JP3718831B2 - Bead mill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an annular type bead mill having a cylindrical rotor, and in particular, a pigment blended in a paste to be dispersed in a dispersion step of a water-based paint or an organic solvent-based paint, that is, a pigment composed of secondary particles. The present invention relates to a bead mill for obtaining a dispersion paste in which an aggregate is dispersed in primary particles and a pigment is uniformly dispersed.
[0002]
[Prior art]
In a conventional bead mill, a gap separator or a separation screen is generally known as a mechanism for separating a dispersion paste obtained by dispersing a pigment and a dispersed media (so-called beads).
[0003]
[Problems to be solved by the invention]
However, in recent years, a demand for finer dispersion has increased, and a bead mill capable of using a dispersion medium having a small particle diameter has been demanded. However, there is a limit in a screen or a gap separator.
[0004]
That is, in the gap separator that separates the dispersion paste and the dispersion media by the clearance between the rotor and the stator fixed to the bezel, the rotor has a rotational axis that expands and contracts due to thermal expansion, so the clearance is limited to 0.1 mm. The dispersion media having a diameter of 0.3 mm to 0.5 mm can be used. Moreover, in the case of a dispersion paste such as a paint or ink having a relatively high viscosity, if the clear run between the rotor and the stator of the gap separator is reduced, the pressure loss increases, so that a media having a diameter of 0.5 mm is the use limit.
[0005]
In addition, the screen has a larger opening area (total area) than the gap separator, but since the flow of the liquid is worse than that of the gap separator, the clearance is limited to about 0.1 mm, and the dispersion has a diameter of 0.3 mm. The media is the limit. In particular, a dispersion paste having a large structural viscosity has a disadvantage that pressure loss increases. Furthermore, problems such as clogging due to dispersed pigments and abrasion due to dispersed media are likely to occur.
[0006]
Accordingly, an object of the present invention is to provide a bead mill for dispersing a pigment in which a dispersed media having a fine particle diameter can be used without causing clogging due to an undispersed pigment or abrasion due to a dispersed media.
[0007]
[Means for Solving the Problems]
The object of the present invention is to form a vessel having a supply port for supplying the paste to be dispersed and a discharge port for discharging the dispersed paste, and an annular gap for dispersion between the inner wall of the vessel. An annular bead mill having an outer circumferential surface arranged in the bezel having a cylindrical rotor, and a flow path from the annular gap to the discharge port through the interior of the rotor is formed. A centrifuge for centrifuging the dispersion media from the dispersion paste is provided in the middle of the flow path, and a circulation opening for sending the centrifuged dispersion media to the annular gap is formed in the rotor. It is achieved by a bead mill characterized by
[0008]
It is preferable that the centrifuge has a rotating body that performs centrifugal separation of the dispersed media, and the rotating body is an impeller.
[0009]
The rotating body may be a rotating disk instead of the impeller.
[0010]
It is preferable that the rotational drive shaft of the rotor is a hollow shaft, and a discharge opening that communicates with the discharge port is formed in the hollow shaft.
[0011]
The supply port is disposed on one end side of the vessel, further includes a substantially cylindrical stator disposed on the other end side of the vessel and on the inner side of the rotor, and between the stator and the rotor. It is preferable to form a gap that constitutes a part of the flow path.
[0012]
The rotational drive shaft of the rotor of the centrifugal separator is inserted into the hollow shaft of the rotor, and the flow leading to the discharge opening is between the hollow shaft inner peripheral wall of the rotor and the rotational drive shaft of the rotor. It is preferable to form a gap constituting the path.
[0013]
It is preferable that the rotation drive shaft of the rotor and the rotation drive shaft of the rotating body are arranged concentrically.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of a bead mill according to the present invention will be described below with reference to the drawings. 1 is a longitudinal sectional view of a bead mill, and FIG. 2 is a sectional view taken along line AA of FIG. In addition, the same code | symbol was attached | subjected to the same component through the whole figure.
[0015]
As shown in FIGS. 1 and 2, the bead mill 1 includes a rotor 4 having a cylindrical outer peripheral surface inside a vessel 3 in which a supply port 2 is formed. An annular gap X for dispersing the pigment is formed between the inner wall of the vessel 3 and the outer peripheral wall of the rotor 4.
[0016]
The rotational drive shaft 4a of the rotor 4 is a hollow shaft, and a discharge opening 5 is formed in the hollow shaft. A flow path 6 is formed from the hollow portion 4x of the rotation drive shaft 4a through the inside of the rotor 4 and opening toward the bottom of the rotor 4.
