JP2010036126A - Coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method in which energy consumed in a coating line is reduced and a space required for constructing the coating line is cut down while the coating defect of parts constructing an automobile body is suppressed. <P>SOLUTION: The coating method includes the following processes, which are performed on the coating line: an electrodepositing drying process of drying the parts 31 constructing the automobile body electrodeposition-coated with a water paint in an electrodepositing drying furnace 4, a sealer coating process of coating a predetermined parts of the parts 31 with a sealing material in a sealing material coating booth 6 after the electrodepositing drying process, an intermediate coating process of intermediate-coating the parts 31 coated with the sealing material in an intermediate coating booth 9, and a top coating process of top-coating the parts 31 intermediate-coated in a top coating booth 10, wherein the coating line of the sealer process, the intermediate coating process and the top coating process are humidified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a painting method, and more particularly, to a method for painting a member constituting an automobile body.

2. Description of the Related Art Conventionally, in a method for painting a member constituting an automobile body, reduction in energy consumption and reduction in space required for installation of painting equipment have been promoted.
For example, for a vehicle body assembled by welding each part, an electrodeposition coating process for electrodepositioning a base paint, a sealing agent application process for applying a sealing agent to a predetermined part of the vehicle body after the electrodeposition coating process, The sealing agent drying process, in which only the predetermined part is heated to dry the sealing agent, the intermediate coating process in which the intermediate coating is applied to the vehicle body after completion of the sealing agent drying process, and the intermediate coated vehicle body is dried to be intermediate An intermediate coating drying process for forming a coating film, a top coating process for applying a finish paint to a vehicle body on which an intermediate coating film has been formed, and a baking process for baking and drying the coated vehicle body to form a final coating film are performed. A coating film forming method has been proposed (see, for example, Patent Document 1).

In this method, the sealing agent drying process is partially heated to heat only a predetermined part of the vehicle body, thereby reducing the size of the sealer drying furnace, thereby reducing the energy required for the operation of the sealer drying furnace and The space required for the installation is reduced.
JP 2003-200110 A

However, after the base film formed by electrodeposition coating is dried, if dust adheres to the surface of the film and is applied in an intermediate or overcoating state in this state, the coating film formed in these processes may have irregularities or other irregularities. There is a risk of paint failure.
For this reason, in the above method or the like, a wiping step of wiping off dust or the like adhering to the coating film surface with a waste cloth is provided before the intermediate coating step so as to suppress coating defects. In the wiping process, since the structural member of the automobile body and the waste are in direct contact with each other, if the wiping process is provided before the sealing agent drying process, the sealing agent may be deformed by contact with the waste. Therefore, the wiping process needs to be provided after the sealing agent drying process.

  On the other hand, in recent years, an electrodeposition drying furnace for drying a base coating film (electrodeposition coating film) in order to further reduce the energy consumed in the coating process and further reduce the space required for installation of coating equipment, From a four drying oven coating line comprising a sealer drying oven for drying the sealant, an intermediate drying oven for drying the intermediate coating and a top drying oven for drying the finished coating, a sealer drying oven and an intermediate coating oven It is desired to construct a two-dry oven coating line in which is omitted.

However, since there is no sealing agent drying process in the 2 drying furnace coating line, it is difficult to provide a complete wiping process, and as a result, there is a risk of coating failure.
An object of the present invention is to provide a painting method capable of reducing energy consumed in a painting line and reducing a space required for construction of the painting line, while suppressing painting defects of members constituting an automobile body. There is.

  In order to achieve the above object, a painting method of the present invention is a painting method performed on a painting line for painting a member constituting an automobile body by a flow operation, wherein the member electrodeposited is applied. An electrodeposition drying step for drying; an application step for applying a sealing material to a predetermined portion of the member after the electrodeposition drying step; and an intermediate coating step for intermediate-coating the member coated with the sealing material with a water-based paint. And an overcoating step of overcoating the intermediately coated member, and the coating line is humidified in the application step, the intermediate coating step and the overcoating step.

  According to this method, after the coating step of applying the sealing material, the intermediate coating step is performed without the sealing material drying step of drying by heating the sealing material. Therefore, installation of a sealer drying furnace for drying the sealing material can be omitted. As a result, the energy required to operate the sealer drying furnace can be reduced, so that the energy consumed in the painting line can be reduced. In addition, by omitting the installation of the sealer drying furnace, the space required for the construction of the painting line can be reduced.

  Moreover, since the coating line is humidified in the coating process, the intermediate coating process, and the overcoating process, dust can be prevented from being scattered into the atmosphere through these processes after the electrodeposition drying process. Therefore, it is possible to suppress the adhesion of dust to the surface of the members constituting the automobile body that has been electrodeposited. As a result, it is possible to prevent unevenness and the like from being generated on the coating film, and to suppress coating defects.

In the coating method of the present invention, the coating line is provided with a drying furnace in the electrodeposition drying step, and the drying furnace is heated from above with respect to the member transferred on the coating line. It is preferable to include a first drying zone to which the hot water is added and a second drying zone that is disposed downstream of the first drying zone and supplies hot air to the member from below.
It is more difficult to raise the temperature of the lower end portion of the automobile body, particularly the left and right rocker portions than the other portions. Therefore, in the method of drying by heating from above the automobile body, a difference in temperature rise occurs between the lower end portion of the automobile body and the other parts. In such a drying method, if the automobile body is dried on the basis of the temperature rise at the lower end, the temperature rise in other parts becomes excessive, and there is a risk of causing a coating failure.

Thus, a method of drying by applying heat from below the automobile body is studied. However, when hot air or the like is supplied from below and heated, dust may be scattered into the atmosphere and adhere to the automobile body.
In this method, the member is dried by applying heat from above in the first drying zone, and further, the member is dried by supplying hot air from below in the second zone. Therefore, the entire member can be uniformly dried. it can.

