JPH0310097A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To drastically reduce acid removal efficiency without releasing heavy metals, etc., into a coating material in a bath by opposing a material to be coated as a first electrode to a second electrode in an electrodeposition bath and furnishing a diaphragm part having a specified function between both electrodes. CONSTITUTION:The material 1 to be coated is set at the center of an electrodeposition bath 100 as a first electrode, and the second electrode 2 formed with a tubular electrodes 30 is set on both ends in opposition to the material 1. The diaphragm part 3 is provided respectively between the material 1 and the tubular electrode 30, the diaphragm part 3 is formed with a cation-exchange membrane 4 on the material 1 side and an anion-exchange membrane 5 on the tubular electrode 30 side, and several small holes 5a and 5b are provided on the upper and lower ends of the anion-exchange membrane 5. Consequently, the flow of the anion of the acid as the neutralizer in the cationic coating aq. soln. W is blocked by the cation-exchange membrane 4, and the flow of the positive heavy metal ion eluted from the tubular electrode 30 is blocked by the anion-exchange membrane 5. A high-quality finished coating is formed on the material 1 in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrodeposition coating method. The present invention relates to an electrodeposition coating method for electrodepositing a film-forming substance onto an object.

[Conventional technology]

Electrodeposition coatings can be roughly divided into those using anionic paints and those using cationic paints, but in both cases, the uniformity and adhesion of the coating to the object are excellent. In addition, because it generates little pollution, it has recently been widely applied, for example, to automatic coating treatment of automobile bodies, as it is especially suitable for undercoating or one-coat finishing of metal coatings.

Among the paints used in such electrodeposition coatings, the above-mentioned anionic paints include those made water-soluble by attaching carboxyl groups to a resin with a molecular weight of 2,000, and the cationic paints include The paint used is one in which an amino group is attached to the resin component of the paint to make it water-soluble. On the other hand, even these water-soluble paints have a weak degree of ionization after being dissolved in water. For this reason, at present, in the case of anionic paints, an alkaline neutralizer such as triethylamine is mixed in, and in the case of cationic paints, an acidic neutralizer such as acetic acid is mixed in, and these are neutralized and soaked in water. A material designed to increase the degree of ionization is used.

・In this way, a neutralizing agent is mixed in to increase the degree of ionization depending on the properties of the resin component of each paint, but on the other hand, as the electrodeposition process progresses on the object to be coated, the resin components of the paint in the solution When the paint decreases, the paint must be sequentially replenished from the outside, and amine or acetic acid as a neutralizing agent is continuously accumulated in the solution, causing problems such as re-dissolution of the painted surface or the formation of pinholes. A phenomenon occurs in which the efficiency of electrodeposition coating is significantly impaired.

For this reason, in recent years, for example,
As seen in Publication No. 31, one electrode part is separated from the object to be coated and the aqueous solution using an ion exchange membrane or the like, and the ion exchange membrane or the like separates the amine or the like from the aqueous solution. So-called pH control, which prevents an increase in the amount of the neutralizing agent in the aqueous solution by permeating and extracting acetic acid, is being carried out and is being tried to be effective.

Here, cationic electrodeposition using a cationic paint will be explained.

Conventionally, anion exchange membranes have been used as diaphragms in cationic electrodeposition. This anion exchange membrane usually has an electrical efficiency of acid removal (coulomb removal rate of acid) of 8.
It has a value of ~1 Oxlo-' (mol/coulomb).

Added to the electrodeposition aqueous solution (ED bath paint) in the electrodeposition bath layer! The (neutralizing agent) is only IA contained in the paint supplied to the electrodeposition bath layer.

On the other hand, the acids carried out from the ED bath paint include: ■ 10 to 20 (%) of the A contained in the UF filtrate used as a washing liquid after electrodeposition coating; ■ A carried out contained in the paint film. (5 to 10 (%)) of (1) 70 to 80 (%) of A removed by the diaphragm electrode.

Ideally, iA and IB should be equal, but since this is difficult to adjust, generally B>A is established, and acid that is running low is often replenished from the outside.

