JP2021141151A - Ferrite powder for bond magnet and production method thereof - Google Patents

Abstract

To provide ferrite powder for a bond magnet, enabling acquisition of a bond magnet having higher remanent magnetization Br by magnetic field orientation, and a production method thereof.SOLUTION: A production method of ferrite powder for a bond magnet comprises the steps of: mixing and granulating powder of a compound oxide of iron, strontium, lanthanum and cobalt with iron oxide (preferably hematite (α-Fe2O3)), calcining the mixture (preferably at 1280-1400°C) and pulverizing the calcined mixture thereby obtaining coarse powder of ferrite (coarse powder preferably having a specific surface area of 0.5-1.0 m2/g); mixing the coarse powder of ferrite with a fine powder of ferrite having a specific surface area larger than that of the coarse powder of ferrite (fine powder preferably having the specific surface area of 5-10 m2/g or further preferably having the specific surface area of 7-9 m2/g); pulverizing the mixture of the coarse powder of ferrite and the fine powder of ferrite and then annealing them (preferably at 880-990°C).SELECTED DRAWING: None

Description

The present invention relates to a ferrite powder for a bonded magnet and a method for producing the same, and more particularly to a ferrite powder for a bonded magnet containing coarse and fine particles of ferrite and a method for producing the same.

Conventionally, ferritic sintered magnets have been used as magnets with high magnetic force such as magnets used in small motors used in AV equipment, OA equipment, automobile electrical components, etc., and magnet rolls in copiers. .. However, the ferrite-based sintered magnet has a problem that the productivity is inferior because chipping cracks occur and polishing is required, and there is a problem that it is difficult to process into a complicated shape.

Therefore, in recent years, rare earth magnet bond magnets have been used as high magnetic force magnets for small motors used in AV equipment, OA equipment, automobile electrical components, and the like. However, rare earth magnets cost about 20 times as much as ferritic sintered magnets and have a problem of being easily rusted. Therefore, it is desired to use ferritic bonded magnets instead of ferritic sintered magnets. There is.

As the ferrite powder for this bonded magnet composition is _{(Sr 1-x A x)} O · n [(Fe 1-y-z Co y Zn z) 2 O 3] ( where, A is La, La-Nd , La-Pr or La-Nd-Pr, n = 5.80 to 6.10, x = 0.1 to 0.5, y = 0.0083 to 0.042, 0 ≦ z <0.0168) It is a magnetoplumbite-type strontium ferrite particle powder having a saturation magnetization value σs of 73 Am ² / kg (73 emu / g) or more and an average particle size of 1.0 to 3.0 μm, and a magnetoplumbite-type strontium ferrite. A strontium ferrite particle powder for a bonded magnet containing 60% or more of plate-like particles in the particle powder has been proposed (see, for example, Patent Document 1).

JP-A-2002-175907 (paragraph number 0025)

However, since the strontium ferrite particle powder for bond magnets of Patent Document 1 contains a large amount of plate-like particles, when the particle powders are aligned in the magnetic field direction by magnetic field orientation, the plate-like particles hinder each other's orientation. Therefore, it has been difficult to produce a bonded magnet having high orientation.

Therefore, in view of such conventional problems, an object of the present invention is to provide a ferrite powder for a bonded magnet and a method for producing the same, which can obtain a bonded magnet having a high residual magnetization Br by magnetic field orientation. ..

As a result of diligent research to solve the above problems, the present inventors have mixed and granulated a powder of a composite oxide of iron, strontium, lanthanum and cobalt and iron oxide, and then fired and pulverized the powder. After crushing a step of obtaining a coarse ferrite powder, a step of mixing the coarse ferrite powder with a fine ferrite powder having a larger specific surface area than the coarse ferrite powder, and a crushing of a mixture of the coarse ferrite powder and the fine ferrite powder. We have found that it is possible to produce a ferrite powder for a bonded magnet, which can obtain a bonded magnet having a high residual magnetization Br by magnetic field orientation, by a method for producing a ferrite powder for a bonded magnet, which includes a step of annealing. Has been completed.

That is, in the method for producing a ferrite powder for a bonded magnet according to the present invention, a powder of a composite oxide of iron, strontium, lanthanum and cobalt and iron oxide are mixed and granulated, then fired and pulverized to form ferrite. A step of obtaining a coarse powder, a step of mixing a ferrite coarse powder and a ferrite fine powder having a larger specific surface area than the ferrite coarse powder, and a step of crushing a mixture of the ferrite coarse powder and the ferrite fine powder and then annealing. It is characterized by having and.

In this method for producing a ferrite powder for a bonded magnet, the composite oxide powder was obtained by mixing strontium carbonate, lanthanum oxide, iron oxide and cobalt oxide, granulating the mixture, and then firing at 1000 to 1250 ° C. It is preferably obtained by crushing the fired product. Further, it is preferable that the composite oxide powder and iron oxide are mixed and granulated, and then calcined at 1280 to 1400 ° C. Further, when the composite oxide powder and iron oxide are mixed, the composite oxide is such that the molar ratio Fe / (Sr + La) of Fe in iron oxide to the total of Sr and La is 4.5 to 11.7. It is preferable to mix the powder of iron oxide with iron oxide. The specific surface area of the coarse ferrite powder ^{is preferably 0.5 to 1.0 m 2} / g. The fine ferrite powder is granulated by mixing strontium carbonate and iron oxide so that the molar ratio Fe / Sr of Fe in iron oxide to Sr in strontium carbonate is 10.0 to 12.5, and then 900 to 900 to It is preferably obtained by pulverizing the fired product obtained by firing at 1000 ° C. Further, when mixing the coarse ferrite powder and the fine ferrite powder, it is preferable that the ratio of the coarse ferrite powder is 60 to 90% by mass.

Also, the ferrite powders for bonded magnet according to the present _{invention, (Sr 1-x La x} ) · (Fe 1-y Co y) n O 19-z ( where, 0 <x ≦ 0.5,0 <y ≦ 0 It has a composition of .04, 10.0 ≦ n ≦ 12.5, −1.0 ≦ z ≦ 3.5), and has a particle size of 1 μm in a volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device. The proportion of particles less than 5 μm is 20 to 40% by volume, the proportion of particles of 1 to 5 μm is 30 to 60% by volume, and the proportion of particles larger than 5 μm is 18 to 30% by volume.

