Note: Descriptions are shown in the official language in which they were submitted.
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AN AGITATOR, A CIRCULATORY CLEANING DEVICE ATTACHED TO THE
AGITATOR, AND A CIRCULATORY LINE SYS7.'EM COMPRISING THE
CIRCULATORY CLEANING DEVICE
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DESCRIPTION
An . agitator, a circulatory cleaning device
attached to the agitator, and a circulatory line system
comprising the circulatory cleaning device
TECHNICAL FIELD
The present invention relates to an agitator, a
circulatory cleaning device attached to the agitator, and
a circulatory line system comprising the circulatory
cleaning device.
BACKGROUND ART
Conventionally, coating compositions, inks and
like coloring licyuids are clear varnishes containing
pigment pastes. Pigment pastes are generally prepared by
the steps of mixing pigments, resins, organic solvents,
and like raw materials in an agitator to prepare a mill
base, and then passing this mill base a few times through
a bead mill dispersion apparatus or like continuous
dispersion apparatus to disperse the pigment.
Specifically, the commonly employed pigment
dispersion method comprises the steps of feeding an
unprocessed pigment paste stored in a feeding vessel to a
dispersion apparatus, temporarily storing the pigment
paste obtained by dispersing it in the dispersion
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apparatus in a receiving vessel, returning the pigment
paste stored in the receiving vessel to the dispersion
apparatus to redisperse it after the completion of the
first pigment dispersion process, anct returning the
pigment paste which has been subjected to the second
pigment dispersion process to the feeding vessel to store
it, and then repeating these processes a few times. The
above-mentioned manufacturing process, however,
disadvantageously requires two vesse7_s, i,e., feeding
vessel and receiving vessel, and operations to switch
between these vessels.
To overcome these disadvantages, a known
technique connects an agitator and a dispersion apparatus
via a circulation line to circulate pigment paste between
the apparatuses, unifying the feeding vessel and receiving
vessel (for example, refer to Japane:~e Unexamined Patent
Publication Nos. 1996-266880 and 2002-306940).
A known bead mill apparatu:> (cf. Japanese
Unexamined Patent Publication No. 1996-266880, Japanese
Examined Patent Publication No. 1994--28745 and Japanese
Unexamined Patent Publication No. 2002-204969) having a
mechanism which separates pigment pa:~te from a grinding
medium by the action of centrifugal i_orce caused by the
rotation of a rotor has such advantages that it has a
large throughput (flow rate); it requires only one vessel
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because it allows circulation dispersion; and it does not
require a switching operation between. a feeding vessel and
a receiving vessel because it has only one vessel.
However, even if a pigment is dispersed and
mixed by using the above-mentioned bead mill apparatus,
there is the disadvantage that insufficient agitating and
mixing in an agitator may cause mill base to short-path
when the pigment flows in and out around the agitator (for
example, anchor type, propeller type), and that the
efficiency of the pigment dispersion is lowered if there
is any pooling in the vessel. Here, "short-path° means
that fluid supplied in an agitator is discharged from the
agitator without fully being agitated..
Accordingly, to efficiently perform agitating
and mixing in the agitator, a double-shafted mixer having
a high-speed agitator and a low-speed anchor type
agitating blade which removes the pooled mill base off the
vessel wall was developed.
However, said double-shaft mixer has the problem
of high installation cost. In addition, since a small
interval between the vessel wall and anchor type agitating
blade makes cleaning the mill base by injecting a cleaning
solvent difficult, the mixer still has a problem in its
ability to be cleaned when the mixer is applied to the
production of coating compositions, which requires the
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frequent replacement of materials.
There are other known mixers, for example,
single shaft mixers, than the above-mentioned agitators
(for example, refer to Japanese Patent No. 3224498 and
Japanese Examined Patent Publication No. 1989-37173).
Although these agitators are suitable: for simply mixing a
fluid in a vessel homogenously, when they are used for
circulation dispersion systems which drive fluid drawn
from a lower part of the vessel from a return pipe
provided in an upper part of the vessel into the vessel,
and return the drawn fluid to the return pipe through a
dispersion apparatus, they have the following
disadvantage: as the circulating flow of the fluid in the
vessel becomes faster, the fluid provided by the return
pipe fails to be mixed and short-paths in the vessel
because it is instantaneously drawn from the lower part of
the vessel. Furthermore, it is less effective than an
anchor type agitating blade in drawing fluid off the inner
wall portion of the vessel in the agitator, mixing it, and
circulating it. Therefore, pigment paste with high
structural viscosity is likely to pool on the wall of the
vessel and thus is disadvantageously difficult to mix and
agitate.
To overcome the aforementioned problems, the
inventors of the present invention have previously
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improved the constitution of paddle blades and proposed an
agitator which can be applied to a c3.rculatory system with
a large flow rate, can deal with a variety of fluids,
changes in fluid volume, and has an excellent ability to
mix and disperse fluids with different viscosities ranging
from low to high and cleanability (refer to Japanese
Patent No. 3189047).
Moreover, the production of: caating compositions
and like coloring liquids is often in small batches of a
wide variety of products. Therefore, every time the color
is changed, the agitating vessel and other portions which
come in contact with the pigment paste need to be cleaned.
