JP3706281B2 - Painting equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating facility for applying a water-based paint to the surface of an object to be transported by a conveyor and then repeatedly applying a different paint on the coating film of the water-based paint.
[0002]
[Prior art]
Recently, the use of water-based paints has been increasing over a wide range of applications as organic solvent emission regulations have become stricter. In particular, in the field of automobile painting, in order to clear organic solvent emission regulations, a shift from conventional coating with organic solvent-based paints to painting using water-based paints is being attempted.
[0003]
For automobile painting, a high-quality coating film is required, but water-soluble baked paints made by water-solubilizing various synthetic resins to be baked and dried, for example, an aluminum acrylic type baked at 150 ° C, Attempts have been made to use it for intermediate coating and top coating of automobile bodies because they are transparent, have little discoloration, and have excellent weather resistance.
[0004]
By the way, a conventional automobile painting facility that performs, for example, a top coating of an automobile body, includes a coating zone in the previous stage in which a base coat for imparting aesthetics is applied to the surface of the automobile body conveyed by a conveyor with an organic solvent-based metallic paint, and the base coat Generally, a base coat post-correction coating zone and a setting zone of about 20m in length are provided between the rear coating zone where a clear coating having a protective function against external factors is applied with a transparent paint. Is.
[0005]
In this setting zone, the base coat paint film applied to the surface of the automobile body in the previous paint zone is left at room temperature, and the organic solvent in the paint film is evaporated to an appropriate degree, thereby providing a base coat and clear coat. When baking and drying the top coat film, the base coat film is softened and smoothed at the same time, and at the same time, bubbles are generated in the base coat film due to rapid evaporation of the organic solvent. It is provided to prevent the occurrence of coating defects such as.
[0006]
[Problems to be solved by the invention]
However, when water-based paint is used as the base coat paint in the existing automobile painting equipment as described above, the water content of the water-based paint remains excessively in the base coat film that is left at room temperature in the setting zone. Since the clear coat paint will be overcoated on the coating film, the moisture in the base coat film may rapidly evaporate during baking and drying, which may cause coating defects such as sagging, sagging, and armpits. There is.
[0007]
That is, the water-based paint is usually heated after coating to evaporate water for diluting the water-soluble resin and the water-soluble resin and a co-solvent having a water coupling effect, and then the water-based paint is made dense by a crosslinking reaction or the like. When a water-based paint is used as a base coat paint for top coating in an existing automobile painting facility, the water-based paint film is left at room temperature without being heated. Since the clear coat paint is applied repeatedly without moisture evaporating, it is inevitable that defects such as wrinkles occur during baking and drying.
[0008]
Therefore, the applicant applies an infrared heater 20 and a hot air heating device 21 as shown in FIG. 3 in the setting zone of an existing automobile painting facility, and is applied to the surface of the automobile body 22 conveyed by a conveyor. An attempt was made to evaporate the water in the paint film by heating the paint film of the water-based paint to a high temperature.
[0009]
According to this experiment, the automobile body 22 that is usually conveyed at a conveyor speed of about 5 m / min is first heated by the radiant heat of the infrared heater 20 for about 1 minute, so that the surface temperature of the automobile body 22 is about 60%. The surface temperature of about 60 ° C. was kept for about 3 minutes with hot air of 80 ° C. blown from the hot air blowing nozzle 23 of the hot air heating device 21 at a speed of 8 m / s. It was confirmed that the water content of the water evaporates to such an extent that it does not generate aside during baking and drying.
[0010]
However, in order to keep the surface temperature of the automobile body 22 at a high temperature of 60 ° C. with hot air of 80 ° C., it is necessary to provide a heat insulating wall or the like along the conveyance path of the automobile body 22 so as not to escape the hot air. There is a construction cost for that.
[0011]
Also, if it takes about 4 minutes to evaporate the water in the coating film with the infrared heater 20 and the hot air heating device 21 as described above, the automobile body 22 conveyed at a speed of 5 m per minute moves about 20 m in the meantime. If it is an existing painting facility, it will pass through the setting zone and move to a later painting zone where a clear coat is applied while maintaining a high surface temperature. For this reason, even if the possibility that the coating film of the water-based paint may cause defects such as aside is resolved, this time, the coating film of the clear coat paint to be overcoated on the coating film has defects such as rough skin due to high temperature. May occur.
