JPH0417109B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to the coating of automobile bodies, casings of home appliances, metal materials used for various purposes, etc. Related to drying treatment of water-soluble paint.

[Conventional technology]

Conventionally, when drying oil-based paints using volatile solvents such as thinner, the object to be coated with oil-based paints was simply left in an atmosphere of room temperature and humidity for about 10 minutes, as the solvents in these oil-based paints evaporated quickly. However, when using water-soluble paints, the evaporation rate of the water contained in them is considerably slower than that of volatile solvents such as thinner, so some kind of forced drying process is required to maintain efficiency. I was getting used to it.

100% for water-soluble paint after application.
In so-called high-temperature heating drying, such as contacting with high-temperature hot air of ~250℃ or applying radiant heating,
Problems such as the drying of the surface of the applied water-soluble paint film progresses, leading to a decline in the quality of the paint, and the need for a long cooling process after high-temperature heating, which actually reduces efficiency. Derived.

Therefore, by bringing low-humidity air into contact with the water-soluble paint film in a warm atmosphere, the evaporation of the water contained in the paint film is promoted. A technique has been proposed that efficiently reduces the drying distance (see, for example, Japanese Patent Application Laid-open No. 52-98748).

[Problem to be solved by the invention]

However, even when drying water-soluble paints using low-humidity air as described above, there is a problem in that maintaining a warm atmosphere (especially in winter) and generating low-humidity air by dehumidifying each require a large amount of energy.

An object of the present invention is to reduce the energy required for drying water-soluble paint using low-humidity air by adopting a rational low-humidity air supply form.

[Means to solve the problem]

The characteristic structure of the coating method according to the present invention is that the air taken out from the drying chamber is dehumidified by an adsorption/desorption type dehumidification device that regenerates the adsorbent using high-temperature regenerating air, and the dehumidified air is circulated and supplied to the drying chamber. The purpose of this method is to dry the water-soluble wild material applied to the object in the drying chamber, and its functions and effects are as follows.

[Function] In other words, the moisture that evaporates from the water-soluble paint film on the object to be coated in the drying chamber is discharged from the drying chamber along with the air taken out from the drying chamber,
By supplying low-humidity air dehumidified by a dehumidifying device to the drying room, the evaporation of water contained in the water-soluble paint film is effectively promoted, thereby reducing the water-soluble paint applied to the object. Efficient drying process.

Then, as low-humidity air to be supplied to the drying room, the air taken out from the drying room is dehumidified by a dehumidifying device and is circulated and supplied to the drying room. Use effectively to maintain a warm atmosphere for promotion.

In addition, as a dehumidifying device, there is an adsorption/desorption type that regenerates the adsorbent using high-temperature regeneration air, in other words, the temperature of the air to be dehumidified rises due to the heat transfer from the high-temperature regeneration air as the adsorbent dehumidifies due to the moisture absorption action of the adsorbent. By using a dehumidifying device in the system, its temperature raising function can be used more effectively to maintain a warm atmosphere in dry and humid conditions.

〔Effect of the invention〕

As a result of the above actions, it is possible to effectively save energy and reduce running costs in drying processing that uses low-humidity air, which has the advantage of efficiently drying water-soluble paints while maintaining high coating quality. I ended up getting it.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

Figure 1 shows a series of processing steps in a painting line for automobile bodies.In this example, chemical conversion treatment for the object to be coated, water washing treatment, undercoating by electrodeposition, intermediate coating of hard film forming paint by spraying, and intermediate coating. The formed hard film is polished, top-coated by spraying, and finished-coated with a glossy film-forming paint by spraying, in that order.

In addition, after washing with water, a drying process using hot air is carried out, after each of the base coat and intermediate coat, a baking process using hot air is carried out, after the top coat is a drying process for the finishing coat, and after the finishing coat is a final drying process using hot air. A baking process is performed respectively.

After the draining and drying treatment and each baking treatment, there is a cooling step in which the object to be coated, which has been heated to a high temperature by hot air, is naturally cooled so as not to interfere with the next coating.

