JP2022084472A - Hexagonal ferrite magnetic powder for bonded magnet and manufacturing method thereof, and bonded magnet and manufacturing method thereof - Google Patents

Abstract

To provide a hexagonal a ferrite magnetic powder for a bond magnet and a manufacturing method thereof capable of obtaining a high residual magnetic flux density Br when used for a bond magnet, and a bond magnet having a high residual magnetic flux density Br and a manufacturing method thereof.SOLUTION: A hexagonal ferrite magnetic powder for a bond magnet is represented by a composition formula (Sr1-xLax)(Fe1-yZny)nO19-z (however, 0.01≤x≤0.50, 0.010≤y≤0.040, 10.00≤n≤12.50, z=19-[2(1-x)+3x+n{3(1-y)+2y}]/2), in the volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring device, the proportion of particles with a particle size of less than 1 μm is 25 volume% or more and 40 volume% or less, the proportion of particles with a particle size of 1 μm or more and less than 5 μm is 30 volume% or more and 65 volume% or less, and the proportion of particles with a particle size of 5 μm or more is 7 volume% or more and 30 volume% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hexagonal ferrite magnetic powder for a bonded magnet and its manufacturing method, and a bonded magnet and its manufacturing method, in particular, a hexagonal ferrite magnetic powder for a bonded magnet containing coarse powder and fine powder of the hexagonal ferrite magnetic powder and its manufacturing method. Regarding the manufacturing method.

Conventionally, ferrite-based 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 it is inferior in productivity due to cracking and polishing, and it is difficult to process it 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, since rare earth magnets cost about 20 times as much as ferritic sintered magnets and have a problem of being easily rusted, it is desired to use ferritic bonded magnets instead of ferritic sintered magnets.

As such a ferrite powder for a bonded magnet, Patent Document 1 states that the composition is (Sr _1-x A _x ) O · n [(Fe _{1- y} By) ₂ O ₃ ] (where A is La, La-. Nd, La-Pr or La-Nd-Pr, B is Zn or Zn-Co, n = 5.80 to 6.10, x = 0.10 to 0.50, y = 0.0083 to 0.042) It is a magnesium 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 to 3 μm, and the magnesium ferrite particles. A strontium ferrite particle powder containing 60% or more of plate-like particles in the powder is disclosed. Further, Examples 1 and 2 disclose SrLaZn ferrite powder in which A is La and B is Zn in the composition formula. Further, as a method for producing strontium ferrite particle powder, a production method is disclosed in which a powder as a raw material for strontium ferrite particle powder is mixed, fired, pulverized and then annealed.

Japanese Unexamined Patent Publication No. 2001-189210

The hexagonal ferrite magnetic powder for bonded magnets described in Patent Document 1 was developed with the aim of high orientation and high filling, but its compression density is only about 3.4 g / cm ³ and also. The residual magnetic flux density Br of a bond magnet manufactured using the magnetic powder is only about 3000 G, and a hexagonal ferrite magnetic powder for a bond magnet that can achieve a higher residual magnetic flux density Br as a bond magnet is required. ing.
The present invention provides a hexagonal ferrite magnetic powder for a bond magnet capable of obtaining a high residual magnetic flux density Br when used in a bond magnet and a method for producing the same, and a bond magnet having a high residual magnetic flux density Br and a method for producing the same. The purpose is to do.

The present invention for solving the above problems is a hexagonal ferrite magnetic powder for a bonded magnet, wherein the composition formula (Sr _1-x La _x ) (Fe _1-y Zn _y ) _n O _19-z (however, 0.01 ≦ x ≦ 0.50, 0.010 ≦ y ≦ 0.040, 10.00 ≦ n ≦ 12.50, z = 19- [2 (1-x) + 3x + n {3 (1-y) + 2y }] / 2), and in the volume-based particle size distribution measured by the laser diffraction type particle size distribution measuring device (hereinafter, simply referred to as "particle size distribution"), the proportion of particles having a particle size of less than 1 μm is 25% by volume. The proportion of particles having a particle size of 1 μm or more and less than 5 μm is 30% by volume or more and 65% by volume or less, and the proportion of particles having a particle size of 5 μm or more is 7% by volume or more and 30% by volume or less. It is characterized by.

The hexagonal ferrite magnetic powder for bonded magnets includes 92.0 parts by mass of hexagonal ferrite magnetic powder for bonded magnets, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and a powdered polyamide resin. 6.6 parts by mass was filled in a mixer and kneaded, and the obtained kneaded product was put into a melt indexer, and the weight of the kneaded product extruded at 270 ° C. and a load of 10 kg was measured, and this weight was measured for 10 minutes. The fluidity of the kneaded product, which is obtained by converting it into the mass extruded by hitting, is preferably 100 g / 10 min or more.

The hexagonal ferrite magnetic powder for bond magnets is obtained by filling a cylindrical mold having an inner diameter of 2.54 cmφ with 10 g of hexagonal ferrite magnetic powder for bond magnets and then compressing the molded product at a pressure of 1 ton / cm ³ . The density is preferably 3.60 g / cm ³ or more, and in the particle size distribution, the proportion of particles having a particle size of 1 μm or more and less than 5 μm is 50% by volume or more and 65% by volume or less, and the proportion of particles having a particle size of 5 μm or more is It may be 7% by volume or more and 20% by volume or less.

Further, the present invention from another viewpoint is a method for producing a hexagonal ferrite magnetic powder for a bonded magnet, wherein the composition formula (Sr _1-x1 La _x1 ) (Fe _1-y1 Zn _y1 ) _n1 O _19-z1 (however). , 0.01 ≦ x1 ≦ 0.50, 0.010 ≦ y1 ≦ 0.040, 10.00 ≦ n1 ≦ 12.50, z1 = 19- [2 (1-x1) + 3x1 + n1 {3 (1-y1) + 2y1}] / 2) The process of mixing the powder that is the raw material of the hexagonal ferrite magnetic powder and then firing at the first temperature to obtain the coarse powder of hexagonal ferrite, and the composition formula (Sr _1-x2 ). La _x2 ) (Fe _1-y2 Zn _y2 ) _n2 O _19-z2 (However, 0 ≦ x2 ≦ 0.50, 0 ≦ y2 ≦ 0.040, 10.00 ≦ n2 ≦ 12.50, z2 = 19- [ 2 (1-x2) + 3x2 + n2 {3 (1-y2) + 2y2}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, at the second temperature lower than the first temperature. The step of obtaining fine powder of hexagonal ferrite magnetic powder by firing, and the mass ratio of the coarse powder to the total mass of the coarse powder and the fine powder is 60% by mass or more and 90% by mass or less. It is characterized by including a step of obtaining a pulverized mixed powder by mixing and pulverizing at a certain ratio, and a step of annealing the pulverized mixed powder.
In this production method, it is preferable to carry out a pulverization treatment in a step of obtaining fine powder so that the compression density of the fine powder is 3.00 g / cm ³ or more and 4.00 g / cm ³ or less.
Further, in this production method, the first temperature is preferably 1220 ° C. or higher and 1400 ° C. or lower, and the second temperature is preferably 900 ° C. or higher and 1000 ° C. or lower.

Further, the present invention from another viewpoint is a bonded magnet containing the hexagonal ferrite magnetic powder for a bonded magnet and a resin of the present invention.
Further, the present invention from another viewpoint is a method for manufacturing a bonded magnet using the hexagonal ferrite magnetic powder for a bonded magnet obtained by the method for producing a hexagonal ferrite magnetic powder for a bonded magnet of the present invention.

