JP2015182028A - Bead mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bead mill which can shorten a time required for flattening and improve the magnetic permeability of magnetic particles.SOLUTION: An aspect of the bead mill of this invention, being a bead mill used for the flattening treatment of magnetic particles, includes a mill body, a rotary shaft part, and a projection group. The projection group comprises a first projection projecting from the rotary shaft part to one side in a radial direction and a second projection projecting to an exact opposite side of the first projection with respect to the rotary shaft part. A plurality of stages provided with the first and second projections are provided along the axial directions, where adjacent stages are arranged with a displacement of 90° around the axis. When the bore diameter of an agitation part is D, a length in the axial direction of the projection group is 0.165D or more and 0.185D or less, and a length in a projecting direction of the projection group is 0.25D or more and 0.27D or less. When the volume of the agitation part is V, a volume which is a combination of the volume of the first projection and that of the second projection is 0.0062V or more and 0.0072V or less.

Description

  The present invention relates to a bead mill.

Depending on the shape of the particles, various properties can be improved. For example, it is known that light scattering can be improved by making titanium oxide having a high refractive index into a star shape (for example, Patent Document 1).
Further, it is known that the magnetic permeability of magnetic particles can be improved by flattening spherical magnetic particles (for example, Patent Document 2). Examples of a method for flattening the magnetic particles include a method of stirring the magnetic particles using a stirring device.

As a stirring device, for example, a bead mill is known (for example, Patent Document 3).
Patent Document 1 describes a bead mill in which a rotor having a rotor pin is provided, and the raw slurry supplied to the bead mill by the rotor pin is stirred by the rotation of the rotor.

JP 2010-001212 A JP 2012-134463 A International Publication No. 2007/108217

  However, when the above bead mill is used, there is a problem that it takes time for the flattening process. Further, even if the treatment time is increased, the magnetic particles are not sufficiently flattened, and the magnetic permeability of the magnetic particles may not be sufficiently improved.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a bead mill capable of shortening the time required for flattening and improving the magnetic permeability of magnetic particles.

  One aspect of the bead mill of the present invention is a bead mill used for flattening processing of magnetic particles, the cylindrical mill body in which the magnetic particles are accommodated, the cylinder body of the mill body provided in the mill body A rotating shaft portion coaxial with the shaft, and a projecting portion group that protrudes from the rotating shaft portion in the radial direction of the rotating shaft portion, and includes a plurality of projecting portions, and the projecting portion group includes the rotating shaft. A first projecting portion projecting to one side in a radial direction of the rotating shaft portion from a portion, and a second projecting portion projecting to the opposite side of the first projecting portion with respect to the rotating shaft portion, A plurality of steps in which the first protrusion and the second protrusion are provided are provided along the axial direction of the rotating shaft, and the adjacent steps are shifted by 90 ° around the axis of the rotating shaft. Of a stirring unit that is disposed and stirs the magnetic particles in the mill body. When the diameter is D, the axial length of the rotating shaft portion in the projecting portion group is 0.165D or more and 0.185D or less, and the length of the projecting portion group in the projecting direction is 0.25D or more and 0.27D or less, and when the volume of the stirring unit is V, the volume of the volume of one of the first protrusions and the volume of one of the second protrusions is It is 0.0062V or more and 0.0072V or less.

  The total volume of the protrusion group may be 0.081V or more and less than 1.0V.

The total projected area when the projecting portion group is projected in a direction perpendicular to the direction in which the projecting portion group projects and perpendicular to the axial direction of the rotating shaft portion is 0.85D ² or more and 1.2D. It is good also as a structure which is ² or less.