Moreover, by first heating the member by applying heat from above, the surface layer of the coating film can be formed on the surface of the member before the supply of hot air from below. Even if dust is scattered into the atmosphere by supplying hot air, the scattered dust can be prevented from coming into close contact with the member.
Furthermore, in the coating method of the present invention, the shape of the sealing material is maintained in the coating line with respect to the member transferred on the coating line between the coating process and the intermediate coating process. It is preferable that air injection means for injecting air is provided.

  In this method, since air is sprayed onto the members constituting the automobile body after the application process, for example, even if dust adheres to a portion where the sealing material is applied in the application process, the dust is removed from the air. It can be removed by jetting. Furthermore, since air is injected so that the shape of the sealing material is maintained, deformation of the sealing material can be suppressed. Therefore, generation | occurrence | production of the irregularities etc. in the surface of the water-based coating material coated on a sealing material can be suppressed.

  As a result, coating defects can be suppressed.

  According to the coating method of the present invention, installation of a sealer drying furnace for drying the sealing material can be omitted. As a result, the energy required to operate the sealer drying furnace can be reduced, so that the energy consumed in the painting line can be reduced. In addition, by omitting the installation of the sealer drying furnace, the space required for the construction of the painting line can be reduced.

  Moreover, it is possible to suppress the adhesion of dust to the surface of the members constituting the automobile body that has been electrodeposited. As a result, the occurrence of irregularities such as unevenness in the coating film can be prevented, and coating defects can be suppressed.

FIG. 1 is a process diagram showing an embodiment of a coating method of the present invention. FIG. 2 is a schematic cross-sectional view showing a layer structure of a coating film formed on a member constituting the automobile body.
1 is a coating method in which a base coating film 32, an intermediate coating film 33, and a top coating film 34 are sequentially formed on a member 31 (see FIG. 2) that constitutes an automobile body. It is carried out on the painting line where painting is performed by flow work.

  The painting line includes a conveyor 18 (described later) for transferring a member 31 to be painted, and the members 31 to be painted are transferred to the conveyor 18 one by one at intervals. In addition, on the conveyor 18, as a booth in which various processes are performed from the upstream side to the downstream side, for example, the pretreatment booth 2, the electrodeposition coating booth 3, the electrodeposition drying furnace 4, A landing inspection booth 5, a sealing material application booth 6, a UBC booth 7, a cleaning booth 8, an intermediate coating booth 9, a top coating booth 10, a top drying oven 11, and a final inspection booth 12 are provided in this order. ing.

Hereinafter, this coating method will be described together with the explanation of each booth with reference to FIG. 1 and FIG.
In this coating method, for example, a member 31 transferred from a body forming line (not shown) for forming an automobile body by pressing and welding a steel plate or the like is first pretreated in the pretreatment booth 2 (pretreatment). Process).

In the pretreatment process, for example, a rust removing process for removing rust generated in the member 31, a degreasing process for removing oil such as a lubricating oil used during press working, and the like are executed.
Next, the pretreated member 31 is electrodeposited with, for example, a water-based paint in the electrodeposition coating booth 3 (electrodeposition coating process).
The water-based paint (electrodeposition water-based paint) used for electrodeposition coating is not particularly limited. For example, a water-based paint containing a water-soluble or water-dispersible resin component and a curing agent is used.

  Examples of the resin component include a hydrophilic group (for example, a carboxyl group, a hydroxyl group, a methylol group, an amino group, a sulfonic acid group, and a polyoxyethylene bond) and a functional group that reacts with a curing agent (for example, a hydroxyl group). Aqueous resin having Specific examples include known aqueous resins such as acrylic resins, polyester resins, alkyd resins, epoxy resins, melamine resins, and polyurethane resins. These can be used alone or in combination of two or more. Of these, an epoxy resin is preferable.

Depending on the type of hydrophilic group, such a resin component may be neutralized with a base or acid to be water-solubilized or water-dispersed. Decentralize.
It does not restrict | limit especially as a hardening | curing agent, For example, a melamine resin, block polyisocyanate, etc. are mentioned. Specifically, examples of the melamine resin include hydrophilic melamine, and examples of the blocked polyisocyanate include, for example, the isocyanate group of the polyisocyanate blocked with a blocking agent such as oxime, phenol, alcohol, lactam, and mercaptan. Things. These can be used alone or in combination of two or more. Of these, block polyisocyanate is preferable.

For electrodeposition water-based paints, coloring pigments, light interference pigments, extender pigments, dispersants, anti-settling agents, organic solvents, reaction accelerators (such as organotin compounds), antifoaming agents, thickening as necessary Known additives such as additives, rust preventives, ultraviolet absorbers and surface conditioners can be appropriately blended.
And each said component is mix | blended with water by a well-known method, and the solid content density | concentration is 15-30 weight%, for example, Preferably it is 18-25 weight by water-soluble or water-dispersing a resin component, for example. The electrodeposition water-based paint is prepared so as to be%.

Examples of the coating method of the electrodeposition water-based paint prepared as described above include known electrodeposition coating methods such as cationic electrodeposition coating and anion electrodeposition coating, and preferably cationic electrodeposition coating.
After the electrodeposition coating process, the electrodeposited member 31 is dried in the electrodeposition drying furnace 4 (electrodeposition drying process).

The electrodeposition drying furnace 4 has a preliminary drying zone 13 (see FIG. 3) and a first drying zone 14 downstream of the preliminary drying zone 13 (FIG. 4) from the upstream side to the downstream side in the transfer direction of the member 31. And a second drying zone 15 (see FIG. 5) on the downstream side of the first drying zone 14.
FIG. 3 is a schematic configuration diagram of the inside of the preliminary drying zone 13 as viewed from the downstream side in the transfer direction of the member 31. FIG. 4 is a schematic configuration diagram of the inside of the first drying zone 14 as viewed from the downstream side of the member 31 in the transfer direction. FIG. 5 is a schematic configuration diagram of the inside of the second drying zone 15 as viewed from the downstream side in the transfer direction of the member 31.

