JP5598824B2 - Dispersion or grinding apparatus and dispersion or grinding method - Google Patents

Description

  The present invention relates to an apparatus and a dispersion or pulverization method that can be used at an actual production level so that nanometer-sized solid particles mixed in a liquid can be dispersed or pulverized.

  An apparatus for finely pulverizing solid particles in a processing material (mill base) using a pulverizing medium (beads) and dispersing or pulverizing the particles in a liquid is known. Dispersers, media mills, etc.) are widely used. In the apparatus used in actual production, the processing material is stirred together with the beads, and solid particles are pulverized by a shearing action and dispersed in a liquid to obtain particles micronized to a submicron level. However, it is difficult to obtain extremely fine nanoparticles having a particle size of 100 nanometers or less as required in recent years by a bead mill using beads on the order of mm. This is because a uniform shear force cannot be applied to the nanoparticles. Therefore, recently, a bead mill using beads of several tens of μm has been developed, and a more uniform shearing force can be applied to the nanoparticles. It has become possible. On the other hand, there is also known an ultrasonic disperser used for dispersion of liquid / liquid systems such as the production of emulsions, and for pulverization and dispersion of solid particles in solid / liquid systems. According to this method, since collisions between uniform particles can be added, depending on the particle concentration, it is possible to pulverize and disperse to near the primary particle which is nanometer size at the laboratory level. This ultrasonic disperser can be pulverized and dispersed by generating collision of particles with a shock wave generated by the collapse of cavitation. A combination of a bead mill using the above-mentioned mm order beads that can be used at the production level and ultrasonic irradiation, specifically connecting a media mill and a container with a tube to circulate a mixture of dispersed solid pigment and liquid medium There is also known a pigment dispersion apparatus in which the inside of the container is decompressed and an ultrasonic oscillation mechanism is provided in part (see, for example, Patent Document 1). However, the ultrasonic oscillation mechanism used in such an apparatus and method irradiates ultrasonic waves for the purpose of preventing sedimentation of the dispersion liquid dispersed by the media mill, so that pulverized and dispersed nanoparticles are reliably obtained. Therefore, an ultrasonic device is not used.

JP 2000-351916 (Claim 7, [0029], [0049] drawings)

As described above, in the bead mill using very fine beads of the order of several tens of μm, pulverization and dispersion to the nanometer-sized primary particle size became possible at the laboratory level. There is a problem that it is difficult to separate particles and beads of the order of several tens of μm, and they cannot be used at the actual production level. In addition, when beads of the order of mm, for example, beads having a level of 0.5 mm (500 μm) are used, it is possible to separate the beads, but it has been impossible to pulverize and disperse to near the primary particle size. On the other hand, a method that enables pulverization and dispersion at the primary particle level by a method of irradiating ultrasonic waves is also known, but the conditions for sufficiently generating collision between particles are extremely narrow, and an area where energy can be applied Is very narrow and can handle only small amounts. Therefore, it is rarely used for actual production in terms of cost performance. Furthermore, as shown in Patent Document 1, a method in which ultrasonic irradiation and a bead mill are combined has also been proposed. However, ultrasonic irradiation is performed in a large-capacity tank at an actual production level, and a grinding medium (ball or bead is placed in the tank. ) Does not enter, the particles do not sufficiently collide with each other due to ultrasonic irradiation and do not have a function of pulverizing solid particles. In order to pulverize and disperse the solid particles in the liquid by the effect of ultrasonic irradiation, there is no method other than making the tank extremely small, and this is inefficient and cannot be used in actual production.
Although various methods have been tried in this way, there is still a problem that it has not reached the point where it can be used at the actual production level using beads on the order of mm in applications aimed at crushing and dispersing nanoparticles. is there.

