JP2005154881A - Method for recycling pole liquid, apparatus for recycling pole liquid, and electrodeposition coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recycling a pole liquid, which effectively recycles it for various kinds of treatment in an electrodeposition process, without returning the pole liquid to a pole liquid tank and without immediately discarding it; an apparatus for recycling the pole liquid; and an electrodeposition coating apparatus. <P>SOLUTION: The method for recycling the pole liquid in a diaphragm chamber of a diaphragm electrode (1) which is arranged in an electrodeposition tank and is provided with an anionic film and/or a neutral film comprises: arranging a diaphragm electrode (2) provided with an amphoteric membrane, and/or a bare electrode in the electrodeposition tank; controlling the ratio of electrolyzing quantity for the diaphragm electrode (1) to electrolyzing quantity for the diaphragm electrode (2) and/or the bare electrode to 90/10 to 20/80, and electrodeposition-coating an article; removing cation from at least one part of the pole liquid, while circulating the pole liquid between the diaphragm chamber and the pole liquid tank capable of storing the pole liquid; and utilizing the pole liquid in at least one of electrodeposition coating treatment and rinsing treatment. The recycling apparatus and the electrodeposition coating apparatus are used for performing the method of recycling the pole liquid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for recycling an extreme liquid, an apparatus for recycling an extreme liquid, and an electrodeposition coating apparatus.

In general, automobile bodies and parts are painted by electrodeposition. In this electrodeposition coating, it is considered that four phenomena of electrophoresis, electrodeposition, electrodialysis, and electrolysis occur simultaneously. That is, the charged paint particles move to the object to be coated as the counter electrode (electrophoresis), and the paint particles that have reached the object to be counter electrode emit electrons and deposit on the object to be coated (electrodeposition). ), The water in the deposited coating film moves into the coating liquid and is dehydrated, resulting in a coating film that does not conduct electricity (electrodialysis).
In addition, since the gas (hydrogen or oxygen) generated at the electrode causes a coating film defect, it is preferably suppressed (electrolysis) as much as possible.

  There are two types of electrodeposition coating described above: anode electrodeposition coating (anion electrodeposition coating) and cathode electrodeposition coating (cation electrodeposition coating). The anion electrodeposition coating is a coating method in which an acidic paint (having a negative charge) neutralized with an alkaline neutralizing agent is electrodeposited on an object to be coated using the object to be coated as an anode and a counter electrode as a cathode. On the other hand, cationic electrodeposition coating is a coating method in which an object to be coated is used as a cathode, a counter electrode is used as an anode, and an alkaline paint (having a positive charge) neutralized with an acid neutralizer is electrodeposited on the object to be coated. . Here, the alkaline paint refers to a product obtained by neutralizing a basic resin (for example, an amino-modified epoxy resin) with an organic acid that is an acidic neutralizing agent to make it water-soluble or emulsified. For example, acetic acid or the like is used as the organic acid.

  In general, cationic electrodeposition coating is a system for washing an object to be coated with a filtrate containing water, neutralizing acid, solvent, etc. taken out from the electrodeposition coating liquid, and a system for discharging excess neutralizing acid from the electrodeposition tank. Have both.

  As shown in FIG. 2, in the electrodeposition tank 20, an object to be coated 200 charged with a charged paint particle and a counter electrode, and an electrode 24 having the same polarity as the paint particle are immersed in the electrodeposition liquid. Are arranged as follows. Furthermore, a diaphragm chamber 22 is provided in the electrodeposition tank 20 so as to surround the electrode 24, and in the diaphragm chamber 22, only miscellaneous ions or the like that remove paint from the electrodeposition liquid stored in the electrodeposition tank 20 are provided. The diaphragm which permeate | transmits is provided.

  Further, the object to be coated 200 and the electrode 24 are electrically connected to the thyristor 170, respectively, and a direct current is passed so that the object to be coated 200 becomes a cathode and the electrode 24 becomes an anode.

  The electrodeposition liquid in the electrodeposition tank 20 is sent to the UF device 140 via the pump 160. In the UF device 140, pressure is applied to the semipermeable membrane from a liquid containing a polymer substance or a colloidal substance, so that only water, ions, and low molecular substances are permeated and separated from countless fine holes in the semipermeable membrane. The filtrate filtered by the UF device 140 is sent to the UF water washing tank 152, and the filtrate exceeding the capacity of the UF water washing tank 152 is sent to the UF water washing tank 150. The UF rinsing tanks 150 and 152 are used for cleaning the article 200 and are a closed system.