Hereinafter, the electrodeposition drying process in the electrodeposition drying furnace 4 will be described with reference to FIGS.
The electrodeposition drying furnace 4 includes a floor 22, a ceiling 21 that faces the floor 22 in the vertical direction, and a pair of the floor 22 and the ceiling 21 that face each other in the width direction perpendicular to the transfer direction of the member 31. Wall 28.
On the floor 22, a conveyor 18 for transporting the members 31 is installed with a pair of walls 28 at intervals. The member 31 is supported by a carriage 19 that is movably mounted on the conveyor 18, and is transferred through the electrodeposition drying furnace 4.

In the electrodeposition drying process, the electrodeposited member 31 is first heated in the preliminary drying zone 13 (preliminary heating process).
In the pre-drying zone 13, the upper corner of the generally bowl-shaped electrodeposition drying furnace 4 formed in a manner that the ceiling 21 and the walls 28 of the electrodeposition drying furnace 4 are substantially perpendicular to each other is formed in the width direction. Plural pairs of preliminary hot air dryers 20 facing each other are installed. In FIG. 3, only one pair of the plurality of pairs of preliminary hot air dryers 20 is shown.

In the preliminary hot air dryer 20, air outlets 24 for blowing hot air are formed at the positions facing the both ends of the conveyor 18 in the width direction so as to face the lower side in the width direction.
In the preheating step, hot air is blown along the side surface of the member 31, for example, by blowing hot air from the outlet 24 located on the outer side in the width direction with respect to the member 31 transferred on the conveyor 18. Hot air is blown onto the inner surface of the member 31 through an opening (for example, a window formed on the side panel) formed on the side surface, thereby heating the member 31.

  The preheating condition is such that the hot air blowing temperature is lower than the hot air blowing temperature in the first heating step and the second heating step described later, and is, for example, 80 to 130 ° C, preferably 90 to 110 ° C. Moreover, the blowing speed of hot air is 5-15 m / s, for example. Moreover, the wind speed in the coating surface (surface of the member 31) of a hot air is 2-5 m / s, for example. The distance from the hot air outlet to the surface to be coated is, for example, 30 to 80 cm. Furthermore, the heating time is, for example, 3 to 10 minutes.

Moreover, the temperature in the preliminary drying zone 13 is 70-110 degreeC, for example, Preferably, it is 80-100 degreeC.
Next, in the electrodeposition drying step, the preheated member 31 is heated in the first drying zone 14 (first heating step).
In the first drying zone 14, as in the preliminary drying zone 13, a plurality of pairs of first hot air dryers 23 that are opposed to each other in the width direction are installed at the upper corner of the substantially bowl-shaped electrodeposition drying furnace 4. . In FIG. 4, only one pair of the multiple pairs of first hot air dryers 23 is shown.

In the first hot air dryer 23, air outlets 25 for blowing hot air are formed so as to face the lower side in the width direction at positions opposed to both ends of the conveyor 18 in the width direction.
Also in the first heating step, similar to the preheating step, for example, by blowing hot air from the outlet 25 located on the outer side in the width direction with respect to the member 31 transferred on the conveyor 18, for example, Hot air is blown along the side surface, and hot air is blown onto the inner surface of the member 31 through an opening (for example, a window formed on the side panel) formed on the side surface to heat the member 31.

  The condition of the first heating is that the hot air blowing temperature is higher than the hot air blowing temperature in the preheating step and lower than the hot air blowing temperature in the second heating step described below, for example, 100 to 170 ° C., preferably Is 130-150 degreeC. Moreover, the blowing speed of hot air is 5-15 m / s, for example. Moreover, the wind speed in the coating surface (surface of the member 31) of a hot air is 2-5 m / s, for example. The distance from the hot air outlet to the surface to be coated is, for example, 30 to 80 cm. Furthermore, the heating time is, for example, 5 to 15 minutes.

Moreover, the temperature in the 1st drying zone 14 is 120-150 degreeC, for example, Preferably, it is 130-140 degreeC.
Next, in the electrodeposition drying step, the first heated member 31 is heated in the second drying zone 15 (second heating step).
In the second drying zone 15, a width is formed at the lower corner of the substantially bowl-shaped electrodeposition drying furnace 4 formed by the floor 22 and the walls 28 of the electrodeposition drying furnace 4 being substantially perpendicular to each other. A plurality of pairs of second hot air dryers 27 are installed so as to face each other across the conveyor 18 in the direction. In FIG. 5, only one pair of the plurality of pairs of second hot air dryers 27 is shown.

The second hot air dryer 27 is formed with an air outlet 26 for blowing hot air at a position substantially the same height as the upper surface of the conveyor 18 so as to face the upper side in the width direction.
In the second heating step, for example, hot air is blown to the bottom surface of the member 31 by blowing hot air from the air outlet 26 located on the lower outer side in the width direction of the first heated member 31 transferred on the conveyor 18. To heat the member 31.

  The condition of the second heating is that the hot air blowing temperature is higher than the hot air blowing temperature in the preliminary heating step and the first heating step, and is, for example, 140 to 200 ° C, preferably 150 to 190 ° C. Moreover, the blowing speed of hot air is 10-15 m / s, for example. Moreover, the wind speed in the coating surface (surface of the member 31) of a hot air is 2-5 m / s, for example. The distance from the hot air outlet to the surface to be coated is, for example, 30 to 80 cm. Furthermore, the heating time is, for example, 10 to 15 minutes.

Moreover, the temperature in the 2nd drying zone 15 is 140-180 degreeC, for example, Preferably, it is 150-170 degreeC.
And by performing a preheating process, a 1st heating process, and a 2nd heating process, the electrodeposition water-based coating material apply | coated to the member 31 dries, and the primer coating film 32 is formed in the surface of the member 31 .

