JP2668334B2 - Permanent magnet, manufacturing method thereof, and permanent magnet material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide permanent magnet manufactured by a dry forming method, a method of manufacturing the same, and a permanent magnet material used in the manufacturing method.

[0002]

2. Description of the Related Art Anisotropic oxide permanent magnets of magnetoplumbite such as Sr ferrite and Ba ferrite are known. Such an oxide permanent magnet is manufactured by molding in a magnetic field and then sintering. Generally, in a molding apparatus, a molding space is composed of a mold, an upper punch and a lower punch, and pressure is applied by moving the upper punch or the lower punch. The molding method is roughly classified into a dry molding method and a wet molding method, and those having high magnetic properties are usually produced by a wet molding method.

In the wet molding method, a slurry in which a permanent magnet material composed of oxide permanent magnet material particles is suspended in a dispersion medium such as water is pressure-fed and filled into the molding space of a molding apparatus, and is pressed in a magnetic field. Molding is performed while removing the dispersion medium from the space. In the wet molding method, since the permanent magnet material particles are easily rotated, the orientation is good and high characteristics are obtained, but since the dispersion medium needs to be discharged to the outside of the molding space during the pressure molding, the productivity becomes low, Further, the mold structure becomes complicated and the device becomes large.

On the other hand, in the dry molding method, a permanent magnet material that has been dried is filled in a molding space and molded in a magnetic field. The dry molding method is inferior to the wet molding method in the orientation, but the cost is low because the productivity is high and the configuration of the apparatus is simple.

It is considered that the reason why the degree of orientation is reduced in the dry molding method is due to contact friction between particles when the permanent magnet material is pressed. Further, since a frictional force acts between the particles and the mold, the consolidation action by pressurization is insufficient, and the moldability is reduced. For this reason, various proposals have been made to add a low friction lubricant to the permanent magnet material in the dry molding method.

For example, in Japanese Patent Publication No. 60-22484, magnesium stearate is mixed as a binder,
It has been proposed to dry-press under a magnetic field. However, with this method, it is difficult to uniformly apply magnesium stearate to the surface of each particle. For this reason,
The amount of addition must be increased, and the amount of carbon in the magnet after sintering increases, so that high magnetic properties cannot be obtained.

Further, in JP-A-62-176102, it is difficult to uniformly mix when a solid binder is used, and the surface of the particles is coated with a binder in a gas phase by heating or depressurizing. A proposal has been made. However, this method requires a large scale of equipment and is time-consuming and troublesome.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to remarkably improve the orientation and formability by a simple method when producing an oxide permanent magnet by utilizing dry forming.

[0009]

The above objects are achieved by the present invention described in (1) to (20) below. (1) A carboxylate or a carboxylate and another anionic surfactant in a water slurry of a raw material powder composed of magnetoplumbite-type oxide permanent magnet material particles containing at least one of strontium and barium. And / or a nonionic surfactant is contained as a surfactant and then dried to obtain a permanent magnet material comprising oxide permanent magnet material particles having the surfactant adsorbed on the surface thereof, Using a dry molding apparatus in which a molding space is formed by at least a mold, an upper punch and a lower punch, a step of dry molding the permanent magnet material in a magnetic field to obtain a molded body, and sintering the molded body The residual magnetization Br is 4000 G or more and the coercive force Hcj
Wherein the magnetoplumbite-type permanent magnet having a particle size of 2800 Oe or more is obtained. (2) The method for producing a permanent magnet according to the above (1), wherein the carboxylate is a polycarboxylate. (3) The method for producing a permanent magnet according to the above (2), wherein the polycarboxylate is a salt of a copolymer of an unsaturated hydrocarbon and a lower unsaturated carboxylic acid. (4) The method for producing a permanent magnet according to any one of the above (1) to (3), wherein the other anionic surfactant contains a low molecular weight polyolefin wax. (5) The method for producing a permanent magnet according to any one of (1) to (4), wherein the nonionic surfactant contains a polyoxyalkylene compound. (6) The method for producing a permanent magnet according to any one of (1) to (5), wherein the carboxylate is added to the slurry in the form of an aqueous solution. (7) The method for producing a permanent magnet according to (6), wherein an aqueous solution or emulsion of the anionic surfactant and / or nonionic surfactant is added to the aqueous solution of the carboxylate. (8) The specific surface area of the oxide permanent magnet material particles is 5 m ^2.
/ G or more, the method for producing a permanent magnet according to any one of the above (1) to (7). (9) dry-molding a permanent magnet material in which a plurality of the oxide permanent magnet material particles are combined and granulated;
The method for producing a permanent magnet according to any one of (8). (10) The method for producing a permanent magnet according to any one of the above (1) to (9), wherein the relative density of the molded body is 54 to 69%. (11) After forming the compact, the mold is moved relative to the upper and lower punches while maintaining the pressurization by the upper punch and the lower punch to discharge the gas in the compact, and then the upper punch and the lower Releasing the pressure applied by the punch (1)-
(10) The method for producing a permanent magnet according to any of (10). (12) Using the dry molding apparatus in which at least one of the punches has an exhaust hole opened on the surface facing the molding space, (1)
The method for producing a permanent magnet according to any one of (11) to (11). (13) In order to prevent the permanent magnet material from entering the exhaust hole, a dry molding apparatus provided with a gas permeable filter so as to cover at least the exhaust hole is used (12).
Of manufacturing permanent magnets. (14) The method for producing a permanent magnet according to the above (12) or (13), wherein a dry molding apparatus provided with an intake unit for inhaling gas in the molding space from the exhaust hole is provided. (15) One punch has a configuration in which molding is performed without intruding into the mold, the surface of the one punch facing the molding space is covered with a breathable filter, and the breathable filter has a vent passage. The method for producing a permanent magnet according to any one of the above (1) to (14), wherein the dry molding device forming the permanent magnet is used. (16) The method for producing a permanent magnet according to the above (15), wherein a dry molding apparatus having an exhaust hole on a surface of at least one punch facing the molding space is used. (17) A permanent magnet having a degree of orientation of 91% or more, which is a value obtained by dividing the residual magnetization in the orientation direction by the saturation magnetization, (1)
A method for manufacturing a permanent magnet according to any one of (16) to (16). (18) A permanent magnet material, which is used in any one of the methods (1) to (17). (19) A magnetoplumbite-type oxide permanent magnet containing at least one of strontium and barium, which is produced by a dry molding method and has a residual magnetization Br of 40.
A permanent magnet having a coercive force Hcj of at least 00 G and at least 2800 Oe. (20) The permanent magnet according to (19), wherein the degree of orientation, which is a value obtained by dividing residual magnetization in the orientation direction by saturation magnetization, is 91% or more.

