JP2004066036A - Coating system for water-based paint - Google Patents

Abstract

An object of the present invention is to provide a coating system for water-based paint which can reduce the amount of curtain liquid used for a water curtain.
A super hydrophilic coating is applied to a curtain forming wall (20a) disposed at a position opposite to a spray nozzle (18) for spraying a work mist-like paint, with a work (14) conveyed inside a coating booth (12) therebetween. Even when the curtain liquid is supplied, a uniform and uninterrupted liquid film is formed on one surface of the curtain forming wall 20a to form the water curtain 20.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a coating system for water-based paint, and in particular, to reduce the amount of a curtain liquid used in a water curtain for collecting unpainted paint generated when a water-based paint is sprayed onto a work in the form of a mist and applied. It relates to the improvement of a coating system for water-based paints that can be made.
[0002]
[Prior art]
Conventionally, a work (object to be coated) is continuously transferred into a coating booth using a transfer means such as an overhead conveyor, and mist is sprayed on the transferred work using a paint spraying device (spray nozzle) or the like. 2. Description of the Related Art A coating system that performs a coating by spraying a shape of a coating is widely used. When paint is sprayed by such a spray nozzle, in the coating booth, mist-like uncoated paint floating in the coating booth is generated without being applied to the work. It is necessary to prevent the uncoated paint from leaking out of the painting booth or re-adhering to the work, and it is desired to reliably collect the unpainted paint.
[0003]
In recent years, it has been proposed to collect unpainted paint, perform reprocessing such as filtration as necessary, and use the regenerated paint again for painting. In this case, aggressive collection of uncoated paint is required. As a means for collecting uncoated paint, a method using an air filter or a water shower is generally used. For example, a water curtain method is effective as a method of efficiently collecting unpainted paint near the work actually being coated without affecting the work or the like. In the water curtain system, a liquid containing water as a main component (curtain liquid) is provided on a surface of a curtain forming wall (for example, a metal plate) installed on a side opposite to an injection nozzle with a work conveyed in a coating booth therebetween. To form a water curtain, the uncoated paint floating by the water curtain is involved, and the paint (uncoated paint) is introduced together with the curtain liquid to the lower part of the coating booth or an external water tank. The curtain liquid in the water tank is circulated again to a water curtain or the like. When the curtain liquid reaches a predetermined concentration due to the collected paint (uncoated paint), the concentrated liquid is used by a UF concentrator (filtration device) or the like. The concentrated liquid is separated into a (paint) and a filtrate, and after the toning, the concentrated liquid is reused as a regenerated paint for painting, and the filtrate is reused again as a curtain liquid or a washing liquid for a painting booth.
[0004]
[Problems to be solved by the invention]
However, in order to form a uniform water curtain without interruption on the wall of the coating booth and to make the water curtain function well, it is generally necessary to supply a curtain liquid of 100 liters or more per minute per 1 m width. is there. Although the size (length) of the painting booth varies depending on the size of the work and the number of works staying in the painting booth, a painting booth of about 10 to 13 m is generally required. Therefore, in order to form a good water curtain, 1000 to 1300 liters or more of curtain liquid (water) is required per minute. That is, a large capacity pump for supplying a curtain liquid of 1300 liters or more per minute is required. Further, for such a pump, the capacity of the supply tank of the curtain liquid to be used is required to be, for example, about 2.5 to 3 times in consideration of the residence time of the supply pipe system. That is, there is a problem that a supply tank of 3000 liters or more is required, and the equipment scale becomes enormous and the equipment cost increases.
[0005]
Further, when painting a work in such a painting booth, it may be necessary to change the color of the paint. In this case, the curtain liquid must be completely replaced to prevent color mixing of the recovered paint. For example, when performing color change between two colors, two spare tanks for color change are prepared, and all the curtain liquids used so far in the circulation system of the water curtain are transferred to the first spare tank. Thus, the curtain liquid in the second preliminary tank had to be transferred to the circulation tank and circulated for the water curtain. At this time, the used curtain liquid, which has been used in the water curtain circulation system, is completely concentrated by the UF concentrator to which the spare tank is connected, and is separated into a reusable concentration paint and filtrate.
[0006]
However, since the concentration processing time increases according to the amount of the curtain liquid to be transferred, when an enormous amount of the curtain liquid as described above is used, the concentration processing takes several hours, and the concentration processing is completed. Until then, there was a problem that the color could not be changed again. It suffices if the processing capacity of the UF concentrator can be increased, but increasing the capacity of the UF concentrator that is used only intermittently is not preferable in terms of equipment scale and cost. Since a commonly used UF concentrator is about 10 liters per minute, it takes 5 hours to perform 3000 liters of processing, during which time the color changing operation cannot be performed.