  One aspect of the bead mill of the present invention is a bead mill used for particle flattening treatment, a cylindrical mill main body in which particles are accommodated, a cylindrical shaft of the mill main body provided in the mill main body, A coaxial rotation shaft portion, and a protrusion group that is provided so as to protrude from the rotation shaft portion in the radial direction of the rotation shaft portion, and that includes a plurality of protrusion portions, and the protrusion portion group extends from the rotation shaft portion. A first projecting portion projecting to one side in a radial direction of the rotating shaft portion; and a second projecting portion projecting to the opposite side of the first projecting portion with respect to the rotating shaft portion, A plurality of steps provided with the protruding portion and the second protruding portion are provided along the axial direction of the rotating shaft portion, and the adjacent steps are arranged 90 ° apart from each other around the axis of the rotating shaft portion. , D is the inner diameter of the stirring unit for stirring the particles in the mill body. Sometimes, the axial length of the rotating shaft portion in the projecting portion group is 0.165D or more and 0.185D or less, and the length in the projecting direction of the projecting portion group is 0.25D or more, 0.27D or less, and when the volume of the stirring unit is V, the total volume of one of the first protrusions and one of the second protrusions is 0.0062V or more, It is 0.0072V or less.

  The particles may be metal particles.

  According to one aspect of the present invention, a bead mill that can shorten the time required for flattening and improve the magnetic permeability of magnetic particles is provided.

It is a schematic block diagram which shows typically the bead mill of this embodiment. It is a partial expansion perspective view which shows the stirring pin of the bead mill of this embodiment. It is a scanning electron micrograph which shows the result of a present Example.

Hereinafter, a bead mill according to an embodiment of the present invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiment, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

  In the present specification, “magnetic permeability” means relative magnetic permeability, which is a ratio to vacuum magnetic permeability, unless otherwise specified.

FIG. 1 is a schematic configuration diagram schematically showing a bead mill 10 of the present embodiment. In FIG. 1, the mill body 20 is shown in cross section, and the inside of the mill body 20 is illustrated.
In the following description, an XYZ coordinate system is set, and the positional relationship of each member will be described with reference to this XYZ coordinate system. At this time, the axial direction of the shaft 40 (see FIG. 1) is the Z-axis direction, one direction orthogonal to the Z-axis direction is the X-axis direction (left-right direction in FIG. 1), and the direction orthogonal to the Z-axis direction and the X-axis direction is The Y-axis direction is assumed. In the present embodiment, the Z-axis direction is the vertical direction.

In the present embodiment described below, the bead mill 10 will be described as an apparatus that is used for flattening of magnetic particles using, for example, magnetic particles as an object to be processed.
In addition, the bead mill 10 of this embodiment can be used suitably also for the particle | grains which can improve a characteristic by flattening, for example, a metal particle.

  As shown in FIG. 1, the bead mill 10 includes a mill body 20, a shaft (rotating shaft portion) 40, a separator 50, and a stirring pin group (projecting portion group) 30.

[Mill body]
The mill body 20 is a cylindrical container. Inside the mill body 20, a shaft 40 is inserted, and a stirring pin group 30 and a separator 50 are accommodated. Inside the mill body 20, a stirring unit 21 is provided on the stirring pin group 30 side (−Z side) from the separator 50.
The stirring unit 21 is a part that stirs the raw slurry accommodated in the mill body 20. The stirring unit 21 is the entire internal space on the stirring pin group 30 side (−Z side) with respect to the separator 50 in the internal space of the mill body 20.

The shape of the stirring unit 21 in the mill body 20, that is, the ratio between the vertical length (Z-axis direction length) and the inner diameter D is, for example, such that the volume V of the stirring unit 21 satisfies the following formula (1). Is set.
Formula (1) 0.548πD ³ ≦ V ≦ 0.677πD ³

More preferably, the volume V of the stirring unit 21 is set so as to satisfy the following expression (2).
Formula (2) V = 0.5625πD ³
By setting the volume V of the stirring unit 21 in such a numerical range, when setting the stirring pin length W1 and the stirring pin thickness W2 of the stirring pin group 30 described later, the volume V of the stirring unit 21 is set to The volume per stage of the stirring pin group 30 can be set within a preferable range.

  The inside of the mill body 20 is filled with a dispersion medium. The dispersion medium applies mechanical energy to the raw slurry introduced into the mill body 20 to flatten the magnetic particles contained in the raw slurry.

  Examples of the dispersion medium include metals such as aluminum and steel or metal compounds, oxide sintered bodies such as alumina, zirconia, silicon dioxide, and titania, nitride sintered bodies such as silicon nitride, and silicon carbide. Granules having a predetermined hardness, such as glass zirconia beads such as silicide sintered body, soda glass, lead glass, and high specific gravity glass, glass beads, titania beads, and metal beads can be selected.