According to the present invention, there is provided a hexagonal ferrite magnetic powder for a bonded magnet capable of obtaining a high residual magnetic flux density Br when used in a bonded magnet. Further provided are a method for producing a hexagonal ferrite magnetic powder for a bond magnet capable of obtaining a high residual magnetic flux density Br when used in a bond magnet, and a bond magnet having a high residual magnetic flux density Br.

It is a graph which shows the result of having measured the particle size distribution of the hexagonal ferrite magnetic powder for a bond magnet of Example 1 and Comparative Example 1 by a laser diffraction type particle size distribution measuring apparatus.

(Hexagonal ferrite magnetic powder for bonded magnets)
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention has a composition formula (Sr _1-x La _x ) (Fe _1-y Zn _y ) _n O _19-z (however, 0.01 ≦ x ≦ 0.50, 0). .010≤y≤0.040, 10.00≤n≤12.50, z = 19- [2 (1-x) + 3x + n {3 (1-y) + 2y}] / 2), particle size distribution The proportion of particles having a particle size of less than 1 μm is 25% by volume or more and 40% by volume or less, the proportion of particles having a particle size of 1 μm or more and less than 5 μm is 30% by volume or more and 65% by volume or less, and particles having a particle size of 5 μm or more. The proportion of the particles is 7% by volume or more and 30% by volume or less. Hereinafter, aspects such as the composition and particle size distribution of the hexagonal ferrite magnetic powder for bonded magnets of the present invention will be described.

[composition]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention has a composition formula (Sr _1-x La _x ) (Fe _1-y Zn _y ) _n O _19-z (however, 0.01 ≦ x ≦ 0.50, 0). .010≤y≤0.040, 10.00≤n≤12.50, z = 19- [2 (1-x) + 3x + n {3 (1-y) + 2y}] / 2), Sr. It is a hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure containing La and Zn as essential elements.
Here, by substituting La for Sr sites and Zn for Fe sites in the crystal structure of the Sr-based hexagonal ferrite magnetic powder, a hexagonal ferrite magnetic powder having a higher magnetic force than the Sr-based hexagonal ferrite magnetic powder can be obtained. Obtainable. In order to obtain the effect of improving the magnetic force, the value of x in the above composition formula is 0.01 or more, and the value of y is 0.010 or more. On the other hand, if the addition of each of La and Zn is excessive, it becomes difficult to maintain the crystal structure. Therefore, the value of x in the above composition formula is set to 0.50 or less, and the value of y is set to 0.040 or less. The numerical range of x is preferably 0.07 or more and 0.50 or less, and more preferably 0.15 or more and 0.40 or less. The numerical range of y is preferably 0.005 or more and 0.050 or less, and more preferably 0.015 or more and 0.030 or less. In order to obtain a hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n in the above composition formula is 10.00 or more and 12.50 or less. The value of n is preferably 11.00 or more and 12.00 or less from the viewpoint of suppressing the remaining amount of unreacted material after firing.
The value of z is the value of the composition formula, where the valence of Sr is +2, the valence of La is +3, the valence of Fe is +3, the valence of Zn is +2, and the valence of O is -2 in the above composition formula. It can be calculated so that the total number is 0 (zero), and it can be shown as z = 19- [2 (1-x) + 3x + n {3 (1-y) + 2y}] / 2.
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention may contain unavoidable components such as impurities contained in raw materials and impurities derived from manufacturing equipment. Examples of such a component include oxides such as Mn and Ba. These contents are preferably suppressed to 0.4% by mass or less. The above composition formula is a composition formula excluding unavoidable components.

[Particle size distribution]
In the hexagonal ferrite magnetic powder for bonded magnets of the present invention, in order to obtain high filling property, the proportion of particles having a particle size of less than 1 μm is 25 volumes in the particle size distribution on a volume basis measured by a laser diffraction type particle size distribution measuring device. % Or more and 40% by volume or less, the proportion of particles having a particle size of 1 μm or more and less than 5 μm is 30% by volume or more and 65% by volume or less, and the proportion of particles having a particle size of 5 μm or more is 7% by volume or more and 30% by volume or less. , The proportion of particles with a particle size of less than 1 μm is 25% by volume or more and 35% by volume or less, the proportion of particles with a particle size of 1 μm or more and less than 5 μm is 40% by volume or more and 65% by volume or less, and the proportion of particles with a particle size of 5 μm or more is 7 volumes. % Or more and 20% by volume or less, preferably 27% by volume or more and 32% by volume or less of particles having a particle size of 1 μm or less, and 50% by volume or more and 65% by volume or less of particles having a particle size of 1 μm or more and less than 5 μm. It is more preferable that the proportion of particles having a particle size of 5 μm or more is 7% by volume or more and 15% by volume or less.
Among them, the most distinctive feature is that particles having a particle size of less than 1 μm and particles having a particle size of 5 μm or more are contained in a certain amount or more. In the conventional SrLaZn-based hexagonal ferrite magnetic powder as in Patent Document 1, those having a uniform particle size distribution are aimed at, and the particle size distribution is wide and the particle size is wide like the hexagonal ferrite magnetic powder for bonded magnets of the present invention. Conventionally, there has been no technical idea of a magnetic powder containing particles of less than 1 μm and particles of 5 μm or more in a certain amount or more.
In the volume-based particle size distribution of the hexagonal ferrite magnetic powder for bonded magnets of the present invention 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 25% by volume or more and the particles. High filling properties of hexagonal ferrite magnetic powder for bonded magnets can be obtained for the first time when the proportion of particles having a diameter of 5 μm or more is 7% by volume or more. If the proportion of particles with a particle size of less than 1 μm is less than 25% by volume, or the proportion of particles with a particle size of 5 μm or more is less than 7% by volume, the hexagonal ferrite magnetic powder for bonded magnets has a high filling property. Cannot be achieved, and the effect of the present invention cannot be obtained.
From the viewpoint of obtaining high filling property, the value of ratio a / b between the volume ratio (a) of particles having a particle size of less than 1 μm and the volume ratio (b) of particles having a particle size of 5 μm or more is 2.0 or more and 3.5 or less. Is preferable.

[Compression density]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention has high filling property as described above. This filling property is evaluated by the density of a molded product obtained by filling 10 g of the above hexagonal ferrite magnetic powder powder for a bonded magnet into a cylindrical mold having an inner diameter of 2.54 cmφ and then compressing the powder at a pressure of 1 ton / cm ² . be able to. The hexagonal ferrite magnetic powder for a bonded magnet of the present invention preferably has a compression density of 3.60 g / cm ³ or more, and more preferably 3.60 g / cm ³ or more and 3.80 g / cm ³ or less. .. The higher the compression density, the easier it is to obtain a high residual magnetic flux density Br when a bonded magnet is manufactured using the hexagonal ferrite magnetic powder for a bonded magnet.

[Average particle size and specific surface area]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention preferably has an average particle size of 1.0 μm or more and 3.0 μm or less, and more preferably 1.0 μm or more and 2.5 μm or less, as measured by an air permeation method. preferable. Further, the hexagonal ferrite magnetic powder for a bonded magnet of the present invention preferably has a specific surface area of 1.0 m ² / g or more and 3.0 m ² / g or less, and 1.5 m ² / g or more and 3.0 m ² /. It is more preferably g or less.