[0010]

In the present invention, an aqueous solution of a surfactant essentially containing a carboxylate is added to a water slurry of a raw material powder composed of oxide permanent magnet material particles. Since the surface of the oxide permanent magnet material particles is hydrophilic, the functional group portion of the carboxylate surfactant quickly adsorbs to the particle surface. Then, the powder is dried to obtain a permanent magnet material composed of oxide permanent magnet material particles in which the surfactant is uniformly adsorbed on the surface. Since the surface of the particles has extremely low friction, the contact friction between the particles during molding is extremely small, and the orientation is significantly improved.

In dry molding, when the particle diameter is reduced to improve the magnetic properties, especially when the specific surface area is made 5 m ² / g or more,
The friction between the particles and the friction between the particles and the mold become extremely large, and the consolidation action by pressurization becomes insufficient, so that good moldability cannot be obtained. However, in the present invention, since the friction on the surface of the particles is small, the moldability is good.

However, in the present invention, since the surface active agent containing a carboxylate salt is very uniformly adsorbed on the particle surface and the affinity between a gas such as air and the particle surface is high, the molding is started. The gas that was sometimes present in the molding space is difficult to escape during pressurization. Therefore, a relatively large amount of gas is sealed in the molded body after the completion of molding. Therefore, a force that expands acts on the molded body, and a crack may be generated by rubbing with the mold when releasing the molded body, and in some cases, the molded body is divided by explosive cracks. Sometimes.

In order to prevent the occurrence of such cracks, it is effective to use a surfactant essentially containing a carboxylate and a low molecular weight polyolefin wax. Carboxylate has a high friction reducing effect on the surface of particles, while low molecular weight polyolefin wax has a high effect of increasing the cohesive force between particles at the time of pressurization and increasing the binding force between particles. Thereby, the orientation of the molded body is improved, and the occurrence of cracks can be prevented. In addition, the nonionic surfactant can also prevent the molded article from cracking by the same action as the low molecular weight polyolefin wax. The nonionic surfactant has almost no effect on the low friction of the particle surface due to the anionic surfactant.

Further, in the present invention, compression molding is performed while discharging at least a part of the gas contained in the molding space,
After compression molding, cracks can also be prevented by releasing at least a part of the gas in the molded body and then releasing the molded product. Specifically, it is preferable to use at least one of the following methods.

[0015] The shape retention force is increased by increasing the density of the compact during molding.

The particles adsorbed with a surfactant essentially containing a carboxylate are granulated and molded to facilitate the discharge of gas in the molding space.

When the compact is pressed by the upper punch and the lower punch, the mold is moved relatively to the press. In this case, the side surface of the molded body may be exposed from the mold, and the gas in the molded body may be exhausted from the side surface.The upper punch may be raised to near the upper edge of the mold, or the lower punch may be moved to the mold. , The gas in the compact may be exhausted from the gap between the mold and the punch.

The punch is provided with an exhaust hole, or a permeable filter is provided between the punch and the mold, and compression molding is performed while discharging gas in the molding space from the exhaust hole and the permeable filter.

