Lusner method) [particle size: 0.1 to 0.6 μm (average: 0.5 μm
m)] was added in the same manner as in Example 1 except that 0, 14.8 and 29.5% by volume were added, respectively. The average particle size of these fine powders in the compact was 1 μm when the specific surface area was 0.9 m ² / g and 0.2 μm or 4.2 μm when the specific surface area was 2.6 m ² / g. 0.1μm in those ² / g, a 0.1μm in those 6.0 m ² / g,
The average particle size of the oxide magnetic (calcined) particles is 0.5 μm
Met.

FIG. 3 shows the relationship between the amount of fine powder of these samples and the degree of orientation of the compact.

As is apparent from FIG. 3, the effect of improving the degree of orientation was obtained when the specific surface area of the fine powder was 2.6 m ² / g or more (average particle size: 0.5 μm or less).

Example 4 (Addition timing of fine powder) In Example 1, α-Fe ₂
O ₃ (iron oxide by Lusner method, average particle size: 0.3 μm
m, specific surface area: 2.6 m ² / g), and a molded body was produced in the same manner as in Example 1 except that the addition time was before starting the vibration mill pulverization, at the start of the ball mill pulverization, and one hour before the end of the ball mill pulverization. Each sample was obtained in the same manner as in Example 1 except that this was fired at 1200 to 1240 ° C. The average particle size of the fine powder in the molded body is the average particle size of 0.2 μm added before starting the vibration mill pulverization, the average particle size of 0.2 μm added at the start of ball mill pulverization, and the average particle size of 0.2 μm added after the ball mill pulverization. One hour before the addition, the average particle size was 0.3 μm. The average particle size of the magnetic oxide (calcined) particles in the compact was 0.5 μm. FIG. 4 shows the sintering density and magnetic orientation (Ir / I
s).

As is apparent from FIG. 4, the degree of orientation decreases as the timing of addition decreases.

Example 5 (Calcination Temperature of Oxide Particles)
° C, 1275 ° C, 1300 ° C, and α-Fe ₂ O ₃ (iron oxide by Lusner method, average particle size: 0.3 µm, specific surface area 2.6 m ² / g) as fine powder to be added. A molded body was produced in the same manner as in Example 1 except that
Each sample was obtained in the same manner as in Example 1 except that the sample was fired. The average particle size of the fine powder in the compact is 0.2 μm
Met. The average particle diameter of the oxide magnetic material (calcined body) particles in the molded product was determined at a calcining temperature of 1200 ° C.
4 μm, 1250 ° C., 0.5 μm, 1300 ° C., 0.9 μm. FIG. 5 shows the relationship between the density at each calcination temperature and the degree of magnetic orientation (Ir / Is) of these samples.

As apparent from FIG. 5, except for the 1300 ° C., the higher the calcination temperature, the higher the magnetic orientation.

Example 6 (Addition of calcium gluconate)
Amount) An attritor was blended with the raw material so that SrFe ₁₂ O ₁₉ was obtained. At that time, in addition to this composition, SiO ₂ : 0.2% by weight, CaCO ₃ :
0.15% by weight was added. After pulverization, the powder was dried and sized, and calcined in air at 1250 ° C. for 3 hours to obtain a granular calcined body.

When the calcined powder thus obtained is expressed as Sr _{1 -x} La _x Fe _{12 -x} Co _x O ₁₉ , La ₂ (C
_{O 3) 3 · 8H 2 O} , CoO x (CoO + Co 3 O 4) + Si
O ₂ : 20.4% by weight, CaCO ₃ : 31.25% by weight
Was added. Further, calcium gluconate: 0.03
% By weight, 0.6% by weight, 0.9% by weight, 1.2% by weight,
After adding 1.5% by weight and 1.8% by weight, respectively, the resultant was coarsely pulverized for 20 minutes by a vibrating rod mill. Then α
-Fe ₂ O ₃ (iron oxide by Lusner method, average particle size: 0.1
3 μm, specific surface area 2.6 m ² / g)
0.3 volume% was added, and the obtained pulverized powder was wet-pulverized in water by a ball mill for 40 hours to obtain a molded product. Each sample was obtained in the same manner as in Example 1 except that this was fired at 1200 to 1240 ° C. The average particle size of the fine powder in the molded product was 0.2 μm. The average particle size of the magnetic oxide (calcined) particles in the compact was 0.5 μm. FIG. 6 shows the relationship between the amount of calcium gluconate added and the degree of orientation of the compact. FIG. 7 shows the relationship between the amount of calcium gluconate added and the degree of magnetic orientation at different firing temperatures. FIG. 8 shows the HcJ-Br characteristics according to the amount of calcium gluconate added.