The thickness of the undercoat coating film 32 to be formed is, for example, 5 to 30 μm, or preferably 10 to 20 μm.
After completion of the electrodeposition drying process, for example, the electrode 31 of the preceding member 31 is attached to the member 31 having the primer coating film 32 formed in a first storage space (not shown) for holding the member 31. Hold until the inspection process starts.

  This first storage space is preferably humidified. Specifically, although it varies depending on the temperature (space temperature) in the first storage space, for example, it is preferable that the relative humidity is 50 to 90% when the space temperature is 25 to 35 ° C., More preferably, the moisture is 60 to 70%. Moreover, it is preferable that it is humidified so that it may become 50-80% of relative humidity when space temperature is 5-15 degreeC, and it is still more preferable that it is humidified so that it may become 60-70%.

As a method of humidifying the inside of the first storage space, for example, a humidifier is installed in the first storage space, the humidifier is operated and humidified, and a water spigot is provided on the floor of the first storage space. Examples of the method include watering the floor from the water sprinkler to humidify, and a method in which a person waters the floor with a hose to humidify the floor.
Then, when the electrodeposition inspection process for the preceding member 31 is completed, the member 31 in the first storage space is transferred to the electrodeposition inspection booth 5 and subjected to the electrodeposition inspection in the electrodeposition inspection booth 5 (electrodeposition inspection). Process).

In the electrodeposition inspection step, for example, the undercoat coating film 32 is visually inspected for defects such as blisters and sagging. Then, in the case where irregularities and / or sagging have occurred, the undercoat film 32 is polished with a polishing tool such as water-resistant abrasive paper (water-resistant paper) in order to remove the irregularities and / or sagging. Wipe off the resulting sharpened residue with a waste cloth.
Note that the looseness refers to, for example, small particles generated on the undercoat film 32 when dust or the like adheres to the surface of the member 31 before the electrodeposition coating process and is electrodeposited while the dust or the like is adhered. It is. Further, the sagging means that the paint remaining in the gap between the mating portions of the steel plates in the member 31 boils in the drying step and blows out on the surface of the member 31.

  It is preferable that the electrodeposition inspection booth 5 is humidified in the electrodeposition inspection step. Specifically, although it varies depending on the room temperature of the electrodeposition inspection booth 5, for example, it is preferably humidified so that the relative humidity is 50 to 90% when the room temperature is 25 to 35 ° C. It is more preferable to be humidified to be%. Moreover, it is preferable that it is humidified so that it may become 50-80% of relative humidity when indoor temperature is 5-15 degreeC, and it is still more preferable that it is humidified so that it may become 60-70%.

As a method for humidifying the inside of the electrodeposition inspection booth 5, for example, the above-described humidification method may be mentioned.
After completion of the electrodeposition inspection process, the sealing material is applied to a predetermined portion of the member 31 in the sealing material application booth 6 (the sealer application process).
The predetermined portion of the member 31 is, for example, a joint between the steel plate and the steel plate in the member 31 that is generated by joining the steel plate and the steel plate by spot welding in the body forming line (not shown). It is.

The sealing material used in the sealer coating step is not particularly limited, and examples thereof include acrylic resins.
In the sealer application process, for the purpose of preventing the entry of water and outside air from the seam, for example, a sealant is applied to the portion by hand, and the shape of the sealant is adjusted with a spatula or the like, if necessary. Thereby, the predetermined part of the member 31 is sealed with the sealing material in a wet state.

  In the sealer coating process, the inside of the sealant coating booth 6 is humidified. Specifically, although it varies depending on the room temperature of the sealing material application booth 6, for example, when the room temperature is 25 to 35 ° C., it is humidified so as to have a relative humidity of 50 to 90% and becomes 60 to 70%. It is preferable to be humidified. Moreover, it is humidified so that it may become relative humidity 50-80% when indoor temperature is 5-15 degreeC, and it is preferable to be humidified so that it may become 60-70%.

As a method of humidifying the inside of the sealing material application booth 6, for example, the above-described humidification method may be mentioned.
Next, the member 31 to which the sealing material is applied is subjected to UBC (Under Body Coating) treatment in the UBC booth 7 without drying the wet sealing material with a drying furnace or the like (UBC process).

In the UBC process, for example, an undercoat is applied to the part 31 for the purpose of preventing peeling due to chipping of the undercoat film 32 formed on the part 31 that is susceptible to chipping, such as a tire house (not shown) of the member 31. The material is applied manually or by robot.
The undercoat material used in the UBC process is not particularly limited, and examples thereof include acrylic resins.

  In the UBC process, the UBC booth 7 is preferably humidified. Specifically, although it depends on the room temperature of the UBC booth 7, it is preferably humidified so that the relative humidity is 50 to 90% when the room temperature is 25 to 35 ° C, for example, to 60 to 70%. More preferably, it is humidified. Moreover, it is preferable that it is humidified so that it may become 50-80% of relative humidity when indoor temperature is 5-15 degreeC, and it is still more preferable that it is humidified so that it may become 60-70%.

As a method for humidifying the inside of the UBC booth 7, for example, the above-described humidification method may be mentioned.
After the UBC process is completed, the UBC-treated member 31 is passed through, for example, a second storage space (not shown) in which the member 31 can be retained, and then the cleaning booth 8 for performing the cleaning process. Transport continuously.
The second storage space is preferably humidified. Specifically, although it varies depending on the temperature in the second storage space (space temperature), for example, it is preferable that the relative humidity is 50 to 90% when the space temperature is 25 to 35 ° C., More preferably, the moisture is 60 to 70%. Moreover, it is preferable that it is humidified so that it may become 50-80% of relative humidity when space temperature is 5-15 degreeC, and it is still more preferable that it is humidified so that it may become 60-70%.

As a method for humidifying the inside of the second storage space, for example, the above-described humidification method may be mentioned.
And in the clean booth 8, the air blow process which injects air to the member 31 is performed (air blow process).
FIG. 6 is a schematic configuration diagram of the inside of the clean booth 8 as viewed from the downstream side of the member 31 in the transfer direction.

