JPH01315366A - Coating method - Google Patents

Abstract

PURPOSE:To extremely prevent sagging from being caused before transfer to a drying stage by applying coating on the lateral face and the longitudinal face of a material to be coated at thickness not thinner than a slagging limit in an applying stage and rotating the coated material around a nearly horizontal axial line in the ensuing drying stage. CONSTITUTION:A coating method is equipped with both a coating stage P2 wherein a material W to be coated having the longitudinal face lengthened to the vertical direction and the lateral face lengthened to the horizontal direction is coated with coating and a drying stage for drying coating applied on the material W. This coating stage is finished by applying coating on the lateral face at thickness not thinner than a sagging limit and simultaneously thereafter applying coating on the longitudinal face at thickness not thinner than the sagging limit. In the ensuing drying stage, the coated material W is rotated around a nearly horizontal axial line (l). In other words, coating of the longitudinal face wherein sagging is easily caused at a time of transfer to the drying stage from the coating stage is performed later in comparison with a conventional method and therefore such possibilities that sagging is caused before transfer to the drying stage can be reduced regardless of a coating method for utilizing fluidity of coating.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a coating method.

(Prior art and its problems) When painting the outer surface of an object to be painted, such as an automobile body,
The method includes a preparation step for removing dust adhering to the object to be painted, a step for applying paint to the object to be painted, and a drying step for drying the applied paint. For example, in the case of thermosetting paints, this drying process is carried out in two stages: a setting process and a baking process. It is also called baking, and is carried out in an atmosphere at a temperature of 40° to 60'C (the baking temperature in the baking process is usually around 140°C).

The object to be coated is usually conveyed by a conveyance means such as a trolley through the preparation process, coating process, and drying process, but the posture of the object to be coated is maintained at a predetermined position in each process. It is still being done.

By the way, one criterion for evaluating the quality of a painted surface is smoothness (flatness), and the greater the smoothness, the smaller the degree of unevenness on the painted surface, and the better the painted surface. It is already known that in order to improve the smoothness of the painted surface, it is sufficient to increase the thickness of the paint film, that is, the film thickness of the applied paint.

On the other hand, paint sag is a factor that impairs the quality of painted surfaces. Paint sag refers to traces of paint sprayed on an object being moved by lrnm to 2 mm from the position of adhesion that can be visually confirmed on the painted surface before it hardens through the drying process. Therefore, if the above-mentioned trace exceeds at least 2 mm, it is considered that sagging has occurred.

Therefore, the film thickness within the sag limit means a thickness that does not cause sag during the drying process even if the paint is left as is after being sprayed. On the other hand, the film thickness greater than the sag limit means that the coating is so thick that it will sag at least during the drying process if the paint is left as it is after being sprayed.

The above paint sagging occurs when the applied paint flows downward under the influence of gravity, and the thicker the paint applied at one time, the more likely it is that sagging will occur.
Since the cause of this degree sag is ultimately the effect of gravity, it tends to occur on surfaces of the object to be coated that extend in the vertical direction, that is, so-called vertical surfaces.

Therefore, on surfaces extending in the horizontal direction of the object to be coated, where sagging of paint does not pose much of a problem, so-called lateral surfaces,
It is possible to apply a greater thickness of paint on the vertical surfaces than on the vertical surfaces. Furthermore, even if the thickness of the paint film on the horizontal and vertical surfaces is the same, the unevenness on the horizontal surface will be reduced due to slight flow of the paint that does not cause sagging, and the unevenness on the vertical surface will be smooth. This means that better smoothness can be obtained than the average degree of smoothness.

From the above-mentioned point of view, conventionally, in order to obtain a coated surface as smooth as possible while preventing "sagging" of the paint, painting was carried out using a paint with as little fluidity as possible.

Then, the paint sag occurs on the vertical surface. The so-called ``sag limit'' is, for example, for thermosetting paints, where the maximum paint film thickness is about 40 μm.More specifically, paint sag occurs during the setting process and baking process, especially during the baking The thickness of the paint applied in the painting process is determined to prevent sagging during this period, which is likely to occur during the process, and the maximum value of this determined thickness, that is, the sag limit value, is 40 μm.
It will be about. Therefore, in order to obtain a painted surface with even greater absolute smoothness, with conventional painting methods, it is necessary to repeat the series of steps from the painting process to the drying process multiple times, for example by applying two coats. was there. In this way, in terms of the thickness of the paint film, "sagging" is to be avoided as much as possible, so in the process of applying the paint, for example, in the case of electrostatic painting, care is taken only to prevent overspray. A painting gun is installed, and the specific layout is as shown in Fig. 13, when the object to be coated is an automobile body.
Guns 1, 2.3 apply paint to the vertical surface of the body W in order from the lag side to the advance side with respect to the direction of movement (from the left side to the right side (arrow direction) in the figure). It was common practice to place a top gun 4 for applying paint on the side surface of the body W.