In a known cleaning step, for example, a cleaning device
ejects a cleaning liquid from a cleaning nozzle connected
to a cleaning liquid tank into the agitating vessel (for
example, refer to Japanese Patent No. 3189047). This
cleaning device showers the inner wall of the agitating
vessel and the surface of the agitating blade with the
cleaning liquid from the cleaning liquid tank via the
cleaning nozzle to wash away pigment paste deposited
therein. The cleaning liquid ejected from the cleaning
liquid nozzle into the agitating vessel is immediately
drawn out from the bottom of the agitating vessel,
collected and recycled.
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DISCLOSURE OF THE INVENTION
However, the heating generated by the friction
between the grinding medium and the rotor or vessel inside
a bead mill and the friction within the grinding medium is
greater than the cooling provided by the vessel of the
bead mill. Consequently, the temperai_ure of the pigment
paste increases. The pigment paste is sometimes
deteriorated by elevated temperatures, and therefore the
heat generated by the pigment paste becomes greater as its
viscosity increases.
Accordingly, a first object of the present
invention is to provide an agitator with further
improvements in its flat paddle blade, and an agitating
vessel with the improved agitator previously suggested by
the inventors of the present invention to mainly increase
the cooling efficiency of the agitator.
Moreover, although the aforementioned known
improved agitator previously proposed by the inventors of
the present invention is capable of cleaning the flat
2~ paddle blade and the inner wall of an agitating vessel by
circulating a cleaning liquid and has a much higher
cleanability than the aforementioned ltnown double-shaft
mixer because it employs a flat paddle blade, pigment
paste deposited on the outermost peripheral surface (flat
surface) of the flat paddle blade and the pigment paste
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deposited on the bottom of the agitating vessel are
sometimes a little difficult to scrape off.
In cleaning the aforementioned known improved
agitator, for example, a cleaning liquid is collected in
the agitating vessel, and then the flat paddle blade and
the inner wall of the agitating vessel is cleaned by
rotating the flat paddle blade backw<~rds and forwards. At
this time, the cleaning liquid simultaneously cleans the
inside of the bead mill apparatus by circulating through
10, the circulatory channel connecting the bead mill apparatus
and the agitator.
The inventors of the present invention have
conducted extensive research, and consequently found that
in the prior art, including the previously proposed
improved agitator, pigment paste deposited on the flat
surface around the agitating blade tends to pool during
circulation dispersion since the peripheral edge of the
agitating blade is a flat surface as shown in the cross
section of Fig. 8, which results in lowered dispersibility.
They also found that pigment paste readily adheres and
deposits on the flat surface of the agitating blade and
cannot be sufficiently cleaned by the cleaning liquid
ejected from the cleaning nozzle.
Moreover, the inventors of the present invention
have found that the flow of cleaning' liquid fed through a
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fluid inlet provided in an upper part of the agitating
vessel, discharged through a fluid outlet provided in the
bottom, and circulated inside the agitator and bead mill
apparatus through the circulatory channel of the bead mill
apparatus sometimes pools at the bottom of the agitating
vessel.
Therefore, a second object of the present
invention is to provide an agitator with increased
cleanability of a paddle blade and an agitating vessel of
the agitator.
Moreover, known cleaning devices which clean
agitating vessels and the like require a large amount of a
cleaning liquid for a sufficient level of cleaning to be
achieved.
Furthermore, if the agitator and dispersian
apparatus is connected with a pipe, to make sure that no
the cleaning liquid or the like is left when changing
colors, the pipe needs to be disassembled and its inside
cleaned. This requires a great deal of work and
significantly increases production costs.
Therefore, a third object of the present
invention is to provide a circulatory cleaning device
which can reduce the amount of a cleaning liquid used.
Further, a fourth object of the present
invention is to provide a circulatory line system which
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can reduce the amount of cleaning liquid used and the
labor required for cleaning in a system in which an
agitator and a dispersion apparatus are connected via a
pipe.
In order to achieve the aforementioned first
object, the agitator according to the: present invention
comprises an agitating vessel which bias a fluid inlet in
an upper part thereof , a fluid out7_et: at the bottom, and a
cylindrical circumferential configura~tionA a rotating
shaft extending vertically inside the; agitating vessel;
and a flat paddle blade mounted on said rotating shaft,
the flat paddle blade having a bottom flat paddle blade
portion which extends outwards from t:he bottom of the
rotating shaft, and oblong upper flat: paddle blade
portions extending upward from an upper part of each side
end of the bottom flat paddle blade portion, the
dimensional ratio (b/a) of the blade diameter (b) of the
bottom flat paddle blade portion to t:he inner diameter (a)
of the agitating vessel being in the range of from 0.6 to
0.9, the dimensional ratio (d/c) of t:he height (d) of the
upper flat paddle blade portion to tree height (c) of the
bottom flat paddle blade portion being in the range of
from 1 to 4, and a passage to pass a coolant medium
through the rotating shaft and the f7_at paddle blade.
It is preferable that the agitator further
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comprises a coolant jacket around the agitating vessel.
Moreover, to achieve the aforementioned second
object, the agitator according to the, present invention
has an agitating vessel comprising a fluid inlet in an
upper part thereof, a fluid outlet at. the bottom, and
having a cylindrical peripheral configuration; a rotating
shaft extending vertically inside the; agitating vessel;
and a flat paddle blade mounted on s2~id rotating shaft,
the flat paddle blade having a bottom flat paddle blade
portion which extends outwards from t:he bottom of the
rotating shaft and a oblong upper flat paddle blade
portion extending upward from an upper part of each side
end of the bottom flat paddle blade portion, the outermost
periphery of the flat paddle blade being tapered by two
inclined surfaces.
