JP2005125273A - Treating method and device of over-spray coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently treating an over-spray coating generated in a coating using an aqueous coating and a treating device therefor. <P>SOLUTION: The method for treating the over-spray coating comprises spray-coating with the aqueous coating in a coating booth, catching the over-spray coating, which has not adhered to a material to be coated, by an aqueous medium and recovering it as a booth water, obtaining a condensate of a solid component contained in the over-spray coating by filtering the booth water with an ultrafilter in a batchwise manner and recovering for disposing of the condensate. The solid content of the condensate is 45-53 wt.%. The apparatus for the method is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for treating overspray paint, and more particularly to a method for treating booth water comprising overspray paint resulting from painting with aqueous paint. Furthermore, this invention relates to the processing apparatus used suitably in order to implement such a processing method.

  At present, water-based paints are easy to handle because the medium is mainly water, and there are fewer problems such as air pollution than organic solvents. Many water-based paints are used to paint products.

  In a general painting method, the object to be coated is applied with a water-based paint by a spray gun in a painting booth, and the overspray paint that is not attached to the object to be coated is captured by an aqueous medium such as a water curtain. The aqueous medium that has captured the overspray paint is stored as booth water at the bottom of the painting booth (see, for example, Patent Document 1).

  Since the stored booth water is circulated and used again during painting, a water curtain is formed again, so that overspray paint, substantially solids contained in the overspray paint accumulates in the booth water. Therefore, it is necessary to periodically remove this solid content from the booth water. For example, ions from the booth chemicals or miscellaneous ions such as chlorine ions in tap water used for the booth water accumulate. Needs to be updated regularly.

  For example, the solid content of the overspray paint contained in the booth water is removed from the booth water by coagulation separation. In this method, in a large pit or sedimentation tank, a flocculant or the like is added as necessary to perform sedimentation separation or flotation separation, and then subjected to centrifugation to separate into a solid content and an aqueous medium. Yes. The aqueous medium is reused as booth water, and the collected solid content is reused as a recycled paint by preparing it. However, since the paint which is a toned product has a large number of primary colors, it is difficult to adjust the color, and additional processing is required to recycle the collected solid content for each color. Further, when the collected solid content is reused, it is necessary to manage the booth water so as not to adversely affect the solid content used as the recycled paint, which is not satisfactory in terms of cost.

  A method called an electrolytic levitation method (see, for example, Patent Document 2 and Patent Document 3) has also been proposed, and by causing an aluminum electrode disposed in booth water to be energized, aluminum is dissolved in the booth water, and is thereby generated. Adopts the principle that the aluminum spray causes the overspray paint, substantially solids contained in the overspray paint and the above-mentioned miscellaneous ions to agglomerate, and that the agglomerate floats and is separated by bubbles generated from the aluminum electrode. doing. However, if the solid content adheres to the aluminum electrode and is energized continuously, there is a problem that the ionization of aluminum is hindered by the solid content.

Japanese Patent Application Laid-Open No. 2002-079154 Japanese Patent Laid-Open No. 11-114304 JP 2003-2111166 A

  Therefore, an object of the present invention is to provide an overspray paint, more specifically, an efficient treatment method for solids contained in such paint and an apparatus therefor.

In order to solve the above problems, the present invention provides:
Spray water-based paint at the painting booth,
Capturing overspray paint that has not been applied to the substrate with an aqueous medium and collecting it as booth water,
Filtering the booth water batchwise using an ultrafilter to obtain a concentrate enriched in solids contained in the overspray paint, and recovering the concentrate for disposal An overspray processing method comprising:
A method is provided wherein the solids content of the concentrate is between 45 wt% and 53 wt%.

The present invention also provides an apparatus for treating booth water comprising overspray paint. The device
A storage tank for storing the booth water;
An ultrafilter for concentrating the booth water,
Means for discharging the concentrate concentrated in the overspray paint obtained by filtration of the booth water for processing, and a line for returning the residue from which the filtrate has been removed by filtration to the storage tank; Have.

  In the overspray paint processing method and processing apparatus of the present invention, the concentrate obtained is disposed as waste, so that the processing required to reuse the concentrate as a recycled paint is not required, and the entire coating system is The initial cost and running cost can be reduced, and therefore, the overspray paint generated by painting, more specifically, the solid content contained in such paint can be efficiently processed.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, as one embodiment, a method and an apparatus for treating an overspray paint of the present invention will be described.

