JP6398080B2 - Ink defoaming apparatus and ink defoaming method - Google Patents

Description

  The present invention relates to an ink defoaming apparatus and an ink defoaming method that efficiently remove bubbles in ink.

  When forming a coating film, if air bubbles are mixed in the ink forming the coating film, it causes defects such as pinholes and cracks in the coating film. Bubbles in the ink are often generated by air mixing in the stirring / kneading process at the time of ink preparation, air mixing in piping at the time of coating, and air mixing at the time of supplying ink to the coating tank.

  Therefore, a defoaming process that removes bubbles in the ink upstream and as close to the process of forming the coating film as possible is essential.

  As a conventional ink defoaming device, the contents described in Patent Document 1 are known. The apparatus disclosed in this document will be described with reference to FIG.

  FIG. 5 is a schematic view of a cross section of a conventional defoaming apparatus.

  In FIG. 5, the defoaming device 100 has an ink passage 103 and a vacuum chamber 104 formed by a wall surface 101 and a thin film 102, and the thin film 102 has a first surface and a second surface, The first surface is in contact with ink (not shown) in the ink passage, and the second surface is in contact with the vacuum chamber.

  The ink passage 103 has an ink inlet 106 connected to an ink supply tank for supplying ink and an ink outlet 108 connected to a coating apparatus 107 such as an inkjet (IJ). Further, the ink passage 103 has a slope inclined downward from the ink inlet 106 toward the ink outlet 108, and is gradually lowered over the entire length between the ink inlet 106 and the ink outlet 108.

  Further, the ink flowing through the ink passage 103 and the member that separates the vacuum chamber 104 are the thin film 102, and degassing is performed by allowing the gas contained in the ink to pass through the thin film 102 toward the vacuum chamber 104. Is disclosed.

  The content of patent document 2 is known as another conventional ink defoaming apparatus. The technique described in this document relates to a batch-type vacuum defoaming method in which bubbles are removed by putting the prepared ink in a tank and creating a vacuum environment.

JP 2006-281784 A Japanese Patent No. 3838161

  However, the ink defoaming device described in Patent Document 1 cannot be passed through the thin film 102 unless the vacuum is high, so that the running cost for maintaining the high vacuum is high, the equipment is large and the equipment cost is high. Has the problem of being expensive. The thin film 102 is a film having fine holes through which only air bubbles do not pass, and when used for a long time, particles in the ink accumulate on the surface of the thin film 102. As a result, the fine holes are blocked and clogged, and the defoaming process cannot be performed sufficiently. In order to maintain the defoaming performance, clogged thin films must be frequently replaced.

  Furthermore, the bubbles have the property of rising upward due to buoyancy in the ink, but since there is a slope inclined downward between the ink inlet 106 and the ink outlet 108, the flow of the ink and the rising of the bubbles are reduced. It is the composition which becomes the reverse direction. Therefore, fine bubbles are easily diffused into the ink, and a stable defoaming process cannot be performed. That is, there is a problem of stability of the defoaming process.

  Next, since the defoaming method described in Patent Document 2 is a batch type process in which the ink supplied to the tank is left for a long period of time to perform the defoaming process, a large lead time is required from ink preparation to coating. I need. Therefore, in order to apply a large amount, it is necessary to store a large amount of ink tanks to be defoamed, and to manage the defoaming treatment process and the ink after the treatment. Therefore, a continuous defoaming process is desired in which the defoaming process is performed to supply the ink immediately after preparation to the coating apparatus while defoaming. However, the defoaming method described in Patent Document 2 has a problem that it cannot cope with the continuous defoaming treatment.

  Accordingly, an object of the present invention is to provide an ink defoaming apparatus and an ink defoaming method that realize continuous and stable defoaming processing at low cost.

  An ink defoaming device for solving the above problems will be described.

  The ink defoaming device of the present invention includes an inlet for supplying ink, a manifold for spreading the ink in the width direction of the defoaming device, a narrow passage for uniting the bubbles in the ink, and the upper portion of the ink by buoyancy. And a degassing port for removing the collected bubbles, and an outlet of the defoamed ink.

  Next, an ink defoaming method using the defoaming apparatus will be described.

  By supplying ink containing bubbles from the ink inlet and filling the manifold once with ink, the ink is uniformly spread in the width direction of the defoaming device. Next, by continuing to supply ink from the ink inlet, the narrow passage is passed. At this time, bubbles in the ink are crushed in the narrow gap of the narrow passage in the narrow passage. At that time, some bubbles are united, grow into large bubbles and are discharged to the bubble collecting manifold.