  Moreover, the electrodeposition is promoted by removing neutralized acid ions of a certain concentration or more accumulated in the electrodeposition tank 20. Therefore, as shown in FIGS. 2, 3 and 4, for example, excessive neutralized acid ions are selectively introduced into the diaphragm chamber 22 through the diaphragm 26 made of an ion exchange membrane using an anion membrane or a neutral membrane. Then, this excess neutralized acid ion-containing membrane liquid (hereinafter referred to as “polar liquid”) is fed to the polar liquid tank 30. Then, in the polar liquid tank 30, pure water is added so that the neutralized acid ion concentration becomes an optimum concentration in the electrodeposition tank 20, and the polar liquid having the neutralized acid ion concentration at a predetermined concentration is again added. It returns to the diaphragm chamber 22 through the pump 162. Thereby, the neutralized acid concentration in the electrodeposition tank 20 can be managed. On the other hand, the amount of polar liquid that exceeds the amount stored in the polar liquid tank 30 is always drained.

  In the above-described polar liquid circulation system, miscellaneous ions accumulated in the electrodeposition tank 20 are also attracted to the electrode 24 and transmitted through the diaphragm 26 to the polar liquid tank 30. Therefore, miscellaneous ions can be more efficiently removed from the electrodeposition tank 20.

  However, the above-mentioned polar liquid treatment system adds pure water to make the polar liquid in the polar liquid tank have a constant concentration, while the amount of the polar liquid exceeding the amount stored in the polar liquid tank is discharged out of the system. Has been.

Therefore, the acid liquid is discharged as a waste liquid at every electrodeposition coating. In order to drain the waste liquid out of the system, a certain discharge standard has to be satisfied, and there is a risk that the processing cost increases when further processing is performed.
In addition, in order to add pure water to the polar liquid tank, if the cost of pure water is taken into consideration, the above-mentioned partial polar liquid discharge system has a problem of high processing costs.

  Therefore, a method of reusing the polar liquid without discharging a part of the polar liquid from the polar liquid tank and without newly adding pure water has been proposed (for example, see Patent Document 1). However, since an adsorption process using a plurality of types of ion exchange resins is required, the cost becomes high after all, and it is difficult to sufficiently solve the above-described problems in consideration of practicality.

In addition, an electrodeposition coating apparatus has been proposed which attempts to guarantee the long-term stable operation of the diaphragm electrode device and the improvement of the quality of the coating film by preventing clogging of the diaphragm in the diaphragm electrode (see, for example, Patent Document 2). . However, this apparatus has a capacity limitation and cannot treat all polar solutions efficiently.
JP 2002-35746 A Japanese Utility Model Publication No. 6-51271

  The present invention has been made in view of the above-described conventional problems, and its purpose is to return the polar liquid from the polar liquid tank to the polar liquid tank again, and without discarding it immediately, the electrodeposition process. It is an object of the present invention to provide an extreme liquid recycling method, an extreme liquid recycling apparatus, and an electrodeposition coating apparatus that can be effectively used for various treatments. Another object of the present invention is to provide a method for reusing an extreme liquid, an apparatus for reusing an extreme liquid, and an electrodeposition coating apparatus that can maintain the quality of a coating film on a conventional object to be coated even if the electrode liquid is used for a cleaning process.

As a result of intensive studies to achieve the above object, the present inventors have conceived the present invention described below and found that the object can be achieved.
That is, the present invention is a method of reusing polar liquid in a diaphragm chamber of a diaphragm electrode (1) provided in an electrodeposition tank and having an anion membrane and / or a neutral membrane,
A diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane is provided in the electrodeposition tank, and the amount of electrolysis (D) of the diaphragm electrode (1) and the membrane electrode (2) provided with the amphoteric membrane and / or Alternatively, the electrodeposition coating treatment is performed with the ratio (D / N) to the amount of electrolysis (N) of the bare electrode as 90/10 to 20/80,
While circulating the polar liquid between the diaphragm chamber and the polar liquid tank capable of storing the polar liquid, at least a part of the polar liquid is subjected to cation removal treatment,
The method for reusing a polar liquid, wherein the polar liquid that has been subjected to the cation removal process is used in at least one of the electrodeposition coating process, the cleaning process, and the water washing process.

  By applying a cation removal treatment to a certain amount of the polar liquid, miscellaneous ions are removed, so that the acid can be effectively used and it can contribute to the formation of a high-quality coating film equivalent to the conventional one.

  The pH of the washing liquid used for the washing treatment and / or the washing water used for the washing treatment is preferably set to 5.0 to 6.5.

