JP2011099158A - System for recovery of electrodeposition paint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system for recovery of an electrodeposition paint which can reduce loss of the paint in a multistage recovery and washing process for a membrane filtration filtrate in electrodeposition coating, by efficiently increasing a washing liquid in the final stage, and which is actualized by utilizing existing equipment. <P>SOLUTION: The system for recovery of an electrodeposition paint supplies the membrane filtration filtrate of electrodeposition bath liquid into the final stage washing tank of a membrane filtration filtrate multistage recovery and washing process, and is characterized in that the multistage recovery and washing process for a membrane filtration filtrate includes at least one dip type washing tank, the filtrate obtained by carrying out the membrane-filtration of the liquid in the at least one dip type washing tank is supplied into the final stage washing tank, and the concentrated liquid is supplied into an electrodeposition bath and/or a washing tank at a stage before the dip type washing tank in which the liquid in the washing tank is membrane-filtrated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrodeposition coating material recovery system that reduces the loss of electrodeposition coating material while maintaining a good coating finish in electrodeposition coating.

  Conventionally, electrodeposition coating has been widely used for painting automobile bodies, automobile parts, electrical products and building materials. The electrodeposition coating system consists of an electrodeposition process for electrochemically forming a coating film on an object to be coated, a cleaning process for washing off non-electrodeposited paint, and a drying-baking process for curing the coating film. In general, the washing process is roughly divided into a membrane filtration filtrate multistage recovery water washing process and a final water washing process.

  In the membrane filtration filtrate multistage recovery water washing process, the coating material is washed using the filtrate obtained by filtering the coating material in the electrodeposition tank with a membrane, and the coating material physically adhered to the coating material is washed off and electrodeposition is performed. It is a process of collecting in a tank. In addition, the final water washing step is a step of performing final washing using pure water or purified water (industrial water), and a trace amount of paint and contaminant ions that could not be washed out in the membrane filtration filtrate multi-stage recovery water washing step are washed away. However, the water after being used for washing is discharged out of the process as waste water.

  However, in the case of the conventional water washing method, when a large amount of electrodeposition is applied to the object to be coated, the concentration of non-electrodeposited paint in each recovered water washing tank increases, and the amount of paint taken out of the electrodeposition coating facility increases. For this reason, the paint recovery rate is reduced, and in order to compensate for this, there are problems such as an increase in the amount of purified water and pure water used in the final washing step and an increase in the wastewater treatment burden. This problem can be solved by increasing the number of steps of the membrane filtration filtrate multistage recovery water washing step, but a new problem of increased equipment costs and installation space arises.

  In order to solve the above-mentioned problem, in Patent Document 1, the first stage of recovered water washing water in the membrane filtration filtrate multistage recovery water washing step is filtered by an ultrafiltration membrane device, and the obtained filtrate is subjected to membrane filtration filtrate multistage recovery water washing. Propose to supply to the last stage of the process. However, in this method, there is a problem that the amount of the filtrate obtained by ultrafiltration of the recovered washing water in the first stage is small, and the concentration of the non-electrodeposition paint in the final stage is not sufficiently lowered.

Japanese Patent Laid-Open No. 7-224397

  In view of the above problems, an object of the present invention is to provide an electrodeposition paint recovery system that does not increase the loss of electrodeposition paint by utilizing existing equipment in electrodeposition paint. Another object of the present invention is to provide an electrodeposition paint recovery system that can reduce paint loss by efficiently increasing the final stage wash water in the membrane filtration filtrate multistage recovery water washing step.

  There are two types of washing tanks in the membrane filtration filtrate multistage recovery washing process, spray type and dip type. The spray type is a type in which the amount of washing water is small and at least a part of the article to be coated is immersed in the washing water, and the article is washed by spraying the washing water on the article to be coated. . On the other hand, the dip type is a type in which a large amount of rinsing water is retained, the coated object is completely immersed in the rinsing water, and the coated object is washed by immersing the coated object in the rinsing water. When adding a membrane filtration device, the dip-type washing tank retains a larger amount of washing water than the spray-type washing tank, so that the recovered washing water can be stably supplied to the membrane filtration device. Suitable for installation. In addition, the dip-type water rinsing tank has better cleaning efficiency of the object to be coated than the spray-type water rinsing tank.