For this reason, if all the electrodes installed in the electrodeposition bath layer are diaphragm electrodes, the removal of acid will be extremely excessive, resulting in a lack of acid, which is a neutralizing agent, and the electrodes will be periodically removed from the outside. Managing the neutralizing agent in the ED bath paint becomes troublesome, as acid needs to be replenished, and acid is wasted. For this reason, today, acid removal is balanced by configuring the electrodes as so-called bare electrodes without a diaphragm.

As mentioned above, a removal rate of 8~toxio-''cmol/coulomb results in excessive acid removal;
Since h (mol/coulomb) provides an approximately ideal acid removal balance, a neutral membrane having such an acid removal rate may be used in some cases.

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

[Problem that the invention sought to solve]

However, the above-mentioned conventional technique in which bare electrodes are partially used has the following serious disadvantages in meeting the recent demands for high-quality coating finishes.

That is, sludge mainly composed of inorganic pigments deposited on the surface of bare electrodes becomes a problem, and among the useful components in the paint, there are components that promote electrolytic corrosion of the electrodes (usually 5US316 is often used). It often contains , which causes severe electrolytic corrosion when energized. Normally, the electrolytic corrosion rate of 5US316 is about 2~3X10-'' [Durham/Coulomb] with respect to the flowing current, but in the above case, it is 100~150X
IQ-6 (grams/coulomb) can be reached.

In this way, heavy metal ions (iron, chromium, nickel, etc.) eluted from the electrodes due to electrolytic corrosion were mixed into the paint, causing problems such as roughening of the painted surface, reduced rust prevention ability, and coloring problems caused by heavy metals. .

Further, even in the case of using a neutral membrane in the conventional example described above, the same problem occurred because the neutral membrane allows 1 g of 5 heavy metal ions, etc., which promote electrolytic corrosion, to pass through.

Furthermore, when using the conventional cation exchange membrane described above, the coulomb removal efficiency of acid is very low, less than 1X10-' [Durham/Coulomb], and the cation exchange membrane is used as a part of the entire diaphragm. By doing so, excessive removal of acid can be prevented, but since the heavy metal ions generated by the elution of the electrode mentioned above are passed through, the electrical efficiency is 4 to 15X10-b.
(gram/coulomb). In other words, this means that when a cation exchange membrane is used, most of the heavy metal ions eluted from the electrodes are mixed into the paint.

[Purpose of the invention]

An object of the present invention is to provide an electrodeposition coating method which can improve the disadvantages of the conventional methods and, in particular, can effectively reduce the acid removal efficiency without releasing heavy metals etc. into the bath paint. There is a particular thing.

[Means to solve the problem]

Therefore, in the present invention, an object to be coated as a first electrode portion disposed in an electrodeposition bath and a second electrode consisting of one or two electrodes disposed corresponding to this object to be coated are provided. and an electrode section. The coating film-forming substance is electrodeposited onto the coating material by passing an electric current through an aqueous solution of the coating film-forming substance contained in the electrodeposition bath between the coating material and the second electrode part. It has become. Here, a first function of blocking most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the second electrode part, and a second function of blocking most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the second electrode part. A method is adopted in which the second electrode part is separated from the aqueous solution by a diaphragm part having a second function of blocking the flow of ions flowing out from the side. This is an attempt to achieve the above-mentioned purpose.

[For production]

The case where the electrodeposition coating method of the present invention is used in cationic electrodeposition coating will be explained.

First, an object to be coated as a first electrode portion and a second electrode portion were placed in an aqueous solution of a cationic paint neutralized with acetic acid, and the object to be coated was used as a negative electrode. DC voltage is applied to the area as the king's authority. Then, the first function of the diaphragm part blocks most of the flow of acetic acid (anion), which is a neutralizing agent in the aqueous solution, and the second function causes it to be attracted to the first electrode part and then to the second electrode part. The flow of cations eluting from the side is blocked.

The method according to claim 2, wherein a cation exchange membrane is disposed on the side of the object to be coated which is the first electrode part, and an anion exchange membrane is disposed on the second electrode part side opposite to this cation exchange membrane. Taking the invention as an example to explain that a current flows between the reexchange membranes, a portion of the water at the interface between the cation exchange membrane and the anion exchange membrane is ionized into [H"] and (OH-). At the interface between the anion exchange membrane and the cation exchange membrane, the degree of ionization is uneven, and on the surface of the anion exchange membrane, due to the presence of anion exchange groups such as (-NH, °), the concentration of (OH-3 is high, Conversely, on the surface of the cation exchange membrane, the concentration of [H+] is high due to the presence of cation exchange groups (-SO, Z-3, etc.).
The rate of ion movement is extremely high, which causes charge movement. In the case of the invention described in the other claims as well, current flows between the re-exchanged resin parts based on the same principle.