The present invention also includes at least an electrodeposition tank, an polar liquid tank, and a washing tank, provided in the electrodeposition tank, and provided in the diaphragm chamber of the diaphragm electrode (1) provided with an anion membrane and / or a neutral membrane. An extreme liquid recycling apparatus for reusing polar liquid,
The electrodeposition tank has a diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane,
A circulation structure in which the polar liquid circulates between the diaphragm chamber and the polar liquid tank;
Cation removal means for performing cation removal treatment on at least a part of the circulating polar liquid;
A liquid feeding means for feeding the polar liquid subjected to the cation removal treatment to at least one of the electrodeposition tank and the washing tank;
It is a polar liquid recycling apparatus characterized by having.

  The polar liquid recycling apparatus of the present invention is an apparatus used for carrying out the above-described method of reusing a polar liquid of the present invention. The polar solution that has been subjected to cation removal treatment does not contain cations such as iron, chromium, sodium, etc., so it can be used as an acid concentration adjusting solution for electrodeposition baths. It can also be supplied to at least one of the washing water concentration tanks and used for washing and washing treatment. As a result, the excess polar liquid can be effectively used without being immediately discarded. Even when such an extreme liquid is reused, the quality of the coating film formed on the article to be coated is as good as before.

Ratio between the amount of electrolysis (D) of the diaphragm electrode (1) having the anion membrane and / or the neutral membrane and the amount of electrolyte (N) of the diaphragm electrode (2) and / or the bare electrode having the amphoteric membrane ( D / N) is preferably 90/10 to 20/80.
By setting it as this aspect, it becomes easy to control the balance of an acid concentration.

Furthermore, it has a washing tank and / or a washing water concentration tank, and the liquid feeding means sends the polar solution subjected to the cation removal treatment to the washing tank and / or the washing water concentration tank. Is preferred.
By setting it as this aspect, since a polar liquid can be utilized for various processes, it can utilize more effectively.

Furthermore, the present invention includes at least an electrodeposition tank, an polar liquid tank, and a washing tank, provided in the electrodeposition tank, and provided in the diaphragm chamber of the diaphragm electrode (1) provided with an anion membrane and / or a neutral membrane. An electrodeposition coating apparatus having a polar liquid reuse mechanism for reusing polar liquid,
The electrodeposition tank has a diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane,
The cation recycle mechanism has a circulation structure in which the polar liquid circulates between the diaphragm chamber and the polar liquid tank, and performs cation removal treatment on at least a part of the circulated polar liquid. Removing means; and liquid feeding means for feeding the polar liquid that has been subjected to the cation removal treatment to at least one of the electrodeposition tank and the washing tank;
It is an electrodeposition coating apparatus characterized by having.

  The electrodeposition coating apparatus of the present invention is an apparatus for performing electrodeposition coating on an object while performing the above-described method of reusing an extreme liquid of the present invention. It is provided as a liquid recycling mechanism. Therefore, according to the electrodeposition coating apparatus of the present invention, as described above, it is possible to perform electrodeposition coating with a good coating film quality while effectively utilizing an acid (polar solution).

Ratio between the amount of electrolysis (D) of the diaphragm electrode (1) having the anion membrane and / or the neutral membrane and the amount of electrolyte (N) of the diaphragm electrode (2) and / or the bare electrode having the amphoteric membrane ( D / N) is preferably 90/10 to 20/80.
By setting it as this aspect, it becomes easy to control the balance of an acid concentration.

Furthermore, it has a washing tank and / or a washing water concentration tank, and the liquid feeding means sends the polar solution subjected to the cation removal treatment to the washing tank and / or the washing water concentration tank. Is preferred.
By setting it as this aspect, since a polar liquid can be utilized for various processes, it can utilize more effectively.

  According to the present invention, it is possible to recycle the polar liquid that can be effectively used for various processes in the electrodeposition process without returning the polar liquid from the polar liquid tank to the polar liquid tank again and without immediately discarding it. It is possible to provide a utilization method, an extreme liquid recycling apparatus, and an electrodeposition coating apparatus. In addition, it is possible to provide a method of reusing an extreme liquid, an apparatus for reusing an extreme liquid, and an electrodeposition coating apparatus that can maintain the quality of a coating film on an object to be coated even if the extreme liquid is reused for cleaning treatment.

  Hereinafter, the method for reusing a polar liquid, the apparatus for reusing a polar liquid and the electrodeposition coating apparatus of the present invention will be described in detail.