The density of the ferrite powder for the bond magnet when 10 g of the ferrite powder for the bond magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ ^{and then compressed at a pressure of 1 ton / cm 2} is the compression density of the ferrite powder for the bond magnet. The compression density of the ferrite powder for a bonded magnet ^{is preferably 3.70 g / cm 3} or more. Further, 8 g of the above-mentioned ferrite powder for a bond magnet and 0.4 cc of polyester resin are kneaded in a dairy pot, and 7 g of the obtained kneaded product is filled in a mold having an inner diameter of 15 mmφ and compressed at a pressure of ^{2 tons / cm 2 for 60 seconds.} When the coercive force iHc of the green compact obtained by extracting the molded product obtained in the above process from the mold and drying it at 150 ° C. for 30 minutes was measured with a measuring magnetic field of 10 kOe, the coercive force iHc was 1500 Oe or more. Is preferable. Further, the mixer is filled with 92.0 parts by mass of the above-mentioned ferrite powder for a bond magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 6.6 parts by mass of a powdered polyamide resin. The resulting mixture was kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets were placed in a magnetic field of 9.7 kOe at a temperature of 300 ° C. and a forming pressure of 8.5 N / mm ² A cylindrical bond magnet A having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is along the central axis of the column) is produced, and the residual magnetization Br of this bond magnet A is measured with a magnetic field of 10 kOe. It is preferable that the residual magnetization Br is 3270 G or more when measured in. The bonded magnet A, upon measuring the maximum energy product _{BH max} measured magnetic field 10 kOe, the maximum energy product _{BH max} is preferably of at least 2.65MGOe, also ferrite powder 93.5 mass for the above bonded magnet A mixture obtained by filling a mixer with 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 5.1 parts by mass of a powdered polyamide resin and mixing them was prepared at 230 ° C. Kneading is performed to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets are injection-formed in a magnetic field of 9.7 kOe at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² to have a diameter of 15 mm and a height of 8 mm. When a cylindrical bond magnet B (the orientation direction of the magnetic field is along the central axis of the cylinder) is produced and the residual magnetization Br of this bond magnet B is measured with a measurement magnetic field of 10 kOe, the residual magnetization Br is 3410 G or more. It is preferable to have it. The bonded magnet B, upon measuring the maximum energy product _{BH max} measured magnetic field 10 kOe, the maximum energy product _{BH max} is preferably at least 2.80MGOe.

Further, the bonded magnet according to the present invention is characterized by including the above-mentioned ferrite powder for a bonded magnet and a binder.

According to the present invention, it is possible to produce a ferrite powder for a bonded magnet, which can obtain a bonded magnet having a high residual magnetization Br by magnetic field orientation.

In the embodiment of the method for producing a ferrite powder for a bonded magnet according to the present invention, a powder of a composite oxide of iron, strontium, lanthanum and cobalt and iron oxide (preferably hematite (α-Fe ₂ O ₃ )) are mixed. After granulation, it is fired (preferably at 1280 to 1400 ° C.) and pulverized to obtain a coarse ferrite powder (preferably a coarse powder having a specific surface area of 0.5 to 1.0 m ² / g). , A step of mixing the coarse ferrite powder and the fine ferrite powder having a larger specific surface area than the coarse ferrite powder (preferably 5 to 10 m ² / g, more preferably 7 to 9 m ² / g fine powder). , A step of pulverizing a mixture of coarse ferrite powder and fine ferrite powder and then annealing (preferably at 880 to 990 ° C.) is provided. The particle size of the coarse ferrite powder can be increased by using a powder of a composite oxide of iron, strontium, lanthanum, and cobalt and setting the firing temperature when obtaining the coarse ferrite powder to 1280 ° C. or higher. ..

The powder of the composite oxide of iron, strontium, lanthanum and cobalt is granulated by mixing strontium carbonate, lanthanum oxide, iron oxide and cobalt oxide, and then granulated at 1000 to 1250 ° C. (preferably 105 to 1200 ° C., more preferably 105 to 1200 ° C.). Can be obtained by pulverizing a fired product obtained by firing at (1050 to 1150 ° C.).

When the powder of this composite oxide and iron oxide are mixed, the molar ratio Fe / (Sr + La) of Fe in iron oxide to the total of Sr and La is preferably 4.5 to 11.7 (more preferably 9. The composite oxide powder and iron oxide are mixed so as to be 0 to 11.0).

Fine ferrite powder is prepared by mixing strontium carbonate and iron oxide so that the molar ratio of Fe in iron oxide to Sr in strontium carbonate is 10.0 to 12.5, and then granulating the coarse powder. It is preferably obtained by pulverizing the fired product obtained by firing at a temperature lower than the firing temperature (preferably 900 to 1000 ° C.) at the time of obtaining.

When mixing the coarse ferrite powder and the fine ferrite powder, it is preferable that the ratio of the coarse ferrite powder is 60 to 90% by mass. By mixing 60 to 90% by mass of coarse ferrite powder and 10 to 40% by mass of fine ferrite powder, particles having a particle size of less than 1 μm in a volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device. It is possible to obtain a ferrite powder for a bonded magnet having a ratio of 20% by volume or more and a particle ratio of particles larger than 5 μm of 18% by volume or more.

The mixture of the coarse ferrite powder and the fine ferrite powder is pulverized (preferably 10 to 40 minutes, more preferably 15 to 30 minutes) by a wet attritor or the like, and the obtained slurry is filtered. The solid matter thus obtained was dried (preferably in the air at 120 to 180 ° C. for 5 to 20 hours), and the obtained dried cake was used as a medium by a vibrating ball mill and was relatively large (preferably having a diameter of 10 to 15 mm). After milling using balls (preferably 20-40 minutes, more preferably 25-35 minutes), a relatively small ball (preferably 5-10 mm in diameter) is used as a medium by a vibrating ball mill. It can be pulverized by performing a pulverization treatment (preferably for 20 to 40 minutes, more preferably 25 to 35 minutes).

In this _{way, (Sr 1-x La x} ) · (Fe 1-y Co y) n O 19-z ( where, 0 <x ≦ 0.5,0 <y ≦ 0.04,10.0 ≦ A ferrite powder for a bonded magnet having a composition shown by n ≦ 12.5 and −1.0 ≦ z ≦ 3.5) can be produced.

