JP2009148693A - Method and apparatus for degassing liquid coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for degassing a liquid coating capable of removing bubbles mixed with the coating efficiently with a simple configuration of the apparatus. <P>SOLUTION: The method of degassing a liquid coating is characterized by stirring a bubble-mixed liquid coating by means of a stirring screw 23 having a stirring blade 26 equipped with a liquid guiding section 45 tapered toward the back in the proceeding direction so as to flocculate and float bubbles b in the liquid guiding section 45. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid paint defoaming method and a liquid paint defoaming apparatus for removing bubbles from a liquid paint mixed with bubbles.

Conventionally, as this type of defoaming device, a container for storing a high-viscosity liquid material, a vacuum decompression device for depressurizing the inside of the container, and a gas cylinder for agitating the liquid material with the gas blown into and blown into the liquid material (See Patent Document 1). In this defoaming device, the flowability of the liquid material is improved by the blown gas and the stirring of the liquid material is promoted. On the other hand, the inside of the container is depressurized by the vacuum decompression device, and finally bubbles (gas) in the liquid material are removed. It expands and floats (defoaming).
JP 2005-161273 A

  In such a conventional defoaming device, a vacuum decompression device that accommodates a container in which a liquid material is stored is required, and there is a problem that the facility becomes large. Further, for example, in the case of a liquid material using a highly volatile solvent, there has been a problem that evaporation of the solvent is promoted by the reduced pressure, and the concentration and viscosity change.

  An object of the present invention is to provide a liquid paint defoaming method and a liquid paint defoaming apparatus capable of efficiently removing bubbles mixed in the liquid paint with a simple apparatus configuration.

  The method of defoaming a liquid paint according to the present invention uses a stirring screw having a stirring blade that constitutes a liquid introduction portion that becomes narrower toward the rear in the moving direction, and stirs the liquid paint mixed with bubbles with the stirring screw. In the liquid introduction part, bubbles are aggregated and floated.

  The defoaming device for a liquid paint of the present invention comprises a container for storing the liquid paint, a stirring screw immersed in the container, and a drive mechanism for rotating the stirring screw, and the stirring screw is directed rearward in the moving direction. It has the stirring blade which comprised the liquid introduction part which becomes narrow and narrow.

  According to these configurations, when the liquid paint mixed with bubbles is stirred with the stirring screw, the liquid paint passes through the stirring blade (liquid introduction part), and the bubbles are compressed and aggregated in the liquid introduction part and gradually become larger. It will become. Bubbles in the liquid paint that have become sufficiently large float on the liquid surface and are defoamed. In this way, since the defoaming can be performed simply by stirring the liquid paint with the stirring blades constituting the liquid introduction part, the apparatus configuration can be simplified and bubbles in the liquid paint can be easily defoamed. be able to.

  In the above defoaming method of the liquid paint, it is preferable that the stirring blade is composed of two blade plates arranged to face each other.

  Similarly, in the defoaming device for liquid paint, it is preferable that the stirring blade is composed of two blade plates arranged to face each other.

  In the liquid paint defoaming apparatus, the two blades are preferably composed of two flat plates arranged at a narrowed angle.

  According to these structures, since the stirring blade which comprised the liquid introduction part was comprised by the two blade plates, the stirring blade can be formed easily.

  In the above defoaming method of the liquid paint, it is preferable that the stirring blade is formed of a cylindrical body.

  Similarly, in the defoaming device for a liquid paint, it is preferable that the stirring blade is composed of a cylindrical body.

  In the liquid paint defoaming apparatus, the cylindrical body is preferably formed in a truncated cone shape.

  According to these structures, since the stirring blade which comprised the liquid introduction part is comprised with the cylindrical body, while being able to form a stirring blade easily, a bubble can be aggregated efficiently.

  In the liquid paint defoaming method, it is preferable that the rear end portion in the moving direction of the cylindrical body is closed with a perforated plate.

  Similarly, in the liquid paint defoaming device, it is preferable that the rear end portion in the moving direction of the cylindrical body is closed with a perforated plate.

  According to these structures, since the enlarged bubbles are further compressed in the perforated plate, aggregation is further promoted.

  In the above defoaming method of the liquid paint, it is preferable that the stirring blade is inclined so that the rear part is directed upward with respect to the moving direction.

  Similarly, in the defoaming device for a liquid paint, it is preferable that the stirring blades are inclined so that the rear part faces upward with respect to the moving direction.

  According to these configurations, since the bubbles that have become large in the liquid introduction part are released toward the liquid surface of the liquid paint, the bubbles can be promoted to the liquid surface and the defoaming time can be shortened. be able to.