In this way, since current flows between the re-exchange membranes, electrode coating starts immediately, and colloidal molecules of paint resin components and pigments that have positive charges in the aqueous solution move toward the negative electrode to be coated. After adhering to the surface of a painted object and generating an electric discharge, the solid matter of the paint aggregates to form a paint film.

[First Embodiment] Hereinafter, a first embodiment of the present invention will be described based on FIGS. 1 and 2.

This example shows the use of the electrodeposition coating method of the present invention for cationic electrodeposition.

As shown in FIG. 1, an object 1 to be coated 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 section 2 are arranged at both ends thereof, corresponding to the object 1 to be coated.

Although not shown here, several tubular electrodes 30 are actually provided.

Further, between these tubular electrodes 30 and the object 1 to be coated, there is a diaphragm portion 3 for separating each tubular electrode 30 from the aqueous solution W of the cationic paint contained in the electrodeposition bath 100 and the object 1 to be coated. is equipped with.

To explain this in more detail, the diaphragm portion 3 includes a cation exchange membrane 4 disposed on the side of the object to be coated l and an anion exchange membrane 5 disposed on the tubular electrode 30 side opposite to the cation exchange membrane 4.
It is composed of.

These cation exchange membranes4. Since the anion exchange membrane 5 has low strength, it is actually installed together with a diaphragm support member (not shown) formed of a non-conductive rope member or a water-permeable porous member. Further, the anion exchange membrane 5 disposed on the tubular electrode 30 side has small holes 5a and 5 at the upper and lower ends.
b are provided respectively. These small holes 5a, 5b
Although not shown here, they are actually provided at several locations. For this reason, these small holes 5a.

The polar liquid always fills the gap between the cation exchange membrane 4 and the anion exchange membrane 5 via the membrane 5b, so that no gap is generated that would impede current flow.

The reason why the diaphragm section 3 is constructed by doubly disposing a cation exchange membrane 4- and an anion exchange membrane 5 is that the cation exchange membrane 4 on the paint side acts as an acid that is a neutralizing agent in the aqueous solution W. This is to prevent the flow of anions in the tube, and also to block positive (+) heavy metal ions eluted from the tubular electrode 30 by the anion exchange membrane 5 on the tubular electrode 30 side. That is, the acid permeability of the cation exchange membrane is lXl0-' (mol/
coulomb] or less, and 8 to 1 when using an anion exchange membrane.
It is expected that the permeation amount of heavy metals will be much smaller than 0 [grain/coulomb], whereas in the case of anion exchange membrane, it is 0.025
This is because it has an extremely low value of 'C grams/coulomb].

Here, when a DC voltage is applied with the object 1 to be coated as a negative electrode and the tubular electrode 30 as a positive electrode, acetic acid (anion), which is a neutralizing agent in the aqueous solution W, is ) is mostly blocked, and the flow of metal ions (cations) that are attracted to the object 1 to be coated and eluted from the tubular electrode 30 side is blocked by the action of the anion exchange membrane 5.

Here, it is generally believed that if the acid, that is, the negative (-) ions are blocked by the cation exchange membrane 4 and the positive ions are blocked by the anion exchange membrane 5, no current will flow. For some reason, a sufficient amount of current actually flows.

A portion of the water at the interface between the cation exchange membrane 4 and the anion exchange membrane 5 is ionized into [H゛] and (OH-3. In the case of neutral purity, the degree of this ionization is (H'') ,(OH
-) are both about 10-' (mol/liter), but
At the interface between the anion exchange membrane 5 and the cation exchange membrane 4, the degree of ionization is uneven. That is, as shown in FIG. 2, on the surface of the anion exchange membrane 5, the anion exchange group (-
NH1], etc., the concentration of (OH-3 is high (, conversely, the surface of the cation exchange membrane
4''-), etc., the concentration of [H゛] is high.

Both (OH-) and (H') have extremely high ion transfer rates, which causes charge transfer.