[0007]
The present invention has been made in view of the above-described conventional problems, and its purpose is to use a water curtain to collect unpainted paint generated when a water-based paint is sprayed onto a work in the form of a mist and painted. It is an object of the present invention to provide a coating system for a water-based paint that can reduce the amount of a curtain liquid used for a water curtain in a system to be performed. It is another object of the present invention to provide a water-based paint coating system capable of performing a color change operation in a short cycle.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a coating system for water-based paint that performs coating by spraying a water-based paint from an injection nozzle on a work to be conveyed in a coating booth. A curtain-forming wall that is disposed on the opposite side of the injection nozzle and that captures uncoated paint that has not been applied to the workpiece, and a liquid that supplies a curtain-forming liquid to the curtain-forming wall; And a supply unit, wherein a surface of the curtain forming wall is provided with a superhydrophilic coating.
[0009]
According to this configuration, by applying a superhydrophilic coating to the curtain forming wall of the water curtain, it becomes possible to form a uniform water film on the curtain forming wall even when supplying a very small amount of curtain liquid, Can be drastically reduced and unpainted paint that has collided with the water curtain can be collected as in the conventional case.
[0010]
In order to achieve the above object, the present invention is characterized in that, in the above configuration, the superhydrophilic coating is performed using a photocatalyst.
[0011]
It is known that the extent to which water is repelled on a material surface is determined by the contact angle between a water droplet and the material surface. When the surface of the substance is coated with a photocatalyst, the contact angle can be set to several tens of degrees, and finally can be reduced to almost 0 ° by irradiating light. In other words, it can be set to a state where water is not repelled at all. As a result, a uniform and uninterrupted thin water film can be formed by supplying a very small amount of curtain liquid to the curtain forming wall. Note that an oxide of titanium can be used as the photocatalyst, and it can be excited by ultraviolet light or visible light by partially changing the composition. Further, the degree of hydrophilicity can be continuously changed by changing the illuminance, irradiation amount, and the like of light.
[0012]
According to this configuration, the curtain forming wall can easily have the desired superhydrophilicity.
[0013]
In order to achieve the above object, according to the present invention, in the above configuration, the liquid supply unit includes a liquid circulation system that circulates a curtain forming liquid having a predetermined concentration or less after forming the water curtain to the curtain forming wall. And
[0014]
According to this configuration, a good water curtain can be formed with a small amount of curtain liquid.
[0015]
In order to achieve the above object, according to the present invention, in the above-described configuration, the liquid circulation system includes a filtration device that filters the curtain-forming liquid after the formation of the water curtain and discharges the filtrate, and supplies the discharged filtrate to the curtain-forming wall. It is characterized by circulating supply.
[0016]
According to this configuration, it is possible to always keep the concentration of the curtain liquid used for forming the water curtain constant. In other words, since the concentration of the water curtain and the concentration of the liquid passing through the liquid circulation system can be stabilized at a low concentration, it is possible to stabilize the collection efficiency and to prevent the liquid circulation system from being stained by paint. .
[0017]
In order to achieve the above object, according to the present invention, in the above configuration, the coating booth has a liquid storage portion for temporarily storing the curtain liquid after the formation of the water curtain on the booth bottom surface, and a back surface side of the curtain forming wall. An exhaust path having an exhaust fan for exhausting the atmosphere in the coating booth, and a minute gap is formed between the liquid level of the curtain liquid stored in the liquid storage part and the lower end of the curtain forming wall. In addition, a part of the uncoated paint floating in the coating booth is collected by a curtain liquid that is raised by the atmosphere in the coating booth passing through the minute gap.
[0018]
By forming the water curtain with a small amount of the curtain liquid by applying a superhydrophilic coating to the curtain forming wall, the curtain liquid is merely dripped at the lower end of the water curtain, and jumping up is eliminated. That is, it is impossible to expect the unpainted paint to be collected by the jumped-up curtain liquid. Therefore, a minute gap is formed between the liquid level of the curtain liquid stored in the liquid storage part and the lower end of the curtain forming wall, and the so-called minute gap is generated when the atmosphere in the painting booth is sucked from the exhaust path side by the exhaust fan. The curtain liquid stored in the liquid storage section is jumped up by the venturi effect. The unpainted paint can be collected by the splashing up of the liquid by the Benchery effect.
[0019]
Therefore, while the amount of the curtain liquid used for forming the water curtain is drastically reduced, it is possible to collect the uncoated paint as in the case where a large amount of the curtain liquid is used.
[0020]
In order to achieve the above object, the present invention is characterized in that, in the above configuration, a collection filter for collecting uncollected uncoated paint is disposed in the exhaust path.
[0021]
According to this configuration, the uncoated paint that could not be completely collected by the curtain liquid jumped up by the water curtain and the venturi effect is surely collected by the collection filter to prevent the paint from flowing outside. This can contribute to an increase in paint collection efficiency.
