JPS6223079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a coating film by electrodeposition coating, and in particular to a method of performing electrodeposition coating while peeling off the coating film adhering to a jig using a cationic type electrodeposition coating material. It is.

Electrodeposition coating is used as a primer coating for metal parts for vehicles. Conventionally, anionic type paints have been used in electrodeposition coatings, but cationic type paints have been used in recent years because the rust prevention effect is not good. Amino-modified epoxy resin paints are the mainstream of cationic paints, and the paint films formed with these paints have excellent adhesion to metal parts, and the paint itself has thin crosslinks, so it exhibits excellent rust prevention effects.
On the other hand, there was a problem in that a paint film was formed on the painting jig, such as a hanger, used when painting the other side, and it was difficult to remove it.

Electrodeposition coating uses a paint hanger to conduct electricity, so it is necessary to remove the paint film that adheres to the hanger. However, amino-modified epoxy resin-based electrodeposition coatings can be used to remove conventional anion-type electrodeposition coatings. It is difficult to dissolve using alkaline solutions, etc., which were used in For this reason, removal methods using removers based on organic acids such as formic acid and organic solvents such as methylene chloride have been proposed, but they cannot be removed completely and may impede current flow during the painting process or gradually There were problems such as peeling off and dispersing during painting, worsening the finish of the product.

This invention was made by focusing on the above-mentioned conventional problems, and involves bringing a coating jig on which a coating film has been formed into contact with a stripping solution, and sequentially applying parallel jet streams to the swollen coating film. It is an object of the present invention to provide a coating film forming method that can efficiently perform electrodeposition coating by spraying from different directions and peeling off the coating film.

This invention is a method of performing electrodeposition coating using a cationic electrodeposition paint to form a coating film on the surface of an object to be coated. Parallel jet streams formed in an oval pattern and overlapped at the tips of adjacent jet streams are sequentially applied to the membrane from different directions so that the angle relative to the jig changes as the jig moves. This is a coating film forming method characterized by spraying to peel off the coating, and using the jig from which the coating was peeled off again for electrodeposition coating.

The present invention will be explained below based on the drawings. FIG. 1 is a system diagram showing a coating line in one embodiment of the present invention. In the drawing, reference numeral 1 is an endless chain conveyor, to which hangers as painting jigs are attached at fixed pitches as described later, and it moves in the directions of arrows A and B, and moves in the directions of arrow C.
The object to be coated is carried in in the direction of arrow D, and the object to be coated is taken out in the direction of arrow D. In the moving direction, the pretreatment tank 2, draining drying chamber 3, electrodeposition tank 4, rinsing tank 5, baking drying chamber 6, peeling tank 7, peeling rinsing tank 8
is provided.

In the above painting line, hangers with objects to be painted are carried in the direction of arrow C and attached to the chain conveyor 1, and first in the pre-treatment tank 2, degreasing with alkali etc. and chemical conversion coating treatment with zinc phosphate etc. Pre-treatments such as the following are performed, and then draining and drying is performed in the draining and drying chamber 3. Next, electrodeposition tank 4
Electrodeposition is performed using a cationic electrodeposition paint made of amino-modified epoxy resin paint, connecting the object to be coated to the (-) pole and the paint to the (+) pole. A coating film is formed on the surface.
After washing away excess paint in the washing tank 5, baking drying is performed in the baking drying chamber 6 at about 180 to 210° C. for about 30 minutes, and the coated product is taken out in the direction of arrow D. On the other hand, the paint film adhering to the hanger from which the painted object has been removed is immersed in a stripping solution in a stripping tank 7, and the swollen coating film is sprayed with water in the next stripping and rinsing tank 8 to be stripped and removed.

Fig. 2 is a vertical sectional view showing a stripping device in an embodiment of the present invention, Fig. 3 is a plan view of its dipping tank, Fig. 4 is a sectional view thereof, and Fig. 5 is an enlarged view of the part shown in Fig. 2. It is a sectional view, and the same reference numerals as in FIG. 1 indicate the same or corresponding parts, and the stripping and washing tank 8 is the
Washing tank 9, second washing tank 10 and third washing tank 11
Consisting of

The chain conveyor 1 passes through a stripping tank 7, a first rinsing tank 9, a second rinsing tank 10, and a third rinsing tank 11 in order in the directions of arrows E and F, and hangers 13 are attached to a plurality of hooks 12. has been done.