As described above, according to the present invention, high orientation and moldability can be obtained by an extremely simple method, so that a high-performance permanent magnet can be manufactured with high productivity.

[0020]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The method for manufacturing a permanent magnet according to the present invention includes a permanent magnet material manufacturing step, a forming step, and a sintering step in this order.

<Permanent Magnet Material Manufacturing Process> The permanent magnet material of the present invention is composed of oxide permanent magnet material particles having a surface-active surface of a surfactant containing a carboxylate as an essential component. The permanent magnet material manufacturing step includes a step of adding a surfactant essentially containing a carboxylate to an aqueous slurry of the raw material powder, preferably in the form of an aqueous solution.

The raw material powder is a powder composed of oxide permanent magnet material particles, that is, a powder which becomes an oxide permanent magnet by molding and sintering, and is usually a calcined product of starting materials such as various oxides and hydroxides. Is obtained by crushing. If this pulverization is performed in a wet manner using water, a water slurry of the raw material powder is obtained. However, after performing dry pulverization, it may be mixed with water to form a slurry. The concentration of the raw material powder in the water slurry is not particularly limited, but is usually about 10 to 50% by weight.

The smaller the particle size of the magnetic material particles, that is, the larger the specific surface area of the raw material powder, the greater the effect of the present invention is. In the case where the specific surface area is 5 m ² / g or more, particularly 6 m ² / g or more. The effects of the present invention are remarkable. The upper limit of the specific surface area is usually about 9 m ² / g. The average particle size of the raw material powder measured by the air permeation method is 0.8 to 1.
It is about 2 μm.

[0025]

As the carboxylate as a surfactant, it is preferable to use a polycarboxylate. As the polycarboxylate, a salt of a copolymer of an unsaturated hydrocarbon and a lower unsaturated carboxylic acid, for example, an ammonium salt or a sodium salt is preferable. Examples of unsaturated hydrocarbons include ethylene, propylene, butene, pentene, hexene, styrene, propenylbenzene, stilbene, vinylnaphthalene, and the like, and examples of lower unsaturated carboxylic acids include acrylic acid, maleic acid, and methacrylic acid. Examples include acids, isocrotonic acid, itaconic acid, citraconic acid, allylmalonic acid, glutaconic acid, tiglic acid, vinylacetic acid, atropic acid, benzoylacrylic acid and the like. The lower unsaturated carboxylic acid is also used as an ester. Among them, especially HLB (hydrophilic lipophilic balance) is 2
The effect is remarkable although the polymerization is performed so as to be 5 or less.

Further, even when a monocarboxylate is used, the effect is large, and another anionic surfactant such as a sulfonate can be used. As the monocarboxylate, specifically, for example, ammonium stearate,
Sodium stearate, potassium stearate, aluminum stearate, ammonium hydrogen stearate, ammonium oleate, sodium oleate,
Those containing at least one kind of saturated or unsaturated fatty acid salt having about 10 to 30 carbon atoms, such as potassium oleate, are preferable.

Incidentally, two or more carboxylate salts may be used in combination as a surfactant.

In the present invention, it is preferred to use a carboxylate anionic surfactant in combination with a low molecular weight polyolefin wax as another anionic surfactant. By adding low molecular weight polyolefin wax,
As described above, the occurrence of cracks in the molded body can be prevented. The anionic low molecular weight polyolefin-based wax (oxidized polyolefin-based wax) used in the present invention preferably has an acid value of 5 to 50, more preferably 15 to 35,
The average molecular weight is preferably 1,000 to 10,000, more preferably 2,000 to 6,000. The number of carbon atoms of the raw material monomer is preferably about 2 to 3.

In the present invention, a nonionic surfactant may be used in some cases. As such a nonionic surfactant, it is preferable to use at least a polyoxyalkylene compound. Examples of the polyoxyalkylene-based compound include polyoxyalkylene, polyoxyalkylene ester, and polyoxyalkylene ether, and polyoxyalkylene is particularly preferred. As the polyoxyalkylene, those obtained by polymerizing ethylene glycol and / or propylene glycol are preferable, and particularly, the molar ratio of ethylene glycol is 0.2 to
A value of 0.8 is preferred. The average molecular weight of the polyoxyalkylene compound is preferably from 1,000 to 2,500.
It is 0, more preferably 3000 to 20000. Specifically, it is preferable to use at least one of polyethylene glycol and polyoxyalkylene represented by the following chemical formula 1.

[0031]

Embedded image

In the above formula 1, a + b + c = 1, and
It is preferable that a + c is 0.2 to 0.8.

[0033] Two or more nonionic surfactants may be used in combination.