By the way, regarding the above problem of smoothness, it is considered effective to rotate the object to be coated around a substantially horizontal axis during the drying process. In other words, by appropriately changing the direction of gravity acting on the paint applied to the object,
If the fluidity of paint is actively utilized, even if the thickness of the paint film remains the same, a coated surface with greater smoothness can be obtained. In order to fully obtain such an effect, it is necessary to apply the paint beyond the "sag limit", contrary to the conventional method.

However, if this is done in the same application order as before,
Because the vertical surfaces are applied first, sag occurs on the vertical surfaces of the object before the drying process begins, and it is difficult to repair it even if the object is rotated during the drying process. There is a possibility that an incident may occur.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a coating method that prevents sag as much as possible before moving on to the drying process when a coating material is applied in an amount exceeding the sag limit.

(Means and actions for solving the problem) In order to achieve the above technical problem, the present invention provides a method for applying paint to an object having a vertical surface extending in the vertical direction and a horizontal surface extending in the horizontal direction. Assuming that the coating method includes a coating step for applying the paint and a drying step for drying the paint applied to the object to be coated, in the coating step, the paint is applied to the side surface to a thickness exceeding the sag limit. At the same time as the application, or thereafter, the application process is completed by applying the paint to a thickness equal to or greater than the sag limit on the vertical surface, and in the drying process, the object to be coated is rotated around a substantially horizontal axis. It has a configuration that allows it to rotate.

According to the present invention, even if the thickness of the coating film is the same as in the past, the fluidity of the coating material can be used to create an excellent painted surface with fewer irregularities, that is, greater smoothness. can do.

Of course, even though the fluidity of the paint is used, the spraying does not move the paint significantly beyond 1 to 2 mm when visually observed from the original deposition position. More specifically, when paint is attached to an object to be coated, when viewed under magnification, due to the influence of surface tension, there are inevitably high areas (areas with large film thickness) and low areas (areas with small film thickness). is in a continuous state. The idea is to take advantage of the fluidity of the paint in these high areas to fill in the low areas immediately adjacent to it.

Furthermore, if you try to obtain a painted surface with the same smoothness, for example, the same level of smoothness as that obtained with conventional painting methods,
The film thickness of the paint to be applied can be made thinner than in the conventional method, and the amount of paint used can be reduced by the amount that can be made thinner.

Of course, for paints that cause sagging even in thin films, it is recommended to reduce the content of anti-sag agents that inhibit fluidity in conventional paints by a certain percentage, or increase the content of thinners such as thinner. You can get it by letting it happen.

On the other hand, to solve the problem that sagging tends to occur before the drying process begins, it is possible to finish the application on the vertical side later than or at the same time as the horizontal side. It is possible to shorten the transition time to the process, thereby reducing the possibility of sag occurring on the vertical surface before transition to the drying process.

(Example) Hereinafter, an example of the present invention will be described based on the attached drawings.

Support 5 11 FIG. 1 shows the entire process for painting an automobile body W as an object to be painted, and each process is indicated by PI-P4.

First, the body W, which has been undercoated by electrodeposition coating in a known manner, is sent to a preparatory step P1 while being held on a trolley. In this preparatory step PI, dust inside and outside the body W is removed by, for example, air blowing or vacuum suction. Next, after paint is sprayed onto the body W in step P2, the paint is dried in setting step P.
3 and a baking step P4.

If step PI-P4 is for intermediate coating, the body W is sent to the top coating step after step P4. Also, process P
If I-P4 is for topcoating, the body W is transported to an assembly line in a known manner.

Dust removal in the dust removal step P1 is preferably performed while rotating the body W around the horizontal axis β, as shown in FIG. That is, for example, first, the rotation of the body W is stopped in the state shown in FIG. 2(a) to remove dust, and then the dust is removed in the state shown in FIG. 2(b).
), the body W is stopped at this position, and the dust is removed again. In this way, the second
Dust is removed while the body W is intermittently rotated as shown in (c), (d), . . . (i) in the figure.