  The discharged air bubbles move upward by buoyancy in the foam collecting manifold, and the air bubbles are removed from the defoaming port. The defoamed ink is discharged from the ink outlet and supplied to a coating apparatus or the like.

  A large-scale high vacuum processing machine is not required, and bubbles in the ink can be removed efficiently and continuously. That is, it is possible to realize a continuous and stable defoaming process at low cost, and as a result, it is possible to suppress the occurrence of pinholes and cracks by applying ink with less bubbles, so that the coating film forming process Yield can be improved.

Diagram of the defoaming device used in Embodiment 1 of the present invention The figure which shows the motion of the bubble of the defoaming apparatus used in Embodiment 1 of this invention. Schematic of the defoaming device used in Embodiment 2 of the present invention The figure which shows the motion of the bubble of the defoaming apparatus used in Embodiment 2 of this invention. Schematic of defoaming device in the conventional example

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
[Deaerator configuration]
An outline of the ink defoaming apparatus used in this embodiment will be described with reference to FIG.

  Fig.1 (a) shows the schematic sectional drawing of a defoaming apparatus, FIG.1 (b) shows the schematic top view of a defoaming apparatus.

  The configuration of the ink defoaming device is as follows: an ink inlet 1 for supplying ink, a manifold 2 for spreading the ink in the width direction of the defoaming device, and two or more blocks 3 having a predetermined shape and thickness in the ink passage. In addition, it has an adjustable narrow passage 4 that can adjust the gap between the blocks.

  Further, a foam collecting manifold 5 having a predetermined space on the opposite side to the manifold 2 with respect to the narrow passage 4 is provided, and the defoaming port 6 is placed above the foam collecting manifold 5 at a position lower than the defoaming port 6. The ink outlet 7 is provided. If necessary, a thin film 8 having a filter effect may be installed in the defoaming port 6.

  Here, the block 3 forming the narrow passage 4 is formed of a metal member that is not corroded by ink such as stainless steel, but may be a transparent block such as acrylic resin or glass. It is also possible to perform processing while visually confirming the state of generation of bubbles through a transparent block.

  Next, important elements among the constituent elements of the ink defoaming apparatus will be described.

  When the shape of the narrow passage 4 through which ink flows is flat as shown in FIG. 1, it is important to flow ink in parallel to the shape of the narrow passage 4. If ink cannot flow in parallel, for example, ink does not flow at the end in the width direction of the narrow passage 4, and ink flows only at the center in the width direction in the narrow passage 4, ink in the narrow passage 4. Stagnation occurs. This is because bubbles present in the ink stay.

  In order to avoid this state, the manifold 2 is necessary. The manifold 2 needs to be sized so that the ink easily spreads in the width direction of the defoaming device, that is, the width direction of the narrow passage 4. Specifically, it is important to make the entire width of the narrow passage 4 smaller than the pressure loss at which ink flows than the pressure loss at which ink flows in the width direction of the manifold 2. That is, the manifold 2 needs a space sufficiently larger than the size of the ink inlet and a space sufficiently thicker than the gap of the narrow passage 4.

  In the present embodiment, the manifold 2 has a width of 100 to 1000 mm, a thickness of 10 mm to 50 mm, and a gap between the narrow passages of 10 to 500 μm. Details of the gap size of the narrow passage 4 will be described later.

  Next, the foam collection manifold 5 will be described.

  Since the ink that has passed through the narrow passage 4 passes through a narrow gap, the speed at which bubbles present in the ink flow is very high. However, in the bubble collecting manifold 5 having a predetermined space, the ink flowing speed, that is, the bubble flowing speed in the ink is low. That is, by rapidly reducing the flow rate of bubbles from the narrow passage 4 to the bubble collection manifold 5, the bubble buoyancy is actively exerted, and the bubbles are collected in the defoaming port 6 installed above the bubble collection manifold. Can do.

  Here, a measure for narrowing the width of the narrow passage 4 from the manifold 2 toward the bubble collecting manifold 5 with respect to the direction of ink flow is also effective from the viewpoint of preventing bubbles from staying in the narrow passage 4.

  The sizes of the manifold 2, the narrow passage 4, and the bubble collecting manifold 5 are appropriately adjusted depending on the type of ink. For example, if the ink has high viscosity and bubbles are difficult to escape, the ink flow distance, that is, the narrow passage 4 is lengthened.

  In the present defoaming apparatus according to the present embodiment, the ink inlet 1 is connected to an ink supply tank or the like, and the ink outlet 7 is connected to a coating apparatus such as a die coat head or an inkjet head so that the ink is continuously defoamed. It is possible to apply.