It is preferable that the outermost periphery of
the flat paddle blade has a V-shaped peripheral
configuration formed by the two inclined surfaces and each
of said inclined surfaces is formed ;so that the internal
angle (81) between a flat surface of the flat paddle blade
and the inclined surface is in the range of from 100°to
140° .
The bottom configuration o:f the agitating vessel
preferably is in the shape of a cone or a truncated cone
tapering downwards, and the bottom configuration of the
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bottom flat paddle blade portion is preferably formed
parallel with the bottom of the agitating vessel.
The bottom conical surface of the agitating
vessel preferably has an inclination so that the angle
(6z) of the surface is 5° -30° from horizontal.
The dimensional ratio (e/b) of the width (e) of
each upper flat paddle blade portion to the blade diameter
(b) of the bottom flat paddle blade portion is preferably
in the range of from 0.05 to 0.2.
Moreover, to achieve the third object of the
present invention, the circulatory cleaning device
according to the present invention is a circulatory
cleaning device attached to an agitator for agitating
pigment paste, the device comprising a cleaning liquid
tank storing a cleaning liquid; a first pump which
suctions a liquid in said cleaning liquid tank and feeds
the liquid into the agitating vessel; and a second pump
having a suction opening connected to~ an outlet provided
at the bottom of the agitating vessel., and a discharge
opening connected to an inlet of the cleaning liquid tank
by a circulatory cleaning pipeline.
In the circulatory cleanings device, a first
directional control valve, which further has a waste fluid
tank which receives cleaning waste fluid and switches so
that a liquid discharged from the second pump is
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discharged into the waste fluid tank, is preferably
provided in the circulatory cleaning pipeline.
In addition, to achieve the aforementioned
fourth object of the present invention, the circulation
dispersion system according to the present invention
comprises the above circulatory cleaning device; the above
agitator having an agitating blade and agitating vessel;
and a dispersion apparatus provided in the circulatory
cleaning pipeline for disaggregating pigment aggregates
comprising secondary particles into p~rirnary particles and
dispersing these primary particles in pigment paste, a
second directional control valve which switches so that
liquid discharged from the second pump is fed to the
dispersion apparatus, wherein an outlet of the dispersion
apparatus and a inlet of the agitating vessel are
connected by a pipeline for circulation dispersion,
The circulation dispersion system preferably has
a product tank in the pipeline for circulation dispersion
for receiving pigment paste which ha:> been subjected to
the above dispersion process, and a third directional
control valve which switches to disctaarge liquid
discharged from the second pump into the product tank .
The dispersican apparatus of the circulation
dispersion system is an annular bead mill which has a
vessel having an inlet which supplies pigment paste for
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dispersing and an outlet which discharges the dispersed
pigment paste; and a rotor having a cylindrical outer
peripheral surface and disposed inside the vessel to form
an annular gap for performing dispersion between itself
and the inner wall of the vessel. It is also preferable
that the annular gap comprises a passage through the
inside of the rotor to the outlet; that a centrifuge for
centrifuging a grinding medium from grinding
medium/pigment paste mixture in the passage inside the
rotor is provided; and that an opening for circulation for
discharging the centrifuged grinding medium into the
annular gap is provided in the rotor.
It is preferable that the centrifuge has a
rotary member which centrifuges the grinding medium and
said rotary member is ~n impeller or a rotational disk.
It is preferable that the rotational drive shaft
of the rotor is a hollow shaft and that an outlet
communicating with the outlet of the vessel is formed in
said hollow shaft. It is preferable that the inlet of the
vessel is disposed on one end of the vessel; an
approximately cylindrical stator is further disposed
approximately on the other end of the; vessel inside the
rotor; and that a gap constituting a part of the passage
is formed between said stator and the: rotor.
It is preferable that a rotational drive shaft
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of the rotary member is inserted into the hollow shaft of
the rotor and a gap constituting a passage leading to the
outlet opening is formed between inner circumferential
wall of the hollow shaft of the rotor and the rotational
drive shaft of the rotary member. It is preferable that
the rotational drive shaft of the rotor and the rotational
drive shaft of the rotary member are disposed
concentrically.
BRIEF DESCRIPTTON OF THE DRAWINGS
Fig. 1 is a longitudinal sectional view showing
one embodiment of an agitator according to the present
invention.
Fig. 2 is a longitudinal sE:ctional view showing
the inner structure of a component of the agitator of Fig.
1, a flat paddle blade, with partial omission.
Fig. 3 is a longitudinal sectional view showing
the agitator of Fig. 1.
Fig. 4 is a cross-sectional view taken along the
line A-A of Fig. 1.
Fig. 5 is a cross-sectional view taken along the
line B-B of Fig. 1.
Fig. 6 shows another form ~of a component of an
agitator according to the present invention, a flat paddle
blade, and is a cross-sectional view corresponding to the
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cross section taken along the line B-B of Fig. 1.
Fig. 7 is an illustrative drawing showing the
action of a component the agitator of Fig. 1, a flat
paddle blade.
Fig. 8 is a horizontal sectional view showing
how a prior art flat paddle blade is used.
Fig. 9 is a system drawing showing one
embodiment of the circulatory cleaning device according to
the present invention and a circulation dispersion system
comprising said circulatory cleaning device.
Fig. 10 is a longitudinal sectional view showing
a dispersion apparatus incorporated into the system of Fig.
9.