A dipping tank 14 is provided at the bottom of the peeling tank 7, in which a peeling liquid 15 is stored, and the hanger 13 is moved in an immersed state.A jacket 16 is formed on the inclined side wall and bottom wall of the peeling tank 7. and constant temperature water is flowing. In addition, a closed liquid level 19 is formed by a partition wall 18, leaving a passage 17 for the hanger 13 at the liquid level of the immersion tank 14, and a regular hexagonal hollow floating body 20 made of light synthetic resin is formed on this closed liquid level 19. It's full. A layer of liquid paraffin 21 is formed on the surface of the stripping liquid 15.

At the bottoms of the first washing tank 9, the second washing tank 10, and the third washing tank 11, there are water tanks 22, 23, 2, respectively.
4 is provided, and overflow pipes 25 and 26 allow
It flows down from the water tank 24 to the water tanks 23 and 22 in sequence,
Water is drained from the water tank 22 through a drain pipe 27. In the first washing tank 9, the second washing tank 10, and the third washing tank 11, riser pipes 28, 29 are provided with a large number of nozzles arranged in a row so as to spray washing water from both sides across the passage of the hanger 13. , 30 are standing up, the riser pipe 28 is connected to the water tank 22 through the pump 31, the riser pipe 29 is connected to the water tank 23 through the pumps 32, 33, and the riser pipe 30 is connected to the water supply source. There is. riser pipe 28
A filter 34 made of a wire mesh basket is provided between the water tank 22 and the water tank 22, and the pumps 31, 3
2 and 33 are provided with screens 35, 36, and 37. A layer of antifoaming agent 39 is formed on the surface of the cleaning water 38 in the water tank 22 .

6 is a cross-sectional view of FIG. 2, FIG. 7 is a cross-sectional view along the water flow direction, and FIG. 8 is a cross-sectional view along the water flow direction. The riser pipes 28 are arranged in three pairs on each side of the chain conveyor 1 in the direction of movement, and rise in two groups.
a ₁ , 28b ₁ , 28a ₂ , 28b ₂ , 28a ₃ , 28b ₃ and 28a ₄ , 28b ₄ , 28a ₅ , 28b ₅ , 28a ₆ ,
Consists of 28b ₆ .

Among these, the riser pipes 28a ₁ , 28a ₃ , 28a ₅ are provided on the left side in the direction of movement of the conveyor 1, and are provided with a large number of nozzles 41 so as to form a parallel jet stream 40 diagonally upward. Pipe 28b ₁ ,
28b ₃ and 28b ₅ are provided on the right side in the traveling direction of the conveyor 1 so as to face them, and a large number of nozzles 4 are provided so as to form a diagonally downward parallel jet stream 40.
1 is provided. Riser pipe 28a ₂ , 28
a ₄ , 28a ₆ are provided on the left side of the conveyor 1, and are provided with a large number of nozzles 41 so as to form obliquely downward parallel jet streams 40, and riser pipes 28b ₂ , 28b ₄ , 28b A large number of nozzles 41 are provided on the right side of the _conveyor 1 so as to face the conveyor 1, and form a parallel jet stream 40 diagonally upward.

In this way, the riser pipes 28a ₁ and 28b ₁ , 28a ₃ and 28b ₃ , 28a ₄ and 28b ₄ , and 28a ₆ and 28b ₆ are provided facing each other, and the direction of the jet flow 40 is also opposite. The injection directions are shifted so that the collision positions do not coincide. On the other hand, riser pipes 28a ₂ and 28b ₂ , 28a ₅ and 28b ₅
The jet streams 40 are completely opposed to each other, and the collision positions of the jet streams 40 from the riser pipes on both sides are shifted from the center, so that the jet streams 40 as a whole are intensively sprayed onto the hanger 13. It is becoming more and more like this.

The arrangement of the riser pipes 29 in the second washing tank 10 is exactly the same, but three pairs of riser pipes 30 in the third washing tank 11 are arranged at intervals.