[Fluidity when the ferrite concentration is 92.0% by mass (MFR _A )]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention is in the form of a powder containing 92.0 parts by mass of the hexagonal ferrite magnetic powder for a bonded magnet, 0.6 parts by mass of a silane coupling agent, and 0.8 parts by mass of a lubricant. 6.6 parts by mass of the polyamide resin of the above was filled in a mixer and mixed, and the obtained mixture was kneaded at 230 ° C. to prepare a kneaded product. The ferrite concentration obtained by measuring the weight of the kneaded product melted and extruded at 270 ° C. and a load of 10 kg in accordance with 1: 2014 and converting this weight into the extruded mass per 10 minutes. The fluidity of the kneaded product (referred to as MFR _A in the present specification) at 92.0% by mass is preferably 90 g / 10 min or more, and more preferably 100 g / 10 min or more and 200 g / 10 min or less. preferable. By setting the MFR _A to 100 g / 10 min or more, a bond magnet having a high residual magnetic flux density Br can be obtained as a bond magnet using the magnetic powder. Further, in order to avoid a situation where the moldability is deteriorated due to the fluidity being too high, it is preferably 200 g / 10 min or less.
By controlling the conditions of the pulverization treatment so that the compression density becomes high during the production of fine powder, high fluidity can be realized in the hexagonal ferrite magnetic powder for bonded magnets.

[Magnetic characteristics of bonded magnet A]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention contains 92.0 parts by mass of a ferrite magnetic powder for a bonded magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and a powdery polyamide resin. The mixture obtained by filling 6.6 parts by mass in a mixer and mixing them is kneaded at 230 ° C. to prepare a kneaded product, and from the obtained kneaded product, kneaded pellets having an average diameter of 2 mm are prepared and kneaded. Pellets are ejected and 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 , and have a cylindrical shape with 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 cylinder). ), The bond magnet A can be manufactured.
The residual magnetic flux density Br and the maximum energy product BHmax of the bond magnet A can be measured with a measurement magnetic field of 10 kOe, and by using the hexagonal ferrite magnetic powder for a bond magnet of the present invention, the residual magnetic flux density Br is 3200 G or more. Bond magnet A can be obtained. Further, according to a more preferable aspect of the present invention, a bonded magnet A of 3240 G or more and 3400 G or less can be obtained. Further, according to the present invention, a bond magnet A having a maximum energy product BH _max of 2.50 MGOe or more can be obtained, and according to a more preferable embodiment of the present invention, a bond magnet A having a maximum energy product BH max of 2.55 MGOe or more and 2.70 MGOe or less can be obtained. can.

[Fluidity when the ferrite concentration is 93.5% by mass (MFR _B )]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention is in the form of a powder containing 93.5 parts by mass of the hexagonal ferrite magnetic powder for a bonded magnet, 0.6 parts by mass of a silane coupling agent, and 0.8 parts by mass of a lubricant. 5.1 parts by mass of the polyamide resin of the above was filled in a mixer and mixed, and the obtained mixture was kneaded at 230 ° C. to prepare a kneaded product. The ferrite concentration obtained by measuring the weight of the kneaded product melted and extruded at 270 ° C. and a load of 10 kg in accordance with 1: 2014 and converting this weight into the extruded mass per 10 minutes. The fluidity of the kneaded product (referred to as MFR _B in the present specification) at 93.5% by mass is preferably 25 g / 10 min or more, more preferably 40 g / 10 min or more, and 40 g / 10 min or more. It is more preferably 10 min or more and 110 g / 10 min or less. By setting the MFR _B to 40 g / 10 min or more, a bond magnet having a high residual magnetic flux density Br can be obtained as a bond magnet using the magnetic powder.
By controlling the pulverization conditions so that the compression density becomes high during the production of fine powder, high fluidity can be realized in the hexagonal ferrite magnetic powder for bonded magnets.

[Magnetic characteristics of bond magnet B]
The hexagonal ferrite magnetic powder for a bonded magnet of the present invention contains 93.5 parts by mass of a ferrite magnetic powder for a bonded magnet, 0.6 parts by mass of a silane coupling agent, 0.8 parts by mass of a lubricant, and a powdery polyamide resin. A mixture obtained by filling a mixer with 6.6 parts by mass and mixing them was kneaded at 230 ° C. to prepare a kneaded product, and a kneaded pellet having an average diameter of 2 mm was prepared from the obtained kneaded product. The kneaded pellets were injection-formed in a magnetic field of 9.7 kOe at a temperature of 300 ° C. and a forming pressure of 8.5 N / mm ² , and formed into a cylinder having a diameter of 15 mm and a height of 8 mm (the orientation direction of the magnetic field was along the central axis of the cylinder). The bond magnet B in the direction) can be manufactured.
The residual magnetic flux density Br and the maximum energy product BHmax of the bond magnet B can be measured with a measurement magnetic field of 10 kOe, and by using the hexagonal ferrite magnetic powder for a bond magnet of the present invention, the residual magnetic flux density Br is 3300 G or more. Bond magnet B can be obtained. Further, according to a more preferable aspect of the present invention, a bonded magnet B of 3350 G or more and 3500 G or less can be obtained. Further, according to the present invention, a bond magnet B having a maximum energy product BHmax of 2.60 MGOe or more can be obtained, and according to a more preferable embodiment of the present invention, a bond magnet B having a maximum energy product BHmax of 2.70 MGOe or more and 2.95 MGOe or less can be obtained. ..

(Manufacturing method of hexagonal ferrite magnetic powder for bonded magnets)
The method for producing the hexagonal ferrite magnetic powder for a bonded magnet of the present invention is a composition formula (Sr _1-x1 La _x1 ) (Fe _1-y1 Zn _y1 ) _n1 O _19-z1 (where 0.01 ≦ x1 ≦ 0. 50, 0.010 ≦ y1 ≦ 0.040, 10.00 ≦ n1 ≦ 12.50, z1 = 19- [2 (1-x1) + 3x1 + n1 {3 (1-y1) + 2y1}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, it is fired at the first temperature to obtain a coarse powder of the hexagonal ferrite magnetic powder, and the composition formula (Sr _1-x2 La _x2 ) (Fe _1- ). _y2 Zn _y2 ) _n2 O _19-z2 (However, 0 ≦ x2 ≦ 0.50, 0 ≦ y2 ≦ 0.040, 10.00 ≦ n2 ≦ 12.50, z2 = 19- [2 (1-x2) + 3x2 + n2 {3 (1-y2) + 2y2}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, it is fired at a second temperature lower than the first temperature to hexagonal ferrite magnetic. The step of obtaining fine powder of powder and the coarse powder and the fine powder are mixed and pulverized at a ratio of the mass ratio of the coarse powder to the total mass of the coarse powder and the fine powder to be 60% by mass or more and 90% by mass or less, and pulverized. The present invention includes a step of obtaining the mixed powder obtained by the above-mentioned powder and a step of annealing the mixed powder obtained by the pulverized treatment. By using the fine powder fired at a second temperature lower than the first temperature, which is the firing temperature at the time of obtaining the coarse powder, the filling property of the obtained hexagonal ferrite magnetic powder for a bonded magnet can be improved. As a result, it is possible to obtain a bond magnet having a high residual magnetic flux density Br when the bond magnet is manufactured using the magnetic powder. Here, the specific surface area of the coarse powder is usually smaller than the specific surface area of the fine powder. Each process will be described in detail below.