  In the present invention, the “water-based paint” is a paint containing a solid content and an aqueous medium, and is a paint widely used for general painting, and is concentrated using an ultrafilter. It is a paint that can be used. Alternatively, it may be a paint that can be reused from a concentrate obtained by concentrating solids contained in the overspray paint. The aqueous medium generally contains water as a main component, but may contain other components such as a hydrophilic organic solvent. The solid content is, for example, a resin for forming a coating film, a pigment incorporated into the coating film, and the like, and may contain other components as much as possible by concentration as described below by filtration.

  In the present invention, the “aqueous medium” that captures the overspray paint is a medium that captures the aqueous paint that has not been applied to the object to be coated, and is mainly composed of water, such as tap water or industrial water. is there. If necessary, other components such as amines may be contained. In painting, such an aqueous medium is recycled in the painting booth. That is, the aqueous medium captures the overspray paint as a water curtain, is stored as booth water together with the overspray paint, and is repeatedly used as a water curtain again. Thus, the “aqueous medium” that captures the overspray paint is essentially also the booth water circulating in the paint booth.

  In the present invention, “booth water” is generated when an aqueous medium captures overspray paint in a painting booth. Therefore, the “booth water” is a liquid material in which an overspray coating material containing a solid content is diluted with an aqueous medium, and is substantially included in the solid content of the overspray coating material and the aqueous coating material. It comprises an aqueous medium and an aqueous medium used to capture overspray paint.

  In the present invention, the booth water comprising the solid content of the overspray paint is treated by being filtered. In such filtration, the aqueous medium originally contained in the overspray paint and a part of the aqueous medium used for capturing the overspray paint are removed as a filtrate. Can be obtained.

  In addition, it is preferable that this booth water is filtered by a batch type. In this batch system, by repeatedly filtering, the aqueous medium originally contained in the aqueous paint and the aqueous medium used to capture the overspray paint are gradually removed from the booth water as a filtrate. A concentrate in which solid contents such as pigments are concentrated can be obtained. Therefore, the “concentrate” means that the aqueous medium originally used in the aqueous paint and the aqueous medium used to capture the overspray paint are filtrated by filtering the booth water, preferably by batch-type filtration. As a residue after partly removed from the booth water, if the solids such as resin and pigments originally contained in the overspray paint were contained in the booth water before filtration Means more concentrated. The “concentrate” may be liquid or slurry in the order of decreasing solid content.

  In the present invention, the concentrate in which the solid content contained in such an overspray paint is concentrated is treated as waste without being reused. Therefore, the treatment required in the prior art coagulation separation or the like becomes unnecessary, and the effect of facilitating handling of the booth water is brought about.

  Specifically, since the concentrate is not reused as a recycled paint, the management range of solid content and miscellaneous ions contained in the booth water or the pH of the booth water is widened, and management of the booth water is considerably facilitated. At the same time, it is not necessary to control the temperature of the concentrate as in the prior art, and it is not necessary to add a function for reuse to the water-based paint in advance when designing the paint. Furthermore, the present invention does not require a relatively large sedimentation tank required for coagulation separation and the like, and instead uses a relatively small filter, so that the processing apparatus, and thus the entire coating system, can be made compact. it can.

  Further, there is no need to add a flocculant to booth water as in the prior art, and in addition, the aqueous medium in the concentrate is treated with the disposal of the concentrate, so that the miscellaneous ions contained in the aqueous medium are removed. Will be removed. Therefore, the ratio (namely, accumulation speed) in which miscellaneous ions accumulate in the booth water repeatedly used decreases, and as a result, the effect of reducing the renewal frequency of the booth water is also brought about.

  In the treatment method of the present invention, the obtained filtrate can be reused as booth water, but this filtrate can also be used for cleaning, for example, a scrubber part in the painting booth, so the inside of the painting booth is cleaned. Can be maintained, and maintenance becomes easy.

  Here, the disposal of the concentrate means that it is treated as waste as described above, used as dissolved slag, or recovered as heat as liquid fuel. Specifically, the concentrate obtained in the present invention can be incinerated by an incinerator such as a kiln. Moreover, the incinerated ash obtained can be disposed of in landfills, and can also be used as dissolved slag or cement paint. If the concentrate is in liquid form, it falls under the category of “waste oil” in the category of industrial waste. Therefore, the concentrate is managed by the industrial waste management slip (manifest), and the general “waste treatment method” Is generally transported and disposed of. On the other hand, the liquid concentrate can be recovered as heat by using it as a liquid fuel, for example, as a fuel for a boiler or cogeneration.

