JP7429039B2 - wet bead mill - Google Patents

Description

The present invention crushes and disperses fine particles in a suspension of solid fine particles in a solvent (hereinafter referred to as slurry) by stirring hard particles (hereinafter referred to as beads) as stirring media in a container. Regarding a wet bead mill for processing.

There are various types of devices for crushing and dispersing particles in slurry, but the continuous type uses a rotating member (stirrer) that rotates at high speed in a closed cylindrical container, allowing the cylindrical container and the stirrer to separate. There is a device (bead mill) that generates shear force between the slurry and crushes and disperses particles in the slurry using stirring media (beads) suspended in the slurry. For example, in the device (bead mill 1) of the invention disclosed in the patent document of Patent Document 1, there is a stirrer at the bottom of a cylindrical container, and by rotating this, it is possible to perform the pulverization process of particles and the secondary particles where primary particles have aggregated. Perform dispersion treatment of the next particle. When grinding and dispersing are to be carried out efficiently, beads with a diameter of about 0.03 to 3 mm are mixed into the slurry. In the bead mill 1, beads are separated from the slurry that has been pulverized and dispersed using a bead separator at the top.

Furthermore, the wet bead mill (bead mill 2) described in Patent Document 2 is an apparatus that uses a centrifugal separator to perform both bead separation and stirring of a mixture of slurry and beads. By improving the bead separation ability, it is possible to operate even at low speed rotation, and by adjusting the stirring force and reducing excessive crushing force, it has the function of improving the particle shape during dispersion processing. Further, the stirrer is the same as that of the bead mill 1, but a nozzle-shaped movable stopper is installed at the slurry outlet, and a gap narrower than the diameter of the beads is formed between the outlet and the movable stopper. The beads are separated by passing the treated slurry through this gap. Some bead mills with similar functionality use screens for bead separation.

In a bead mill with a bead separation mechanism having a slit or screen narrower than the diameter of the beads at the bead outlet, beads of 0.3 mm to several mm are used to process the slurry due to restrictions on the gap for separating the beads. Since there is a large pressure loss when the slurry passes through this gap, a relatively high pressure of 0.1 to 0.4 MPa is applied in order to flow the slurry into a bead mill equipped with this type of bead separation device. Furthermore, even when using a separator that uses centrifugal force to separate beads, a pressure of 0.1 A relatively high pressure of ~0.4 MPa is applied.

As described above, a sealing device is essential for a bead mill, and there are also problems associated with wear and deposits on the sealing device.As a technique to solve this problem, a wet bead mill (bead mill) without a mechanical seal is described in Patent Document 3. 3) was developed. A hole is made in the top of the mill to create a gap between the stirrer of the bead mill and the rotating shaft that rotates the centrifugal bead separator, and in this gap, the slurry from which beads have been separated by the centrifugal bead separator rises. This technology eliminates the use of mechanical seals by discharging the water outside the mill. However, since beads cannot be separated in the upper space between the centrifugal bead separator and the upper part of the mill, there is a problem that slurry containing beads flows from the upper space into the above-mentioned gap. An impeller member is installed to create a flow of slurry from the center to the periphery.

Note that pulverization processing here refers to dividing a single particle into multiple small particles, and dispersion processing refers to separating secondary particles to a state in which primary particles are individually dispersed. say what you do Note that a primary particle refers to a single crystalline or amorphous particle of a substance, and a secondary particle is generally a particle formed by the surfaces of several to several thousand primary particles coming into contact with each other to form a pseudo particle. Say what you have. The beads used in the pulverization and dispersion processing are particles made of ceramic such as alumina or zirconia, metal such as stainless steel, or plastic, and are generally preferably spherical.

Japanese Patent Application Publication No. 2002-143707 JP 2017-131807 Publication JP2017-043685A

Wet bead mills are capable of continuous processing and have excellent pulverization and dispersion capabilities, such as being able to pulverize and disperse particles from micrometer to nanometer sizes, but they have the following issues. A wet bead mill stirs beads in a cylindrical container to pulverize or disperse particles in a slurry, and separates the beads in the cylindrical container. In a wet bead mill that has a bead separation mechanism that separates beads by passing the slurry through a narrow gap such as a slit or screen, the fluid resistance when stirring the slurry and the fluid resistance when passing through the gap are Therefore, it was necessary to pressurize the slurry and force it into a cylindrical container. Since the rotating shaft for rotating the stirrer in the cylindrical container has a rotating sliding portion in contact with the slurry, a sealing mechanism for the rotating portion is required to counteract this internal pressure. In order to seal the rotating part of such a relatively high pressure part, a seal structure using a mechanical seal device, a rotary joint, etc. has generally been used.

Seal devices such as mechanical seals have contact parts between stationary parts and rotating parts, and the seal liquid is stored under pressure outside the seal device to prevent the high-pressure slurry inside the container from leaking out from the seal part. It was a structure. Since the seal contact parts gradually wear out, there is a problem in that the sealing performance deteriorates over time. As a result, there was a problem that the sealing liquid leaked into the slurry and contaminated the slurry. There was also the problem that abrasion powder from seal contact parts (metals, ceramics, etc.) was mixed into the slurry. Furthermore, when the sealing device becomes severely worn, it is necessary to replace the sealing device, which poses a problem of high costs. Particularly when using slurry containing metal powder such as nickel, the seal part was subject to significant wear, which was a serious problem.

A further problem with sealing devices is that they are comprised of a plurality of complexly shaped parts and have a complex structure as a whole, with seams and irregularities sometimes present. In a wet bead mill having a sealing device, there is a problem that slurry sticks to the seams and uneven portions. Particularly in the processing of raw materials for food and pharmaceuticals, there have been problems such as rotting fixed substances that prevent the products from becoming commercially available, difficult cleaning, and contamination of the slurry after changing types.

On the other hand, there is Bead Mill 3, which is a wet bead mill without a mechanical seal device, but in this system, slurry pressure flowing from the slurry supply port at the bottom of the mill raises the slurry in the gap, and the centrifugal bead separator Due to the effect of the upper plate member (slurry urging means), a flow is created that circulates inside the centrifugal bead separator from between the upper plate of the centrifugal bead separator and the top surface of the cylindrical container, passing near the side of the mill. This structure prevents the slurry containing beads from flowing into the gap.