[Coarse powder manufacturing process]
Composition formula (Sr _1-x1 La _x1 ) (Fe _1-y1 Zn _y1 ) _n1 O _19-z1 (However, 0.01 ≦ x1 ≦ 0.50, 0.010 ≦ y1 ≦ 0.040, 10.00 ≦ n1 ≦ 12.50, z1 = 19- [2 (1-x1) + 3x1 + n {3 (1-y1) + 2y1}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, the first This is a step of firing at one temperature to obtain a coarse powder of hexagonal ferrite magnetic powder.
As the raw material of the crude powder of hexagonal ferrite magnetic powder, each compound of constituent elements Sr, La, Fe and Zn can be used. For example, as the Sr compound, strontium carbonate, strontium chloride and strontium sulfate can be used. , La compound is lanthanum oxide, lanthanum hydroxide, lanthanum sulfate, Fe compound is iron oxide (hematite, magnetite), iron chloride, iron sulfate, preferably hematite, and Zn compound is zinc oxide, zinc chloride, sulfuric acid. Zinc can be used respectively.
In order to obtain the effect of improving the magnetic force of the coarse powder, the value of x1 in the above composition formula is 0.01 or more, and the value of y1 is 0.01 or more. Further, if the addition of each of La and Zn is excessive, it becomes difficult to maintain the hexagonal ferrite crystal structure. Therefore, the value of x1 is set to 0.50 or less, and the value of y1 is set to 0.04 or less. The numerical range of x1 is preferably 0.07 or more and 0.50 or less, and more preferably 0.15 or more and 0.40 or less. The numerical range of y1 is preferably 0.005 or more and 0.050 or less, and more preferably 0.015 or more and 0.030 or less.
Further, in order to obtain a hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n1 in the above composition formula is set to 10.00 or more and 12.50 or less. The value of n1 is preferably 11.00 or more and 12.00 or less from the viewpoint of suppressing the residual unreacted material after firing.
The method for calculating the value of z1 is the same as that for z in the composition formula of the hexagonal ferrite magnetic powder for bonded magnets.
The coarse powder may contain unavoidable components such as impurities contained in the raw material and impurities derived from the manufacturing equipment. Examples of such a component include oxides such as Mn and Ba. These contents are preferably suppressed to 0.4% by mass or less. The above composition formula is a composition formula excluding unavoidable components.

The first temperature, which is the firing temperature in the crude powder manufacturing process, is preferably 1220 ° C. or higher and 1400 ° C. or lower, and more preferably 1220 ° C. or higher and 1300 ° C. or lower. By setting the first temperature to 1220 ° C. or higher, the particle size distribution on a volume basis measured by a laser diffraction type particle size distribution measuring device for the hexagonal ferrite magnetic powder for bonded magnets finally obtained has a particle size of 5 μm or more. The proportion of particles in the above can be easily increased to 7% by volume or more.
In the process of producing the crude powder, a mixture of the raw material powders may be granulated and fired. The atmosphere at the time of firing is preferably an oxidizing atmosphere, and more preferably an atmospheric atmosphere. Further, it is preferable to carry out a pulverization treatment after firing. The method of the pulverization treatment is not particularly limited, and examples thereof include known methods using a roller mill or the like.

The specific surface area of the coarse powder measured by the BET one-point method is preferably 0.2 m ² / g or more and 0.6 m ² / g or less, and 0.3 m ² / g or more and 0.5 m ² / g or less. Is more preferable.

[Fine powder manufacturing process]
Composition formula (Sr _1-x2 La _x2 ) (Fe _1-y2 Zn _y2 ) _n2 O _19-z2 (However, 0 ≦ x2 ≦ 0.50, 0 ≦ y2 ≦ 0.040, 10.00 ≦ n2 ≦ 12. 50, z2 = 19- [2 (1-x2) + 3x2 + n2 {3 (1-y2) + 2y2}] / 2) After mixing the powder that is the raw material of the fine powder of the hexagonal ferrite magnetic powder, the first This is a step of obtaining fine powder of hexagonal ferrite magnetic powder by firing at a second temperature lower than the temperature.
As the raw material of the fine powder of hexagonal ferrite magnetic powder, each compound of constituent elements Sr, La, Fe and Zn can be used. For example, as the Sr compound, strontium carbonate, strontium chloride, strontium sulfate, etc. can be used. The La compound is lanthanum oxide, lanthanum hydroxide, or lanthanum sulfate, the Fe compound is iron oxide (hematite, magnetite), iron chloride, iron sulfate, preferably hematite, and the Zn compound is zinc oxide, zinc chloride, or zinc sulfate. Can be used respectively.
Since it is difficult to maintain the hexagonal ferrite crystal structure, the value of x2 is set to 0.50 or less and the value of y2 is set to 0.040 or less in the composition formula. The numerical range of x2 is preferably 0.00 or more and 0.50 or less, and more preferably 0 or more and 0.30 or less. The numerical range of y2 is preferably 0 or more and 0.030 or less, and more preferably 0 or more and 0.015 or less.
Further, in order to obtain a hexagonal ferrite magnetic powder having a magnetoplumbite-type crystal structure, the value of n2 in the above composition formula is set to 10.00 or more and 12.50 or less. The value of n2 is preferably 10.50 or more and 12.00 or less from the viewpoint of suppressing the residual unreacted material after firing.
The method for calculating the value of z2 is the same as that for z in the composition formula of the hexagonal ferrite magnetic powder for bonded magnets.
On the other hand, the above composition formula includes the case of x2 = 0 and / or y2 = 0, and the fine powder obtained in this step is any one of hexagonal SrLa ferrite, hexagonal SrZn ferrite and hexagonal Sr ferrite. Hexagonal Sr ferrite is preferable.
Here, it was found that the bonded magnet exhibits extremely excellent magnetic properties when SrLaZn ferrite is used as the coarse powder, whereas when unsubstituted Sr ferrite not substituted with La or Zn is used as the fine powder. rice field. Since fine powder has a larger coercive force than coarse powder, by using Sr ferrite, which has better coercive force, for fine powder, the balance of magnetic characteristics is excellent as a result in combination with SrLaZn ferrite, which has excellent characteristics of saturation magnetic flux density. It is presumed that the hexagonal ferrite magnetic powder for the bonded magnet was obtained.
The fine powder may contain impurities contained in the raw material and unavoidable components derived from the manufacturing equipment. Examples of such a component include oxides such as Mn (manganese) and V (vanadium). These contents are preferably suppressed to 0.4% by mass or less. The above composition formula is a composition formula excluding unavoidable components.

The second temperature, which is the firing temperature in the process for producing fine powder, is preferably 900 ° C. or higher and 1000 ° C. or lower, and more preferably 950 ° C. or higher and 1000 ° C. or lower. By setting the second temperature to 900 ° C. or higher, fine powder having a hexagonal ferrite crystal structure can be easily obtained. Further, by setting the second temperature to 1000 ° C. or lower, the particle size in the volume-based particle size distribution measured by the laser diffraction type particle size distribution measuring device of the hexagonal ferrite magnetic powder for bonded magnets finally obtained The proportion of particles smaller than 1 μm can be easily increased to 25% by volume or more.
In the process of producing fine powder, a mixture of raw material powder may be granulated and fired. The atmosphere at the time of firing is preferably an oxidizing atmosphere, and more preferably an atmospheric atmosphere. Further, it is preferable to carry out a pulverization treatment after firing. The pulverization treatment can be carried out by a known method using a roller mill or the like, but it is preferable to perform a wet pulverization treatment. A dry pulverization treatment such as a roller mill and a wet pulverization treatment may be combined.