According to the present invention, it has a vessel having a supply port and a discharge port for a processing material in which solid particles are mixed in a liquid, a rotor rotated by a drive shaft in the vessel, and a medium separator for a bead mill. the process material supplied into the vessel to 攪拌the grinding media together with for bead milled, the solid particles fed into the mill from the milling media for the bead mill at medium separation device for the bead mill A bead mill to be separated, a tank having an outlet leading to a supply port of the bead mill and an inlet leading to a discharge port of the bead mill, an agitating blade rotating in the tank, and an ultrasonic wave generating ultrasonic wave in the tank a device having a media separating device for mixers, with the stirring blade, while the process material supplied into the tank is stirred with grinding media mixer, ultrasonic And a mixer for separating the solid particles supplied to the mixer from the pulverizing medium for the mixer by the medium separator for the mixer, and pulverizing for the bead mill and the mixer medium is a particle size of 15μ m~1.0mm, above problems by frequency of ultrasonic waves to be irradiated 15KHz～30KHz, dispersing or milling apparatus is characterized in that the amplitude is 5μm~50μm is provided Is resolved. According to the present invention, there is also provided a dispersion or pulverization method for dispersing or pulverizing solid particles in a liquid using the above apparatus.

  The present invention is configured as described above, and a shearing force is applied to the solid particles in the processing material by the movement of the grinding medium like a bead mill using beads on the order of mm, or between particles like an ultrasonic disperser. Compared to the case of pulverizing and dispersing by collision, the processing material in which solid particles are mixed in the liquid is stirred with the pulverizing medium, and ultrasonic waves are irradiated during the stirring to finely pulverize and disperse the solid particles in the liquid. As a result, collision between nanoparticles aggregated by shock waves generated by ultrasonic irradiation occurs, and the nanoparticles also collide with the grinding medium. This is particularly effective when the particle concentration is lower. At the same time, a shock wave generated by ultrasonic irradiation is transmitted to the grinding medium to promote the movement and the grinding medium is vigorously stirred in the vessel, so that the grinding medium moves sufficiently, and the grinding media collide with each other. A strong shearing force is generated, and the shearing force generated by the collision, the collision between the nanoparticles, and the collision with the pulverization medium can be combined, so that the solid particles can be extremely finely pulverized to obtain nanoparticles. . This crushing and dispersing apparatus does not cause any problems when used at the actual production level.

  Further, since the average particle size of the nanoparticles obtained as described above is about 100 nm or less, the grinding media can be separated by setting the particle size of the grinding media to 15 μm or more. By setting the diameter to 1.0 mm or less, the pulverization medium can be sufficiently moved by a shock wave formed by ultrasonic waves. When an ultrasonic oscillator is provided in a vessel in a bead mill, when used at the production level, the nanoparticles and beads can be classified more reliably, and the pulverizing medium can be sufficiently used by shock waves formed by ultrasonic waves. A range of 0.5 mm to 1.0 mm that can be moved is preferred. When an ultrasonic oscillator is provided in a tank that shares a supply tank and a recovery tank in a bead mill, there is no problem in actual production even if the grinding medium is in a range of 15 μm to 1.0 mm. Furthermore, if the frequency of the ultrasonic wave is 15 KHz to 30 KHz and the amplitude is 5 μm to 50 μm, large cavitation can surely be generated, and the shock wave generated when it collapses becomes strong, and the aggregated nanoparticles and grinding media are sufficiently To disperse and grind. More preferably, it is desirable that the ultrasonic vibration frequency is 15 KHz to 20 KHz and the amplitude is 20 μm to 50 μm.

  The present invention can be applied to various bead mills (wet medium dispersers, media mills, bead dispersers, etc.). A to D systems will be described below as specific examples and reference examples. FIG. 1 shows an example of a reference example A system. A bead mill 1 has a vessel 2 and a rotor 4 rotated by a drive shaft 3 in the vessel 2, and the vessel 2 is supplied from a bead supply port 5. A predetermined amount of the pulverized medium (beads) is stored, and a processing material (mill base, slurry) which is a mixture of solid particles and liquid is supplied into the vessel 2 from the mill base supply port 6.

  The rotor 4 is formed in a cylindrical shape and the surface is formed in a substantially smooth surface. However, as shown in Japanese Patent Publication No. 4-70050, for example, a suitably shaped protrusion is provided so as to give motion to the grinding medium. A guide member may be provided so that the processing material can be moved forward or backward in a vessel and allowed to flow substantially in the form of plug flow (plug flow). The rotor is provided with a rotor opening 7 at a suitable position so that the grinding medium circulates from the inner surface to the outer surface.