  In the liquid paint defoaming device, the stirring screw preferably has a plurality of stirring blades in the circumferential direction.

  According to these configurations, since the bubbles can be enlarged at a plurality of locations at a time, the defoaming time can be further shortened.

  In the liquid paint defoaming device, a circulation channel that communicates the bottom and the top of the container, a circulation pump that is interposed in the circulation channel and feeds the liquid paint from the bottom of the container to the top of the container, It is preferable to further include

  According to this configuration, for example, even when the liquid paint is composed of a solvent and a pigment that easily precipitates, the mixing of the solvent and the pigment can be promoted while defoaming.

  Hereinafter, a coating system using a defoaming apparatus according to a first embodiment of the present invention will be described with reference to the accompanying drawings. In this coating system, in order to increase the coefficient of friction on the workpiece surface, an aqueous liquid paint containing a pigment such as alumina is applied to the work by spraying. The paint tank (tank unit) for storing the liquid paint is a solvent. It has a function of defoaming bubbles generated when a pigment is added to the.

  As shown in FIG. 1, a coating system 1 includes a tank unit 2 that stores liquid paint and has a stirring and defoaming function, a coating unit 3 that applies liquid paint to a work W by a spray method, The liquid supply flow path 4 has a forward flow path 31 and a liquid supply return flow path 32 and connects the tank unit 2 and the coating unit 3.

  The coating unit 3 stores a work case W, a spray case 12 which is housed in the paint case 11 and sprays liquid paint onto the work W, and is connected to the spray nozzle 12 to mix liquid paint and compressed air. -The liquid mixing part 13 is provided. The gas-liquid mixing section 13 is connected with a liquid supply flow path 4 connected to the tank unit 2 and an air flow path (not shown) connected to a compressor or the like. The coating unit 3 mists the supplied liquid paint with the supplied compressed air and sprays it onto the workpiece W via the spray nozzle 12.

  The tank unit 2 includes an open top container 21 that stores liquid paint, and an agitation mechanism 22 that stirs the liquid paint by being immersed in the container 21 and agglomerates and degass the mixed bubbles b. is doing. The container 21 is formed in a cylindrical shape with a bottom made of stainless steel or the like, and a liquid feed return flow path 32 is connected to the upper part, and a liquid feed forward flow path 31 is connected to the bottom part.

  The stirring mechanism 22 is immersed in the container 21 to stir the liquid paint, a motor 24 that is a drive source of the stirring screw 23, and supports the stirring screw 23 and the motor 24 and also serves as a lid of the container 21. And a support frame 25. As will be described in detail later, the stirring screw 23 has a plurality of stirring blades 26 that stir the liquid paint and agglomerate the mixed bubbles b. The motor 24 is composed of a geared motor or the like, and rotates the stirring screw 23 at a low speed.

  The liquid feed flow path 4 has an upstream end connected to the bottom of the container 21 and a downstream end connected to the inflow port of the gas-liquid mixing section 13, and an upstream end connected to the gas-liquid mixing section 13. And a bypass flow path 33 interposed between the liquid supply forward flow path 31 and the liquid supply return flow path 32. Has been. A liquid feed pump (circulation pump) 34 that feeds the liquid paint from the tank unit 2 to the coating unit 3 and circulates the liquid paint from the bottom to the top of the container 21 in the liquid feed forward flow path 31. It is installed. The liquid feed pump 34 is constituted by a Mono pump or a trochoid pump in order to feed and circulate a liquid paint that is a highly viscous fluid.

  The bypass flow path 33 constitutes a circulation flow path 35 that circulates the liquid paint in the container 21 by shortcutting the liquid supply flow path 4. It is connected to a branch valve 36 provided on the downstream side, and a downstream end is connected to a junction 37 provided in the liquid feed return channel 32. Note that the circulation flow path 35 according to the claims is formed by the liquid supply forward flow path 31 from the container 21 to the branch valve 36, the bypass flow path 33, and the liquid supply return flow path 32 from the junction 37 to the container 21. In addition, the tank unit 2 and the circulation flow path 35 constitute a defoaming device 38 according to the claims.

  At the time of painting, the branch valve 36 is switched to the painting unit 3 side and the liquid feeding pump 34 is driven to feed the liquid paint to the painting unit 3. Further, at the time of stirring and defoaming, the liquid paint is circulated by switching the branch valve 36 to the bypass flow path 33 side and driving the liquid feed pump 34 (details will be described later).

