JPS5980796A - Electrodeposition painting device - Google Patents

Abstract

PURPOSE:To form easily a paint coated film having different thickness at upper and lower side by providing plural diaphragm chambers which are divided to upper and lower chambers in an electrodeposition cell, transferring a part of the diaphragm water in the upper diaphragm chambers into the lower diaphragm chambers and making the conductivity of the diaphragm water smaller on the upper side than on the lower side. CONSTITUTION:Plural pairs of diaphragm chambers each consisting of an upper diaphragm chamber 7 and a lower diaphragm chamber 8 are juxtaposed on both sides in an electrodeposition cell 2, and diaphragms 7a, 8a and plates 9, 10 are provided in the upper and lower chambers 7, 8. The upper chamber 7 is connected through a supply pipe 12 to a regulation tank 13, and is further connected through a conduit 14 for circulation to the tank 13. The conductivity of the diaphragm water in the tank 13 is measured with a sensor 15 and pure water is supplied by a flow rate control valve 16 to the tank 13 to regulate the conductivity of the diaphragm water to about 50- 100muOMEGA/cm. Said diaphragm water is supplied by a pump 11 into the chamber 7. Part of the diaphragm water discharged from the chamber 7 is introduced through a three-way valve 18 provided to the conduit 14 into the chamber 8, and regulate the conductivity of the diaphragm water therein to 150-300muOMEGA/cm. The thickness of the paint coated film is thus made thin on the upper side and thick on the lower side.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrodeposition coating apparatus, in particular, a method in which an electrode is arranged in a diaphragm chamber provided in an electrodeposition tank, and a voltage is applied between the electrode and the object to be coated to coat the object. This invention relates to a diaphragm-type electrodeposition coating device that is adapted to adhere to objects.

An electrodeposition tank is filled with a liquid containing a water-dispersible or water-soluble electrodeposition paint, an electrode is provided in the tank, and a DC voltage is applied between the electrode and the object to be coated immersed in the tank. Electrodeposition coating, in which paint is applied electrostatically to the object to be coated, is widely used for painting automobile bodies and the like. Incidentally, since the lower part of an automobile body is subject to more severe corrosion conditions than the upper part, the paint film must be thicker at the lower part than at the upper part. Conventionally, in order to achieve this objective in electrodeposition coating, Japanese Patent Application Laid-open No. 127946/1987 discloses that an insulating shielding plate is provided along the inner wall surface of the electrodeposition tank, and the gap between this shielding plate and the object to be coated is By arranging an electrode plate that can apply a voltage weaker than that of the electrodeposition bath, it is possible to form a thin coating film on the part of the surface of the object to be coated that corresponds to the shielding plate, and a thick coating film on other parts. A device has been proposed. Also, JP-A-52-12794
No. 8 states that in electrodeposition painting of automobile bodies, the lower part of the car body is first immersed in a high-voltage electrodeposition bath, and then the entire body is immersed in a low-voltage electrodeposition bath, so that the lower part is thicker. , a method has been proposed in which a thin coating film is formed on the top.

In such conventional electrodeposition coating, the electrode is inserted bare into the electrodeposition liquid in the electrodeposition tank, or the electrodeposition tank itself constitutes the electrode, and as the coating progresses, the electrode is inserted into the electrodeposition solution. As a result, the paint components in the electrodeposition solution adhere to the object to be coated, and the concentration of the neutralizing agent becomes correspondingly high, resulting in a tendency for the thickness of the coating film to become thinner. In order to solve this problem, a diaphragm chamber surrounded by a permeable diaphragm is provided in the electrodeposition bath, and an electrode is placed inside this diaphragm chamber. A diaphragm-type electrodeposition coating in which an amount of neutralizing agent is transferred to the diaphragm chamber, and the concentration of the neutralizing agent in the electrodeposition solution is appropriately controlled relative to the concentration of the paint, has come into use. .

However, the apparatus proposed in JP-A-52-127946 mentioned above cannot be said to be suitable for such diaphragm-type electrodeposition coating, and cannot be expected to produce fully satisfactory results. Furthermore, the method proposed in JP-A-52-127948 requires two steps to form coating films of different thicknesses, and is not satisfactory in terms of equipment and processing time. do not have.