[Recycling method of polar liquid]
The method for reusing the polar liquid of the present invention is a method for reusing the polar liquid in the diaphragm chamber of the diaphragm electrode (1) provided in the electrodeposition tank and having an anion membrane and / or a neutral membrane.
Specifically, the above-mentioned diaphragm electrode (1), and the diaphragm electrode (2) provided with an amphoteric film and / or a bare electrode are provided in an electrodeposition tank when electrodeposition is applied to an object to be coated. Electrodeposition coating is performed with the ratio (D / N) of the electrolysis amount (D) of the diaphragm electrode (1) and the electrolysis amount (N) of the diaphragm electrode (2) and / or the bare electrode being 90/10 to 20/80. Apply processing.

By providing the diaphragm electrode having the diaphragm chamber, it is possible to prevent the neutralized acid and miscellaneous ions in the diaphragm from leaking out of the diaphragm. Moreover, Nippe diaphragm ^# 2000 (made by Nippon Paint Co., Ltd.) etc. can be used as an anion membrane used as a diaphragm of a diaphragm electrode (1). Moreover, as a neutral film | membrane, Non-Slugde (made by Polytex) etc. can be used.
Moreover, PT-LAN (made by Polytex) etc. can be used as an amphoteric membrane used as a diaphragm of a diaphragm electrode (2).

On the other hand, if all the electrodes are the diaphragm electrodes (1), the acid ion concentration in the tank becomes small, leading to a decrease in electrolytic ability. Therefore, in the present invention, it is preferable to provide a bare electrode together with the diaphragm electrode (1).
The ratio (D / N) of the amount of electrolysis (D) of the diaphragm electrode (1) and the amount of electrolysis (N) of the diaphragm electrode (2) and / or the bare electrode is 90/10 to 20/80 (preferably 80 / 20 to 30/70), it is possible to prevent a decrease in acid in the electrolytic cell while maintaining high electrolytic ability.

  In the present invention, the polar liquid is taken out and supplied to a tank (electrodeposition tank, washing tank, washing tank, etc.) other than the diaphragm chamber of the diaphragm electrode (1) to recycle the polar liquid. . However, it is not preferable to reuse the electrolyte as it is because the polar solution that has been subjected to electrolytic treatment has a high acid ion concentration and miscellaneous ions. Therefore, a polar liquid tank capable of storing the polar liquid is provided, and the cation removing process is performed on at least a part of the polar liquid while circulating the polar liquid between the diaphragm chamber and the polar liquid tank. The applied polar liquid is used for at least one of an electrodeposition coating treatment, a washing treatment, and a water washing treatment.

  By performing the cation removal treatment, ions unnecessary for the reuse of the polar liquid such as cations such as iron, chromium and sodium can be removed. Here, “perform at least a part of the polar liquid to remove the cation” means that a certain amount of the polar liquid is taken out from the polar liquid tank and the polar liquid is subjected to the treatment, or a certain amount as described later. This is a case where the polar solution is continuously taken out and the treatment is applied to the polar solution. The amount of the polar solution to be taken out is preferably set as appropriate depending on the type of electrodeposition coating treatment, washing treatment and washing treatment, the scale of the treatment apparatus, and the like.

  As described above, the polar solution that has been subjected to the cation removal treatment is preferably reused for the electrodeposition coating treatment, the washing treatment, and the water washing treatment.

  Here, the electrodeposition coating process refers to a process of performing electrodeposition coating on the entire object to be coated (car body, parts, etc.) or a desired place in the electrodeposition tank. As conditions for the electrodeposition coating treatment, normal conditions applied when electrodepositing a car body or the like can be employed.

  The cleaning process is a process of washing away unnecessary electrodeposition liquid and the like adhering to the object to be coated after the electrodeposition process. As the cleaning liquid used for the cleaning process, a cleaning liquid conventionally used in the above-mentioned electrodeposition coating can be used. Specifically, it is preferable to use a cleaning solution having a pH of 5.0 to 6.5. Therefore, in order to use the polar liquid that has been subjected to the cation removal treatment as the cleaning liquid, it is preferable to adjust the amount of the polar liquid to bring the pH to the above range.

Furthermore, the water washing treatment refers to a treatment of washing with a water washing solution (water or aqueous solution) after the washing treatment in order to further clean the surface of the object to be coated. The pH of the water washing solution used for the water washing treatment is preferably pH 5.0 to 6.5. By setting it as this range, melt | dissolution etc. of the coating film formed in a to-be-coated article can be prevented. Therefore, in order to use the polar liquid that has been subjected to the cation removal treatment as an aqueous solution for the water washing treatment, it is preferable to adjust the amount of the polar liquid to make the pH within the above range.
In addition, the said washing | cleaning process and a water washing process may be collectively performed as one cleaning process.