The clean booth 8 has a floor 41, a ceiling 43 facing the floor 41 in the vertical direction, and a pair of walls facing the width direction perpendicular to the transfer direction of the member 31. 42.
On the floor 41, the conveyor 18 is installed at a distance from the pair of walls 42. The member 31 is supported by the carriage 19 and is transported in the clean booth 8 by a so-called vertical feed system in which the front portion is in the transport direction.

In the clean booth 8, an arch-shaped air pipe 29 is laid so as to surround the member 31 to be transferred. The air pipe 29 is provided with a plurality of air blowers 44 as air injection means for injecting air into the clean booth 8.
As the air blower 44, preferably, a static elimination blower including an electrostatic sensor or the like capable of measuring the charge amount on the surface of the member 31 to be transferred is used. If the air blower 44 is a static elimination blower, it is possible to suppress the dust removed from the member 31 from adhering to the member 31 again in the air blowing process.

In addition, a plurality (five in FIG. 6) of air blowers 44 are arranged on the air pipe 29 on a cross section that crosses the transfer direction at a substantially right angle. Each air blower 44 is formed with a plurality (four in FIG. 6) of injection ports 45 for injecting air so as to face the inside of the clean booth 8.
A pipe 47 is connected to the air pipe 29. The piping 47 communicates with the air piping 29 and also communicates with an air supply device such as an air compressor (not shown). A valve 46 for opening and closing the supply of air is provided in the middle of the pipe 47.

In the air blowing step, air is blown from above and from both sides of the entire member 31 transported on the conveyor 18 by injecting air from the injection port 45 of each air blower 44 with the valve 46 opened. . Thereby, for example, even when dust or the like has adhered to the member 31 before the intermediate coating step, the dust can be removed.
The condition of the air blowing treatment is such that the air injection pressure is a pressure that maintains the shape of the sealing material applied to the member 31, specifically, the gauge pressure is, for example, 0.05 to 0.3 MPa, preferably Is 0.05 to 0.1 MPa.

  In the air blowing process, after the air blowing process by the air blower 44, for example, a manual air blowing process may be performed on a predetermined portion of the member 31. Examples of the predetermined portion subjected to the air blowing process include a portion processed in a process upstream of the air blowing process, specifically, a part where the sealing material in the member 31 is applied. By performing the manual air blowing process, even if the part where the degree of dust adheres to the surface of the member 31 is large and small, the air blowing process is partially performed on the part where the degree is large. The coating quality of the intermediate coating film 33 and the top coating film 34 can be improved.

  In the air blowing process, the clean booth 8 is preferably humidified. Specifically, although it varies depending on the room temperature of the clean booth 8, it is preferably humidified so that the relative humidity is 50 to 80% when the room temperature is 25 to 30 ° C., for example, to 60 to 75%. More preferably, it is humidified. Moreover, it is preferable that it is humidified so that it may become 50-80% of relative humidity when indoor temperature is 18-25 degreeC, and it is still more preferable that it is humidified so that it may become 60-75%.

As a method for humidifying the inside of the clean booth 8, for example, the above-described humidification method may be mentioned.
In the cleaning booth 8, in addition to the process, for example, a wiping operation of wiping the surface of the member 31 (excluding the portion coated with the sealing material) with varnish gauze is performed.
Next, in the intermediate coating booth 9 and the top coating booth 10, wet-on-wet coating in which the intermediate coating material and the top coating material are continuously applied to the member 31 that has been subjected to the air blowing process is executed.

In wet-on-wet coating, first, intermediate coating is performed at the intermediate coating booth 9 (intermediate coating process).
An aqueous intermediate coating (intermediate aqueous coating) used for the intermediate coating is not particularly limited, and for example, an aqueous coating containing a water-soluble or water-dispersible resin component, a curing agent, and a pigment is used.

Examples of the resin component include an aqueous resin similar to the aqueous resin contained in the electrodeposition water-based paint, and preferably a polyester resin.
It does not restrict | limit especially as a hardening | curing agent, The hardening | curing agent similar to the hardening | curing agent contained in the said electrodeposition water-based coating material is mentioned.
The pigment is not particularly limited, and examples thereof include known color pigments. Specifically, for example, titanium dioxide, zinc oxide, basic lead sulfate, calcium leadate, zinc phosphate, aluminum phosphate, zinc molybdate, calcium molybdate, bitumen, ultramarine blue, cobalt blue, copper phthalocyanine blue, indium Dunslon Blue, Yellow Lead, Synthetic Yellow Iron Oxide, Transparent Bengal (Yellow), Bismuth Vanadate, Titanium Yellow, Zinc Yellow (Zinc Yellow), Strontium Chromate, Lead Cyanamide, Monoazo Yellow, Monoazo Yellow, Disazo, Monoazo Yellow, Iso Indolinone yellow, metal complex salt azo yellow, quinophthalone yellow, isoindoline yellow, benzimidazolone yellow, bengara, transparent bengara (red), red lead, monoazo red, monoazo red, unsubstituted quinacridone red, azo lake (Mn salt), ki Cridon Magenta, Ansanthrone Orange, Dianthraquinonyl Red, Perylene Maroon, Quinacridone Magenta, Perylene Red, Diketopyrrolopyrrole Chromium Vermilion, Basic Lead Chromate, Chromium Oxide, Chlorinated Phthalocyanine Green, Brominated Phthalocyanine Green, Examples include pyrazolone orange, benzimidazolone orange, dioxazine violet, and perylene violet. These can be used alone or in combination of two or more.

Further, the intermediate water-based paint preferably contains a catalyst such as a blocking agent dissociation catalyst or an acid catalyst in order to promote the crosslinking reaction by the curing agent.
The dissociation catalyst for the blocking agent is not particularly limited. For example, tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanote), dioctyltin diacetate, dibutyltin dilaurate , Organic metal compounds such as dibutyltin oxide, monobutyltin trioctate, lead 2-ethylhexinate and zinc octylate. These can be used alone or in combination of two or more.