  Next, with reference to FIG. 2, the stirring screw 23 which forms the core of the present invention will be described in detail. As described above, the stirring screw 23 includes the plurality of stirring blades 26 and the rotation shaft 41 that fixes the stirring blades 26 and serves as the rotation center of the stirring screw 23. The rotating shaft 41 extends in the vertical direction so that the tip is located near the bottom of the container 21, and is connected to the main shaft of the motor 24 directly or via a coupling. The rotating shaft 41 is preferably formed in a cylindrical shape in consideration of attachment of the stirring blade 26 and weight reduction. The plurality of stirring blades 26 are fixed so as to draw a spiral around the rotation shaft 41. More specifically, the eight agitating blades 26 are attached so as to be evenly arranged in the axial direction with respect to the rotating shaft 41 and evenly arranged in the circumferential direction (90 ° pitch) (FIG. 2A). )reference).

  Each stirring blade 26 is composed of two upper and lower blade plates 42 that are fixed at one end to the rotating shaft 41 and extend in the radial direction so as to be orthogonal to the rotating shaft 41. The two slats 42 are composed of an upper plate 43 and a lower plate 44 that face each other at a predetermined angle, and are each formed of a flat plate. The upper plate 43 and the lower plate 44 face each other so that the front part in the movement direction (rotation direction) is wide and the rear part is narrow in the cross-sectional direction. The liquid introduction part 45 is configured so as to be narrowed toward the rear in the direction). Further, the two blade plates 42 are disposed so as to be inclined so that the rear portion is obliquely upward as a whole so that the liquid paint that has flowed into the liquid introduction portion 45 by the rotation of the stirring screw 23 flows upward. . That is, the upper plate 43 is disposed with an angle (the front lowering with respect to the horizontal) that the rear portion is higher than the front portion in the moving direction, while the lower plate 44 is steeper than the inclination angle of the upper plate 43. They are arranged at an angle (see FIG. 2B). As a result, when the stirring blade 26 rotates (circular movement), a force for pushing the liquid paint upward acts, and the liquid paint in the container 21 generates convection that rises at the center and descends at the peripheral edge. Therefore, mixing of the pigment and the solvent (water) is promoted.

  Next, the stirring and defoaming operation by the stirring screw 23 (defoaming device 38) will be described. In this apparatus, the agitating screw 23 is rotated by the motor 24 to agitate and degas the liquid paint (details will be described later), and at the same time, the liquid feeding is performed while the branch valve 36 is switched to the bypass flow path 33 side. The pump 34 is driven to feed the liquid paint at the bottom of the container 21 to the top of the container 21 via the circulation channel 35 so that pigments that tend to precipitate can be mixed uniformly. That is, the defoaming operation of the liquid paint and the mixing operation (stirring operation) of the solvent and the pigment are performed simultaneously.

  When attention is paid to the stirring operation, when the stirring screw 23 is rotated, each stirring blade 26 takes in the liquid paint mixed with the bubbles b ahead of the rotation direction between the upper plate 43 and the lower plate 44. Since the liquid introduction part 45 is formed so that the stirring blade 26 is narrowed toward the rear in the rotation direction, the liquid paint mixed with the bubbles b is compressed as it moves rearward of the stirring blade 26. . Here, the bubbles b mixed in the liquid paint are aggregated (approached) with the compression in the liquid introduction part 45, and the bubbles b collide together to form a large bubble b. The enlarged bubble b increases buoyancy, and is released somewhat upward from the liquid introduction part 45 and floats. By repeating this, the bubbles b mixed in the liquid paint gradually become large bubbles b, and the buoyancy with respect to the liquid paint increases, and the bubbles b reaching the liquid level are defoamed by collapsing on the liquid level. Is done.

  According to the above configuration, when the liquid paint is agitated by the agitation screw 23, the bubbles b mixed in the liquid paint are aggregated in the liquid introduction part 45 and become large bubbles b by colliding with each other. It rises and collapses. Therefore, the bubbles b mixed in the liquid paint can be easily degassed only by the stirring operation that is normally performed so that the pigment and the solvent are uniformly mixed by the stirring screw 23. According to the test results, the time required for defoaming the liquid paint mixed with air bubbles b was about 12 hours (the same applies when stirring with a general stirring screw). When stirring with the screw 23, the required time was shortened to about 8 hours.

  Next, with reference to FIG. 3, the stirring screw 23 concerning 2nd Embodiment of this invention is demonstrated. Note that only parts different from the first embodiment are described in order to avoid repeated description. The stirring screw 23 according to the present embodiment replaces the blade plate 42 of the first embodiment with a plurality of cylindrical bodies 51 formed in a truncated cone shape and a rod for attaching the cylindrical bodies 51 to the rotary shaft 41. And a mounting member 52 having a shape.