Further, embodiments of the ferrite powder for bonded magnets according to the present _{invention, (Sr 1-x La x} ) · (Fe 1-y Co y) n O 19-z ( where, 0 <x ≦ 0.5 (preferably 0.01 ≦ x ≦ 0.5, more preferably 0.1 ≦ x ≦ 0.5), 0 <y ≦ 0.04 (preferably 0.01 ≦ y ≦ 0.04), 10.0 ≦ It has a composition of n ≦ 12.5 (preferably 10.0 ≦ n ≦ 12.0) and −1.0 ≦ z ≦ 3.5 (preferably −0.5 ≦ z ≦ 3.5). In the volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device, the proportion of particles having a particle size of less than 1 μm is 20 to 40% by volume (preferably 20 to 30% by volume), and the proportion of particles having a particle size of 1 to 5 μm is 30. The proportion of particles larger than 5 μm is 18 to 30% by volume (preferably 18 to 27% by volume). Increase the proportion of particles with a particle size of less than 1 μm and particles larger than 5 μm in ferrite powder for bond magnets (the proportion of particles with a particle size of less than 1 μm is 20% by volume or more and the proportion of particles larger than 5 μm is 18% by volume or more). Thereby, the compression density (CD) of the ferrite powder for the bonded magnet can be set ^{to 3.70 g / cm 3 or more.}

The ferrite powder for a bonded magnet has an average particle size of preferably 1.0 to 2.0 μm, more preferably 1.2 to 1.8 μm, and a specific surface area of preferably 1.0 to ^{2.5 m 2.} / G, more preferably 1.5 to 2.3 m ² / g.

Further, the density of the ferrite powder for the bond magnet when 10 g of the above-mentioned ferrite powder for the bond magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ ^{and then compressed at a pressure of 1 ton / cm 2 is adjusted to the density of the ferrite powder for the bond magnet.} The compression density (CD) of the ferrite powder for a bonded magnet is preferably 3.70 g / cm ³ or more, and more preferably 3.70 to 4.00 g / cm ^{3 when measured as the compression density (CD) of.} ..

Further, 8 g of the above ferrite powder for a bonded magnet and 0.4 cc of polyester resin are kneaded in a dairy pot, and 7 g of the obtained kneaded product is filled in a mold having an inner diameter of 15 mmφ and compressed at a pressure of ^{2 tons / cm 2 for 60 seconds.} The molded product thus obtained was withdrawn from a mold and dried at 150 ° C. for 30 minutes to prepare a green compact. As the magnetic characteristics of this green compact, a BH tracer was used and the green compact was used at a measurement magnetic field of 10 kOe. When the coercive force iHc and the residual magnetization Br of the body are measured, the coercive force iHc is preferably 1500 Oe or more, more preferably 2000 to 4000 Oe, further preferably 2300 to 3500 Oe, and the residual magnetization Br is preferably 1700 to 2200 G. More preferably, it is 1800 to 2050G.

Further, the mixer is filled with 92.0 parts by mass of the above-mentioned ferrite powder for a bond magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 6.6 parts by mass of a powdered polyamide resin. The resulting mixture was kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets were placed in a magnetic field of 9.7 kOe at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² A cylindrical bond magnet A having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is the direction along the central axis of the column) is produced, and the coercive magnetic force iHc and residual magnetism Br of this bond magnet A are produced. When the maximum energy product BH _max is measured with a measurement magnetic field of 10 kOe, the coercive force iHc is 2000 to 2500 Oe, more preferably 2100 to 2350 Oe, the residual magnetization Br is preferably 3270 G or more, and the maximum energy product BH _max is. It is preferably 2.65 MGOe or more, more preferably 2.65 to 2.85 MGOe, and most preferably 2.65 to 2.75 MGOe.

Further, the mixer is filled with 93.5 parts by mass of the above-mentioned ferrite powder for a bond magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 5.1 parts by mass of a powdered polyamide resin. The resulting mixture was kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets were placed in a magnetic field of 9.7 kOe at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm ² A cylindrical bond magnet B having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is the direction along the central axis of the column) is produced, and the coercive magnetic force iHc and residual magnetism Br of this bond magnet B are produced. When the maximum energy product BH _max is measured with a measuring magnetic field of 10 kOe, the coercive force iHc is 1800 to 2200 Oe, more preferably 1900 to 2100 Oe, and the residual magnetism Br is preferably 3410 G or more, more preferably 3420 G or more. The maximum energy product BH _max is preferably 2.80 MGOe or more, more preferably 2.80 to 3.00 MGOe, and most preferably 2.80 to 2.90 MGOe.

Further, the bond magnet A is cut parallel to the direction of the applied magnetic field, the shape of the particles is observed at 2000 times with an electron microscope, and the obtained electron micrograph is binarized to obtain a particle shape index. The major axis length (the maximum value of the distance between straight lines when one particle is sandwiched between two parallel straight lines (the length of a line segment drawn perpendicular to two parallel straight lines)) is 1. The ratio of the major axis length (major axis length / minor axis length) (aspect ratio) to the minor axis length of particles of 0 μm or more (minimum value of the distance between straight lines when one particle is sandwiched between two parallel straight lines). When calculated (assuming that each particle is a plate-shaped particle, and calculating the volume average aspect ratio weighted by volume with the volume as major axis length × major axis length × minor axis length), the aspect ratio is 1.5. It is preferably as follows. When the aspect ratio is 1.5 or less, the magnetic field orientation makes it easier to align the particles of the ferrite powder for the bond magnet in the magnetic field direction, so that the bond magnet with high _{particle orientation and high residual magnetization Br and maximum energy product BH max can be obtained.} It becomes easy to manufacture.

Further, the embodiment of the bonded magnet according to the present invention includes the above-mentioned ferrite powder for a bonded magnet and a binder (preferably made of a resin such as a polyamide resin). The fluidity MFR when the ferrite powder for a bonded magnet is mixed with a resin or the like in order to manufacture this bonded magnet is preferably 30 g / 10 minutes or more, and more preferably 35 g / 10 minutes or more.

Hereinafter, examples of the ferrite powder for bonded magnets and the method for producing the same according to the present invention will be described in detail.