That is, the present invention provides the following inventions.
(1) In the electrodeposition paint recovery system for supplying the membrane filtration filtrate of the electrodeposition bath liquid to the final stage washing tank of the membrane filtration filtrate multistage recovery water washing process, the membrane filtration filtrate multistage recovery water washing process includes at least one dip type water washing A tank is provided, and the filtrate obtained by membrane filtration of the dip-type washing tank liquid of at least one tank is supplied to the final stage washing tank, and the concentrated liquid is membrane-filtered by the electrodeposition bath and / or the washing tank liquid. An electrodeposition paint recovery system, characterized in that the electrodeposition paint recovery system is supplied to a rinsing tank in a stage preceding the dip-type washing tank.
(2) The electrodeposition paint recovery system according to the above item (1), wherein the dip-type water washing tank to be membrane-filtered is the last stage dip-type water washing tank.
(3) The electrodeposition paint recovery system according to item 1 or 2, wherein the filtration membrane is a microfiltration membrane or an ultrafiltration membrane.
(4) The electrodeposition paint recovery system according to the above item 3, wherein the filtration membrane is an ultrafiltration membrane.
(5) The last stage dip-type washing tank is one or two or more stages before the last stage of the membrane filtration filtrate multistage recovery washing process, and the filtrate obtained by membrane filtration of the last stage dip-type washing tank The electrodeposition paint according to any one of the above items 2 to 4, wherein the amount is 2 to 9 times the amount of the concentrated liquid supplied to the electrodeposition bath and / or the water tank before the last dip type water tank. Collection system.
(6) The last stage dip-type washing tank is one or two or more stages before the last stage of the membrane filtration filtrate multi-stage recovery water washing process, and the concentrated solution when the last stage dip-type washing tank liquid is membrane filtered. The electrodeposition paint recovery system according to any one of the above items 2 to 5, wherein the paint heating residue is 1.1 to 10 times the paint heating residue of the last-stage dip-type washing tank.
(7) The electrodeposition paint recovery system as described in 5 or 6 above, wherein the membrane filtration of the dip-type water washing tank liquid in the last stage of the membrane filtration filtrate multistage recovery water washing step is performed by a circulation pump.
(8) Membrane filtration The membrane filtration of the dip-type washing tank liquid at the last stage of the multistage recovery water washing step is an average filtration represented by the following formula with a paint heating residue of the circulating liquid of 0.5 to 6%. The electrodeposition paint recovery system according to any one of the above items 5 to 7, wherein the differential pressure is 0.05 to 0.4 MPa.
Average filtration differential pressure = (membrane module input pressure + membrane module output pressure) / 2−filtration side pressure

  According to the present invention, the concentration of the non-electrodeposition paint in the final stage washing tank is reduced by using the conventional membrane filtration filtrate multistage recovery washing process as it is, and by providing a membrane filtration device in the washing tank. Loss can be reduced, and an increase in drainage load can be suppressed.

It is the figure which showed an example of the conventional electrodeposition coating material collection | recovery system. It is the figure which showed an example of the electrodeposition coating material collection | recovery system of this invention. It is the figure which showed an example of the membrane filtration apparatus used with the conventional electrodeposition coating material collection | recovery system. It is the figure which showed an example of the membrane filtration apparatus used with the electrodeposition coating material collection | recovery system of this invention.

