JP2008068165A - Method and device for degassing liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for degassing a liquid that is of as the lowest cost as possible, and can smoothly perform processing without being polluted with particles and without an improper limitation. <P>SOLUTION: The liquid 2 is efficiently degassed with a negative pressure in a negative pressure space 3c on the liquid by allowing the liquid 2 to be fluidized with bubbles 11 generated by introducing a gas 10 into the liquid 2 in a storage tank 3 while a space in a vacuum container 4 is in negative pressure state. Because the solubility of the gas 10 in the liquid 2 is low and it is under the negative pressure, the gas 10 is hardly dissolved in the liquid 2. Because the method and the device for degassing a liquid are each of a simple configuration, they are at low costs. In addition, because a member that is a particle generating source is not provided in the container 4, there is no pollution caused by the particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid degassing method and a degassing apparatus, and more particularly, degassing by degassing dissolved gas in a liquid by setting a space above the liquid surface of a storage container in which the liquid is stored to a negative pressure state. The present invention relates to a method and an apparatus thereof.

  As is well known, in the semiconductor field using liquid, the chemical field including FPD (flat panel display) field, and the general industrial machine field, the dissolved gas dissolved in the liquid used for the use is the cause. It has led to various problems.

  As an example, when a gas such as air is dissolved in ink as a liquid used in an ink jet printer, when the ink is ejected from the printer, the dissolved gas is generated in the ink as bubbles when the ink is ejected. As a result, the nozzle for ejecting the ink of the printer is clogged with gas, causing a problem that the ink is not ejected.

  In order to prevent such a problem, it is effective to perform so-called degassing to remove dissolved gas dissolved in the liquid, and various measures as described below have been proposed or put into practical use as measures for that purpose. It has become.

  That is, according to the following Patent Document 1, the space on the liquid surface is in a negative pressure state, two kinds of stirring blades are put in the liquid, and the stirring blades are rotated in opposite directions by a motor. Thus, it is disclosed that the liquid flows and is turbulent. In this case, the plurality of bubbles in the liquid expands and floats on the liquid surface because the space on the liquid surface is in a negative pressure state, and these bubbles are increased in size by being combined on the liquid surface. And then rupture, thereby degassing.

  Further, according to Patent Document 2 below, the space on the liquid surface is set to a negative pressure state, and a stirrer made of a permanent magnet and a porous material is placed in the liquid and rotated by magnetic force from the outside of the liquid. Thus, a configuration is disclosed in which gas bubbles are generated from the porous portion of the stirrer and deaeration is performed by floating the bubbles on the liquid surface and causing the bubbles to burst.

  Furthermore, according to the following Patent Document 3, a hollow fiber membrane is produced using a membrane having characteristics of allowing gas to permeate and not liquid to permeate, and in the state where tens of thousands of these hollow fiber membranes are bundled, It is disclosed that the outside of the hollow fiber membrane is decompressed while flowing a liquid inside the membrane. According to such a method, the gas in the liquid is degassed by permeating through the hollow fiber membrane and going outside.

Moreover, according to the following Patent Document 4, nitrogen is blown into the liquid in the liquid feeding path under normal pressure without using the negative pressure (or reduced pressure) as described above, thereby forming nitrogen microbubbles. It is disclosed that a supersonic gas-liquid mixed state is generated and oxygen is deaerated by absorbing and removing oxygen in the liquid in a nitrogen bubble.
JP 2004-290859 A JP-A-9-155177 JP-A-5-317605 Japanese Patent Laid-Open No. 5-184811

  By the way, in the method disclosed in the above-mentioned Patent Document 1, particles (small foreign matters) generated from sliding portions such as a stirring blade and a rotating shaft contaminate the liquid. Similarly, even if the technique disclosed in Patent Document 2 is used, particles generated by rubbing the stirring bar in the liquid and the bottom of the container containing the liquid contaminate the liquid.