The amount of the carboxylate surfactant to be added is preferably 0.1 to 2.0 parts by weight based on 100 parts by weight of the raw material powder. Especially for monocarboxylates,
The effect of the present invention is remarkable when 1.5 parts by weight and 0.3 to 1.0 parts by weight of polycarboxylic acid salt are added. When a low-molecular-weight polyolefin-based wax is used in combination, the amount of the low-molecular-weight polyolefin-based wax to be added is preferably 0.1 to 0.8 parts by weight based on 100 parts by weight of the raw material powder. Further, the amount of the nonionic surfactant added to 100 parts by weight of the raw material powder is preferably 0.1 to 0.8 parts by weight. In any of the carboxylate, other anionic surfactants and nonionic surfactants, if the amount added is less than the above range, the effect of the addition is insufficient. The carbonization of the organic material at the time of binding lowers the density and deteriorates the magnetic characteristics.

The carboxylic acid salt, other anionic surfactants and nonionic surfactants are made into an aqueous solution, or if they are not water-soluble, they are made into an aqueous solution such as an emulsion, and then added to an aqueous slurry of the raw material powder. Is added to Of these, the carboxylic acid salt can be an aqueous solution, as shown in Examples described later. The concentration of the carboxylate, the anionic surfactant, and the concentration of the nonionic surfactant in the aqueous solution or emulsion are not particularly limited, but are preferably 50% by weight or less. This is when the concentration is such that it can be quickly dispersed in the water slurry when an aqueous solution or emulsion is added,
This is because the uniform adsorption effect is remarkable.

After adding the carboxylate salt and, if necessary, other anionic surfactant and / or nonionic surfactant, the slurry is dried. There is no particular limitation on the drying means, the temperature during drying, the carboxylate used,
The temperature is set lower than the decomposition temperature of other anionic surfactants and nonionic surfactants.

<Molding Step> In the molding step, a permanent magnet material is dry-molded in a magnetic field using a dry molding apparatus in which a molding space is formed by at least a mold, an upper punch and a lower punch to form a molded body. obtain.

The method of dry molding is not particularly limited, but when a permanent magnet material having a carboxylate adsorbed therein is molded, gas is easily trapped in the molded body as described above. Therefore, the following method is used. Preferably, molding is performed.

First Method In the first method, the dry molding is performed by increasing the density of the molded body. Usually, the oxide permanent magnet material particles have a high friction between particles and a high friction between the particles and the mold, so that it is difficult to increase the density of the compact. For example, it is possible to manufacture a molded body having a density of 3 g / cm ³ during the manufacture of an Sr ferrite magnet, but the life of the mold becomes extremely short. However, in the present invention, since the friction on the particle surface is low, the compaction action by pressurization is improved, and the relative density (measured density / theoretical density) is 5%.
4 to 69% (2.8 to 3.5 in terms of Sr ferrite magnet)
A molded body of g / cm ³ ) can be easily obtained. In a compact having a high density, the distance between the material particles becomes small, and the contact area between the particles becomes large. As a result, the adhesion is improved and cracks are prevented. When a low molecular weight polyolefin wax is added as another anionic surfactant in addition to the carboxylate, or when a nonionic surfactant is added, the cohesive force increases and the adhesion between particles improves. However, since the cohesive force and the adhesive force are further improved by increasing the density of the molded body, the crack prevention effect is remarkably enhanced. If the relative density of the molded body is less than 54%, the expansive force of the gas in the molded body may be larger than the consolidation force between the particles to cause cracks, and if it exceeds 69%, the orientation may be deteriorated. There is.

Second Method In the second method, a plurality of oxide permanent magnet material particles are combined and granulated, and then dry-molded. Granulation is usually carried out by wet-molding a water slurry after adding a carboxylate and, if necessary, the above-mentioned other anionic surfactant or nonionic surfactant in a magnetic field to obtain a molded product. Is crushed to an appropriate particle size and sized. However,
When an anionic surfactant such as a low HLB carboxylate is added, the orientation may be deteriorated in wet molding. Therefore, in order to obtain a higher orientation, it is necessary to perform the molding in a magnetic field during granulation. It is preferable that a wet method or a dry method is appropriately selected and used. The average particle size of the granules is 50-30
Preferably, the thickness is about 0 μm.

Third Method In the third method, after the molded body is formed, the mold is moved relative to the molded body while maintaining the pressure applied by the upper punch and the lower punch. The gas inside is discharged, and then the pressure applied by the upper punch and the lower punch is released. As described above, in this method, the gas may be discharged from the side surface of the molded body, or the gas may be discharged from the gap between the mold and the punch. As described above, when the pressure in the hard axis direction is released while the expansion in the easy axis direction is suppressed, the layer crack does not occur.

Fourth Method In the fourth method, dry molding is performed while exhausting gas in the molding space through an exhaust port of the punch or a gas permeable filter provided between the punch and the raw material powder.

FIG. 1 shows a partial cross-sectional view of an example of the dry molding apparatus used in the fourth method. In the dry molding apparatus shown in the figure, a molding space 5 is formed by a mold 2, an upper punch 3 and a lower punch 4, and the upper punch 3 and the lower punch 4 are formed.
Exhaust holes 31 and 41 are provided on the surfaces facing the respective molding spaces 5.
Are opened, and these exhaust holes communicate with the outside of the apparatus.