In this way, the cation exchange membrane 4 and the anion exchange membrane 5
As a current flows between them, electrode coating starts immediately, and colloidal molecules of paint resin components and pigments that have a positive charge in the aqueous solution W move toward the negative electrode to be coated 1. After adhering to the surface of the coating material 1 and generating an electric discharge, the solid matter of the coating material aggregates to form a coating film.

As explained above, according to the present embodiment, the diaphragm portion 3
The cation exchange membrane 4 that constitutes the cation exchange membrane 4 blocks most of the flow of acetic acid (anion), which is a neutralizing agent in the aqueous solution W, which is attracted to the tubular electrode 30, and the anion exchange membrane 5 prevents the flow of acetic acid (anion), which is a neutralizer, Since the flow of cations eluted from the tubular electrode 30 side is blocked, the acid removal rate can be significantly lowered compared to the conventional cationic electrodeposition coating method using an anion exchange membrane, and the electrode There is an advantage that heavy metals can be effectively prevented from flowing out from the 30 side to the paint side.

[Second Embodiment] Next, a second embodiment will be described based on FIGS. 3 to 6.

In this embodiment, the present invention is similarly applied to cationic coating, but specifically shows the case where the diaphragm electrode device 10 shown in FIG. 3 is used as the second electrode section.

This diaphragm electrode device 10 is actually arranged in an aqueous solution W for electrodeposition coating in correspondence with the object 1 to be coated as a first electrode portion, as shown in FIG.

This is used as the second electrode section.

This diaphragm electrode device 10 includes a main body portion 11, an electrode portion 12 as a second electrode portion, and a water passage mechanism 14 set between the two.

The main body portion 11 includes first and second insulating tubes 15.16 coaxially arranged at a predetermined interval, and a relatively hard diaphragm support member 1 that connects each of these insulating tubes 15.16.
7, a diaphragm portion 9 wrapped around the outer periphery of the diaphragm support member 17, and an outer cloth 18 further wrapped around the outer surface of the diaphragm portion 9.
It is composed of. The outer cloth 18 is made of, for example, chemical fiber, and is sufficiently durable against tension and has water permeability.

The diaphragm support member 17 is formed into a relatively long tube shape using a non-conductive net member or a water-permeable porous member, and supports the first and second insulating tubes 15 and 16 on the inner diameter side of both ends thereof. Arranged to connect.

Further, the diaphragm portion 9 is formed in a cylindrical shape, as shown in FIGS. 3 and 4.

A double-structured ion exchange membrane consisting of a cation exchange membrane 7 disposed on the outside (paint side) and an anion exchange membrane 8 disposed on the inner electrode part 12 side opposite to this cation exchange membrane 7. It is made up of.

To explain this in more detail, the outer cation exchange membrane 7 and the inner anion exchange membrane 8 are wound around the outer periphery of the diaphragm support member 17 with both ends integrally fixed to each other, as will be described later. ing. In reality, the surfaces of these cation exchange membranes 7 and anion exchange membranes 8 are somewhat uneven, so that a certain amount of voids are formed between the opposing portions of the membranes. For this reason, small holes 8a and 8b are provided at the upper and lower ends of the inner anion exchange membrane 20, respectively, as shown in FIG. The space between the anion exchange membrane 8 and the anion exchange membrane 8 is filled to prevent the generation of voids that would impede current flow.

Further, since the diaphragm portion 9 is wound around the diaphragm support member 17, its mechanical strength against external pressure is significantly increased. Furthermore, the outer cloth 18 is spirally wrapped around the entire outer circumferential surface of the diaphragm portion 9 as described above, thereby adding sufficient pressure resistance against internal pressure. .

As shown in FIG. 3, first and second frames 20 and 21 are arranged at a predetermined interval on the outer periphery of both ends of the diaphragm support member 17 around which the diaphragm portion 9 and the outer cloth 18 are wound. established,
At the same time, the botting material 4 is attached to the inner diameter side of this frame 20.21.
1, thereby each of the insulating tubes 15, 16
and the diaphragm support member 17 and the diaphragm portion 9. It has a structure in which the outer cloth 18 is simultaneously and firmly integrated. In this case, the first frame 20 is formed into a cylindrical shape, and when filling the botting material 41, a ring member 22 is installed to prevent the botting material 11 before solidification from flowing out. It is disposed within the first frame 20. The second frame 21 is formed into a cylindrical shape with a bottom, and the diaphragm support member 17, the insulating tube 16, etc. are inserted into the second frame 21, and the botting material 41 is filled as described above. The entire structure is fixed together at the same time.