However, in such a structure, the pressure inside the mill may increase due to various condition changes during operation, and in this case, the bead-containing slurry flows from the outside to the inside over the centrifugal bead separator. It is discharged to the outside of the mill through the above-mentioned gap. As a result, beads leak. In order to prevent this, there are ways to increase the circulating slurry flow rate by improving the shape or increasing the number of impeller members on the top surface of the centrifugal bead separator. However, when the circulating slurry flow rate increases, the slurry flow rate passing through the centrifugal bead separator increases, causing a problem in that beads tend to leak.

Furthermore, this system has a problem in that as the rotational speed of the stirrer and centrifugal bead separator increases, the flow rate of the circulating slurry increases. In other words, if the rotation speed is increased to strengthen the stirring force, the circulating slurry flow rate will increase too much, and the slurry flow rate in the centrifugal bead separator will become excessive, which may deviate from the optimal conditions for preventing bead leakage. there were. On the other hand, when the rotation speed is low, the circulation flow rate is too low, and when the pressure rises due to pressure fluctuations in the mill, the flow to the outside becomes too small, and depending on the conditions, the flow between the top surface of the cylindrical container and the centrifugal bead separator becomes too small. However, there was a problem that a flow from the outside toward the center occurred, causing beads to leak. In this way, in Bead Mill 3, bead leakage does not occur under ideal operating conditions, but bead leakage occurs when the operating conditions of the wet bead mill (peripheral speed of the stirrer, flow rate of processed slurry, etc.) or slurry viscosity change. There was a problem.

In this way, conventional wet bead mills have problems caused by mechanical seals, or even if they are designed to solve these problems, they cannot respond flexibly to changes in operating conditions. . Therefore, new technology to solve these problems has been required.

(1) The wet bead mill of the present invention includes a cylindrical container that stirs a mixture of slurry and beads in an internal space, a slurry storage tank that is installed above the cylindrical container, and a slurry that connects the cylindrical container and the slurry storage tank. The wet bead mill has a flow path, and has a drive device above the slurry storage tank, and a rotating shaft connected to the drive device extends into the cylindrical container via the slurry storage tank and the slurry flow path. A member having a structure in which the slurry inside the slurry flow path flows downward is installed, and a stirrer is connected to stir the mixture of the slurry and beads at an internal position of the cylindrical container to separate the beads in the slurry. The wet bead mill is characterized in that the slurry is discharged from the cylindrical container through an opening different from the slurry flow path after passing through the bead separation device.

(2) Further, a member having a structure in which the slurry flows downward as the rotating shaft rotates in the slurry flow path is installed, a slurry discharge port is installed in the lower lid of the cylindrical container, and the bead separation device , is installed at the slurry discharge port and is configured to separate the beads by contacting them, and the slurry passes from the slurry storage tank through the slurry flow path and into the cylindrical container, The above problem is solved by having a structure in which beads are discharged from the cylindrical container after being separated by the bead separation device.

(3) Further, the bead separation device includes a centrifugal bead separator fixed to the rotating shaft, and the centrifugal bead separator generates centrifugal force when the slurry flows from the outer circumferential side toward the center in the cylindrical container. The centrifugal bead separator is configured to separate beads using A stirrer is fixed to the rotating shaft at a position below the bead separator, and the rotating shaft has a tubular space therein through which slurry can pass from the center of the centrifugal bead separator into the slurry storage tank. . A slurry supply port is installed in the lower lid of the cylindrical container, and a slurry discharge port is installed in the slurry storage tank, and the slurry passes through the cylindrical container from the slurry supply port to the centrifugal bead separator. After entering the slurry storage tank from the center of the slurry tank through the tubular space, a portion of the slurry in the slurry storage tank flows through the slurry flow path due to the rotation of the rotating plate. The above problem is solved by having a structure in which the liquid is forcibly fed to the cylindrical container via the cylindrical container.

(4) Further, the bead separation device includes a stirring bead separator fixed to the rotating shaft, and the stirring bead separator stirs a mixture of slurry and beads in the cylindrical container, and the slurry is placed on the outer peripheral side. The slurry is configured to separate beads by using centrifugal force when flowing toward the center from the slurry, and a plurality of at least one of a plate giving swirl to the slurry and a swirling plate are installed on the upper surface of the stirring bead separator, The rotating shaft has a tubular space therein through which slurry can pass from the center of the stirring bead separator into the slurry storage tank. A slurry supply port is installed in the lower lid of the cylindrical container, and a slurry discharge port is installed in the slurry storage tank, and the slurry passes through the cylindrical container from the slurry supply port to the stirring bead separator. The slurry enters the slurry storage tank from the center via the tubular space and is then discharged to the outside of the apparatus, and a part of the slurry in the slurry storage tank is rotated by the rotation plate to pass through the slurry flow path. The above problem is solved by having a structure in which the liquid is forcibly fed to the cylindrical container.

(5) Furthermore, in the wet bead mill according to any one of (1) to (4), the slurry is directed downwardly to the rotating shaft at a position in the slurry flow path as it rotates in the slurry flow path. The above-mentioned problem is solved by having a pumping member having a structure that allows the flow to flow.
(6) The bead mill according to any one of (3) to (5) above, wherein the centrifugal separator includes an upper plate, a lower plate, and a plurality of the plates, and the plate is The above problem is solved by being provided so as to be connected to the plate and the lower plate.
(7) Furthermore, in the bead mill according to any one of (3) to (6) above, the plate has a receding angle of 15 to 60 degrees in a direction opposite to rotation from the center toward the outer periphery. This solves the above problem.
(8) The bead mill according to any one of (3) to (7) above solves the above problem by having an installation interval of 56 mm or less on the outer periphery of the plate.
(9) The bead mill according to any one of (6) to (8) above, wherein the upper plate of the centrifugal separator has the rotating plate above, and the diameter of the inner peripheral part of the rotating plate is The above-mentioned problem is solved by setting the ratio of the difference in diameter of the outer circumferential portion to the outer circumferential diameter to be 0.2 or more.
(10) The bead mill according to any one of (6) to (9) above, wherein the upper plate of the centrifugal separator has the rotating plate above, and an interval on the outer periphery of the rotating plate is By being 71 mm or less, the above problem is solved.
(11) The bead mill according to any one of (6) to (10), wherein the upper plate of the centrifugal separator has the rotating plate above, and the outer circumferential diameter of the rotating plate is The above problem is solved by having a diameter of 0.9 to 1.2 times the outer circumference of the member that gives swirl to the slurry in the separation device.