In this way, by removing dust while rotating the body W, it is possible to remove dust adhering to closed sections such as the inside corners of the roof panel and side sills of the body W, i.e., if the body W is not rotated. It becomes possible to completely remove even the garbage that does not fall.

The rotation range of the body W is 36 degrees as shown in FIG.
It may be rotated by 0°, but it may also be adjusted to match the rotation angle range of the body W in the drying process, which will be explained later.

Painting and Drying First, the spraying of the paint in P2, which will be explained in detail later, is carried out so that the thickness of the paint film exceeds the sag limit.

In other words, in conventional thermosetting paints, the maximum thickness of the paint that does not cause "sag", that is, the sag limit value, is about 40 μm, but in process P2, the thickness is much greater than this sag limit of 40 μm. The paint is sprayed to give a thick coating (eg 65 μm).

The reason why paint is applied by spraying is that it is possible to control the thickness of the paint film as desired. ). On the other hand, if the paint is applied by dipping, d i pp i
At the stage when the object to be coated is pulled up from the NG tank, a much larger movement of the paint occurs, which exceeds 1 to 2 mm according to the visual inspection described above. If the coating is applied above the sag limit and then rotated after -degree sag occurs, even after subsequent rotations, if the painted surface where the -degree sag has occurred, other painted surfaces where no sag occurs. It is not possible to obtain such smoothness.

After this P2, the process moves to a setting step P3.

In this setting process P3, before sagging occurs on the surface of the body W that has been painted in the painting process P2, for example, it is inverted in an angle range of up to 360° as shown in Fig. 2 (a) to (i). While doing so, the body W is rotated in the horizontal direction. That is, the body W is rotated about a rotation axis C that extends in the horizontal direction, and in the embodiment, this rotation axis a extends in the front-rear direction of the body W.

The rotational speed of the body W varies depending on the film thickness and viscosity of the sprayed paint, but is basically set to a rotational speed within a range between the following lower limit and upper limit. That is, the lower limit of the rotational speed is the minimum value of the rotational speeds at which the painted surface can be brought from at least a vertical state to a horizontal state before the paint on the painted surface moves by gravity and sag. Further, the upper limit value is the maximum value among the rotational speeds at which sagging does not occur due to centrifugal force generated by rotation. Note that when the body W is rotated around a substantially horizontal axis, the rotation axis may be inclined at an angle of about 30 degrees with respect to the horizontal axis, but it is preferable that this inclination is within 10 degrees.

The period during which the body W is rotated around the approximately horizontal axis is as follows:
A small amount (during the drying process, it is sufficient if the period is from before sag occurs to the coated surface until it hardens until no sag occurs.Of course, due to equipment considerations, the object to be coated must be rotated during the entire drying process. You can.

Further, this rotation may be continuous rotation in one direction, forward/reverse rotation that alternately performs forward rotation and reverse rotation, or intermittent rotation with a rotation stop period in between.

Note that the temperature atmosphere in this setting step P3 is set to room temperature in the example, but it can be set to an appropriate temperature in a lower temperature range than the temperature atmosphere in the next baking step P4, such as 40° to 60'C. It is possible. Of course, this setting process P3
This is to volatilize the low-boiling point components in the paint in advance, thereby preventing the generation of pinholes on the painted surface due to the rapid volatilization of the low-boiling point components in the next baking step P4.

In the baking step P4, the paint is baked in an atmosphere at a temperature of 140'C, for example. Even in this P4, P
Similarly to the setting step No. 3, the body W is rotated around a substantially horizontal axis while being reversed.

Due to the horizontal rotation of the body W at P3 and P4 described above, even if the paint is sprayed to a thickness exceeding the sag limit at P2, the paint dries without sagging. As a result, a high-quality coated surface with extremely high smoothness that could not be obtained with conventional coating methods can be obtained. Further, by performing the reversal, it is possible to prevent a situation where only the corners of the body W become extremely thick and bulge during the coating process.

The reason why the body W is rotated in both steps P3 and P4 is because a thermosetting paint that causes sagging is used in both steps P3 and P4, and in the case of powder paint, the body W is rotated in the baking step P4. In the case of a two-component curing type paint, it is sufficient to perform this rotation only during the setting process.