[0022]
In order to achieve the above object, according to the present invention, in the above-described configuration, the coating booth has an exhaust path for exhausting an atmosphere in the coating booth on the back side of the curtain forming wall, and the exhaust path is provided in the path. A collection filter that collects uncollected uncoated paint, an exhaust fan that exhausts the atmosphere in the coating booth through the collection filter, and washing or collection of the paint collected by the collection filter. A liquid supply unit for supplying a liquid for collecting uncoated paint floating around the collection filter from a lower surface side of the collection filter.
[0023]
According to this configuration, since the atmosphere in the painting booth can be directly sucked from the painting booth side to the exhaust path side, the exhaust can be efficiently exhausted even with a small exhaust fan, and the collection filter can efficiently remove the uncoated paint. Capture can be performed. Further, by collecting the paint (uncoated paint) in the liquid efficiently by supplying the liquid from the lower surface side of the collection filter in, for example, a mist state and washing the collection filter. be able to. In addition, since the ventilation state of the collection filter can be kept constant by washing, it is possible to stably collect the uncoated paint and stabilize the load of the exhaust fan. Further, by supplying the liquid from the lower surface of the collection filter, for example, in the form of a mist, it becomes possible to collect uncoated paint floating around the collection filter, thereby improving collection efficiency and collecting. The load on the filter and the exhaust fan can be reduced.
[0024]
In order to achieve the above object, the present invention is characterized in that, in the above configuration, the painting booth is provided with a superhydrophilic coating on the bottom surface of the booth.
[0025]
According to this configuration, even if the amount of the curtain liquid forming the water curtain is small, the curtain liquid that has collected the uncoated paint can be easily collected. In addition, it is possible to reduce contamination due to the paint in the painting booth, and it is easy to wash with color change.
[0026]
In order to achieve the above object, according to the present invention, in the above configuration, a curtain liquid supplied from a liquid supply unit is supplied onto the curtain forming wall on the curtain forming wall to form a uniform liquid film. It has a liquid film forming part.
[0027]
Here, the liquid film forming portion may be any as long as it can form a constant flow path of the curtain liquid with respect to the curtain forming wall, for example, a porous resin or sponge, a fiber or a non-woven cloth, or a fixed liquid. A metal plate or the like capable of forming the interval of.
[0028]
According to this configuration, it is possible to stably easily supply a small amount of curtain liquid to the curtain forming wall, and to form a good water curtain.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating an entire configuration of a water-based paint coating system (hereinafter, simply referred to as a coating system) 10 of the present embodiment. A coating booth 12 constituting the coating system 10 includes an overhead conveyor that suspends and sequentially conveys a workpiece 14 (eg, electrical product parts, automobile parts, construction materials, other various machine products, daily necessities, and the like) that is an object to be coated. 16 (hereinafter simply referred to as a conveyor). The work 14 is carried in from the back side of the paper, subjected to a coating process, and then carried out to the front side of the paper. On the side of the work 14 conveyed by the conveyor 16, a paint spray nozzle 18 for spraying the water-based paint in the form of a mist on the surface of the work 14 is arranged. The spray nozzle 18 can be moved in any direction of up, down, left, and right, and sprays paint on the entire surface of one side of the workpiece 14 being conveyed. By rotating the work 14 while the work 14 is being conveyed, or by turning the spray nozzle 18 upward or downward, the paint can be sprayed on the entire periphery of the work 14 and on the entire back surface, top surface, bottom surface, and the like. Further, a plurality of injection nozzles 18 may be arranged. The water-based paint is a water-soluble, water-dispersible, or emulsion paint that does not cure unless dried (for example, drying by applying a predetermined temperature or natural drying). In addition, depending on the water-based paint, there is a water-based recycled paint that can be recycled by collecting uncoated paint that has not been applied to the work 14 after being sprayed from the spray nozzle 18. The water-based recycled paint can be collected and collected by a liquid used in a water curtain or a water shower in the coating booth 12, and then separately concentrated, prepared, and reused. Hereinafter, in the present embodiment, the water-based paint refers to a water-based recycled paint. Of course, ordinary non-recyclable water-based paints can also be applied to the embodiments described below.
[0030]
As described above, when the coating is performed by the spray nozzle 18, there is a mist-like paint (uncoated paint) that is sprayed from the spray nozzle 18 and then floats inside the coating booth 12 without adhering to the work 14. The unpainted paint reattaches to the work 14 after the painting is completed and causes poor quality, or adheres to the conveyor 16 and the spray nozzle 18 inside the painting booth 12 and causes malfunction, and Must be removed as much as possible.
[0031]
In the coating system 10 of the present embodiment, a water curtain 20 that collects uncoated paint is formed at a position facing the injection nozzle 18 with the work 14 interposed therebetween. The water curtain 20 includes a curtain forming wall 20a disposed substantially vertically in the coating booth 12, and a liquid supply nozzle 20b for supplying a curtain liquid to the curtain forming wall 20a. The curtain forming wall 20a is made of a metal plate (for example, stainless steel) or resin having excellent corrosion resistance, and the curtain liquid is continuously flowed on the wall surface to form a water film, so that the water spread over the curtain forming wall 20a. A curtain 20 is formed. The curtain liquid contains water as a main component, mist-like uncoated paint is involved, and falls down along the curtain forming wall 20a. In the case of the present embodiment, an airflow generated by an exhaust fan, which will be described later, forms an airflow in the coating booth 12, guides the mist-like uncoated paint, and efficiently collides with the water curtain 20.
