JP2006007128A - Annular type bead mill, pigment dispersion system provided with it and pigment dispersion method using the system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an annular type bead mill for pigment dispersion for which dispersion media with a very small particle size can be used without causing a clogging problem of the media and for which the washing time can be shortened. <P>SOLUTION: The bead mill has a cylindrical vessel 2 provided with a supply passage 4, and a discharge passage 5, for pigment paste and having a peripheral wall and both side-walls; a cylindrical rotor 3 housed in the vessel 2 and arranged so as to form an annular gap for pigment dispersion between the peripheral wall of the vessel and the rotor 3 itself, and forming a opening 3a for circulation, through which the dispersion media can pass, through the peripheral wall of the rotor 3; and a separating screen 10 placed in the rotor 3 and supported by a first rotating and driving shaft 11 penetrating the one side wall of the vessel 2. The discharge passage 5 is formed in the first rotating and driving shaft 11 which communicates to the inside of the separating screen 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an annular type bead mill having a cylindrical rotor, and in particular, it is composed of pigments, that is, secondary particles, which are blended (premixed) in a paste to be dispersed, particularly in a dispersion process of paint and ink. The present invention relates to a bead mill for obtaining a dispersed paste in which pigment aggregates are pulverized into primary particles and dispersed in the paste to uniformly disperse the pigment.

  In a conventional bead mill, a gap separator or a separation screen has been known for a long time as a mechanism for separating a pigment paste obtained by dispersing a pigment and a dispersed media (so-called beads).

In addition, an annular bead mill is known in which a centrifugal blade is provided in place of the gap separator and the separation screen, and the dispersion media is separated from the discharge path by the centrifugal blade (see, for example, Patent Document 1).
JP 2002-306940 A

In recent years, there has been an increasing demand for finer pigment dispersion. In order to obtain a finer pigment dispersion, a method of reducing the particle size of the dispersed media contained in the bead mill and a method of circulating the bead mill with a stirrer to increase the circulation flow rate can be considered.
However, the conventional bead mill using only the separation screen or only the gap separator has a limit in reducing the particle size of the dispersed media.

  That is, in the gap separator that separates the pigment paste and the dispersion media by the clearance between the rotor and the stator fixed to the vessel, the rotation axis of the rotor 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 pigment pastes such as paints and inks having a relatively high viscosity, if the clearance between the rotor and the stator of the gap separator is reduced, the pressure loss increases, so a media with a diameter of 0.5 mm is the use limit.

  In addition, the separation screen has a larger opening area (total area) than the gap separator, but since the flow of liquid is worse than the gap separator, the clearance is limited to about 0.1 mm, and the diameter is 0.3 mm. The dispersion media is the limit. In particular, a pigment paste having a large structural viscosity has a drawback that the pressure loss is increased. Furthermore, the problem of clogging due to the dispersed pigment is likely to occur.

  Further, when the conventional bead mill is connected to the stirrer in a circulating manner, there is a problem that if the circulating flow rate is increased, the separation screen and the gap separator are clogged. Further, there is a problem that the clogging occurs when the viscosity of the dispersion paste is high even if the circulation flow rate is small.

  On the other hand, there is known an annular bead mill that solves the above-mentioned problems by adopting a centrifugal separator instead of a separation screen and a gap separator (see Patent Document 1). After cleaning, the cleaning time was long, and there was a slight problem with cleaning performance.

  That is, in the annular type bead mill employing the conventional centrifugal separator, as shown in FIG. 7, the pigment paste dispersed in the vessel 40 is fed from the upper part of the rotary blade body constituting the centrifugal separator 41 to the rotor 42. Through the gap G1 between the inner wall of the hollow rotary shaft 42a and the rotary drive shaft 41a, through the through hole 42b formed in the hollow rotary shaft 42a, and further through the gap G2 between the hollow rotary shaft 42a and the outer tube 43. To the discharge path 44.

  In general, in this type of bead mill, cleaning is performed through a cleaning liquid or cleaning water for each color change. In the conventional bead mill having such a configuration, the gaps G1 and G2, particularly the upper portions of the through holes 42a in the gap G1, and G2 The clearance at the upper part of the discharge passage 44 is not easily cleaned by the cleaning liquid or the cleaning water, and it is technically difficult to eliminate this clearance structurally.

  Therefore, an object of the present invention is to provide an annular type bead mill for pigment dispersion that can use a dispersion medium having a small particle size without causing clogging due to the dispersion medium, and that can shorten the washing time.

  Another object of the present invention is to provide a pigment dispersion system and a dispersion method that enable circulation and dispersion at a high flow rate even for a highly viscous pigment paste by circulatingly connecting such a bead mill to a stirrer.

  The object of the present invention is to disperse the pigment between the supply path and the discharge path of the pigment paste, the cylindrical vessel having a peripheral wall and both side walls, and the peripheral wall of the vessel that is accommodated in the vessel. A cylindrical rotor arranged to form an annular gap of the rotor, the rotor having a circulation opening through which a dispersed media can pass on the peripheral wall of the rotor, and the rotor arranged in the rotor A separation screen supported by a first rotary drive shaft that passes through one side wall of the vessel, and the discharge passage communicating with the interior of the separation screen is formed in the first rotary drive shaft. It is achieved by an annular type bead mill characterized in that

The rotor may be supported by a second rotational drive shaft that penetrates the other side wall of the becel. In this case, it is preferable that a centrifugal blade arranged so as to surround the separation screen be supported by the first rotation drive shaft.
The rotor may be fixed to the first rotational drive shaft. In this case, it is preferable that the centrifugal blade disposed so as to surround the separation screen be supported by a third rotational drive shaft that penetrates the other side wall of the vessel.
The above-mentioned object of the present invention can also be achieved by a pigment dispersion system characterized in that the bead mill and a stirrer having a flat paddle blade inside are connected by a circulation line via a circulation pump. The flat paddle wing includes a bottom flat paddle wing extending laterally from the bottom of the rotating shaft, and a rectangular upper flat paddle wing extending upward from both upper ends of the bottom flat paddle wing. It is preferable to have.

  The object of the present invention is a pigment dispersion method using the pigment dispersion treatment system, wherein a dispersion medium having a particle size of 0.1 to 0.3 mm is accommodated in the bead mill having a capacity of 3 to 10 liters, This is achieved by a pigment dispersion method characterized in that a pigment paste having a viscosity of 0.3 to 10 Pa · s is dispersed at a circulation flow rate of 600 to 3000 kg / hour according to the bead mill capacity.

  According to the present invention, by rotating the separation screen, the dispersion media in the pigment paste around the separation screen acts so as to be separated from the separation screen by centrifugal force, so that only the conventional separation screen and the gap separator are used. Compared with the conventional bead mill, even a dispersed media having a smaller diameter is not clogged, and the portion where it is difficult for the cleaning water or cleaning liquid to reach as in the prior art can be eliminated, so that the cleaning performance is improved.

  Moreover, by providing the centrifugal blade surrounding the periphery of the separation screen, the centrifugal force is increased and the separation action of the dispersed media from the separation screen is increased.

  Furthermore, even when connected to the stirrer in a circulating manner, the centrifugal force of the separation screen enables continuous operation without clogging the dispersion media with the separation screen even if the circulation flow rate is increased.

  A preferred embodiment of a bead mill according to the present invention will be described below with reference to the drawings. Throughout the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

  First, a first embodiment of a bead mill according to the present invention will be described with reference to FIGS. 1 and 2. 1 is a longitudinal sectional view of the bead mill, and FIG. 2 is a sectional view taken along the line II-II in FIG.

  As shown in FIG. 1, the bead mill 1 includes a cylindrical vessel 2 whose center line is oriented in the horizontal direction, and a cylindrical rotor 3 is housed in the vessel 2. In the vessel 2, a supply path 4 for supplying a paste to be dispersed is formed in the upper part of the peripheral wall, and a discharge path 5 for discharging the dispersed pigment paste is formed in the side wall.

  An annular gap X is formed between the inner peripheral wall of the vessel 2 and the outer peripheral wall of the rotor 3 for dispersing the pigment in the paste. The rotor 3 is rotatably supported at one end side by a second rotation drive shaft 6 extending in the horizontal direction. The second rotary drive shaft 6 penetrates the other side wall of the vessel 2 and is supported by a mechanical seal or shaft seal 7 and a bearing 8. A pulley 9 is attached to the tip of the second rotary drive shaft 6 and is connected to a drive motor (not shown) with a belt.

  The rotor 3 has an opening at the other end, and a separation screen 10 is inserted from the opening. A circulation opening 3a through which the dispersion media can pass is formed on the peripheral wall of the rotor 3, and the circulation opening 3a is formed by a plurality of slits extending in parallel in the horizontal direction in the illustrated example.

  The separation screen 10 disposed inside the rotor 3 is supported by a first rotation drive shaft 11 extending in the horizontal direction. The first rotary drive shaft 11 passes through one side wall of the vessel 2 and is supported by a shaft seal 12 and a bearing 13. A discharge path 5 communicating with the inside of the separation screen 10 is formed in the first rotation drive shaft 11. A pulley 14 is attached to the first rotation drive shaft 11, and the pulley 14 is belt-connected to a drive motor (not shown). A rotary joint 15 is attached to the first rotary drive shaft 11, and the outlet of the discharge path 5 is directed in a certain direction by the rotary joint 15.

A gap Y is formed between one side wall of the vessel 2 and the opening end of the rotor 3, and a flow path through which the pigment paste passes from the annular gap X to the separation screen 10 is formed by the gap Y.
A cooling liquid circulation path 2 a is formed in the vessel 2, and a cooling liquid such as cooling water is introduced into the cooling liquid circulation path 2 a from the cooling liquid supply part 2 b, and is discharged from the cooling liquid discharge part 2 c. The temperature rise is prevented.

  The effect of the bead mill having the above configuration will be described below.

  The pigment paste (preliminary mixture of pigment, varnish, and solvent) to be dispersed is stirred by a stirrer (not shown) and then pumped into the vessel 2 from the supply path 4 by a pump action (not shown). A dispersion medium (not shown) is accommodated in advance in the vessel 2 of the bead mill 1.

  Due to the pumping action of sending the pigment paste to the bead mill 1, the pigment paste supplied from the supply path 4 passes through the annular gap X, the gap Y and the inside of the rotor 3, and is discharged from the discharge path 5 through the separation screen 10. .

The pigment paste is stirred together with the dispersed media by the rotation of the rotor 3 from the annular gap X to the separation screen 10, and the aggregate of pigment is dispersed into primary particles by the dispersed media. The rotational speed of the rotor 3 can be about 1000-1600 rpm.
Further, when the separation screen 10 is driven to rotate, a rotational flow is generated around the separation screen 10, and centrifugal force is applied to the dispersion media having a large specific gravity (specific gravity of 6.0 for zirconia media) by the rotational flow. Move the media away from the separation screen 10. The dispersed media receiving the centrifugal force further passes through the circulation gap 3a of the rotor 3 and is returned to the annular gap X, and this is repeated and circulated. On the other hand, since the pigment paste is pumped by the pump, it is discharged from the discharge path 5 through the separation screen 10. The rotation speed of the separation screen 10 can be about 1600 to 2000 rpm.

  The centrifuge function prevents the dispersed media from clogging the separation screen 10. For this reason, it is possible to use a small-diameter dispersion medium having a diameter of 0.1 mm using the separation screen 10 having a clearance of 0.1 mm. By using such a small diameter dispersion media, fine pigment dispersion that could not be achieved conventionally can be achieved.

  Further, even when the dispersion paste has a high viscosity of, for example, about 5 Pa · s, the dispersion media is separated from the separation screen 10 by the centrifugal separation action, so that the dispersion screen 10 is dispersed without clogging. be able to.

  As described above, the dispersion media moves from the annular gap X to the separation screen 10 along with the flow of the pigment paste, and repeats circulation that returns to the original state through the circulation opening 3a by the rotary blade 10b by the separation screen. During this time, the aggregated particles (secondary particles) of the pigment blended in the paste are dispersed into the primary particles by the shearing action caused by the collision with the dispersion media in the annular gap X between the inner wall of the vessel 2 and the outer wall of the rotor 3. The

  The bead mill 1 having the above-described configuration is cleaned by press-fitting the cleaning liquid or cleaning water from the supply path 4 and discharging it from the discharge path. The cleaning liquid or cleaning water has the conventional gaps G1 and G2 (see FIG. 7). Since it does not pass through, it is possible to eliminate the portion where the cleaning liquid is not sufficiently reached, and the cleaning performance is improved.

  Next, 2nd Embodiment of the bead mill which concerns on this invention is described with reference to FIG.3 and FIG.4. FIG. 3 is a longitudinal sectional view of the bead mill, and FIG. 4 is a sectional view taken along the line IV-IV in FIG.

  The bead mill of the second embodiment is different from the first embodiment in that it includes a centrifugal blade surrounding the separation screen, and the other configurations are the same.

In the illustrated example, the centrifugal blade 20 is fixed to the first rotary drive shaft 11, but it may be fixed to both end fittings 10 a of the separation screen 10.
As shown in FIG. 4, the centrifugal blade 20 can be configured by forming a horizontally long slit 20 a in an oblique radial direction in a cylindrical portion surrounding the separation screen 10. The centrifugal blade 20 can employ various rotating blades such as a flat blade, an arrow blade, and a twisted blade, and has a function of sucking in the central part of the blade and pushing it in the circumferential direction, that is, a function of a centrifugal pump. Of course, the centrifugal blade 20 may be formed not by forming a slit in the cylindrical portion but by attaching blade components individually. The distance between the blades of the centrifugal blade 20 is set to a width (for example, 2 to 3 mm) sufficient for the dispersion media to pass through.

  The centrifugal blade 20 applies a centrifugal force to a dispersion media (not shown) sent together with the pigment paste from the annular gap X into the rotor 3. Therefore, when the centrifugal action of the centrifugal blade 20 is added to the centrifugal action of the separation screen 10, the centrifugal action of the dispersed media is further promoted.

  Next, a third embodiment of the bead mill according to the present invention will be described with reference to FIG. FIG. 5 shows a longitudinal sectional view of the bead mill of the third embodiment.

  In the bead mill of the third embodiment, the rotor 3 is fixed to the first rotation drive shaft 11, and the centrifugal blade 20 is supported by the third rotation drive shaft 25 penetrating the other side wall of the bethel 3. Is different from the second embodiment in that it is changed to one side wall side, and the other configuration is the same as that of the second embodiment.

  Next, a preferred embodiment of the pigment dispersion system according to the present invention will be described. The bead mill according to the present invention can exhibit a higher dispersion effect by using a pigment dispersion system that is circulated and connected via a stirrer and a circulation pump. Hereinafter, the pigment dispersion system will be described with reference to FIG.

  In the pigment dispersion system, as shown in FIG. 6, the bead mill 1 is circulated and connected to a stirrer 32 through a circulation pipe 31 via a circulation pump 30. The bead mill 1 uses the same thing as the said embodiment.

  The stirrer 32 has a processing liquid supply path 33 at the top and a processing liquid outlet 34 at the bottom and a cylindrical periphery of the stirring tank 35, a rotating shaft 36 suspended in the stirring tank 35, and a rotating shaft And a flat paddle blade 37 attached to 36. The processing liquid supply path 33 is connected to the discharge path 5 of the bead mill 1, and the processing liquid outlet 34 is connected to the supply path 4 of the bead mill 1.

  The flat paddle blade 37 includes a bottom flat paddle blade portion 37a that extends laterally from the bottom portion of the rotating shaft 36, and a rectangular upper flat paddle blade portion 37b that extends upward from the upper portions on both sides of the bottom flat paddle blade portion 37a. And have.

  The stirrer 32 has a dimensional ratio (b / a) between the inner diameter (a) of the stirring tank and the blade diameter (b) of the bottom flat paddle blade portion 37a in the range of 0.6 to 0.9, preferably 0.6 to 0.00. It is designed to be within the range of 8. When the dimensional ratio (b / a) is less than 0.6, the blade diameter is too small compared to the inner diameter of the stirring tank 35, so that the pigment paste stays on the tank wall surface, while the dimensional ratio (b / a) This is because if a) exceeds 0.9, the blade diameter becomes too large compared to the inner diameter of the agitation tank 35, so that a short circuit of the pigment paste is likely to occur.

  The flat paddle blade 4 has a dimensional ratio (d / c) between the height (c) of the bottom flat paddle blade portion 37a and the height (d) of the upper flat paddle blade portion 37b, preferably 1-4. It is designed within the range. When the dimensional ratio (d / c) of this height is less than 1, that is, the height (d) of the upper flat paddle wing 37b is too low as compared with the height (c) of the bottom flat paddle wing 37a. However, since the required power during stirring increases, there is a disadvantage that the cost of the product increases and short-circuiting of the pigment paste easily occurs. On the other hand, when the dimensional ratio (d / c) exceeds 4, that is, the upper flat surface. This is because if the height (d) of the paddle blade portion 37b is too high as compared with the height (c) of the bottom flat paddle blade portion 37a, there is a drawback that the pigment paste cannot be uniformly mixed in the tank.

  According to the pigment dispersion system having the above configuration, when a zirconia media having a diameter of 0.1 mm is used as the dispersion media, the viscosity of the pigment paste is about 0.3 to 10 Pa · s when the bead mill capacity is 3 liters. If present, it is preferable to disperse the circulating flow rate at about 600 to 900 kg / hour.

  When a dispersion media having a particle size of 0.1 to 0.3 mm is used in the pigment dispersion system, the bead mill capacity is at most 10 liters, and the circulation flow rate of the pigment paste can be increased as the bead mill capacity increases. However, the circulation flow rate cannot be increased in a linear proportional relationship with the capacity of the bead mill because of the centrifugal separation capacity, the circulation pump capacity, etc., and the capacity of the bead mill containing 0.1 mm dispersion media. Is 10 liters, the circulation flow rate is preferably 1500 kg / hr to 3000 kg / hr for the pigment paste having the viscosity (0.3 to 10 Pa · s).

  The larger the circulation flow rate, the better. However, when the viscosity of the pigment paste exceeds 10 Pa · s, the load on the centrifugal separator 10 (see FIG. 1) and the circulation pump 30 increases due to viscous resistance. The circulation flow rate is preferably 600 kg / hour or more, and when the viscosity is less than 0.3 Pa · s, the load on the centrifugal separator 10 is taken into consideration, and 3000 kg / It is preferable to be less than the hour.

It is a longitudinal section showing a 1st embodiment of a bead mill concerning the present invention. It is II-II sectional drawing of FIG. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the bead mill which concerns on this invention. It is IV-IV sectional drawing of FIG. It is a longitudinal cross-sectional view which shows 3rd Embodiment of the bead mill which concerns on this invention. 1 is a system diagram schematically showing a preferred embodiment of a pigment dispersion system according to the present invention. The conventional bead mill is shown, (a) is a longitudinal cross-sectional view, (b) is IV-IV sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead mill 2 Bethel 3 Rotor 4 Supply path 5 Discharge path 6 2nd rotation drive shaft 11 1st rotation drive shaft 10 Separation screen 20 Centrifugal blade 32 Stirrer 37 Flat paddle blade 37a Bottom flat paddle blade 37b Upper flat paddle blade

Claims (8)

A cylindrical becel having a supply path and a discharge path for the pigment paste, and having a peripheral wall and both side walls;
A cylindrical rotor that is accommodated in the vessel and is arranged so as to form an annular gap for dispersing the pigment between the peripheral wall of the vessel and the circulation of the dispersed media through the peripheral wall of the rotor The rotor formed with an opening for use;
A separation screen disposed in the rotor and supported by a first rotary drive shaft penetrating one side wall of the vessel.
The annular bead mill characterized in that the discharge path communicating with the inside of the separation screen is formed inside the first rotary drive shaft. 2. The bead mill according to claim 1, wherein the rotor is supported by a second rotational drive shaft that penetrates the other side wall of the vessel. The annular bead mill according to claim 1, wherein a centrifugal blade arranged so as to surround the separation screen is supported by the first rotation drive shaft. The bead mill according to claim 1, wherein the rotor is fixed to the first rotation drive shaft. The bead mill according to claim 4, wherein a centrifugal blade disposed so as to surround the separation screen is supported by a third rotation drive shaft that penetrates the other side wall of the vessel. A pigment dispersion system, wherein the bead mill according to any one of claims 1 to 5 and a stirrer having a flat paddle blade therein are connected by a circulation line via a circulation pump. The flat paddle wing includes a bottom flat paddle wing extending laterally from the bottom of the rotating shaft, and a rectangular upper flat paddle wing extending upward from both upper ends of the bottom flat paddle wing. The pigment dispersion system according to claim 6, further comprising: A pigment dispersion method using the pigment dispersion treatment system according to claim 6 or 7, wherein a dispersion medium having a particle size of 0.1 to 0.3 mm is contained in the bead mill having a capacity of 3 to 10 liters, and a viscosity of 0 A pigment dispersion method, wherein a pigment paste of 3 to 10 Pa · s is dispersed at a circulation flow rate of 600 to 3000 kg / hour according to the bead mill capacity.

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