The present invention was achieved by focusing on the above-mentioned problems of conventional electrodeposition coating, and provides a diaphragm-type electrodeposition coating device that can form coating films with different thicknesses on the upper and lower sides using a simple device. The purpose is to

That is, in the present invention, an electrode is arranged in a diaphragm chamber in an electrodeposition tank, and a DC voltage is applied between the electrode and a workpiece immersed in the electrodeposition tank, thereby applying paint to the surface of the workpiece. In electrocoating equipment that uses electrodeposition to paint objects, the diaphragm chamber is divided into upper and lower halves, and an electrode is placed in each diaphragm chamber, and the diaphragm water in the upper diaphragm chamber is drained. By moving the diaphragm to the side diaphragm, the conductive dust in the diaphragm water in the upper diaphragm is made smaller than that in the diaphragm water in the lower diaphragm. According to this configuration of the present invention, since the electrically conductive dust in the diaphragm water in the lower diaphragm chamber is larger than that in the upper diaphragm chamber, the current density in the lower part of the object to be coated is higher than in the upper part. The membrane becomes thicker at the top. To transfer diaphragm water from the upper diaphragm chamber to the lower diaphragm chamber, a three-way valve is installed in the circulation path that takes the diaphragm water from the upper diaphragm chamber, adjusts the neutralizing agent concentration, and returns it to this diaphragm chamber. In this case, it is easy to adjust the conductive dust in the diaphragm water in the lower diaphragm chamber, and to control the conductive dust in the diaphragm water in the adjustment tank. Adjustment is also easy. When the conductive dust is supplied to the upper diaphragm chamber, it is adjusted to about 50 to 100 μm/f in a regulating tank, and the upper diaphragm is adjusted to a diaphragm torpedo conductivity of about 150 to 600 μ'117 cm in the lower diaphragm chamber. Preferably, the diaphragm water is circulated from the diaphragm chamber. If the conductive dust in the diaphragm water in the upper diaphragm chamber is less than 50μυ/cr11, the coating film formed will be too thin and will be 100μT.
J/cm or more is too thick and uneconomical. The conductive dust of the diaphragm water in the lower diaphragm chamber is 150 to 300 μσ to ensure the coating thickness required for the lower part of a normal automobile body.
/-.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, an electrodeposition tank 2 filled with an electrodeposition solution 1 containing a paint and a neutralizing agent has an object to be coated 3 and an outlet 4, and an object to be coated 5 is supplied to the electrode from the inlet 3 by a conveyor 6. The inside of the loading tank 2 is energized, and it is carried out from the outlet 4. In the electrodeposition tank 2, a plurality of pairs of diaphragm chambers, each pair being an upper diaphragm chamber 7 and a lower diaphragm chamber 8, are arranged in rows on both sides along the traveling direction of the object to be coated. Second
As shown in the figure, the upper diaphragm chamber 7 has a permeable diaphragm 7a on the wall surface on the side of the object to be coated 5, and an upper electrode plate 9 is arranged inside. Similarly, the lower diaphragm chamber 8 has a diaphragm 8a, and a lower electrode plate 10 is disposed therein. When the present invention is applied to anionic electrodeposition coating, the electrode plates 9 and 10 are connected to the negative side of the power source, and the object to be coated 5 is connected to the positive side. In the case of cationic electrocoating, the connection to the power source is the opposite. As is well known, the diaphragm 7a s 8a allows an amount of neutralizing agent corresponding to the amount of paint adhering to the car body to permeate into the diaphragm chamber 7.8 by ion exchange, and the amount of neutralizing agent in the electrodeposition tank 2 is increased. Keep the neutralizer concentration in the solution appropriate for the paint.

Referring again to FIG. 1, the upper diaphragm chamber 7 is connected to a regulating tank 13 by a supply pipe 12 having a pump 11, and the diaphragm water in which conductive dust has been adjusted in the regulating tank 13 is supplied to the supply pipe 12.
It is supplied to the upper diaphragm chamber 7 via. The upper diaphragm chamber 7 is further connected to the adjustment tank 13 by a diaphragm water circulation conduit 14, and the diaphragm water in which the neutralizing agent concentration is high in the upper diaphragm chamber 7 and the conductive dust is high as a result is transferred to the adjustment tank 13. be discharged. The adjustment tank 13 includes a water supply pipe 17 having a flow rate control valve 16 whose opening degree is adjusted by a signal from the conductive dust sensor 15.
is provided, and pure water is supplied from the water supply pipe 17 to the adjustment tank 13 to adjust the conductive dust in the diaphragm water in the adjustment tank 13 to a predetermined value, for example, exactly 50 to 1[]0μ.