[Example 1]
(Manufacturing of coarse ferrite powder)
Strontium carbonate (SrCO ₃ , specific surface area 5.8 m ² / g), lanthanum oxide (La ₂ O ₃ , specific surface area 3.8 m ² / g) and hematite (as iron oxide) (α-Fe ₂ O ₃ , ratio) Surface area 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) in molar ratio Sr: La: Fe: Co = 0.70: 0.30: 0.70: 0 Weigh and mix to a specific surface area of .30, granulate the mixture while adding water in a pan pelletizer, and put the obtained spherical granules with a diameter of 3 to 10 mm into an internal-combustion rotary kiln and put it in the atmosphere. A fired product was obtained by firing (primary firing) at 1100 ° C. for 20 minutes in an atmosphere. This fired product was pulverized with a roller mill to obtain a powder of a composite oxide of iron, strontium, lanthanum and cobalt.

The powder of this composite oxide and hematite (α-Fe ₂ O ₃ , specific surface area 5.3 m ² / g) (as iron oxide) are mixed with the molar ratio of Fe in iron oxide (Fe /) to the total of Sr and La. (Sr + La))) = 10.0, weighed and mixed, and 0.17% by mass of boric acid (as an additive) and 2.3% by mass of potassium chloride were added to the mixture and mixed. After that, water is added to granulate, and the obtained spherical granules having a diameter of 3 to 10 mm are put into an internal-combustion rotary kiln and fired in the air at 1300 ° C. (baking temperature) for 20 minutes (secondary firing). The fired product thus obtained was crushed with a roller mill to obtain a coarse powder. When the specific surface area of this coarse powder was measured by the BET one-point method using a specific surface area measuring device (Monosorb manufactured by Kantachrome Co., Ltd.), the specific surface area was 0.64 m ² / g.

(Manufacturing of ferrite fine powder)
Strontium carbonate (SrCO ₃ , specific surface area 5.8 m ² / g) and hematite (as iron oxide) (α-Fe ₂ O ₃ , specific surface area 5.3 m ² / g) in molar ratio Sr: Fe = 1.0 Weigh and mix to a ratio of 11.0, granulate the mixture while adding water in a pan pelletizer, and put the obtained spherical granules with a diameter of 3 to 10 mm into an internal-combustion rotary kiln. , A fired product was obtained by firing at 970 ° C. for 20 minutes in an air atmosphere. This fired product was crushed with a roller mill to obtain fine powder. When the specific surface area of this fine powder was measured by the BET one-point method using a specific surface area measuring device (Monosorb manufactured by Kantachrome Co., Ltd.), the specific surface area was 7.96 m ² / g.

(Manufacturing of ferrite powder for bonded magnets)
75 parts by mass of the obtained crude powder, 25 parts by mass of fine powder, and 150 parts by mass of water were put into a wet attritor and pulverized for 20 minutes to obtain a slurry. The solid obtained by filtering this slurry was dried in the air at 150 ° C. for 10 hours to obtain a dried cake. The crushed product obtained by crushing this dried cake with a mixer is used as a medium by a vibrating ball mill (Uras Vibrator KEC-8-YH manufactured by Murakami Seiki Kosakusho Co., Ltd.) using a steel ball having a diameter of 12 mm. After crushing at a rotation speed of 1800 rpm and an amplitude of 8 mm for 28 minutes, a steel ball having a diameter of 8 mm was used as a medium by the above-mentioned vibration ball mill, and crushing treatment was performed at a rotation speed of 1800 rpm and an amplitude of 8 mm for 28 minutes. .. The pulverized product thus obtained was annealed (annealed) in the air at 925 ° C. for 30 minutes in an electric furnace to obtain a ferrite powder for a bonded magnet.

The composition of this ferrite powder for bonded magnets is analyzed by calculating the amount of each element by the fundamental parameter method (FP method) using a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Co., Ltd.). went. In this composition analysis, ferrite powder for bond magnets is packed in a measurement cell and ^{molded by applying a pressure of 10 tons / cm 2} for 20 seconds, the measurement mode is EZ scan mode, the measurement diameter is 30 mm, and the sample form is oxide. With the measurement time as the standard time, qualitative analysis was performed in a vacuum atmosphere, and then quantitative analysis was performed on the detected constituent elements. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.3 wt% MnO, and _Fe 2 _{O 3} of 86.2 wt%, 1.7 wt% and of _Co 2 _{O 3,} and 7.9 wt% SrO, and 0.1 wt% BaO, are included 3.5 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.22, y = 0.020, n = 11. 26, z = 1.11. For z, the valence of Sr is +2, the valence of La is +3, the valence of Fe is +3, the valence of Co is +2, and the valence of O is -2, and the total valence of the chemical formula is 0. It was calculated to be (zero).

Further, regarding this ferrite powder for a bond magnet, a dry laser diffraction type particle size distribution measuring device (manufactured by Nippon Laser Co., Ltd. (HELOS & RODOS)) is used, and the focal length is 20 mm, the dispersion pressure is 5.0 bar, and the attraction pressure is 130 mbar, based on the volume. The particle size distribution was measured. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 27.5% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 48.1% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 24.5 volumes. %Met.

Further, for this ferrite powder for bond magnets, a powder X-ray diffractometer (Miniflex 600 manufactured by Rigaku Co., Ltd.) was used to set the tube voltage to 40 kV, the tube current to 15 mA, the measurement range to 15 ° to 60 °, and the scan speed. Measurement was performed by powder X-ray diffraction method (XRD) at 1 ° / min and a scan width of 0.02 °. As a result, all the peaks were _{observed at the same positions as SrFe 12} O _19, and it was confirmed that the ferrite powder for the bonded magnet of this example had an M-type ferrite structure. This result was the same in Examples 2 to 4 and Comparative Examples 1 to 5 described below.

Further, when the average particle size (APD) of the ferrite powder for bond magnets was measured by the air permeation method using a specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation), the average particle size was 1.47 μm. rice field. Further, when the specific surface area of the ferrite powder for a bonded magnet was measured by the same method as described above, the specific surface area was 1.88 m ² / g.