For the wet pulverization treatment, a wet pulverizer having a stirring mechanism with a rotary stirring blade can be used, and the peripheral speed of the stirring blade is preferably 0.5 m / s or more and 2.5 m / s or less, preferably 1.0 m / s. More preferably 2.0 m / s or less. Here, the peripheral speed of the stirring blade refers to the speed at the position where the distance from the rotation axis of the stirring blade is the furthest, and is an index showing the strength of crushing in the wet crusher. By setting the peripheral speed of the stirring blade to 0.5 m / s or more and 2.5 m / s or less in this way, 10 g of fine powder after crushing is filled in a cylindrical mold having an inner diameter of 2.54 cmφ and then 1 ton / cm. The compact can be crushed so that the compression density of the molded product compressed at the pressure of ³ is 2.80 g / cm ³ or more and 4.00 g / cm ³ or less. Thereby, the fluidity of the kneaded product produced by using the obtained hexagonal ferrite magnetic powder for a bonded magnet can be increased. Then, the residual magnetic flux density Br of the bond magnet manufactured by using the hexagonal ferrite magnetic powder for the bond magnet obtained as a result can be increased.
By setting the compression density of the molded fine particles after crushing to 2.80 g / cm ³ or more and 4.00 g / cm ³ or less in this way, a mechanism capable of increasing the residual magnetic flux density Br of the finally obtained bond magnet. Although it is not clear, the high compression density reflects that while the particle shape is proportioned, the generation of ultrafine particles that are not reflected in the particle size distribution measurement due to excessive grinding is suppressed. it is conceivable that. In particular, it is preferable at the time of high filling that there are few ultrafine particles that increase the specific surface area and significantly reduce the fluidity at the time of compounding. As a result, fine powder suitable for high filling was obtained, and it is presumed that this was due to the fact that when the fine powder and the coarse powder were mixed to produce a bonded magnet, the orientation of the fine powder and the coarse powder particles was improved. ..
It is preferable to use an attritor as a wet crusher having a stirring mechanism with a stirring blade, water is preferably used as a solvent, and the media diameter is preferably 2 mm or more and 15 mm or less.

The specific surface area of the fine powder measured by the BET one-point method is preferably 4 m ² / g or more and 20 m ² / g or less, and more preferably 5 m ² / g or more and 15 m ² / g or less.

[Mixed crushing process]
The separately obtained coarse powder and fine powder are mixed and pulverized at a ratio of the mass ratio of the coarse powder to the total mass of the coarse powder and the fine powder to be 60% by mass or more and 90% by mass or less to obtain a pulverized mixed powder. It is a process. By setting the mass ratio of the crude powder at the time of mixing to 60% by mass or more, the proportion of particles having a particle size of 5 μm or more can be set to 7% by volume or more in the particle size distribution of the hexagonal ferrite magnetic powder for bonded magnets. Further, by setting the mass ratio of the coarse powder at the time of mixing to 90% by mass or less (that is, the mass ratio of the fine powder is 10% by mass or more), the particle size distribution of the hexagonal ferrite magnetic powder for bond magnets has a particle size of less than 1 μm. The proportion of particles can be 25% by mass or more.
It is preferable to use a wet pulverizer for mixing, more preferably an attritor, and the peripheral speed of the stirring blade is preferably 1.5 m / s or more and 3.5 m / s or less.
Further, it is preferable to use a vibrating ball mill for crushing after mixing, and it is preferable to use balls having a medium diameter of 5 mm or more and 20 mm or less in the crushing process by the vibrating ball mill. It is preferable to carry out the crushing treatment using a ball having a medium diameter of 5 mm or more and 10 mm or less as the second stage after the crushing treatment is carried out. By using a vibrating ball mill, coarse particles that could not be crushed by an attritor can be crushed.

[Annealing process]
This is a step of annealing the mixed powder obtained in the mixed pulverization treatment to obtain a hexagonal ferrite magnetic powder for a bonded magnet. The annealing conditions are not particularly limited, and can be carried out under conditions known as a method for producing hexagonal ferrite magnetic powder for bonded magnets. The annealing temperature is preferably 900 ° C. or higher and 1000 ° C. or lower, and more preferably 930 ° C. or higher and 980 ° C. or lower. Further, the atmosphere at the time of annealing is preferably an oxidizing atmosphere, and more preferably an atmospheric atmosphere.

(Bond magnet and its manufacturing method)
A bonded magnet is obtained by mixing the hexagonal ferrite magnetic powder for a bonded magnet obtained by the method for producing a hexagonal ferrite magnetic powder for a bonded magnet of the present invention with a resin and a lubricant, kneading the mixture, and then molding the mixture in a magnetic field. be able to. Here, the method for manufacturing the bonded magnet is not particularly limited, and a known method can be used.

Hereinafter, the ferrite magnetic powder for a bonded magnet according to the present invention and a method for producing the same will be described in detail by way of examples.

The evaluation in the examples was performed as follows.
[Measurement of average particle size]
The average particle size (APD) was measured by an air permeation method using a specific surface area measuring device (SS-100 manufactured by Shimadzu Corporation).

[Specific surface area measurement]
The specific surface area was measured by the BET one-point method using a specific surface area measuring device (Monosorb manufactured by Kantachrome).

[Composition analysis]
The composition analysis was performed by calculating the component amount of each element by the fundamental parameter method (FP method) using a fluorescent X-ray analyzer (ZSX100e manufactured by Rigaku Co., Ltd.). In this composition analysis, the powder to be measured is packed in a measurement cell, and a pressure of 10 tons / cm ² is applied for 20 seconds for molding. The measurement mode is EZ scan mode, the measurement diameter is 30 mm, the sample form is oxide, and measurement is performed. With the time as the standard time, qualitative analysis was performed in a vacuum atmosphere, and then quantitative analysis was performed on the detected constituent elements.

[Compression density measurement]
The compression density was measured as the compression density (CD) by filling 10 g of the powder to be measured into a cylindrical mold having an inner diameter of 2.54 cmφ and then compressing it at a pressure of 1 ton / cm ² .

[Measurement of particle size distribution]
For the particle size distribution, a volume-based particle size distribution was measured at a focal length of 20 mm, a dispersion pressure of 5.0 bar, and an attraction pressure of 130 mbar using a dry laser diffraction type particle size distribution measuring device (manufactured by Nippon Laser Co., Ltd .: HELOS & RODOS).

[Magnetic characteristic measurement]
For the magnetic properties of the green compact of hexagonal ferrite magnetic powder for bond magnets, 8 g of hexagonal ferrite magnetic powder for bond magnets and 0.4 cm ³ polyester resin (P-resin manufactured by Nippon Geographical Sciences Co., Ltd.) are kneaded in a dairy pot. 7 g of the obtained kneaded product was filled in a mold having an inner diameter of 15 mmφ, compressed at a pressure of 2 ton / cm ² for 60 seconds, and the obtained molded product was withdrawn from the mold and dried at 150 ° C. for 30 minutes under pressure. A powder is obtained, and as the magnetic properties of the green compact, a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.) is used to obtain the coercive magnetic force iHc and residual magnetic flux density Br of the green compact with a measurement magnetic field of 10 kOe. It was measured.