[0032]
An exhaust path 22 for exhausting the atmosphere (air) in the painting area of the painting booth 12 is formed on the back side of the water curtain 20 of the painting booth 12. An exhaust fan 24 is provided near the outlet of the exhaust path 22, and a collection filter 26 is disposed upstream of the exhaust fan 24. By forcibly exhausting the air by the exhaust fan 24, an airflow is generated in the coating booth 12, causing the uncoated paint to collide with the water curtain 20 and the mist-like uncoated paint that cannot be completely collected by the water curtain 20. The coating material is guided to the collection filter 26 and collected. In addition, a baffle plate 28 may be arranged, for example, in a zigzag manner on the upstream side of the collection filter 26 (the inlet side of the exhaust path 22) in order to reduce the load on the collection filter 26. In this case, a part of the uncoated paint is also collected on the baffle plate 28, and can be recovered later when washed with a washing liquid (for example, a filtrate described later) or the like.
[0033]
The characteristic feature of the present embodiment is that a super-hydrophilic coating is applied to the surface of the curtain forming wall 20a forming the water curtain 20 to form a very thin uniform water film on the curtain forming wall 20a. As a result, the water curtain 20 is being formed with a small amount of curtain liquid.
[0034]
The superhydrophilic coating can be performed, for example, using a photocatalyst. It is known that the extent to which water is repelled on a material surface is determined by the contact angle between a water droplet and the material surface. When a photocatalyst is coated, the contact angle can be made several tens of degrees, and finally can be made almost 0 ° by irradiating with light to excite. In other words, it can be set to a state where water is not repelled at all. As a result, a uniform and uninterrupted thin water film can be formed by supplying a very small amount of curtain liquid to the curtain forming wall. Note that an oxide of titanium can be used as the photocatalyst. In addition, by partially changing the composition, it can be excited by ultraviolet light or excited by visible light. Further, the degree of hydrophilicity can be continuously changed by changing the illuminance, irradiation amount, and the like of light, and the relationship between the supply amount of the curtain liquid of the water curtain 20 and the relationship can be arbitrarily changed.
[0035]
Conventionally, in order to form a water curtain that functions well for collecting uncoated paint floating in the coating booth 12, it is necessary to supply a curtain liquid of 100 liters or more per minute per 1 m width. This is because, when a curtain liquid is caused to flow on a curtain-forming wall that is not coated with a superhydrophilic coating, water repelling occurs on the curtain-forming wall and the water curtain does not spread over the entire surface or cracks are generated. A predetermined flow rate had to be secured to counteract the effect. However, by applying a superhydrophilic coating to the curtain forming wall 20a as in the present embodiment, water repelling of the curtain liquid is prevented, and 0.5 to 1.0 liters of the curtain liquid per minute per 1 m width is used. Even with the supply, a thin and stable water film can be formed on one surface of the curtain forming wall 20a. That is, the amount of curtain liquid required for forming the water curtain 20 can be drastically reduced.
[0036]
In the present embodiment, when a photocatalyst is used for the superhydrophilic coating, a lamp 30 for catalyst excitation is arranged near the curtain forming wall 20a in order to make the photocatalyst function well. It is desirable that the lamp 30 has an irradiation range covering the entire surface of the curtain forming wall 20a. Of course, the irradiation range may be secured by a plurality of lamps 30. When the photocatalyst is of a type that is excited by ultraviolet rays, for example, a mercury lamp, a metal halide lamp, a xenon lamp, an excimer laser, or the like can be used as the lamp 30. In the case of a type that is excited by visible light, any visible light lamp can be used.
[0037]
As described above, when the amount of curtain liquid required for forming the water curtain 20 can be drastically reduced, the capacity of a supply tank for supplying the curtain liquid to the water curtain 20 can be reduced. At the same time, the pump capacity for sending out the curtain liquid can be reduced. Hereinafter, the overall configuration including the liquid circulation system shown in FIG. 1 and the collecting operation will be described. In FIG. 1, a system in which the paint color can be changed between two colors according to the work 14 will be described as an example.
[0038]
As shown in FIG. 1, a liquid storage 32 is formed at the bottom of the coating booth 12 so that the curtain water used in the water curtain 20 can flow in and be temporarily stored. As is clear from FIG. 1, the liquid storage portion 32 is formed on the bottom surface of the coating booth 12 that is inclined downward toward the water curtain 20. The liquid storage section 32 has an overflow drainage section 32a at the left end in order to always keep the liquid level of the used curtain liquid increased by the formation of the water curtain. Here, the liquid level of the curtain liquid stored in the liquid storage section 32 is adjusted by the operation of the drain section 32a so as to form a minute gap (for example, 30 mm) 33 with the lower end of the curtain forming wall 20a. Has been adjusted.