FIG. 9 is a schematic diagram showing the jet flow pattern in the first flush tank 9 and the second flush tank 10, FIG. 10 is a front view thereof, and FIG. 11 is a schematic diagram showing the jet flow pattern in the third flush tank 11. FIG. 12 is a front view thereof. When the nozzles 41 attached to the riser pipes 28 and 29 of the first washing tank 9 and the second washing tank 10 inject water at a water pressure of 1 to 3 kg/cm ² , the pattern 42 of the jet flow 40 obtained is an ellipse. The pattern 42 of the jet stream 40 overlaps with the pattern 42 of the adjacent jet stream 40 at its tip, and is arranged so that an overlapping part 43 is formed. On the other hand, the third washing tank 1
The pattern 46 of the jet stream 45 obtained from the nozzle 44 attached to the riser pipe 30 of No. 1 has a perfect circular shape, and is arranged so that overlapping portions 43 are formed at the upper and lower ends.

As the stripping liquid 15, a liquid containing an organic acid, an organic solvent, and a surfactant is used. As the organic acid, formic acid, oxalic acid, etc. can be used, and formic acid is particularly preferred. In addition, organic solvents that have the property of swelling or dissolving the coating film, such as methylene chloride,
Although trichlorethylene, trichloropropane, dichloropropane, etc. can be used, methylene chloride is particularly preferred. Any surfactant may be used as long as it imparts permeability to the stripping solution, such as sodium alkylbenzenesulfonate. In addition, auxiliary agents such as swelling promoters and antioxidants may be added. The blending ratio of organic acid is 5 to 50.
% by weight (preferably 10 to 40% by weight), the blending ratio of organic solvent is 60 to 90% by weight (preferably 65 to 85% by weight), and the blending ratio of surfactant is 1 to 10% by weight (preferably 2 to 85% by weight). 7% by weight). When liquid paraffin 21 is added to this stripping solution, liquid paraffin 2
1 forms a layer on the upper surface of the stripping liquid 15.

The antifoaming agent 39 may be any agent that forms a layer on the cleaning water 38 and can suppress the foaming of the surfactant mixed in the stripping liquid 15. For example, a metal soap-based antifoaming agent may be replaced with kerosene, kerosene, petroleum oil, etc. A solution dissolved in a solvent, vegetable oil, etc. can be used.

Hanger 13 attached to chain conveyor 1
A coating film is formed by electrodeposition in the electrodeposition tank 4, and is baked in the baking drying chamber 6 to harden and adhere to the hanger 13. Enter, soaking tank 1
4 is immersed in stripping liquid 15. Remover liquid 1
The coating film swells due to the action of step 5, but the surface tension of stripping solution 15 is reduced by the addition of surfactant.
The stripping liquid 15 penetrates into the gap between the hanger 13 and the paint film, and the stripping liquid 15 penetrates into the paint film attached to the hanger 13 from the outside and inside, so that the softening and swelling of the paint film is shortened. progress in time.

Figure 13a is a horizontal cross-sectional view of a part of the hanger with a coating film formed on it, b is a cross-sectional view of a square shape, c is a round cross-sectional diagram, and Figure 14a is a hanger with a swollen paint film. A horizontal cross-sectional view showing a part, b is a cross-sectional view when the hanger is square, and c is a cross-sectional view when the hanger 13 is round.
As shown in FIG. 13, the paint film 48 is in close contact except for the contact area 47 between the hanger 13 and the object to be coated. It swells and becomes floating. The immersion time required for swelling is about 1 to 10 minutes, preferably about 2 to 5 minutes. In this case, it is preferable that the square hanger 13 penetrates and swells from the corners 49.

Constant temperature water is flowed into the jacket 16, and the stripping liquid 1
5 is maintained at a temperature suitable for peeling, for example 15 to 25°C. The layer of liquid paraffin 21 formed on the upper surface of the stripping liquid 15 prevents the evaporation of the stripping liquid 15 in the dipping tank 14, and also covers the coated film 48 surface of the hanger 13 pulled up from the dipping tank 14, thereby preventing the evaporation of the solvent, etc. To prevent. Hollow floating body 20 floating on closed liquid surface 19
completely covers the liquid surface and prevents the stripping liquid 15 from evaporating. Further, the partition wall 18 has the function of a partition and a guide.