The diameter and arrangement density of the exhaust port are not particularly limited. For example, when the permanent magnet material in the molding space 5 is fine, it is more difficult for gas to escape from the molding space. Therefore, the density of exhaust holes should be relatively high. Usually, it is preferable that the diameter of the exhaust hole is about 0.1 to 2 mm. If the diameter of the exhaust hole is too small, the escape of gas from the molding space becomes worse, and if the diameter is too large, a large amount of the permanent magnet material may enter the exhaust hole. Although the density of the exhaust holes is not particularly limited, it is generally preferable to be about 1 to 4 holes / cm ² .

Since ordinary permanent magnet materials are magnetically aggregated and have low fluidity, even if the diameter of the exhaust hole is not set smaller than the particle size, the permanent magnet material hardly penetrates into the exhaust hole. Since the permanent magnet material of the present invention has high dispersibility and improved fluidity, it is preferable to prevent the permanent magnet material from entering the exhaust holes by providing a breathable filter so as to cover at least the exhaust holes. As the air-permeable filter, cloth, paper, or the like can be used, and fine holes may be formed in these as necessary. Alternatively, a perforated resin film may be used.

As described above, the exhaust hole may be provided in only one of the upper punch and the lower punch, but is preferably provided in both punches.

When the punch moves and the compression of the permanent magnet material is started, the gas in the molding space is discharged from the exhaust hole. The gas may be forcibly exhausted.

In the present invention, the upper punch may be moved or the lower punch may be moved during compression molding. Further, the molding may be performed without at least one punch penetrating into the mold.

In the present invention, since molding in a magnetic field is performed, a coil (not shown) for generating a magnetic field is usually provided on the mold 2.
Is wound.

FIG. 2 shows a partial sectional view of another example of the dry molding apparatus used in the fourth method. This apparatus has a structure in which molding is performed without the upper punch 3 penetrating into the mold 2, and compression molding is performed by lowering the mold 2 and the upper punch 3 or raising the lower punch 4. In this device, the surface of the upper punch 3 facing the molding space 5 is covered with a breathable filter 6, and this breathable filter 6 forms a ventilation path. That is, the gas in the molding space 5 is discharged to the outside of the apparatus through the breathable filter 6.

The material used for the air permeable filter 6 is not particularly limited as long as gas can move in a direction perpendicular to the thickness direction (in-plane direction), but usually, cloth or paper is preferably used. . The thickness of the gas permeable filter 6 is not particularly limited, but is preferably about 0.1 to 1 mm in order to efficiently discharge gas.

It is also possible to adopt a configuration in which the lower punch does not enter the mold. In this case, the breathable filter is provided between the lower punch and the mold.

In the embodiment shown in FIG. 2, the permanent magnet material adheres to the gas permeable filter 6 at the time of molding, causing clogging.
Further, when the breathable filter is used in the mode in which the exhaust holes are provided, the breathable filter is also clogged. For this reason, it is preferable to replace the breathable filter in a timely manner. As shown in FIG. 2, the upper punch 3 has a mold 2
In the structure that does not enter inside, a long air-permeable filter can be wound around two rolls, one roll being a pay-out roll, and the other roll being a take-up roll, which can be rotated at a suitable time. This eliminates the need to interrupt the work for replacing the breathable filter.

When a gas permeable filter is used, a transfer pattern of the gas permeable filter is present on a part of the surface of the molded body and the permanent magnet obtained by sintering the compact.

Dry Forming Apparatus The dry forming apparatus used in the present invention is not particularly limited, and the forming space is constituted by a mold, an upper punch and a lower punch, and pressing is performed by moving the upper punch or the lower punch. Any configuration may be used. In the illustrated example, the shape of the molding space is a column shape, but may be another shape such as a cylindrical shape or an arc shape if necessary. When the third method or the fourth method is used, the gas in the molding space may be discharged as described above, and the shape of the molding space is not limited. However, when manufacturing a compact having a relatively small contact area with the punch with respect to the volume, the gas is particularly difficult to escape from the molding space. Therefore, the third method has a particularly high effect in such a case. I do. For example, there is a case where an arc-shaped molded body is manufactured using a device having a molding space in which a mold frame forms an arc-shaped curved surface, or a case where a cylindrical molded body is formed. The first method and the second method exhibit a high effect regardless of the shape and size of the molding space.

According to the present invention, the above-described first to fourth methods are used.
The molding may be performed by combining two or more of the above methods. However, the first method is most preferable because a magnet having high magnetic characteristics can be obtained and productivity is high.

In the present invention, various conditions such as a molding pressure and a magnetic field intensity applied during molding are not particularly limited, and may be appropriately selected from a usual range. However, when the first method is used, the molding pressure is set so that the density of the molded body falls within the range described above.