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

In this embodiment, hard vinyl chloride pipes are used as the first and second insulating pipes 15 and 16. Among them, the first insulating pipe 15 has a drainage section 1 as shown in FIG.
3, and a cap 24 is removably attached to its upper end.

Reference numeral 15A indicates a spacer fixed to the inner diameter side of the upper end of the insulating tube 15.

On the other hand, the electrode section 12 includes a tubular electrode 30 made of stainless steel and formed into a tubular shape, and a metal lid member 3 for locking the electrode hanging, which is attached to the upper end of the tubular electrode 30 in FIG.
1 and a power supply connection terminal 32 provided on this lid member 31
and a water supply section 33. Among these, the tubular electrode 30 is formed so that its outer diameter is smaller than the inner diameter of each of the first and second insulating tubes 15 and 16 of the main body portion 11 described above. Therefore, the tubular electrode 30 can be easily attached to and removed from the main body 11, and at the same time, a part of the water passage mechanism 14 is formed between the main body 11 and the tubular electrode 30. . Further, the outer peripheral edge of the metal lid member 31 projects from the tubular electrode 30, so that the tubular electrode 30 is locked by the first insulating tube 15 as shown in FIG. It looks like this. Therefore, the electrode portion 12 can be inserted into the main body portion 11 from the outside very easily, and can be easily removed from the electrode (to the outside) if necessary.

The water passage mechanism 14 is for discharging acetic acid and the like accumulated between the diaphragm section 9 and the tubular electrode 30 to the outside, and is specifically composed of the electrode section 12 and the main body section 11 described above. ing. That is, the water flowing from the water supply part 33 of the electrode part 12 flows down inside the tubular electrode 30, as shown by the arrow in FIG. 6, and flows from below to the outer circumferential side of the tubular electrode 30. At the same time, it flows inside the diaphragm part 9 while rising on the outer peripheral side of the tubular electrode 30, and flows into the discharge part 13 together with impurities.
It is now forcibly leaked from the outside.

An attachment fitting 11A for attachment to a bathtub during electrodeposition coating is wrapped around one frame 20 portion of the main body portion 12. Further, the outer cloth 8 wrapped around the outer surface of the diaphragm portion 9 is not necessarily limited to a cloth-like material, and may be replaced with another material as long as it has the same reinforcing function and water permeability. . Furthermore, each ion exchange membrane constituting the diaphragm section 9 is
On the premise that the joint portion is waterproof, it may be wound spirally or may be formed into circular slices.

Here, the method of fixing the diaphragm portion 9, which constitutes the main portion of the main body portion 11 mentioned above, will be described in more detail.

First, the anion exchange membrane 8 constituting the diaphragm portion 9 is wound around the outer periphery of the diaphragm support member 17, and the abutting edges of the anion exchange membrane 8 are brought together so that the anion exchange membrane 8 has a substantially circular cross section as shown in FIG. Stick to shape. The cation exchange membrane 7 is wound on top of this membrane, and its abutting ends are overlapped or abutted against each other, and the cation exchange membrane 7 is fixed in a substantially circular cross-section as shown in FIG. Subsequently, the outer cloth 18 is spirally wound around the outer surface of the cation exchange membrane 7, thereby completing the integration of the diaphragm support member 17 and the diaphragm portion 9.

Next, the first and second insulating tubes 15 and 16 described above 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 a predetermined interval as described above. Then, each frame body 20, 2
The botting material 41 is filled into each of the holes i and solidified, thereby completing the integration of the main body portion 11.

The sealing member 22 disposed inside the lower end of the first frame 20 in FIG. 3 is for preventing the unsolidified botting material 4I from flowing out, as described above. After the botting material 41 is solidified, it may be removed. ''Here, when the object to be coated 1 and the diaphragm electrode device 10 are placed in the aqueous electrodeposition solution W, and the object to be coated 1 is used as a negative electrode, and the tubular electrode 30 of the diaphragm electrode device IO is used as an awn seed, a DC voltage is applied. , electrode coating starts immediately as usual, and colloidal molecules of paint resin components and pigments that have positive charges in the aqueous solution move toward the negative electrode to be coated.
After the paint adheres to the surface and discharges, the solids of the paint aggregate to form a paint film.