  On the other hand, in the technique disclosed in the above-mentioned Patent Document 3, in addition to the fatal defect that the hollow fiber membrane tube is expensive, a pressure is required for bundling tens of thousands of hollow fiber membrane tubes having an inner diameter of the order of microns. There is also a problem that the loss is large and the liquid degassing speed is slow. Furthermore, even by the method disclosed in Patent Document 4 described above, a fatal defect that is expensive due to the need for a long liquid supply path for absorbing oxygen in the liquid into the nitrogen bubbles occurs. In addition, since the main idea is to absorb nitrogen into the liquid under normal pressure, it cannot be used for liquids that cause problems under normal pressure, and the deaeration process is unduly restricted. Become.

  Accordingly, the present invention is technically to provide a liquid degassing method and a degassing apparatus that are as inexpensive as possible, are free from contamination by particles, and can be processed smoothly without being unduly restricted. Let it be an issue.

  The method according to the present invention, which was created to solve the above technical problem, is a degassing method in which a dissolved gas in a liquid is degassed by setting the upper space in contact with the liquid surface of the storage container in which the liquid is stored to a negative pressure state. In this method, by introducing an external gas into the liquid, an upward liquid flow is generated inside the liquid, and the dissolved gas in the liquid is moved to the upper negative pressure space through the liquid surface. It is characterized by that.

  According to such a method, since an upward liquid flow is generated inside the liquid by the operation of the external gas (bubble) introduced into the liquid, the dissolved gas (for example, air) dissolved in the liquid is liquid. The liquid moves from the surface to the negative pressure space, whereby the liquid is deaerated. In this case, the liquid flow upward is continuously performed with the introduction of the external gas into the liquid, so that the liquid level where the degassing process can be performed is always replaced, and the efficiency of the degassing process is improved. improves. This process simply introduces an external gas into the liquid to generate an upward liquid flow and moves the dissolved gas in the liquid to the negative pressure space, thereby greatly reducing the cost. In addition, since there are no driving parts including a rotating member, a moving member, and the like in the liquid, contamination by particles can be suppressed. In addition, since it is not necessary to use a large number of hollow fiber membranes, the pressure loss during the deaeration process is extremely small and the processing speed is greatly increased.

  In addition, it is suitable to use clean nitrogen in which particles do not exist as the external gas introduced into the liquid. That is, if the space in contact with the liquid surface is at normal pressure (atmospheric pressure) as described above, nitrogen introduced into the liquid and moving to the upper space may be taken into the liquid again. When the upper space in contact with the liquid surface is in a negative pressure state as in the case, nitrogen is smoothly moved from the liquid surface to the negative pressure space and is prevented from being taken into the liquid again. In addition, if the amount of external gas (for example, nitrogen) introduced into the liquid is excessive, the liquid may scatter and interfere with the deaeration process, and the gas in the liquid may move to the negative pressure space side. Since the moving speed varies depending on the type of liquid, it is preferable to set the amount of external gas in consideration of the saturation point of the moving speed. In addition, it is preferable to widen the area where the liquid and the negative pressure space come into contact in order to increase the deaeration efficiency.

  In this case, an opening is formed at the upper end of the storage container, the storage container is accommodated in the internal space of the vacuum container, and externally supplied to the liquid in the storage container through external gas supply means installed in the vacuum container. It is preferable to introduce a gas.

  In this way, it is extremely advantageous to simply and surely perform the negative pressure in the space above the liquid level of the storage container and introduce external gas into the liquid in the storage container. .

  On the other hand, an apparatus according to the present invention, which was created to solve the above technical problem, includes a storage container that stores liquid and a negative pressure suction unit that places a space above the liquid surface of the storage container in a negative pressure state. A liquid deaeration device comprising external gas supply means for supplying an external gas into the liquid in the storage container, and the operation of the external gas introduced into the liquid. It is characterized in that the liquid flow upward is generated in the liquid, and the dissolved gas in the liquid is moved to the upper negative pressure space through the liquid surface.

  According to such a configuration, it is possible to enjoy the same operational effects as those of the deaeration method described above by the operation of the negative pressure suction unit, the external gas supply unit, and the like.

  Also in this case, an opening is formed at the upper end of the storage container, the storage container is accommodated in the internal space of the vacuum container, and an external gas is supplied to the vacuum container in the liquid in the storage container It is preferable to install a gas supply means.