  The amount filled with the dispersion medium is, for example, 5% by volume or more and 50% by volume or less of the inner volume of the mill body 20. When it is less than 5% by volume of the inner volume of the mill body 20, mechanical energy cannot be appropriately applied to the raw slurry, and when it is greater than 50% by volume, production of flattened magnetic particles is produced. Efficiency is reduced.

  The mill body 20 includes a cylindrical portion 20 a, a disk-shaped bottom wall portion 20 b that closes an opening on the lower side in the vertical direction (−Z side) of the cylindrical portion 20 a, and the vertical direction of the cylindrical portion 20 a together with the shaft 40. A disc-shaped top wall portion 20c that closes the upper (+ Z side) opening.

  The bottom wall portion 20b is provided with a supply port 22 formed through the bottom wall portion 20b and connected to the output end of the pump P. A through hole 20d through which the shaft 40 is inserted is formed at the center of the top wall portion 20c in plan view (XY plane view).

[shaft]
The shaft 40 is inserted into the through hole 20d of the top wall portion 20c and is provided inside the mill body 20. The shaft 40 is provided coaxially with the cylindrical axis of the cylindrical portion 20 a of the mill body 20. A separator 50 and a stirring pin group 30 are connected to the shaft 40 inside the mill body 20.

  A drive device (not shown) is connected to the shaft 40 and is driven to rotate about the axis by the drive device. When the shaft 40 is rotationally driven, the separator 50 and the stirring pin group 30 connected to the shaft 40 are rotationally driven.

[separator]
The separator 50 is a centrifuge that separates the raw slurry mixed in the mill body 20 and the dispersion medium. The configuration of the separator 50 is not particularly limited as long as the raw slurry and the dispersion medium can be separated. For example, the separator 50 may be configured to include a pair of disks provided at regular intervals and an impeller formed of a blade that connects the pair of disks.

[Stirring pin group]
The stirring pin group 30 is a member that protrudes from the shaft 40. The shape of the stirring pin group 30 is, for example, a cylindrical shape in the present embodiment. The agitation pin group 30 rotates about the axis of the shaft 40 as the shaft 40 rotates, and agitates the dispersion medium filled in the agitation unit 21 in the mill body 20 and the raw material slurry accommodated in the agitation unit 21.
The agitation pin group 30 includes agitation pins (first protrusions) 31a, 31b, 31c, 31d, agitation pins (second protrusions) 32a, 32b, 32c, 32d, and agitation pins (first protrusions) 33a, 33b, 33c, and stirring pins (second protrusions) 34a, 34b, 34c.

  In the present embodiment, the stirring pins 31a to 31d, the stirring pins 33a to 33c, the stirring pins 32a to 32d, and the stirring pins 34a to 34c have the same shape and size. As a representative, only the stirring pin 31a, the stirring pin 32a, the stirring pin 33a, and the stirring pin 34a may be described.

FIG. 2 is a partially enlarged perspective view showing the stirring pin group 30.
As shown in FIG. 2, the stirring pin 31 a is a cylindrical member that protrudes from the shaft 40 to one side (+ X side) in the radial direction (X-axis direction) of the shaft 40. The same applies to the stirring pins 31b to 31d. As shown in FIG. 1, the agitation pins 31a, 31b, 31c, and 31d are provided along the axial direction (Z-axis direction) of the shaft 40, and from the vertical direction upper side (+ Z side) to the lower side (−Z side). It is arranged at equal intervals in this order.

  The agitating pin 32a is provided at the same position as the agitating pin 31a in the axial direction (Z-axis direction) of the shaft 40. As shown in FIG. 2, the agitating pin 31a is opposite to the agitating pin 31a (on the −X side). It is a columnar member which protrudes in the. The stirring pin 32a is provided so as to be coaxial with the stirring pin 31a. The same applies to the stirring pins 32b to 32d. As shown in FIG. 1, the agitation pins 32a, 32b, 32c, and 32d are provided along the axial direction (Z-axis direction) of the shaft 40, from the upper side in the vertical direction (+ Z side) to the lower side (−Z side). It is arranged at equal intervals in this order.