Since the wet bead mill of the present invention does not have a rotating part sealing device that comes into contact with the slurry, it solves problems such as contamination of the product slurry by debris of worn seal parts and sealing liquid caused by wear of the contact member of the sealing device of the rotating part. can. Furthermore, it is possible to solve the problem of particles in the slurry sticking to the rotating part sealing device, making it difficult to clean the parts.

FIG. 2 is a diagram showing a first example of the structure of the upper part of the bead mill of the present invention. It is a figure showing the second example of the structure of the upper part of the bead mill of the present invention. This is the first type of bead mill of the present invention, and is an example in which a plug-type bead separation device that forms a gap at the slurry discharge port is installed. This is a second type of bead mill of the present invention, and is an example in which a centrifugal bead separator and a stirrer are installed on a rotating shaft. This is a third type of bead mill of the present invention, and is an example in which a stirring bead separator having a bead centrifugation function and a stirring function is installed on a rotating shaft. 1 is a diagram showing an example of the structure of a centrifugal bead separator used in the present invention.

The present inventors have researched various mechanical structures for omitting the mechanical seal that conventional wet bead mills are equipped with between the rotating shaft and the fixed part. The apparatus of Patent Document 3 was a bead mill that omitted a sealing mechanism due to the structure in which the slurry rose through the gap between the rotating shaft and the opening of the top lid of the cylindrical container. However, the present inventors conducted various experiments and found that, for example, by installing a structure that circulates the slurry on the top surface of the centrifugal bead separator, the slurry was distributed between the top surface of the centrifugal bead separator and the top surface of the cylindrical container from the center to the periphery. Even if a flow is created, beads leakage is likely to occur as long as the slurry rises through the gap on the side of the rotating shaft.

Therefore, as shown in FIG. 1 or 2, a slurry storage tank 8 is installed above the cylindrical container, and in the slurry flow path 7 installed above the rotating shaft 9 and the top lid 2 of the cylindrical container. A vertical wet bead mill equipped with a device for lowering the slurry in the slurry storage tank 8 was invented. The present invention can be broadly divided into a first form and a second form. The first type is a bead mill that uses relatively large beads and uses a contact type bead separation device. The second type is a bead mill that uses relatively small beads and uses a centrifugal bead separation device.

In the wet bead mill of the present invention, the slurry enters the cylindrical container from the slurry storage tank 8 via the slurry channel 7, thereby applying pressure inside the cylindrical container without installing a mechanical seal on the rotating shaft 9. This makes it possible to fill the slurry in the same state. Note that the slurry in the cylindrical container is discharged from a slurry outlet provided at a position different from the slurry channel 7 via a bead separation device installed inside the cylindrical container.

As shown in FIG. 1, above the slurry storage tank 8 there is a shaft drive pulley 11 which is a drive device for the rotation shaft 9, and the rotation shaft 9 connected to the shaft drive pulley 11 passes through the slurry storage tank 8 and the slurry channel 7. and extends into the cylindrical container. The drive device does not necessarily have to be a pulley, and may be a gear type or a direct motor-coupled type. A pumping member 10 is installed on the rotating shaft 9 at a position inside the slurry channel 7, and the rotation of the pumping member 10 forces the slurry in the slurry storage tank 8 into the cylindrical container. Although not shown in FIG. 1, a stirring member or the like is connected to the rotating shaft 9 at a position inside the cylindrical container, and stirs the mixture of slurry and beads inside the cylindrical container. In addition, in FIG. 1, only the structure of the upper part of the said cylindrical container is described for simplification. The component that causes the slurry to flow downward does not necessarily have to be the pumping member 10, nor does it need to be inside the slurry channel 7. For example, at the top of the mill, a rotary disk with multiple stirring rods (impellers) and a stirring plate on the top surface is installed on the rotating shaft, and the centrifugal force generated by the rotation of these parts creates a slurry flow path. It is also possible to flow the slurry in step 7 downward. An example of its structure is shown in FIG. In this example, a disk 28 is installed in the mill, and a plurality of upper blades 29 having a structure similar to a centrifugal pump are installed on the upper surface of the disk 28.The centrifugal force generated by the upper blades 29 causes the slurry flow path to can be poured into the cylindrical container.

A configuration in which the slurry is supplied from the slurry storage tank 8 to the cylindrical container via the slurry channel 7, stirred, and then discharged to the outside via the bead separator 5 installed in the lower lid 3. (first form). (Described in FIG. 3) This mainly consists of a slurry storage tank 8, a slurry flow path 7, a cylindrical part 1 forming a cylindrical container, an upper lid 2 and a lower lid 3, a rotating shaft 9, a pumping member 10, a stirrer 4, and a lower lid. 3 and a slurry discharge port 6. In this type, the bead separation device does not necessarily have the structure shown in FIG. 3, but any contact separation device (slit type, screen type) may be used.

Further, the slurry is supplied from the lower part of the cylindrical container, and after being processed in the cylindrical container, the slurry applied to the rotating shaft 9 is transferred from the cylindrical container to the slurry through a centrifugal bead separation device. There is a form (second form) in which the slurry is discharged into the slurry storage tank 8 via a tubular space for flowing into the storage tank 8. (See FIG. 4) In the latter method, a part of the slurry in the slurry storage tank 8 is forced into the cylindrical container via the slurry flow path 7 by a pumping member 10 installed in the slurry flow path 7. Prevent beads leakage by flushing the beads.