[0012]
Therefore, as shown in FIG. 3, a cold air cooling device 24 is installed at the next stage of the hot air heating device 21, and 20 ° C. cold air blown at a speed of 8 m / s from the cold air blowing nozzle 25 of the cold air cooling device 24 is blown onto the surface of the automobile body 22. When an experiment to reduce the surface temperature was attempted, the surface temperature of the automobile body 22 heated to a high temperature of about 60 ° C. was reduced to about 1 to reduce the temperature of the clear coat to a level that did not cause skin roughness. It took about 30 minutes. Therefore, the cold air cooling device 24 requires an installation length of 7 m or more.
[0013]
However, since the infrared heater 20 and the hot air heating device 21 also require installation lengths of about 5 m and about 15 m, respectively, a setting zone of about 20 m or less provided in an existing automobile painting facility is used. There is no space for installing the cold air cooling device 24.
[0014]
In order to create an installation space for the cold air cooling device 24, the installation length of the infrared heater 20 and the hot air heating device 21 is shortened, and the installation length of the infrared heater 20 and the hot air heating device 21 is reduced accordingly. If you try to evaporate the water in the paint film of the water-based paint in a short time by increasing the heating temperature, the flow of the paint film due to the rapid evaporation of water and bubbles are generated, such as sagging, sagging, aside There is a high risk of defects.
[0015]
If the cooling temperature of the cold air cooling device 24 is lowered to shorten the installation length, the coating surface of the aqueous paint held at a high temperature by the hot air heating device 21 is rapidly cooled by the low temperature cold air, There is a risk of condensation on the surface and defects such as wrinkles.
[0016]
In view of the circumstances as described above, the present invention causes coating defects such as sagging, sagging, and armpits in a water-based paint film so that the paint can be applied with the water-based paint even in existing automobile painting equipment. Without vaporizing moisture in the paint film quickly, and avoiding coating defects such as rough skin due to high temperature in the paint film of another paint layered over the water paint film. This is a technical issue.
[0017]
[Means for Solving the Problems]
In order to solve the above-described problems, the coating equipment of the present invention is configured such that a coating zone of a previous stage in which a water-based paint is applied to the surface of an object to be transported by a conveyor, and a different paint is stacked on the coating film of the water-based paint. A heating device that heats and raises the temperature of an object coated with a water-based paint in the previous-stage paint zone and evaporates moisture in the coating film of the water-based paint between the coating zone of the latter-stage to be applied and the heating device The dry air dehumidified by the dehumidifier is blown at a high wind speed on the surface of the object heated in step 1, evaporating the water content of the water-based paint applied to the surface, and at the same time lowering the surface temperature of the object to be coated A coating film evaporation drying zone provided with a dry air spraying device is provided.
[0018]
According to the present invention, the water-based paint film applied to the surface of the object to be coated in the previous coating zone is first heated, and the moisture in the paint film begins to evaporate from the surface of the paint film. Next, the dry air dehumidified by the dehumidifier is blown onto the surface of the coating film at a high air speed, and the air in contact with the surface of the coating film is carried away one after another to replace the air with dry air having a low relative humidity. By generating the air flow, the evaporation of moisture from the surface of the coating film is promoted, and at the same time, the coating film is gradually cooled by the heat of vaporization caused by the evaporation of moisture.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a diagram showing an example of a painting facility according to the present invention, and FIG. 2 is a graph showing the effect of the present invention.
[0020]
The painting equipment of this example is an automobile painting equipment for applying a top coat to an automobile body, and a coating zone 2 in the previous stage for applying an aqueous metallic base coat to the surface of the automobile body 1 conveyed by a conveyor, and an upper part of the aqueous metallic base coat. The automobile body 1 coated with the water-based metallic paint in the former coating zone 2 is heated to increase the surface temperature of the automobile body 1 between the latter and the latter painting zone 3 where the transparent coating is applied to the transparent coating. The surface of the heating device 5 and the automobile body 1 heated and heated by the heating device 5 was sprayed with high-air-speed dry air that was dehumidified by the dehumidifying device 6 and supplied by the blower 7, and was applied to the surface. Evaporation drying zone of coating film provided with dry air spraying device 8 for lowering the surface temperature of automobile body 1 at the same time as evaporating water of water-based metallic paint It is provided.
[0021]
The heating device 5 heats the automobile body 1 conveyed at a speed of 5 m per minute from both sides of the conveying path for about 1 minute, and raises the surface temperature of the automobile body 1 to about 45 to 60 ° C. The infrared heater is used.