Here, if the rotation of the body W involves reversal, the following may be done, for example. That is, with the position shown in FIG. 2(a) as the reference position, one rotation of the body W with inversion
When considering the cycle, from state (a) to forward rotation direction (
2) and the reverse direction by a predetermined angle. For example, if both of the above predetermined angles are 90 degrees, the change in the posture of the body W is as shown in FIG.
(a)-= (b)-(c)-(b)-(a)(i)-
= (h) −(g) −(h) −(i) (a)
This makes one cycle. Of course, inversion is performed in the above states (c) and (g). Also, as another example.

If the above predetermined angles are both 135°, then l cycle is:
(a) = (b) = (c) → (d) → (c) → (b)
→(a)(i)-(h)→(g)→(f)→(g)-
(h)→(i)(a).

The inversion at this time is performed at the time of (d) and (f').

Of course, the above-mentioned predetermined angle may be determined so that the direction of gravity acting on the paint (particularly paint applied on a vertical surface) is changed, and the shape of the object to be coated, especially the position of the corner, is taken into consideration. .

Therefore, FIGS. 2(a) to (b), (c), and (d)
The manner of rotation accompanied by reversal can be set as appropriate, such as rotating it in order to (i) (after rotating it by 360 degrees) and then rotating it again by 360 degrees in the opposite direction.

Relationship between coating film thickness, sagging limit, smoothness, and horizontal a-rolling Figure 2 shows the influence of coating film thickness on the sagging limit when focusing on thermosetting paints. This third
In the figure, the coating thickness is 40um, 53gm, 65u
Three cases of m are shown. It is understood that for any of these thicknesses, peaks of "sag" occur both at the beginning of the setting process and at the beginning of the baking process.

In addition, the sagging limit is 1 to 2 m in the drying process P3 or P4.
m is the value at which sag occurs (if sag of 2 mm or more is visually observed, the painted surface is considered defective), and the maximum coating thickness that can be obtained within the range below this sag limit is The weight of paint is about 40 gm.

On the other hand, FIG. 4 shows the influence on the smoothness when the body W is rotated in the horizontal direction and when it is not rotated. A in FIG. 4 shows a state in which the body W is not rotated (conventional painting method). Figure 4B shows the body W
This figure shows the case where it is rotated by 90 degrees and then reversed (forward and reverse rotation between FIG. 2 (a) and (c)). FIG. 4C shows a case where the body W is rotated by 135 degrees and then reversed (forward and reverse rotation between FIG. 2(a) and FIG. 2(d)).

The fourth diagram shows the case where the body W is rotated 180 degrees and then reversed (forward and reverse rotation between FIGS. 2(a) and (e)). Fig. 4E shows the case where the body W is continuously rotated in the same degree in one direction (Fig. 2-(a), (b)
), (c)... Take the posture in the order of (i), and again (a
).

As is clear from Fig. 4, if the thickness of the coating is the same, it is better to rotate the body W (Fig. 4 B, C, D, E).
), thicker smoothness can be obtained than in the case of no rotation (FIG. 4A).

In addition, as is known, IG at the mapping sharpness shown in FIG.
(Image cross) indicates the ratio of sharpness to the mirror surface (black glass) as 100, and P
GD is a value at which the smoothness of the painted surface decreases as the degree of discrimination of the reflected image decreases from 1.0.

The test conditions for the data shown in FIGS. 3 and 4 are as follows, and these test conditions indicate the conditions when overcoating is performed at P2.

a, Paint: Melamine alkyd (black) Viscosity: 22 seconds/20'C with Ford cup #4 b, Coating machine: Minibell (16, OOOrpm) Shaping air 8.2, Okg/am2 C0 discharge rate = 2 times The first time was sprayed separately, ,
, 100cc/min 2nd time, 150~200cc/min, Setting time = IO minutes x room temperature e, Baking conditions: l 40' Cx25 molecules,
Base smoothness: 0.6 (PGD value) (intermediate coating, on PE tape) g0 rotation or reversal operating range: Setting (10 minutes) to baking (10 minutes) h, workpiece to be coated is a rectangular cylinder with a knee side of 30 cm. Painted on the side, rotatably supported in the center, rotation speed of the object to be painted: 6 rpm, 30 rpm, 60 r
pm, but there was no significant difference due to the difference in rotational speed.The causes of sagging in the setting process P3 and baking process P4 in the above-mentioned paint are as follows. First, the sagging in the setting process P3 occurs because the paint applied in the painting process P2 is wet and has fluidity, so the viscosity of the paint causes the film to be thicker than the conventional film thickness that does not cause smearing. Therefore, the gravitational force exerted by the paint is greater than the gravitational force, which is caused by the paint moving in the direction of gravity. On the other hand, the sag in the baking process P4 is
Due to the temperature in the baking process P4, the paint has fluidity before it hardens (usually so-called thermal flow), and the gravity applied to the paint exceeds the viscosity of the paint, causing the paint to move in the direction of gravity. It is something that occurs.