Further, the density of the ferrite powder for the bond magnet when 10 g of the ferrite powder for the bond magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ ^{and then compressed at a pressure of 1 ton / cm 2} is the compression of the ferrite powder for the bond magnet. When measured as a density (CD), it was ^{3.73 g / cm 3.}

Further, 8 g of ferrite powder for bond magnets and 0.4 cc of polyester resin (P-resin manufactured by Nippon Geographical Science Co., Ltd.) were kneaded in a dairy pot, and 7 g of the obtained kneaded product was filled in a mold having an inner diameter of 15 mmφ and 2 tons. The molded product obtained by compressing at a pressure of / cm ² for 60 seconds was withdrawn from the mold and dried at 150 ° C. for 30 minutes to obtain a green compact. As the magnetic characteristics of this green compact, when the coercive force iHc and residual magnetization Br of the green compact were measured with a measurement magnetic field of 10 kOe using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.), the coercive force was measured. The iHc was 2520Oe and the residual magnetization Br was 2010G.

(Manufacturing of bond magnet A)
92.0 parts by mass of the obtained ferrite powder for bond magnets, 0.6 parts by mass of a silane coupling agent (Z-6094N manufactured by Toray Dow Corning Co., Ltd.), and a lubricant (VPN-212P manufactured by Henkel Co., Ltd.) 0. 8 parts by mass and 6.6 parts by mass of powdered polyamide resin (P-1011F manufactured by Ube Kosan Co., Ltd.) as a binder were weighed, filled in a mixer and mixed, and the obtained mixture was kneaded at 230 ° C. Then, kneaded pellets having an average diameter of 2 mm were obtained. Using a melt flow indexer (melt flow indexer C-5059D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.), the weight of the above mixture extruded at 270 ° C. and a load of 10 kg was measured, and this weight was measured for 10 minutes. The fluidity MFR when mixing the ferrite powder for a bonded magnet was determined by converting it into the amount extruded by hitting, and it was 145.1 g / 10 minutes. This kneaded pellet is loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.) and ^{injection-formed at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm 2} in a magnetic field of 9.7 kOe to have a diameter of 15 mm × height. A cylindrical bond magnet A (FC 92.0 mass%, 9.7 kOe) having a diameter of 8 mm (the orientation direction of the magnetic field was along the central axis of the column) was obtained.

As the magnetic characteristics of this bond magnet A, a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) is used to obtain the coercive force iHc, residual magnetization Br, and maximum energy product BH _{max of the bond magnet A at a measurement magnetic field of 10 kOe.} As a result, the coercive force iHc was 2310Oe, the residual magnetization Br was 3281G, and the maximum energy product BH _max was 2.68MGOe.

Further, the bond magnet A is cut parallel to the direction of the applied magnetic field, the shape of the particles is observed at 2000 times with a scanning electron microscope (SEM), and the obtained SEM photograph is binarized to obtain particles. As the shape index of, 200 or more particles in the SEM photograph (long axis length in which the entire outer edge is observed in one or more visual fields of the SEM photograph (straight line when one particle is sandwiched between two parallel straight lines) For 200 or more particles with an inter-straight distance of 1.0 μm or more), the major axis length with respect to the minor axis length (minimum value of the inter-straight line distance when one particle is sandwiched between two parallel straight lines). The average value (aspect ratio) of the ratios (major axis length / minor axis length) was 1.48. As this aspect ratio, the volume average aspect ratio weighted by volume was calculated by assuming that each particle is a plate-shaped particle and the volume is major axis length × major axis length × minor axis length.

(Manufacturing of bond magnet B)
93.5 parts by mass of the obtained ferrite powder for bond magnets, 0.6 parts by mass of a silane coupling agent (Z-6094N manufactured by Toray Dow Corning Co., Ltd.), and a lubricant (VPN-212P manufactured by Henkel Co., Ltd.) 0. 8 parts by mass and 5.1 parts by mass of powdered polyamide resin (P-1011F manufactured by Ube Kosan Co., Ltd.) as a binder were weighed, filled in a mixer and mixed, and the obtained mixture was kneaded at 230 ° C. Then, kneaded pellets having an average diameter of 2 mm were obtained. Using a melt flow indexer (melt flow indexer C-5059D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.), the weight of the above mixture extruded at 270 ° C. and a load of 10 kg was measured, and this weight was measured for 10 minutes. The fluidity MFR when mixing the ferrite powder for a bonded magnet was determined by converting it into the amount extruded by hitting, and it was 69.7 g / 10 minutes. This kneaded pellet is loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.) and ^{injection-formed at a temperature of 300 ° C. and a molding pressure of 8.5 N / mm 2} in a magnetic field of 9.7 kOe to have a diameter of 15 mm × height. A cylindrical bond magnet B (FC 93.5 mass%, 9.7 kOe) having a diameter of 8 mm (the orientation direction of the magnetic field was along the central axis of the column) was obtained.

As the magnetic characteristics of this bond magnet B, a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) is used to obtain the coercive force iHc, residual magnetization Br, and maximum energy product BH _{max of the bond magnet B at a measurement magnetic field of 10 kOe.} As a result, the coercive force iHc was 2050Oe, the residual magnetization Br was 3443G, and the maximum energy product BH _max was 2.88MGOe.

[Example 2]
A ferrite powder for a bonded magnet was obtained by the same method as in Example 1 except that the temperature of annealing (annealing) in producing the ferrite powder for a bonded magnet was set to 900 ° C.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.4 wt% MnO, and _Fe 2 _{O 3} of 85.5 wt%, 2.0 wt% and of _Co 2 _{O 3,} and 7.7 wt% SrO, and BaO of 0.1 weight%, contains 4.0 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.25, y = 0.020, n = 11. 08, z = 1.38.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 24.8% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 55.9% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 19.3 volume. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.39 μm, the specific surface area was 2.18 m ² / g, the compression density (CD) was 3.78 g / cm ³ , the coercive force iHc of the green compact was 2520 Oe, and the residual magnetization Br was 2010 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. The maximum energy product BH _max was 2.67 MGOe, and the aspect ratio was 1.47. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 121.2 g / 10 minutes.

Further, using the above-mentioned ferrite powder for a bonded magnet, a bonded magnet B was obtained by the same method as in Example 1. When the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured for this bond magnet B by the same method as in Example 1, the coercive force iHc was 2050 Oe, the residual magnetization Br was 3442 G, and the maximum energy product BH _max. Was 2.88 MGOe. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 36.6 g / 10 minutes.

