JP2727231B2 - Electrocoating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrodeposition coating apparatus, and more particularly, to an object to be coated forming a first electrode portion and disposed corresponding thereto. An electrodeposition coating apparatus provided with a second electrode portion;
The present invention relates to an electrodeposition coating apparatus in which a diaphragm electrode device is used as an electrode part of the above.

[Prior art] Electrodeposition coating is roughly classified into those using an anionic type coating and those using a cationic type coating. In recent years, it has been widely applied to, for example, an automatic coating treatment of an automobile body, which is particularly suitable for undercoating or one-coat finishing of metal coating, because of its excellent property and low occurrence of pollution.

Among the paints used for such electrodeposition coating, as the above-mentioned anionic paint, for example, a water-soluble resin obtained by attaching a carboxyl group to a resin having a molecular weight of 2,000 is used. What has been used is one in which an amino group is attached to a resin component of the paint to make it water-soluble. On the other hand, even with these water-soluble paints, the degree of ionization after dissolving in water is weak. For this reason, at present, an alkaline neutralizing agent such as triethylamine is mixed in the case of an aonin type paint, and an acidic neutralizing agent such as acetic acid is mixed in a case of a kaotin type paint, each of which is neutralized and then neutralized in water. Which increase the degree of ionization is used.

As described above, the neutralizing agent for increasing the degree of ionization is mixed according to the properties of the resin component of each paint, but the electrodeposition treatment of the object to be coated proceeds, and the resin component of the paint in the solution is reduced. When the amount decreases, the paint must be sequentially replenished from the outside. Therefore, amine or acetic acid as a neutralizing agent is continuously accumulated in the above-mentioned solution, and phenomena such as re-dissolution of the coated surface or generation of pinholes. And the efficiency of the electrodeposition coating is significantly impaired.

For this reason, in recent years, for example, Japanese Patent Publication No. 45-22231
As seen in the publication, while separating the other electrode from the object to be coated and the aqueous solution as one electrode by an ion exchange membrane or the like, the amine or acetic acid is permeated and extracted from the aqueous solution by the ion exchange membrane or the like. Thus, so-called pH control of preventing an increase in the neutralizing agent in the aqueous solution is performed, and the effect is achieved.

Here, the cationic electrodeposition using the cationic paint will be described.

Conventionally, in cation electrodeposition, an anion exchange membrane has been used as a diaphragm. This anion exchange membrane
Usually, the electrical efficiency of acid removal (coulomb removal rate of acid)
It has a value of 8 to 10 × 10 ⁻⁶ [mol / Coulomb].

The acid (neutralizing agent) added to the aqueous solution for electrodeposition (ED bath paint) in the electrodeposition bath layer is only the amount A contained in the paint supplied to the electrodeposition bath layer.

On the other hand, the acid taken out from the ED bath paint to the outside is 10 to 20% of A taken out and contained in the UF filtrate used as a washing solution after electrodeposition coating. 1010 [%] The total amount B of 70 to 80 [%] of A removed by the diaphragm electrode.

Although it is ideal that the amount A and the amount B are equal, it is difficult to adjust the amount. Therefore, in general, B> A is often supplied from the outside to make the amount of acid insufficient.

For this reason, when all of the electrodes provided in the electrodeposition bath layer are used as diaphragm electrodes, the removal of the acid becomes excessive and causes a deficiency of the acid as a neutralizing agent, and the acid is periodically removed from the outside. For example, it becomes necessary to replenish the acid, and the management of the neutralizing agent in the ED bath paint becomes troublesome, and the acid is wasted. For this reason,
Today, some of the electrodes are made up of so-called bare electrodes without a diaphragm to balance acid removal.

As mentioned above, removal of the acid becomes excessive in removal rate 8 to 10 × 10 ^-6 [mol / Coulomb], and the balance of the 5 to 6 × 10 ^-6 [mol / Coulomb] In approximately ideal acid removal Therefore, a neutral film having such an acid removal rate may be used.

In addition, in cation electrodeposition, it is also possible to use a cation exchange membrane for a part of the diaphragm electrode.

[Problems to be solved by the invention]

However, the above-described method of partially using the bare electrode has the following serious inconveniences in meeting the recent demand for high-quality coating.