[0039]
By the way, usually, in the case of the conventional method of forming a water curtain using a large amount of curtain liquid, the liquid jumps up during dropping of the curtain liquid or at the time of landing. It was possible to expect the unpainted paint in the coating booth 12 to be collected by the flip-up. However, in the present embodiment, since the amount of the curtain liquid forming the water curtain 20 has been drastically reduced, it is not possible to expect the liquid to jump up during dropping or landing. Therefore, in the present embodiment, as described above, the gap between the liquid surface of the curtain liquid stored in the liquid storage portion 32 and the lower end of the curtain forming wall 20a is set to be the minute gap 33, and from the exhaust path 22 side The atmosphere inside the coating booth 12 is sucked by the exhaust fan 24. When the atmosphere passes through the minute gap 33 at high speed, the curtain liquid jumps up on the exhaust path 22 side due to the so-called Ventelli effect. Since the atmosphere passing through the minute gap 33 contains uncoated paint that could not be collected by the water curtain 20, the uncoated paint that passed through the minute gap 33 due to the jumping-up of the curtain liquid due to the venturi effect. The paint can be collected. That is, as in the case where a large amount of curtain liquid is used, the uncoated paint can be taken into the liquid storing section 32. Of course, as described above, the collection by the collection filter 26 and the baffle plate 28 is also performed.
[0040]
Next, circulation of the curtain liquid accompanying the use of the water curtain 20 will be described. As described above, the curtain liquid used in the water curtain 20 is sequentially dropped and stored in the liquid storage unit 32. Then, the curtain liquid that has overflowed the liquid storage section 32 always flows into the circulation tank 34a (or 34b) from the drain section 32a. As described above, in FIG. 1, two liquid circulation systems are prepared in order to enable color change between two colors. In the present embodiment, two identical liquid circulation systems are shown, and are distinguished by subscripts “a” and “b”. Since the functions and operations of each circulatory system are the same, the following description will focus on one circulatory system with a suffix 'a'.
[0041]
The curtain liquid overflowing the liquid storage section 32 and discharged from the drain section 32a, and the curtain liquid discharged by releasing the cock 36 of the liquid storage section 32 during color change, are selected by switching the three-way valve 37. 34a (or 34b). The concentration of the curtain liquid flowing into the circulation tank 34a (or 34b) is slightly increased by collecting uncoated paint in the coating booth 12. As long as no extreme increase in concentration occurs, the water curtain 20 may be circulated for use. However, in this embodiment, a UF concentrator (filtration device) is used to keep the concentration of the curtain liquid constant. 38a. A pump 40a is disposed in the circulation tank 34a, and the curtain liquid constantly circulates between the circulation tank 34a and the UF concentrator 38a. Then, the filtrate generated at this time is transferred to the filtrate storage tank 42a. By arranging the UF concentrating device 38a in this manner, the concentration of the curtain liquid used for forming the water curtain 20 can always be kept constant. As a result, it is possible to stabilize the concentration of the water curtain and the concentration of the liquid passing through the liquid circulation system at a low concentration, thereby stabilizing the collection efficiency and preventing the liquid circulation system from being stained by paint. Can be.
[0042]
Note that the filtration performed by the UF concentrator 38a is not filtration for regenerating the paint, but for maintaining the circulating curtain liquid at a certain concentration or less, and therefore does not require high filtration capability. The curtain liquid having a certain concentration or less transferred to the filtrate storage tank 42a is sent to the liquid supply nozzle 20b arranged at the upper end of the curtain forming wall 20a by the pump 44a, and is used again for forming the water curtain 20. The curtain liquid transferred from the filtrate storage tank 42b for another color can be supplied to the liquid supply nozzle 20b by switching the three-way valve 46.
[0043]
On the other hand, when the color of the paint is changed, or when the curtain liquid in the circulation tank 34a exceeds a predetermined concentration, the pump 48a operates, and the entire amount of the curtain liquid in the circulation tank 34a is transferred to the liquid concentration tank of the paint recovery system 50a. Transfer to 52a. The liquid concentrating tank 52a is connected to a UF concentrating device 56a via a circulation pump 54a, and performs concentration of the curtain liquid. The filtrate generated at this time is sent to a filtrate tank 58a, and is used as a cleaning liquid for cleaning the collection filter 26 and the baffle plate 28 arranged in the exhaust path 22 of the coating booth 12 via a pump 60a at a predetermined timing. Then, the collected paint is transferred to the liquid storage unit 32 (indicated by the symbol C). In addition, a part of the filtrate in the filtrate tank 58a is returned to the circulation tank 34a, and is reused as a curtain liquid (indicated by reference numerals Da and Db).
