JPS5980797A - Electrodeposition painting device - Google Patents

Abstract

PURPOSE:To form a paint coated film having different thickness at upper and lower side with a simple device by juxtaposing plural diaphragm chambers which are divided to upper and lower chambers in an electrodeposition cell, and making the temp. of the diaphragm water in the upper diaphragm chambers lower than the temp. of the diaphragm water in the lower diaphragm chambers. 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 to the chambers 7, 8. The diaphragm water in the chamber 7 is transferred by a conduit 11 and a manihold pipe 12 into a regulation tank 13. Pure water is supplied into the tank 13 by a control valve 13 in accordance with the signal of a sensor 16 for the concn. of a neutralizing agent to regulate the concn. of the neutralizing agent. Such diaphragm water is fed by a pump 17 into a cooler 18a to control the conductivity to about 50- 100muOMEGA/cm, then the diaphragm water is supplied into the chamber 7. The diaphragm water in the chamber 8 is similarly transferred by pipes 19, 20 into a regulation tank 21, where the pure water is supplied by a sensor 22 and a control valve 23 to the diaphragm water to control the conductivity of the diaphragm water in the tank 21 to about 400-500muOMEGA/cm. The diaphragm water is then supplied by a pump 25 through a supply pipe 26 into the chamber 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrodeposition coating apparatus, in particular, an electrodeposition coating device, 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 apply the paint to the object. The present invention relates to a diaphragm type electrodeposition coating device that allows the coating to be applied to the surface of the membrane.

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 is a process in which the paint is applied electrostatically to the object being coated.
It is widely used for painting automobile bodies. by the way,
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 in the lower part than in 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 be applied a weaker voltage than the electrodeposition bath, it is possible to form a thin film on the part of the surface of the object to be coated that corresponds to the shielding plate, and a thick film on other parts. A device has been proposed. Also, JP-A-52-127
No. 948 describes that in electrodeposition painting of automobile bodies, the lower part of the car body is first immersed in a high-voltage electrodeposition tank, and then the entire car body is immersed in a low-voltage electrodeposition tank, so that the lower part is thicker and the upper part is thicker. A method of forming a thin coating film has been proposed.

In such conventional electrodeposition painting, 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 coating components in the electrodeposition solution adhere to the object to be coated, and the concentration of the neutralizing agent increases accordingly, causing 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 paint concentration, 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 give sufficiently satisfactory results. Furthermore, the method proposed in JP-A No. 52-127948 requires two steps in order to form coating films of different thicknesses, and is unsatisfactory in terms of equipment and processing time.

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 disposed in a diaphragm chamber in an electrodeposition tank, and a DC voltage is applied between the electrode and the workpiece immersed in the electrodeposition tank, so that the surface of the workpiece can be coated. In electrodeposition coating equipment, which is used to electrodeposit paint on objects to be coated, the diaphragm chamber is divided into upper and lower halves, and an electrode is arranged in each diaphragm chamber, and the diaphragm in the upper diaphragm chamber It is characterized in that means is provided for making the temperature of the water lower than the temperature of the diaphragm water in the lower diaphragm chamber. According to this configuration of the present invention,
Since the temperature of the diaphragm water in the lower diaphragm chamber is higher than that in the upper diaphragm chamber, the conductivity of the diaphragm water in the lower diaphragm chamber is higher than that in the upper diaphragm chamber, and as a result, the lower part of the workpiece is The current density is higher at the top, and the coating formed at the bottom is thicker than at the top. Temperature control is achieved by simply installing a cooler in the circulation path that takes the diaphragm water from the upper diaphragm chamber, adjusts the concentration of the neutralizing agent, and returns it to the diaphragm chamber. can produce satisfactory results. The temperature is such that the conductivity of the diaphragm water in the upper diaphragm chamber is about 50 to 100 μU/:cm, and the conductivity of the diaphragm water in the lower diaphragm chamber is 400 to 500 μU.
It is preferable to control it so that it is about /σ. If the electrical conductivity of the diaphragm water in the upper diaphragm chamber is less than 50 μfj/cm, the coating film formed is too thin and 100 μ77/cm
This is too thick and uneconomical. The electrical conductivity of the diaphragm water in the lower diaphragm chamber is required to be 400μU10n to ensure the minimum coating thickness required for the lower part of a normal automobile body, and if it exceeds 500μ75/lar, the coating becomes too thick. The surface becomes rough.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

In FIG. 1, an electrodeposition bath 2 filled with an electrodeposition solution 1 containing a paint and a neutralizing agent has an inlet 3 and an outlet 4 for the object to be coated, and the object 5 is conveyed to the inlet 3 by a conveyor 6. Electricity is passed through the electrodeposition tank 2 from the electrodeposition tank 2, and the electrodeposition tank 2 is discharged from the outlet 4. In the electrodeposition bath 2, a plurality of pairs of diaphragm chambers, including 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 diaphragms 7a and 8a allow 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 solution in the electrodeposition tank 2 is Maintain proper concentration of Japanese additive in paint.

Referring again to FIG. 1, the upper diaphragm chamber 7 is connected to the upper adjustment tank 13 through a conduit 11 and a collecting pipe 12, and the diaphragm water in the upper diaphragm chamber 7 is sent to the adjustment tank 13 through the pipes 11 and 12. be transferred. Pure water is supplied to the adjustment tank 13 from a water supply pipe 15 having a flow rate control valve 14.
4 has its opening degree controlled by a signal from a neutralizer concentration sensor 16 provided in the adjustment tank 13, and adjusts the neutralizer concentration of the diaphragm water in the adjustment tank 13 to a predetermined range. The adjustment tank 13 is further connected to the upper diaphragm chamber 7 through a supply pipe 18 having a pump 17, and the diaphragm water whose neutralizing agent concentration has been adjusted as described above is sent to each chamber via the pipe 18 by the pump 17. The upper diaphragm chamber 7 is supplied. A cooler 18a is provided in the middle of the supply pipe 18, and the diaphragm water is cooled by the cooler 18a and supplied to the upper diaphragm chamber 7. The conductivity of the diaphragm water decreases due to cooling;
This is done so that the thickness is ~100μ in y/cm. This diaphragm water circulation circuit maintains the electrical conductivity of the diaphragm water in the upper diaphragm chamber 7 at a predetermined value.