That is, sludge mainly composed of an inorganic pigment deposited on the surface of the bare electrode becomes a problem, and among the useful components in the paint, a component that promotes electrolytic corrosion of the electrode (usually SUS316 is often used). Is often included, causing severe electrolytic corrosion when energized. Usually, the electrolytic corrosion rate of SUS316 is about 2 to 3 × 10 ⁻⁶ [gram / coulomb] with respect to the flowing current, but in the above case, it is also 100 to 150 × 10 ⁻⁶ [gram / coulomb]. May reach.

In this way, heavy metal ions (iron, chromium, nickel, etc.) eluted from the poles due to electrolytic corrosion are mixed into the paint,
Obstacles such as roughening of the painted surface, reduced rust prevention, and coloring by heavy metals have occurred.

Further, even in the case of using the above-described conventional neutral film, the neutral film has a similar disadvantage because the neutral film allows components that promote electrolytic corrosion, heavy metal ions, and the like to pass through.

Furthermore, when the above-mentioned conventional cation exchange membrane is used, the coulomb removal efficiency of the acid is very low at 1 × 10 ⁻⁶ [gram / coulomb] or less, and the cation exchange membrane is partially used in all the membranes. Although excessive removal of acid can be prevented by using, the heavy metal ions generated by the elution of the above-mentioned electrode are passed, so that the electric efficiency reaches 3 to 5 × 10 ⁻⁶ [gram / coulomb]. In other words, this means that the use of the cation exchange membrane causes a disadvantage that most of the heavy metal ions eluted from the poles are mixed into the paint.

[Object of the invention]

An object of the present invention is to improve the disadvantages of the conventional example, and particularly, without releasing heavy metals and the like in bath paints.
An object of the present invention is to provide an electrodeposition coating apparatus capable of adjusting the acid removal efficiency.

[Means for solving the problem]

Therefore, in the present invention, the object to be coated as the first electrode portion provided in the electrodeposition bath and the second electrode portion composed of a plurality of electrodes provided corresponding to the object to be coated are formed. And applying an electric current through an aqueous solution of the film-forming substance contained in the electrodeposition bath between the object to be coated and the second electrode portion, thereby electrodepositing the film-forming substance on the object to be coated. It has become. Here, as each electrode constituting the second electrode portion, a diaphragm electrode device having a diaphragm portion that separates each electrode from the aqueous solution is used, and a part of the diaphragm electrode device is used as the diaphragm electrode device. To prevent most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the electrode, and to block the flow of ions that are attracted to the first electrode and flow out of the electrode side of the diaphragm electrode device. In addition to having a diaphragm, the remaining diaphragm electrode is provided with a diaphragm for permeating and extracting the neutralizing agent. This aims to achieve the above-mentioned object.

[Action]

A case where the electrodeposition coating apparatus of the present invention is used for cationic electrodeposition coating will be described.

First, when a DC voltage is applied to the object to be coated as a negative electrode and each of the diaphragm electrode devices constituting the second electrode portion as a positive electrode, electrode coating is started immediately as usual, and a positive charge is applied in an aqueous solution for electrodeposition coating. The colloidal molecules of the coating resin component and the pigment having the above-mentioned composition move toward the coated object of the negative electrode, adhere to the surface of the coated object and discharge, and then the solid matter of the coating aggregates to form a coating film.

On the other hand, acetic acid having a negative charge is accumulated in the aqueous solution, and the acetic acid starts to move toward the electrode of each diaphragm electrode device simultaneously with the start of the above-mentioned electrodeposition coating. For example, when a composite exchange membrane in which a cation exchange membrane is provided on the paint side and an anion exchange membrane is provided on the electrode side is used as a membrane part provided in some of the membrane electrode devices, the cation exchange membrane is used. Since it is on the paint side, the flow of the acid as a neutralizing agent in the aqueous solution is mostly blocked by the cation exchange membrane and cannot reach the electrode side, and the acid is accumulated in the aqueous solution for electrodeposition. However, since this cation exchange membrane does not completely block acetic acid, a part of the cation exchange membrane reaches the electrodes and discharges. On the other hand, the outflow of the heavy metal ions eluted from the electrode to the aqueous solution for electrodeposition is effectively prevented by the action of the anion exchange membrane.