When 1.2% by weight or more of calcium gluconate was added, cracks occurred in the sintered body. FIG.
As is clear from the above, if the added amount of gluconic acid is 0.3% by weight or less, a sufficient degree of orientation cannot be obtained, and to obtain a higher degree of orientation, 0.6 to 1.2% by weight must be added. It is.
As apparent from FIG. 7, the amount of calcium gluconate added was 0.9 to 1.2% by weight, reflecting the degree of orientation of the molded body.
, The degree of orientation of the sintered body is maximum. As is apparent from FIG. 8, Br is maximized when the amount of calcium gluconate added is 0.9 or 1.2% by weight, reflecting the degree of magnetic orientation.

Example 7 (Addition of fine Sr ferrite particles
In addition , the raw materials were compounded in an attritor so that SrFe ₁₂ O ₁₉ was obtained. At that time, in addition to this composition, SiO ₂ : 0.2% by weight, CaCO ₃ :
0.15% by weight was added. After pulverization, the powder was dried and sized, and calcined in air at 1250 ° C. for 3 hours to obtain a granular calcined body.

The calcined powder obtained was calcined at 1100 ° C. and 1150 ° C. for 3 hours with the same composition as above, 30% by weight, SiO ₂ : 20.4% by weight,
CaCO _3: 31.25 wt%, calcium gluconate: by adding 0.9 wt% were coarsely pulverized by a small vibration mill. The average primary particle size of the calcined powder was about 0.4 μm when calcined at 1100 ° C., and was about 0.4 μm even when calcined at 1150 ° C. Thereafter, pulverization was carried out in water in the same manner as in Example 1, and calcination was performed to obtain each sample. FIG. 9 shows the relationship between the density and the degree of magnetic orientation for each of the added low-temperature calcined materials.

As is clear from FIG. 9, the degree of orientation was improved by firing at a lower temperature than the normal calcination temperature in the case of producing Sr ferrite, even when fine calcined powder was added. In addition, both of the calcined material for addition at 1100 ° C. and 1150 ° C. and the calcined material at 1250 ° C. confirmed that SrM type ferrite was generated by X-ray diffraction.

Example 8 A molding slurry was prepared in the same manner as in Example 6 except that the amount of calcium gluconate added was 0.6% by weight. At this time, the slurry at the time of ball mill pulverization was collected, air-dried on a sample stage, and then SEM-EDS
And the component analysis of each particle was performed. FIG. 10 shows an SEM photograph of this sample.

From FIG. 10 and the analysis results, the added fine α-Fe ₂ O ₃ particles are not aggregated with each other,
It was found that Sr ferrite particles were scattered on the surface. Similar results were observed by SEM-EDS analysis of the molded product.

From the above results, the mechanism by which the degree of orientation is improved by the addition of fine particles is that the added particles are present in a state of being dispersed on the surface of ferrite particles, whereby ferrite aggregation is prevented, and as a result, the degree of orientation is reduced. It can also be considered an improved one.

Comparative Example 2 In Example 1, as polycarboxylic acid ammonium salt type dispersant, SN Dispersant 5468 manufactured by Sannobuco Co., Ltd. and SN dispersant manufactured by Sannobuco Co., Ltd .: SN
Dispersant 2X4150 polymer type dispersant,
1.0% by weight and 1.0% by weight, respectively, based on the calcined composition
A sintered body sample was obtained in the same manner as in the example, except that it was added. Similarly, a sample to which no dispersant was added and calcium gluconate was added was also prepared. FIG. 11 shows the relationship between the amount of iron oxide fine powder particles added and the degree of orientation in each dispersant.

As is apparent from FIG. 11, the sample using the polymer type dispersant outside the present invention as an additive tended to have a lower orientation degree.

Example 9 In the above Example 1, when the dispersant was a sugar having a carboxyl group, a derivative thereof, or an organic compound which is a salt thereof, those exemplified above were used. It was confirmed that the effect was obtained.

The effects of the present invention are clear from the results of the above examples.

[0100]

As described above, according to the present invention, in the process of manufacturing an oxide magnetic material such as an anisotropic ferrite magnet, the magnetic field orientation during wet molding using water is advantageous in terms of environment and cost. By improving the properties, an oxide magnetic material having high characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of post-addition and the degree of orientation of a molded article.

FIG. 2 is a diagram showing the relationship between the amount of fine powder and the degree of orientation for each type of fine powder to be added.