There are two types of washing tanks used in the membrane filtration filtrate multistage recovery water washing process, spray type and dip type, but in the present invention, the membrane filtration filtrate multistage recovery water washing process has at least one dip type water washing tank, A membrane filtration device is provided in at least one of the dip-type washing tanks. That is, when there is one dip-type washing tank, a membrane filtration device is provided in one dip-type washing tank, and when there are two or more dip-type washing tanks, any dip-type washing tank may be provided. It is preferable to provide a membrane filtration device in the last-stage dip-type washing tank farthest from the electrodeposition bath.
Since the dip-type rinsing tank retains a large amount of rinsing water, it is easy to supply the recovered rinsing water to the second membrane filtration device, and is suitable for remodeling the existing membrane filtration filtrate multistage recovery rinsing process.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example of a conventional electrodeposition coating material recovery system, in which 1 is an electrodeposition bath, A is a membrane filtration filtrate multistage recovery water washing step, and B is a final water washing step. The membrane filtration filtrate multistage recovery water washing step A is composed of three stages of a spray type first water washing tank 2, a dip type second water washing tank 3, and a spray type third water washing tank 4, and the final water washing step B is a dip. The first water washing tank 5 is a mold and the second water washing tank 6 is a spray type. The object to be coated is mounted on a conveyor (not shown), immersed in an electrodeposition bath and electrodeposited, and then subjected to a first water washing tank, a second water washing tank, and a third water washing in a membrane filtration filtrate multistage recovery water washing process. It is conveyed in order to the tank, the first water-washing tank and the second water-washing tank in the final water-washing process, and washed with water. Reference numeral 7 denotes a first membrane filtration device. The electrodeposition liquid is sent from the electrodeposition bath to the first membrane filtration device via the line 10 and membrane filtered. The concentrate that does not permeate the membrane is returned to the electrodeposition bath by line 11. The filtrate is sent to the final stage of the membrane filtration filtrate multistage recovery water washing step, in this example, the third water washing tank, via the line 12 and used as flush water in the membrane filtration filtrate multistage recovery water washing step. The flush water in the membrane filtration filtrate multistage recovery flush process overflows in order from the third flush tank 4 to the second flush tank 3 and the first flush tank 2 and is used as flush water in each flush tank. Overflow from the rinsing tank 2 to the electrodeposition bath 1 causes the non-electrodeposition paint to be recovered. Pure water or purified water (engineering water) is supplied from the line 13 to the first washing tank 5 in the final washing process, and pure water or purified water (engineering water) is supplied from the line 14 to the second washing tank 6. To be washed. The pure water supplied to the second rinsing tank 6 overflows into the first rinsing tank 5 and is discharged from the line 15 together with the purified water supplied to the first rinsing tank.

FIG. 2 is an example of the electrodeposition paint recovery system of the present invention. In FIG. 2, the same devices as those in FIG. The system shown in FIG. 2 is characterized in that the second membrane filtration device 8 is newly provided in the dip-type second water washing tank 3 in the conventional system shown in FIG. This is the same as the conventional system shown in FIG. The second rinsing tank liquid is supplied from the line 16 to the second membrane filtration device 8, and the concentrated liquid that does not permeate the membrane is returned to the electrodeposition bath by the line 17. The filtrate is supplied to the third water washing tank 4 (the final stage of the membrane filtration filtrate multistage recovery water washing step) through the line 18 and is used as washing water together with the filtrate of the first membrane filtration device 7 supplied through the line 12.
By providing the above-mentioned second membrane filtration device, it is possible to efficiently increase the final stage washing liquid, prevent an increase in non-electrodeposited paint in the final stage, and suppress an increase in paint loss.

  In the present invention, devices used in the conventional system other than the newly provided second membrane filtration device can be used without any limitation under the operating conditions used in the conventional system. For example, although the example of two stages was shown as the final water washing process, of course, one stage may be sufficient. Various contrivances have been conventionally made in the final water washing step, and the conventionally known final water washing step can be used in the present invention without any limitation.

In addition, as the membrane filtration filtrate multistage recovery water washing step, an example of a three-stage configuration in which the first stage is a spray-type water washing tank, the second stage is a dip-type water washing tank, and the third stage is a spray-type water washing tank. A dip-type washing tank may be used for the three stages. In that case, it is preferable that the 2nd membrane filtration apparatus 8 is provided in the 3rd washing tank 4 further away from the electrodeposition bathtub 1. FIG. Further, there is no third-stage spray-type washing tank 4, and a two-stage configuration may be used. In this case, the second membrane filtration device 8 is provided in the second-stage dip-type washing tank 3 as the final stage. Of course, it is possible to adopt a configuration with four or more stages. What is important is that at least one of the dip type water washing tanks is necessarily included, and the second membrane filtration device is provided in at least one of the dip type water washing tanks. Thereby, the non-electrodeposition paint in the final stage washing tank is reduced, and the loss of the electrodeposition paint can be reduced.
For the second membrane filtration device 8, the membrane filtration device for the electrodeposition bath liquid used in the conventional electrodeposition paint recovery system can be used without any limitation under the conventional operating conditions. It is preferable to use a membrane filtration apparatus as shown in FIG.

  In order to reduce the paint loss in the final washing tank of the membrane filtration filtrate multistage recovery washing process, it is necessary to increase the washing water, that is, increase the amount of filtrate in the first membrane filtration device. However, the electrodeposition liquid contains a large amount of paint, and the paint heating residue (NV) is usually about 10 to 25%. With such a high NV, there is a limit to the increase in the amount of filtrate in the first membrane filtration device. In the present specification, the paint heating residue (NV) is a value measured according to JISK5601-1-2.