On the other hand, since the remaining diaphragm electrode device has an anion membrane that allows acetic acid molecules having a negative charge to pass easily, acid molecules attracted to the electrode of the diaphragm electrode device having a positive potential are converted into electron flux lines. Along the membrane and easily pass through the anion exchange membrane to reach the electrodes and discharge. In this case, the outflow of the heavy metal ions eluted from the electrode to the electrodeposition aqueous solution side is effectively prevented by the action of the anion exchange membrane as described above.

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

This example shows a case where the present invention is applied to a cationic electrodeposition coating apparatus using a cationic paint.

The embodiment shown in FIG. 1 includes a coating object 1 serving as a first electrode portion provided in an electrodeposition bath 100 and a plurality of electrodes provided for the coating object 1. 2 electrode portions 2. As the electrodes constituting the second electrode unit 2, diaphragm electrode devices 3, 3,... And diaphragm electrode devices 4, 4,.

As the diaphragm electrode device 3, one having a diaphragm portion for permeating and extracting a neutralizing agent in an aqueous solution for electrodeposition coating (aqueous solution of a cationic paint) W accommodated in an electrodeposition bath 100 is used. . Further, the diaphragm electrode device 4 has a first function of preventing most of the flow of ions in the neutralizing agent in the aqueous solution W sucked by the electrodes of the diaphragm electrode device 4, and a suction function of the coating object 1. The one having a diaphragm part having a second function of blocking the flow of ions eluted from the electrode side of the diaphragm electrode device 4 is used.

More specifically, as shown in FIG. 2, the diaphragm electrode device 4 includes a main body 11, an electrode 12, and a water passage mechanism 14 set between the two.

The main body 11 includes first and second insulating tubes 15 and 16 disposed coaxially at a predetermined interval, and each of these insulating tubes 1 and 16.
A relatively hard diaphragm supporting member 17 connecting the diaphragms 5 and 16, a diaphragm portion 9 wound around the outer periphery of the diaphragm supporting member 17, and an outer cloth 18 further wound around the outer surface of the diaphragm portion 9 It is configured. The outer cloth 18 is made of, for example, chemical fiber or the like and has water permeability that is sufficiently durable against tension.

The diaphragm supporting member 17 is formed in a relatively long tubular shape by a non-conductive net-like member or a water-permeable porous member, and the first and second insulating tubes 15 and 16 are provided at inner ends of both ends thereof. It is arranged to be connected.

As shown in FIG. 3, each of the diaphragm portions 9 is formed in a cylindrical shape, and has a cation exchange membrane 7 disposed on the outer side (paint side) and a cation exchange membrane 7 facing the cation exchange membrane 7. Anion exchange membrane 8 disposed on inner electrode 12 side
And a double-structure ion exchange membrane consisting of Outer cation exchange membrane 7 and inner anion exchange membrane 8
Is wound around the outer periphery of the diaphragm support member 17 in a state where both ends are integrally fixed as described later. Actually, since the surfaces of the cation exchange membrane 7 and the inner anion exchange membrane 8 have some irregularities, a certain gap is formed between the opposing portions thereof. Therefore, as shown in FIG. 2, small holes 8a and 8b are formed at the upper and lower ends of the inner anion exchange membrane 8.
Are provided so that the polar liquid always fills the gap between the cation exchange membrane 7 and the anion exchange membrane 8 through these small holes 8a and 8b, so that no voids that hinder energization are generated. I have.

The reason why the diaphragm section 9 has a double structure is that the cation exchange membrane 7 is disposed on the paint side to prevent the flow of the acid (negative ion) as a neutralizing agent in the aqueous solution W (ED bath paint). The cation exchange membrane 7 blocks most of the components, and an anion exchange membrane 8 is disposed on the inner side close to the electrode 30 so that the positive (+) heavy metal ions eluted from the electrode 30 are removed by the anion exchange membrane 8. It is to prevent. That is, the transmittance of an acid cation exchange membrane is a 1 × 10 ^-6 [mol / Coulomb Hereinafter, becomes very small compared to 8 to 1 × 10 ^-6 when the anion exchange membrane used [mol / Coulomb] It is expected that the permeation amount of heavy metal is 4 to 15 × 10 ⁻⁶ [gram / coulomb] when using a cation exchange membrane under the ordinary electrodeposition coating line operating conditions, whereas the anion exchange membrane is This is because, in the case of, it has an extremely low value of 0.025 × 10 ⁻⁶ [gram / coulomb].