[Measurement of MFR _A ]
92.0 parts by mass of hexagonal ferrite magnetic powder for bond magnets, 0.6 parts by mass of silane coupling agent (Z-6094N manufactured by Toray Couning Co., Ltd.), and 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. A kneaded product was prepared, and kneaded pellets having an average diameter of 2 mm were obtained from the obtained kneaded product.
The obtained kneaded pellets were placed in a melt indexer (melt indexer C-5059D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the weight of the kneaded material extruded at 270 ° C. and a load of 10 kg was measured, and this weight was measured as 10. The MFR _A of the hexagonal ferrite magnetic powder for bonded magnets was determined by converting to the amount extruded per minute.

[Measurement of magnetic properties of bonded magnet A]
The kneaded pellets obtained by the method described in the measurement of MFR _A were loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.), and the temperature was 300 ° C. and the molding pressure was 8.5 N / mm in a magnetic field of 9.7 kOe. Bonded magnet A (FC 92.0 mass%, 9.7 kOe) formed by injection in step ² and having a cylindrical shape with 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 cylinder). Got The magnetic characteristics of this bonded magnet A were measured using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.).

[Measurement of MFR _B ]
93.5 parts by mass of hexagonal ferrite magnetic powder for bond magnets, 0.6 parts by mass of silane coupling agent (Z-6094N manufactured by Toray Dow Corning Co., Ltd.), and 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. A kneaded product was prepared, and kneaded pellets having an average diameter of 2 mm were obtained from the obtained kneaded product.
The obtained kneaded pellets were placed in a melt indexer (melt indexer C-5059D2 manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the weight of the kneaded material extruded at 270 ° C. and a load of 10 kg was measured, and this weight was measured as 10. The MFR _B of hexagonal ferrite magnetic powder for bonded magnets was determined by converting to the amount extruded per minute.

[Measurement of magnetic properties of bond magnet B]
The kneaded pellets obtained by the method described in the measurement of MFR _B were loaded into an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.), and the temperature was 300 ° C. and the molding pressure was 8.5 N / mm in a magnetic field of 9.7 kOe. Bonded magnet B (FC 93.5 mass%, 9.7 kOe) formed by injection in step ² and having a cylindrical shape with 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 cylinder). Got The magnetic characteristics of this bonded magnet B were measured using a BH tracer (TRF-5BH manufactured by Toei Kogyo Co., Ltd.).

(Example 1)
1. 1. Production of hexagonal ferrite magnetic powder according to Example 1 (1) Production process of crude powder 83.2 parts by mass of iron oxide, 9.4 parts by mass of strontium carbonate, 5.2 parts by mass of lanthanum hydroxide and zinc oxide Was weighed to be 2.2 parts by mass. To the weighed product, 0.18% by mass of boric acid and 2.45% by mass of potassium chloride were added and mixed, and then water was added to granulate into spheres having a diameter of 3 to 10 mm.

The obtained granulated product was fired in a rotary kiln at 1250 ° C. for 20 minutes at a primary temperature of 1250 ° C. in a rotary kiln, and the obtained calcined product was treated with a roller mill to obtain coarse powder.

The average particle size of the obtained coarse powder was measured and found to be 1.20 μm.
The BET specific surface area of the obtained crude powder was measured and found to be 0.4 m ² / g.
The composition of the obtained crude powder was analyzed, and the composition formula of the crude powder was determined from the analytical values of Sr, La, Fe, and Zn (Sr _1-x1 La _x1 ) (Fe _1-y1 Zn _y1 ) _n1 O _19-z1 . When x1, y1, n1, and z1 were calculated, the results were x1 = 0.32, y1 = 0.021, n1 = 11.23, and z1 = 1.11.

(2) Production process of fine powder After weighing and mixing 85.5 parts by mass of iron oxide and 14.5 parts by mass of strontium carbonate, water was added to granulate into spheres having a diameter of 3 to 10 mm.

The obtained granulated product was calcined in a rotary kiln at a second temperature of 970 ° C. for 20 minutes in an atmospheric distribution atmosphere, and the obtained calcined product was treated with a roller mill to obtain fine powder. Water is added to the obtained fine powder to form a slurry so that the concentration of the fine powder is 40% by mass, and then the mixture is put into an attritor together with a steel ball having a diameter of 5.56 mm and stirred for 120 minutes (crushing treatment time). And pulverized to obtain a slurry containing fine powder after wet pulverization. Here, the rotation speed of the stirring blade was adjusted so that the peripheral speed of the stirring blade was 3.2 m / s. The obtained fine powder after wet pulverization was sampled from the slurry, separated into solid and liquid by filtration, and then dried to obtain a fine powder sample for evaluation.

The BET specific surface area of the obtained fine powder sample was measured and found to be 13.7 m ² / g.
The compression density of the obtained fine powder was measured and found to be 2.87 g / cm ³ .
The composition of the fine powder sample was analyzed, and the composition formula of the hexagonal ferrite magnetic powder for bonded magnets was (Sr _1-x2 La _x2 ) (Fe _1-y2 Zn _y ) _n2 O _19-z2 based on the analysis values of Sr and Fe. When x2, y2, n2, and z2 in the notation were calculated, the results were x2 = 0, y2 = 0, n2 = 10.80, and z2 = 1.80.
The results are shown in Table 1.

(3) Mixing and crushing step The coarse powder of (1) is so that the ratio of fine powder to coarse powder is 30:70 in the slurry containing the obtained fine powder after wet crushing contained in the crushing container of Atreiter. The crude powder obtained in the manufacturing process was added, and a mixing and pulverizing treatment was further carried out for 20 minutes by an attritor. Here, the rotation speed of the stirring blade was controlled so that the peripheral speed of the stirring blade was 3.2 m / s. Then, the slurry was filtered and separated into solid and liquid, and then dried in the air at 150 ° C. for 10 hours to obtain a dried cake. The dried cake was crushed to obtain a mixed powder. The obtained mixed powder was pulverized with a vibrating ball mill (manufactured by Murakami Seiki Seisakusho: Uras Vibrator KEC-8-YH) to obtain a pulverized mixed powder. As the crushing treatment conditions, a steel ball having a medium diameter of 12 mm was used, and the process was carried out for 28 minutes under the conditions of a rotation speed of 1800 rpm and an amplitude of 8 mm. The pulverization treatment was carried out for 28 minutes under the conditions of a rotation speed of 1800 rpm and an amplitude of 8 mm.

(4) Annealing Step The pulverized mixed powder was annealed in the air at 970 ° C. for 30 minutes to obtain a hexagonal ferrite magnetic powder for a bonded magnet according to Example 1.

(5) Evaluation of Hexagonal Ferrite Magnetic Powder for Bonded Magnet The hexagonal ferrite magnetic powder for bonded magnet according to Example 1 was subjected to a tube voltage of 40 kV using a powder X-ray diffractometer (Miniflex 600 manufactured by Rigaku Co., Ltd.). The measurement was performed by powder X-ray diffraction method (XRD) with a tube current of 15 mA, a measurement range of 15 ° to 60 °, a scan speed of 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 hexagonal ferrite magnetic powder for the bonded magnet of this example had a magnetoplumbite-type crystal structure. This result was the same in Examples 2 to 4 and Comparative Examples 1 to 5 described below.
The composition of the hexagonal ferrite magnetic powder for bond magnets according to Example 1 was analyzed, and the composition formula of the hexagonal ferrite magnetic powder for bond magnets was determined from the analytical values of Sr, La, Fe, and Zn (Sr _1-x La _x) . ) (Fe _1-y Zn _y ) When x, y, n, z when expressed as _n O _19-z are calculated, x = 0.21, y = 0.014, z = 0.90, n = It was 11.38.