On the other hand, acetic acid having a negative charge is accumulated in the aqueous solution W, and this acetic acid starts moving toward the tubular electrode 30 of the diaphragm electrode assembly M10 at the same time as the above-mentioned electrodeposition coating starts. do. Here, in this embodiment, since the cation exchange membrane 7 is on the paint side, the aqueous solution W for electrodeposition coating is
The flow of acetic acid, which is a neutralizing agent, flows through this cation exchange membrane 7.
Most of the acetic acid is blocked and cannot reach the tubular electrode 30 side, and acetic acid is accumulated in the electrodeposition aqueous solution W.

However, since this cation exchange membrane 7 does not completely block acetic acid, a portion of it reaches the tubular electrode 30 and is discharged. In this case, since the discharged neutralizing agent, acetic acid, has a low concentration (several percent in this example), almost the entire amount is ionized. Therefore, acetic acid having a negative charge is attracted to the anode, which is the tubular electrode 30, during current application, and therefore, acetic acid is accumulated between the tubular electrode 30 and the diaphragm portion 9. On the other hand, since pure water is forced to flow between the tubular electrode 30 and the diaphragm portion 9 as described above, the accumulated acetic acid is continuously discharged to the outside together with the pure water. on the other hand,
The action of the anion exchange membrane 8 effectively prevents the heavy metal ions eluted from the electrode 30 from flowing out to the electrodeposition aqueous solution side.

The inventor actually measured the acid removal rate and heavy metal permeability in this case, and found that: (1) Acid removal rate: 1.3 x 10-6 [mol/cou 0710 Heavy metal permeability: 0.058 x 10-6 C grams/coulomb] .

(This value is somewhat inferior to the individual characteristic values of each diaphragm mentioned above, but this is because in the cation exchange membrane 7, cations moving from the polar liquid side are blocked by the anion exchange membrane 8. There is a shortage of charges and carriers passing through the cation exchange membrane 7, and there is a tendency for anions (acids) to pass through to carry charges. The acid is blocked by 7,
This is because there is a shortage of anion carriers, so there is a tendency for charge to be carried through the passage of the separated ions.

) However, the diaphragm portion 9 is separated by a cation film 7 and an anion film 8.
By creating a double structure in which cation exchange membranes are superimposed, the acid removal rate can be reduced to about 1/7 of that of conventional anion exchange membranes, and the permeation of heavy metals is also about 1/70 of that of a cation exchange membrane alone. 0.05sxio-” (gram/coulomb)
I was able to keep it down to

As explained above, according to the second embodiment, the second electrode section disposed corresponding to the object 1 serving as the first electrode section is the tubular electrode 30, and the area around the tubular electrode 30 is , a diaphragm part 9 is laminated with a diaphragm support member 17 made of an insulating material interposed therebetween, and this diaphragm part 9 is connected to an anion exchange membrane 8 on the electrode 30 side.
The cation exchange membrane 7 prevents the flow of ions in the electrodeposited aqueous solution W attracted to the tubular electrode 30, and the anion exchange membrane 8 prevents the flow of ions from the electrodeposited aqueous solution W to the object to be coated. By adopting a method of blocking the flow of ions that are attracted to the membrane and eluted from the tubular electrode 30 side, the acid removal rate can be significantly lowered compared to the conventional diaphragm electrode device using an anion exchange membrane. This has the advantage that it is possible to effectively prevent heavy metals from flowing out from the electrode side to the paint side, and that paint sludge is not generated because the electrode 30 is not exposed. Further, due to the action of the diaphragm support member 17, it can sufficiently withstand the above-mentioned external pressure fluctuations, so that it can be used continuously for a long time. Since the structure is configured so that water is forced to flow upward, polarized particles and air bubbles stagnant around the tubular electrode 30 can be forcibly removed, and water permeability is maintained around the outer surface of the diaphragm portion 9. Since the outer cloth 18 is wound, there is an advantage that even if the tensile strength of the diaphragm portion 9 is extremely low, it can sufficiently withstand changes in internal pressure.