Fig. 1l is a cross-sectional view of Fig. 10 in
the plane of A-A.
BEST MODE FOR CARRYING OUT 'PHE INVENTION
A first embodiment of an agitator according to
the present invention will be described with reference to
Figs. 1 - 3 below. Fig. 1 is a longitudinal sectional
view showing the inner structure of the agitator, and Fig.
2 is a partial longitudinal sectional view showing the
inner structure of the flat paddle blade part of Fig. 1.
The agitator 1 has an agitating vessel 2; a
rotating shaft 3 extending vertically in the inner center
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of the agitating vessel 2; and a flat paddle blade 4 as an
agitating blade mounted on the rotating shaft 3.
The agitating vessel 2 comprises a fluid inlet 5
in an upper part thereof and a fluid outlet 6 at the
bottom. It has a cylindrical circumferential side face
and a coolant jacket 2a therearound.
The coolant jacket can be of a known
constitution, and allows a coolant medium such as a
coolant water to circulate inside. The configuration of
the bottom of the agitating vessel 2 is a truncated cone
with the narrow portion downwards. Moreover, the
agitating vessel 2 comprises cleaning liquid inlets 7, 7
in an upper part thereof.
The flat paddle blade 4 has a bottom flat paddle
blade portion 4a which extends outwards from the bottom of
the rotating shaft 3, and oblong upper flat paddle blade
portions 4b which extend upward from an upper part of each
side end of the bottom flat paddle blade portion 4a.
The bottom configuration of the bottom flat
paddle blade portion 4a is formed by inclined sides
parallel to the bottom conical surface of the agitating
vessel 2, and has a predetermined clearance between itself
and the bottom face of the agitating vessel 2.
Each upper flat paddle blade portion 4b is set
up symmetrically with respect to the rotating shaft 3.
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The rotating shaft 3 is ratationally driven by a drive 8
disposed external to the vessel via a. pulley 9, pulley
belt 10 and pulley 11, and the rotational drive of the
rotation shaft 3 causes the flat paddle blade 4 to pass
near the cylindrical inner wall face of the agitating
vessel 2 as it rotates.
In the rotating shaft 3 and flat paddle blade 4,
a passage 12 is formed to pass a coo7Lant medium through
the flat paddle blade 4 via the rotating shaft 3. The
passage 12 formed in the flat paddle blade 4 is preferably
formed in both the bottom flat paddle blade portion 4a and
upper flat paddle blade portion 4b. A coolant medium
which is cooled by a cooler (not shown) to -10°C to 10°C
can be used.
In the embodiment illustrated, the inner portion
of the rotating shaft 3 has a double pipe structure. The
coolant medium flows, as shown by the arrows in Fig. 2,
through the passage 12 formed inside the flat paddle blade
4, through the passage 12 formed by an inner pipe 3a, and
is then discharged via the passage 12 formed by an outer
pipe 3b of the double pipe. At the upper end of the
rotating shaft 3, a duplex rotary joint 13 corresponding
to the double pipe is mounted so that coolant medium can
be supplied and discharged from the upper end of the
rotating shaft even during rotation of the rotating shaft
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3.
As shown in Fig. 3, the bottom flat paddle blade
portion 4a is configured so that the dimensional ratio
(b/a) of the blade diameter b to the inner diameter a of
the agitating vessel 2 falls within t:he range of from 0.6
to 0.9, and preferably 0.6 to 0.8. If the dimensional
ratio (b/a) is lower than 0.6, the blade diameter is too
small compared to the inner diameter of the agitating
vessel 2 and therefore too much pigment paste pools at the
ZO vessel wall surface. On the other hand, if the
dimensional ratio (b/a) is higher than 0.9, the blade
diameter becomes too large compared to the inner diameter
of the agitating vessel 2, causing pigment paste to easily
short-path.
Moreover, the flat paddle blade 4 is designed so
that the dimensional ratio (d/c) of the height d of the
upper flat paddle blade portion 4b to the height c of the
bottom flat paddle blade portion 4a falls within the range
of from 1 to 4, and preferably from 1 to 3. If this
height dimensional ratio (d/c) is lower than 1, that is.
the height d of the upper flat paddle blade portion 4b is
too low relative to the height c of the bottom flat paddle
blade portion 4a, the driving force required for agitation
is too large. This may disadvantageously result in high
production costs, accelerated deterioration of machinery
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due to heavy loads, and increased chances of pigment paste
short-pathing. 0n the other hand, if the dimensional
ratio (d/c) is higher than 4, in other words, if the
height d of the upper flat paddle blade portion 4b becomes
too high relative to the height c of the bottom flat
paddle blade portion 4a, pigment paste disadvantageously
fails to be mixed homogenously in the vessel.
In addition, the flat paddle blade 4 is designed
so that the dimensional ratio (h/a) of overall height,
i.e., (d+c), of the flat paddle blade 4 to the inner
diameter a of the agitating vessel 2 falls within the
range of from 0.8 to 1.5, and preferably from 1.0 to 1.3.
If this dimensional ratio (h/a) of height is lower than
0.8, that is, if the overall height h of the flat paddle
blade 4 becomes too short relative to the inner diameter a
of the agitating vessel 2, pigment paste disadvantageously
tends to short-path. On the other hand, if the
dimensional ratio (hJa} is higher than I.5, that is, if
the overall height h of the flat paddle blade 4 becomes
too long relative to the inner diameter a of the agitating
vessel 2, pigment paste disadvantageously fails to be
mixed homogenously in the vessel.