[Example 3]
A ferrite powder for a bonded magnet was obtained by the same method as in Example 1 except that the annealing (annealing) temperature when producing the ferrite powder for a bonded magnet was set to 950 ° C.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.4 wt% MnO, and _Fe 2 _{O 3} of 85.7 wt%, 1.8 wt% and of _Co 2 _{O 3,} and 7.9 wt% SrO, and 0.2 wt% BaO, includes a 3.7 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.23, y = 0.020, n = 11. 07, z = 1.40.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 26.7% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 47.8% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 25.5 volume. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.47 μm, the specific surface area was 1.88 m ² / g, the compression density (CD) was 3.75 g / cm ³ , the coercive force iHc of the green compact was 2590 Oe, and the residual magnetization Br was 1990 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. The maximum energy product BH _max was 2.68 MGOe, and the aspect ratio was 1.48. The fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1 and found to be 148.2 g / 10 minutes.

Further, using the above-mentioned ferrite powder for a bonded magnet, a bonded magnet B was obtained by the same method as in Example 1. When the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured for this bond magnet B by the same method as in Example 1, the coercive force iHc was 2027 Oe, the residual magnetization Br was 3426 G, and the maximum energy product BH _max. Was 2.85 MGOe. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 77.4 g / 10 minutes.

[Example 4]
A ferrite powder for a bonded magnet was obtained by the same method as in Example 1 except that the temperature of annealing (annealing) in producing the ferrite powder for a bonded magnet was set to 975 ° C.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.4 wt% MnO, and _Fe 2 _{O 3} of 85.5 wt%, 1.9 wt% and of _Co 2 _{O 3,} and 8.0 wt% of SrO, and 0.2 wt% BaO, includes a 3.7 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.23, y = 0.020, n = 10. It was 95, z = 1.58.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 23.9% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 50.6% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 25.6 volumes. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.58 μm, the specific surface area was 1.73 m ² / g, the compression density (CD) was 3.71 g / cm ³ , the coercive force iHc of the green compact was 2530 Oe, and the residual magnetization Br was 1970 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 2176Oe and the residual magnetization Br was 3291G. The maximum energy product BH _max was 2.66 MGOe, and the aspect ratio was 1.45. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 143.6 g / 10 minutes.

Further, using the above-mentioned ferrite powder for a bonded magnet, a bonded magnet B was obtained by the same method as in Example 1. When the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured for this bond magnet B by the same method as in Example 1, the coercive force iHc was 1918 Oe, the residual magnetization Br was 3426 G, and the maximum energy product BH _max. Was 2.81 MGOe. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 77.0 g / 10 minutes.

[Comparative Example 1]
After obtaining a powder of a composite oxide of iron, strontium, lanthanum, and cobalt by the same method as in Example 1, a crude powder was obtained by the same method as in Example 1 except that the firing temperature was set to 1250 ° C. rice field. When the specific surface area of this crude powder was measured by the same method as in Example 1, the specific surface area was 0.74 m ² / g.

100 parts by mass of the obtained crude powder and 150 parts by mass of water were put into a wet attritor and pulverized for 20 minutes to obtain a slurry. The solid obtained by filtering this slurry was dried in the air at 150 ° C. for 10 hours to obtain a dried cake. The crushed product obtained by crushing this dried cake with a mixer is used as a medium by a vibrating ball mill (Uras Vibrator KEC-8-YH manufactured by Murakami Seiki Kosakusho Co., Ltd.) using a steel ball having a diameter of 12 mm. , The pulverization treatment was carried out at a rotation speed of 1800 rpm and an amplitude of 8 mm for 28 minutes. The pulverized product thus obtained was annealed (annealed) in the air at 975 ° C. for 30 minutes in an electric furnace to obtain a ferrite powder for a bonded magnet.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.3 wt% MnO, and _Fe 2 _{O 3} of 85.3 wt%, 2.4 wt% and of _Co 2 _{O 3,} and 6.8 wt% SrO, and 0.1 wt% BaO, includes a 4.9 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.030, n = 11. 47, z = 0.80.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 21.3% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 71.9% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 6.8 volumes. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.72 μm, the specific surface area was 1.47 m ² / g, the compression density (CD) ^{was 3.45 g / cm 3} , the coercive force iHc of the green compact was 3060 Oe, and the residual magnetization Br was 1870 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 2415Oe and the residual magnetization Br was 3193G. The maximum energy product BH _max was 2.52 MGOe, and the aspect ratio was 1.43. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 69.8 g / 10 minutes.

Further, using the above-mentioned ferrite powder for bond magnets, an attempt was made to manufacture the bond magnet B by the same method as in Example 1, but the ferrite powder for bond magnets did not flow when mixed, so that the bond magnets did not flow. B could not be manufactured.

[Comparative Example 2]
Coarse powder was obtained by the same method as in Comparative Example 1 except that the firing temperature was set to 1300 ° C. When the specific surface area of this crude powder was measured by the same method as in Example 1, the specific surface area was 0.68 m ² / g. Using this coarse powder, a ferrite powder for a bonded magnet was obtained by the same method as in Comparative Example 1.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.4 wt% MnO, and _Fe 2 _{O 3} of 84.7 wt%, 2.6 wt% and of _Co 2 _{O 3,} and 6.8 wt% SrO, and 0.1 wt% BaO, are included 5.1 wt% _La 2 _{O 3,} in the main component of the ferrite powder for bonded magnets Certain Sr, La, Fe, and Co were detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.32, y = 0.030, n = 11. 27, z = 1.10.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 17.0% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 62.4% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 20.6 volume. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.84 μm, the specific surface area was 1.38 m ² / g, the compression density (CD) was 3.47 g / cm ³ , the coercive force iHc of the green compact was 2590 Oe, and the residual magnetization Br was 1920 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. The maximum energy product BH _max was 2.56 MGOe, and the aspect ratio was 1.49. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 89.5 g / 10 minutes.

Further, using the above-mentioned ferrite powder for bond magnets, an attempt was made to manufacture the bond magnet B by the same method as in Example 1, but the ferrite powder for bond magnets did not flow when mixed, so that the bond magnets did not flow. B could not be manufactured.

[Comparative Example 3]
Strontium carbonate (SrCO _3, a specific surface area of 5.8 m ² / g) and lanthanum oxide _(La 2 _{O 3,} a specific surface area of 3.8 m ² / g) and hematite _(α-Fe 2 _{O 3,} a specific surface area of 5.3 m ² / g) and cobalt oxide (Co ₃ O ₄ , specific surface area 3.3 m ² / g) so that the molar ratio Sr: La: Fe: Co = 0.70: 0.30: 11.70: 0.30. Coarse powder was obtained by the same method as in Example 1 except that the primary firing temperature was changed from 1100 ° C. to 1200 ° C. and the secondary firing was not performed. When the specific surface area of this crude powder was measured by the same method as in Example 1, the specific surface area was 0.51 m ² / g.

Using the obtained crude powder, a ferrite powder for a bonded magnet was obtained by the same method as in Comparative Example 1 except that the annealing (annealing) was set to 985 ° C.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.3 wt% MnO, and _Fe 2 _{O 3} of 85.3 wt%, 2.4 wt% Co ₂ O ₃ and 7.0% by mass of SrO and 4.9% by mass of La ₂ O ₃ are contained, and Sr, La, Fe and Co, which are the main components of ferrite powder for bonded magnets, are contained. was detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.31, y = 0.030, n = 11. 24, z = 1.14.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 26.2% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 72.6% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 1.3 volumes. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.25 μm, the specific surface area was 2.21 m ² / g, the compression density (CD) was 3.26 g / cm ³ , the coercive force iHc of the green compact was 3950 Oe, and the residual magnetization Br was 1790 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 3248Oe and the residual magnetization Br was 3012G. The maximum energy product BH _max was 2.21 MGOe, and the aspect ratio was 1.62. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 42.8 g / 10 minutes.

Further, using the above-mentioned ferrite powder for bond magnets, an attempt was made to manufacture the bond magnet B by the same method as in Example 1, but the ferrite powder for bond magnets did not flow when mixed, so that the bond magnets did not flow. B could not be manufactured.

[Comparative Example 4]
Coarse powder was obtained by the same method as in Comparative Example 3 except that the temperature of the primary firing was set to 1250 ° C. When the specific surface area of this crude powder was measured by the same method as in Example 1, the specific surface area was 0.71 m ² / g.

Using the obtained crude powder, a ferrite powder for a bonded magnet was obtained by the same method as in Comparative Example 3.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.3 wt% MnO, and _Fe 2 _{O 3} of 85.3 wt%, 2.4 wt% Co ₂ O ₃ and 7.1% by mass of SrO and 4.7% by mass of La ₂ O ₃ are contained, and Sr, La, Fe and Co, which are the main components of the ferrite powder for bond magnets, are contained. was detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.30, y = 0.030, n = 11. 27, z = 1.10.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 25.2% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 70.0% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 4.8 volumes. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.26 μm, the specific surface area was 2.19 m ² / g, the compression density (CD) was 3.34 g / cm ³ , the coercive force iHc of the green compact was 3590 Oe, and the residual magnetization Br was 1830 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. The maximum energy product BH _max was 2.33 MGOe, and the aspect ratio was 1.56. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 61.2 g / 10 minutes.

Further, using the above-mentioned ferrite powder for bond magnets, an attempt was made to manufacture the bond magnet B by the same method as in Example 1, but the ferrite powder for bond magnets did not flow when mixed, so that the bond magnets did not flow. B could not be manufactured.

[Comparative Example 5]
Coarse powder was obtained by the same method as in Comparative Example 3 except that the temperature of the primary firing was set to 1300 ° C. When the specific surface area of this crude powder was measured by the same method as in Example 1, the specific surface area was 0.98 m ² / g.

Using the obtained crude powder, a ferrite powder for a bonded magnet was obtained by the same method as in Comparative Example 3.

The composition of this ferrite powder for bonded magnets was analyzed by the same method as in Example 1. As a result, the ferrite powder for bonded magnets, and _Cr 2 _{O 3} 0.1 wt%, and 0.3 wt% MnO, and _Fe 2 _{O 3} of 85.4 wt%, 2.4 wt% Co ₂ O ₃ and 7.0% by mass of SrO and 4.7% by mass of La ₂ O ₃ are contained, and Sr, La, Fe and Co, which are the main components of ferrite powder for bonded magnets, are contained. was detected. Elements such as Cr, Mn, Zn, and Ba, which are considered to be derived from impurities in the raw material, were also detected, but all of them were in a trace amount of 0.4% by mass or less in terms of oxide. These trace elements (1.0% by mass or less in terms of oxide) are regarded as impurities, and the chemical formula of the ferrite powder for bonded magnets is determined from the analytical values of the main components Sr, La, Fe, and Co (Sr _{1-). x La x) · (Fe 1} -y Co y) in the case where denoted as _{n O 19-z x, y} , n, calculating the z, x = 0.30, y = 0.030, n = 11. 39, z = 0.91.

Further, with respect to this ferrite powder for a bonded magnet, the volume-based particle size distribution was measured by the same method as in Example 1. As a result, the frequency distribution of particles having a particle size of less than 1 μm is 27.5% by volume, the frequency distribution of particles having a particle size of 1 to 5 μm is 64.3% by volume, and the frequency distribution of particles having a particle size of more than 5 μm is 8.2 volumes. %Met.

Further, for this ferrite powder for a bonded magnet, the average particle size, specific surface area, compression density (CD), coercive force iHc of the green compact, and residual magnetization Br were measured by the same method as in Example 1. As a result, the average particle size was 1.22 μm, the specific surface area was 2.41 m ² / g, the compression density (CD) was 3.42 g / cm ³ , the coercive force iHc of the green compact was 3140 Oe, and the residual magnetization Br was 1800 G. there were.

Further, using this ferrite powder for a bonded magnet, a bonded magnet A was obtained by the same method as in Example 1. For this bond magnet A, the coercive force iHc, the residual magnetization Br and the maximum energy product BH _max were measured by the same method as in Example 1, and the aspect ratio was calculated. As a result, the coercive force iHc was 2315Oe and the residual magnetization Br was 3108G. The maximum energy product BH _max was 2.36 MGOe, and the aspect ratio was 1.58. When the fluidity MFR when mixing the ferrite powder for the bonded magnet was determined by the same method as in Example 1, it was 58.6 g / 10 minutes.

Further, using the above-mentioned ferrite powder for bond magnets, an attempt was made to manufacture the bond magnet B by the same method as in Example 1, but the ferrite powder for bond magnets did not flow when mixed, so that the bond magnets did not flow. B could not be manufactured.

The results of these examples and comparative examples are shown in Tables 1 to 7.

From the results of Examples 1 to 4 and Comparative Examples 1 to 5, in Examples 1 to 4, it is possible to produce a ferrite powder for a bond magnet capable of obtaining a bond magnet having a high residual magnetization Br by magnetic field orientation. I understand.

Claims (15)

A process of mixing iron, strontium, lanthanum, and cobalt composite oxide powder and iron oxide to granulate, then firing and crushing to obtain ferrite coarse powder, and ferrite coarse powder and this ferrite A ferrite powder for a bonded magnet, which comprises a step of mixing a ferrite fine powder having a larger specific surface area than the coarse powder and a step of pulverizing a mixture of the ferrite coarse powder and the ferrite fine powder and then annealing the mixture. Manufacturing method. The composite oxide powder can be obtained by mixing strontium carbonate, lanthanum oxide, iron oxide and cobalt oxide, granulating the mixture, and then firing at 1000 to 1250 ° C. to pulverize the obtained calcined product. The method for producing a ferrite powder for a bonded magnet according to claim 1, wherein the ferrite powder for a bonded magnet is produced. The production of a ferrite powder for a bonded magnet according to claim 1 or 2, wherein the composite oxide powder and the iron oxide are mixed and granulated, and then calcined at 1280 to 1400 ° C. Method. When the powder of the composite oxide and the iron oxide are mixed, the composite is such that the molar ratio Fe / (Sr + La) of Fe in the iron oxide to the total of Sr and La is 4.5 to 11.7. The method for producing a ferrite powder for a bonded magnet according to any one of claims 1 to 3, wherein the oxide powder and the iron oxide are mixed. The method for producing a ferrite powder for a bonded magnet according to any one of claims 1 to 4, wherein the specific surface area of the coarse ferrite powder is 0.5 to 1.0 m ^{2 / g.} The ferrite fine powder was granulated by mixing strontium carbonate and iron oxide so that the molar ratio of Fe in iron oxide to Sr in strontium carbonate Fe / Sr was 10.0 to 12.5, and then 900. The method for producing a ferrite powder for a bonded magnet according to any one of claims 1 to 5, which is obtained by pulverizing a fired product obtained by firing at ~ 1000 ° C. The bond magnet according to any one of claims 1 to 6, wherein the ratio of the crude ferrite powder is 60 to 90% by mass when the coarse ferrite powder and the fine ferrite powder are mixed. Ferrite powder manufacturing method. _{(Sr 1-x La x)} · (Fe 1-y Co y) n O 19-z ( where, 0 <x ≦ 0.5,0 <y ≦ 0.04,10.0 ≦ n ≦ 12.5 , -1.0 ≦ z ≦ 3.5), and in the volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device, the proportion of particles having a particle size of less than 1 μm is 20 to 40% by volume. A ferrite powder for a bonded magnet, characterized in that the proportion of particles of 1 to 5 μm is 30 to 60% by volume and the proportion of particles larger than 5 μm is 18 to 30% by volume. The density of the ferrite powder for the bond magnet when 10 g of the ferrite powder for the bond magnet is filled in a cylindrical mold having an inner diameter of 2.54 cmφ ^{and then compressed at a pressure of 1 ton / cm 2} is the compression density of the ferrite powder for the bond magnet. The ferrite powder for a bond magnet according to claim 8, wherein the ferrite powder for a bond magnet has a compression density of 3.70 g / cm ^{3 or more when measured as.} 8 g of the ferrite powder for a bond magnet and 0.4 cc of polyester resin are kneaded in a dairy pot, and 7 g of the obtained kneaded product is filled in a mold having an inner diameter of 15 mmφ and compressed at a pressure of ^{2 tons / cm 2 for 60 seconds.} When the coercive force iHc of the green compact obtained by removing the molded product from the mold and drying it at 150 ° C. for 30 minutes was measured with a measuring magnetic field of 10 kOe, the coercive force iHc was 1500 Oe or more. The ferrite powder for a bonded magnet according to claim 8 or 9. 92.0 parts by mass of the ferrite powder for a bonded magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 6.6 parts by mass of a powdered polyamide resin are filled in a mixer and mixed. The resulting mixture was kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets were injected and formed at a ^{temperature of 300 ° C. and a molding pressure of 8.5 N / mm 2 in a magnetic field of 9.7 kOe.} Then, a cylindrical bond magnet A having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is the direction along the central axis of the column) was produced, and the residual magnetization Br of the bond magnet A was measured with a measurement magnetic field of 10 kOe. The ferrite powder for a bonded magnet according to any one of claims 8 to 10, wherein the residual magnetization Br is sometimes 3270 G or more. The ferrite powder for a bond magnet according to claim 11, wherein the maximum energy product BH _{max of the bond magnet A is 2.65 MGOe or more when the maximum energy product BH max} is measured with a measurement magnetic field of 10 kOe. 93.5 parts by mass of the ferrite powder for a bond magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and 5.1 parts by mass of a powdered polyamide resin are filled in a mixer and mixed. The resulting mixture was kneaded at 230 ° C. to prepare kneaded pellets having an average diameter of 2 mm, and the kneaded pellets were injected and formed at a ^{temperature of 300 ° C. and a molding pressure of 8.5 N / mm 2 in a magnetic field of 9.7 kOe.} Then, a cylindrical bond magnet B having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field is the direction along the central axis of the column) was produced, and the residual magnetization Br of the bond magnet B was measured with a measurement magnetic field of 10 kOe. The ferrite powder for a bonded magnet according to any one of claims 8 to 10, wherein the residual magnetization Br is sometimes 3410 G or more. The ferrite powder for a bond magnet according to claim 13, wherein the maximum energy product BH _{max of the bond magnet B is 2.80 MGOe or more when the maximum energy product BH max} is measured with a measurement magnetic field of 10 kOe. A bond magnet comprising the ferrite powder for a bond magnet according to any one of claims 8 to 14 and a binder.