For this reason, the diaphragm electrode device 1 configured and functioning as described above
By using a plurality of 0 tubes placed in an aqueous solution for electrodeposition together with a diaphragm electrode device equipped with a conventional anion exchange membrane, it is possible to prevent excessive removal of acid, which is a neutralizing agent, which has been a problem in the past, and also to improve electrodepositing. It becomes possible to almost completely prevent heavy metal ions from being mixed into the paint component (ED bath paint) in the wear aqueous solution due to the elution of the electrode.

[Third Embodiment] Next, a third embodiment will be described based on FIGS. 7 and 8.

This third embodiment uses a diaphragm electrode device 40 shown in FIG. 7 in place of the diaphragm electrode device 10 described above.

This diaphragm electrode device 40 has a main body portion 41 having a substantially U-shaped cross section.
and a diaphragm section 19 that is removably attached to this main body section 41.
It is equipped with

Among these, as the diaphragm portion 19, as shown in FIG. 8, a base material 26 made of woven fabric of nylon or polyethylene is used.
A composite exchange membrane is used in which one surface (paint side surface) 26a is coated with cation exchange resin 27A and the other surface (electrode 30 side surface) 26b is coated with anion exchange resin 27B. In reality, it is integrally fixed to a diaphragm support member (not shown) and is detachably attached to the main body part 41.

A tubular electrode 30 is used as the second electrode, and when the device is used, the main body 41 is filled with an electrolyte, similar to the diaphragm electrode device IO.

A case where this diaphragm electrode device 40 is used for cationic electrodeposition coating will be explained.

First, in an aqueous solution W of a cationic paint neutralized with acetic acid, an object 1 to be coated as a first electrode portion and a diaphragm electrode device t4 are placed.
0 and the object to be coated 1 was used as a negative electrode, and the diaphragm electrode device 2
DC voltage is applied using the 40 tubular electrodes 3o as positive electrodes.

Then, as in the first and second embodiments described above, electrode coating is immediately started, and colloidal molecules of paint resin components and pigments having positive charges in the aqueous solution W move toward the negative electrode to be coated 1. After adhering to the surface of the object to be coated and generating an electric discharge, the solid matter of the paint aggregates to form a coating film. In this case, the same action as shown in FIG. 2 is performed within the diaphragm 19,
A current flows between the layer of cation exchange resin 27A and the layer of anion exchange resin 27B that constitute the diaphragm portion 19.

On the other hand, the negatively charged acetic acid in the aqueous solution starts moving toward the electrodes of the diaphragm electrode device 40 at the same time as the electrodeposition coating starts, as described above. At this time, the flow of acetic acid is mostly blocked by the action of the layer of cation exchange resin 27A on the paint side.

On the other hand, the action of the anion exchange resin 27B layer on the tubular electrode 30 side prevents the heavy metal ions eluted from the tubular electrode 30 from flowing out to the electrodeposition aqueous solution W side.

According to the third embodiment configured as described above, the first.
In addition to obtaining the same effect as the second embodiment, the diaphragm portion 19
Since it is removable, it also has the advantage that the replacement work of the diaphragm part 19 becomes easier.

[Fourth example] Next, a fourth embodiment will be described based on FIG. 9.

This fourth embodiment is characterized in that a diaphragm section 29 is used in place of the diaphragm section 9 of the second embodiment described above. As shown in FIG. 9, this diaphragm portion 29 is made of a mixture 28 made by mixing powder of anion exchange resin 27B and powder of cation exchange resin 27A at a ratio of 50:50 and binding them with a binder 27C. This is a composite exchange membrane formed by coating both sides of a base material 26 made of a polyethylene woven fabric. The other configurations are the same as those of the second embodiment described above.

Even in this case, the same effect as in the second embodiment described above could be obtained.

Microscopically, by mixing both types of exchange resins, this has the same effect as a multilayer diaphragm system with cation resin/anion resin/cation resin/anion resin/... It is thought that this is because

In addition, a practical effect in terms of acid removal rate was confirmed even when the mixing ratio was between 90 and 90:10. As described above, this embodiment also has the advantage that the acid removal rate can be set to various values simply by changing the mixing ratio.