Here, if the acid, that is, the negative (-) ion is blocked by the cation exchange membrane 7 and the positive ion is blocked by the anion exchange membrane 8, it is considered that no current flows. The current flows sufficiently.

A portion of the water in the cation exchange film 7 and an anion exchange membrane 8 and the boundary surface [H ^+] and ^- are ionized into [OH]. If pure neutral, degree of ionization [H ^+], [OH ^-] are both 1
The ionization degree is not uniform at the interface between the anion exchange membrane 8 and the cation exchange membrane 7 although it is about 0 ^-7 [mol / liter]. That is, as shown in Figure 4, the surface of the anion exchange membrane 8, because of the presence of such [-NH ₄ ^+] anion-exchange groups, [OH ^-] higher concentration of a cation exchange membrane in the reverse 7
Due to the presence of such a cation exchange group [-SO ₄ ^2-] In the surface of,
[H ⁺ ] concentration is high.

Both [OH ⁻ ] and [H ⁺ ] have extremely high ion mobility, which causes charge transfer.

Further, since the diaphragm portion 9 is wound around the diaphragm support member 17, the mechanical strength against external pressure is significantly enhanced. Further, the outer cloth 18 is spirally wound around the entire outer peripheral surface of the diaphragm portion 9 as described above, so that a sufficient pressure resistance against internal pressure is added. .

A diaphragm supporting member on which the diaphragm portion 9 and the outer cloth 18 are wound
As shown in FIG. 2, first and second frames 20 and 21 are disposed at predetermined intervals on the outer peripheral sides of both ends of the 17. At the same time, potting materials are provided on the inner diameter sides of the frames 20 and 21. 41, whereby the insulating tubes 15, 16 and the diaphragm support member 1 are filled.
7, the diaphragm 9, and the outer cloth 18 are simultaneously and firmly integrated. In this case, the first frame body 20 is formed in a cylindrical shape, and when the potting material 41 is filled, the first frame member 20 has a first ring member 22 to prevent the potting material 41 before solidification from flowing out. Are arranged in the frame 20 of the first embodiment.

The second frame 21 is formed in a bottomed cylindrical shape, and is filled with the potting material 41 as described above in a state where the diaphragm support member 17 and the insulating tube 16 and the like are inserted therein.
The whole is simultaneously and integrally fixed.

Although an epoxy resin is used as the potting material 41 in this embodiment, a urethane resin or a phenol resin may be used.

In the present embodiment, hard vinyl chloride tubes are used as the first and second insulating tubes 15 and 16. 2, the first insulating tube 5 is provided with a drainage portion 13 as shown in FIG. 2, and a cap 24 is detachably provided at an upper end thereof. Reference numeral 15A denotes a spacer fixed to the upper end inner diameter side of the insulating tube 15.

On the other hand, the electrode section 12 includes a tubular electrode 30 made of stainless steel and formed in a tubular shape, and a metal lid member 31 for hanging down the electrode attached to the upper end of the tubular electrode 30 in FIG.
It is composed of a power supply connection terminal 32 and a water supply section 33 provided on the lid member 31. Among them, the tubular electrode 30
Is formed to have an outer diameter smaller than the inner diameter of the first and second insulating tubes 15 and 16 of the main body 11 described above.
For this reason, the attachment / detachment of the tubular electrode 30 to / from the main body 11 is facilitated, and at the same time, the main body 11 and the tubular electrode 30
And a part of the water passage mechanism 14 is formed between them. Further, the metal lid member 31 has an outer peripheral edge projecting from the tubular electrode 30, thereby forming the tubular electrode 30.
Are locked by a first insulating tube 15 as shown in FIG. For this reason, the electrode portion 12 is very easily inserted and arranged in the main body portion 11 from the outside, and can be easily detached to the outside as needed.