The conduit 14 is provided with a three-way valve 18 via which it is connected to the lower diaphragm chamber 8 . The three-way valve 18 functions to introduce a predetermined amount of diaphragm water discharged from the upper diaphragm chamber 7 into the lower diaphragm chamber 8 . A diaphragm water discharge pipe 19 is provided in the lower diaphragm chamber 8 . The amount of diaphragm water guided from the upper diaphragm chamber 7 to the lower diaphragm chamber 8 is such that the conductive dust of the diaphragm water in the lower diaphragm chamber 8 is within a predetermined range, for example, 150 to 3
Adjust so that it is 00μU/α, and use the three-way valve 1 to adjust it.
Do it by 8.

In this way, since the conductive dust in the diaphragm water is higher in the lower diaphragm chamber 8 than in the upper diaphragm chamber 7, the diaphragm current is also higher in the lower diaphragm chamber 8, and as a result, it forms on the object to be coated. The coating film is thicker at the bottom. In the illustrated embodiment, a portion of the diaphragm water is transferred from the diaphragm water circulation circuit extending from the upper diaphragm chamber to the adjustment tank to the lower diaphragm chamber, but the total amount of diaphragm water taken out from the upper diaphragm chamber The diaphragm water may be introduced into the lower diaphragm chamber, and the diaphragm water taken out from the lower diaphragm chamber may be transferred to an adjustment tank or discarded.

Using the electrodeposition coating apparatus having the structure described above, stain coating was carried out under the following electrodeposition conditions.

Electrodeposition bath: length 350, width 2.5m% depth 2m Diaphragm chamber: height 0.8m on top, 1-2m on bottom 5m width 1m, thickness 0.1m
, Number of pieces (placed on one side) 14 each Object to be coated: Automobile body Total surface area 60m2 Paint: 0T
O-U-52 (manufactured by Nippon Paint Co., Ltd.) Conductive dust 1400 tiTJ/cm Temperature 27°C Concentration 21% Coulombic efficiency 33■/C Applied voltage: 330V (cation/type) Total charge of the object to be coated to the electrodeposition bath Immersion time: 2.5 minutes Total number of objects to be coated immersed in the electrodeposition tank Coatings when the conductive dust in the diaphragm water in the upper diaphragm chamber 7 and lower diaphragm chamber 8 is changed under the conditions of electrodeposition of 4 or more objects The total diaphragm current in the electrodeposition tank 2 flowing between the object 5 and the upper electrode plate 9 and the lower electrode plate lO changes as shown in FIG. changes as shown in FIG.

Under the above electrodeposition conditions, the conductive dust in the diaphragm water in the upper diaphragm chamber 7 was
0μU/-, 200μ of conductive dust in the diaphragm water in the lower diaphragm chamber 8
As for the coating thickness in the case of U/Crn, a coating thickness of about 15μ was obtained on the upper part of the object to be coated, and about 18μ on the lower part.

[Brief explanation of drawings]

Fig. 1 is a side view of an electrodeposition coating apparatus showing an embodiment of the present invention, Fig. 2 is a partial sectional view thereof, and Fig. 3 is a case where the conductive dust in the diaphragm water in the upper and lower diaphragm chambers is changed. FIG. 4 is a graph showing changes in the total diaphragm current flowing between the object to be coated and the upper and lower electrode plates, and FIG. 4 is a graph showing changes in coating film thickness with respect to the total diaphragm current. 2... Electrodeposition tank, 5... To be coated, 7... Upper diaphragm chamber, 8... Lower diaphragm chamber, 9, 10... Electrode plate, 17.
... Water supply pipe, 18... Three-way valve. Patent applicant: Toyo Kogyo Co., Ltd.

Claims (1)

[Claims] A diaphragm chamber is provided in an electrodeposition tank filled with an electrodeposition paint solution, an electrode plate is arranged in the diaphragm chamber, and a direct current is applied between the electrode plate and the object to be coated immersed in the electrodeposition tank. In an electrodeposition coating apparatus that coats an object by electrodepositing the paint onto the surface of the object by applying a voltage, the diaphragm chamber is divided into upper and lower parts, and each diaphragm chamber is provided with an electrode. A plate is arranged, and a circuit is provided to transfer at least a portion of the diaphragm water in the upper diaphragm chamber to the lower diaphragm chamber, such that conductive dust in the diaphragm water in the upper diaphragm chamber is transferred to the diaphragm water in the lower diaphragm chamber. An electrodeposition coating device configured to be smaller than conductive dust,