Since the coating thickness of the gloss-forming paint in the finish coat is thin, baking treatment for the top coat paint is performed together with the finish coat paint in the final baking treatment after the finish coat, and in the drying process after the top coat, the applied top coat A simple drying process to bring the paint to a state that does not interfere with the final coating is carried out in a warm atmosphere (for example, at 30 to 50°C as shown in Figure 3 below).
(in a moderate atmosphere).

In other words, in the drying process after topcoating, by simply drying in a warm atmosphere, there is no need for a cooling process between topcoat and finishing, and the cooling process is extremely short compared to other cooling processes. This will reduce the overall time required on the painting line, improve painting efficiency,
In addition, efforts are being made to shorten the required line length.

Water-soluble paints with a low content of volatile solvents such as thinner are used for the base coat, intermediate coat for forming a hard film, and top coat, while for the finish coat for forming a glossy film, Oil-based paints with a high content of volatile solvents such as thinner are used.

In the past, oil-based paints containing a high content of volatile solvents such as thinner were also used for top coats because water-soluble paints could not pass through the top coat due to film quality and so-called dripping. However, in recent years, water-soluble paints such as those with high thixotropy have been developed, and water-soluble paints are used as top coats. By reducing the overall consumption of solvents, we are trying to prevent pollution caused by these volatile solvents.

Figure 2 shows the equipment configuration for drying the top coat after application in a warm atmosphere. 1 is formed, and an external circulation air passage 2 is connected to the drying chamber 1,
A rotary type dehumidifier 3 is interposed in the middle of the circulation air path 2.

In other words, with the coated object A placed in the drying chamber 1, circulating air with low absolute humidity dehumidified by the dehumidifier 3 is brought into contact with the coated top coat, thereby reducing the drying temperature of the top coat. The evaporation of the contained moisture is effectively promoted to dry the top coat.

In the rotary type dehumidification device 3, the drying chamber 1
an adsorption zone a through which circulating air from the burner 4 passes, and a desorption zone b through which high-temperature regeneration air generated by the burner 4 passes through.
A rotating roller 3 filled with an adsorbent X that absorbs moisture from the circulating air from the drying chamber 1 and is renewed by the desorbing action of the high-temperature regenerated air.
A rotates so that the packed adsorbent X is alternately located in the adsorption zone a and the desorption zone b.

In the figure, 5 is a fan for supplying high-temperature regeneration air, 6 is a circulation fan, 7 is a bypass air passage for adjusting the amount of air passing through the adsorption area, and 8 is a fan for bypass circulation.

Note that FIG. 3 is a psychrometric diagram showing changes in the state of the circulating air, with solid lines showing changes in the state in the summer and broken lines showing changes in the state in the winter. Also, the points , , in FIG. 3 indicate the states at the positions of the same symbols in FIG. 2 .

In order to bring the dehumidifying circulating air into contact with the applied top coat paint in the drying chamber 1, a plurality of blowing chambers 10 equipped with 9 groups of dehumidifying circulating air blowing nozzles are placed at a preparation position away from the object A (double-dashed line in the figure). ) and a processing position (indicated by a solid line in the figure) where each nozzle 9 approaches the surface to which the top coat is applied by the same distance l. Each nozzle 9 in processing position relative to the surface
By uniformly blowing dehumidified circulating air from the top coat, the top coat is dried evenly.

[Another example]

Next, another embodiment of the present invention will be described.

Various improvements can be made to the configuration of the device in which circulating air dehumidified by the adsorption/desorption type dehumidification device 3 is supplied to the drying chamber 1 and brought into contact with the water-soluble paint coated on the object A to be coated.

The present invention is applicable not only to the drying treatment of water-soluble paints used for top coats but also intermediate coats and base coats.

The objects to be painted on the painting line to which the present invention is applied are not limited.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams explaining embodiments of the present invention, with Figure 1 being a flow sheet for a painting line, Figure 2 being a diagram showing drying treatment equipment, and Figure 3 being a diagram showing circulating air for drying. It is a psychrometric diagram showing state changes.

Claims (1)

[Claims] 1. The air taken out from the drying chamber 1 is dehumidified by an adsorption/desorption type dehumidifier 3 that regenerates the adsorbent X using high-temperature regeneration air, and the dehumidified air is circulated and supplied to the drying chamber 1. A coating method that dries the water-soluble paint applied to the object A in 1.