The water passage mechanism 14 is for discharging acetic acid and the like accumulated between the diaphragm 9 and the tubular electrode 30 to the outside, and is specifically constituted by the electrode 12 and the main body 11 described above. ing. That is, the water flowing from the water supply part 33 of the electrode part 12 flows down in the tubular electrode 30 as shown by the arrow in FIG. 5, and flows from below to the outer peripheral side of the tubular electrode 30, At the same time, it flows inside the diaphragm portion 9 while ascending on the outer peripheral side of the tubular electrode 30 and is forcibly discharged from the discharge portion 13 to the outside together with impurities.

A mounting bracket 11A to be mounted on a bathtub for electrodeposition coating is wound around one frame 20 of the main body 11.
Further, the outer cloth 18 wound around the outer surface of the diaphragm section 9 is not necessarily limited to a cloth-like one, and may be replaced with another member as long as it has the same reinforcing function and water permeability. . Furthermore, each of the ion exchange membranes constituting the diaphragm section 9 may be wound spirally or may be formed in a ring shape, assuming that the junction is waterproofed.

Here, the method of fixing the diaphragm 9 which is a main part of the main body 11 will be described in more detail.

First, the anion exchange membrane 8 constituting the membrane portion 9 is wound around the outer periphery of the membrane support member 17, and the anion exchange membrane 8 is brought into contact with its end edge to make the anion exchange membrane 8 substantially circular in cross section as shown in FIG. Stick to shape. A cation exchange membrane 7 is wound thereon, and its end is overlapped or its end is abutted to be fixed in a substantially circular cross section as shown in FIG. Subsequently, an outer cloth 18 is spirally wound around the outer surface of the cation exchange membrane 7, whereby the integration of the membrane support member 17 and the membrane section 9 is completed. Next, the above-described first and second insulating tubes 15 and 16 are fitted to both ends of the cylindrical diaphragm member thus formed as shown in FIG. On the outside, the first and second frames 20, 21 are arranged at predetermined intervals as described above. Each potting material 4 is placed in each of the frames 20, 21.
1 is solidified by filling, whereby the integration of the main body 11 is completed.

The seal member 22 disposed inside the lower end portion of FIG. 2 of the first frame body 20 is for preventing the potting material 41 before solidification from flowing out as described above.
After the potting material 41 is solidified, it may be removed.

The diaphragm electrode device 3 has substantially the same configuration as the diaphragm electrode device 4, but a normal anion exchange membrane is used in place of the diaphragm portion 9. Other configurations are the same as those of the diaphragm electrode device 4 described above.

 Next, the overall operation of this embodiment will be described.

First, the object to be coated 1 is used as a negative electrode and the diaphragm electrode devices 3, 3, and
When a DC voltage is applied with each of the tubular electrodes 30 of …… and 4,4,… as a positive electrode, electrode coating starts immediately as usual,
In the aqueous solution, the colloidal molecules of the paint resin component and the pigment having a positive charge move toward the coating object 1 of the negative electrode, adhere to the surface of the coating object and discharge, and then the solid material of the coating aggregates to form a coating. A film is formed.

On the other hand, in the aqueous solution, acetic acid having a negative charge is accumulated, and this acetic acid is generated in the diaphragm electrode devices 3, 3,..., 4, 4,. Movement toward each tubular electrode 30 is started. Here, since each membrane electrode device 3 uses an anion membrane that allows acetic acid molecules having a negative charge to easily pass through, the acetic acid molecules attracted to the tubular electrode of the membrane electrode device 3 having a positive potential are electrons. It easily passes through the anion exchange membrane along the line of force and reaches the tubular electrode 30 from around the tubular electrode 30 to discharge. In this case, almost all of the discharged neutralizing agent is ionized when the concentration is low, and thus the neutralizing agent is attracted to the anode during energization, so that the neutralizing agent is accumulated between the tubular electrode 30 and the anion exchange membrane. by the way,
As described above, for example, pure water is forcibly circulated between the tubular electrode 30 and the anion membrane, and thus the accumulated acetic acid is continuously discharged to the outside together with the pure water.