  It is preferable to implement the recycle method of the polar liquid of this invention using the polar liquid recycle apparatus or electrodeposition coating apparatus mentioned later. The details of the bare electrode and the like will be collectively described in “Explanation of the polar liquid recycling apparatus and electrodeposition coating apparatus” of the present invention described later.

[Extreme liquid recycling equipment and electrodeposition coating equipment]
The polar liquid recycling apparatus of the present invention may be used alone, or may be used by being incorporated as the polar liquid recycling mechanism of the electrodeposition coating apparatus of the present invention. Therefore, hereinafter, the electrodeposition coating apparatus of the present invention in which the polar liquid recycling apparatus of the present invention is incorporated as the polar liquid recycling mechanism will be described.

FIG. 1 illustrates the configuration of the electrodeposition coating apparatus of the present invention in which the polar liquid recycling apparatus (polar liquid recycling mechanism) of the present invention is incorporated.
An electrodeposition coating apparatus 100 shown in FIG. 1 has an electrodeposition tank 8, a polar liquid tank 2, a washing area 14, and a water washing area 12, and a diaphragm electrode (1) having a diaphragm chamber 4 in the electrodeposition tank 8. ) And a bare electrode (not shown). In addition, the water washing area | region 12 is an area | region provided as needed.

  The polar liquid is stored in the polar liquid tank 2. Between the diaphragm chamber 4 and the polar liquid tank 2, there is a circulation structure in which the polar liquid circulates through the pipes 1a and 1b. At least a part of the circulating polar liquid is sent from the polar liquid tank 2 to the cation removing means 10 through the pipe 3a by an overflow or a pump. The fed polar solution is subjected to a cation removing process by the cation removing means 10. The polar solution that has been subjected to the cation removal treatment is supplied to at least one of the electrodeposition tank 8, the washing region 14, and the water washing region 12 by a liquid feeding means including the pump 17 and the pipings 3c, 5a, 5b, and 5c through the piping 3b. (Pole liquid recycling mechanism). The polar liquid returned to the electrodeposition tank 8, the washing area 14, and the water washing area 12 is used to maintain the acid concentration of the electrodeposition paint by the organic acid (for example, acetic acid) contained in the polar liquid. Can do. In addition, the polar liquid may be fed to the washing water concentration tank 18 by the liquid feeding means.

A conventionally well-known thing can be used for the electrode and diaphragm chamber which are used for a diaphragm electrode.
The ion exchange membrane, which is the anion membrane, provided on the diaphragm electrode (1) allows anions such as neutralizing acid to pass through but does not allow cationic electrodeposition paints to pass through. In addition, the ion exchange membrane using the above neutral membrane has a large number of minute holes on the entire surface, and anions such as neutralizing acid that are smaller than these holes can pass through, but electrodeposition paints that are larger than the holes, etc. Cannot pass. Therefore, the diaphragm electrode (1) using these anion membranes or neutral membranes collects neutralizing acid (and other miscellaneous ions) in the membrane chamber and raises the acid concentration of the polar liquid.
On the other hand, the amphoteric membrane ion exchange membrane provided on the diaphragm electrode (2) has a two-layer structure of an anion exchange membrane and a cation exchange membrane. Do not pass. Therefore, in the case of a diaphragm electrode using an amphoteric membrane, the acid concentration of the polar liquid does not increase due to the collection of neutralizing acid in the diaphragm chamber. An example of a diaphragm electrode using an amphoteric membrane is “PT-LAN” manufactured by Polytex.
Since the bare electrode does not have a diaphragm chamber, there is no polar liquid.

  As a material used for the bare electrode, an electrode containing no Pb is preferably used. For example, a material based on stainless steel, ferrite, platinum, titanium or the like is used. Among them, it is preferable that the electrode is based on Ti, and at least the surface layer thereof is made of at least one selected from Ir, Ta, Ru, Pd, Pt and alloys or oxides thereof. Such a bare electrode is preferable because defects such as blisters hardly occur even when a Pb-containing electrode paint is used. In addition, as explained in the above-described method for reusing a polar liquid, the ratio (D /) of the electrolysis amount (D) of the diaphragm electrode (1) and the electrolysis amount (N) of the diaphragm electrode (2) and / or the bare electrode N) is preferably 90/0 to 20/80. Conventionally known conditions can be applied as other conditions for the electrolysis conditions.