  In this way, as in the case described above, the space above the liquid surface of the storage container is brought into a negative pressure state, and external gas is introduced into the liquid in the storage container. It is extremely advantageous in carrying out the process.

  And it is preferable that the said external gas supply means has an external gas supply pipe | tube which has an open end in the lower part of the liquid in the said storage space.

  In this way, since the external gas enters from the lower part into the liquid in the storage container through the open end of the external gas supply pipe, the convection and stirring of the liquid including the upward liquid flow is preferably generated. Thus, an appropriate deaeration process is performed.

  In this case, the pressure in the negative pressure space is preferably 50 kpa to 10 kpa.

  That is, if the pressure in the negative pressure space is excessively low, sufficient deaeration cannot be performed. On the other hand, if the pressure in the negative pressure space is excessively high, the liquid may be vaporized and processed. When the liquid saturation point is exceeded, waste occurs. Therefore, the pressure in the negative pressure space is conveniently within the above numerical range.

  In the above configuration, the liquid is preferably ink used for an ink jet printer.

  More specifically, the liquid preferably has a viscosity of 5 to 18 cp. As a material having such a viscosity, a film material (for example, an alignment film material) used when a film (for example, an alignment film) is formed on a substrate (for example, a transparent substrate of a liquid crystal display device) can be exemplified. .

  As described above, according to the liquid degassing method and the degassing apparatus according to the present invention, the external gas is simply introduced into the liquid to cause upward liquid flow, and the dissolved gas in the liquid is brought into the negative pressure space. Since deaeration treatment can be performed simply by moving it, it is possible to achieve significant cost reductions, and there are no drive parts including rotating members, moving members, etc. in the liquid. Can be suppressed. In addition, since it is not necessary to use a large number of hollow fiber membranes, the pressure loss during the deaeration process is extremely small and the processing speed is greatly increased. Furthermore, even if nitrogen is used as the external gas, the upper space in contact with the liquid level is in a negative pressure state, so that nitrogen is smoothly transferred from the liquid level to the negative pressure space and is not taken into the liquid again. And good degassing treatment can be performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal front view of a liquid degassing apparatus according to the present embodiment.

  The deaeration device 1 includes a storage container 3 for storing a liquid (treatment liquid) 2 and a vacuum container 4 for completely storing the storage container 3 in an airtight internal space. It is mounted on the upper surface of. A gap is provided between the upper wall 3 a of the storage container 3 and the lid wall 4 a of the vacuum container 4. In addition, the storage container 3 has an opening 3b on its upper wall 3a (upper end), and stores the liquid 2 to a height approximately at the center in the height direction or higher.

  The vacuum container 4 has a liquid supply means 6 for supplying the liquid 2 to the storage container 3, a liquid extraction means 7 for taking out the liquid, and an upper space (negative pressure space) 3 c in contact with the liquid surface of the storage container 3. Negative pressure suction means 8 to be in a state and external gas supply means 9 for supplying external gas (nitrogen) 10 into the liquid 2 of the storage container 3 are installed.

  The liquid supply means 6 has a liquid supply pipe 61 that penetrates the lid wall 4 a from above the vacuum container 4 in an airtight state and reaches the internal space of the storage container 3, and the liquid is supplied above the lid wall 4 a of the liquid supply pipe 61. A supply valve 62 is installed. Further, the liquid take-out means 7 also has a liquid take-out pipe 71 that penetrates the lid wall 4a from above the vacuum vessel 4 in an airtight state and reaches the internal space of the storage vessel 3, and above the liquid take-out pipe 71 above the cover wall 4a. Also, a liquid extraction valve 72 is installed. The lower end openings of both the liquid supply pipe 61 and the liquid take-out pipe 71 are located around the bottom of the storage container 3 (lower part of the liquid 2).

  The negative pressure suction means 8 passes through the lid wall 4a from above the vacuum vessel 4 in an airtight state and opens to the inner surface of the lid wall 4a (the gap between the lid wall 4a and the upper wall 3a of the storage container 3). There is a pressure suction pipe 81, and a negative pressure suction valve 82 is installed above the lid wall 4 a of the negative pressure suction pipe 81.