[0044]
Further, the concentrated liquid concentrated to a predetermined concentration in the liquid concentration tank 52a is transferred to the paint tank 64a by the pump 62a as a regenerated paint after toning, and is used again for painting. The paint in the paint tank 64a or the paint in the paint tank 64b is supplied to the injection nozzle 18 at a predetermined timing and used by switching the three-way valve 66 (indicated by Ea and Eb).
[0045]
As described above, the uncoated paint collected by the water curtain 20, the collection filter 26, the baffle plate 28, and the like is subjected to the concentration treatment by the paint collection systems 50a and 50b, and becomes usable. As described above, by applying the superhydrophilic coating to the curtain forming wall 20a, the total amount of the curtain liquid flowing through the circulation system including the water curtain 20 can be drastically reduced. As a result, the total amount of the curtain liquid that is transferred from the circulation tank 34a or the circulation tank 34b to the paint recovery system 50a (or 50b) at the time of color change of the paint and needs to be subjected to the concentration treatment is drastically reduced. For example, the total amount of the curtain liquid to be processed can be reduced to 1/100 to 1/200 of a conventional equivalent system without a superhydrophilic coating, so that the processing time at the time of color change can be reduced. That is, for example, even if the first color needs to be changed again after the color change from the first color to the second color, the concentration processing of the first color has been completed, so that the concentration processing has an effect. Color change work can be performed quickly.
[0046]
FIG. 2 shows another embodiment of the coating booth 12 in which the curtain forming wall 20a is provided with a superhydrophilic coating. In the example of FIG. 2, for simplicity of description, the circulation system of the curtain liquid and the like connected to the coating booth 12 shows one system, that is, a system that does not consider the color change, but is similar to FIG. A plurality of systems may be provided in consideration of color change. 2 having the same functions as those of the circulating system in FIG. 1 are denoted by the same reference numerals except for the suffixes (a, b, etc.), and description thereof is omitted. I do.
[0047]
A feature of the coating booth 12 in FIG. 2 is that a large gap 70 is secured between the liquid level of the liquid storage portion 32 on the bottom surface of the coating booth 12 and the lower end of the curtain forming wall 20a. That is, in the portion of the gap 70, as shown in FIG. 1, the curtain liquid does not jump up due to the venturi effect, and the uncoated paint that cannot be completely collected by the water curtain 20 is located near the inlet of the exhaust passage 22. The operation is performed only by the provided collection filter 26. With such a configuration, it is not necessary to increase the capacity of the exhaust fan 24 so that the venturi effect is generated as shown in FIG. 1, and efficient collection can be performed by the small exhaust fan 24. Further, since the collection of the unpainted paint is completed near the entrance of the exhaust passage 22, it is not necessary to provide the baffle plate 28 as in the structure of FIG. 1, so that the entire structure of the coating booth 12 is simplified. can do. Further, in the case of performing exhaustion strong enough to generate the venturi effect as shown in FIG. 1, there is a possibility that a part of the uncoated paint may pass through the collection filter 26, but as shown in FIG. If the required capacity of the coating 24 can be reduced, the collection rate of the uncoated paint can be improved without the above-mentioned concerns.
[0048]
In this case, since the collection load of the collection filter 26 increases, it is desirable to wash the collection filter 26 (collect the collected uncoated paint in the liquid storage unit 32) frequently or constantly. At this time, by washing the collection filter 26 from the lower surface side of the collection filter 26, the collected paint (uncoated paint) can be efficiently collected in the liquid. By cleaning the collection filter 26 from the lower surface, the ventilation state of the collection filter 26 can be maintained constant, so that it is possible to stably collect uncoated paint and stabilize the load on the exhaust fan. it can. This lower surface cleaning can be performed, for example, by using a very small amount of liquid (for example, a filtrate) using the minute spray nozzle 72 or the like. At this time, it is desirable to spray uniformly on almost the entire lower surface of the collection filter 26. It is preferable that the filtrate to be supplied to the fine spray nozzle 72 is always supplied from the filtrate storage tank 42 via the switching valve 74. For example, when the load of the exhaust fan 24 is detected and the load exceeds a predetermined value, When it is detected that the filter 26 needs to be cleaned, the switching valve 74 may be opened to perform the cleaning. Of course, manual switching may be performed by an administrator.
[0049]
In this way, by supplying the filtrate from the lower surface of the collection filter 26 in the form of a mist by the fine spray nozzle 72, it is possible to collect the uncoated paint floating around the collection filter 26. become. As a result, the collection efficiency of the uncoated paint can be improved, and the load on the collection filter 26 and the exhaust fan 24 can be reduced. In FIG. 2, the inclination of the liquid storage portion 32 is opposite to that in FIG. 1, but only a structural variation is shown.
[0050]
In addition, not only the collection filter 26 but also the wall of the exhaust path 22 in front of the collection filter 26 may be cleaned by the fine spray nozzle.