FIG. 5 shows a schematic diagram showing an example of a part of the electrodeposition coating apparatus of the present invention in which a diaphragm electrode (1) using an anion membrane or a neutral membrane is used in combination with a bare electrode. Moreover, the schematic diagram which shows a part of example of the electrodeposition coating apparatus of this invention which uses together the diaphragm electrode which uses an anion membrane or a neutral membrane, and the diaphragm electrode which uses an amphoteric membrane is shown in FIG.
In FIG. 5, since a bare electrode is used together with a diaphragm electrode using an anion membrane or a neutral membrane (both membranes may be used together), it is compared with a case where only an anion membrane or a neutral membrane is used. Thus, the amount of electrolysis of the diaphragm electrode is reduced. As a result, the amount of neutralized acid collected in the diaphragm chamber is reduced, and the amount of the polar liquid in the polar liquid tank that performs cation treatment is also reduced. Accordingly, the amount of neutralized acid fed from the polar bath to the electrodeposition bath, washing bath, etc. is also reduced, so that it is easy to balance the liquid balance.

The same thing can be said in the example shown in FIG. 6, and a diaphragm electrode using an amphoteric membrane is used together with a diaphragm electrode using an anion membrane or a neutral membrane (both membranes may be used in combination). Therefore, compared with the case where only an anion membrane or a neutral membrane is used, the amount of electrolysis of the diaphragm electrode (electrode on the left side in FIG. 6) having a diaphragm chamber for collecting neutralized acid is reduced. As a result, the amount of neutralized acid collected in the diaphragm chamber is reduced, and the amount of the polar liquid in the polar liquid tank that performs cation treatment is also reduced. Accordingly, the amount of neutralized acid fed from the polar bath to the electrodeposition bath, washing bath, etc. is also reduced, so that it is easy to balance the liquid balance.
As will be described later, at least a part of the polar liquid returned to the polar liquid tank passes through the cation removal means through the pipe and is fed to the electrodeposition layer, the washing region, the water washing region, etc. by the liquid feeding means. Is done.
In the drawing, since the neutralizing acid is not concentrated in the polar liquid in the polar liquid tank provided on the right side of FIG. 6, it can be returned to the polar liquid chamber as it is.

  As shown in FIG. 1, an unillustrated article first acts as a cathode in an electrodeposition tank 8 provided with a diaphragm chamber surrounding a diaphragm electrode as an anode, and is subjected to an electrodeposition coating process. The object to be electrodeposited is transported to the cleaning region 14 in order to remove excess electrodeposition liquid and adhering dust.

The cation removing means 10 includes an adsorption device filled with an ion exchange resin. Specifically, it is configured to adsorb cations (cations) such as iron, chromium, and sodium. In the present invention, since the ion exchange resin is used only as the cation removing means 10, the cost is significant.
By performing the cation removal treatment on the polar liquid, the cation in the fed polar liquid is removed, and anions such as acetate ions pass through the pipe 3b.
In addition, as an ion exchange resin used, a strong acidic cation exchange resin etc. are preferable.

In the cleaning region 14, cleaning tanks 14a, 14b, and 14c are arranged. The object to be coated is cleaned by being dipped in order from the cleaning tank farthest from the electrodeposition tank 8 (in the case of FIG. 1, in the order of 14c, 14b, and 14a). The cleaning tanks 14a, 14b, and 14c are preferably configured such that the cleaning liquid sequentially moves due to overflow or the like. As the cleaning liquid, a filtrate filtered by a UF device (not shown) can be used.
Here, when the polar liquid is fed to the cleaning region 14 by the liquid feeding means, the polar liquid is the washing tank furthest away from the electrodeposition tank 8, that is, the washing tank 14c in which the object to be coated is finally washed. It is preferable that the liquid is fed to the liquid.

The object to be coated that has been subjected to the cleaning process in the cleaning area is conveyed to the water washing area 12. In the water washing region 12, water washing tanks 12a, 12b, 12c and 12d filled with a water washing solution (water or an aqueous solution) are arranged for washing with water. The object to be coated is cleaned by a dipping process and a spray process sequentially from the cleaning tank closest to the electrodeposition tank 8 (in the order of 12a, 12b, 12c, and 12d in the case of FIG. 1). The washing tanks 12a, 12b, 12c, and 12d are preferably configured such that the washing liquid sequentially moves due to overflow or the like. After the water washing process is performed, it is sent to the baking process.
Here, when the polar liquid is fed to the water washing region 12, the polar liquid is fed to the nearest water washing tank from the electrodeposition tank 8, that is, the water washing tank 12a in which the object to be coated is first washed. It is preferable. It is preferable that the polar liquid fed to the washing region 12 is added and fed in the range where the pH of the washing solution is 5.0 to 6.5.