On the other hand, in each of the membrane electrode devices 4, since the cation exchange membrane 7 is on the paint side, the flow of acetic acid, which is a neutralizing agent, in the aqueous solution W is mostly blocked by the cation exchange membrane 7, and
The acetic acid cannot reach the 30 side and accumulates in the aqueous solution W for electrodeposition. However, since the cation exchange membrane 7 does not completely block acetic acid, a part thereof reaches the electrode 30 and is discharged. In the same manner as described above, acetic acid is accumulated between the tubular electrode 30 and the diaphragm 9, and the accumulated acetic acid is continuously discharged to the outside together with pure water. On the other hand, the anion exchange membrane 8 effectively prevents heavy metal ions eluted from the electrode 30 from flowing out to the electrodeposition aqueous solution W side.

The inventor of the present invention actually measured the acid removal rate and heavy metal permeability of the membrane electrode device in which the membrane portion 9 had a double structure of the cation exchange membrane 7 and the anion exchange membrane 8, and found that the acid removal rate was 1.3 × 10 ^{−. 6} [mol / Coulomb] A heavy metal permeability of 0.058 × 10 ⁻⁶ [g / Coulomb] was obtained.

(This value is somewhat inferior to the individual characteristic value of each of the above-mentioned diaphragms, but this is because, as described above, in the cation exchange membrane 7, the cations moving from the polar solution side become the anion membrane 8. And the charge and carriers passing through the cation membrane 7 are depleted, which tends to carry the charges by the passage of anions (acids). In the anion exchange membrane 8, it is on the paint side. This is because the acid is blocked by the cation exchange membrane 7 and the carrier of the anion is depleted, so that there is a tendency to carry charges by the passage of the cation.) However, the membrane section 9 is formed by the cation exchange membrane 7. And a double structure in which the anion exchange membrane 8 is overlapped, the acid removal rate can be reduced to about 1/7 that of a normal anion exchange membrane used alone, and the permeation of heavy metals is reduced by cations. Exchange 0.058 × 10, about 1/70 of that of the exchange membrane alone
^-6 [gram / coulomb].

As described above, according to the first embodiment, the diaphragm electrode device 4 capable of suppressing the removal rate of acid and preventing the outflow of heavy metal ions due to elution of the electrode, and the anion membrane capable of effectively removing acid. Is used to prevent excessive removal of the acid which is a neutralizing agent, which has been a problem in the past. There is an advantage that the entry of heavy metal ions due to elution of the poles can be almost completely prevented. Further, by appropriately combining the membrane electrode device 3 and the membrane electrode device 4, there is also an advantage that the acid removal rate can be set to a desired value.

Second Embodiment Next, a second embodiment will be described with reference to FIG.

Here, the same reference numerals are used for constituent members equivalent to those in the first embodiment described above.

As shown in FIG. 6, an object to be coated 1 as a first electrode portion is disposed in the center of an electrodeposition bath 100.
Further, in the electrodeposition bath 100, tubular electrodes 30 constituting the second electrode unit 2 corresponding to the object 1 to be coated are disposed at both ends thereof.

Further, between the tubular electrode 30 and the article 1, a diaphragm section 9 that separates each tubular electrode 30 from the aqueous solution W of the cationic paint and the article 1 contained in the electrodeposition bath 100. Is equipped.

This will be described in more detail. The diaphragm section 9 includes a cation exchange membrane 7 provided on the side of the article 1 to be coated and the cation exchange membrane 7.
Exchange membrane 8 arranged on the tubular electrode 30 side opposite to
And is constituted by. These cation exchange membranes 7,
Since the strength of the anion exchange membrane 8 is low, the anion exchange membrane 8 is actually equipped with a non-illustrated non-conductive mesh member or a diaphragm supporting member formed of a water-permeable porous member.
Further, the anion exchange membrane 8 provided on the tubular electrode 30 side is provided with small holes at the upper and lower ends, respectively. Although not shown here, these small holes are actually provided at several places. For this reason, the space between the cation exchange membrane 4 and the anion exchange membrane 5 is not always filled with the polar liquid through these small holes, so that no gap is generated that hinders energization.

Further, on the object 1 side of the diaphragm portion 9, diaphragm electrode devices 3, 3,... Are provided similarly to the first embodiment.

Even in this case, the same operation and effect as those of the first embodiment can be obtained.

Third Embodiment Next, a third embodiment will be described with reference to FIG.

This embodiment is characterized in that a voltage adjusting means 40 for adjusting the voltage applied between the diaphragm electrode devices 3, 3,... Have. Other configurations are the same as those of the first embodiment.