  The bubble removal port 6 includes a valve and a valve (not shown) that can be controlled to open and close, and has a structure that can remove bubbles. The valve or valve is normally closed to prevent volatilization of the solvent component of the ink, and when air bubbles gather around the defoaming port 6 and the surrounding pressure increases, the air bubbles are released to the atmosphere. Therefore, a mechanism that manages the pressure at regular intervals and pressure and can be opened or closed manually or automatically.

In addition, when the ink has a large viscosity or solid content in the ink, when performing the defoaming process of the ink in which bubbles are not easily removed, the thin film 8 is installed in the defoaming port 6 and the depressurizer 9 such as a vacuum pump is defoamed. It is also possible to connect and use the mouth 6. The thin film 8 is a film that does not transmit ink but transmits only air bubbles. For example, the thin film 8 is a filter formed of a porous film having nano-sized air holes or nano-sized fibers.
[Principle of defoaming]
The principle of defoaming using the defoaming apparatus will be described with reference to FIG.

  2A and 2B are diagrams showing the behavior of bubbles present in the ink in the apparatus of FIG. 1, FIG. 2A is a cross-sectional view, and FIG. 2B is a top view.

  First, ink to be defoamed is supplied into the defoaming apparatus by pumping or pressurized gas from the ink inlet 1 for supplying ink. The supplied ink is fed into the manifold 2 to spread the ink evenly in the width direction of the defoaming apparatus. In the manifold 2, the air bubbles 10 are present in the ink.

  Next, the bubble 10 passes through the narrow passage 4 together with ink. In the manifold 2, when a substantially spherical bubble is crushed into a gap smaller than the spherical diameter, a phenomenon occurs in which the bubble is thinned and expanded. Therefore, as the gap in the narrow passage 4 is narrower, the bubbles 10 are crushed and pass as bubbles 11 having a diameter larger than the diameter of the bubbles. The bubbles 11 are easily brought into contact with the adjacent bubbles 11 by being spread out, the bubbles are united, and grow into bubbles 12 having a larger volume.

  When the bubbles 12 grow from the narrow passage 4 to the bubble collection manifold 5, they move upward of the bubble collection manifold 5 to form a bubble pool 13 due to the buoyancy of the bubbles. The bubble pool 13 is removed from the defoaming port 6 installed near the bubble pool 13.

  The ink from which the bubbles are removed can be supplied to the coating apparatus by discharging the ink from which the bubbles have been removed from the ink outlet 7 to the outside of the defoaming apparatus. When removing bubbles from the defoaming port 6, the degassing port 6 is opened to the atmosphere to remove the bubbles, and the atmospheric pressure is removed. The depressurizer is connected to the degassing port 6 to remove bubbles in a depressurized state. Two methods of removal are possible. Detailed conditions will be described later in Examples.

  In this example, acetylene black having a predetermined particle diameter as carbon, pure water as a solvent, and a polytetrafluoroethylene solution (solid content concentration 60%) as a binder were prepared so as to have a predetermined solid content concentration. Further, an ink was prepared using an ultrasonic homogenizer as a dispersing means. Further, with respect to the prepared ink, the viscosity was measured with a cone plate viscometer, and the particle size in the ink was measured with a laser particle size distribution meter to confirm the ink physical properties.

  The physical property evaluation contents (ink viscosity, ink average particle diameter) of the ink prepared using the ink preparation method described above, and the processing conditions of the defoaming apparatus described in FIG. It was used to check the degree of defoaming of the ink. The ink prepared as an evaluation of the degree of defoaming was applied to a predetermined film thickness using a doctor blade and dried at 30 to 50 ° C. until the solvent was removed.

  With respect to the coating film formed by drying, the presence or absence of pinholes and cracks within 100 mm □ was confirmed. The depressurization degree (differential pressure with respect to the atmospheric pressure) of the defoaming port was set to 0, that is, defoaming treatment (removal to the atmosphere) was performed by opening the valve to the atmosphere. The results are shown in Table 1.

The results of Table 1 will be described.

  Sample: As shown in the results of 1 to 14, when the gap of the narrow passage 4 is wider than the coating film thickness, the coating result has pinholes and cracks. This is because the bubbles in the ink are crushed and unified by the narrow passage 4 to be defoamed, and it can be said that bubbles smaller than the gap in the narrow passage 4 are difficult to remove. Therefore, when the gap of the narrow passage 4 is larger than the coating film thickness, it is considered as a result of the bubbles having a size that generates a pinhole being mixed into the coating film. Therefore, it is desirable that the gap of the narrow passage 4 is smaller than the coating film thickness.