In the first form (first type), the slurry is first supplied to the slurry storage tank 8. A pumping member 10 installed in a slurry flow path 7 formed between a rotating shaft 9 and an upper lid 2 causes slurry to flow from a slurry storage tank 8 to the cylindrical container. By forcibly lowering the slurry in the slurry channel 7 by the pumping member 10, it is possible to prevent the slurry containing beads that has not passed through the bead separation device from flowing back from the cylindrical container to the slurry storage tank 8. It can be prevented.
However, if the pump for sucking the slurry from inside the mill can ensure a sufficient suction flow rate and cavitation due to negative pressure does not occur, the pumping member 10 may be omitted. Depending on the liquid feeding capacity of the pumping member 10, it may be possible to supply the slurry necessary for processing into the mill, but when flowing slurry in excess of the liquid feeding capacity of the pumping member 10, the pipe 18 connected to the slurry discharge port 6 may be A pump 17 may be installed to suck the slurry in the cylindrical container to increase the slurry flow rate.

The slurry supplied to the cylindrical container forms a mixture with the beads. By stirring this mixture with a stirrer 4, particles in the slurry are crushed or dispersed. Thereafter, the beads are separated. In the first type of bead mill of the present invention, a bead separation device of the type that separates the beads by passing the slurry through a narrow gap is used. A movable separator (bead separator 5) in the shape of a stopper with a downwardly expanding taper is used at the slurry discharge port 6. During the treatment, the gap between the bead separator 5 and the slurry discharge port 6 is opened so that beads do not leak. Further, the bead separator 5 may be a slit-type separator or a screen-type separator with a taper that narrows downward. The slurry from which beads have been separated by the bead separator 5 is discharged from the cylindrical container and sent to the slurry tank 15 through a pipe 18.

The pumping member 10 may be of any structure as long as it provides a flow to the slurry through rotation, such as a screw type installed in the slurry flow path 7 (shown in FIG. 1), or a screw type installed in a cylindrical structure. A cut structure (shown in FIGS. 3 and 4), an axial flow type or a centrifugal type installed in the cylindrical container (shown in FIG. 2), etc. are preferable. It is desirable that the structure is such that the downward flow velocity of the slurry in the slurry flow path 7 by the pumping member 10 alone is 5 mm/sec or more. This is a condition to prevent the slurry from flowing back upward in the slurry flow path 7 due to a change in the pressure inside the mill. Further, the maximum value is determined by the set flow rate required for processing. If the slurry flow rate generated by the pumping member 10 or the like is smaller than the set flow rate required for processing, a pump 17 is installed in the pipe 18 connecting the slurry discharge port 6 and the slurry tank 15 to suck the slurry in the cylindrical container. . Further, in the centrifugal pumping device shown in FIG. 2, the number of upper blades 29 is preferably about 4 to 16, and the interval between the outer circumferences is preferably 30 to 60 mm.

The stirrer 4 may have any structure as long as it can mix the beads and slurry efficiently, and may be rod-shaped, disc-shaped, plate-shaped, etc. In Fig. 3, a pin-type stirrer is used. 4 examples were shown. The cylindrical container has an inner surface that is almost rotationally symmetrical with respect to the central axis, except for partially installed members and recesses, and does not change in the height direction even if the diameter is constant. You can leave it there. Note that the cylindrical container may be provided with a water cooling jacket for cooling the slurry inside. Further, the slurry storage tank 8 may be of any shape or type as long as it can hold slurry and has an opening or groove through which the slurry flows.

The second form is further structurally divided into two categories (second form and third form). First, the second type of bead mill is shown in FIG. 4, and mainly includes a slurry storage tank 8, a slurry channel 7, a rotating shaft 9, a cylindrical part 1 forming a cylindrical container, an upper lid 2, a lower lid 3, and a stirrer. 4 and a centrifugal bead separator 20. Slurry is supplied from a slurry supply port 22 installed in the lower lid 3. The slurry is processed by being stirred by the rotation of the stirrer 4 installed on the rotating shaft 9 while rising inside the cylindrical container. Thereafter, the slurry is separated from beads in the slurry by a centrifugal bead separator 20 installed on the rotating shaft 9 in the upper part of the cylindrical container, and then passed through the tubular space 21 in the rotating shaft 9 and passed through the cylindrical container. It flows into the slurry reservoir 8 above the vessel. In addition, by rotating the rotating plate 27 installed on the upper circular plate 24 on the top surface of the centrifugal bead separator 20, a forced slurry downward flow is created in the slurry flow path 7, and a part of the slurry in the slurry storage tank 8 is removed. Flow into the cylindrical container. This downward flow prevents the slurry containing beads in the slurry flow path 7 from rising, thereby preventing bead leakage and applying pressure inside the cylindrical container. The slurry flowing into the cylindrical container from the slurry channel 7 passes through the centrifugal bead separator 20, passes through the tubular space 21, and returns to the slurry storage tank 8 again. Note that, as long as the functions are the same, the rotating plate 27 may not be installed on the upper circular plate 24 but may be installed at another position such as the lower part of the pumping member 10.

The rotating plate 27 is located on the upper surface of the centrifugal bead separator 20 and has the function of flowing the slurry between the upper lid 2 and the upper circular plate 24 from the inside to the outside by centrifugal force. As a result, a downward flow of slurry is formed in the slurry flow path 7. It is even better if the outer peripheral side of the rotating plate 27 is set back by 10 to 40 degrees with respect to the direction of rotation. Furthermore, the turning plate 27 may be linear or bent. It is preferable that the rotating plate 27 generates approximately the same centrifugal force as the plate 26. In experiments conducted by the present inventors, the outer diameter ratio of the rotating plate 27 to the plate 26 was preferably 0.9 to 1.2 times. If it is less than 0.9 times, there is a problem that the slurry will flow back at low rotation speeds, and if it is more than 1.2 times, the amount of circulating slurry will increase too much during high speed rotations, and the flow rate in the bead separation section will increase. There was a problem with the beads leaking.

In order to more effectively prevent bead leakage, it is preferable to set the rotation plates 27 at appropriate intervals. Desirably, the interval between the outer peripheries of the rotating plates 27 is 71 mm or less, more preferably 51 mm or less. Furthermore, the length of the pivot plate 27 is also an important design element. Since the rotating plate 27 is not necessarily linear or installed in the diametrical direction, the length of the rotating plate 27 is defined as 1/2 of the difference between the outer circumferential diameter and the inner circumferential diameter of the rotating plate 27. A good condition is that the length should be at least 0.2 times the outer diameter. From a mechanical structural point of view, it is difficult to increase the ratio to 0.4 times or more, so a ratio of 0.2 to 0.4 times is good as an actual design condition. Although the pumping member 10 is not necessarily required in this structure, the pumping member 10 may be installed in order to cope with insufficient pressure or instability to form a downward flow of slurry in the slurry flow path 7.