  A stator 8 is formed on the inner surface of the rotor 4, and a stator opening 10 having a medium separating device such as a screen 9 is formed at an appropriate position of the stator 8 so as to separate the pulverized medium and allow only the processing material to flow out. The stator opening 10 communicates with the mill base discharge port 11.

The bead mill shown in FIG. 1 is provided with a pocket in a part of the vessel, and a horn type ultrasonic oscillator is mounted inside the pocket. More specifically, as shown in FIG. 1B, a concave portion 12 is formed on the inner wall of the vessel 2, and an ultrasonic horn 13 of an ultrasonic generator is provided in the concave portion 12. The recess 12 may be provided in a portion that is not easily affected by the grinding medium, or in a location where an appropriate baffle or the like is configured to be less affected. In the specific example shown in the figure, it is provided at one place, but it can be provided at a plurality of places. Since beads and slurry are supplied to the pockets, collision of nanoparticles with each other and collision between nanoparticles and beads occur when irradiated with ultrasonic waves, and the shearing force and phase due to the beads being subjected to high-speed rotation in the rotor rotating part. Overlapping and agglomerated nanoparticles can be ground and dispersed to near primary particles.
The size of the beads is in the range of 15 μm to 1.0 mm. Preferably it is the range of 0.5 mm to 1.0 mm. By setting it as this range, it becomes possible to classify nanoparticles and beads reliably using a medium separation device such as a screen (gap).

  FIG. 2 shows an example of the reference example B system. The bead mill 14 has a rotor 17 that is rotated by a drive shaft 16 in a vessel 15, and the peripheral surface of the rotor 17 is disclosed in, for example, Japanese Patent Publication No. 4-70050. As described, a guide member for allowing the slurry to flow substantially in a plug flow is formed, and a grinding medium (bead) is accommodated therein. The slurry entering from the supply port 18 is dispersed while flowing in a substantially plug-like flow, and flows out from the discharge port 20 through the medium separator 19. In this apparatus, the slurry is flowing from the direction of the tip of the vessel toward the rotor as opposed to the above-described A method. A space 21 is formed in a vessel opposite to the tip of the rotor, and a throwing-type ultrasonic oscillator 22 is attached thereto. Since beads and slurry are supplied to this space, if ultrasonic irradiation is performed, collisions between nanoparticles and collisions between nanoparticles and beads occur, and the shearing force caused by the beads used for high-speed rotation in the rotor rotating part By overlapping, the agglomerated nanoparticles can be crushed and dispersed close to the primary particles. The size of the beads is in the range of 15 μm to 1.0 mm. Preferably it is the range of 0.5 mm to 1.0 mm. By setting it as this range, it becomes possible to reliably separate nanoparticles and beads using a medium separation device such as a screen (gap).

  FIG. 3 shows an example of the reference example C method. Since the bead mill 23 is basically the same as the bead mill 1 shown in FIG. 1, the common portions are denoted by the same reference numerals and the description thereof is omitted. A concave portion for accommodating the sonic horn is not formed, and the horn type ultrasonic oscillator 24 is mounted in a reservoir space 25 before the slurry passes through the screen (gap) and exits to the discharge port. First, in the vessel before passing through the screen, there is pulverization of particles from the shearing force by the beads that are subjected to high-speed rotation in the rotor rotating portion. Since the horn-type ultrasonic transmitter 24 is mounted inside, collisions between the nanoparticles occur here, and as a result, the aggregated nanoparticles can be pulverized and dispersed close to the primary particles by receiving both actions almost simultaneously. It becomes. The size of the beads is in the range of 15 μm to 1.0 mm. Preferably it is the range of 0.5 mm to 1.0 mm. By setting it as this range, it becomes possible to reliably separate nanoparticles and beads using a medium separation device such as a screen (gap).