  Next, samples 15 to 17 will be described.

  This is a result of changing the relationship between the average particle diameter of carbon in the ink and the gap of the narrow passage.

  As can be seen from this result, when the average particle diameter of carbon is the same as the gap between the narrow passages, the defoaming treatment cannot be stably performed. This is thought to be because the particles were clogged in the narrow passages, making it difficult for the ink to flow. Therefore, it is desirable that the gap of the narrow passage is larger than the maximum particle diameter of the particles. Furthermore, it is desirable that the size be at least twice the maximum particle size.

  Here, if the gap between the narrow passages is narrow, the pressure loss increases, so that the pressure required to supply ink tends to increase. Therefore, it is desirable to make it as wide as possible, and it is necessary to adjust it according to the viscosity of the ink.

  Next, Table 2 shows the results of confirming the behavior when the ink viscosity is changed by changing the solid content concentration and the binder mixing ratio at the time of ink preparation.

  The results shown here are the same as in Table 1. Furthermore, the experiment was carried out by changing the degree of vacuum at the degassing port. Here, when the pressure reduction degree of the degassing port is 0, when the pressure reduction degree (differential pressure with respect to the atmospheric pressure) of the degassing port is “−10 kPa”, “−30 kPa”, “−100 kPa” by the open air removal Indicates vacuum removal.

The results of Table 2 will be described.

  From the results of samples 18 to 21, there was a tendency for defects to occur in the coating results as the ink viscosity increased. In the bubble collection manifold 5 of FIG. 2, if the ink viscosity is high, bubbles are not easily raised by buoyancy and are not easily removed from the bubble removal port 6, and bubbles existing around the bubble removal port 6 are removed from the ink outlet 7. Considered to be discharged with ink.

  Therefore, as in samples: 22 to 25, by increasing the degree of decompression of the defoaming port 6 (increasing the differential pressure from the atmospheric pressure), the removal of bubbles existing around the defoaming port 6 described above is promoted. I was able to. As a result, it can be inferred that a defoaming treatment could be stably performed even with ink having a high viscosity, and a coating film free from pinholes and cracks could be formed.

  On the other hand, as in Samples 26 to 27, when the degree of decompression of the defoaming port 6 was too high (the differential pressure from the atmospheric pressure was too large), the ink physical properties changed and it was impossible to apply stably. . This is presumably because the solvent (water in this embodiment) constituting the ink is easily vaporized due to the degree of reduced pressure, and the concentration of the ink is changed. It can also be inferred that a stable coating film could not be formed because the particles in the ink partially aggregated.

  That is, it is necessary to adjust the pressure reduction degree of the defoaming port 6 according to the viscosity of the ink and the type of the solvent, and it is desirable to provide a mechanism for adjusting the pressure reduction degree.

(Embodiment 2)
A mode in which the same effect can be obtained even in a configuration different from the ink defoaming device of the first embodiment will be described in detail.

  The apparatus configuration according to the present embodiment is shown in FIG. 3 (a) is a front view of the defoaming device, FIG. 3 (b) is a cross-sectional view of the XX plane of FIG. 3 (a), and FIG. 3 (c) is a Y- A sectional view of the Y plane is shown.

  The configuration of the defoaming device will be described with reference to FIG.

  The ink defoaming device includes an ink supply port 17 connected to the ink supply means, a narrow gap 18 that is adjusted to a predetermined gap (A in the figure) and is installed in a direction opposite to gravity (hereinafter, vertically upward), A bubble collecting manifold 19 that collects bubbles and raises them by buoyancy, a narrow passage 20 installed in a vertical direction, an ink outlet 21 connected to a coating device and the like, and a degassing port 22 installed above the bubble collecting manifold. .

  In this apparatus, it is important that the width of the foam collecting manifold (B in the figure) is wider than the gap (A in the figure) between the narrow passages 18 and 20. Details thereof will be described later. In the present embodiment, the widths of the narrow passages 18 and 20 are the same. However, in the present embodiment, the width is not particularly limited and may be different.

  By installing the ink outlet 21 at a position lower than the defoaming port 22, it is possible to suppress the bubbles collected around the defoaming port 22 from being discharged from the ink outlet 21, thereby realizing a more stable defoaming process. Can do.

  Next, an ink defoaming method will be described with reference to FIG. FIG. 4 is a diagram showing the behavior of bubbles in FIG.

  First, ink (not shown) supplied from the ink supply port 17 is introduced into the narrow passage 18. At this time, the air bubbles 23 in the ink flow radially while being expanded in the gap of the narrow passage 18.