The hanger 13 pulled up from the dipping tank 14 is prevented from evaporating the solvent etc. with liquid paraffin, and is sent in a swollen state to the peeling and washing tank 8, where the coating film 48 is peeled off. In the peeling rinsing tank 8, water is directed toward the hanger 13 from a large number of nozzles 41, 44 provided in riser pipes 28-30 arranged on both sides of the hanger 13 in the first to third rinsing tanks 9-11. The sprayed and swollen coating film 48 is peeled off.

In the peeling operation, as shown in FIGS. 6 to 12, the hanger 13 attached to the conveyor 1
Once inside, as the conveyor 1 moves, parallel jet streams 40 are ejected from riser pipes 28a ₁ to 28a ₆ and 28b ₁ to 28b ₆ sequentially from different directions, and the coating film 48 is peeled off.

To explain this state in detail, as the conveyor 1 moves, it first moves diagonally upward from the left side by the riser pipe 28a ₁ , then diagonally downwards from the right side by the riser pipe 28b 1, and then diagonally downwards from the right side by the riser pipe 28b ₁ .
28a ₂ and 28b ₂ cause the jet stream 40 to flow diagonally downward from the left side and diagonally upwardly from the right side; furthermore, 28a ₃ causes the jet stream 40 to flow diagonally upwardly from the left side; and 28b ₃ causes the jet stream 40 to flow diagonally downwardly from the right side. are injected, and these are injected in a concentrated manner from three pairs of riser pipes, giving a strong impact force to the coating film.

When the direction of the nozzle 41 in the riser pipe 28 is changed to form jet streams in various directions on the same surface,
The jet streams collide to weaken the impact force on the coating film 48, but if the nozzles 41 are oriented in the same direction to form parallel jet streams 40 as in the present invention, the impact force is extremely large because no interference occurs. Become.
By shifting the injection direction from the opposing riser pipes and the adjacent riser pipes and shifting the impact position on the hanger 13, it is possible to eliminate mutual interference due to jet flows in different directions, and various types of jets can be sprayed in a narrow range. Strong impact force can be obtained even when sprayed in a concentrated direction. Also, if the jet stream 40 is alternately directed obliquely upward or downward, the hanger 13
Water can be applied from various angles, eliminating blind spots of water.

If the interval between the riser pipes 28 provided on both sides is too close, there will be a portion of the hanger 13 where the water does not hit, and if it is too far, the impact force of the water will be weakened.
The length is preferably about 0.8 to 1 m. Further, the interval between the riser pipes 28 on each side is preferably 5 to 20 cm, and the interval between the centers of each group is preferably about 1.5 to 2 m.

Since the pattern 42 of the jet stream 40 in the first washing tank 9 and the second washing tank 10 has an elliptical shape, the impact force is larger than in the case of a perfectly circular pattern 46. In the perfectly circular pattern 46, 80 to 90% of the water does not hit the hanger 13 and is wasted, and the amount of water that hits the hanger 13 per unit time is small, but in the oval pattern 42, water hits the hanger 13 intensively. Impact force increases.

Such a peeling operation is performed in two stages in the first washing tank 9 and the second washing tank 10,
Most of the coating film 48 peels off. In the third washing tank 11, a jet flow 45 having a perfect circular pattern 46 is ejected by a similar operation to prevent the hanger 13 from being exposed to water for a long time.
The remaining coating film 48 is peeled off and washed with water. When the peeling is almost completely performed in the first washing tank 9, the second washing tank 10
The pattern of the jet flow may be made into a perfect circle.

Most of the coating film 48 is peeled off in the first washing tank 9, but the peeled coating film is captured by the filter 34, and the washing water flows down into the water tank 22. At this time, stripping liquid 15
Foaming occurs due to the surfactant contained in the water tank 22, but since the antifoaming agent 39 is stored on the liquid surface of the water tank 22, the antifoaming action of the antifoaming agent 39 prevents foaming.
When the wash water flows down, the layer of antifoaming agent 39 is disturbed and becomes dispersed, but since the antifoaming agent 39 is concentrated in the upper part, the antifoaming effect is performed. Further, since the tip of the drain pipe 27 is below the liquid level, the amount of defoamer 39 discharged is small.