The present invention is characterized in that, in addition to the first membrane filtration device, the second membrane filtration device is provided in the dip-type water washing tank of the membrane filtration filtrate multistage recovery water washing step, in the second water washing tank 3 in the above example. The second membrane filtration apparatus is supplied with the second flush water through the line 16, and the filtrate is fed as the flush water into the third flush tank through the line 18. The concentrate that has not permeated through the membrane is sent to the electrodeposition bath via line 17. The concentrated liquid may be sent to a stage preceding the dip type water washing tank provided with the second membrane filtration device of the membrane filtration filtrate multistage recovery water washing step, in this example, the first water washing tank 2.
By providing such a second membrane filtration device, it is possible to efficiently recover the non-electrodeposition coating material in the final stage washing tank and to reduce the NV in the final stage washing tank.

  In the electrodeposition paint recovery system, membrane filtration generally increases the amount of filtrate when the NV of the treatment liquid is low. The electrodeposition bathtub and the NV of each washing tank are the highest in the electrodeposition bathtub, and gradually decrease in the order of the first washing tank, the second washing tank, and the third washing tank in the membrane filtration filtrate multistage recovery washing process. Therefore, the NV of the final stage washing tank of the membrane filtration filtrate multistage recovery washing process is the lowest, and it is efficient to filter the final stage washing tank.

However, as described above, the spray-type washing tank has a small amount of washing water and is not suitable for the stable supply of recovered washing water to the membrane filtration device. Therefore, it is preferable to filter the water in the last stage of the dip-type water rinsing tank that is suitable for the stable supply of recovered rinsing water because there is a space for installing a membrane filtration device in the vicinity. In the case of the above-described example, the second rinsing tank 3 which is the last stage dip-type washing tank is one before the last stage, but the NV of the washing tank one stage before the last stage is 1 to 5%. Therefore, it is possible to collect 2 to 9 times as much filtrate as the first membrane filtration device for filtering the electrodeposition bath liquid by filtering the washing tank liquid immediately before the final stage.
In the case of this example, since the washing tank provided with the membrane filtration device is one step before the final stage of the membrane filtration filtrate multistage recovery washing process, the NV of the washing tank is smaller than that provided in the final stage washing tank. Since it is high, the amount of filtrate collected is reduced, while the operation of the membrane filtration device is stable.

  The amount of liquid supplied to the second water washing tank 3 (the dip-type water washing tank at the last stage of the membrane filtration filtrate multistage recovery water washing process) is an overflow from the third water washing tank 4, but this overflow amount is the third water washing tank. 4, that is, the amount of filtrate of the first membrane filtration device and the amount of filtrate of the second membrane filtration device, so that the second membrane filtration device sent from the second water washing tank 3 to the electrodeposition bath 1 The amount of concentrate must be less than that of the first membrane filter. As described above, the amount of filtrate of the second membrane filtration device that filters the washing tank liquid immediately before the final stage of the membrane filtration filtrate multistage recovery water washing step is 2 to 9 times the amount of filtrate of the first membrane filtration device. Therefore, in the second membrane filtration device, the amount of filtrate sent to the third water washing tank 4 by the line 18 must be controlled to be at least 2 to 9 times the amount of concentrate sent to the electrodeposition bath by the line 17. .

  Moreover, if the amount of filtrate sent to the 3rd washing tank 4 by the line 18 exceeds at least 10 times the amount of concentrate sent to the electrodeposition bath by the line 17, NV of a concentrate will rise and filtrate collection efficiency will fall. there's a possibility that. On the other hand, if it is less than twice, the NV of the circulating fluid may decrease and the filtrate amount may become unstable.

  FIG. 3 is a view showing an example of a conventional membrane filtration device used in the first membrane filtration device. In FIG. 3, 20 is a membrane module and 21 is a supply pump. The remaining 95 to 99 parts that were controlled so that the filtrate sent to the second or third washing tank would be 1 to 5 parts per 100 parts of the processing liquid supplied from the electrodeposition bath 1 and did not permeate the membrane. The concentrated liquid is returned to the electrodeposition bath 1 in the course of the event. If the conventional membrane filtration device as shown in FIG. 3 is used as the second membrane filtration device, it is difficult to perform the control as described above.