  In addition, the place where the polar solution that has been subjected to the cation removal treatment is fed by the feeding means may be at least one of the electrodeposition tank 8, the washing area 14, the washing area 12, and the washing water concentration tank 18. .

  By performing the above washing treatment, water washing treatment, etc., while reusing the polar liquid effectively, the formation of a good coating film whose coating quality is the same as that using conventional processes and equipment Can be realized.

  Moreover, in the example of FIG. 1, at least a part of the polar liquid sent to the washing tank 12a is sent to the washing water concentration tank 18 through the pipe 7b. The washing water concentration tank 18 is a tank that is used to adjust the properties (for example, pH) of the fed extreme liquid and prepare a treatment liquid that can be used for washing treatment and washing treatment. . The washing water sent from the washing tank 12a is concentrated and filtered through the ultrafiltration filter 16 while driving the pump 19, and the filtrate is sent to the washing tank 12d through the pipe 7c, and the concentrated liquid is sent through the pipe 7d. Then, it enters the washing water concentration tank 18 again, and is sent to the washing region 14 (for example, the washing tank 14b) through the pipe 7a. By doing in this way, polar solution can be reused more effectively. In addition, the ultrafiltration filter 16 can be cleaned by the acidity of the polar liquid, and the state of the washing liquid can be stabilized to prevent adverse effects due to the aggregation of the paint components.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto.

[Examples 1 to 3 and Comparative Example]
The electrodeposition coating apparatus shown in FIG. 1 was used, and electrodeposition coating was performed on a test piece (70 mm × 150 mm × 0.7 mm thick cold-rolled steel sheet) subjected to phosphate treatment. In addition, Powernix 110 gray (made by Nippon Paint Co., Ltd.) was used as the electrodeposition liquid, and a stainless steel electrode was used as the bare electrode. The ratio (D / N) of the amount of electrolysis (D) of the diaphragm electrode provided with the anion membrane (Nippe Membrane ^# 2000 (manufactured by Nippon Paint)) and the amount of electrolysis (N) of the bare electrode was 50/50. As the cation exchange resin, ND mini clopack G (manufactured by Nippon Electric Works) was used.

Specifically, the polar liquid fed from the polar liquid tank 2 to the washing tank 12a by the liquid feeding means is fed to the washing water concentration tank 18, and the washing liquids having different polar liquid concentrations (Examples 1 to 3). Was prepared, and this was sent to the water washing tank 12 for water washing treatment.
Table 1 below shows the polar solution concentration, pH, conductivity, and evaluation results (re-solubility, water resistance) of the washing solution prepared. In the comparative example, pure water was used as the washing liquid.

  For re-solubility, the film thickness of the coating film that was dipped for 5 minutes, 10 minutes, and 20 minutes, dried and baked, and the coating film that was not immersed in these washing solutions The film thickness difference compared with the film thickness was examined, and the appearance of the coating film after baking was evaluated. As a result, as shown in Table 1, it was found that the same performance as that of the comparative example when immersed in pure water was exhibited.

  Moreover, about the immersion method among the water resistance tests, the test pieces subjected to the above-mentioned electrodeposition coating treatment were dipped in the washing solutions having different polar liquid concentrations for several seconds, dried, and baked. Next, this is coated in the order of intermediate coating, baking, top coating, and baking, and a cross-cut adhesion test (secondary adhesion) after a water resistance test (immersed in 40 ° C pure water for 240 hours) of the finished coating film. ) And the appearance was evaluated.

  Further, for the spot method, the test piece subjected to the above-mentioned electrodeposition coating treatment is kept horizontal, and on the surface, the above-mentioned washing solutions having different polar liquid concentrations are dropped in the form of 0.05 ml or 0.1 ml spots, It was dried and baked while keeping the horizontal so that no flow. Thereafter, the coating treatment was performed in the same manner as in the above immersion method, and the cross-cut adhesion test (secondary adhesion) and the appearance after the water resistance test of the finished coating film were evaluated. As a result, as shown in Table 1, it was found that the water resistance performance is comparable to the case of using pure water as a comparative example.