Examples of the acid catalyst include phosphoric acid-based and sulfonic acid-based acid catalysts. These can be used alone or in combination of two or more.
In addition, in the intermediate coating water-based paint, if necessary, a light interference pigment, an extender pigment, a dispersant, an anti-settling agent, an organic solvent, a reaction accelerator (such as an organic tin compound), an antifoaming agent, a thickener, Known additives such as a rust inhibitor, an ultraviolet absorber, and a surface conditioner can be appropriately blended.

And each said component is mix | blended with water by a well-known method, and the solid content density | concentration is 40 to 60 weight%, for example, Preferably it is 45 to 50 weight by water-soluble or water-dispersing a resin component, for example. The intermediate water-based paint is prepared so as to be%.
The method for coating the intermediate water-based paint prepared as described above is not particularly limited, and examples thereof include an air spray method, an airless spray method, and an electrostatic coating method. Among these, Preferably, the electrostatic coating method is mentioned, Specifically, the electrostatic coating method (bell coating method) using a bell coating machine is mentioned.

The coating conditions of the bell coating method are, for example, a bell rotation speed of 20000 to 35000 min ⁻¹ , a shaving air pressure of 0.5 to 3.5 kg / cm ² , a gun distance of 20 to 30 cm, and a discharge amount. Is 150 to 350 mL.
In the intermediate coating process, the interior coating booth 9 is humidified. Specifically, although it varies depending on the room temperature of the intermediate coating booth 9, for example, when the room temperature is 25 to 30 ° C., the humidification is performed so that the relative humidity is 50 to 80%, and 60 to 75%. It is preferable to be humidified. Moreover, it is humidified so that it may become 50-80% of relative humidity when indoor temperature is 18-25 degreeC, and it is preferable to be humidified so that it may become 60-75%.

Examples of the method for humidifying the interior coating booth 9 include the above-described humidification method and a humidification method using a shower or direct steam installed in an air conditioner.
By applying the intermediate water-based paint on the undercoat film 32, a wet film (intercoat film 33) is formed on the surface of the undercoat film 32.
Next, the intermediate coated film 33 is overcoated in the top coating booth 10 without drying the intermediate coated film 33 with a drying furnace or the like (overcoating step).

The top coating booth 10 is divided into a base coating booth 16 and a clear coating booth 17 disposed downstream of the base coating booth 16. In the top coating process, first, base coating is performed with a water-based paint at the base coating booth 16 (base coating process).
The water-based paint (base water-based paint) used for the base coating is not particularly limited, and for example, a water-based paint containing a water-soluble or water-dispersible resin component, a curing agent, and a pigment is used.

Examples of the resin component include an aqueous resin similar to the aqueous resin contained in the electrodeposition water-based paint, and preferably an acrylic resin, a polyester resin, a melamen resin, and a polyurethane resin.
It does not restrict | limit especially as a hardening | curing agent, The hardening | curing agent similar to the hardening | curing agent contained in the said electrodeposition water-based coating material is mentioned.

Examples of the pigment include color pigments contained in the intermediate water-based paint, and metallic pigments such as aluminum powder, flaky aluminum oxide, pearl mica, and flaky mica. These can be used alone or in combination of two or more. By using a metallic pigment, a metallic or pearly coating film can be formed.
The blending ratio of the pigment is, for example, a blending ratio such that the base coating film 35 formed by the base coating has transparency and the color of the intermediate coating film 33 can be visually recognized through the base coating film 35.

In addition, the base water-based paint includes a light interference pigment, an extender pigment, a dispersant, an anti-settling agent, an organic solvent, a reaction accelerator (such as an organic tin compound), an antifoaming agent, a thickener, Known additives such as a rust inhibitor, an ultraviolet absorber, and a surface conditioner can be appropriately blended.
And each said component is mix | blended with water by a well-known method, and the solid content density | concentration is 15-30 weight%, for example, Preferably it is 20-25 weight by water-soluble or water-dispersing a resin component, for example. The base water-based paint is prepared so as to be%.

The coating method of the base aqueous paint prepared as described above is not particularly limited, and examples thereof include an air spray method, an airless spray method, and an electrostatic coating method. Among these, Preferably, the electrostatic coating method is mentioned, Specifically, the electrostatic coating method (bell coating method) using a bell coating machine is mentioned.
The coating conditions by the bell coating method are, for example, a bell rotation speed of 20000 to 35000 min ⁻¹ , a shaving air pressure of 0.5 to 3.5 kg / cm ² , a gun distance of 20 to 30 cm, and a discharge amount. Is 150 to 350 mL.

Next, clear painting is performed in the clear painting booth 17 (clear painting process).
The paint used for clear coating (clear paint) is not particularly limited, and for example, a known clear paint is used, and a paint containing a resin component and a crosslinking agent can be used.
Examples of the resin component include acrylic resin, polyester resin, alkyd resin, urethane resin, and epoxy resin.

Examples of the crosslinking agent include block polyisocyanate, melamine resin, urea resin, and the like. These can be used alone or in combination of two or more.
And each said component is mix | blended by a well-known method with an organic solvent or water, and the solid content density | concentration is 50 to 70 weight%, for example, Preferably it is 55 to 60 weight by dissolving or disperse | distributing a resin component. A clear paint is prepared so as to be%.

In addition, the clear paint has a base color pigment, a metallic pigment, a light interference pigment, an extender pigment, a dispersant, an anti-settling agent, an organic solvent, a reaction accelerator (as long as it does not hinder its transparency, if necessary. For example, known additives such as an organic tin compound, an antifoaming agent, a thickening agent, a rust preventive agent, an ultraviolet absorber, and a surface conditioner can be appropriately blended.
The method for applying the clear paint prepared as described above is not particularly limited, and examples thereof include an air spray method, an airless spray method, and an electrostatic coating method. Among these, Preferably, the electrostatic coating method is mentioned, Specifically, the electrostatic coating method (bell coating method) using a bell coating machine is mentioned.