  As shown in FIG. 2, the stirring pin 33a is a cylindrical member that protrudes from the shaft 40 to one side (−Y side) in the direction (Y-axis direction) perpendicular to the direction in which the stirring pin 31a protrudes (X-axis direction). is there. The same applies to the stirring pins 33b and 33c. As shown in FIG. 1, the stirring pin 33a is provided between the stirring pin 31a and the stirring pin 31b in the axial direction of the shaft 40 (Z-axis direction). The stirring pins 33a, 33b, and 33c are provided along the axial direction (Z-axis direction) of the shaft 40, and are arranged at equal intervals in this order from the upper side in the vertical direction (+ Z side) to the lower side (−Z side). Has been.

  The agitating pin 34a is provided at the same position as the agitating pin 33a in the axial direction (Z-axis direction) of the shaft 40, and as shown in FIG. 2, a cylinder protruding from the shaft 40 to the opposite side (+ Y side) to the agitating pin 33a. It is a member. The stirring pin 34a is provided so as to be coaxial with the stirring pin 33a. The same applies to the stirring pins 34b and 34c. The stirring pins 34a, 34b, and 34c are provided along the axial direction (Z-axis direction) of the shaft 40, and as shown in FIG. 1, from the upper side in the vertical direction (+ Z side) toward the lower side (−Z side). These are arranged at equal intervals in this order.

  In the present embodiment, the position where the stirring pin group 30 is provided in the vertical direction (Z-axis direction) is referred to as a “stage”. A plurality of steps are provided along the vertical direction (Z-axis direction). In FIG. 1, for convenience of explanation, only seven stages are shown, but in the present embodiment, for example, twelve or more stages are provided. By setting in this way, the ratio of the magnetic particles colliding with the stirring pin group 30 can be increased, and the time required for the flattening process can be further shortened.

  In the present embodiment, the number of stirring pins provided per stage is two. For example, the stirrer pin 31a and the stirrer pin 32a are provided in the uppermost vertical direction (+ Z side), and the stirrer pin 33a and the stirrer pin 34a are disposed on the lower stage (−Z side) thereof. Is provided. The stage provided with the stirring pin 31a and the stirring pin 32a and the stage provided with the stirring pin 33a and the stirring pin 34a are alternately provided. That is, the protruding direction of the stirring pin in the adjacent steps is vertical. In other words, the adjacent steps are provided 90 ° apart from each other around the axis of the shaft 40.

The stirring pin length W1 in the protruding direction (X-axis direction) of the stirring pin 31a is 0.250D or more and 0.270D or less with respect to the inner diameter D of the stirring unit 21.
The stirring pin thickness W2 of the stirring pin 31a is 0.165D or more and 0.185D or less with respect to the inner diameter D of the stirring unit 21.
The same applies to the stirring pins 31b to 31d, the stirring pins 32a to 32d, the stirring pins 33a to 33c, and the stirring pins 34a to 34c.

  In this specification, the thickness of the stirring pin group 30 means the length of the shaft 40 in the stirring pin group 30 in the axial direction (Z-axis direction). For example, in the present embodiment, since the stirring pin group 30 has a cylindrical shape, the stirring pin thickness W <b> 2 is the diameter of the stirring pin group 30.

  The agitation pin group 30 as described above has a larger agitation pin length W1 and agitation pin thickness W2 than the conventional agitation pins. By setting to such a numerical range, the time required for the flattening process of the magnetic particles can be shortened.

The volume of the stirring pin group 30 per stage, that is, for example, the total volume of the stirring pin 31 a and the stirring pin 32 a is 0.0062 V or more and 0.0072 V with respect to the volume V of the stirring unit 21. It is as follows.
The total volume of the stirring pin group 30, that is, the total volume of all the stirring pins included in the stirring pin group 30 is 0.081 V or more and less than 1.0 V.

The total projected area of the stirring pin group 30 is 0.85D ² or more and 1.2D ² with respect to the inner diameter D of the stirring unit 21. The projected area is an area when projected in a direction perpendicular to the protruding direction of each stirring pin group 30 and perpendicular to the axial direction of the shaft 40 (Z-axis direction). That is, in the stirring pins 31a to 31d and the stirring pins 32a to 32d, it means an area in a side view (ZX view) shown in FIG. 1, and in the stirring pins 33a to 33c and the stirring pins 34a to 34c, the YZ view is shown. Means the area. The total projected area of the stirring pin group 30 is the total area of the projected areas of all the stirring pin groups 30.