  The external gas supply means 9 has an external gas supply pipe 91 that penetrates the lid wall 4a from above the vacuum vessel 4 in an airtight state and reaches the internal space of the storage container 3, and the lid wall 4a of the external gas supply pipe 91 A gas throttle valve 92, a gas flow meter 93, and a gas supply valve 94 are installed on the upper side in order from the upper side. The lower end opening (opening end) of the external gas supply pipe 91 is located around the bottom of the storage container 3 (lower part of the liquid 2). Further, an atmospheric pressure return external gas supply pipe 95 is branched from above the gas throttle valve 92 of the external gas supply pipe 91, and the atmospheric pressure return external gas supply pipe 95 is airtight in the lid wall 4a. Is opened between the upper wall 3a and the cover wall 4a of the storage container 3, and an atmospheric pressure return external gas release valve 96 is installed above the cover wall 4a of the atmospheric pressure return external gas supply pipe 95. ing.

  The arrow A indicates the direction of the flow of air or nitrogen 10 exhausted through the negative pressure suction pipe 81. An arrow B indicates the direction of the flow of the liquid 2 collected through the liquid take-out pipe 71. An arrow C indicates the flow direction of the liquid 2 supplied through the liquid supply pipe 61. An arrow D indicates the direction of the flow of the gas 10 supplied through the external gas supply pipe 91.

  According to the liquid degassing apparatus 1 having the above-described configuration, the following processing is executed.

  First, by opening the liquid supply valve 62, the liquid 2 to be deaerated is introduced into the storage container 3 through the liquid supply pipe 61, and the weight of the liquid 2 is measured by the weigh scale 5 to obtain a predetermined amount of liquid. When 2 is introduced, the liquid supply valve 62 is closed. Thereafter, by opening the negative pressure suction valve 82, the upper space in contact with the liquid surface of the storage container 3 through the negative pressure suction pipe 81 is brought into a negative pressure state.

  Further, by opening the external gas supply valve 94, nitrogen 10 is introduced into the lower part of the liquid 2 in the storage container 3 through the external gas supply pipe 91, and the nitrogen 10 introduced into the liquid 2 is introduced. The flow rate is adjusted by the gas throttle valve 92 while looking at the gas flow meter 93 and is fixed after the adjustment.

  In such a state, the liquid 2 around the bubbles 11 rises with the rise of the bubbles 11 caused by the nitrogen 10 introduced into the liquid 2 by being left for a predetermined time. The rising liquid 2 is degassed by the negative pressure on the liquid surface. Further, as the bubble 11 rises, a flow as indicated by an arrow is generated in the liquid 2, and the liquid 2 sequentially goes to the liquid surface over the entire area and is degassed by the negative pressure at the liquid surface. For this reason, the entire liquid 2 is efficiently deaerated.

  After a predetermined time has elapsed, the external gas supply valve 94 is closed, the negative pressure suction valve 82 is closed, and then the atmospheric pressure return external gas release valve 96 is opened to return the atmospheric pressure. External gas is introduced through the external gas supply pipe 95 until the negative pressure space 3c reaches atmospheric pressure. Thereafter, the liquid extraction valve 72 is opened, and the liquid 2 in the storage container 3 is recovered through the liquid extraction pipe 71.

  In this case, for the deaeration process, the atmospheric pressure in the vacuum vessel 4 takes about time for deaeration if the negative pressure is insufficient, and the liquid 2 is vaporized if the negative pressure is excessive. About 50 kPa to 10 kPa is preferable. Further, the liquid 2 has a limit on the effect of degassing due to negative pressure (the limit varies depending on the type of liquid), and further pressure reduction after reaching the limit is useless.

  Furthermore, for the deaeration treatment, if the flow rate of nitrogen 10 introduced into the liquid 2 is insufficient, there is no effect of stirring, and if it is excessive, the liquid 15 scatters, so about 10 mL / sec to 100 mL. / Sec is preferred.