  Each attachment member 52 is fixed so that one end thereof is orthogonal to the rotation shaft 41, and a cylindrical body 51 is attached to the other end. The four attachment members 52 are fixed so as to draw a spiral around the rotation shaft 41, and each attachment member 52 is evenly arranged in the axial direction with respect to the rotation shaft 41 and evenly arranged in the circumferential direction (90 °). (See FIG. 3A). The cylindrical body 51 is connected to the mounting member 52 so that the front portion in the movement direction (rotation direction) is wide and the rear portion is narrow in the cross-sectional direction, and the rear end portion has a plurality of discharges. It is closed by a perforated plate 54 having a hole 53. In addition, in the cross-sectional direction of the disposed cylindrical body 51, the upper bus bar located at the upper side is arranged with an angle that is higher at the rear than the front in the moving direction, so the lower bus bar located at the lower side Is steeper than the inclination angle of the upper bus (see FIG. 3B). Thereby, the convection of the liquid paint at the time of stirring is promoted. Further, as in the first embodiment, the bubbles b mixed in the liquid paint by this stirring are aggregated in the liquid introduction part 45, and the bubbles b repeatedly collide and coalesce to become large bubbles b on the liquid surface. Ascend and defoam. In particular, in the present embodiment, the bubbles b are aggregated in the introduction part 45, and further, the bubbles b are aggregated in the discharge hole 51, so that the bubbles b become larger and defoaming is promoted.

  According to the above configuration, as in the first embodiment, the bubble b mixed in the liquid paint can be easily defoamed only by the stirring operation that is normally performed so that the pigment and the solvent are uniformly mixed by the stirring screw 23. can do.

  The number and shape of the stirring blades 26 are not limited to those in the first and second embodiments as long as the bubbles b in the liquid paint can be efficiently aggregated. For example, the upper plate 43 and the lower plate 44 of the stirring blade 26 may be shaped to warp downward in the cross-sectional direction. Similarly, the tubular body 51 may be curved as a whole.

It is a schematic diagram of a coating system. It is a schematic diagram of the stirring screw which concerns on 1st Embodiment. It is a schematic diagram of the stirring screw which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Container 23 ... Agitation screw 24 ... Motor 26 ... Agitation blade 34 ... Liquid feed pump 35 ... Circulation flow path 38 ... Defoaming device 42 ... Blade plate 45 ... Liquid introduction part 51 ... Cylindrical body 54 ... Hole plate

Claims (14)

Using a stirring screw having a stirring blade that constitutes a liquid introduction part that becomes narrow toward the rear in the moving direction,
A method of defoaming a liquid paint, wherein the liquid paint mixed with bubbles is stirred by the stirring screw, and the bubbles are aggregated and floated in the liquid introduction part.   2. The method for defoaming a liquid paint according to claim 1, wherein the stirring blade is composed of two blade plates arranged to face each other.   2. The liquid paint defoaming method according to claim 1, wherein the stirring blade is formed of a cylindrical body.   The liquid paint defoaming method according to claim 3, wherein a rear end portion of the cylindrical body in a moving direction is closed with a perforated plate.   5. The liquid paint defoaming method according to claim 1, wherein the stirring blade is inclined so that a rear portion thereof is directed upward with respect to a moving direction. 6. A container for storing liquid paint;
A stirring screw immersed in a container;
A drive mechanism for rotating the stirring screw,
The said stirring screw has the stirring blade which comprised the liquid introduction part which becomes narrow toward the back of a moving direction, The defoaming apparatus of the liquid coating material characterized by the above-mentioned.   The defoaming device for liquid paint according to claim 6, wherein the stirring blade is composed of two blade plates arranged to face each other.   The liquid paint defoaming device according to claim 7, wherein the two blade plates are constituted by two flat plates arranged at the narrowing angle.   The liquid paint defoaming apparatus according to claim 6, wherein the stirring blade is formed of a cylindrical body.   10. The liquid paint defoaming apparatus according to claim 9, wherein the cylindrical body is formed in a truncated cone shape.   The defoaming device for a liquid paint according to claim 9 or 10, wherein a rear end portion of the cylindrical body in the moving direction is closed with a perforated plate.   The defoaming device for a liquid paint according to any one of claims 7 to 11, wherein the stirring blade is inclined so that a rear portion thereof is upward with respect to a moving direction.   13. The liquid paint defoaming device according to claim 7, wherein the stirring screw has a plurality of the stirring blades in a circumferential direction. A circulation channel communicating the bottom and the top of the container;
14. The circulation pump according to claim 6, further comprising a circulation pump that is interposed in the circulation channel and feeds liquid paint from the bottom of the container to the top of the container. Defoaming device for liquid paint.

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