The centrifugal bead separator 20 has a structure in which a member having a structure that gives swirl to the slurry on its outer periphery is installed, and the member has a gap through which the slurry can pass. The slurry flows toward the center while rotating. At this time, the centrifugal force pushes out beads with a large specific gravity in the outer circumferential direction, thereby separating the beads. The centrifugal bead separator 20 has various shapes; for example, a plurality of plates 26 are installed between an upper circular plate 24 and a lower circular plate 25, which are circular plates as shown in FIG. There is something. In the centrifugal bead separator 20 having this structure, it is preferable that the plate 26 is installed with the outer side set back with respect to the direction of rotation. The diametrical length L of the installed plate 26 is preferably 0.2 times or more the outer circumferential diameter of the plate 26. Further, a better condition is that the receding angle of the plate 26 is 15 to 60 degrees, and a better condition is that the installation pitch of the plate 26 is 56 mm or less based on the outer peripheral edge, and even better is 42 mm or less.

A third type of bead mill is shown in FIG. 5, and is a bead mill mainly composed of a slurry storage tank 8, a rotating shaft 9, a pumping member 10, a cylindrical container, and a stirring bead separator 23. This type is a centrifugal bead separator with a stirring function, and is different from the second type bead mill in that the stirrer 4 is omitted. The structure of the rotating shaft 9 and the stirring bead separator 24 is similar to the combination of the rotating shaft 9 and the centrifugal bead separator 20 of the second type bead mill. A tubular space 21 extending into the slurry storage tank 8 is provided. The stirring bead separator 23 stirs the mixture of beads and slurry and at the same time separates the beads using centrifugal force. As an example of the shape, as shown in FIG. 6, there is one in which a plurality of plates 26 are installed between an upper circular plate 24 and a lower circular plate 25. The details of this construction are similar to the construction requirements of the second type of bead mill, and the configuration of the plate 26 is also similar, although it may be made longer in the longitudinal direction. Further, similarly to the second type of bead mill, a rotating plate 27 is installed on the upper circular plate 24 on the top surface of the stirring bead separator 23. The rotation of the swirl plate 27 creates a slurry flow from the inside to the outside, resulting in a downward flow in the slurry channel 7 . Similar to the second type of bead mill, a pumping member 10 may be installed on the rotating shaft 9.

Slurry is supplied from a slurry supply port 22 installed in the lower lid 3. The slurry is treated by stirring the mixture of beads and slurry by rotating the stirring bead separator 23. Thereafter, the slurry is separated into beads by centrifugal force as it passes between the plates 26 of the stirring bead separator 23, and then flows into the slurry storage tank 8 through the tubular space 21 in the rotating shaft 9. Furthermore, the flow state of the slurry in the slurry channel 7 is equivalent to that of the second type bead mill.

The operational characteristics of the three types of wet bead mills explained above are as follows. The first type of wet bead mill can use beads with a diameter of 0.2 mm or more, and as a result, processes with a relatively large impact force are performed. It is often used in pulverization processes where the product particle size ranges from microns to 150 nanometers. The second type of wet bead mill can use beads with a diameter of 50 μm or more and performs processing with relatively low impact force. It is often used for processing dispersion conditions where the product particle size ranges from submicron to nanometer units. The wet bead mill of the third form can use a bead diameter of 50 μm or more like the second form, but it is also capable of processing with a smaller impact force and processing with a larger flow rate. It is used for dispersion conditions where the product particle size ranges from submicron to nanometer scale, and for processing where particle damage is a concern.

When the wet bead mill described above is operated in circulation, it is desirable to install a tank in addition to the wet bead mills of the first to third types. Particularly, in the first type of bead mill shown in FIG. 3, the installation of a slurry tank 15 is effective as a measure to simplify the water level control of the slurry storage tank 8. In FIG. 3, a slurry tank 15 is installed, and the slurry storage tank 8 and the slurry tank 15 are connected by a water channel 16 that allows slurry to flow from the slurry tank 15 to the slurry storage tank 8 in a state where no pressure is applied. The water channel 16 may be in the form of an open gutter or may be in the form of a pipe. It is preferable to make the water level of the slurry tank 15 and the slurry storage tank 8 common, or to make the water level of the slurry tank 15 higher than the water level of the slurry storage tank so that the slurry in the slurry tank 15 overflows. In the case of this structure, the water levels in the slurry tank 15 and the slurry storage tank 8 do not change under conditions where the slurry amount does not change during processing, so there is an advantage that liquid level control is not required.

As an example of the first type of wet bead mill, the results of a dispersion treatment experiment using the wet bead mill of the present invention shown in FIG. 3 are shown. The size of the device was such that the inner diameter of the cylindrical container was 120 mm and the inner height was 210 mm. The rotational diameter of the stirring bar 4 was 112 mm, and six stirring bars 4 were installed. The effective volume of this device after subtracting the volume of internal parts such as the stirrer 4 was 1.6 liters. An experiment was conducted by using zirconia beads made by Nikkato with a diameter of 0.5 mm and supplying room temperature water at a flow rate of 100 liters/hour. The pumping member 10 uses a cylindrical impeller with spiral stripes as shown in FIG. We installed one designed to deliver 24 liters of liquid per hour. Since the slurry supply is insufficient with the pumping member 10 alone, a pump 17 is installed in the pipe 18 connected to the slurry discharge port 6, and the device is configured to suck the slurry from the wet bead mill and send it to the slurry tank 15.