  By setting the volume and projected area of the stirring pin group 30 in the above numerical range, the time required for the flattening process of the magnetic particles can be further shortened.

Hereinafter, a flattening method using the bead mill 10 of the present embodiment will be described.
First, the raw material slurry containing the magnetic particles as the object to be processed is accommodated in the mill body 20.
The raw material slurry stored in the raw material tank 60 is conveyed by the pump P, and is accommodated from the supply port 22 into the mill body 20, more specifically, into the stirring unit 21. In the present embodiment, the raw material slurry is a liquid material in which the magnetic particles that are the object to be processed of the present embodiment are dispersed in a dispersion medium. The raw slurry accommodated in the stirring unit 21 in the mill body 20 from the supply port 22 is mixed with the dispersion medium.

[Magnetic particles]
The magnetic particles are not particularly limited as long as they are magnetic particles. For example, one or two of nickel (Ni), copper (Cu), cobalt (Co), zinc (Zn), and molybdenum (Mo) are used. The above or two or more alloys selected from these can be used.
Examples of the two types of alloys include Fe-Ni alloys, Fe-Si alloys, Fe-Co alloys, Fe-Cr alloys, and the like. Examples of the three types of alloys include Fe-Si-Al alloys and Fe-Fe alloys. -Cr-Si alloy etc. are mentioned.

  The average primary particle size of the magnetic particles is not particularly limited, but when the fine particles are prepared as the magnetic particles after the flattening treatment, the average primary particle size of the magnetic particles is preferably 200 nm or less. Magnetic particles having an average primary particle size of 200 nm or less are preferable because the particle surface has high activity, and thus the affinity between particles is increased and adhesion between particles is promoted.

  On the other hand, if the average primary particle diameter of the magnetic particles is too small, the surface activity of the magnetic particles is too high, and the magnetic particles are remarkably easily oxidized, which may deteriorate the magnetic properties. Therefore, the average primary particle diameter of the magnetic particles is preferably 50 nm or more, and the practical lower limit is about 30 nm.

  The production method of the magnetic particles is not particularly limited, and those produced by a known method such as a liquid phase reduction method or an atomization method can be used. When synthesizing magnetic particles having an average primary particle size of 200 nm or less, it is preferable to use a liquid phase reduction method.

[Dispersion medium]
Examples of the dispersion medium include hydrocarbons, that is, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. One of these solvents may be used as a dispersion medium, or a mixture of two or more may be used.
In this embodiment, for example, a low polarity organic solvent such as xylene or toluene is used as the dispersion medium.

Next, the raw material slurry accommodated in the mill main body 20 is stirred together with the dispersion medium filled in the mill main body 20.
The shaft 40 is rotationally driven by a drive unit (not shown), and the separator 50 and the stirring pin group 30 are rotationally driven. Thus, the raw slurry and the dispersion medium are stirred by the stirring pin group 30 that is rotationally driven. Thereby, the magnetic particles in the raw material slurry are flattened.

The details of the principle of flattening the magnetic particles are unknown, but are thought to be based on the following principle.
By stirring the raw material slurry and the dispersion medium, the dispersion medium collides with the magnetic particles in the raw material slurry, and mechanical energy is applied to the magnetic particles. The magnetic particles to which mechanical energy is applied are pressed and adhered to each other. Then, the magnetic particles are processed in a two-dimensional direction by further applying mechanical energy that generates a shearing force to the adhered magnetic particles from the dispersion medium. It is considered that the magnetic particles are flattened by repeating such a phenomenon.

Next, the raw slurry and the dispersion medium are separated.
The raw material slurry stirred by the stirring unit 21 in the mill body 20 is sequentially moved upward in the vertical direction (+ Z side) by the pressure of the raw material slurry continuously supplied from the pump P. Then, the raw material slurry reaching the separator 50 is separated into the raw material slurry and the dispersion medium by the separator 50. The separated raw material slurry is discharged from the mill main body 20 through a discharge port (not shown).