It is the schematic which shows the structure of the electrodeposition coating apparatus which comprises the polar liquid reuse apparatus of this invention. It is the schematic which shows the structure of a series of closed systems used for the conventional electrodeposition coating. It is explanatory drawing for demonstrating the principle of electrodeposition coating. It is explanatory drawing for demonstrating the relationship between an electrodeposition tank and a polar liquid tank. It is the schematic which shows a part of example of the electrodeposition coating apparatus of this invention. It is the schematic which shows the other example of a part of electrodeposition coating apparatus of this invention.

Explanation of symbols

1a, 1b, 3a, 3b, 3c, 5a, 5b, 5c, 7a, 7b ... Piping 2 ... Polar liquid tank 4 ... Separation chamber 8 ... Electrodeposition tank 12 ... Washing area 12a , 12b, 12c, 12d ... Washing tank 14 ... Washing area 14a, 14b, 14c ... Washing tank 16 ... Ultrafiltration filter 17, 19 ... Pump 18 ... Washing water concentration tank 10 ... Cation removing means 100 ... Electrodeposition coating apparatus

Claims (8)

A method of reusing polar liquid in a diaphragm chamber of a diaphragm electrode (1) provided in an electrodeposition tank and having an anion membrane and / or a neutral membrane,
A diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane is provided in the electrodeposition tank, and the amount of electrolysis (D) of the diaphragm electrode (1) and the membrane electrode (2) provided with the amphoteric membrane and / or Alternatively, the electrodeposition coating treatment is performed with the ratio (D / N) to the amount of electrolysis (N) of the bare electrode as 90/10 to 20/80,
While circulating the polar liquid between the diaphragm chamber and the polar liquid tank capable of storing the polar liquid, at least a part of the polar liquid is subjected to cation removal treatment,
A method of reusing an polar liquid, wherein the polar liquid that has been subjected to the cation removal process is used in at least one of the electrodeposition coating process, the cleaning process, and the water washing process.   The method for reusing a polar liquid according to claim 1, wherein the pH of the washing liquid used for the washing treatment and / or the washing liquid used for the washing treatment is set to 5.0 to 6.5. It has at least an electrodeposition tank, an polar liquid tank, and a washing tank, and is used in the electrodeposition tank to recycle the polar liquid in the diaphragm chamber of the diaphragm electrode (1) provided with an anion membrane and / or a neutral membrane. An extreme liquid recycling device,
The electrodeposition tank has a diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane,
A circulation structure in which the polar liquid circulates between the diaphragm chamber and the polar liquid tank;
Cation removal means for performing cation removal treatment on at least a part of the circulating polar liquid;
A liquid feeding means for feeding the polar liquid subjected to the cation removal treatment to at least one of the electrodeposition tank and the washing tank;
A polar liquid recycling apparatus comprising:   Ratio between the amount of electrolysis (D) of the diaphragm electrode (1) having the anion membrane and / or the neutral membrane and the amount of electrolyte (N) of the diaphragm electrode (2) and / or the bare electrode having the amphoteric membrane ( D / N) is 90/10 to 20/80, the polar liquid recycling apparatus according to claim 3.   Furthermore, it has a washing tank and / or a washing water concentration tank, and the liquid feeding means sends the polar solution subjected to the cation removal treatment to the washing tank and / or the washing water concentration tank. The polar liquid recycling apparatus according to claim 3 or 4, characterized in that: It has at least an electrodeposition tank, an polar liquid tank, and a washing tank, and is used in the electrodeposition tank to recycle the polar liquid in the diaphragm chamber of the diaphragm electrode (1) provided with an anion membrane and / or a neutral membrane. An electrodeposition coating apparatus having an extreme liquid recycling mechanism,
The electrodeposition tank has a diaphragm electrode (2) and / or a bare electrode provided with an amphoteric membrane,
The cation recycle mechanism has a circulation structure in which the polar liquid circulates between the diaphragm chamber and the polar liquid tank, and performs cation removal treatment on at least a part of the circulated polar liquid. Removing means; and liquid feeding means for feeding the polar solution that has been subjected to the cation removal treatment to at least one of the electrodeposition tank and the washing tank;
An electrodeposition coating apparatus characterized by comprising:   Ratio between the amount of electrolysis (D) of the diaphragm electrode (1) having the anion membrane and / or the neutral membrane and the amount of electrolyte (N) of the diaphragm electrode (2) and / or the bare electrode having the amphoteric membrane ( The electrodeposition coating apparatus according to claim 6, wherein D / N) is 90/10 to 20/80.   Furthermore, it has a washing tank and / or a washing water concentration tank, and the liquid feeding means sends the polar solution subjected to the cation removal treatment to the washing tank and / or the washing water concentration tank. The electrodeposition coating apparatus according to claim 6 or 7, wherein:

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