As an example of the second type of wet bead mill, barium titanate particles were subjected to dispersion treatment using the wet bead mill of the present invention shown in FIG. However, the pumping member 10 was not installed in this mill. The size of the device was such that the inner diameter of the cylindrical container was 120 mm and the inner height was 210 mm. The stirring bar 4 had a rotational diameter of 112 mm, and the stirring bar 4 was installed in which members each having a pair of pins were fixed in four stages. First, an experiment was conducted using a centrifugal bead separator 20 having the following configuration. The centrifugal bead separator 20 had 12 plates 26 installed in upper and lower disks of the type shown in FIG. 6, and had an outer diameter of 110 mm and a height of the plates 26 of 35 mm. The installation angle of the plate was a setback angle of 30 degrees, and the length of the plate 26 was 22 mm. Six rotating plates 27 were installed, each having an outer diameter of 115 mm, a length of 25 mm, and a height of 12 mm. The distance between the upper lid 2 and the rotating plate 27 was 4 mm. The outer diameter of the lower end of the pumping member 10 was 80 mm. The slurry descending speed in the pumping member 10 was 5 mm/sec when the outer peripheral speed of the plate 26 was 6 m/sec, and 21 mm/sec when the outer circumferential velocity of the plate 26 was 12 m/sec. The effective volume of this device after subtracting the volume of internal parts such as the stirrer 4 was 1.55 liters.Using Nikkato's zirconia beads with a diameter of 0.1 mm, water at room temperature was poured into the mill at 100 liters/hour. It was operated under the conditions supplied.

Next, in the same manner as in the above experiment, an investigation was conducted on the appropriate structure of a centrifugal bead separator of the type shown in FIG. 6 using the same equipment and under the same operating conditions. Important structural configurations for more stable bead separation are the installation interval and angle of the plates 26. Therefore, we investigated the appropriate range for both. Table 1 shows the effect of the sweepback angle on the direction of rotation of the plate 26. The number of plates 26 used in the experiment was eight. (Plate spacing is 42 mm) When the receding angle is 0 degrees, a considerable amount of bead leakage is confirmed when the outer peripheral speed of the plate 26 is 6 m/sec, and a very small amount of bead leakage is observed between 7 and 8 m/sec. However, beads could be separated without any problems at speeds of 10 m/sec or higher. Thus, beads could be separated at a receding angle of 10 degrees or less, but the beads tended to leak when rotating at low speed. On the other hand, when the receding angle was from 15 to 60 degrees, extremely good bead separation was achieved as shown in Table 1.

Next, the influence of the installation interval of the plates 26 on the bead separation performance was investigated. Note that the configuration of parts other than the plate 26 was the same as in the experiments in paragraphs 0041 and 0042 above. Table 2 shows the results of installing 4 to 12 plates 26 with a receding angle of 30 degrees. When four plates were installed, the interval between the plates 26 was 85 mm, and a small amount of beads leaked at a peripheral speed of 10 m/sec, and a considerable amount of beads leaked at a peripheral speed of 8 m/sec. When six plates were installed, the interval between the plates 26 was 56 m, and no bead leakage was observed at 8 m/s, but a small amount of beads leaked at a peripheral speed of 6 m/s, which is the lowest speed in general processing. was confirmed. When the distance was 42 mm or less, no bead leakage was observed even at 6 m/sec. Generally, operation is possible even if there is a trace amount of bead leakage, so the distance between the plates 26 is desirably 56 mm or less, and even better if it is 42 mm or less. Based on the above experimental results, the centrifugal bead separator 20 was used in the following processing experiments, with the number of plates 26 being 8, the length L being 36 mm, and the receding angle being 30 degrees. In addition, here, the speed at the time of micro leakage is the minimum or maximum outer peripheral speed of the plate 26 at which 0.2 g or less of beads leaks per 10 minutes, and the speed at the time of leakage is the minimum or maximum peripheral speed of the plate 26 at which 0.2 g or less of beads leaks per 10 minutes. This is the minimum or maximum peripheral speed at which leakage occurs. Also, - in the table means no leakage.

Table 3 shows the results of an investigation into the influence of the interval between the outer circumferences of the rotating plates 27 on bead leakage. The dimensions of the container of the device used (consisting of cylinder 1, upper lid 2, and lower lid 3) were 120 mm in inner diameter and 210 mm in height, and 8 plates 26 were installed, and the outer diameter was 90 mm. . The length of the rotating plate 27 was 35 mm, and the outer diameter of the rotating plate 27 was 98 mm. Zirconia beads with a diameter of 0.1 mm were used, and water at room temperature was supplied into the mill at 100 liters/hour. Experiments were conducted under the conditions that the outer peripheral speed of the plate 26 was 10 m/sec and the number of rotating plates 27 was 4, 6, 8, and 12. When 4 plates were installed, a small amount of bead leakage was observed, but it did not last for several hours. If so, it was at a level that would allow him to continue driving. Although a very small amount of beads leaked when six disks were installed, it was possible to continue operation for a long time, and the amount of beads leaked in the slurry after treatment was small, so they could be easily separated using a filtration device outside the process. Ta. No bead leakage was observed in the operation with 8 or more beads. Therefore, the installation interval (outer periphery) of the rotating plates 27 is preferably 71 mm, and even better is 51 mm. Note that 3.4 kg of beads were charged into the mill before operation.

Table 4 shows experimental results regarding the length of the rotating plate 27 (1/2 of the difference between the outer circumferential diameter and the inner circumferential diameter). The equipment conditions and operating conditions other than the equipment configuration of the rotating plate 27 were the same as in the experiment in paragraph 0044 above. The operation was carried out under four conditions in which the number of rotating plates 27, which were good in the above experiment, was 8 and the length was 16 to 38 mm. When the length was 16 mm, there was a small amount of bead leakage, but when the length was 20 mm or more, there was no bead leakage. In other words, it has been found that the ratio of the length of the rotating plate 27 to the outer diameter is preferably 0.2 or more.