[0022]
The dry air blowing device 8 includes two front and rear air blowing ducts 9a and 9b arranged side by side along both sides of the conveyance path of the automobile body 1, and the air blowing ducts 9a and 9b are separated from each other by about 300 mm in front. A large number of air blowing nozzles 10 are provided for blowing dry air at a high wind speed toward the side surface of the automobile body 1 facing the vehicle body 1.
[0023]
The dehumidifier 6 is a cooling type dehumidifier that cools the processing air to a dew point temperature or less and condenses and removes water vapor in the air, or passes the processing air through a rotor to remove moisture in the air such as silica gel or activated alumina. An adsorption-type dehumidifying device that adsorbs to a rotor element made of a porous material can be used.
[0024]
The blower 7 supplies the dry air dehumidified by the dehumidifying device 6 to the air blowing ducts 9a and 9b of the dry air blowing device 8 through the air supply duct 11, and a variable speed fan that can freely adjust the supply amount of the dry air. Is used.
[0025]
The air supply duct 11 is a branch duct that distributes and supplies the dry air dehumidified by the dehumidifier 6 to the air blowing ducts 9a and 9b, and airflow adjustment dampers 12a and 12b are provided in the branched ducts, respectively. The air speed and air volume of the dry air blown to the surface of the automobile body 1 by the dry air blowing device 8 can be individually adjusted for each of the air blowing ducts 9a and 9b.
[0026]
Note that a post-correction coating zone 13 is attached to the front-side coating zone 2 on the carry-out side of the automobile body 1.
[0027]
Also, the air blowing ducts 9a and 9b of the dry air blowing device 8 have a total installation length of about 2 m so that they can be installed in a setting zone having a length of about 20 m provided in an existing painting facility. It is selected to be 15m or less.
[0028]
Thus, the coating film of the aqueous metallic paint applied to the surface of the automobile body 1 in the previous coating zone 2 is first heated to about 45-60 ° C. by the heating device 5 installed in the evaporation drying zone 4 of the coating film. When heated, the moisture in the coating begins to evaporate.
[0029]
Next, dry air prepared at a temperature of about 30 ° C. and a relative humidity of about 30% by the dehumidifying device 6 is applied to the coating film of the aqueous metallic paint heated by the heating device 5, and the air blowing duct 9 a of the dry air blowing device 8. , 9b is sprayed from a large number of air blowing nozzles 10 at a high wind speed of about 10 m / sec for about 3 minutes, and the evaporation of moisture in the coating film is promoted, and at the same time, the heat of vaporization when the moisture evaporates. Thus, the coating film is gradually cooled without causing coating defects such as wrinkles due to rapid cooling on the surface.
[0030]
As a result, the coating film of the water-based metallic paint applied to the surface of the automobile body 1 in the preceding coating zone 2 is applied to the clear coating for the clear coating in the subsequent coating zone 3 when the clear coating is applied repeatedly. To the extent that there is no risk of causing coating defects such as rough skin due to high temperature, and at the same time, there is no risk of causing coating defects such as sagging, sagging, and side during baking and drying. Water in the film evaporates moderately.
[0031]
According to an experiment, when a coating film of a water-based paint having a film thickness of about 15 μm and a non-volatile content NV = 25.5% by weight applied to the surface of the automobile body 1 is left at room temperature, 3 minutes have passed. While the NV value reaches only about 30% by weight, the coating film is heated by the heating device 5 for about 30 seconds and heated to about 48 ° C., and then the air blowing duct 9a, When dry air having a temperature of 30 ° C. and a relative humidity of 30% is blown from each air blowing nozzle 10 of 9b at a blowing wind speed of about 10 m / sec, the NV value at the lapse of 3 minutes is about 30% as shown by the solid line in the graph of FIG. It was confirmed that it reached 75% by weight. That is, according to the present invention, in just 3 minutes, the NV value of the coating film reaches the range of 75 to 80% by weight which is optimal for baking drying.
[0032]
Further, by using the experimental equipment of FIG. 3 which is a comparative example of the present invention, the coating film is heated by the infrared heater 20 for about 30 seconds to be raised to about 48 ° C., and then blown out from the hot air heating device 21 at 80 ° C. As a result of an experiment for further heating with hot air, the NV value after 3 minutes was about 77% by weight as shown by the broken line in the graph of FIG. Therefore, the dry air spraying device 8 according to the present invention is almost the same as the hot air heating device 21 in the effect of evaporating and drying the coating film of the water-based paint.