[0051]
FIG. 3 shows still another structural variation of the painting booth 12. The basic configuration of the example in FIG. 3 is similar to that shown in FIG. 2, and the same reference numerals are given to the same functional parts, and the description thereof will be omitted. A characteristic of the coating booth 12 in FIG. 3 is that the surface of the inclined bottom surface 12a of the coating booth 12 is also coated with a superhydrophilic coating. Also in this case, a photocatalyst or the like can be used. In this case, the curtain liquid discharged from the water curtain 20 and the cleaning liquid for cleaning the collection filter 26 (equivalent to the curtain liquid) flow along the slope while containing the collected uncoated paint. There is no need to worry about remaining uncoated paint. Therefore, it is not necessary to form a liquid storage portion. In other words, the used curtain liquid or the like can be directly charged into the circulation tank 34, which simplifies the structure and reduces the amount of stopping in the circulation system (for the liquid storage part). A further reduction in the overall curtain liquid requirement can be achieved.
[0052]
As described above, by applying the superhydrophilic coating also to the surface of the bottom surface 12a, even if the amount of the curtain liquid forming the water curtain is small, it is possible to easily collect the curtain liquid that has collected the uncoated paint. . In addition, it is possible to reduce contamination due to the paint in the painting booth, and it is also possible to easily carry out washing for changing colors.
[0053]
By the way, as described above, the curtain liquid to be supplied to the curtain-forming wall 20a provided with the superhydrophilic coating supplies a necessary minimum amount uniformly and continuously over the entire width of the curtain-forming wall 20a, and a thin liquid film is formed. Need to be formed.
[0054]
Therefore, in the present embodiment, as shown in FIGS. 4A and 4B, near the upper end of the curtain forming wall 20a, a curtain liquid supply pipe (liquid supply nozzle 20b) 76 and the supply pipe are provided. Liquid film forming portions 78a and 78b for supplying the supplied curtain liquid as a uniform liquid film onto the curtain forming wall 20a are arranged. In the supply pipe 76, for example, a plurality of holes 76a are formed at predetermined intervals in a pipe arranged along the width direction of the curtain forming wall 20a, and an appropriate amount of curtain liquid is dripped with curtain liquid. Further, the liquid film forming portion 78a may be any as long as it can form a constant flow path of the curtain liquid with respect to the curtain forming wall 20a. For example, a porous resin, sponge, fiber, non-woven cloth, or a fixed A metal plate or the like capable of forming an interval can be used. In the case of a porous resin, sponge, fiber or non-woven cloth, as shown in FIGS. 4 (a) and 4 (b), it is preferable to dispose it by pressing it against the curtain forming wall 20a. In this case, stable outflow of the curtain liquid can be performed without performing fine adjustment. In addition, a metal plate, a resin plate, or the like is arranged so as to have a slight interval so that the curtain liquid seeps out. In this case, fine adjustment of the flow rate is required, but the configuration can be simplified, which can contribute to cost reduction and the like. In any of these cases, the curtain liquid supplied from the supply pipe 76 is held in front of the temporary liquid film forming portions 78a and 78b, so that a uniform amount of curtain liquid can be supplied without interruption. it can.
[0055]
As described above, the water curtain 20 arranged in the painting booth 12 is arranged near the work conveyed in the painting booth 12. When forming a water curtain by supplying a curtain liquid of 100 liters or more per minute per 1 m width of the water curtain as in the prior art, the distance between the water curtain and the work is defined as For example, it was necessary to secure 1000 mm or more. However, as shown in the present embodiment, by applying the superhydrophilic coating to the curtain forming wall 20a of the water curtain 20, only an extremely thin water film is formed on the surface of the curtain forming wall 20a. No water splash like this occurs. That is, the distance between the work 14 and the water curtain 20 can be reduced (for example, about 300 mm). As a result, the painting booth 12 can be reduced in size, that is, the equipment can be reduced in size. Further, since the distance between the work 14 and the water curtain 20 is short, uncoated paint that has not been applied to the work 14 collides with the water curtain 20 immediately behind the work 14 and is collected by the water curtain 20. In addition, the collection efficiency of the water curtain 20 can be improved, and the floating rate of uncoated paint in the coating booth 12 can be reduced.
[0056]
In this embodiment, the super hydrophilic coating is applied to the curtain forming wall 20a or the like for the purpose of collecting unpainted paint. It may be a purpose. In this case, by performing intermittent washing with a shower or the like, it is possible to easily prevent contamination by the paint adhered in the coating booth 12 and to perform maintenance easily. In addition, since the supply of the curtain liquid is stopped after the completion of the painting operation of the water curtain 20, the curtain liquid containing several percent uncoated paint may remain on the curtain forming wall 20a. Due to the self-cleaning action of the present invention, the next time the curtain liquid is supplied, it is possible to eliminate the residue and to easily perform maintenance of the curtain forming wall 20a. In particular, even when the color change is performed while the painting operation is stopped (the next operation is several hours later, for example, the next day), the residue of the previous color is quickly removed, and the painting operation of the next color is performed. be able to.
