JPS5980794A - Electrodeposition painting device - Google Patents

Abstract

PURPOSE:To prevent easily the formation of any hash mark on the paint coated film surface of a substrate by juxtaposing plural diaphragm chambers in an electrodeposition cell, and cooling the diaphragm water in the diaphragm chamber on the inlet part thereof with a cooler thereby decreasing the conductivity thereof. CONSTITUTION:Plural diaphragm chambers 3 are juxtaposed on both sides in an electrodeposition cell 1, and are divided to a diaphragm chamber 3b in which the conductivity of the diaphragm water has a prescribed value (about 400-500muOMEGA/ cm) and the diaphragm chamber 3a of the lower conductivity (about 50-100muOMEGA/ cm). Said chambers are connected respectively through circulation circuits 9, 10 to storage tanks 11, 12, so that the diaphragm water is circulated by a pump P to the chambers 3a, 3b. The diaphragm water in the tank 11 is cooled by a cooler Co to decrease the conductivity thereof down to a prescribed low value. When the conductivity of the diaphragm water increases on progressing of the painting, valve driving devices 19, 20 open stop valves 17, 18 in accordance with the values detected with detectors 21, 22 to supply pure water to the tanks 11, 12 thereby maintaining the conductivity of the diaphragm water at the prescribed value.

Description

[Detailed description of the invention] The present invention relates to improvements in electrodeposition coating equipment.

Conventionally, one electrode is provided in an electrodeposition tank filled with water-dispersible or water-soluble electrodeposition paint, and the object to be coated that is transported in the electrodeposition tank is used as the other electrode, and the coating is applied between the two electrodes. A method is known in which electrocoating paint is deposited on the object to be coated by applying a constant direct current using a so-called energization tank method in which electricity is applied before the object is immersed in the electrodeposition bath. According to this electrodeposition coating, it is possible to paint automobile bodies etc. fairly well, but as mentioned above, it is carried out by passing a constant DC current between the electrode and the object to be coated using the energized bath method. However, when the object to be coated is placed in the electrodeposition tank, a large current flows through the object partially immersed in the electrodeposition tank, resulting in formation of 7. tsch marks, that is, ripples, on the surface of the coating film.

In order to prevent the formation of hash marks on the coating surface, in Japanese Patent Publication No. 4-'11477, the current flowing between the object to be coated and the electrode is changed in the conveying direction of the object to be coated. We have proposed an electrodeposition coating method in which electrodeposition is performed with the current value increasing as it progresses in the transport direction, that is, the current value at the bath entry section is decreased.

According to this electrodeposition coating method, it is possible to obtain an electrodeposition coating film with a better appearance without hash marks, but in this method, the change in the current transport direction is This is generated by changing the distance from the object to be coated or the voltage value applied between this electrode and the object to be coated in the transport direction, so when changing the size of the electrode, it is necessary to use electrodes of various sizes. or prepare
Alternatively, a specially shaped electrode must be prepared, and if the distance between the electrode and the object to be coated is changed, the distance from the electrode to the object must be increased on the tank side. ,
In other words, the electrodes have to be arranged diagonally, which requires a large space, which makes the electrodeposition tank quite large.Furthermore, when changing the voltage value applied between the electrode and the object to be coated, it is necessary to There are so many drawbacks that it requires a device to change the voltage applied to the electrodes.

On the other hand, as the coating progresses on the object to be coated in the electrodeposition tank, the paint components in the paint adhere to the object, so the concentration of the neutralizing agent in the paint increases, and therefore the coulombic efficiency of the paint increases. decreases,
As a result, a situation occurs in which the film thickness of the coating film decreases. For this reason, in order to maintain a constant concentration of the neutralizing agent in the paint, a diaphragm chamber is currently installed in the electrodeposition tank along the conveyance path of the object to be coated. Electrodeposition coating equipment of a type that maintains a constant concentration of neutralizing agent in the paint by removing an amount of neutralizing agent commensurate with the film-forming components in the membrane chamber is increasingly used. In this type of electrodeposition coating apparatus, a paint whose neutralizing agent concentration is the same as that of the paint in the tank can be used as a replenishing paint, and the electrodeposition tank can be easily managed. In this type of electrodeposition coating equipment equipped with a diaphragm chamber, the diaphragm chamber (electrode plate) is not installed near the tank entry area in order to prevent the occurrence of hash marks. Since the coating is not applied effectively to the object to be coated, the electrodeposition tank becomes longer, requiring a predetermined number of diaphragm chambers to be shifted toward the exit tank side in order to obtain the desired coating film. There is.