  FIG. 4 is an apparatus showing an example of the D system of the embodiment, which has an inlet 26 and an outlet 27 for slurry (treatment material), and has a certain kind of slurry supply tank and recovery tank for the bead mill 28. A tank mixer 29 is provided, beads (mixing medium for mixer) are charged into the mixer, and an ultrasonic oscillator 30 is mounted. At the same time, a stirring blade 31 for stirring the beads is attached to the mixer. The size of the mixer beads is in the range of 15 μm to 1.0 mm. As a media separator 32 for a mixer that separates nanoparticles and beads in a slurry, a screen (gap) is provided in the case of 0.5 mm to 1.0 mm, and a filter is provided in the case of 15 μm to 0.5 mm. It is desirable to pass the As for the size of the above beads for the mixer, if the amplitude of the ultrasonic wave is large, the beads can be moved even if they are large. Can be caused to collide with each other, and the effect of overlapping can be pulverized and dispersed to near the primary particles of the nanoparticles. On the other hand, when the amplitude of the ultrasonic wave is small, it is necessary to select a smaller bead because a large bead cannot be moved. The optimum amount of beads is determined by the particle concentration of the slurry to be processed. In the case of a dilute slurry, a large amount of input is required, and in the case of a thick slurry, it is necessary to decrease the amount of input. As shown in FIG. 4, the bead mill 28 is configured in the same manner as the bead mill shown in FIG. 3 except that it does not have an ultrasonic oscillator. That is, a vessel 2 having a processing material supply port 6 and a discharge port 11, a rotor 4 rotated by a drive shaft 3 in the vessel, and a bead mill for separating a bead mill grinding medium housed in the vessel from the processing material. A medium separating device 9 is provided. The solid particles in the processing material stirred together with the pulverizing medium in the vessel are made into fine particles, separated from the pulverizing medium by the above-described bead mill medium separator, and discharged from the discharge port 11. The processing material processed by the bead mill is supplied to the mixer from the inlet 26 that leads to the discharge port 11, and the processing material that is processed by the mixer and flows out from the outlet 27 is supplied from the supply port 6 that leads to the outlet 27. The above processing is performed alternately while being supplied to the bead mill and circulating.

When an ultrasonic oscillator is installed in a vessel, the grinding media is relatively fine particles that are moved by shock waves due to cavitation collapse caused by ultrasonic waves, that is, relatively smaller than the beads used in conventional general media dispersers. Those having a small diameter are preferably used, and the size is such that they can be separated by a medium separation device such as the screen (gap). Specifically, in the method using a filter and the method using centrifugation, according to the experimental results, in order to be able to separate nanoparticles having an average particle size of 100 nm or less, the particle size of the grinding medium is about 15 μm. The above is necessary, and separation was difficult with a smaller particle size. More preferably, the bead diameter is more preferably 0.5 mm or more by a method using a screen (gap) that can be classified reliably. In addition, if the bead diameter exceeds 1.0 mm, the grinding medium cannot be sufficiently moved by the shock wave formed by ultrasonic waves, and as a result, the aggregated nanoparticles can be effectively collided with the grinding medium. Can not.
In order to move larger grinding media, it is necessary to generate and collapse larger cavitation. Further, when the particle concentration is high, it is desirable that the amount of the grinding medium is small, and when the particle concentration is low, the amount of the grinding medium is large.
As the material of the grinding medium, an optimum material is selected depending on the application in which the dispersing or grinding apparatus provided in the present invention is used, and any material such as engineering plastic, glass, ceramics, and steel may be used. Zirconia material is preferred for applications where wear and defects are likely to occur.
When the nanoparticles are treated using the dispersion or pulverization apparatus provided in the present invention, the solvent may be water or an organic solvent such as various alcohols, cyclohexane, methyl ethyl ketone, methyl acetate, toluene, hexane and the like. Absent.

  When an ultrasonic oscillator is installed in a vessel, the ultrasonic generator has a frequency that allows the nanoparticles to collide with each other by the cavitation shock wave generated by ultrasonic irradiation and move the grinding medium. Amplitude is required. According to the results of experiments, when the frequency is about 15 KHz to 30 KHz and the amplitude is about 5 μm to 50 μm, the cavitation is large, the shock wave generated at the time of collapse can be strengthened, and sufficient motion is achieved for the aggregated nanoparticles and grinding media Could be given. More preferably, it is desirable that the ultrasonic vibration frequency is 15 KHz to 20 KHz and the amplitude is 20 μm to 50 μm.