  The supply amount of the raw material slurry supplied from the pump P can be determined according to the time required for the flattening process. When the time required for the flattening process is short, the supply amount of the raw slurry is set so as to increase, and the moving speed of the raw slurry upward in the vertical direction (+ Z side) in the mill body 20 is increased. On the other hand, when the time required for the flattening process is long, the supply amount of the raw slurry is set to be small, and the moving speed of the raw slurry upward in the mill body 20 is slow. In addition, the raw material slurry supplied from the pump P may be intermittent supply instead of continuous supply.

  By the above, the flattening process using the bead mill 10 of this embodiment is complete | finished, and the raw material slurry containing the flattened magnetic particle is obtained.

  According to this embodiment, the stirring pin length W1 in the protruding direction (X-axis direction) of the stirring pin 31a is 0.250D or more and 0.270D or less with respect to the inner diameter D of the stirring unit 21, and the stirring is performed. The stirring pin thickness W2 of the pin 31a is 0.165D or more and 0.185D or less with respect to the inner diameter D of the stirring unit 21. That is, in this embodiment, the stirring pin length W1 and the stirring pin thickness W2 of the stirring pin group 30 with respect to the inner diameter D of the stirring unit 21 are set larger than those of the conventional stirring pin. Therefore, when the raw slurry and the dispersion medium are agitated, the number of dispersion media that come into contact with the agitation pin group 30 increases. The dispersion medium in contact with the stirring pin group 30 is increased in relative speed with respect to the stirring pin group 30 by applying mechanical energy from the stirring pin group 30. The dispersion medium whose relative speed is increased collides with the magnetic particles, thereby applying mechanical energy to the magnetic particles as described above. Therefore, according to the present embodiment, the increase in the dispersion media colliding with the stirring pin group 30 increases the mechanical energy applied to the magnetic particles from the dispersion media per unit time, and the time required for the flattening process of the magnetic particles Can be shortened.

  In addition, when three or more stirring pins are provided in one step, the number of times that the magnetic particles and the dispersion medium come into contact with the stirring pins increases. When the number of times that the magnetic particles and the dispersion medium come into contact with the stirring pin increases, the entire magnetic particles and the dispersion medium tend to move at the same speed as the rotation of the stirring pin. When the magnetic particles and the dispersion medium are moving at the same speed, it is difficult to apply mechanical energy to the magnetic particles by the dispersion medium, and the time required for the flattening process of the magnetic particles becomes long.

  On the other hand, according to this embodiment, two stirring pin groups 30 are provided in one stage. Therefore, the number of times that the magnetic particles and the dispersion medium come into contact with the stirring pin group 30 does not increase excessively, and the entire magnetic particles and the dispersion medium can be prevented from having the same speed as the rotation of the stirring pins. As a result, according to the present embodiment, it is possible to suppress an increase in the time required for the flattening process of the magnetic particles.

  Further, according to the present embodiment, the stage provided with the stirring pins 31a to 31d and the stirring pins 32a to 32d and the stage provided with the stirring pins 33a to 33c and the stirring pins 34a to 34c are provided alternately. ing. That is, the protruding direction of the stirring pins between adjacent steps is vertical. Therefore, according to this embodiment, it can suppress more that a magnetic particle and a dispersion medium become the same speed as rotation of the stirring pin group 30. FIG.

  Further, according to the present embodiment, the total volume of the stirring pin group 30 is 0.081 V or more and less than 1.0 V with respect to the volume V of the stirring unit 21. Therefore, according to the present embodiment, the number of magnetic particles contacting the stirring pin group 30 per unit time can be improved, and as a result, the time required for the flattening process can be shortened.

Further, according to this embodiment, the total projected area of the stirring pin group 30, 0.85D ² or more, a 1.2D ^2. Therefore, according to the present embodiment, the number of magnetic particles contacting the stirring pin group 30 per unit time can be improved, and as a result, the time required for the flattening process can be further shortened.

  In the present embodiment, the following configuration may be employed.

  In the embodiment described above, the number of stages is 12 or more, but is not limited thereto. In the present embodiment, for example, the number of stages may be 11 or less.

In the present embodiment, the total volume of the stirring pin group 30 may be smaller than 0.081V.
In the present embodiment, the total projected area of the stirring pin group 30 may be smaller than 0.85D ^2, may be greater than 1.2D ^2.