As the solids content increases, the concentrate cannot be easily handled as a liquid or slurry due to the increased viscosity. Moreover, when solid content becomes still higher, a concentrate will disperse | distribute as a powder body at the time of incineration, and will cause the fall of incineration efficiency. On the other hand, if the solid content of the concentrate is too low, the amount of discharge increases and the economic efficiency deteriorates. Accordingly, the solids content of the concentrate is 40 wt% to 60 wt%, more preferably 45 wt% to 53 wt%. The solid content is a ratio to the solid content present in the concentrate. The obtained concentrate is left in a drying chamber at about 105 ° C. for about 3 hours, and then the weight W2 is concentrated after being left as it is. Measured by determining the ratio to the object weight W1:
Solid content (% by weight) = W2 / W1 × 100.

  FIG. 1 schematically shows a coating system having a processing device 12 of the present invention. The overspray paint processing method and processing apparatus of the present invention will be described below with reference to FIG.

  The coating system of FIG. 1 includes a coating booth 1 for coating an object 3 and a processing apparatus 12 of the present invention. The painting booth 1 includes a spray gun 2, a water curtain 4, a booth water tank 6, a booth water circulation pump 7, a scrubber unit 11, and the like. The processing apparatus 12 of the present invention includes a storage tank 13 for storing booth water to be processed, a concentration pump 14 for supplying booth water to be processed to a filter, a strainer 15 for removing dust contained in the booth water to be processed, A filter 16 for filtering the booth water to be treated, means 20 for discharging the resulting concentrate for processing, a recovery tank 21 for storing the discharged concentrate, a filtrate tank 17 for storing the filtrate, and coating the filtrate It has a filtrate pump 18 that returns to the booth 1.

  During painting, the article 3 is applied with a water-based paint in the painting booth 1 using a spray gun 2. The overspray paint that has not been applied to the object 3 is captured by the aqueous medium that forms the water curtain 4 behind the object 3, and enters the booth water tank 6 disposed at the bottom of the paint booth 1 as the booth water 5. Stored. The booth water 5 is extracted from the coating booth 1 by the booth water circulation pump 7 and then repeatedly used as the water curtain 4 again via the circulation line 8. Therefore, while the article 3 is being coated, the booth water 5 accumulates overspray paint, and solids such as resins and pigments that are essentially contained in the overspray paint over time. Become. In general, a water-based paint is dispersed in a mist form as an overspray paint in the atmosphere gas in the painting booth 1. Therefore, by generating the air flow 9 in the painting booth 1 and capturing the overspray paint in the atmospheric gas with the filter 10, the scrubber unit 11 absorbs it in an aqueous medium that is an absorption liquid (or also called a cleaning liquid), Remove overspray paint in ambient gas. Since the booth water 5 is repeatedly used for the aqueous medium of the scrubber unit 11, the solid content contained in the overspray paint in the atmospheric gas is also accumulated in the booth water 5. Booth water used in the treatment method of the present invention is obtained by the coating as described above.

  In the subsequent overspray coating treatment of the present invention, the booth water 5 used for painting is transferred to the storage tank 13, and then the batch filtration operation of the booth water is performed. That is, the booth water is continuously passed through the strainer 15 through the strainer 15 by the concentration pump 14, so that the aqueous medium originally contained in the aqueous paint and the aqueous medium used for capturing the overspray paint are collected. A part is removed from the booth water as filtrate and sent to the filtrate tank 17. On the other hand, the residue from which the filtrate has been removed is returned to the storage tank 13 via the concentration line 19. Subsequently, by passing the mixture of the residue and the booth water still stored in the storage tank 13 through the filter 16, the residue from which the filtrate is further removed is obtained. Then, the residue is returned again to the storage tank 13 via the concentration line 19, thereby producing a mixture having a higher solid content. Therefore, by repeating such a filtration operation, a concentrate in which the solid content is concentrated can be obtained in the storage tank 13. In order to facilitate the filtration of the booth water, an amine such as dimethylethanolamine and triethylamine or a hydrophilic organic solvent such as diethylene glycol monobutyl ether and ethylene glycol monobutyl ether may be added to the booth water. The viscosity of the booth water may be adjusted by a vessel.

  In addition, since the booth water is filtered batchwise as described above, during the concentration operation, a residue obtained by filtering the booth water, a mixture of the residue and the booth water still stored in the storage tank 13, and the Concentrated liquid materials generated by the filtration operation, such as the residue after the filtrate is further removed from the mixture and the mixture of the residue and the mixture still stored in the storage tank 13, are stored in the storage tank 13, the concentration pump 14, and the strainer. 15, and in the concentration system such as the filter 16 and the concentration line 19.