The oblong upper flat paddle blade portion 4b is
a blade whose longest dimension is in the direction of
height, and its width a is preferably such that the
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dimensional ratio (e/b) of the blade width of the upper
flat paddle blade portion 4b to the diameter b of the
bottam flat paddle blade portion 4a falls within the range
of from 0.05 to 0.2, and preferably from 0.06 to 0.15. If
the dimensional ratio (e/b) is lower than 0.05, the effect
in removing pigment paste in the vicinity of the inner
vessel surface is reduced. On the other hand, if it is
higher than 0.2, pigment paste tends to short-path.
Moreover, the dimensional ratio (c/b) of the
height c of the bottom flat paddle blade portion 4a to the
blade diameter b of the same is preferably from 0.4 to 1.0,
and more preferably from 0.5 to 0.7. If the dimensional
ratio (c/b) is lower than 0.4, the agitating effect is
lowered. On the other hand, if the dimensional ratio
(c/b) is higher than 1.0, the load applied to the
apparatus is too large, which accelerates deterioration.
The flat paddle blade 4 is preferably
constituted by a single piece. Moreover, the materials)
constituting the flat paddle blade ~ are not limited and
materials which have been used for prior art agitating
blades may be used. Stainless steel is especially
preferable from the aspect of durability and strength.
From the aspect of cleanability, it is preferable that the
surface is mirror finished or a Teflon~ coating or glass
lining is applied to the surface. It shauld be noted that
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when the capacity of the agitating vessel 2 is 500 liters,
the thickness of the flat paddle blade 4 is 10-30 mm.
The capacity of the agitating vessel 2 is not
particularly limited, but in general ranges from about 2
liters to about 10000 liters.
According to a second embodiment of the present
invention, the flat paddle blade 4 has, as shown in the
cross sectional configurations of Figs. 4 and 5, a
peripheral portion which is entirely tapered by inclined
surfaces 4c, 4c formed two sides and has a V-shaped cross
sectional configuration. In the examples shown in Figs. 4
and 5, the inclined surfaces 4c, 4c are flat surfaces, but
they can also be formed by curving faces as shown in the
cross-sectional view of Fig. 6. Moreover, the tip tapered
by the inclined surfaces 4c, 4c, is illustrated as a sharp
point in the examples shown in Figs. 4 and 5, but can be,
for example, of rounded U-shaped cross sectional
configuration shown in Fig. 6. It should be noted that
the cross sectional configuration of only the upper flat
paddle blade portion 4b is shown in Figs. 4-6, but the
case for the bottom flat paddle blade portion 4a is also
the same.
The agitators of the aforementioned first and
second embodiments are mainly used incorporated into a
circulation dispersion system connected to a dispersion
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apparatus.
A suitable embodiment of such a circulation
dispersion system will be described with reference to Figs.
9-11 below. It should be noted that in Fig. 9, the
circulation dispersion system 100 comprising the agitator
1, a circulatory cleaning device 80 connected to the
agitator 1 by a circulatory cleaning pipeline, and a
dispersion apparatus 15 connected to the agitator 1 by a
circulation dispersion pipeline l6, and will be described
as an example of this embodiment.
The circulatory cleaning device 80 has a
cleaning liquid tank 20 for storing .a cleaning liquid such
as water and solvent; a first pump 24 which suctions the
cleaning liquid from the cleaning liquid tank 20 and
provides cleaning liquid inlets 21a, 21a of the agitating
vessel 2 with the liquid therein; and a second pump 14
whose suction opening is connected to a fluid outlet 6
provided at the bottom of the agitating vessel 2 and whose
discharge opening is connected to a cleaning liquid inlet
20a of the cleaning liquid tank 20 by a circulatory
cleaning pipeline 22.
The cleaning nozzle 21 of the agitating vessel 2
comprises cleaning liquid inlets 21a, 21a, and a cleaning
liquid pumped out from the first pump 24 is ejected via
the cleaning nozzle 21 at high pressure like a shower at
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the agitating vessel 2 and the flat paddle blade 4 as an
agitating blade.
The cleaning liquid collected in the agitating
vessel 2 is drawn out from the fluid outlet 6 of the
agitating vessel 2 by the second pump 14, and is returned
to the cleaning liquid tank 20 via the circulatory
cleaning pipeline 22.
The circulatory cleaning device 80 further has a
waste fluid tank 25 which receives cleaning waste fluid,
and a first directional control valve 23, which switches
so that the liquid discharged from the second pump 14 is
discharged into the waste fluid tank 25, is provided in
the circulatory cleaning pipeline 22.
A second directional control valve 17 is further
provided in the circulatory cleaning pipeline 22. The
second directional control valve 17 is capable of
switching so that liquid discharged from the second pump
14 is fed to the dispersion apparatus 15. The outlet of
the dispersion apparatus 15 is connected to a fluid inlet
5 of the agitating vessel 2 by a pipeline for circulation
dispersion 16.
A third directional control valve 18 is provided
in the pipeline for circulation dispersion 16. The third
directional control valve 18 is capable of switching so
that liquid discharged from the second pump 14 is
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discharged into a product tank 19. The product tank 19
receives pigment paste Which has been subjected to the
dispersion process.
There is no particular limitation on the
dispersion apparatus 15, and a known pigment dispersion
apparatus can be used. A bead mill is especially
preferably used, as it can produce a high processing flow
rate. In particular, as in the example illustrated below,
an annular bead mill incorporating a centrifuge which can
20 use small-diameter grinding media is preferred.