  FIG. 4 is a view showing a preferred example of the membrane filtration device used in the second membrane filtration device. In FIG. 4, the same parts as those in FIG. The second membrane filtration device is characterized in that a circulation pump 22 and a circulation line 23 are provided as compared with the first membrane filtration device. 100 parts of the processing liquid supplied from the second water rinsing tank 3 is combined with the liquid from the circulation line 23 and is increased to 1000 to 3000 parts by the circulation pump 22 and supplied to the membrane module 20. At the same time, the amount of filtrate returned to the second washing tank 3 is controlled to be 70 to 90 parts, and at the same time, the amount of concentrate returned from the line 17 to the electrodeposition bath 1 is less than the amount of filtrate of the first membrane filtration device. The concentration is controlled to be 10 to 30 parts, and the concentrate is circulated in the circulation line 23.

  Further, the NV of the concentrated liquid (circulating liquid) of the second membrane filtration device is preferably 1.1 to 10 times, more preferably 1.5 to 8 times, and 2 to 6 times that of the second washing tank 3. Particularly preferred. If the NV of the concentrated liquid (circulating liquid) of the second membrane filtration device exceeds 10 times the NV of the second water washing tank 3, the NV of the concentrated liquid may increase, and the filtrate collection efficiency may decrease. On the other hand, when the ratio is less than 1.1 times, the NV of the circulating liquid is lowered, and the stability of the filtrate amount may be deteriorated.

In order to operate the second membrane filtration apparatus shown in FIG. 4 under the above-described conditions, the NV of the treatment liquid circulated to the membrane module 20 is 0.5 to 6%, preferably about 2 to 6%. As the average filtration differential pressure of the membrane module represented by the following formula, 0.05 to 0.40 MPa, preferably 0.10 to 0.30 MPa, and more preferably 0.10 to 0.20 MPa.
Average filtration differential pressure = (membrane module input pressure + membrane module output pressure) / 2−filtration side pressure

There is no restriction | limiting in particular about the membrane used for a 2nd membrane filtration apparatus, For example, a reverse osmosis membrane (RO membrane), an ultrafiltration membrane (UF membrane), a microfiltration membrane (MF membrane), etc. are mentioned. Among these, it is preferable to use an MF film and a UF film, and it is particularly preferable to use a UF film.
The RO membrane has a low processing capacity per unit time and is not economically preferable. The MF film is excellent in processing capacity per unit time, but a part of the paint component may permeate therethrough.
On the other hand, the UF membrane has no practical problem in terms of processing ability and paint component removal ability. The UF membrane preferably has a molecular weight cut off of about 3,000 to 1,000,000, and the materials are polyacrylonitrile, polysulfone, polyolefin, polyvinylidene fluoride (PVDF), and chemically modified products thereof. Any of these may be used.

As the membrane module, any type of membrane module using a membrane such as the above-described UF membrane, such as a hollow fiber type, a spiral type, and a tubular type, can be used.
The electrodeposition paint used in the electrodeposition paint recovery system of the present invention is not particularly limited, and may be any electrodeposition paint such as a cationic electrodeposition paint and an anion electrodeposition paint.

Hereinafter, the present invention will be described in detail using examples and comparative examples, but the present invention is not limited to these examples.
(Example)
Electrodeposition coating was performed using the electrodeposition paint recovery system shown in FIG. The first membrane filtration device 7 was the membrane filtration device shown in FIG. 3, and the membrane was an ultrafiltration membrane KCV-3010 manufactured by Asahi Kasei Chemicals Corporation. The membrane filtration device shown in FIG. 4 was used for the second membrane filtration device 8, and an ultrafiltration membrane KCV-3010 manufactured by Asahi Kasei Chemicals Corporation was used for the membrane.
As the electrodeposition paint, a cationic electrodeposition paint was used, and the electrodeposition of the automobile was performed.

  The electrodeposition bath 1 is adjusted so that the NV of the electrodeposition bath is 20%. In the first membrane filtration device 7, the supply amount of the electrodeposition bath liquid was set to 2700 L / min, and the filtrate amount was set to 45 L / min. The second membrane filtration device 8 is configured to supply a second washing tank liquid supply amount of 120 L / min, a circulation amount of 1800 L / min, a filtrate amount of 100 L / min, and an amount of concentrated liquid (circulation fluid) to be sent to the electrodeposition bath 1. It was set to 20 L / min. The amount of purified water supplied to the first water washing tank in the final water washing step was set to 50 L / min, and the amount of pure water supplied to the second water washing tank was set to 50 L / min. The amount of liquid brought into the first water washing tank of the final water washing process from the third water washing tank 4 of the membrane filtration filtrate multistage recovery water washing process together with the automobile to be coated is 12 L / min. It was taken out of the second washing tank. The amount of drainage from the first water washing tank in the final water washing step was 100 L / min.