The paint film 48 of the hanger 13 peels off while passing through the peeling and washing tank 8, and is finally washed with water and carried out in the direction of arrow F. The object to be coated is mounted again from the direction of arrow C in FIG. 1 and the painting process begins. and subjected to electrodeposition coating.

In addition, in the above description, in the peeling rinsing tank 8, the direction of the parallel jet streams 40 may be sequentially jetted from different directions, and does not need to be in the order described above. It may be sprayed on. The patterns of the jet streams 40 and 45 are also not limited to those described above. In addition, a pretreatment tank 2, a draining drying room 3, an electrodeposition tank 4, a washing tank 5, a baking drying room 6,
The structures, operating methods, etc. of the stripping tank 7 and the stripping water tank 8 can be changed as appropriate. Furthermore, the present invention is applicable not only to the undercoat coating of metal members for vehicles but also to the coating of other objects to be coated.

As described above, according to the present invention, a coating jig on which a coating film has been formed is brought into contact with a stripping liquid, and the swollen coating film has an oval pattern and overlaps an adjacent jet stream at the tip. The parallel jet stream formed on the jig is sequentially sprayed from different directions so that the angle changes as the jig moves, and the paint film is peeled off. It can apply a strong impact force and remove the paint film completely and efficiently. Therefore, when the jig is supplied to the painting process, there is no obstruction of current flow due to the paint film, and the finish of the newly formed paint film on the object to be painted will not be deteriorated due to peeling of the paint film. Effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a coating line in one embodiment of the present invention, Fig. 2 is a vertical sectional view showing a stripping device in one embodiment, Fig. 3 is a plan view of the dipping tank, and Fig. 4 is the same. - Cross-sectional view, Figure 5 is the second
An enlarged sectional view of the part shown in the figure, Figure 6 is the same as in Figure 2.
7 is a cross-sectional view along the water flow direction, FIG. 8 is a cross-sectional view along the water flow direction, and FIG. 9 is a schematic diagram showing the jet flow pattern in the first flush tank and the second flush tank. 10 is its front view, FIG. 11 is a schematic diagram showing the jet flow pattern in the third washing tank, and FIG. 12 is its front view,
Figure 3a is a horizontal cross-sectional view of a part of a hanger with a paint film formed on it, b is a cross-sectional view of a square shape, c is a round cross-sectional view, and Figure 14a is a part of a hanger with a swollen paint film. A horizontal cross-sectional view showing the part, b is a square cross-sectional view, and c is a round cross-sectional view. In each figure, the same reference numerals indicate the same or equivalent parts, 1 is a chain conveyor, 2 is a pretreatment tank, 3 is a draining drying chamber, 4 is an electrodeposition tank, 5 is a washing tank, 6 is a baking drying chamber, and 7 is a Peeling tank, 8 is peeling washing tank, 9,1
0 and 11 are the first, second and third washing tanks, 12 is the hook,
13 is a hanger, 14 is a dipping tank, 22, 23, 2
4 is a water tank, 28, 29, 30 are riser pipes, 4
0 and 45 are jet streams, and 41 and 44 are nozzles.

Claims (1)

[Claims] 1. In a method of performing electrodeposition coating using a cationic electrodeposition paint to form a coating film on the surface of an object to be coated, the coating jig on which the coating film has been formed is brought into contact with a stripping solution. , a parallel jet stream formed in an oval pattern and overlapped at the tip with an adjacent jet stream is applied to the swollen coating film so that the angle relative to the jig changes as the jig moves. A coating film forming method characterized in that the coating film is sequentially sprayed from different directions to peel off the coating film, and the jig from which the coating film was peeled is again subjected to electrodeposition coating. 2. The parallel jet streams that are injected onto the coating film are formed so as to be injected diagonally upward and diagonally downward from riser pipes placed on both sides of the jig. 2. The coating film forming method according to claim 1, wherein the parallel jet streams formed by the riser pipes are formed such that angles with respect to the jig alternately change. 3 The parallel jet streams formed by the multiple riser pipes are concentratedly jetted from the multiple riser pipes arranged at different positions along the moving direction of the jig onto the jig passing a predetermined position. The coating film forming method according to claim 2, wherein