In the dispersion apparatus 15 shown in the
cross-sectional view of Fig. 10, a rotor 34 having a
cylindrical outer circumferential surface is installed in
a vessel 33 in which a inlet 32 is formed. An annular gap
X for dispersing pigment is formed between the inner wall
of the vessel 33 and the outer wall ~of the rotor 34.
The rotational drive shaft 34a of the rotor 34
is a hollow shaft, and an outlet opening 35 is formed in
said hollow shaft. A passage 36 is formed from a hollow
portion 34x of the rotational drive shaft 34a through the
rotor 34, and which opens at the bottom of the rotor 34.
A grinding medium (not Shawn) is introduced into
the vessel 33 in advance. The grain size of the medium
can be larger than 3 mm, as of those of the prior art, or
can have a very small diameter of 0.05-0.3 mm.
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A centrifuge 37 for centrifuging the grinding
medium flung through the passage 36 from the pigment
paste/pigment paste mixture is disposed inside the rotor
34. In the example illustrated, the centrifuge 37 employs
an impeller 38 disposed in the path of the passage 36. To
drive out centrifuged grinding medium to the annular gap X,
an opening for circulation 39, which communicates the
space surrounding the impeller 38 with the annular gap X,
is formed in the rotor 34.
The impeller 38 can employ various blades such
as flat blades, arrow blades and twisted blades, and has
the action of sucking up at the center of the blade and
driving out in the circumferential d_i.rection, that is,
acts as a centrifugal pump. The rotational drive shaft
38a of the impeller 38 is inserted into the hollow portion
34x of the rotor 34 and protrudes from the rotational
drive shaft 34a of the rotor 34. It should be noted that
40, 41 and 42 in the Fig. are sealing members.
The impeller 38 comprises, as shown in Fig. 11,
an annular plate 50 with an opening through its center
from the top face of the impeller 38. In the clearance
between this annular plate 50 and tYie impeller containing
space top wall portion of the rotor 34, as shown in Fig.
10, an annular mechanical seal 51 is provided so that the
grinding medium is not discharged through said clearance.
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Each of the rotational drive shafts 34a, 38a is
connected to a common primary drive M via a transmission
mechanism 45 in the example illustrated; however, the
primary drives of the rotational drive shafts 34a, 38a may
be connected to different primary drives. In the example
shown, the transmission mechanism 45 is a transmission
mechanism which is a combination of galleys 45a - 45d, and
pulley belts 45e, 45f wound around the pulleys 45a - 45d;
however, a gear transmission mechanism or like known
transmission mechanisms can be employed.
The passage 36 runs from the bottom of the rotor
34 to the center of the impeller 38, i.e., the part which
sucks up of the impeller 38. A circulatory channel which
runs from the annular gap X to the center of the impeller
38 and reaches the annular gap X again through the outer
circumference of the impeller 38 comprises the annular gap
X, the passage 36 and the circulating opening 39.
A stator 60 can be fixed at approximately the
center of the inner bottom of the vessel 33, with a
passage formed by a gap formed between the stator 60 and
rotor 34. The stator 60 has a configuration such that a
passage is formed at the center of impeller 38 where the
suctioning action by rotation is the: greatest, whereby the
circulation of the grinding medium and pigment paste in
the circulatory channel is enhanced. The stator 60
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imparts a speed difference due to the gap between the
inside of the rotor 34 and the outer wall of the stator 60,
and performs dispersion as does as the outer periphery of
the rotor 34. The stator 60 in the example illustrated
has an upper part formed in a shape of a cylindrical
truncated cone, but various other configurations such as a
non-truncated cone can be employed.
Jackets 61, 62 are formed in the outer
circumferential portion of the vessel 33 and stator 60. A
coolant medium is introduced into each of the jackets 61;
62 from a non-illustrated water inlet, and discharged from
a non-illustrated water outlet to prevent elevated
temperatures inside the vessel 33.
Assuming that the inner diameter of the vessel
33 is 1, the geometric dimensional ratios of the above-
mentioned dispersion apparatus 15 are preferably within
the following ranges:
The height H1 of the hollow portion inside the
vessel 33: 1.0-2.0
The outer diameter L1 of the stator 60: 0.5-0.7
The outer diameter L2 of the rotor 34: 0.95-0.98
The width X1 of the annular gap X: 0.02-0.05
The gap X2 between the rotor 34 and stator 60:
0.02-0.05
The diameter L3 of the portion of the passage 36
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which is in communication with the impeller 38: 0.1-0.3
The diameter L4 of the impeller 38: 0.6-0.8
The height H2 of the impeller 38: 0.2-0.3
The inner diameter L5 of the rotational drive
shaft 34a of the rotor 34: 0.3-0.4
The height H3 of the circulating opening 39:
0.25-0.35
The width L6 of the circulating opening 39:
0.05-0.1
Moreover, the number of rotation of the impeller
38 is suitably 1.5-2.0 times that of the rotor 34.
~nly one impeller 38 is shown in the
aforementioned embodiment, but two o:r more of the same may
be provided, and a static guide blade may be provided as a
turbine blade around the impeller 38. Tn addition, a
rotational disk (not shown) may be employed as the
centrifuge 37 in place of the impeller 38. When a
rotational disk is used, it has less action as a suction
pump compared to an impeller, but it, is capable of
applying centrifugal force to the grinding medium.