[0033]
Further, since the dry air spraying device 8 generates a high-speed air flow by dry air on the coating film surface of the water-based paint to evaporate moisture in the coating film, it is not necessary to surround the periphery with a heat insulating wall or the like. Since it is not a device for blowing hot hot air, the air blowing ducts 9a, 9b, the air blowing nozzle 10 and the like can be made of inexpensive plastic, and there is an advantage that the equipment cost can be reduced.
[0034]
Further, as in the embodiment, when the dry air blowing device 8 is constituted by a plurality of air blowing ducts 9a and 9b, for example, the supply air duct 11 is provided with an amount of dry air supplied from the dehumidifying device 6 to the air blowing duct 9a. The surface temperature of the automobile body 1 that is cooled by the dry air is slightly increased by reducing the air speed and the air volume of the dry air blown out from the air blowing nozzle 10 of the air blowing duct 9a. It is possible to optimally adjust the evaporation amount of moisture in the coating film by holding it.
[0035]
The heating device 5 is necessary for setting the NV value of the coating film of the water-based paint to 75 to 80% by weight optimum for baking and drying. A temperature of 30 ° C. for spraying a coating film of an aqueous paint having a film thickness of about 15 μm and an NV value of 25.5% by weight on the surface of the automobile body 1 with a dry air spraying device 8 without heating to 30 ° C. When evaporating and drying only with the dry air having a humidity of 30%, the NV value after 3 minutes reaches approximately 71%, but the NV value does not increase after that, and the NV value after 4 minutes also reaches approximately 71%. %.
[0036]
This is because the evaporation of the co-solvent blended in the water-based paint cannot be promoted only by spraying the high-velocity dry air without heating the water-based paint film. By evaporating the co-solvent in the coating film to some extent, the NV value of the coating film can be 75 to 80% by weight which is optimal for baking and drying within a few minutes.
[0037]
The heating device 5 is not limited to an infrared heater, and may be a hot air heating device that heats the automobile body 1 to be coated with hot air. The present invention can be applied not only to a coating facility for top coating, but also to a coating facility for intermediate coating. Also, not only in automobile painting equipment, but also in the former coating zone where water-based paint is applied to the surface of the object to be transported by the conveyor, and in the latter-stage painting zone where different paint is applied over the coating film of the aqueous paint. It can be applied to various painting facilities equipped with
[0038]
【The invention's effect】
According to the present invention, the coating film of the water-based paint applied to the surface of the object to be transported by the conveyor does not cause coating defects such as sagging, sagging, and side by high temperature, and it is superimposed on the coating film. The paint film of a different paint to be applied also has a very excellent effect that the paint film of the water-based paint can be quickly evaporated and dried without causing coating defects such as rough skin due to high temperature.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a painting facility according to the present invention.
FIG. 2 is a graph showing the effect of the present invention.
FIG. 3 is a diagram showing an experimental coating facility as a comparative example of the present invention.
[Explanation of symbols]
1 ... Auto body (Coating)
2... First coating zone 3... Next coating zone 4... Evaporation drying zone 5... Heating device 6. .... Dry air blowing device 9a ... Air blowing duct 9b ... Air blowing duct

Claims (3)

A former coating zone (2) for applying a water-based paint on the surface of the article (1) conveyed by the conveyor, and a subsequent coating zone (3) for applying another paint on the coating film of the aqueous paint. A heating device (5) for heating and elevating the temperature of the article (1) to which the water-based paint is applied in the previous coating zone (2) to evaporate water in the coating film of the water-based paint, Simultaneously evaporating moisture of the water-based paint applied to the surface of the object (1) heated by the heating device (5) by blowing dry air dehumidified by the dehumidifying device (6) at a high wind speed. A coating facility comprising a coating film evaporation drying zone (4) provided with a dry air spraying device (8) for lowering the surface temperature of the article (1). The coating equipment according to claim 1, wherein the heating device (5) is an infrared heater or a hot air heating device for heating and heating the article (1) to about 45 to 60 ° C. The coating equipment according to claim 1 or 2, wherein the dry air spraying device (8) is constituted by a plurality of air blowing ducts (9a, 9b) to which the dry air dehumidified by the dehumidifying device (6) is distributed and supplied. .

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