[0057]
Further, the configuration of the coating booth 12 and the configuration of the liquid circulation system shown in the present embodiment are merely examples, and the configuration in which the curtain forming wall 20a of the water curtain 20 is coated with a superhydrophilic coating to reduce the amount of the curtain liquid used. If it is, it can be changed appropriately, and the same effect as that of the present embodiment can be obtained. For example, even if a fresh curtain liquid is always supplied without circulating the curtain liquid, the amount of the curtain liquid used can be reduced, and the operating cost can be reduced.
[0058]
【The invention's effect】
As described above, according to the present invention, by applying a superhydrophilic coating to the curtain forming wall of a water curtain, it is possible to form a uniform water film on the curtain forming wall even when supplying a very small amount of curtain liquid. This makes it possible to drastically reduce the amount of curtain liquid used, and to collect uncoated paint that has collided with the water curtain as in the conventional case.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration of a coating system for a water-based paint according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating another configuration of a coating booth of the coating system for a water-based paint according to the embodiment of the present invention.
FIG. 3 is an explanatory diagram illustrating another configuration of a coating booth of the coating system for a water-based paint according to the embodiment of the present invention.
FIG. 4 is an explanatory diagram illustrating a form of supplying a curtain liquid to a curtain forming wall of the coating system for aqueous paint according to the embodiment of the present invention.
[Explanation of symbols]
Reference Signs List 10 coating system, 12 coating booth, 12a bottom surface, 14 work, 16 conveyor, 18 injection nozzle, 20 water curtain, 20a curtain forming wall, 20b liquid supply nozzle, 22 exhaust path, 24 exhaust fan, 26 collection filter, 28 obstruction Plate, 30 lamps, 32 liquid storage, 32a drainage, 33 minute gap, 34, 34a, 34b circulation tank, 34a concentrator, 36 cock, 37 three-way valve, 38a UF concentrator, 40a pump, 42, 42a, 42b Filtrate storage tank, 44a, 48a pump, 46, 66 three-way valve, 50a paint collection system, 52a liquid concentrating tank, 54a circulation pump, 56a UF concentrator, 58a filtrate tank, 60a pump, 62a pump, 64a paint tank, 64b
Paint tank.

Claims (9)

A coating system for water-based paint that sprays water-based paint from a spray nozzle onto a workpiece conveyed in a coating booth,
A curtain forming wall that is arranged at least on the opposite side of the spray nozzle with the work conveyed therebetween, and forms a water curtain that collects uncoated paint that has not been applied to the work,
A liquid supply unit that supplies a curtain forming liquid to the curtain forming wall,
Including
A water-based paint coating system, wherein a surface of the curtain forming wall is provided with a superhydrophilic coating. The system according to claim 1,
The coating system for water-based paints, wherein the superhydrophilic coating is performed using a photocatalyst. In the system according to claim 1 or 2,
The coating system for water-based paint, wherein the liquid supply unit includes a liquid circulation system that circulates a curtain forming liquid having a predetermined concentration or less after forming the water curtain to the curtain forming wall. In the system according to any one of claims 1 to 3,
The coating system for water-based paint, wherein the liquid circulation system includes a filtration device that filters the curtain-forming liquid after forming the water curtain and discharges the filtrate, and circulates and supplies the discharged filtrate to the curtain-forming wall. In the system according to any one of claims 1 to 4,
The painting booth is
A liquid storage unit for temporarily storing the curtain liquid after the formation of the water curtain on the booth bottom surface,
An exhaust path formed on the back side of the curtain forming wall and having an exhaust fan for exhausting the atmosphere in the coating booth,
Including
A minute gap is formed between the liquid level of the curtain liquid stored in the liquid storage section and the lower end of the curtain forming wall, and the inside of the coating booth that passes through the minute gap floats in the coating booth by the curtain liquid that rises. A coating system for water-based paint, wherein a part of unpainted paint is collected. The system according to claim 5,
A coating system for water-based paint, wherein a collection filter for collecting uncollected uncoated paint is disposed in the exhaust path. In the system according to any one of claims 1 to 4,
The painting booth is
On the back side of the curtain forming wall, there is an exhaust path for exhausting the atmosphere in the coating booth,
The exhaust path is
A collection filter for collecting uncollected uncoated paint in the path;
An exhaust fan that exhausts the atmosphere in the coating booth via the collection filter;
A liquid supply unit for supplying a liquid for washing and collecting the paint collected by the collection filter or collecting uncoated paint floating around the collection filter from the lower surface side of the collection filter,
A coating system for water-based paint, comprising: The system according to claim 7,
The painting booth is
A coating system for water-based paints, characterized in that a super hydrophilic coating is applied to the booth bottom. The system according to any one of claims 1 to 8,
A coating system for water-based paint, comprising a liquid film forming unit that supplies a curtain liquid supplied from a liquid supply unit onto the curtain forming wall to form a uniform liquid film on an upper part of the curtain forming wall. .

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