また、表２から５に記載の実験と同様の条件で０．３ｍｍ径のジルコニア製ビーズでの実験では、すべての条件でビーズ漏洩は認められなかった。 Next, Table 5 shows the results of investigating the influence of the ratio of the outer circumferential diameter of the rotating plate 27 and the outer circumferential diameter of the plate 26 on bead leakage. Similarly, the dimensions of the container of the device used were 120 mm in inner diameter and 210 mm in height, 8 plates 26 were installed, and the outer diameter was 90 mm. The number of rotating plates 27 installed was eight, and the length was 27 mm. Zirconia beads with a diameter of 0.1 mm were used, and water at room temperature was supplied into the mill at 100 liters/hour. When the ratio of rotating plate outer diameter/plate outer diameter was in the range of 0.89 to 1.17, no bead leakage was observed when the peripheral speed of the plate 26 was in the range of 5 to 12 m/sec. On the other hand, when the above ratio was 0.78, bead leakage was observed on the low speed side. A slight amount of bead leakage was observed at an outer peripheral speed of the plate 26 of 10 m/sec or less, and a considerable amount of bead leakage was observed at a speed of 6 m/sec or less. On the other hand, when the above ratio was 1.24, there was bead leakage on the high speed side. A slight amount of bead leakage was observed at an outer peripheral speed of the plate 26 of 9 m/sec or more, and a considerable amount of bead leakage was observed at 12 m/sec.

In addition, in experiments using 0.3 mm diameter zirconia beads under the same conditions as the experiments described in Tables 2 to 5, no bead leakage was observed under all conditions.

As an example of the third type of wet bead mill, barium titanate particles were subjected to a dispersion treatment using the wet bead mill of the present invention shown in FIG. The size of the device was such that the inner diameter of the cylindrical container was 120 mm and the inner height was 75 mm. The rotational diameter of the stirring bead separator 23 was 105 mm, and the effective volume after subtracting the volume of internal parts such as the stirring bar 4 of this apparatus was 0.6 liters. In the treatment experiment, a stirred bead separator 24 was used, in which the number of plates 26 was 12, the length L was 40 mm, the outer diameter was 100 mm, and the receding angle was 15 degrees. Eight rotating plates 27 were installed, each having an outer diameter of 105 mm, a length of 28 mm, and a height of 12 mm. In addition, the pumping member 10 was designed to have a flow rate of 12 liters per hour at a predetermined rotation speed (when the outer peripheral speed of the stirring bead separator 23 is 10 m/sec) and a downward flow rate of 15 mm/sec. . As a result of conducting a bead leakage experiment using water at room temperature and using 0.2 mm diameter zirconia beads, no bead leakage was observed within the peripheral speed range of the plate 26 of 6 to 12 m/sec.

In the following experiments, Example 1 was a device of the first form, Example 2 was a device of a second form, and Example 3 was a device of a third form, each having the device structure of the above dimensions. In Comparative Examples 1 to 3, comparative experiments were also conducted using bead mills that had the same structure and dimensions as the first to third types of wet bead mills, but had mechanical seals. In the processing of Examples and Comparative Examples, the raw materials, stirring conditions, slurry flow rate, etc. were the same. The experimental results are shown in Table 6.

In Experiment 1 (Example 1 and Comparative Example 1), the first type wet bead mill was used, and the raw material slurry was metallic nickel powder with a primary particle size of 0.53 micrometers and a secondary particle size of 4.7 micrometers. The volume was 15 liters of tapionol solution containing 5% by mass. In Example 1 and Comparative Example 1, beads with a diameter of 0.3 mm were used, the peripheral speed of the stirrer 4 was set to 10 m/sec, and the slurry flow rate was 30 liters per hour.

In Example 1 and Comparative Example 1, the dispersion treatment was performed for 4 hours, and the secondary particle diameter of the particles in the slurry was measured. No bead leakage was observed in any of the treatments. In these treatments, the secondary nickel particle size after treatment was 0.63 micrometers at 50% diameter (D50) from the small particle size side in Example 1, and 1 at 90% diameter (D90) from the small particle size side in Example 1. In Comparative Example 1, D50 was 0.62 micrometers and D90 was 1.21 micrometers. In both cases, the particle size was sufficient to satisfy the purpose of treatment.

Regarding the influence of the metal nickel particles in the slurry on the bead mill parts, in Comparative Example 1, wear of the mechanical seal was confirmed, and contamination was observed in the product slurry, although the metal parts of the mechanical seal were powdered. On the other hand, in Example 1, in which the pumping member 10 was installed as a substitute for the mechanical seal, no wear of the pumping member 10 or other parts, and no foreign matter mixing into the slurry was observed. In this way, the wet bead mill of the present invention is capable of processing highly abrasive slurry containing metal powder, etc. without causing any wear on parts, allowing stable processing over a long period of time, and improving mechanical seal performance. Slurry contamination due to worn parts is also eliminated.

In Experiment 2 (Example 2 and Comparative Example 2), a second type of wet bead mill of the present invention was used. The raw material slurry was 15 liters of a glycol solution containing 10% by mass of blue organic pigment powder with a secondary particle diameter of 0.25 micrometers and a primary diameter of 53 nanometers. In Example 2 and Comparative Example 2, using the above-mentioned apparatus, beads with a diameter of 50 μm were used, the peripheral speed of the stirrer 4 was set to 10 m/sec, and the slurry flow rate was 30 liters per hour for 4 hours. No bead leakage was observed in any of the treatments of Example 2 and Comparative Example 2. Regarding the particle diameter after treatment, D50 was 72 nanometers in Example 2, and D50 was 74 nanometers in Comparative Example 2, which were similar results. In Comparative Example 2, the pigment leaked into the sealing liquid (alcohol for pressurizing the seal) used in the mechanical seal, and the sealing liquid was colored and adhered substances were observed on the mechanical seal. When operated for a long time, the mechanical seal may be damaged due to stuck objects. On the other hand, in Example 2, such a problem could be avoided because a wet bead mill without a mechanical seal was used.

In Experiment 3 (Example 3 and Comparative Example 3), a third type wet bead mill was used, and the raw material slurry was silicone containing 12% by mass of titanium oxide powder with a secondary particle diameter of 101 nanometers and a primary diameter of 29 nanometers. The oil solution was 15 liters. Using beads with a diameter of 30 μm, the peripheral speed of the stirring bead separator 24 was set to 12 m/sec, and the slurry was processed at a flow rate of 30 liters per hour. No bead leakage was observed in any of the treatments of Example 3 and Comparative Example 3. After each treatment for 5 hours, the particle size was similar to that of Example 3 with a D50 of 34 nanometers and Comparative Example 3 with a D50 of 36 nanometers. In Comparative Example 3, silicone oil was used as the sealing liquid for the mechanical seal in order to prevent foreign liquid from entering the silicone oil forming the slurry. As a result, even after the 2-hour treatment, solid dehydrogenated silicone oil remained stuck to the mechanical seal. On the other hand, in Example 3, such a problem could be avoided because a wet bead mill without a mechanical seal was used.