When the particle size distribution of the hexagonal ferrite magnetic powder for a bonded magnet according to Example 1 was measured, the proportion of particles having a size of less than 1 μm was 29.1% by volume, and the proportion of particles having a size of 1 μm or more and less than 5 μm was 61.4% by volume. The proportion of particles having a size of 5 μm or more was 9.5% by volume.

Regarding the hexagonal ferrite magnetic powder for bonded magnets according to Example 1, the compression density was measured to be 3.67 g / cm ³ , and the specific surface area was measured to be 2.51 m ² / g, and the average particle size was measured. As a result, it was 1.20 μm.

When the magnetic properties of the green compact of the hexagonal ferrite magnetic powder for bonded magnets according to Example 1 were measured, the coercive force p-iHc of the green compact was 2390 Oe, and the residual magnetic flux density p-Br of the green compact was 1990 G. there were.

The MFR _A of the hexagonal ferrite magnetic powder for a bonded magnet according to Example 1 was 91.0 g / 10 min.
When the magnetic characteristics of the bonded magnet A using the hexagonal ferrite magnetic powder for the bonded magnet according to Example 1 were measured, the coercive force iHc was 2355Oe, the residual magnetic flux density Br was 3211G, and the maximum energy product BH _max was 2.52MGOe. there were.

The MFR _B of the hexagonal ferrite magnetic powder for a bonded magnet according to Example 1 was 28.2 g / 10 min.
When the magnetic characteristics of the bond magnet B using the hexagonal ferrite magnetic powder for the bond magnet according to Example 1 were measured, the coercive force iHc was 2467Oe, the residual magnetic flux density Br was 3320G, and the maximum energy product BH _max was 2.69MGOe. there were.

(Example 2)
The rotation speed of the stirring blades when wet pulverizing the fine powder and performing pulverization and mixing was adjusted so that the peripheral speed of the stirring blade was 1.6 m / s, and the pulverization processing time for the wet pulverization of the fine powder was 60. Hexagonal ferrite magnetic powder for bonded magnets was prepared by the same procedure as in Example 1 except that the amount was divided, and the evaluation was performed under the same conditions as in Example 1.

(Example 3)
The rotation speed of the stirring blades when wet pulverizing the fine powder and performing pulverization and mixing was adjusted so that the peripheral speed of the stirring blade was 1.6 m / s, and the concentration of the fine powder was 20 in the process of producing the fine powder. Hexagonal ferrite magnetic powder for bonded magnets was prepared by the same procedure as in Example 1 except that the slurry was made into a slurry so as to be by mass%, and evaluated under the same conditions as in Example.

(Example 4)
The rotation speed of the stirring blades when wet pulverizing and pulverizing and mixing the fine powder was adjusted so that the peripheral speed of the stirring blade was 1.6 m / s, and the concentration of the fine powder was 20 mass in the fine powder manufacturing process. Hexagonal ferrite magnetic powder for bonded magnets was prepared by the same procedure as in Example 1 except that it was made into a slurry so as to be% and that the pulverization treatment using a steel ball having a medium diameter of 8 mm was not performed. It was prepared and evaluated under the same conditions as in Example 1.

(Example 5)
Hexagonal ferrite magnetic powder for bonded magnets was prepared by the same procedure as in Example 1 except that the pulverization treatment time for wet pulverization when wet pulverizing fine powder and pulverizing and mixing was set to 60 minutes. It was evaluated under the same conditions as 1.

(Example 6)
Hexagonal ferrite magnetic powder for bonded magnets was prepared by the same procedure as in Example 1 except that the pulverization treatment time for wet pulverization was 30 minutes when the fine powder was wet pulverized and when the pulverization and mixing were performed. It was evaluated under the same conditions as 1.

(Comparative Example 1)
The crude powder was obtained by the same operation as in the process of producing the crude powder in (1) of Example 1. Water was added to the obtained coarse powder to form a slurry so that the concentration of the coarse powder was 40% by mass, and then the mixture was put into an attritor together with a steel ball having a diameter of 5.56 mm and pulverized for 20 minutes. After wet pulverization of the coarse powder, a slurry containing the powder was obtained. Here, the peripheral speed of the stirring blade was adjusted to 3.2 m / s. Then, the slurry was filtered and dried in the air at 150 ° C. for 10 hours to obtain a dried cake. After the dried cake was crushed, it was crushed by a vibration ball mill (manufactured by Murakami Seiki Seisakusho: Uras Vibrator KEC-8-YH). As the dry pulverization treatment conditions, a steel ball having a medium diameter of 12 mm was used, and the process was carried out for 28 minutes under the conditions of a rotation speed of 1800 rpm and an amplitude of 8 mm. Further, a steel ball having a medium diameter of 8 mm was used for the obtained pulverized powder. The pulverization treatment was carried out for 28 minutes under the conditions of a rotation speed of 1800 rpm and an amplitude of 8 mm. The powder obtained by the dry pulverization treatment was annealed in the air at 970 ° C. for 30 minutes to prepare a hexagonal ferrite magnetic powder for a bonded magnet according to Comparative Example 1, which was evaluated under the same conditions as in Examples.
Here, when an attempt was made to manufacture the bond magnet B in the same procedure as in the first embodiment, the kneaded product obtained by kneading the mixture did not flow, and the MFR _B was measured and the bond magnet B was manufactured. I couldn't.

(Comparative Example 2)
Hexagon for bonded magnets by the same procedure as in Comparative Example 1 except that the first temperature in the crude powder manufacturing process was set to 1300 ° C. and the pulverization treatment using a steel ball having a medium diameter of 8 mm was not performed. Crystalline ferrite magnetic powder was prepared and evaluated under the same conditions as in Examples.
Here, when an attempt was made to manufacture the bond magnet B in the same procedure as in the first embodiment, the kneaded product obtained by kneading the mixture did not flow, and the MFR _B was measured and the bond magnet B was manufactured. I couldn't.

(Comparative Example 3)
Hexagon for bonded magnets by the same procedure as in Comparative Example 1 except that the first temperature in the crude powder manufacturing process was set to 1250 ° C. and the pulverization treatment using a steel ball having a medium diameter of 8 mm was not performed. Crystalline ferrite magnetic powder was prepared and evaluated under the same conditions as in Examples.
Here, when an attempt was made to manufacture the bond magnet B in the same procedure as in the first embodiment, the kneaded product obtained by kneading the mixture did not flow, and the MFR _B was measured and the bond magnet B was manufactured. I couldn't.

(Comparative Example 4)
Hexagon for bonded magnets by the same procedure as in Comparative Example 1 except that the first temperature in the crude powder manufacturing process was set to 1200 ° C. and the pulverization treatment using a steel ball having a medium diameter of 8 mm was not performed. Crystalline ferrite magnetic powder was prepared and evaluated under the same conditions as in the examples.
Here, when an attempt was made to manufacture the bond magnet B in the same procedure as in the first embodiment, the kneaded product obtained by kneading the mixture did not flow, and the MFR _B was measured and the bond magnet B was manufactured. I couldn't.

(Comparative Example 5)
Hexagon for bonded magnets by the same procedure as in Comparative Example 1 except that the first temperature in the crude powder manufacturing process was set to 1150 ° C. and the pulverization treatment using a steel ball having a medium diameter of 8 mm was not performed. Crystalline ferrite magnetic powder was prepared and evaluated under the same conditions as in Examples.
Further, when the production of the bond magnet A and the bond magnet B was attempted with respect to the obtained hexagonal ferrite magnetic powder for the bond magnet by the same procedure as in Example 1, in each case, the mixture was kneaded and obtained. The kneaded product did not flow, and the measurement of MFR _A and MFR _B and the production of the bond magnet A and the bond magnet B could not be performed.