  As described above, the filtrate produced by the filtration operation of the booth water is sent from the filtrate tank 17 to the coating booth 1 and reused for painting as an aqueous medium for the booth water 5 and the scrubber unit 11, while the concentrate is stored in the storage tank. 13 is appropriately discharged by the discharge means 20 for processing and stored in the collection tank 21.

  The filter 16 of the treatment apparatus of the present invention is a filtration membrane module that can filter booth water containing solids such as resin and pigment using a pressure difference inside and outside the membrane, and is generally a cross-flow type. Filter, preferably an ultrafilter. A commercially available ultrafilter may be used. For example, a filter having a spiral filter is particularly preferable.

  In addition, the solid content of the resulting concentrate is adjusted by the circulation flow rate of the concentrated liquid (ie, the resin and pigment contained in the overspray paint is substantially concentrated) in the filtration operation of the booth water. Can do. That is, using the correlation between the circulating flow rate of the concentrated liquid product and the solid content of the concentrated liquid product, the solid content of the concentrated liquid product can be determined from the circulating flow rate in batch filtration. The resulting concentrate can be adjusted to a suitable solids content.

  When the viscosity of the concentrated liquid increases with the filtration operation of the booth water, the load (or frictional resistance) of the concentration pump 14 that supplies the booth water to the filter 16 increases, and the temperature of the concentrated liquid increases. As a result, the temperature of the concentrated liquid may exceed the limit temperature of the filter (for example, about 55 ° C. in the case of a limit filter). Therefore, the processing apparatus 12 of the present invention may additionally include a means for cooling the concentrated liquid material. However, in general, when obtaining a concentrate having a solids content of less than about 50% by weight, batch filtration operations do not exceed the limit temperature of the ultrafilter, and such cooling means are particularly Often not needed.

  In the processing apparatus 12 of the present invention, as the concentrated liquid is repeatedly filtered by a batch operation, the viscosity of the concentrated liquid increases. However, in winter and the like, the concentrated liquid is subjected to batch filtration. When stopped and the concentrated liquid remaining in the circulation system cools, the viscosity of the concentrated liquid further increases (eg, the viscosity reaches about 100 poise at a solids content of about 53% by weight at 5 ° C.). Therefore, if such a highly viscous concentrated liquid remains at a low temperature, the filtration operation may not be restarted. Thus, for example, if the concentrated liquid increases to a viscosity that is expected to be unable to restart due to thickening after stopping, it may be necessary in some cases to stop the filtration operation.

  The storage tank 13 of the processing apparatus of the present invention is a tank for temporarily storing booth water containing overspray paint that has not been applied to the article 3, and batch filtration of the booth water It is also a tank in which the concentrated liquid produced by the above is returned. Therefore, the concentrate can be obtained in the storage tank 13 at the end of the batch filtration operation.

  The discharge means 20 of the processing apparatus 12 of the present invention is for discharging the concentrate obtained in the storage tank 13 from the storage tank 13 for disposal. For example, the discharge means 20 is a valve provided in a storage tank, preferably a pipe in fluid communication with the bottom of the storage tank, and the concentrate obtained by batch filtration operation is discharged from the storage tank 13.

  The processing apparatus 12 of the present invention may additionally include a recovery tank 21 and temporarily stores the concentrate discharged from the storage tank by the discharge means 20. For example, it is preferable that the bottom of the recovery tank 21 is provided with wheels and can easily move. However, in that case, when supplying the concentrate to the recovery tank 21, it is preferable to provide a stopper on the wheel so that the recovery tank 21 does not move. When the concentrate is incinerated, an outlet is provided at the side or lower part of the recovery tank 21 so that the concentrate can be easily supplied from the recovery tank 21 to a receiving port of an incinerator or the like. It is preferable.

  In the present invention, the process mainly comprises a step of controlling the solid content (or water content) of the concentrate, a step of disposing of the concentrate, a step of recycling the filtrate, and a relatively small number of processing steps. Since the operation is easy, it is possible to easily design a treatment apparatus that automates such processing steps.

  Although one embodiment of the present invention has been described above, the present invention is not limited thereto, and it will be easily understood by those skilled in the art that various modifications can be made.

  The processing method of the overspray paint of this invention was implemented using the coating system of FIG. 1 in one embodiment. Odeecoline (registered trademark, manufactured by Nippon Paint Co., Ltd .: aqueous medium-polar solvent, water, solid content-water-soluble polyester resin, titanium oxide, extender pigment) was used. Using this water-based paint, steel furniture was painted.