Table 1 shows the paint recovery rate represented by the following equation and the NV of each washing tank when operating under such conditions, together with the above set conditions.
Paint recovery rate = (1−membrane filtration filtrate multistage recovery water washing process final stage NV / electrodeposition bath NV) × 100
Table 1 also shows the circulating fluid NV of the second membrane filtration device and the average filtration differential pressure.

(Comparative example)
Except that the second membrane filtration device 8 was removed, the same electrodeposition paint recovery system as in the example, that is, the system shown in FIG. . The obtained paint recovery rate, NV of each washing tank, etc. are shown together with Table 1 in Table 1.

  As is apparent from Table 1, the electrodeposition paint recovery system of the present invention equipped with the second membrane filtration device is in spite of the fact that the number of stages of the conventional electrodeposition paint recovery system and the membrane filtration filtrate multistage recovery water washing step is the same. First, the paint recovery rate is greatly increased compared to the conventional electrodeposition paint recovery system.

  The electrodeposition paint recovery system of the present invention can be easily modified from the conventional electrodeposition paint recovery system, and the paint recovery rate is the same as the conventional electrodeposition paint recovery system and the number of stages of the membrane filtration filtrate multistage recovery water washing step. Will increase significantly. Therefore, the industrial utility value is extremely large.

DESCRIPTION OF SYMBOLS 1 Electrodeposition bath 2 Membrane filtration filtrate multistage recovery water washing process 1st water washing tank 3 Membrane filtration filtrate multistage recovery water washing process 2nd water washing tank 4 Membrane filtration filtrate multistage recovery water washing process 3rd water washing tank 5 Final water washing process 1st water washing tank 6 Final Washing process second washing tank 7 First membrane filtration device 8 Second membrane filtration device 20 Membrane module 21 Supply pump 22 Circulation pump A Membrane filtration filtrate multistage recovery washing step B Final washing step

Claims (8)

  In the electrodeposition paint recovery system for supplying the membrane filtration filtrate of the electrodeposition bath liquid to the final stage water washing tank of the membrane filtration filtrate multistage recovery water washing process, the membrane filtration filtrate multistage recovery water washing process includes at least one dip type water washing tank. The filtrate obtained by membrane filtration of the at least one dip-type washing tank liquid is supplied to the final stage washing tank, and the concentrated solution is a dip in which the electrodeposition bath and / or the washing tank liquid is membrane filtered. An electrodeposition paint recovery system, characterized in that it is supplied to a water-washing tank in a stage preceding the mold water-washing tank.   2. The electrodeposition paint recovery system according to claim 1, wherein the dip-type washing tank to be membrane-filtered is the last stage dip-type washing tank.   The electrodeposition paint recovery system according to claim 1 or 2, wherein the filtration membrane is a microfiltration membrane or an ultrafiltration membrane.   The electrodeposition paint recovery system according to claim 3, wherein the filtration membrane is an ultrafiltration membrane.   The last stage dip type washing tank is one or two or more stages before the last stage of the membrane filtration filtrate multistage recovery washing process, and the amount of filtrate obtained by membrane filtration of the last stage dip type washing tank liquid is The system for recovering an electrodeposition paint according to any one of claims 2 to 4, which is 2 to 9 times the amount of the concentrate supplied to the bathing tank and / or the washing tank before the last stage dip-type washing tank. .   The last-stage dip-type washing tank is one or more before the last stage of the membrane filtration filtrate multi-stage recovery washing process, and the paint heating residue of the concentrated liquid when the last-stage dip-type washing tank liquid is membrane filtered The system for recovering an electrodeposition paint according to any one of claims 2 to 5, wherein the minute amount is 1.1 to 10 times the paint heating residue of the dip-type water washing tank at the last stage.   The system for recovering an electrodeposition paint according to claim 5 or 6, wherein the membrane filtration of the dip-type washing tank liquid in the final stage of the membrane filtration filtrate multistage recovery water washing step is performed by a circulation pump. The membrane filtration of the dip-type washing tank liquid in the last stage of the membrane filtration filtrate multistage recovery water washing step is 0.5 to 6% of the paint heating residue of the circulating liquid, and the average filtration differential pressure expressed by the following formula is The electrodeposition paint collection system according to any one of claims 5 to 7, which is performed at 0.05 to 0.4 MPa.
Average filtration differential pressure = (membrane module input pressure + membrane module output pressure) / 2−filtration side pressure

Images