Moreover, rotary members with various configurations other
than a disk shape, such as spheres, elliptical spheres and
conical shapes, which can centrifuge a grinding medium by
rotation, may be employed.
It should be noted that an impeller can be
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fixedly or integrally formed in the rotor 34 as a
centrifuge to dispense with the rotational drive shaft of
the impeller. In this case, the number of rotatian
(rotation speed) of the impeller becomes equal to that of
the rotor. This leads to a reduced centrifugal action,
but can reduce the number of parts.
Moreover, the rotor 34 can be provided with a
plurality of projections such as pins on its outer
circumferential surface to increase 3.ts agitating effect.
In addition, the rotational drive shaft 38a of
the impeller 38 may be extended downward to protrude
through the bottom of the vessel 33.
In a circulation dispersion system having the
aforementioned constitution, circulation dispersion is
performed by repeating the following cycle: the second
directional control valve 17 is switched beforehand so as
to feed liquid discharged from the second pump 24 to the
side of the dispersion apparatus; pigment paste mixed and
agitated by the agitator 1 is drawn out from the agitating
vessel 2 through the fluid outlet 6 and fed to the
dispersion apparatus 15 by the drive of the second pump 14
via the pipeline for circulation dispersion 16: and the
dispersed pigment paste is fed into the agitating vessel 2
from the dispersion apparatus 15 through the fluid inlet 5.
The amount of pigment pas to force-fed to the
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dispersion apparatus 15 by the second pump 14 is suitably
controlled to be within a range that is not too much
greater than the centrifugal ability of the impeller 38
constituting the centrifuge.
While being agitated by the rotor 34 along with
the grinding medium, the pigment paste pumped to the
vessel 33 flows downward through the annular gap X between
the inner wall of the vessel 33 and the outer wall of the
rotor 34, passes through the gap between the bottom of the
rotor 34 and the bottom of the vessel. 33, and flows upward
through the gap between the inner wall of the rotor 34 and
the outer wall of the stator 60. Then, it is suctioned
from the center of the rotor 34 into the impeller 38 by
the centrifugal pump action of the impeller 38 disposed
inside the rotor 34.
The mixture of the pigment paste suctioned into
the impeller 38 and the grinding medium is affected by the
action of the centrifugal force by rotation of the
impeller 38 and the rator 34 external to it, and thus
separates the grinding medium and the pigment paste
because of a difference in specific gravity. The
grinding medium, with high specific gravity, is discharged
to the outer circumference, and returned to the annular
gap X between the inner wall of the vessel 33 and the
outer wall of the rotor 34 from the openings for
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circulation 39 formed in the rotor 34. It is then again
mixed with the pigment paste, and sent downward through
the annular gap X between the inner wall of the vessel 33
arid the outer wall of the rotor 34.
As already mentioned, circU.lation of the
grinding medium, which moves to the passage 36 running
from the annular gap X into the rotor., due to the flow the
pigment paste and returns through the circulating opening
39 by the impeller 38, is repeated. During this tame,
agglomerates (secondary particles) of the pigment
contained in pigment paste are dispersed into primary
particles by the strong shearing action caused by
collisions with the grinding medium in the annular gap X
between the inner wall of the vessel 33 and the outer wall
of the rotor 34.
The grinding medium separated from the pigment
paste by the impeller 38 flows upward through the gap
between the hollow portion 34x of the rotational drive
shaft 34a of the rotor 34 and the rotational drive shaft
38a of the impeller 38, runs through the outlet opening 35
formed in the rotational drive shaft 34a of the rotor 34,
and are discharged from an outlet 33a. Discharged pigment
paste is returned to the agitating vessel 2 via the
pipeline fox circulation dispersion 16. Circulation
dispersion is performed by this repeated circulation.
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After circulation dispersion is thus completed,
the pigment paste is discharged to a groduct tank 19 via a
third directional control valve 18. 'The pigment paste
remaining in the agitating vessel 2 and dispersion
apparatus 15 is then removed by cleaning.
Specifically, after the pigment paste is
discharged to the product tank 19, the first pump 24 is
driven to provide a cleaning liquid from the cleaning
liquid tank 20 to the agitating vessel 2. At this time,
ZO the cleaning liquid is sprayed at high pressure like a
shower from the cleaning nozzle 21 so that initial
cleaning is performed.
When a certain amount of the cleaning liquid is
collected in the agitating vessel 2, the first pump 24 is
25 stopped and the second pump 14 is driven to perform
circulation cleaning of the circulation dispersion system
by circulating a cleaning liquid through the agitating
vessel 2, dispersion apparatus 15, and pipeline for
circulation dispersian 16. At this time, the cleaning
20 liquid is collected in the agitating vessel 2, the flat
paddle blade 4 constituting the ag3.tating blade is
backwards and forwards rotated, whereby the flat paddle
blade 4 and the inner wall of the agitating vessel 2 can
be cleaned. While the cleaning liquid is circulating
25 through the circulation dispersion system, the dispersion
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apparatus is also driven so that the iiispersion apparatus
can also be cleaned efficiently.
When the cleaning liquid is contaminated to a
certain degree by circulation cleanin<~ and the cleaning
liquid loses the desired cleanability,, the cleaning liquid
is discharged to the waste fluid tank 25 by switching the
second directional control valve 17 and first directional
control valve 23, and fresh cleaning :Liquid is poured into
the cleaning liquid tank 20. This allows circulation
cleaning once more of the aforementioned circulation
dispersion system.