FIG. 3 is a diagram showing the relationship between the amount of fine powder and the degree of orientation for each size of fine powder to be added.

FIG. 4 is a diagram showing the relationship between the density of each sample and the degree of magnetic orientation (Ir / Is) at each addition time.

FIG. 5 is a diagram showing the relationship between the density at each calcination temperature and the degree of magnetic orientation (Ir / Is) of each sample.

FIG. 6 is a graph showing the relationship between the amount of calcium gluconate added and the degree of orientation of a molded article.

FIG. 7 is a graph showing the relationship between the amount of calcium gluconate added and the degree of magnetic orientation at different firing temperatures.

FIG. 8: HcJ-Br by amount of calcium gluconate added
FIG. 4 is a diagram showing characteristics.

FIG. 9 is a diagram showing the relationship between the density and the degree of magnetic orientation for each low-temperature calcined material added.

FIG. 10 is a drawing-substituting SEM photograph showing the particle shape of slurry during ball mill pulverization.

FIG. 11 is a diagram showing the relationship between the amount of iron oxide fine powder particles added and the degree of orientation in each dispersant.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazumasa Iida 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (14)

[Claims] 1. A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing magnetic oxide particles, water and a dispersant in a magnetic field to obtain a molded body, The dispersant is an organic compound having a hydroxyl group and a carboxyl group, or a neutralized salt thereof or a lactone thereof, an organic compound having a hydroxymethylcarbonyl group, or an organic compound having an enol-type hydroxyl group that can be dissociated as an acid. A compound or a neutralized salt thereof, wherein the organic compound has 3 to 20 carbon atoms, and a hydroxyl group is bonded to 50% or more of carbon atoms other than a carbon atom double-bonded to an oxygen atom; Fine powder is further added to the material, the average particle size of the fine powder in the compact is smaller than the average particle size of the oxide magnetic material, and the fine powder is based on the oxide magnetic material particles. 1 to Method for producing an anisotropic oxide magnetic body 00 is added vol%. 2. The method according to claim 1, wherein the fine powder in the compact has an average particle size of 0.01 to 2 μm. 3. The method for producing an anisotropic oxide magnetic material according to claim 1, wherein the fine powder contains a ferrite constituent element. 4. The method according to claim 1, wherein the organic compound having a hydroxyl group and a carboxyl group is gluconic acid. 5. The organic compound having an enol-type hydroxyl group that can be dissociated as an acid is ascorbic acid.
3. The method for producing an anisotropic oxide magnetic material according to any one of items 1 to 3. 6. A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing magnetic oxide particles, water and a dispersant in a magnetic field to obtain a molded body, The dispersant is citric acid or a neutralized salt thereof, and fine particles are further added to the molding material, and the average particle diameter of the fine powder in the molded body is larger than the average particle diameter of the oxide magnetic material. Small and 1 to 1 with respect to the oxide magnetic particles.
A method for producing an anisotropic oxide magnetic material in which 100% by volume is added. 7. The method for producing an anisotropic oxide magnetic material according to claim 1, wherein a basic compound is added to the molding material. 8. The method for producing an anisotropic oxide magnetic material according to claim 1, wherein the dispersant is a calcium salt. 9. The method for producing an anisotropic oxide magnetic material according to claim 1, further comprising a wet pulverizing step before said forming step. 10. The method for producing an anisotropic oxide magnetic material according to claim 9, wherein at least a part of the dispersant is added in the wet grinding step. 11. The method for producing an anisotropic oxide magnetic material according to claim 9, further comprising a dry coarse pulverization step before the wet powder step. 12. The method according to claim 1, wherein at least a part of the dispersant is added in the dry coarse pulverization step.
1. The method for producing an anisotropic oxide magnetic material according to 1. 13. The amount of the dispersant added (when the dispersant can be ionized in an aqueous solution, the amount in terms of ions) is 0.05 to the oxide magnetic particles.
The method for producing an anisotropic oxide magnetic material according to any one of claims 1 to 12, wherein the amount is from 3.0 to 3.0% by weight. 14. A method for producing an anisotropic oxide magnetic material, comprising a molding step of molding a molding material containing oxide magnetic material particles, water and a dispersant in a magnetic field to obtain a molded product, The dispersing agent is a saccharide having a carboxyl group or a derivative thereof, or an organic substance which is a salt thereof. Fine powder is further added to the molding material, and the average particle size of the fine powder in the molded body is The diameter is smaller than the average particle diameter of the oxide magnetic substance, and 1 to 1 with respect to the oxide magnetic substance particles.
A method for producing an anisotropic oxide magnetic material in which 100% by volume is added.