  In the embodiment described above, the shape and size of the stirring pin group 30 are all the same. However, the shape and size of the stirring pin group 30 are not limited to this, and the shape and size of some of the stirring pin groups 30 are different. Alternatively, they may have different shapes and sizes.

  In the embodiment described above, the shape of the stirring pin group 30 is a cylindrical shape, but is not limited thereto. The shape of the stirring pin group 30 may be a quadrangular prism shape or a polygonal prism shape. In the present embodiment, the shape of the stirring pin group 30 may be a plate shape.

  In the embodiment described above, as shown in FIG. 2, the tip on the protruding side of the stirring pin group 30 is a plane perpendicular to the direction in which the stirring pin group 30 protrudes. However, the present invention is not limited to this. . In the present embodiment, the protruding tip of the stirring pin group 30 may be a spherical surface, for example.

Example 1 of the bead mill 10 of the present embodiment described above was manufactured and compared with Comparative Example 1 to Comparative Example 4.
The parameters of the stirring pins used in Example 1 and Comparative Examples 1 to 4 are shown in Table 1. In Table 1, D is the inner diameter of the stirring part of the mill body, and V is the volume of the stirring part of the mill body.

Example 1 has two stirrer pins, the stirrer pin length W1 is 0.269D, the stirrer pin thickness W2 is 0.172D, the stirrer pin volume per step is 0.0071V, and the total stirrer pin 0.085V volume, total stirring pin projected area was 1.1D ^2. The number of stages in which the stirring pins are provided was 12 stages.

In Comparative Example 1, the number of stirring pins in one stage is two, the stirring pin length W1 is 0.194D, the stirring pin thickness W2 is 0.150D, the stirring pin volume per stage is 0.0037V, and the total stirring pins 0.037V volume, total stirring pin projected area was 0.58D ^2. The number of stages on which the stirring pins are provided was 10.
Comparative Example 2 has two stirrer pins, the stirrer pin length W1 is 0.194D, the stirrer pin thickness W2 is 0.188D, the stirrer pin volume per step is 0.0057V, and the total stirrer pin 0.063V volume, total stirring pin projected area was 0.80D ^2. The number of stages in which the stirring pins are provided was 11 stages.
Comparative Example 3 has four stirrer pins, the stirrer pin length W1 is 0.194D, the stirrer pin thickness W2 is 0.150D, the stirrer pin volume per step is 0.0073V, and the total stirrer pin 0.080V volume, total stirring pin projected area was 1.3D ^2. The number of stages in which the stirring pins are provided was 11 stages.
Comparative Example 4 has two stirrer pins, the stirrer pin length W1 is 0.241D, the stirrer pin thickness W2 is 0.138D, the stirrer pin volume per step is 0.0041V, and the total stirrer pins 0.045V volume, total stirring pin projected area was 0.73D ^2. The number of stages in which the stirring pins are provided was 11 stages.

The one with two stirring pins has the same stirring pin arrangement as the bead mill 10 of the embodiment described above. When the number of the stirrer pins is four, the stirrer pin arrangement in which the stirrer pin 31a, the stirrer pin 32a, the stirrer pin 33a, and the stirrer pin 34a in the bead mill 10 of the embodiment described above are provided in a single step. It was.
The shape of the stirring pin was a cylindrical shape.

Using the bead mills of Example 1 and Comparative Examples 1 to 4, the magnetic particles were flattened.
The magnetic particles were 78 permalloy having an average primary particle size of 160 nm. The dispersion medium was xylene. The dispersion medium was a zirconia ball having a diameter of 0.2 mm. A flattening treatment was performed, and the magnetic permeability of the magnetic particles at each treatment time was measured.
The magnetic permeability was measured at 1 GHz at room temperature in the atmosphere using a magnetic permeability measuring device (manufactured by Agilent Technologies, Vector Network Analyzer 8791ES type). The results are shown in Table 2. In addition, the magnetic permeability shown in Table 2 has shown the relative magnetic permeability.

  From Table 2, it was found that in Example 1, the permeability was 10 or more at the time of 240 minutes, whereas in Comparative Examples 2 and 3, it was less than 10. . In Comparative Example 1, it was found that the magnetic permeability was less than 10 even when the processing time was 300 minutes. In Comparative Example 4, although the magnetic permeability is 10 or more at the time when the processing time is 480 minutes, it takes twice as long as the processing time when the magnetic permeability is 12.4 in Example 1, It was found that the permeability was lower than that in Example 1.

FIG. 3 is a scanning electron microscope (S-4000, manufactured by Hitachi High-Tech Co., Ltd.) photograph showing magnetic particles at a processing time of 240 minutes in Example 1.
From FIG. 3, it was confirmed that the magnetic particles were flattened.

  From the above, according to this example, it was confirmed that the time required for the flattening treatment of the magnetic particles can be shortened and the magnetic permeability can be improved.

  DESCRIPTION OF SYMBOLS 10 ... Bead mill, 20 ... Mill main body, 21 ... Agitation part, 30 ... Agitation pin group (projection part group), 31a, 31b, 31c, 31d, 33a, 33b, 33c ... Agitation pin (1st projection part), 32a, 32b, 32c, 32d, 34a, 34b, 34c ... stirring pin (second protruding portion), 40 ... shaft (rotating shaft portion), D ... inner diameter, V ... volume, W1 ... stirring pin length (length in protruding direction) ), W2... Stirring pin thickness (axial length of rotating shaft)

Claims (5)

A bead mill used for flattening magnetic particles,
A cylindrical mill main body in which magnetic particles are accommodated;
A rotation shaft provided in the mill body, coaxial with the cylindrical shaft of the mill body;
A projecting portion group which is provided to project from the rotating shaft portion in the radial direction of the rotating shaft portion, and which includes a plurality of projecting portions;
With
The protrusion group is
A first projecting portion projecting from the rotating shaft portion to one side in a radial direction of the rotating shaft portion;
A second projecting portion projecting to the opposite side of the first projecting portion with respect to the rotating shaft portion;
Including
A plurality of steps provided with the first projecting portion and the second projecting portion are provided along the axial direction of the rotating shaft portion,
The adjacent steps are arranged with a 90 ° offset around the axis of the rotating shaft part,
When the inner diameter of the stirring portion for stirring the magnetic particles in the mill body is D, the axial length of the rotating shaft portion in the projecting portion group is 0.165D or more and 0.185D or less. Yes,
The length of the protruding portion group in the protruding direction is 0.25D or more and 0.27D or less,
When the volume of the stirring portion is V, the total volume of one first protrusion and one second protrusion is 0.0062V or more and 0.0072V or less. Features a bead mill.   2. The bead mill according to claim 1, wherein a total volume of the protruding portion group is 0.081 V or more and less than 1.0 V. 3. The total projected area when the projecting portion group is projected in a direction perpendicular to the direction in which the projecting portion group projects and perpendicular to the axial direction of the rotating shaft portion is 0.85D ² or more and 1.2D. The bead mill according to claim 1 or 2, which is ² or less. A bead mill used for particle flattening,
A cylindrical mill body in which particles are accommodated;
A rotation shaft provided in the mill body, coaxial with the cylindrical shaft of the mill body;
A projecting portion group which is provided to project from the rotating shaft portion in the radial direction of the rotating shaft portion, and which includes a plurality of projecting portions;
With
The protrusion group is
A first projecting portion projecting from the rotating shaft portion to one side in a radial direction of the rotating shaft portion;
A second projecting portion projecting to the opposite side of the first projecting portion with respect to the rotating shaft portion;
Including
A plurality of steps provided with the first projecting portion and the second projecting portion are provided along the axial direction of the rotating shaft portion,
The adjacent steps are arranged with a 90 ° offset around the axis of the rotating shaft part,
When the inner diameter of the stirring portion for stirring the particles in the mill body is D, the axial length of the rotating shaft portion in the projecting portion group is 0.165D or more and 0.185D or less. ,
The length of the protruding portion group in the protruding direction is 0.25D or more and 0.27D or less,
When the volume of the stirring portion is V, the total volume of one first protrusion and one second protrusion is 0.0062V or more and 0.0072V or less. Features a bead mill.   The bead mill according to claim 4, wherein the particles are metal particles.