<Sintering Step> Various conditions in the sintering step for sintering the compact are not particularly limited, and may be appropriately selected from ordinary conditions. For example, while appropriately controlling the oxygen partial pressure in the atmosphere. The temperature may be maintained at 1200 to 1300 ° C. and sintered for 0.5 to 4 hours.

<Permanent Magnet> The oxide permanent magnet manufactured according to the present invention is a magnetoplumbite type anisotropic oxide permanent magnet of Sr ferrite or Ba ferrite. Specifically, MO · nFe ₂ O
₃ (n is preferably one or more of Sr and Ba, n =
5.0 to 6.5). Such ferrites further include Si, Ca, Pb, Al, Ga,
Sn, Zn, In, Co, Ni, Ti, Cr, Mn, C
u, Ge, Nb, Zr, B, P and the like may be contained. In order to set the remanent magnetization Br and the coercive force Hcj in the ranges described below, Si and Ca are preferably contained, and more preferably Al is contained. S
The content of i is 0.1 to 1.0% by weight in terms of SiO _2.
Is preferable, the Ca content is preferably 0.05 to 1.5% by weight in terms of CaO, and
The content of is preferably 2% by weight or less in terms of Al ₂ O ₃ . Each element other than Si, Ca, and Al is 5% by weight in total when converted into oxides.
The following is preferred.

The oxide permanent magnet produced according to the present invention can obtain extremely high magnetic properties even though a dry molding method is used in the production. Specifically, the residual magnetization B
r is 4000 G or more and coercive force Hcj is 280
A Sr ferrite magnet having Oe or more is obtained. Further, a degree of orientation of 91% or more can be obtained. The degree of orientation in this case is a value obtained by dividing residual magnetization in the orientation direction by saturation magnetization.

[0061]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Example 1 100 parts by weight of Sr ferrite calcined powder, 0.5 part by weight of SiO ₂ , and 1 part by weight of C
aCO ₃ was wet-milled with water so that the calcined powder had the specific surface area shown in Table 1 below to obtain a slurry of raw material powder. Then, an aqueous solution of ammonium polycarboxylate was charged into this slurry and stirred for 30 minutes to adsorb ammonium polycarboxylate on the particle surface. Table 1 shows the amount of ammonium polycarboxylate added to 100 parts by weight of the raw material powder. Then, the slurry was dried and then dispersed by an atomizer to obtain a permanent magnet material.

Then, the permanent magnet material was dry-molded in a magnetic field. As shown in FIG. 2, the dry forming apparatus has a configuration in which the upper punch does not enter the mold, and has a configuration in which an exhaust hole is opened in a forming space facing surface of the upper punch.
Further, the gas in the molding space is sucked from the exhaust hole. The molding was performed by lowering the upper punch and the mold. The exhaust holes had a diameter of 1 mm and the arrangement density was 2 holes / cm ² . An air permeable filter (thickness: 0.2 mm) made of paper was provided on the surface of the upper punch opposite to the molding space. Molding pressure is 400kg
f / cm ² .

Next, the compact was fired at 1238 ° C. to obtain a magnet sample having a diameter of about 21 mm and a height of about 10 mm. Table 1 shows the magnetic properties of the magnet samples.

For comparison, the same measurement was performed on a magnet sample obtained by performing the same molding without adsorbing ammonium polycarboxylate. Table 1 shows the results.

[0066]

[Table 1]

Table 1 shows the effect of the present invention. That is, in the sample using the permanent magnet material of the present invention composed of particles to which ammonium polycarboxylate is adsorbed, the residual magnetization Br is 4000 G or more and the coercive force Hcj is 28
At least 00 Oe, an extremely high magnetic property with a degree of orientation of the sintered body of 91% or more was obtained. The degree of orientation was determined by dividing the residual magnetization by the saturation magnetization. The saturation magnetization was obtained at a maximum applied magnetic field strength of 12 kOe.

Example 2 A calcined powder of Sr ferrite was wet-pulverized with water so as to have a specific surface area as shown in Table 2 below to form a slurry. Next, the same operation as in Example 1 was carried out except that ammonium oleate was used instead of ammonium polycarboxylate to obtain a magnet sample having substantially the same shape.

Table 2 shows the magnetic properties of each magnet sample.
For comparison, a similar measurement was performed on a magnet sample obtained by performing similar molding without adsorbing ammonium oleate. Table 2 shows the results.

[0070]

[Table 2]

Table 2 clearly shows the effect of the present invention.
That is, even when a monocarboxylic acid salt is used, it is possible to obtain Br 2800 of 4000 G or more as in the case of the polycarboxylic acid salt.
Hcj of e or more and a degree of orientation of 91% or more are obtained.

<Example 3> In addition to the ammonium polycarboxylate used in Example 1,
A permanent magnet material was produced in the same manner as in Example 1 except that a low-molecular-weight polyolefin-based wax was used. As the low molecular weight polyolefin wax, one having an acid value and an average molecular weight in the more preferable ranges described above was used. Since it is not water-soluble, it was made into an emulsion and added to the slurry. Using these permanent magnet materials,
Dry molding was performed in a magnetic field using the same apparatus as in Example 1 except that the exhaust hole and the air-permeable filter were not provided, to obtain a molded body.