The above results are shown in Tables 1 to 3.

From the results of Example 1 and Comparative Example 1, the fine particles obtained by firing at a second temperature lower than the first firing temperature at which the coarse powder is obtained are mixed and pulverized with the coarse powder and annealed. As a result, the proportion of particles having a particle size of less than 1 μm is 25% by volume or more and the proportion of particles having a particle size of 5 μm or more is 7% by volume or more in the particle size distribution as the hexagonal ferrite magnetic powder for bonded magnets. It is possible to obtain magnetic powder having a compression density of 3.60 g / cm ³ or more, and the residual magnetic flux density Br when a bonded magnet is manufactured using the obtained hexagonal ferrite magnetic powder for bonded magnets is high. It can be seen that a bond magnet can be obtained.
Further, from the results of Examples 1 and 2 to 4, in the method for producing hexagonal ferrite magnetic powder for bonded magnets, the peripheral speed of the stirring blade for the fine powder is set to 0.5 m / s or more and 2.5 m / s or less. The MFR _A of the obtained hexagonal ferrite magnetic powder for bonded magnets can be 100 g / 10 min or more by mixing the fine powder and the coarse powder after subjecting to the pulverization treatment by a controlled wet bead mill. Further, it can be seen that a bond magnet having a high residual magnetic flux density Br when a bond magnet is manufactured using the obtained hexagonal ferrite magnetic powder for a bond magnet can be obtained.
From the comparison between Examples 2 and 6 and the comparison with Examples 3 and 5, the compression densities of the fine powders of Examples 2 and 3 are found to be in Examples even though the specific surface areas of the fine powders are almost the same. It is larger than the compression densities of 6 and 5, and the characteristics of the bonded magnet are also excellent. By reducing the peripheral speed of the stirring blade during wet pulverization, fine powder suitable for high filling can be obtained, and when the fine powder and coarse powder are mixed to produce a bonded magnet, fine powder and coarse powder particles are obtained. It can be considered that this is because the orientation of the particles has improved.
From the results of Comparative Examples 2 to 5, in the conventional method for producing SrLaZn-based hexagonal ferrite magnetic powder, the proportion of particles having a particle size of less than 1 μm is 25% by volume or more and the particle size is 5 μm or more in the particle size distribution. It is not possible to obtain hexagonal ferrite magnetic powder having a ratio of 7% by volume or more, and as a result, the MFR _A of the hexagonal ferrite magnetic powder is as small as 90 g / 10 min or less, and the hexagonal ferrite magnetic powder is used to bond magnets. It was found that only a bonded magnet having a low residual magnetic flux density Br can be obtained even if the magnet is manufactured.

Claims (10)

Composition formula (Sr _1-x La _x ) (Fe _1-y Zn _y ) _n O _19-z (However, 0.01 ≦ x ≦ 0.50, 0.010 ≦ y ≦ 0.040, 10.00 ≦ n ≦ 12.50, z = 19- [2 (1-x) + 3x + n {3 (1-y) + 2y}] / 2), based on the volume measured by the laser diffraction type particle size distribution measuring device. In the particle size distribution, the proportion of particles having a particle size of less than 1 μm is 25% by volume or more and 40% by volume or less, the proportion of particles having a particle size of 1 μm or more and less than 5 μm is 30% by volume or more and 65% by volume or less, and the particle size is 5 μm or more. Hexagonal ferrite magnetic powder for bonded magnets, wherein the proportion of particles in the particle is 7% by volume or more and 30% by volume or less. The mixer is filled with 92.0 parts by mass of the hexagonal ferrite magnetic 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 a kneaded product, and the obtained kneaded product was placed in a melt indexer to weigh the kneaded product extruded at 270 ° C. and a load of 10 kg. The hexagonal crystal for a bond magnet according to claim 1, wherein the fluidity MFR _A of the kneaded product, which is measured and converted into the mass extruded per 10 minutes, is 100 g / 10 min or more. Ferrite magnetic powder. The compression density of the molded product obtained by filling 10 g of the hexagonal ferrite magnetic powder for a bonded magnet into a cylindrical mold having an inner diameter of 2.54 cmφ and then compressing it at a pressure of 1 ton / cm ³ is 3.60 g / cm ³ or more. , The hexagonal ferrite magnetic powder for a bonded magnet according to claim 1 or 2. In the volume-based particle size distribution measured by the laser diffraction type particle size distribution measuring device, the proportion of particles having a particle size of 1 μm or more and less than 5 μm is 50% by volume or more and 65% by volume or less, and the proportion of particles having a particle size of 5 μm or more is The hexagonal ferrite magnetic powder for a bonded magnet according to any one of claims 1 to 3, which is 7% by volume or more and 20% by volume or less. Composition formula (Sr _1-x1 La _x1 ) (Fe _1-y1 Zn _y1 ) _n1 O _19-z1 (However, 0.01 ≦ x1 ≦ 0.50, 0.010 ≦ y1 ≦ 0.040, 10.00 ≦ n1 ≦ 12.50, z1 = 19- [2 (1-x1) + 3x1 + n1 {3 (1-y1) + 2y1}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, the first The process of firing at one temperature to obtain coarse powder of hexagonal ferrite magnetic powder,
Composition formula (Sr _1-x2 La _x2 ) (Fe _1-y2 Zn _y2 ) _n2 O _19-z2 (However, 0 ≦ x2 ≦ 0.50, 0 ≦ y2 ≦ 0.040, 10.00 ≦ n2 ≦ 12. 50, z2 = 19- [2 (1-x2) + 3x2 + n {3 (1-y2) + 2y2}] / 2) After mixing the powder that is the raw material of the hexagonal ferrite magnetic powder, from the first temperature The process of obtaining fine powder of hexagonal ferrite magnetic powder by firing at a low second temperature,
The coarse powder and the fine powder are mixed and pulverized at a ratio of the mass ratio of the coarse powder to the total mass of the coarse powder and the fine powder to be 60% by mass or more and 90% by mass or less to obtain a pulverized mixed powder. Process and
The step of annealing the pulverized mixed powder and
A method for producing hexagonal ferrite magnetic powder for bonded magnets, including. The step of obtaining the fine powder includes mixing the powder as a raw material, baking the powder at a second temperature, and then pulverizing the powder. The bond magnet according to claim 5, wherein the compression density of the molded product compressed at a pressure of 1 ton / cm ³ after being filled in a mold is 3.00 g / cm ³ or more and 4.00 g / cm ³ or less. A method for producing hexagonal ferrite magnetic powder. The method for producing a hexagonal ferrite magnetic powder for a bonded magnet according to claim 5 or 6, wherein the first temperature is 1220 ° C. or higher and 1400 ° C. or lower. The method for producing a hexagonal ferrite magnetic powder for a bonded magnet according to any one of claims 5 to 7, wherein the second temperature is 900 ° C. or higher and 1000 ° C. or lower. A bonded magnet containing the hexagonal ferrite magnetic powder for a bonded magnet according to any one of claims 1 to 4 and a resin. A method for manufacturing a bonded magnet using hexagonal ferrite magnetic powder for a bonded magnet obtained by the manufacturing method according to any one of claims 5 to 8.

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