The present invention provides an electrodeposition coating apparatus of the type equipped with the above-mentioned diaphragm chamber, which is free from the above-mentioned drawbacks and has a conventional structure that prevents the formation of scratch marks on the surface of the coating film formed. The purpose is to provide

The present invention provides a plurality of diaphragm chambers along the conveyance path of the object to be coated in an electrodeposition tank filled with an electrodeposition paint, and arranges an electrode plate in each of the diaphragm chambers. In an electrocoating device that performs painting by electrodepositing the electrodeposition paint onto the surface of the object by applying a DC voltage between the object and the object immersed in the coating material using an energizing tank method. In order to circulately supply diaphragm water having a lower conductivity than the diaphragm water supplied to the other diaphragm chambers to the diaphragm chamber on the entrance side of the electrodeposition tank, a cooler is provided to cool the diaphragm water. It is characterized by being equipped with a diaphragm water circulation circuit.

That is, in the electrodeposition coating apparatus of the present invention, the diaphragm water circulation circuit equipped with the above-mentioned cooler allows the diaphragm chambers in the electrodeposition tank to be controlled among the plurality of diaphragm chambers arranged in the electrodeposition tank along the conveying direction of the object to be coated. By cooling the diaphragm water in the diaphragm chamber on the entry tank side, the conductive dust is lowered compared to the conductive dust in the diaphragm water in other diaphragm chambers, and in the entry tank, it flows between the object to be coated and the electrode. By lowering the current, this prevents a large amount of current from flowing when the object to be coated enters the bath, thereby preventing scratch marks from forming on the painted surface. Thus, according to the present invention,
It has a simple structure that only lowers the diaphragm torpedo conductivity in the diaphragm chamber on the tank entry side compared to other diaphragms, and does not require any extra spacing, and effectively creates hash marks on the coating surface. In addition, it is possible to effectively form a coating immediately after entering the electrodeposition tank without increasing the length of the electrodeposition tank.

Next, an electrodeposition coating apparatus according to a preferred embodiment of the present invention will be described.

The present invention can be applied to both anionic electrodeposition coating and cationic electrodeposition coating methods.
The figure shows a cationic electrodeposition coating device.

The cationic electrodeposition coating apparatus shown in FIG.
Inside this electrodeposition tank 1, a diaphragm device 2 is arranged along both side walls 1a. This diaphragm device 2 has a plurality of diaphragm chambers 3, and inside each of the diaphragm chambers 3, electrode plates 4 connected to the anode side of a DC power source V are arranged. The cathode side of the DC power supply V is immersed in the coating liquid 5 in the electrodeposition tank 1 and connected to the object 6 to be coated, which is conveyed by the conveyor C shown in FIG. 2 along the diaphragm device 2. has been done. The electrode plate 4 and the object to be coated 6 are energized by a so-called energization bath method in which the electrode plate 4 and the object to be coated 6 are energized before the object to be coated 6 is immersed in the electrodeposition tank 1. The anion type electrodeposition coating apparatus has the same structure as the cation type electrodeposition coating apparatus shown in FIG. 1, but the electrode plate 4 in the diaphragm chamber 3 is connected to the anode of the DC power source (■). , - A stress relief coating 6 is connected to the cathode of the DC power supply V. Diaphragm water is supplied into the diaphragm chamber 3 from a supply pipe 7 extending from above the diaphragm chamber to near the bottom,
The liquid is discharged to the outside of the electrodeposition tank 1 through a discharge pipe 8 extending outward from the upper side of the diaphragm chamber and penetrating the side wall of the electrodeposition tank 1 .

The plurality of diaphragm chambers 3 arranged along the side wall of the electrodeposition bath 1 are divided into an entrance side diaphragm chamber 3a and a remaining diaphragm chamber 3b, as shown in FIG. contains conductive dust ('100-!;00μ0) used in ordinary electrodeposition coating.
/σ), the diaphragm chamber 3a contains conductive dust (SO~100μ0/σ) which has a lower value than the conductive dust of the diaphragm water in the diaphragm chamber 3b.
σ) The diaphragm is filled with water. A first diaphragm water circulation circuit 9 that circulates and supplies diaphragm water with low conductivity dust to the diaphragm 43a is connected to the diaphragm chamber 38 on the tank entry side, and the remaining diaphragm chamber 3b is connected to the diaphragm chamber 3b. A diaphragm water circulation circuit 10 for circulating and supplying the above-mentioned normal conductive dust diaphragm water is connected to the diaphragm water circulation circuit 10.