(Effects of the Invention) As explained above, according to the present invention, the second electrode part disposed corresponding to the object to be coated as the first electrode part is attracted to the second electrode part. The first function is to block most of the flow of ions in the neutralizer in the aqueous solution of the coating film-forming substance, and to block the flow of ions that are attracted to the first electrode part and flow out from the second electrode side. Since the membrane is separated from the aqueous solution by the diaphragm having the second function, for example, when this is used in cationic electrodeposition coating as in the above example, the acid removal rate is lower than that of the conventional one. It has the unprecedented effect of being able to significantly reduce the amount of metals compared to the electrodeposition coating method using an anion exchange membrane, and effectively preventing heavy metals from flowing from the electrode side to the paint side. be.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of the first embodiment of the present invention, and FIG.
The figure is a diagram for explaining that a current flows between the cation exchange membrane and the anion exchange membrane in the embodiment shown in FIG. 1, and FIG. 3 shows the diaphragm electrode device used in the second embodiment of the present invention. A sectional view showing a specific configuration, FIG. 4 is a TV-
5 is an explanatory diagram showing the actual usage state of the diaphragm electrode device shown in FIG. 3; FIG. 6 is an explanatory diagram showing the flow path of water in the device in FIG. 3; FIG. 7 is an explanatory diagram showing the third embodiment of the present invention, FIG. 8 is an explanatory diagram showing the specific configuration of the diaphragm section in the embodiment of FIG. 7, and FIG. It is an explanatory view showing a concrete composition of a diaphragm part. ■・・・・・・Object to be coated as the first electrode part, 2...
...Second electrode part, 3...Diaphragm part, 4...
... Cation exchange membrane, 5 ... Anion exchange membrane, 100 ... Electrodeposition bath, W ... Aqueous solution for electrodeposition coating. Figure 1 Figure 5 Figure 5 Figure 0 Figure! 619- Figure δ Figure δ Figure

Claims (5)

[Claims] (1) An object to be coated as a first electrode section disposed in an electrodeposition bath, and a second electrode section consisting of one or more electrodes disposed corresponding to the object to be coated; The film-forming substance is electrically applied to the object to be coated by passing 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. A first function of blocking most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the second electrode part, and a first function of blocking most of the flow of ions in the neutralizer in the aqueous solution that is attracted to the second electrode part; An electrodeposition coating method, characterized in that the second electrode part is separated from the aqueous solution by a diaphragm part having a second function of blocking the flow of ions flowing out from the second electrode part side. (2) The diaphragm section is composed of a cation exchange membrane and an anion exchange membrane disposed opposite to the cation exchange membrane, and the exchange membrane on the side of the object to be coated attracts the suction to the second electrode section. While blocking most of the flow of ions in the neutralizing agent in the aqueous solution, the ions are attracted to the first electrode by the exchange membrane on the second electrode side and from the second electrode side. 2. The electrodeposition coating method according to claim 1, further comprising blocking the flow of outflowing ions. (3) The diaphragm part has a double structure consisting of a cation exchange membrane and an anion exchange membrane, and the neutralizing agent in the aqueous solution is attracted to the second electrode part by the exchange membrane on the side of the object to be coated. In addition to blocking most of the ion flow inside,
2. The electrodeposition coating method according to claim 1, wherein the flow of ions attracted to the first electrode section and flowing out from the second electrode section is blocked by an exchange membrane on the second electrode section side. . (4) The diaphragm section is configured to include a base film, one surface of the base film is coated with a cation exchange resin, the other surface is coated with an anion exchange resin, and the surface on the side of the object to be coated is coated with a cation exchange resin. The coated exchange resin blocks most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the second electrode part, and the exchange resin coated on the surface on the second electrode part side 2. The electrodeposition coating method according to claim 1, wherein the resin prevents the flow of ions attracted to the first electrode section and flowing out from the second electrode section. (5) The diaphragm section is configured to include a base film, both sides of the base film are coated with a mixture of an anion exchange resin and a cation exchange resin in a predetermined ratio, and the diaphragm section blocking most of the flow of ions in the neutralizing agent in the aqueous solution that is attracted to the second electrode part, and the flow of ions that are attracted to the first electrode part and flow out from the second electrode part side. 2. The electrodeposition coating method according to claim 1, further comprising the step of preventing: