JPH0280596A - Method and apparatus for coating shade-shaped article by electrodeposition - Google Patents

Abstract

PURPOSE:To form a uniform, smooth coating film having superior weather resistance and fine luster on a shade-shaped article by electrodeposition by immersing the body to be coated in a coating liq. for coating by electrodeposition in a vessel composed of an inner tube for electrifying the coating liq. and an outer tube and by impressing voltage between a counter electrode in the vessel and the body to be coated. CONSTITUTION:When a shade-shaped article is coated with a coating liq. based on acrylic resin and melamine resin by electrodeposition, a vessel for coating by electrodeposition having a double-tubed structure is composed of an inner tube 2 for electrifying the coating liq. and an outer tube 1, the coating liq. is filled into the vessel and the body 8 to be coated is put in the inner tube 2. A counter electrode 4 is set in the coating liq. at the inside of the inner tube 2 or between the inner and outer tubes 2, 1 and voltage is impressed between the body 7 to be coated and the counter electrode 4 to form a coating film on the body 8. A uniform, smooth coating film having superior weather resistance and fine luster can be formed on the shade-shaped article by electrodeposition.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming an electrodeposited coating film on a cap-shaped or bowl-shaped article such as a hemispherical, cylindrical, conical, or hat-shaped article, and a method thereof. The present invention relates to an electrocoating device for carrying out the method.

(Prior art) For articles with uneven parts, such as reflectors of lighting equipment such as large mercury lamps, light parts of automobiles, and parabolic antennas,
Electrodeposition coating is often used. In terms of functionality, the coating of these items places more emphasis on concave areas (inner surfaces) than convex areas, and requires not only the finished appearance but also a fairly high level of weather resistance, chemical resistance, scratch resistance, etc. Performance was required.

(Problem to be Solved by the Invention) Electrodeposition coating is applied to the above-mentioned shade-shaped article using the method and apparatus that have conventionally applied electrodeposition coating to building materials, etc. (see, for example, Japanese Utility Model Publication No. 47-38587). In this case, the paint coverage was poor and it was completely impossible to satisfy the above-mentioned performance requirements for the article.

It is desired that a uniform and smooth coating film be formed on the above-mentioned hat-shaped articles, especially on the concave side, but even if electrodeposition is applied using conventional coating methods and coating equipment, bubbles, unevenness, sagging, etc. will occur. It was not possible to suppress defects in the appearance of the paint film, and the gloss and reflectance of the paint film were poor.

It is an object of the present invention to provide a method and apparatus for electrodeposition coating, particularly for a shade-shaped article, which eliminates the drawbacks of the prior art described above.

Note that the present invention is not limited to the shape of the object to be coated as described above, and can be applied to articles of other shapes as well.

(Means for Solving the Problems) In order to achieve the above object, the present invention uses an electrodeposition coating liquid containing acrylic and melamine resin as main components for forming a coating film,
An electrodeposition coating tank having a double-tube structure consisting of an inner cylinder and an outer cylinder, which are designed to electrically conduct the coating liquid in contact with the inner and outer walls, is filled with the electrodeposition coating liquid, and the inside of the inner cylinder is coated. A coating film is deposited and formed on the object by dipping the object to be coated, providing a counter electrode between the inner and outer cylinders, or inside the inner cylinder, and applying a voltage between the object and the counter electrode. It is.

(Function) When electrodeposition coating was performed on a cap-shaped article according to the present invention configured as described above, the paint coverage was excellent and uniform, especially on the concave side of a large object. A smooth coating film was formed and the benefits of electrodeposition coating could be utilized to the fullest.

(Example) An example will be explained with reference to the drawings.
Figures 3(a) and 3(b) show the main structure of the electrodeposition coating apparatus of the present invention. A counter electrode 4 for the object to be coated is provided between the outer cylinder 1 and the inner cylinder 2. The inner cylinder 2 is provided with a through hole 3 for electrically conducting the electrodeposition coating liquid on both sides thereof and for the coating liquid to flow therethrough. A through hole 5 is also provided on the counter electrode 4 at a portion corresponding to the through hole 3 to allow the coating liquid to flow therethrough. In the upper part between the inner and outer cylinders, a coating liquid inflow pipe 6 to the electrodeposition coating tank is arranged around the entire circumference of the tank. On the other hand, at the inner lower part of the inner cylinder, a coating liquid outflow pipe 7 is arranged concentrically with the inner cylinder. At the bottom of the inflow pipe 6 and outflow pipe 7, there are holes 6', 6'', 6'' through which the paint liquid enters and exits.
..., 7', 7.7'', etc. are provided at appropriate intervals.

FIGS. 4 and 5 (a) show a plan view of a typical object to be coated 8, and FIG. 5 (b) shows a side sectional view. The object to be painted 8 is supported in the coating liquid by a hanger 9 that is normally equipped with a lead wire 10 and serves as a current-carrying contact.

FIG. 6 shows the implementation status of electrodeposition coating. The coating liquid fed into the electrodeposition coating tank from the coating liquid inlet pipe 6 passes through the counter electrode 4 and the through holes 3 and 5 of the inner cylinder 2, and fills the tank. The coating liquid outflow pipe 7 with ffi and Q girders in the lower part of the inner cylinder 2 has holes 7', 7n, 7n, etc. in its lower part, so the coating liquid sucked into the holes can cause the coating liquid to flow through the object 8. Circulating flow occurs around the inside as shown by the arrow. In this state, the object to be coated 8 is suspended inside the inner cylinder of the electrodeposition coating tank by the hanger 9, the lead wire 10 is connected to the positive electrode, and the counter electrode 5 is connected to the electrode 5.
Connect to the negative pole and apply voltage. The circulating flow of the coating liquid generated by the above-mentioned outflow pipe 7 serves to compensate for non-uniformity of coating components caused by electrodeposition coating and to form a uniform coating film.

The electrocoating tank (inner and outer cylinders and bottom) can be made of stainless steel, polypropylene, hard vinyl chloride, unsaturated polyester, or the like.

As the counter electrode, metals with excellent corrosion resistance such as stainless steel and titanium are suitable. If the tank is made of stainless steel, the tank wall can also be used as a counter electrode. Also,
Although the cross-sectional shape of the tank is not limited to any of circular, elliptical, and square shapes, it is ideal to have a cross-sectional shape similar to the cross-section of the object 8 to be coated in order to form a uniform coating film.

In electrodeposition coating, it is usually preferable to stop the circulation of the coating liquid during coating or to carry out circulation in a very small amount. This is to prevent the formed coating film from peeling off or deteriorating its appearance due to the flow of the coating liquid. However, in the present invention, although the coating liquid is circulated if necessary, the flow of the coating liquid in the electrodeposition coating tank is such that the coating liquid is sucked in from the bottom of the outflow pipe provided inside the inner cylinder 2. It is preferable to flow in from the inflow pipe 6 located above the space between the inner and outer cylinders. At this time, there is no need to limit the flow rate or flow rate within the pipe. Moreover, if a heat exchanger, filter, etc. for controlling the temperature of the paint liquid is provided in the middle of the circulation path, even better effects can be achieved.

A specific operation example of the present invention is as follows.

Example 1 (Preparation of electrodeposition coating solution used in Example 1) Into a 11-four-bottom flask equipped with a thermometer, a stirrer, and a reflux condenser, ethylene (nocol monobutyl ether 2509, tert-butyl peroxy-2- Charge 7.57 g of ethylhexanoate and raise the temperature to 80°C.To this, 131 g of methyl methacrylate and 9 g of n-butyl methacrylate.
A monomer mixture of 0 g, 410 g of ethyl acrylate, 14 g of acrylic acid, 80 g of 2-hydroxyethyl methacrylate, 75 g of N-cyclohexylmaleimide, and 1 g of 2,4-diphenyl-4-methyl-1-pentene was mixed with 2
Shun, Zaraani 24 dripped into the flask over 40 minutes
Stir for 0 minutes. Next, 30 g of ethylene glycol monobutyl ether, tertiary butyl peroxy
2-Ethylhexanoate 1.5 g of the mixture is added three times every 60 minutes. Thereafter, the mixture was stirred at 80° C. for 240 minutes to prepare an anionic acrylic resin.

Next, put 120g of this anionic acrylic resin in a container.
Melamine resin (trade name: Cymel HM-6, manufactured by Mitsui Cyanamid Co., Ltd.> 309) was collected and thoroughly stirred, and 1-noethylamine was added to the colander and thoroughly stirred.

Then, ion-exchanged water was gradually added while stirring to prepare an electrodeposition coating solution having a resin solid content of about 10% by weight.

Inner cylinder diameter 500m, outer cylinder diameter 600#, depth 5 as shown in Figure 1
Using an acrylic electrodeposition coating tank with a double cylinder structure of 80M,
An aluminum object having the shape shown in FIG. 5 was electrodeposited. A hard vinyl chloride coating liquid outflow pipe is installed in a circular manner along the top and center of the outer wall of the inner cylinder, and a hard vinyl chloride paint liquid outflow pipe is also installed in a circular manner at the bottom of the inner cylinder. Six holes with a diameter of 80 m are provided at equal intervals on the top, and the circulation of the coating liquid between the inner cylinder and the inner and outer cylinders is made 60 m in diameter.
This was done at a speed of 1/min.

Using the above electrodeposition coating liquid, 12 stainless steel plates (6
01MX500mInX0.5IIa> was connected to the cathode, and electrodeposition coating was performed.

For electrodeposition coating, the liquid temperature is 25℃, the applied voltage is 60V, and the energization time is 3.
A branch direct current was applied. The object to be coated was then taken out, thoroughly washed with tap water, and then baked and dried at 180° C. for 20 minutes. As a result, the coating film had no abnormalities such as pinholes, scratches, or bubbles, and a uniform and smooth coating film with a coating thickness of 12 to 13 μm was formed.

Example 2 Inner cylinder diameter 110 m, outer cylinder diameter 150 m, depth 1 as shown in Fig. 2
An aluminum object having the shape shown in FIG. 4 was electrocoated using a 40 m double-tube acrylic electrocoating tank.

Four holes with a diameter of 20 m are provided at equal intervals on the circumference of the inner cylinder at a distance of 40 m from the bottom surface, and hard vinyl chloride pipes are attached to the inner bottom of the inner cylinder and the upper part between the inner and outer cylinders. The coating liquid was circulated between the cylinders at a rate of 101/min.

The electrodeposition coating method uses a commercially available acrylic-melamine electrodeposition coating liquid (
Four stainless steel plates (30 x 10oxo, 2#l) were inserted at approximately equal intervals between the inner and outer cylinders, using the product to be coated as the anode (product name Honeybright C-1 manufactured by Honey Kasei Co., Ltd.).
was connected to the cathode, voltage was applied, and anion electrodeposition coating was performed.

Electrodeposition coating was carried out at a liquid temperature of 25° C., an applied voltage of 100 V, and a direct current flow for 3 minutes. Then, it was thoroughly washed with tap water and left at room temperature for 10 minutes. Thereafter, baking and drying were performed at 180° C. for 20 minutes.

The finished state of the coating was visually determined, and the coating film thickness was measured using a commercially available film thickness meter (trade name: Permascope Fisher Co., Ltd.). As a result, the coating film had no abnormalities such as pinholes, scratches, or bubbles, and a uniform and smooth electrodeposited coating film with a coating thickness of 9 to 10 μm was formed.