[0017]
Inside the rotor 4, a centrifugal separator 7 for centrifuging the dispersed media flowing through the flow path 6 from the dispersed paste is disposed. In the illustrated example, the centrifugal separator 7 employs an impeller 8 disposed so as to cross the flow path 6. In order to send out the centrifugally dispersed dispersion media to the annular gap X, a circulation opening 9 is formed in the rotor 4 to communicate the surrounding space of the impeller 8 with the annular gap X.
[0018]
The impeller 8 can employ various blades such as a flat blade, an arrow blade, and a twisted blade, and has a function of sucking up at the center of the blade and pushing it out in the circumferential direction, that is, a function of a centrifugal pump. The rotational drive shaft 8 a of the impeller 8 is inserted into the hollow portion 4 x of the rotor 4 and protrudes from the rotational drive shaft 4 a of the rotor 4. In the figure, reference numerals 10, 11, and 12 denote seal members.
[0019]
The rotary drive shafts 4a and 8a are connected to a common drive source M via a transmission mechanism 15 in the illustrated example, but the drive sources of the rotary drive shafts 4a and 8a are connected to separate drive sources. Also good. In the illustrated example, the transmission mechanism 15 is a transmission mechanism including a combination of pulleys 15a to 15d and pulley belts 15e and 15f wound around the pulleys 15a to 15d. However, other known transmission mechanisms such as a gear transmission mechanism are employed. be able to.
[0020]
The flow path 6 communicates from the bottom of the rotor 4 to the center of the impeller 8, that is, the portion that performs the suction action of the impeller 8. The annular gap X, the flow path 6 and the circulation opening 9 constitute a circulation path that leads from the annular gap X to the center of the impeller 8 and through the outer periphery of the impeller 8 to the annular gap X again. .
[0021]
The stator 20 can be fixed substantially at the center of the inner bottom portion of the vessel 3, and a flow path is formed by a gap formed between the stator 20 and the rotor 4. The stator 20 is shaped so as to form a flow path in the central portion where the suction action caused by the rotation of the impeller 8 is strongest, thereby further enhancing the circulation of the dispersion medium and the dispersion paste in the circulation path. The stator 20 gives a speed difference by a gap between the inner side of the rotor 4 and the outer wall of the stator 20, and also plays a role of dispersing similarly to the outer periphery of the rotor 4. In the illustrated example, the stator 20 is formed of a cylindrical body having a truncated cone at the top, but various shapes such as a conical shape can be adopted.
[0022]
Jackets 30 and 31 are formed on the outer peripheral portions of the vessel 3 and the stator 20. Cooling water is introduced into the jackets 30 and 31 from a water supply port (not shown) and drained from a water discharge port (not shown). The temperature inside is prevented from rising.
[0023]
The geometric dimension ratio of the bead mill 1 is as follows:
The inner height H1 of the vessel 3 is 1.0 to 2.0.
The outer diameter L1 of the stator 20 is 0.5 to 0.7.
The outer diameter L2 of the rotor 4 is 0.95 to 0.98.
The width X1 of the annular gap X is 0.02 to 0.05.
The gap X2 between the rotor 4 and the stator 20 is 0.02 to 0.05.
The diameter L3 of the flow path 6 at the part communicating with the impeller 8 is 0.1 to 0.3.
The diameter L4 of the impeller 8 is 0.6 to 0.8.
The width H2 of the impeller 8 is 0.2 to 0.3.
An inner diameter L5 of the rotary drive shaft 4a of the rotor 4 is 0.3 to 0.4.
The height H3 of the circulation opening 9 is 0.25 to 0.35.
The width L6 of the circulation opening 9 is 0.05 to 0.1.
It is preferable that it exists in the range.
[0024]
Further, the rotational speed of the impeller 8 is preferably in the range of 1.5 to 2.0 times the rotational speed of the rotor 4.
[0025]
The effects of the bead mill having the above configuration will be described below.
[0026]
The pre-kneaded paste to be dispersed (preliminary mixture of pigment, varnish, and solvent) is pumped into the vessel 3 from the supply port 2 by a pump action outside the figure. A dispersion medium (not shown) is accommodated in the vessel 3 in advance. The feed amount for feeding the pre-kneaded paste to the supply port 2 is appropriately controlled within a range that does not significantly exceed the centrifugal separation ability of the impeller 8 constituting the centrifugal separator.
[0027]
The pre-kneaded paste that has been fed to the vessel 3 is agitated by the rotor 4 together with the dispersed media, and is sent downward through the annular gap X between the inner wall of the vessel 3 and the outer wall of the rotor 4, and passes through the gap between the bottom of the rotor 4 and the bottom of the vessel 3. Thus, the gap between the inner wall of the rotor 4 and the outer wall of the stator 20 is raised. The air is sucked into the impeller 8 from the center of the rotor 4 by the centrifugal pump action of the impeller 8 disposed inside the rotor 4.
[0028]
The mixture of the dispersed paste and dispersed media sucked into the impeller 8 is subjected to the centrifugal force due to the rotation of the impeller 8 and the rotor 4 outside thereof, and is separated into dispersed media and dispersed paste due to the difference in specific gravity. Dispersed media having a large specific gravity is discharged to the outer peripheral portion and returned to the annular gap X between the inner wall of the vessel 3 and the outer wall of the rotor 4 through a plurality of circulation openings 9 formed in the rotor 4. And it mixes with the pre-kneading paste again, and descend | falls the cyclic | annular clearance gap X between the inner wall of the vessel 3 and the rotor 4 outer wall.
[0029]
In this way, the dispersion media moves from the annular gap X to the flow path 6 inside the rotor by the flow of the dispersion paste, and repeats the circulation returning to the original through the circulation opening 9 by the impeller 8. During this time, the aggregated particles (secondary particles) of the pigment blended in the paste are converted into primary particles by a strong shearing action caused by collision with the dispersed media in the annular gap X between the inner wall of the vessel 3 and the outer wall of the rotor 4. Distributed.
[0030]
The dispersion paste separated from the dispersion media by the impeller 8 rises in the gap between the hollow portion 4x of the rotational drive shaft 4a of the rotor 4 and the rotational drive shaft 8a of the impeller 8, and the rotational drive shaft 4a of the rotor 4 It is discharged from the discharge port 3a through the discharge opening 5 formed in the above.
[0031]
Thus, the dispersed paste and the dispersed media are separated by the specific gravity difference between the dispersed media and the dispersed paste by the action of the strong centrifugal force generated by the rotation of the rotor 4 and the impeller 8 built in the rotor 4. Therefore, unlike the gap separator or the screen, a clearance that is a fraction of the particle size of the dispersed media is not required, and a dispersed media having a smaller diameter can be used.
[0032]
Further, since the dispersion media passes through the circulation path by the pumping action of the impeller 8, no flow resistance of the dispersion paste due to the dispersion media occurs.
[0033]
The above-described embodiment is an example of a bead mill according to the present invention, and there can be various modifications as described below.
[0034]
Although only one stage is shown in the above embodiment, the impeller 8 may be provided in two or more stages, and stationary guide vanes may be provided around the impeller 8 to form turbine blades. Further, as the centrifugal separator 7, a rotating disk (not shown) can be employed instead of the impeller 8. In the case of the rotating disk, the action as a suction pump is smaller than that of the impeller, but there is a function of applying centrifugal force to the dispersion media. In addition, the rotating body having various shapes that can centrifuge the dispersion media by rotating, such as a sphere, an elliptical sphere, and a shade, can also be adopted.
[0035]
In addition, as a centrifugal separator, it is also possible to fix or integrally form an impeller in the rotor 4 and omit the rotational drive shaft of the impeller. In this case, the rotational speed (rotational speed) of the impeller and the rotational speed of the rotor become the same, and the centrifugal separation action is reduced, but the number of parts can be reduced.
[0036]
Further, the rotor 4 can be provided with protrusions such as a plurality of pins on the outer peripheral surface to enhance the stirring effect.
[0037]
Furthermore, the rotational drive shaft 8a of the impeller 8 can be extended downward so as to protrude from the bottom of the vessel 3.
[0038]
Moreover, you may combine the bead mill 1 with a preparation tank, a pre-kneading circulation tank, etc.
[0039]
【Example】
A bead mill (implementing apparatus) equivalent to that shown in FIG. 1 was prepared, and a comparative experiment with a commercially available bead mill (conventional apparatus) was performed. The outline of the apparatus is as follows.
Execution device Rotor 4: outer diameter 140 mm x height 150 mm
Impeller 8: outer diameter 75mm x height 20mm
Bethel 3: Inner diameter 150 mm x Height 170 mm
Output of drive motor M: 2.2kW
Number of rotations of rotor 4: 1500 rpm
Speed of impeller 8: 2500 rpm
Dispersed media: zirconia, diameter 0.1 mm, specific gravity 6.0
Conventional apparatus The conventional apparatus used was a commercially available annular bead mill having the same size and motor output as the apparatus of the present invention. The dispersion media of the conventional apparatus is 0.5 mm in diameter and the material is zirconia.
[0040]
The above two types of bead mills were filled with 1.5 kg of dispersed media, and a paint pigment paste having a viscosity of 0.5 Pa · s was dispersed. As shown in FIG. 3, the tank 50 with a stirrer and the bead mill 1 are connected by a pipe 51 and a pump 52 at a processing flow rate of 500 kg / h and circulated and dispersed, whereby the residence time and dispersity (haze value) in the bead mill are Sought a relationship. The haze value was measured with a haze meter in accordance with JIS K 7105. The residence time is the time required for the dispersion paste to be discharged after being supplied to the bead mill, and can be expressed by the following equation.
[0041]
Residence time = {(bead mill space capacity) / (processing flow rate)} × number of passes Here, the bead mill space capacity is a value obtained by subtracting the volume of the filled beads from the volume of the bead mill. The number of passes is the number of times the dispersed paste passes through the bead mill, and the residence time per pass is obtained by measuring the processing flow rate of the dispersed paste. When the dispersion paste is passed through the bead mill a plurality of times, the residence time is calculated by integrating the number of passes.
[0042]
As a result of the comparative experiment, as shown in the graph of FIG. 4, it was found that the dispersion can be performed with a residence time of about 1/5 as compared with the conventional commercially available bead mill.
[0043]
In this way, the bead mill of the present invention has a significantly higher dispersion performance than the conventional bead mill. The impeller (centrifugation device) built in the rotor makes it possible to use a zirconia media having a diameter of 0.1 mm. It is considered that the media is well circulated between the outer peripheral portion (annular gap) and the inner peripheral portion of the rotor due to the pumping action of the impeller (centrifugal separator) and the movement of the media is promoted. .
[0044]
【The invention's effect】
As is clear from the above description, according to the bead mill according to the present invention, a flow path is formed from the annular gap formed at the outer periphery of the rotor and the inner periphery of the bethel to the inside of the rotor to the outlet of the bethel. Since a centrifugal separator is provided in the middle of the flow path, the dispersed media is centrifuged from the dispersed paste, and the dispersed dispersed media is sent to the annular gap from the circulation opening formed in the rotor. Fine particle size dispersion media can be used without clogging with pigments or wear due to dispersion media, resulting in improved dispersion performance.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a preferred embodiment of a bead mill according to the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is a conceptual diagram showing an experimental apparatus used in a comparative experiment between a bead mill according to the present invention and a conventional bead mill.
4 is a graph showing an experimental result by the experimental apparatus of FIG. 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bead mill 2 Supply port 3 Bethel 4 Rotor 5 Discharge opening 6 Flow path 7 Centrifugal device 8 Impeller 9 Circulation opening 20 Stator

Claims (7)

Arranged in the vessel so as to form an annular gap for dispersion between the vessel having a supply port for supplying the paste to be dispersed and a discharge port for discharging the dispersed paste, and the inner wall of the vessel. An annular bead mill having an outer peripheral surface having a cylindrical rotor,
A flow path is formed from the annular gap through the rotor to the discharge port,
A centrifuge for centrifuging the dispersed media from the dispersed paste is provided in the middle of the flow path in the rotor,
A bead mill characterized in that an opening for circulation is formed in the rotor for delivering the centrifuged dispersion media to the annular gap. The bead mill according to claim 1, wherein the centrifugal separator has a rotating body that performs centrifugal separation of a dispersed media, and the rotating body is an impeller. The bead mill according to claim 1, wherein the centrifugal separator has a rotating body that performs centrifugal separation of a dispersed media, and the rotating body is a rotating disk. The bead mill according to any one of claims 1 to 3, wherein a rotational drive shaft of the rotor is a hollow shaft, and a discharge opening that communicates with the discharge port is formed in the hollow shaft. The supply port is disposed on one end side of the vessel, further includes a substantially cylindrical stator disposed on the other end side of the vessel and on the inner side of the rotor, and between the stator and the rotor. The bead mill according to any one of claims 1 to 4, wherein a gap constituting a part of the flow path is formed. A rotary drive shaft of the rotor is inserted into the hollow shaft of the rotor, and a flow path reaching the discharge opening is formed between the hollow shaft inner peripheral wall of the rotor and the rotary drive shaft of the rotor. The bead mill according to claim 4, wherein a gap is formed. The bead mill according to claim 6, wherein the rotation drive shaft of the rotor and the rotation drive shaft of the rotating body are arranged concentrically.

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