Specific Example 1 of Painting Process P2 (Figures 5 to 9) In this example, the paint is applied to the body W by electrostatic painting, and the application gun is a gun for vertical surfaces (side gun) 10 and a side gun (top gun) 12.
It consists of three types of guns: 0b and high 10c.

And each of these guns 10 (loa, job, 10c)
, 12 are arranged at intervals in the conveying direction of the body W (in the direction of the arrow shown in FIG. 5) in order to prevent a decrease in efficiency due to electrostatic repulsion. The side gun 10 and the top gun 12 are configured such that the top gun 12 is disposed on the lag side and the side gun 10 is disposed on the advance side in the conveyance direction of the body W. As the progress progresses, from top gun 12, side gun low 10a
, side gun middle lOb, and side gun high 10c, and after completing a series of spraying of paint, body W is carried out to process P3 (see FIG. 7). In the case of two stages in which the paint is sprayed twice, the above steps may be repeated as shown in Figure 8, or the steps may be repeated in the first stage as shown in Figure 9. Alternatively, the vertical surfaces may be applied first as in the conventional method.

Coating 1: Specific example 2 of P2 (Fig. 1O) In this example, spraying is performed by painting.

In this example, the horizontal nozzle 20 that discharges paint onto the horizontal surface of the body W that is stationary, and the vertical nozzle 22 that discharges paint onto the vertical surface, are connected in the longitudinal direction of the vehicle body. The horizontal nozzle 20 and the vertical nozzle 22 are arranged so that the horizontal nozzle 20 and the vertical nozzle 22 move synchronously. is installed. As a result, the spraying onto the body W is completed by the horizontal surface nozzle 20 first, and the vertical surface nozzle 22 is completed later. In addition, the vertical surface nozzle 22
and the side surface nozzle 20 may be arranged on the same line so that the spraying onto the body W by these nozzles 20, 22 is completed at the same time.

Modified examples of paint (Fig. ii, Fig. 12) The paint used in the present invention is preferably used in the coating process P.
Immediately after completing step 2 and before starting the rotation in setting step P3, it is appropriate that the film thickness be at least the sag limit at which sag does not occur. The coating film thickness defined in this way is determined by the viscosity of the paint, the content of the anti-sag agent, etc.
It's not about the rate.

FIGS. 11 and 12 show examples of paints that sag only in the setting step P3 but do not sag in the baking step P4. FIG. 11 shows an example of a two-component curing type paint, and FIG. 12 shows an example of a thermosetting type paint.

(The following is a blank space) The test conditions for the data shown in FIG. 11 are as follows.

a, Paint: Polyester urethane paint white (Nippon B Chemical (Suriso, product name R-263)) Main resin: Polyester polyol white Curing agent: Hexalmethylene diisocyanate Mixing ratio (weight ratio): 1 part curing agent to 4 parts main resin Painting machine: Pressure-feeding air spray gun (Iwata Painting Machine (suriso, product name: Wider W71), C8 spraying has a viscosity of 16/Ford Cup #4d, paint discharge rate: 350cc/min, M version) Air pressure: 4.0 kg 7 cm 2 f, spraying distance: 30 cm g, number of coats: 2 times (3 minute interval) Figure 12 shows the temperature of this thermosetting paint when using a thermosetting paint as the paint used in step P2. FIG.
It's a minute.

Further, in the baking step, the temperature was raised from 20° C. to 140° C. over 8 minutes, and then this 140° C. state was maintained for 25 minutes.

Figure 12 shows a total of three test examples a to c, that is, examples of thermosetting paints that can be used in the present invention, but the specific test conditions for obtaining such data are as follows. It is as follows. In addition, in the following explanation, things that are not particularly distinguished between Test Examples a to C are common matters.

(11 Paint/Solvent dilution thermosetting Melaminal Kid (hue black) - Dilution solvent triol 4% (wt%) Tsurupetz 10
0 3% (weight %) (manufactured by Esso) Truvet 200 3% (weight %) (manufactured by Esso) ・Anti-sag agent Pre-crosslinked acrylic resin, all numbers indicating the amount added are expressed as weight % based on non-volatile content. It is shown in Table 1 along with the viscosity.