As explained above, it has been found that the wet bead mill of the present invention, even without a sealing mechanism, does not leak beads and has crushing and dispersion processing capabilities equivalent to those of conventional wet bead mills. Furthermore, since there is no seal structure for the rotating part, there are no problems related to abrasion or damage to the seal member and leakage of seal liquid, which are problems caused by mechanical factors of the seal mechanism.

The wet bead mill according to the present invention grinds slurry containing powders of ceramics, carbon nanotubes, cellulose nanofibers, pigments, inks, paints, organic pigments, dielectrics, magnetic materials, inorganic materials, organic materials, pharmaceuticals, foods, metals, etc. Suitable for processing and distributed processing.

1... Cylindrical part 2... Upper lid 3... Lower lid 4... Stirrer 5... Bead separator 6... Slurry discharge port 7... Slurry channel 8... Slurry storage tank 9...Rotating shaft 10...Pumping member 11...Shaft drive pulley 12...Belt 13...Motor side pulley 14...Drive motor 15...Slurry tank 16...Waterway 17... ... Pump 18 ... Piping 19 ... Stirring device 20 ... Centrifugal bead separator 21 ... Tubular space 22 ... Slurry supply port 23 ... Stirring bead separator 24 ... Upper circular plate 25...Lower circular plate 26...Plate 27...Swivel plate 28...Disc 29...Upper blade

Claims (11)

A wet bead mill comprising: a cylindrical container for stirring a mixture of slurry and beads in an internal space; a slurry storage tank installed above the cylindrical container; and a slurry channel connecting the cylindrical container and the slurry storage tank. ,
a driving device is provided above the slurry storage tank, and a rotating shaft connected to the driving device extends to the cylindrical container via the slurry storage tank and the slurry flow path;
The rotating shaft is connected to a member that causes the slurry inside the slurry flow path to flow downward, and a stirrer that stirs the mixture of the slurry and beads at an internal position of the cylindrical container,
A wet bead mill characterized in that the slurry is discharged from the cylindrical container through an opening different from the slurry flow path after passing through a bead separation device that separates beads in the slurry. It has a structure in which the slurry flows downward as the rotation shaft in the slurry flow path rotates,
A slurry outlet is installed in the lower lid of the cylindrical container,
The bead separation device has a structure configured to separate beads by bringing the beads into contact with a gap,
A structure characterized in that the slurry is discharged from the cylindrical container after passing through the cylindrical container from the slurry storage tank via the slurry flow path and separating beads in the bead separation device. Item 1. Wet bead mill according to item 1. The bead separation device includes a centrifugal bead separator fixed to the rotating shaft,
The centrifugal bead separator is configured to separate beads using centrifugal force when the slurry flows from the outer circumferential side toward the center in the cylindrical container,
and a plurality of at least one of a plate giving swirl to the slurry and a rotation plate are installed on the upper surface of the centrifugal bead separator,
A stirrer is fixed to the rotating shaft at a position below the centrifugal bead separator,
The rotating shaft has a tubular space therein through which slurry can pass from the center of the centrifugal bead separator into the slurry storage tank,
A slurry supply port is installed in the lower lid of the cylindrical container, and a slurry discharge port is installed in the slurry storage tank,
The slurry passes through the cylindrical container from the slurry supply port, passes through the tubular space from the center of the centrifugal bead separator, enters the slurry storage tank, and is then discharged to the outside of the device,
A part of the slurry in the slurry storage tank is forcibly delivered to the cylindrical container via the slurry flow path by rotation of at least one of the plate and the rotating plate. The wet bead mill according to claim 1. The bead separator includes a stirring bead separator fixed to the rotating shaft,
The stirring bead separator is configured to stir a mixture of slurry and beads in the cylindrical container and to separate beads using centrifugal force when the slurry flows from the outer circumferential side toward the center,
and a plurality of at least one of a plate giving swirl to the slurry and a swirling plate are installed on the upper surface of the stirring bead separator,
The rotating shaft has a tubular space therein through which slurry can pass from the center of the stirring bead separator into the slurry storage tank,
A slurry supply port is installed in the lower lid of the cylindrical container, and a slurry discharge port is installed in the slurry storage tank,
The slurry passes through the cylindrical container from the slurry supply port, passes through the tubular space from the center of the stirring bead separator, enters the slurry storage tank, and is then discharged to the outside of the apparatus,
The structure is characterized in that a part of the slurry in the slurry storage tank is forcibly sent to the cylindrical container via the slurry flow path by rotation of at least one of the plate and the rotating plate. The wet bead mill according to claim 1. The wet type according to any one of claims 1 to 4, further comprising a pumping member located at a position in the slurry flow path of the rotating shaft and configured to flow the slurry in the slurry flow path downward as it rotates. bead mill. The centrifugal separator includes an upper plate, a lower plate, and a plurality of the plates,
The wet bead mill according to any one of claims 3 to 5, wherein the plate is provided so as to be connected to the upper plate and the lower plate. The wet bead mill according to claim 3, wherein the plate has a receding angle of 15 to 60 degrees in the direction opposite to rotation from the center toward the outer periphery. The wet bead mill according to any one of claims 3 to 7, wherein an installation interval on the outer periphery of the plates is 56 mm or less. the top plate of the centrifugal separator has a swirl plate above;
The wet bead mill according to any one of claims 6 to 8, wherein the ratio of the difference between the diameter of the inner peripheral part and the diameter of the outer peripheral part of the rotating plate to the outer peripheral diameter is 0.2 or more. the top plate of the centrifugal separator has a swirl plate above;
The wet bead mill according to any one of claims 6 to 9, wherein the distance between the rotating plates on the outer periphery is 71 mm or less. the top plate of the centrifugal separator has a swirl plate above;
Wet type according to any one of claims 6 to 10, characterized in that the outer circumferential diameter of the swirling plate is 0.9 to 1.2 times the outer circumferential diameter of the member that gives swirl to the slurry of the centrifugal separator. bead mill.

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