  The difference between the bead mill using ultrasonic waves as described above and the case of dispersing and pulverizing using a simple ultrasonic disperser or a conventional bead mill will be briefly described. As shown in FIG. The collision generated by the shock wave is only the collision between the aggregated nanoparticles 33. Further, in the case of only the bead mill, as shown in FIG. 6, only the shearing force generated between the grinding media 34, and the nanoparticles 33 do not actively collide with the grinding media 34. In the bead mill using ultrasonic waves, as shown in FIG. 7, since an ultrasonic shock wave is added to the grinding medium, the agglomerated nanoparticles 33 are subjected to shear forces and collisions between the nanoparticles due to ultrasonic irradiation. Since the particles collide with the pulverizing medium, the particles are effectively finely divided, and even the nanoparticles can be sufficiently dispersed and pulverized.

  Examples and reference examples according to the present invention will be described in detail below. However, the present invention is not necessarily limited by these examples.

(Reference Example 1)
The apparatus shown in FIG. 1 in which a pocket was provided in a part of the A-type vessel and a horn type ultrasonic oscillator was mounted inside the pocket was used. More specifically, a concave portion 12 is formed on the inner wall of the vessel 2, and an ultrasonic horn 13 of an ultrasonic generator is provided in the concave portion 12. The ultrasonic wave had an amplitude of 50 μm and a vibration frequency of 20 KHz. The bead mill was processed at a peripheral speed of 4 m / S and a slurry feed speed of 10 mL / S. 10% by volume of Degussa P25 powder having a primary particle size of 35 nm composed of titanium oxide nanoparticles and water containing 0.5 mg / m ² of polyacrylic acid ammonium salt having a molecular weight of 8000 as a polymer dispersant per particle surface area of P25 powder The slurry was pretreated for 30 minutes using a 500 rpm rotating blade. Using this slurry 3 liter, a dispersion experiment was conducted up to 5 hours using the above apparatus. Using an ultrasonic attenuation type particle size analyzer, the particle size in the slurry was measured with the particle concentration kept at 10% by volume. The particle sizes measured every hour up to 5 hours are shown in Table 1.

(Reference Example 2)
The apparatus shown in FIG. Specifically, the slurry flows from the direction of the tip of the vessel toward the rotor as opposed to the A method, and the reference example 1 is the same as that of the reference example 1 except that a throw type ultrasonic oscillator is installed in a space created on the opposite side of the tip of the rotor. Table 1 shows the particle sizes measured in the same manner as the dispersion experiment up to 5 hours every hour.

(Reference Example 3)
The apparatus shown in FIG. Specifically, a horn type ultrasonic oscillator is mounted in a pool space before the slurry passes through the screen (gap) and exits to the discharge port, and a dispersion experiment is performed in the same manner as in Reference Example 1 except for that. The particle size measured up to 5 hours every hour is shown in Table 1.

Example 1
The apparatus shown in FIG. Specifically, a bead mill using 0.5 mm zirconia beads and a mixer serving as a slurry supply tank and a recovery tank are provided in the circulation system, and 50 μm zirconia balls are introduced into the mixer for 0.1 liter. . In order to classify the balls (beads) and the nanoparticles in the slurry, a 25 μm mesh filter was installed. Further, an ultrasonic oscillator having a vibration frequency of 20 KHz and an amplitude of 50 μm was installed in the tank. The bead mill was processed at a peripheral speed of 4 m / S and a slurry feed speed of 10 mL / S. 10% by volume of Degussa P25 powder having a primary particle size of 35 nm composed of titanium oxide nanoparticles and water containing 0.5 mg / m ² of polyacrylic acid ammonium salt having a molecular weight of 8000 as a polymer dispersant per particle surface area of P25 powder The slurry was pretreated for 30 minutes using a 500 rpm rotating blade. Using this slurry 3 liter, a dispersion experiment was conducted up to 5 hours using the above apparatus. Using an ultrasonic attenuation type particle size analyzer, the particle size in the slurry was measured with the particle concentration kept at 10% by volume. The particle sizes measured every hour up to 5 hours are shown in Table 1.

(Example 2)
A dispersion experiment was conducted in the same manner as in Example 1 except that the bead diameter put in a mixer having both a supply tank and a recovery tank was 0.5 mm, and the separation of beads and nanoparticles was 0.2 mm (screen) (gap). The particle size measured up to 5 hours every hour is shown in Table 1.