As shown in FIG. 3, the electrical conductivity-temperature characteristic of diaphragm water is approximately proportional, and by utilizing this, the first diaphragm water circulation circuit 9 has a diaphragm water flowing through the circuit 9. A cooler CO is provided to cool the water and reduce its conductive dust to the predetermined low conductive dust level. Characteristic line a + shown in Figure 3
b is the standard temperature (, zO'c) / θμU/cm,
It shows the change in conductive dust when the temperature of diaphragm water with conductive dust of 100 μU/cm is changed. conductive dust ti-oo~SOOμU/c
The diaphragm water of m is of characteristic line. This has the advantage that the temperature of each diaphragm water can be lowered.

However, it is not necessary to use diaphragm water having different characteristic lines a and b, and only diaphragm water exhibiting characteristic line a may be used.

The first and first diaphragm water circulation circuits 9 and 10 include:
First and second diaphragm water storage tanks 11 and 12 are provided, respectively, and diaphragm water discharged from the diaphragm chambers 3a and 3b is stored in these first and second diaphragm water storage tanks 11 and 12, respectively. It has become. Therefore, the conductive dust of the diaphragm water in the first diaphragm water storage tank 11 is the conductive dust of the diaphragm water in the diaphragm chamber 3a, and the conductive dust of the diaphragm water in the first diaphragm water storage tank 11 is the conductive dust of the diaphragm water in the diaphragm chamber 3b. Each is the same as dust.

As the coating of the object 6 in the electrodeposition bath 1 progresses, the diaphragm chamber 3
A neutralizing agent is absorbed into the coating liquid 5 in an amount corresponding to the solid coating component electrodeposited on the object 6 to be coated. Diaphragm chamber 3
Conductive dust rises in the diaphragm water by the amount of neutralizing agent absorbed. Therefore, the first and first diaphragm water storage tanks 11 and 12 are each provided with conductivity adjusting devices 13 and 14 for keeping the conductive dust in the diaphragm water within a predetermined range. This conductivity adjustment device 13.14 controls pure water into the diaphragm water storage tank 11.
, 12 are provided with pure water supply pipes 15 and 16. The pure water supply pipes 15 and 16 are provided with automatic on-off valves 17 and 18.
The opening and closing of 18 is controlled by valve drive devices 19 and 20. This valve drive device 19.20 detects conductive dust in the diaphragm water in the first and second diaphragm water storage tanks 11.12, and outputs a signal S when the conductive dust in the diaphragm water becomes higher than the value in the predetermined range. Output conductivity detection device 21.2
Connected to 2. When the valve drive device 19.20 receives the signal S from the conductivity detection device 21.22, it opens the on-off valves 17 and 18 and supplies pure water to the diaphragm water storage tank 11.
．． 12 to keep the conductive dust in the diaphragm water in the diaphragm water storage tank 11.12 at a predetermined value.

A pump P is interposed in the pipeline on the supply side of the first and second diaphragm water circulation circuits 9,100.
The diaphragm water in which conductive dust is kept constant is stored in the diaphragm water storage tank 1],
, 12 to the diaphragm chamber 3.

Therefore, the electrically conductive dust in the diaphragm water in the diaphragm chamber 3b is kept at normal electrically conductive dust within the above-mentioned predetermined range, and the electrically conductive dust in the diaphragm water in the diaphragm chamber 3a is kept at a lower electrical conductivity in the predetermined range than the above-mentioned normal electrically conductive dust. kept in dust.

In addition, in order to raise the electrically conductive dust in the diaphragm water in the plurality of diaphragm chambers 3 in stages from the tank entry side, the diaphragm chamber 3b near the diaphragm chamber 3a on the entry tank side is also shown by imaginary lines in Figure 1. The first diaphragm water circulation circuit 9 is extended as shown in FIG.
The conductive dust of this internal diaphragm water is removed from the first and second storage tanks 11.
It may also be conductive dust between the conductive dust of the diaphragm water in 12 and 12.

Using the cationic electrodeposition coating device with the structure explained above,
An example of the present invention in which electrodeposition coating was performed under the following electrodeposition conditions, and a comparative example in which electrodeposition coating was performed under the electrodeposition conditions described below using a cationic electrodeposition coating apparatus in the same manner. is shown in FIG. Figure 2 shows the relationship between the elapsed time and the change in the current flowing between the object to be coated and the electrode plate when the object to be coated is immersed in the electrodeposition bath while being conveyed.