[1] Painting process:
(1) In the painting booth 1, the object 3 was painted by applying a water-based paint with the spray gun 2.
(2) During such coating, the overspray paint that was not applied to the article 3 was captured by the water curtain 4.
(3) The overspray paint captured by the water curtain 4 is stored as booth water 5 at the bottom of the painting booth 1 and is repeatedly used as a water curtain again by circulating at about 300 m ³ / min (the booth water 5 is It was also used as an aqueous medium for the scrubber unit 11).
(4) The coating of the article 3 was completed.
[2] Treatment process of overspray paint:
(1) Booth water 5 (about 900 kg) used in the painting process was transferred to the storage tank 13 (capacity about 1000 L).
(2) Concentrate in which solid content is concentrated by batch filtration operation of booth water using ultrafilter 16 (weight: about 50 kg, solid content: about 52 wt%, viscosity: about 16 poise, temperature: about 25 ° C. )
(3) The concentrate 20 was discharged from the storage tank 13 by operating the valve 20 provided in the pipe in fluid communication with the storage tank 13.
(4) The discharged concentrate was stored in the recovery tank 21 (capacity: about 200 L).
(5) The concentrate was incinerated.

  The processing method of the overspray paint of this invention was implemented using the coating system of FIG. 1 in one embodiment. Silver-colored Aqualex AR-2000 (manufactured by Nippon Paint Co., Ltd .: water and water-based paint containing an acrylic melamine resin and an aluminum pigment as a solid content (22% by weight)) was used. Fender mirrors were painted using this water-based paint.

[1] Painting process:
(1) In the painting booth 1, the object 3 was painted by applying a water-based paint with the spray gun 2.
(2) During such coating, the overspray paint that was not applied to the article 3 was captured by the water curtain 4.
(3) The overspray paint captured by the water curtain 4 is stored as booth water 5 at the bottom of the painting booth 1 and is repeatedly used as a water curtain again by circulating at about 600 L / min (the booth water 5 is a scrubber Also used as an aqueous medium for part 11).
(4) The coating of the article 3 was completed.
[2] Treatment process of overspray paint:
(1) Booth water 5 (approximately 2000 kg) used in the painting process was transferred to a storage tank 13 (capacity approximately 2500 L).
(2) Concentrated solids (weight: about 200 kg, solids content: about 50% by weight, viscosity: about 20 poise, temperature: about 40 ° C. by batch filtration of booth water using ultrafilter 16 )
(3) The concentrate 20 was discharged from the storage tank 13 by operating the valve 20 provided in the pipe in fluid communication with the storage tank 13.
(4) The discharged concentrate was stored in the recovery tank 21 (capacity: about 200 L).
(5) The concentrate was incinerated.

FIG. 1 is a conceptual diagram schematically showing a coating system having an overspray paint processing apparatus in one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Painting booth, 2 ... Spray gun, 3 ... Coating object, 4 ... Water curtain (aqueous medium), 5 ... Booth water, 6 ... Booth water tank, 7 ... Booth water circulation pump, 8 ... Circulation line, 9 ... Painting booth Air flow inside, 10 ... Filter, 11 ... Scrubber section, 12 ... Overspray paint processing device, 13 ... Storage tank, 14 ... Concentration pump, 15 ... Strainer, 16 ... Filter, 17 ... Filtrate tank, 18 ... Filtrate pump, 19 ... Concentration line, 20 ... Discharge means, 21 ... Recovery tank.

Claims (7)

Spray water-based paint at the painting booth,
Capturing overspray paint that has not been applied to the substrate with an aqueous medium and collecting it as booth water,
Filtering the booth water batchwise using an ultrafilter to obtain a concentrate enriched in solids contained in the overspray paint, and recovering the concentrate for disposal An overspray processing method comprising:
A method wherein the solids content of the concentrate is 45% to 53% by weight. The method of claim 1, wherein the water-based paint is a paint that can be reused from the concentrate. The method according to claim 1, wherein an amine or a hydrophilic organic solvent is added to the booth water in order to facilitate the filtration of the booth water. The process according to any one of claims 1 to 3, characterized in that the solids content of the concentrate is adjusted from the circulation flow rate in batch filtration. The method according to claim 1, further comprising disposing of the concentrate by incineration. 5. A method according to any of claims 1 to 4, further comprising utilizing the concentrate as a liquid fuel. An apparatus for treating booth water comprising overspray paint,
A storage tank for storing the booth water;
An ultrafilter for concentrating the booth water,
Means for discharging the concentrate concentrated in the overspray paint obtained by filtration of the booth water for processing, and a line for returning the residue from which the filtrate has been removed by filtration to the storage tank; A processing apparatus comprising:

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