- All viscosity values are for Ford Cup #4/20''C, and are shown in Table 1 along with the content ratio of anti-sagging agent.

(2) Painting conditions Table 2 shows two-stage blowing.

Setting and baking are as described above.

(3) Test plate - Cold rolled steel plate treated with zinc phosphate - Undercoat cationic electrodeposition 170℃ x 25 minutes baking: film thickness 25μm - Intermediate coating 140℃ x 25 minutes baking: film thickness 40um - Intermediate coating wet sanding #800 water resistant Complete water sanding with abrasive paper (4) Evaluation method With the test plate from (3) above set vertically, top coats were applied under the above-mentioned coating conditions with various paint viscosity and anti-sagging agent content. . A paint that causes blurring in the subsequent setting process but does not cause blurring in the baking process is shown in Figure 15 as Test Example a''-c. , PG when the test plate is rotated around the horizontal axis at a speed of 1 Or pm until no wobbling occurs during the setting process.
The D value was measured using a resolution gloss meter, but only test example C was PG.
Although good results were obtained with a D value of ro and 9J, other test examples a and b had extremely excellent results with a PGD value of rl and OJ.

(The following is a blank space) Table 1 Table 2 Here, as the paint used for painting the automobile body W, as shown in Table 3 below, the number average molecular weight of the paint resin is preferably in the range of 2000 to 20000.

Number average molecular weight of 2000-2000 for automobile paint
The reason why it is preferable to set it in the range of 0 is that if it is less than 2000, it corresponds to a paint that is cured by electron beam or ultraviolet light, and this paint has a high crosslinking density and is brittle, so it is not durable (2 to 3
), it is not very desirable for use in automobile exterior panels. In addition, if it exceeds 20,000, the viscosity will be high (because of this, a large amount of solvent will be required and a large amount of solvent will be discharged), which is undesirable.Furthermore, for latex polymers with a number average molecular weight exceeding 20,000, the viscosity will increase immediately after spraying. (This makes it difficult to improve smoothness, which is undesirable.

Table 3 Although the present invention has been described in detail above, the present invention is not limited thereto (and includes the following modifications).

■The coating thickness may be the same as before.

■In order to increase the fluidity of the paint, the amount of thinner or other thinner may be increased in place of the coating thickness, or the amount of anti-sagging agent added may be reduced.

■If the problem of pinholes does not occur, the setting process may be omitted.

(Effects of the invention) As is clear from the above explanation. According to the present invention, by actively utilizing the fluidity of the paint, it is possible to obtain a coated surface with excellent smoothness even if the film thickness is the same as that of the conventional paint. Additionally, since the application on vertical surfaces, where sagging is more likely to occur during the transition from the coating process to the drying process, is delayed compared to conventional methods, the drying process cannot be applied even though this is a painting method that takes advantage of the fluidity of the paint. It is possible to reduce the risk of sag occurring in the front.

[Brief explanation of the drawing]

FIG. 1 is an overall process diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing a state in which the posture of an automobile body as an object to be coated changes as it rotates. Figures 3 and 4 are graphs showing the relationship between paint thickness and sag, paint surface smoothness, and rotation. FIGS. 5 and 6 are diagrams showing the arrangement of painting guns in the coating process. FIG. 7 to FIG. 9 are block diagrams showing the order of coating on the vertical and horizontal surfaces of the object to be coated. Figure 10 is a layout diagram of the nozzle for spraying paint when spraying is for painting. FIG. 11 and FIG. 12 are diagrams showing dripping characteristics of paint suitable for use in the present invention. FIG. 13 is a diagram showing the arrangement of conventional painting guns. P2: Coating process W: Body (object to be coated) D = Cart 2 rotation axis lO: Side gun (gun for vertical surfaces) 12 Nidotsubu gun (gun for horizontal surfaces) 20: Nozzle for horizontal surfaces 22: Nozzle for vertical surfaces

Claims (1)

[Claims] (1) Coating comprising a coating process of applying paint to an object having a vertical surface extending in the vertical direction and a horizontal surface extending in the horizontal direction, and a drying process of drying the paint applied to the corrugated object. In the method, in the coating step, the paint is applied to the horizontal surface to a thickness equal to or greater than the sag limit, or at the same time, the paint is applied to the vertical surface to a thickness equal to or greater than the sag limit. A coating method, characterized in that the coating step is completed, and in the drying step, the object to be coated is rotated around a substantially horizontal axis.