Example 3 Using an electrodeposition coating tank with the same shape as in Example 2 and an aluminum coating object with the same shape, a commercially available acrylic electrodeposition paint (trade name Nirecoat CM, manufactured by Shimizu Co., Ltd.) was used as the electrodeposition coating liquid. Then, cationic electrodeposition was performed by connecting the object to be coated as a cathode and the stainless steel plate provided between the inner and outer cylinders as an anode. Electrodeposition coating was performed under direct current conditions at a liquid temperature of 30° C., an applied voltage of 50 V, and a current application time of 3 minutes. Then, it was thoroughly washed with tap water and left at room temperature for 10 minutes. Thereafter, baking and drying were performed at 160° C. for 20 minutes under far infrared irradiation.

As a result, there were no abnormalities such as pinholes, scratches, or bubbles in the appearance of the coating, and a uniform and smooth electrodeposited coating with a coating thickness of 13 to 15 μm on the object to be coated was formed. Example 4 A stainless steel plate (SUS 30
4: Anionic electrodeposition coating was applied to the area of 300 x 400 x 2 m.

For electrodeposition coating, the liquid temperature is 25℃, the applied voltage is 50V, and the energization time is 3.
A branch direct current was applied. Then, after thoroughly washing with running water, baking and drying were performed at 150° C. for 20 minutes. As a result, the coating film had no abnormalities such as pinholes, scratches, or bubbles, and a uniform and smooth electrodeposited coating film with a coating thickness of 18 to 20 μm was formed.

Example 5 Using an electrodeposition coating tank with the same shape and the same electrodeposition coating solution as in Example 3, an iron plate (JISG 3141
:300X300X2m> was subjected to anion electrodeposition coating.

For electrodeposition coating, the liquid temperature is 25℃, the applied voltage is 50V, and the energization time is 3.
A branch direct current was applied. Then, it was washed thoroughly with tap water, baked at 150° C. for 20 minutes, and dried. As a result, the coating film had no abnormalities such as pinholes, scratches, or bubbles, and a uniform and smooth electrodeposited coating film with a coating thickness of 18 to 20 μm was formed.

Example 6 Using a stainless steel electrodeposition coating tank lined with epoxy resin and having a double hexagonal cylindrical structure shown in FIG.
Electrodeposition coating was performed on an aluminum object having the shape shown in the figure.

Attach a circular hard vinyl chloride coating liquid outflow pipe to the top and center of the outer wall of the inner cylinder, and drill six holes with a diameter of 80 s at equal intervals on the circumference in contact with the center and bottom side of the inner cylinder. The coating liquid was circulated between the cylinder and the inner and outer cylinders at a speed of 6017 minutes.

Using the electrodeposition coating liquid used in Example 1, 12 stainless steel plates (100 x 500 x 0゜5 m) were inserted into the anode at approximately equal intervals along the inner surface of the inner cylinder and connected to the cathode. Painting was done II! Painting was done at 25℃ and applied voltage 6
Direct current was applied for 3 minutes at 0v1 current. Then, it was thoroughly washed with tap water and left at room temperature for 10 minutes. After that, 180
Baking was performed at ℃ for 20 minutes to dry. As a result, there were no abnormalities such as pinholes, scratches, or bubbles in the appearance of the paint film, and the film thickness was 12.
A uniform and smooth electrodeposition coating film with a thickness of ~13 μm could be formed.

Comparative Example 1 An acrylic electrodeposition coating tank shown in FIG. 7 was used to electrocoat an aluminum object having the shape shown in FIG. 5.

Attach a hard PVC pipe to the bottom of the water tank for blowing out the electrodeposition coating liquid and to the bottom of the overflow tank for sucking the electrodeposition coating liquid.
It was overflowed and circulated at a rate of 1/min.

Using the electrodeposition coating solution used in Example 1, the object to be coated was connected to the anode, and two stainless steel plates (50 x 120 x 0.5M) inserted at approximately equal intervals on both sides of the inner wall of the water tank were connected to the cathode.
Electrodeposition painting was performed.