For comparison, a permanent magnet material prepared without adding a low molecular weight polyolefin wax was used to form a molded product in the same manner.

Table 3 shows the amounts of ammonium polycarboxylate and low molecular weight polyolefin wax added to 100 parts by weight of the raw material powder.

Under the conditions shown in Table 3, 50 compacts were manufactured, and the number of cracked compacts was examined.
Table 3 shows the results. The size of the molded body is about 25 mm in diameter.
In the case of a cylinder having a diameter of about 15 mm and a height of about 15 mm and having cracks, the compact was divided by a crack substantially perpendicular to the bottom surface of the compact, and sintering was impossible.

Each compact was fired at 1238 ° C.
A magnet sample of 1 mm and a height of about 11.5 mm was used. Table 3 shows the magnetic properties of the magnet samples.

[0077]

[Table 3]

The effect of the present invention is clear from Table 3. That is, the addition of the low-molecular-weight polyolefin wax drastically reduces the occurrence of cracks in the molded article, and in particular, when 0.3 parts by weight or more is added, no crack is observed.
When the amount of the low-molecular-weight polyolefin wax added is 0.8 parts by weight or less, almost no deterioration of the characteristics of the magnet is observed, and Br of 4000 G or more, Hcj of 2800 Oe or more, and orientation degree of 91% or more are obtained. Have been.

Example 4 A permanent magnet material was produced in the same manner as in Example 3 except that a nonionic surfactant was added instead of the low molecular weight polyolefin wax.
The nonionic surfactant includes polyethylene glycol having a molecular weight in a more preferable range as described above, or a polyoxyalkylene represented by the above formula (1), wherein a +
Those having a preferable range of c were used. Using these permanent magnet materials, dry molding was performed in a magnetic field in the same manner as in Example 3 to obtain a molded body. As a result, polyethylene glycol and the polyoxyalkylene represented by Chemical Formula 1 showed the same effect as the low molecular weight polyolefin wax added in Example 3.

<Example 5> Using the permanent magnet material produced in the same manner as in Example 1 and Example 2, dry molding in a magnetic field was performed in the same manner as in Example 1 to obtain a compact.

For comparison, a molded product was produced using the same apparatus as in Example 1 except that no exhaust hole was provided or no exhaust hole and air-permeable filter were provided.

The specific surface area of the raw material powder, the amounts of ammonium polycarboxylate and ammonium oleate added to 100 parts by weight of the raw material powder, and the pressurizing time during molding were as follows:
It is shown in Table 4 below.

Under the conditions shown in Table 4, 50 compacts were manufactured, and the number of cracked compacts was examined.
Table 4 shows the results. The size of the molded body is about 25 mm in diameter.
In the case of a cylinder having a diameter of 15 mm and a height of about 15 mm, and cracks were generated, cracks (lamination cracks) substantially parallel to the bottom surface of the molded body were generated, and sintering was impossible.

[0084]

[Table 4]

From the results in Table 4, the effect of the present invention is clear.

Example 6 Using the same permanent magnet material as in Example 5, a molded article was manufactured using the apparatus having the structure shown in FIG.

For comparison, a molded product was produced using the same apparatus except that no exhaust hole was provided.

The specific surface area of the raw material powder, the amounts of ammonium polycarboxylate and ammonium oleate added to 100 parts by weight of the raw material powder, and the pressurizing time during molding were as follows:
It is shown in Table 5 below.

Under each condition shown in Table 5, 50 compacts were manufactured, and the number of cracked compacts was examined.
Table 5 shows the results. The size of the molded body is about 30 mm in diameter.
In the case of a cylinder having a diameter of about 15 mm and a height of about 15 mm and having cracks, the compact was divided by a crack substantially perpendicular to the bottom surface of the compact, and sintering was impossible.

[0090]

[Table 5]

From the results in Table 5, the effect of the present invention is clear.

<Example 7> Using a permanent magnet material produced in the same manner as in Example 1 and Example 2, a molded body was manufactured by a device having the configuration shown in FIG. 1 and having no vent hole.

The specific surface area of the raw material powder, the amount of ammonium polycarboxylate and ammonium oleate added to 100 parts by weight of the raw material powder, and the density of the compact are shown in Table 6 below.

Under each condition shown in Table 6, 50 compacts were manufactured, and the number of cracked compacts was examined.
Table 6 shows the results. The size of the molded body is about 30 mm in diameter.
The columnar shape was 15 mm in height and 15 mm in height.

[0095]

[Table 6]

From the results in Table 6, the effect of the present invention is clear. That is, the density of the compact is 2.8 to 3.5 g / cm ^3.
No crack is observed in the range of (relative density 54 to 69%).