The coating conditions of the bell coating method are, for example, a bell rotation speed of 20000 to 35000 min ⁻¹ , a shaving air pressure of 0.5 to 3.5 kg / cm ² , a gun distance of 20 to 30 cm, and a discharge amount. Is 150 to 350 mL.
In the base coating process and / or the clear coating process, the base coating booth 16 and / or the clear coating booth 17 are humidified. Specifically, although it varies depending on the room temperature of the base painting booth 16 and / or the clear painting booth 17, for example, it is humidified so that the relative humidity is 50 to 80% when the room temperature is 25 to 30 ° C. It is preferable to be humidified so as to be 60 to 75%. Moreover, it is humidified so that it may become 50-80% of relative humidity when indoor temperature is 18-25 degreeC, and it is preferable to be humidified so that it may become 60-75%.

Examples of the method of humidifying the interior of the base coating booth 16 and / or the clear coating booth 17 include the above-described humidifying method and a humidifying method using a shower or direct steam installed in an air conditioner.
Then, the base aqueous paint is applied onto the intermediate coating film 33, and further, the clear coating is applied onto the base aqueous paint, whereby the base coating film 35 and the clear coating film 36 are laminated on the surface of the intermediate coating film 33. A wet laminated film (top coat film 34) is formed.

After the top coating step, the top coated member 31 is dried in the top coating drying furnace 11 (top coating drying step).
As the top coat drying furnace 11 used in the top coat drying process, for example, a known drying furnace capable of drying the material to be dried by a heating method such as hot air heating, infrared heating, high frequency heating or the like is used.

  For example, in the case of hot air drying, the condition of the top coat drying is such that the hot air blowing temperature is, for example, 90 to 170 ° C, preferably 100 to 160 ° C. Moreover, the blowing speed of hot air is 10-15 m / s, for example. Moreover, the wind speed in the coating surface (surface of the member 31) of a hot air is 2-5 m / s, for example. The distance from the hot air outlet to the surface to be coated is, for example, 30 to 80 cm. Furthermore, the heating time is, for example, 20 to 30 minutes.

Moreover, the temperature in the top coat drying furnace 11 is 80-170 degreeC, for example, Preferably, it is 90-150 degreeC.
Then, by performing the top coat drying step, the intermediate water-based paint, the base water-based paint and the clear paint applied to the member 31 are dried, and the intermediate coat film 33 and the base in the dry state are formed on the surface of the undercoat film 32. A laminated film composed of the coating film 35 and the clear coating film 36 is formed, and the sealing material applied to the member 31 is dried and cured.

  The film thickness of the intermediate coating film 33 to be formed is, for example, 10 to 35 μm, preferably 15 to 30 μm, and more preferably 20 to 25 μm. Moreover, the film thickness of the base coating film 35 is 17-20 micrometers, for example, Preferably, it is 10-20 micrometers, More preferably, it is 13-17 micrometers. Furthermore, the film thickness of the clear coating film 36 is, for example, 10 to 45 μm, preferably 20 to 40 μm, and more preferably 25 to 35 μm.

Next, the overcoated member 31 is finally inspected in the final inspection booth 12 (final inspection step).
In the final inspection process, it is inspected whether the coating quality of the member 31 satisfies a predetermined standard, for example, whether the top coating film 34 has defects such as blisters or sagging (final inspection process).
After the final inspection process, the member 31 is transferred to an assembly process for assembling parts such as an engine and a sheet, and the coating process is completed.

  As described above, according to the coating method performed in this coating line, after the sealer coating step of coating the sealing material on a predetermined portion of the member 31, the wet sealing material is not dried by a drying furnace or the like. That is, the sealing material drying process for drying the sealing material is omitted, the UBC process, the air blowing process, the intermediate coating process, and the top coating process are performed, and then the top coating drying process is performed. By performing the top coating drying step, a laminated film composed of the intermediate coating film 33, the base coating film 35, and the clear coating film 36 in a dry state is formed on the surface of the primer coating film 32, and applied to the member 31. The sealant is dried and hardened.

  Therefore, the installation of a sealer drying furnace for drying the sealing material can be omitted, and a two-drying furnace coating line having only two drying furnaces (electrodeposition drying furnace 4 and topcoat drying furnace 11) is constructed. Can do. As a result, the energy required to operate the sealer drying furnace can be reduced, so that the energy consumed in the painting line can be reduced. In addition, by omitting the installation of the sealer drying furnace, the space required for the construction of the painting line can be reduced.

  Further, in the process executed after the electrodeposition drying process and before the top coating drying process, specifically, in the sealer coating process, the UBC process, the air blowing process, the intermediate coating process, and the top coating process, the coating line has a room temperature of 25, for example. Humidification is performed so that the relative humidity is 60 to 70% when the temperature is ˜35 ° C., and the relative humidity is 60 to 70% when the room temperature is 5 to 15 ° C. In addition, after the electrodeposition drying process, before the top coating drying process, a space where the member 31 is fastened, specifically, a coating line is also formed in the first storage space (not shown) and the second storage space (not shown), It is humidified as above.

  Therefore, the dust can be effectively lowered by the moisture contained in the atmosphere through these steps executed after the electrodeposition drying step, so that scattering of the dust into the furnace can be suppressed. Therefore, adhesion of dust to the surface of the undercoat coating film 32 formed by the electrodeposition drying process can be suppressed. As a result, it is possible to prevent the intermediate coating film 33 and the top coating film 34 from being uneven, and to suppress coating defects.