For electrodeposition coating, the liquid temperature is 25℃, the applied voltage is 60V, and the energization time is 3.
A branch direct current was applied. Then, after washing with tap water,
Baking and drying were performed at 180° C. for 20 minutes. As a result, bubbles and unevenness occurred in the coating film appearance, and an uneven electrodeposited coating film was formed with a coating thickness of 5 to 15 μm.

Comparative Example 2 An aluminum object having the shape shown in FIG. 4 was electrodeposited using a rectangular double-structure acrylic electrodeposition coating tank shown in FIG.

A hard vinyl chloride pipe is installed at the bottom of the inner tank for sucking out the electrodeposition coating liquid, and at the open bottom of the outer tank for sucking the electrodeposition coating liquid, and the coating liquid is circulated at a speed of 6017 minutes by overflowing from the inner tank to the outer tank. did.

Using the electrodeposition coating liquid used in Example 1, with the object to be coated as the anode, three stainless steel plates (100 x 500 x 0゜5 m) placed at approximately equal intervals on both sides of the inner wall of the inner tank were connected to the cathode. I applied a coat of paint.

For electrodeposition coating, the liquid temperature is 25℃, the applied voltage is 70V, and the energization time is 3.
A branch direct current was applied. Next, wash thoroughly with tap water,
It was left at room temperature for a minute. Thereafter, baking and drying were performed at 180° C. for 20 minutes. As a result, the appearance of the coating film showed craters and dust adhesion, and an uneven electrodeposition coating film was formed with a coating thickness of 8 to 20 μm.

(Effects of the Invention) Since the present invention is configured as described above, it produces effects as described below.

According to the present invention, it is possible to apply a uniform, smooth, and weather-resistant coating even to the concave surface of a large shade-shaped article such as a reflector of a large mercury lamp, for example, where it has been difficult to form a uniform coating film using electrodeposition coating. An electrodeposited coating film is formed which exhibits sufficient properties in terms of chemical resistance, scratch resistance, gloss, and reflectance. Also,
The electrodeposition coating apparatus of the present invention causes less loss and deterioration of the N@ coating solution, and can continuously perform uniform and smooth electrodeposition coating over a long period of time.

[Brief explanation of the drawing]

1, 2, and 3 (a) are plan views showing the main parts of the electrodeposition coating apparatus of the present invention, (b) are side sectional views, and (4)
5 and 5(a) are a plan view of a typical shade-shaped object to be coated, FIG. 5(b) is a side sectional view, FIG. The figure and Figure 8 (a) are
FIG. 2 is a plan view showing the main parts of a conventional electrodeposition coating device, and (b) is a side sectional view. Outer Cylinder Inner Cylinder Through Hole Pair Pole Pole Through hole on the pole 10° Paint liquid inflow tube Paint liquid outflow tube Hanger lead wire that also serves as electrical contact for the object to be coated Figure 1

Claims (2)

[Claims] (1) When electrocoating a hat-shaped article using an electrocoating liquid containing acrylic or melamine resin as the main component, an inner cylinder is designed to electrically conduct the electrocoating liquid in contact with the inner and outer walls. , fill the coating liquid in a double-tube electrodeposition coating tank consisting of an outer cylinder, immerse the object to be coated inside the inner cylinder, and place the coating liquid inside the inner cylinder or between the inner and outer cylinders. An electrodeposition coating method comprising: providing a counter electrode to the object to be coated, and applying a voltage between the object to be coated and the counter electrode to form a coating film on the object to be coated. (2) Consisting of a double cylinder that stores the electrodeposition coating liquid in the internal space, the inner cylinder has a structure that electrically conducts the coating liquid that is in contact with both walls, and an inflow conduit for the coating liquid is provided at the upper part between the inner and outer cylinders. In addition, an outflow pipe for the coating liquid is provided at the bottom of the inner cylinder, and
An apparatus for electrodeposition coating of a cap-shaped article, which is provided with a counter electrode for charging the object to be coated between the outer cylinders or near the inner wall of the inner cylinder.