An apparatus having the same structure as that shown in FIG. 1 except that it does not have an exhaust hole is used, and only the mold is removed in a state where the molded body is pressurized by the upper punch and the lower punch to remove the gas in the molded body. When the pressurization by both punches was released after discharging from the direction of the hard magnetization axis, no crack was observed in the molded body.

When the raw material powder obtained by orienting and granulating the magnet material particles was used, the magnetic properties were slightly lowered, but no cracks were observed. However, in this case, the magnetic properties were higher than in the case of granulation without adsorbing the carboxylate.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an example of a dry molding apparatus used in the present invention.

FIG. 2 is a partial sectional view showing an example of a dry molding apparatus used in the present invention.

[Explanation of symbols]

 2 Formwork 3 Upper punch 31 Exhaust hole 4 Lower punch 41 Exhaust hole 5 Molding space 6 Air permeable filter

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Junji Nakano 1-1-13 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-2-161701 (JP, A) JP-A-2 JP-A-309607 (JP, A) JP-A-4-313206 (JP, A) JP-A-62-9798 (JP, A) JP-A-4-322408 (JP, A)

Claims (20)

(57) [Claims] 1. A carboxylate salt or a carboxylate salt and other anionic surfactants in a water slurry of a raw material powder consisting of magnetoplumbite-type oxide permanent magnet material particles containing at least one of strontium and barium. Of a permanent magnet material comprising oxide permanent magnet material particles having the surfactant adsorbed on the surface thereof, after containing the agent and / or the nonionic surfactant as a surfactant and then drying. And a step of dry-forming the permanent magnet material in a magnetic field using a dry-forming apparatus in which a forming space is formed by at least a mold, an upper punch, and a lower punch; and The residual magnetization Br is 4000 G or more, and the coercive force Hc
A method for producing a permanent magnet, wherein the magnetoplumbite permanent magnet having j of 2800 Oe or more is obtained. 2. The method according to claim 1, wherein the carboxylate is a polycarboxylate. 3. The method for producing a permanent magnet according to claim 2, wherein the polycarboxylic acid salt is a salt of a copolymer of an unsaturated hydrocarbon and a lower unsaturated carboxylic acid. 4. The method for producing a permanent magnet according to claim 1, wherein the another anionic surfactant is a low molecular weight polyolefin wax. 5. The method for producing a permanent magnet according to claim 1, wherein said nonionic surfactant is a polyoxyalkylene compound. 6. The method according to claim 1, wherein the carboxylate is added to the slurry in the form of an aqueous solution. 7. The aqueous solution or emulsion of the anionic surfactant and / or the nonionic surfactant is added to the aqueous solution of the carboxylic acid salt.
Of manufacturing permanent magnets. 8. The method for producing a permanent magnet according to claim 1, wherein the oxide permanent magnet material particles have a specific surface area of 5 m ² / g or more. 9. The method for producing a permanent magnet according to claim 1, wherein the permanent magnet material in which a plurality of the oxide permanent magnet material particles are combined and granulated is dry-molded. 10. The method for producing a permanent magnet according to claim 1, wherein the relative density of the molded body is 54 to 69%. 11. After forming the molded body, the mold is moved relative to the upper and lower punches while maintaining the pressure by the upper and lower punches to discharge gas from the molded body. The method for manufacturing a permanent magnet according to any one of claims 1 to 10, wherein the pressurization by the and the lower punch is released. 12. The method for producing a permanent magnet according to claim 1, wherein at least one of the punches uses a dry molding apparatus having an exhaust hole opened on a surface facing a molding space. 13. The method of manufacturing a permanent magnet according to claim 12, wherein a dry molding apparatus is used in which a breathable filter is provided so as to cover at least the exhaust hole in order to prevent the permanent magnet material from entering the exhaust hole. . 14. The method for manufacturing a permanent magnet according to claim 12, wherein a dry-type molding apparatus provided with an intake unit for inhaling gas in the molding space from the exhaust hole is used. 15. One of the punches has a structure in which molding is performed without penetrating into a mold, and a surface of the one punch facing a molding space is covered with a breathable filter. The method for manufacturing a permanent magnet according to any one of claims 1 to 14, wherein a dry forming apparatus having an air passage is used. 16. A dry forming apparatus having an exhaust hole on a surface of at least one punch facing a forming space.
Of manufacturing permanent magnets. 17. The method for manufacturing a permanent magnet according to claim 1, wherein a permanent magnet having a degree of orientation of 91% or more, which is obtained by dividing residual magnetization in the orientation direction by saturation magnetization, is obtained. 18. A permanent magnet material used in the method according to claim 1. Description: 19. A magnetoplumbite-type oxide permanent magnet containing at least one of strontium and barium produced by a dry forming method, comprising:
r is 4000 G or more and coercive force Hcj is 280
A permanent magnet characterized by being 0 Oe or more. 20. The permanent magnet according to claim 19, wherein the degree of orientation, which is a value obtained by dividing residual magnetization in the orientation direction by saturation magnetization, is 91% or more.