  In the electrodeposition drying step, first, in the preliminary drying zone 13, hot air is blown from the outlet 24 located on the outer side in the width direction of the member 31 to be transferred along the side surface of the member 31. Hot air is blown and hot air is blown to the inner surface of the member 31 through an opening formed on the side surface (preheating step). Next, in the first drying zone 14, hot air is blown onto the side surface and the inner surface of the member 31 in the same manner as in the preheating step (first heating step).

In the preheating step and the first heating step, hot air is blown onto the side surface and the inner surface of the member 31, so that the hot air does not reach or reaches the floor 22 of the electrodeposition drying furnace 4, but the speed is reduced. . Therefore, for example, even if dust adheres to the floor 22 or the like, the dust can be prevented from scattering into the furnace.
And after a 1st heating process, in the 2nd drying zone 15, a hot air is blown on the bottom face of the member 31 by blowing a hot air from the blower outlet 26 located in the width direction outer side lower side of the member 31 (2nd heating). Process).

  Therefore, the hot air reflected from the bottom surface of the member 31 may be blown onto the floor 22 at a speed higher than the speed of the hot air reaching the floor 22 in the first drying zone 14 or the like. Therefore, dust adhering to the floor 22 may be scattered into the atmosphere. However, since the surface layer of the water-based paint film electrodeposited on the member 31 can be formed by the preheating step and the first heating step before drying in the second drying zone 15, dust is deposited in the furnace. Even if it is scattered, the dust can be prevented from coming into close contact with the member 31. As a result, the coating failure of the undercoat coating film 32 can be suppressed, and furthermore, the coating failure of the intermediate coating film 33 and the top coating film 34 formed on the undercoat coating film 32 can be suppressed.

Further, a preliminary heating step and a first heating step are performed in which hot air is blown onto the side surface and the inner surface of the member 31 to heat the member 31, and further, a second heating step in which hot air is blown onto the bottom surface of the member 31 to heat the member 31. Therefore, the entire member 31 can be heated uniformly. As a result, the undercoat coating film 32 can be uniformly dried as a whole.
Further, stepwise in order of preheating step (hot air blowing temperature: 70 to 110 ° C.) → first heating step (hot air blowing temperature: 110 to 150 ° C.) → second heating step (hot air blowing temperature: 130 to 180 ° C.) Since the blowing temperature of the hot air is increased, the member 31 can be heated stepwise. As a result, the water contained in the water-based paint can be gradually evaporated, so that problems such as sagging and bumping repelling caused by the water contained in the water-based paint bumping can be suppressed. As a result, the coating failure of the undercoat coating film 32 can be suppressed, and furthermore, the coating failure of the intermediate coating film 33 and the top coating film 34 formed on the undercoat coating film 32 can be suppressed.

  Further, in the air blowing process executed after the sealer coating process, air is blown against the member 31 transferred on the conveyor 18, so that, for example, dust or the like has adhered to the member 31 before the intermediate coating process. But the dust can be removed. Furthermore, since the air is injected at a gauge pressure that holds the shape of the sealing material applied to the member 31, specifically, for example, 0.05 to 0.1 MPa, deformation of the sealing material can be prevented, and the sealing Generation of irregularities on the surface of the intermediate coating film 33 and the top coating film 34 formed on the material can be suppressed. As a result, the coating failure of the intermediate coating film 33 and the top coating film 34 can be suppressed.

The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.
For example, in the above-described embodiment, in the electrodeposition drying furnace 4, the member 31 is heated while being transferred by the vertical feeding method. For example, the member 31 has a so-called lateral direction in which the side portion is the transfer direction. It may be heated while being transferred by a feeding method.

Further, in the preliminary drying zone 13, the first drying zone 14, and the second drying zone 15, a dark red panel is installed on the wall 28, and this dark red panel is heated by hot air and radiated from the heated dark red panel. The member 31 may be heated by radiant heat.
Although not described in detail in the above-described embodiment, it is preferable that the coating line is humidified even in a place where various booths are not provided between the electrodeposition drying furnace 4 and the topcoat drying furnace 11. . Thereby, it is possible to suppress the dust from adhering to the member 31 during transfer on the conveyor 18.

It is process drawing which shows one Embodiment of the coating method of this invention. It is a schematic sectional drawing which shows the layer structure of the coating film formed on the member which comprises a motor vehicle body. It is the schematic block diagram which looked at the inside of a preliminary drying zone from the conveyance direction downstream side of a member. It is the schematic block diagram which looked at the inside of the 1st drying zone from the transfer direction downstream of a member. It is the schematic block diagram which looked at the inside of the 2nd drying zone from the transfer direction downstream of a member. It is the schematic block diagram which looked at the inside of a clean booth from the transfer direction downstream of a member.

Explanation of symbols

4 Electrodeposition Furnace 6 Sealing Material Application Booth 9 Intermediate Coating Application Booth 10 Top Coating Application Booth 14 First Drying Zone 15 Second Drying Zone 31 Member 32 Undercoat Film 33 Intermediate Coating Film 34 Topcoat Film 44 Air Blower

Claims (3)

A painting method performed on a painting line for painting a member constituting an automobile body by a flow work,
An electrodeposition drying step for drying the electrodeposited member;
After the electrodeposition drying step, an application step of applying a sealing material to a predetermined portion of the member;
An intermediate coating step in which the member to which the sealing material is applied is intermediate coated with a water-based paint;
An overcoating step of overcoating the intermediate-coated member,
The coating method, wherein the coating line is humidified in the coating step, the intermediate coating step, and the top coating step. The coating line is provided with a drying furnace in the electrodeposition drying step,
The drying furnace is arranged on the downstream side of the first drying zone for applying heat from above to the member transferred on the coating line, and hot air is applied to the member from below. The coating method according to claim 1, further comprising: a second drying zone that supplies water.   In the coating line, there is air injection means for injecting air so that the shape of the sealing material is maintained with respect to the member transferred on the coating line between the coating process and the intermediate coating process. The coating method according to claim 1, wherein the coating method is provided.

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