Similarly, the lower diaphragm chamber 8 is connected to a lower adjustment tank 21 through a conduit 19 and a collecting pipe 20, and the opening degree of the adjustment tank 21 is controlled by signals from neutralizer concentration sensors 2, 2. A water supply pipe 24 having a flow control valve 23 is provided. The neutralizing agent concentration in the diaphragm water in the adjustment tank 21 has an electrical conductivity of 400 to 50.
It is adjusted to be 0 μU/crn. The adjustment tank 21 is connected to the lower diaphragm chamber 8 by a supply pipe 26 having an Imp 25, and the lower diaphragm chamber 8 is supplied with diaphragm water whose conductivity has been adjusted in the adjustment tank 21.

In this way, since the electrical conductivity of 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, the electrical conductivity of the diaphragm water is higher in the lower diaphragm chamber 8. The coating is thicker at the bottom.

The relationship between the temperature of the diaphragm water and the electrical conductivity is approximately proportional as shown in FIG. 3, and as the temperature of the diaphragm water is lowered, the electrical conductivity also decreases. The characteristic line asb shown in Fig. 3 is 160 ttU/c at the base parrot temperature (20°C).
m, 4 [] It shows the change in conductivity when the temperature of the diaphragm water was changed with the concentration of the neutralizing agent changed so as to have the conductivity of OaU/cm, and the electrodeposition conditions described below were used. In the example in which electrodeposition coating was performed with
) is the characteristic line a, and the diaphragm water in the lower diaphragm chamber 8 (
Conductivity: 400μ'L)/crn1500baT/Crn
) uses characteristic lines. 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 as and b, and only diaphragm water exhibiting characteristic line a may be used.

Electrodeposition coating was carried out under the following electrodeposition conditions using the electrodeposition coating apparatus having the structure described above.

Electrodeposition tank: length 35m, width 2.5m, depth 2m Object to be coated: Automobile body Total surface area 60m2 Paint: oTo
-U-52 (manufactured by India Ltd. in Japan) Conductivity 1400μ
υ/cm Temperature 27℃ Concentration 21 Coulombic efficiency 33■/C Applied voltage: 330v (cation type) Total immersion time of the object to be coated in the electrodeposition bath 2.5 minutes Between the object to be coated 5 and the upper electrode plate 9 and lower electrode plate 10 when the electrical conductivity of the diaphragm water in the upper diaphragm chamber 7 and the lower diaphragm chamber 8 is changed under the condition of 4 or more electrodepositions. The total diaphragm current flowing in the electrodeposition tank 2 changes as shown in FIG. 4, and the thickness of the coating film changes as shown in FIG. 5 in response to the change in the total diaphragm current.

Under the above electrodeposition conditions, the conductivity of the diaphragm water in the upper diaphragm chamber 7 was 50.
ttTJ/cm (temperature of diaphragm water: approximately 5°C, characteristic line a shown in Figure 3) and 100 μU/Cm (temperature of diaphragm water: approximately 10°C, characteristic line a shown in Figure 3), lower diaphragm chamber The electrical conductivity of the diaphragm water of No. 8 is 400 μT) 7 cm (temperature of the diaphragm water: approximately 20°C, characteristic line b shown in Figure 3) and 500 μt.
When S/α (temperature of diaphragm water: about 40°C, characteristic line b shown in Figure 6), the thickness is about 15μ and about 15μ at the upper part of the object to be coated, and about 23μ and about 26μ at the lower part. The coating thickness was obtained.

[Brief explanation of the drawing]

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, FIG. 6 is a graph showing the relationship between the temperature of diaphragm water and conductive dust, and FIG. The figure is a graph showing the change in the total diaphragm current flowing between the object to be coated and the upper and lower electrode plates when the conductive dust in the diaphragm water in the upper and lower diaphragm chambers is changed. Figure 5 is the total diaphragm current. It is a graph showing the change in coating film thickness with respect to. 2... Electrodeposition tank, 5... To be coated, 7... Upper diaphragm chamber, 8... Lower diaphragm chamber, 9, 1O... Electrode plate, i5.
24... Water supply pipe, 18a... Cooler patent applicant Toyo Kogyo Co., Ltd. Figure 3 S blowing throat i/l 1 (=>) 3 heat (0C) Figure 4 Tokiyamaru-Kth electric knee % L (3J5/cm) Fig. 5 1 Kuma Atsushi':! (,p)

Claims (1)

[Claims] A diaphragm chamber is provided in the electrodeposition tank filled with electrodeposition paint liquid.
An electrode plate is arranged in the diaphragm chamber, and a DC voltage is applied between the electrode plate and the object to be coated immersed in the electrodeposition tank to electrodeposit the paint on the surface of the object to be coated. In electrodeposition coating equipment that has come to be used for coating various objects, the diaphragm chamber is divided into upper and lower halves, and an electrode plate is placed in each diaphragm chamber to lower the temperature of the diaphragm water in the upper diaphragm chamber. An electrodeposition coating apparatus characterized by being provided with means for lowering the temperature of the diaphragm water in the side diaphragm chamber.