(Example 3)
Dispersion experiment was conducted in the same manner as in Example 1 except that ultrasonic waves having a frequency of 20 KHz and an amplitude of 20 μm were applied to the slurry in a mixer having both a supply tank and a recovery tank. Are shown in Table 1.

Example 4
Ultrasonic waves with a frequency of 20 KHz and an amplitude of 20 μm are irradiated to the slurry in a tank mixer that has both a supply tank and a recovery tank, the bead diameter to be put into the mixer is 0.5 mm, and the beads and nanoparticles are classified by a screen (gap) Dispersion experiments were carried out in the same manner as in Example 1 except that the thickness was 0.2 mm.

(Comparative Example 1)
Dispersion experiments were conducted in the same manner as in Example 1 with the exception of eliminating beads and ultrasonic irradiation in a mixer having both a supply tank and a recovery tank. Table 1 shows the particle sizes measured up to 5 hours every hour. .

(Comparative Example 2)
Dispersion experiments were carried out in the same manner as in Example 1 except that the beads to be put into a mixer having both a supply tank and a recovery tank were removed, and the particle sizes measured up to 5 hours every hour are shown in Table 1.

(Comparative Example 3)
A dispersion experiment was conducted in the same manner as in Example 1 except that the mixer slurry having both a supply tank and a recovery tank was irradiated with ultrasonic waves having a frequency of 20 KHz and an amplitude of 20 μm, and the beads to be put into the mixer were eliminated. The particle sizes measured up to 5 hours are shown in Table 1.

(Comparative Example 4)
A dispersion experiment was conducted in the same manner as in Example 1 except that the ultrasonic waves having a vibration frequency of 40 KHz and an amplitude of 5 μm were applied to the slurry of the mixer having both a supply tank and a recovery tank, and the ball beads to be put into the mixer were eliminated. The particle sizes measured up to 5 hours are shown in Table 1.

It is an A type bead mill showing one reference example of the present invention, in which (A) is a cross-sectional view, and (B) is a cross-sectional view taken along line BB of (A). Sectional drawing of the B-type bead mill which shows one reference example of this invention. Sectional drawing of the C type bead mill which shows one reference example of this invention. Sectional drawing of the apparatus of D system which shows one Example of this invention. Explanatory drawing which shows the effect | action of the conventional ultrasonic disperser. Explanatory drawing which shows the effect | action of the conventional bead mill. Explanatory drawing which shows the effect | action of the bead mill of this invention.

1, 14, 23, 28 Bead mill 2, 15 Vessel 3, 16 Drive shaft 4, 17 Rotor 5 Bead supply port 6, 18 mil base supply port 7 Rotor opening 8 Stator 9 Screen 10 Stator opening 11, 20 mil base discharge port 12 Recess 13 22, 24, 30, ultrasonic transmitter 29 tank mixer 33 nanoparticles 34 grinding media (beads)

Claims (2)

A vessel having a supply port and a discharge port for a processing material in which solid particles are mixed in a liquid, a rotor rotated by a drive shaft in the vessel, and a medium separation device for a bead mill, are supplied into the vessel. A bead mill that stirs and finely pulverizes the treated material together with a grinding medium for the bead mill, and separates the solid particles supplied to the bead mill from the grinding medium for the bead mill by the bead mill medium separation device;
For a tank having an outlet that leads to the supply port of the beads mill and an inlet that leads to the outlet of the beads mill, a stirring blade that rotates in the tank, an ultrasonic generator that generates ultrasonic waves in the tank, and a mixer While stirring the processing material supplied into the tank together with the grinding medium for the mixer by the stirring blade, the solid particles are finely ground by irradiating ultrasonic waves. A mixer that separates solid particles supplied to the mixer from the pulverization medium for the mixer by a medium separator ,
The grinding media for the bead mill and the mixer have a particle size of 15 μm to 1.0 mm,
A dispersing or pulverizing apparatus characterized in that an ultrasonic wave to be irradiated has a frequency of 15 KHz to 30 KHz and an amplitude of 5 μm to 50 μm . A dispersion or pulverization method for dispersing or pulverizing solid particles in a liquid using the dispersion or pulverization apparatus according to claim 1 .

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