(1) Electrodeposition conditions of the example Electrodeposition tank: length 3, t, -, width 2.3 m, depth x m Diaphragm chamber: height 2 m + thickness o, im, width/771 (in addition, the (The height of the first diaphragm chamber from the tank side is 7.5 m) Number of 77 pieces arranged on one side Object to be coated: Automobile body Total surface area Paint: o'ro-tr-octopus (Nippon Paint) (manufactured by) conductive dust
1eooμU/c1rL Temperature: 27°C Concentration: 27% Coulombic efficiency: 33■/C Applied voltage: 33θV (cation type) Conductive dust in diaphragm water in the diaphragm chamber on the entry side /θ0pU76
rnConductive dust in diaphragm water in other diaphragm chambers poθ~500μ
TJ/cm Total immersion time of the object to be coated in the electrodeposition bath
2) Electrodeposition conditions for Comparative Example The electrically conductive dust in all the membrane chambers of the above example was 900~! 00μ
U/cIrL.

Other electrodeposition conditions were the same as in the above example.

(3) Electrodeposition conditions for Comparative Example 3 The diaphragm chambers on both sides of the electrodeposition tank are removed, and the remaining diaphragm chambers (one on each side) are cleaned of conductive dust of 100~
It was called gooμC gallery.

Other electrodeposition conditions were the same as in the above example.

As shown in FIG. 1, in Comparative Example/, a large current flowed when the object to be coated was placed in the tank, resulting in scratch marks. In Comparative Example 4, no scratch marks were generated when the object was placed in the bath, but since the current that flows when the object to be coated is placed in the bath is extremely small, it is difficult to form a coating film effectively when the object is placed in the bath. In order to obtain a film, a predetermined number of diaphragm chambers must be shifted toward the outlet tank side, resulting in a problem that the electrodeposition tank becomes long.

On the other hand, in the example of the present invention, when the object to be coated, which is a car body, was electro-deposited, a good painted surface without hash marks could be obtained without a large current flowing when entering the bath.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a cationic electrodeposition coating apparatus to which the present invention can be applied, FIG. 2 is a schematic diagram showing an electrodeposition coating apparatus according to an embodiment of the present invention, and FIG. 3 is a diaphragm. Graph showing conductive dust temperature characteristics of water, No. 9
The figure shows the relationship between the elapsed time and the change in the current flowing between the object to be coated and the electrode plate when the object to be coated is immersed in the electrodeposition tank under the electrodeposition conditions of the example of the present invention and the comparative example. This is the graph shown. 1・・・・・・・・・Electrodeposition bath, 3・・・・・・・・・
Diaphragm chamber, 3a... Diaphragm chamber on the tank entry side, 3
b・・・・・・Other diaphragm chambers, 9・・・・・・・・・
...First diaphragm water circulation circuit, 10...1st
Diaphragm water circulation circuit, 11...7th
Diaphragm water storage tank, 12...Second diaphragm water storage tank, Co...Cooler patent applicant Toyo Kogyo Co., Ltd. Figure 1 Figure 3 Separation 1 [Water 1 Cooling (°C) Figure 4 Special Procedures Amendment Book 5712, -2 Date of 1939 Director-General of the Patent Office Kazuo Wakasugi 1, Indication of Case Patent Application No. 1♂2121 of 1982 2
, Title of the invention Electrodeposition coating device 3, Relationship with the case to be amended Applicant name (313) Toyo Kogyo Co., Ltd. 4, Agent 5, Date of amendment order Initiator 6. 8, Description of contents of amendment , correct the errors in the following places.

Claims (1)

[Claims] A plurality of diaphragm chambers are provided along the conveyance path of the object to be coated in an electrodeposition bath filled with electrocoating paint, and an electrode plate is arranged in each of the diaphragm chambers, and between this electrode plate and the electrocoating paint, In an electrodeposition coating apparatus that performs painting by electrodepositing the electrodeposition paint on the surface of the object to be coated by applying a DC voltage between the object to be coated and the object being immersed in an energized tank, A diaphragm water circulation system equipped with a cooler to cool the diaphragm water in order to circulately supply diaphragm water whose conductivity is lower than the conductivity of the diaphragm water supplied to other diaphragm chambers to the diaphragm chamber on the entry side of the tank. An electrodeposition coating device characterized by being equipped with a circuit.