After the circulation dispersion system cleaning
is finished, the second directional control valve 17 is
switched so that discharge from the second pump 14 is sent
to the cleaning liquid tank 20. Circulation cleaning of
the circulation cleaning system is performed by
circulating cleaning liquid through the circulation
cleaning system comprising the agitating vessel 2,
circulatory cleaning pipeline 22, and cleaning liquid tank
20. It should be noted that in this case also, the
cleaning liquid can be replaced with fresh cleaning liquid
prior to the circulation cleaning of the circulation
cleaning system. After the circulation cleaning system is
cleaned, the first directional control valve 23 is
switched so that the cleaning waste fluid is discharged to
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the waste fluid tank 25.
In the aforementioned description, the
circulation cleaning system is subjected to circulation
cleaning after the circulation dispersion system is
subjected to circulation cleaning; however, the
circulation cleaning system may be cleaned first.
The above-mentioned circulation cleaning steps
can be automatically performed by sequence control. More
specifically, by using electromagnetic valves for the
first to third directional control valves 23, 17, 18,
opening and closing the first to third directional control
valve 34, 17, 18 and driving and stopping of the first
pump 24 and second pump 14 may be controlled by a
controller according to a predetermined sequence program
so that the aforementioned cleaning steps are performed
automatically.
This control may be such that the surface of the
liquid in the cleaning liquid tank 20 and/or agitating
vessel 2 is detected by a liquid surface sensor (not
shown), the detection signal is integfrated into the
control system, and the cleaning liquid is circulated
through the circulation cleaning line;, while driving and
stopping of the first pump 24 and second pump 14 are
controlled. In this case, circulation of the cleaning
liquid need not necessarily be continuous but may be
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intermittent.
It should be noted that the pigment paste to be
processed preferably has a viscosity :Ln the range of from
0.01 Pa~sec to 100 Pa~sec, especially i:rom 0.1 Pa~sec to 10
Pa~see, and has a TI value ranging of 1-10, especially
ranging 1-5. Said TI value is an abbreviation of
thixotropic index, and is a value obtained by converting
the numerical values determined (temperature: 20°C, number
of rotations of rotor: 6 and 60 rpm) by the rotation
viscosity method described in JTS K5101-6-2 to a mPa~s
basis and calculating the apparent viscosity in mPa~s at 6
rpm divided by the apparent viscosity mPa~s at 60 rpm.
Moreover, when the viscosity of the pigment
paste is high and the TI value is high, the adhesive power
of the pigment paste is high. Therefore, the inner wall
face of the agitating vessel 2, the surface of the
agitating blade 8, and the inner surfaces of the pipes are
desirably smoothened by mirror finishing, Teflon~ coating,
glass lining or like treatment.
In an agitator having the constitution of the
aforementioned first embodiment, pigment pastes with high
TI values and pigment pastes of high viscosity and the
like can be cooled by a flat paddle blade having a large
heat transfer area and a high contact frequency with a
fluid even in cases when a sufficiently high rate of heat
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transfer (cooling rate) can not be achieved by a coolant
jacket only, thus improving the cooling efficiency. Hence,
pigment paste can be mixed in a shorter period than the
residence time of ? in the agitating vessel 2.
Accordingly, when the agitator of the aforementioned first
embodiment is employed in the aforementioned circulation
dispersion system, dispersibility can be improved.
Moreover, as shown in the aforementioned second
embodiment, if the peripheral edge of the flat paddle
blade 4 is tapered by the two inclined surfaces 4c, 4c, as
shown in the cross-sectional view of Fig. 7 along with the
flow (broken line arrows) of the cleaning liquid, when the
flat paddle blade 4 rotates backwards and forwards (in Fig.
7, shown in only one direction), the pigment paste
deposited on each inclined surface can be pushed by the
flow of the cleaning liquid and removed efficiently.
Moreover, from such an efficiency perspective,
when the outermost periphery of the i°lat paddle blade 4 is
configured to have a V-shaped peripheral configuration
formed by the two inclined surfaces 4c, 4c, each of the
inclined surfaces 4c is preferably formed so that the
internal angle 81 ( refer ~to Fig . 4 ) between itself and the
flat surface (front or rear) of the :Flat paddle blade 4 is
in the range of from 100° -140° . If this angle of
inclination 81 is less than 100°, the; pigment paste is
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likely to deposit on the flat surface. If the angle of
inclination 81 is greater than 140°, the strength of the
flat paddle blade 4 is lowered, and when subjected to
fluorine resin coating or glass lining, the lining i.s
likely to come off because of contraction stress.
Moreover, since the agitating vessel 2 has a
bottom configuration of a truncated cone tapering
downwards as already stated, this forms a laminar flow
along the inclined surface of the boiaom when a cleaning
liquid is circulated through the dispersion line. As a
result, pigment paste deposited on the bottom of the
agitating vessel 2 can be efficiently removed.
From such an efficiency perspective, the bottom
conical surface of the agitating vessel 2 preferably has
such an inclination that the angle 8a (refer to Fig. 1)
between itself and the horizontal plane is 5°--30°. If the
angle of inclination 62 is less than 5°, pigment paste is
likely to pool around the joint of the body and the bottom
of the tank, hindering the flow of pigment paste to the
fluid outlet 6 during circulation cleaning. If the angle
of inclination 92 is greater than 30°, the pigment paste
is likely to short-path.