  Moreover, since the deaeration of the liquid mainly occurs at the liquid level of the liquid 2 in the storage container 3, for this type of reason, the larger the liquid surface area of the liquid 2 in the storage container 3, the better. The wider the cross-sectional area in the horizontal direction of the inner surface of the storage container 3, the better. However, since the effect of stirring by the bubbles 11 is diminished as it becomes wider, the horizontal sectional area of the inner surface of the storage container 3 should be set in consideration of this.

  The deaeration processing time is set according to the target value of the dissolved air amount in the liquid 2. The target value of the dissolved air amount in the liquid 2 is determined depending on the use of the liquid 2, but the dissolved air amount that makes it impossible to deaerate any more may be set as the target value.

  The nitrogen 10 may be clean nitrogen because it has a low solubility in the liquid 2 and is inexpensive, for example. However, it is not particularly limited as long as the solubility in the liquid 2 is small.

  Actually, the deaeration process was performed using the deaerator 1 of FIG. The conditions were that ink of an ink jet printer was used as the liquid 2, clean nitrogen was used as the external gas 10, the atmospheric pressure in the vacuum vessel 4 was 40 kPa, and the gas flow rate was 50 mL / sec. As a result, after 20 minutes of degassing treatment, the amount of dissolved air became 4.0 ppm, which could not be further degassed. That is, in this embodiment, it has been found that a sufficient deaeration effect can be obtained.

  Furthermore, in order to confirm the presence or absence of particles, pure water was used as the liquid 2 and deaeration treatment was performed using the deaeration device 1 of FIG. The recovered pure water was measured with an in-liquid particle counter, but no particles were measured. That is, in the present embodiment, it has been found that the generation of particles can be prevented.

  Further, if two or more deaeration devices 1 in FIG. 1 are installed and the respective processing times are shifted, it is possible to perform the deaeration process continuously as a whole.

  Further, even with one degassing apparatus shown in FIG. 1, the degassing process can be continuously performed by the method described below. That is, by introducing the gas 10 into the liquid 2 in the storage container 3 and introducing the liquid 2 into the storage container 3 while collecting the liquid 2 from the storage container 3 in the vacuum container 4 in a negative pressure state. The deaeration process can be performed continuously.

It is a vertical front view of the liquid deaeration device concerning an embodiment of the invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deaeration device 2 Liquid 3 Storage container 3a Upper end (upper wall) of storage container
3b Opening 3c Negative pressure space 4 Vacuum container 8 Negative pressure suction means 9 External gas supply means

Claims (7)

A degassing method for degassing dissolved gas in the liquid by setting the upper space in contact with the liquid level of the storage container in which the liquid is stored to a negative pressure state,
By introducing an external gas into the liquid, an upward liquid flow is generated inside the liquid, and the dissolved gas in the liquid is moved to the upper negative pressure space through the liquid surface. Liquid degassing method.   An opening is formed at the upper end of the storage container, the storage container is accommodated in the internal space of the vacuum container, and an external gas is introduced into the liquid in the storage container through an external gas supply means installed in the vacuum container The liquid degassing method according to claim 1, wherein: A liquid deaeration device comprising: a storage container for storing liquid; and a negative pressure suction means for bringing a space above the liquid surface of the storage container into a negative pressure state,
An external gas supply means for supplying an external gas into the liquid in the storage container is provided, and an upward liquid flow is generated inside the liquid by the operation of the external gas introduced into the liquid, and the liquid A liquid degassing apparatus characterized in that the dissolved gas therein is moved through the liquid surface to an upper negative pressure space.   An opening is formed at the upper end of the storage container, and the storage container is accommodated in the internal space of the vacuum container, and external gas supply means for supplying external gas into the liquid in the storage container is installed in the vacuum container The liquid deaeration device according to claim 3, wherein the liquid deaeration device is provided.   5. The liquid deaeration device according to claim 3, wherein the external gas supply unit includes an external gas supply pipe having an open end at a lower portion of the liquid in the storage space.   The liquid deaeration apparatus according to claim 3, wherein the pressure in the negative pressure space is 50 kpa to 10 kpa.   The liquid deaeration apparatus according to claim 3, wherein the liquid is ink used for an ink jet printer.

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