  Next, the adjacent bubbles in the narrow passage 18 are united to grow into a large bubble 24. At this time, the narrow passage 18 has a structure extending vertically upward, and the bubbles 23 grow into bubbles 24 while gradually moving upward. The grown bubbles 24 are discharged as large bubbles 25 into the bubble collection manifold 19. The bubble 25 rises by buoyancy and rises above the foam collection manifold 19.

  Next, the ink from which the bubbles are removed passes through the narrow passage 20 and flows to the ink outlet 21, and is supplied from the ink outlet 21 to the coating apparatus and the like.

  The size (width (B in the figure) and height (C in the figure)) of the bubble collecting manifold 19 needs to be adjusted in accordance with how the ink bubbles are removed. For example, when the ink viscosity is high and it is difficult for bubbles to rise, adjustment is made so that B and C in the figure are increased. Moreover, although the circular shape was used for the cross-sectional shape of the foam collection manifold 19 in this Embodiment, square shape may be sufficient and it is not specifically limited.

  Next, the ink discharged to the bubble collecting manifold 19 is passed through a narrow passage 20 having a narrow gap. Thereby, the narrow gap of the narrow passage 20 becomes resistance when bubbles flow into the narrow passage 20, and the bubbles in the foam collecting manifold 19 are difficult to flow into the narrow passage 20. Therefore, since it rises by buoyancy, the defoaming process can be performed more stably.

  At this time, it is desirable that the resistance due to the gap of the narrow passage 20 is larger than the buoyancy of the bubbles, and it is necessary to adjust in accordance with physical properties such as ink viscosity.

  Next, examination was performed by changing the gap (A in the figure) of the narrow passages 18 and 20 and the width of the foam collecting manifold (B in the figure).

  Using the ink prepared by the ink preparation method shown in Embodiment 1 using the defoaming apparatus, a coating film is formed using the ink subjected to physical property evaluation and defoaming treatment, and pinholes and cracks are formed. The presence or absence of occurrence was confirmed. The results are shown in Table 3.

From the samples in Table 3, from 28 to 36, when the width of the foam collecting manifold became 10 times or more than the gap of the narrow passage, the defoaming treatment was stabilized and the result of good coating results was obtained.

  For the same reason as described in the first embodiment, it is necessary that the gap of the narrow passage is narrower than the coating film thickness. Therefore, it is desirable that the gap of the narrow passage is narrower than the coating film thickness, and the width of the foam collecting manifold is 10 times or more than the gap of the narrow passage.

  By applying the defoaming apparatus of the present application, it can be applied to ink coating of a fuel cell catalyst layer, a lithium ion electrode, a capacitor, and the like, and it is possible to form a high-quality coating film free from pinholes and cracks.

DESCRIPTION OF SYMBOLS 1,106 Ink inlet 2 Manifold 3 Block 4,18,20 Narrow passage 5,19 Foam collection manifold 6,22 Defoaming port 7,21,108 Ink outlet 8,102 Thin film 9 Depressurizer

Claims (5)

An ink supply port for flowing ink containing particles ;
And expandable manifold said ink in the width direction,
An ink passage for the ink is a passed through a slit of a predetermined interval, to coalescence of bubbles of the ink,
And Atsumariawa manifold increases by buoyancy coalesced said bubble,
A bubble removing mechanism for removing the rises and the bubble collected,
An ink outlet for discharging the ink, in the configuration,
The predetermined interval is larger than the maximum particle size of the particles,
A width of the foam collecting manifold is 10 times or more of the predetermined interval;
The predetermined interval is smaller than the thickness of the coating film obtained by applying the defoamed ink.
An ink defoaming device. The ink outlet is installed at a position lower than the bubble removing mechanism.
The ink defoaming device according to claim 1. The ink defoaming device according to claim 1, wherein a width of the ink passage is narrowed from the manifold toward the bubble collecting manifold. Between the bubble removal mechanism and the ink outlet,
A transparent slit is arranged, and the presence of bubbles can be confirmed visually or through a detector through the slit.
The ink defoaming device according to any one of claims 1 to 3 . In an ink defoaming method for removing bubbles of ink containing particles ,
By passing the ink through the slits at a predetermined interval, the air bubbles present in the ink are expanded and coalesced with the adjacent air bubbles, and then the air bubbles are united by being discharged into a space larger than the slit. Is an ink defoaming method that floats by buoyancy and removes the air bubbles
The predetermined interval is larger than the maximum particle size of the particles,
The width of the space is at least 10 times the predetermined distance,
The ink defoaming method , wherein the predetermined interval is smaller than a thickness of a coating film obtained by applying the defoamed ink.

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