Even with this configuration, the same operation and effect as those of the first embodiment can be obtained, and the voltage applied between each of the diaphragm electrode devices 3 and the object 1 is adjusted by the operation of the voltage adjusting means 40. Therefore, there is an advantage that the amount of acid in the electrodeposition bath 100 can be adjusted more easily.

In the first to third embodiments, the case where the diaphragm 9 has a double structure of the cation exchange membrane 7 and the anion exchange membrane 8 is exemplified. The diaphragm 19 shown in FIG. 9 may be used, or the diaphragm 29 shown in FIG. 9 may be used. As shown in FIG. 8, the diaphragm portion 19 has a base material 26 made of woven nylon or polyethylene, a cation exchange resin 27A on one surface (the surface on the ED bath paint side) 26a, and the other surface (electrode). (A side surface) 26b is a composite exchange membrane formed by coating an anion exchange resin 27B. Further, as shown in FIG. 9, the diaphragm section 29 comprises an anion exchange resin 27B and a cation exchange resin 27A.
This is a composite exchange membrane in which a mixture obtained by mixing at a ratio of 50 to 50 and binding with a binder 27C is coated on both surfaces of a base material 26 made of woven nylon or polyethylene. Microscopically, by mixing both types of exchange resins, the same effect can be obtained as a multi-layered membrane system composed of a cation resin / anion resin / cation resin / anion resin /... The mixing ratio is 10 to 90 to 90
Practical effects in terms of acid removal rate were confirmed even between 10 and 10.

〔The invention's effect〕

Since the present invention is configured and functions as described above, according to this, it is possible to almost completely prevent heavy metal ions from being mixed into the paint component (ED bath paint) in the aqueous solution for electrodeposition by elution of the pole. In addition, it is possible to provide an unprecedented excellent electrodeposition coating apparatus capable of adjusting the acid removal efficiency.

[Brief description of the drawings]

FIG. 1 (1) is an explanatory view showing the arrangement of the diaphragm electrode devices in the first embodiment of the present invention as viewed from above, FIG. 1 (2) is an explanatory view showing the configuration of the first embodiment of the present invention, Figure 2 shows the first
FIG. 3 is a cross-sectional view showing a specific configuration of a part of the membrane electrode device in FIG. 3, FIG. 3 is a cross-sectional view taken along the line III-III of FIG.
FIG. 5 is a diagram for explaining that an electric current flows between the cation exchange membrane and the anion exchange membrane, FIG. 5 is an explanatory diagram showing a flow path of water in the apparatus of FIG. 2, and FIG. FIG. 7 is an explanatory view showing the structure of a second embodiment of the present invention, and FIG.
8 and 9 are explanatory diagrams showing modifications of the first to third embodiments. 1... Coating object as first electrode 2... 2nd electrode
3 ... some diaphragm electrode devices, 4 ... remaining diaphragm electrode device for permeating and extracting a neutralizing agent, 100 ... an electrodeposition bath, W ... an aqueous solution of a cationic paint as an aqueous solution of a film-forming substance.

Claims (2)

(57) [Claims] An object to be coated is provided as a first electrode portion provided in an electrodeposition bath and a second electrode portion including a plurality of electrodes provided corresponding to the object to be coated. An electrodeposition of the film-forming substance on the object by passing an electric current through an aqueous solution of the film-forming substance contained in the electrodeposition bath between the object and the second electrode portion; In the electrodeposition coating apparatus, a diaphragm electrode device having a diaphragm portion for separating each electrode from the aqueous solution is used as each electrode constituting the second electrode, and a part of the diaphragm electrode device is A first function for preventing most of the flow of ions in the neutralizing agent in the aqueous solution attracted to the electrode of the diaphragm electrode device, and a second function for preventing the flow of ions flowing out from the electrode side of the diaphragm electrode device. And the remaining diaphragm electrode Wherein the electrodeposition coating device that is provided with a diaphragm portion which location extracts penetrate the neutralizing agent. 2. The method according to claim 1, wherein at least one of the diaphragm electrode devices having a diaphragm portion for permeating and extracting the neutralizing agent is provided with voltage adjusting means for adjusting a voltage applied to an electrode of the diaphragm electrode device. The electrodeposition coating apparatus according to claim 1, wherein: