JPH0231864A - Method of painting by baking - Google Patents

Abstract

PURPOSE:To obtain the good adhesiveness and finish state of a paint and to allow painting by baking in a short period of time by heating an article with the paint from the counter paint applied surface side of the article body to paint the surface of the article body by baking. CONSTITUTION:The device is so constituted that the article 30 with the paint is heated from the counter paint applied surface 30b side and the article body 30A is heated up earlier than the coated film 32 applied thereon. As a result, the curing of the coated film 32 part starts from the inside layer part brought into contact with the article body 30A and thereafter, the heat is transferred to the surface layer part of the coated film 32 to cure the surface layer part. The surface of the coated film 32 is not cured yet even if a solvent such as thinner is incorporated into the coated film 32 and evaporates; therefore, the evaporated solvent is smoothly released from the surface of the coated film 32 into the atmosphere. Further, the temp. rising rate of the article body 30A exceeds the heating up rate of the coated film 32 part and the problem such as curing of the coated film 32 surface earlier than the inside layer part is obviated even if the article is heated to a high temp.

Description

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

(Prior art) Conventionally, when baking an article such as a die-cast motor cover, for example, a paint is applied to one side (surface) of the article, and then the article coated with the paint is dried naturally or in a low-temperature drying oven. The paint-coated article is pre-dried in a drying oven to evaporate solvents such as thinner contained in the paint, and then the article with the paint is heated from the outside of the painted surface of the article at high ambient temperature in a high-temperature drying oven to form a coating. I try to imprint it. In addition, in order to apply baking paint to the surface of an article, the temperature of the body of the article coated with paint must be 15-θ, although it depends on the type of paint used.
It is necessary to heat it until it reaches about 180°C.

By the way, if solvent (thinner) remains in the coating film of a pre-dried article with paint, the solvent will vaporize in the coating film when heated at high temperature, causing bubbles to form in the coating film. . If the air bubbles generated in the coating film are trapped in the coating film as described above, a problem arises in that the finished surface of the coating deteriorates and the yield of the product decreases. For this reason, in the past, after applying paint to the surface of an article, the article with the paint was allowed to dry naturally until a considerable amount of the solvent in the paint film evaporated, or it was pre-dried for a long time in a low-temperature drying oven. was.

(Problem to be Solved by the Invention) However, in the case where the paint-coated article is housed in a high-temperature drying oven in a high-temperature atmosphere for baking painting, it is difficult to store the paint-coated article in the high-temperature drying oven. At that point, the surface of the paint film is heated immediately, and before the temperature of the product body reaches the paint baking temperature (150-180'C), only the surface of the paint film quickly reaches the curing temperature, causing the paint to reach the hardening temperature on the product body. On the other hand, there was a problem in that adhesion was poor and defective products were more likely to be produced. Also, the higher the heating temperature (atmospheric temperature inside the drying oven), the faster the time for the product body to reach the paint baking temperature. The difference between the rate of temperature rise of the main body becomes large, and the above-mentioned problem that only the surface of the coating is cured quickly becomes noticeable. Therefore, in the past, the atmospheric temperature in the drying oven was set at 150 to [8], which is the paint baking temperature.
The temperature is set at around 0°C, and heating is performed slowly in the ambient temperature (so that the difference between the rate of temperature increase on the surface of the coating and the rate of temperature increase on the article itself does not become large). There is a problem that the time required for printing is long (about 20 minutes or more is required).

In addition, if the pre-drying of the painted article is insufficient, that is, if the paint film still contains a large amount of solvent, if the surface of the paint film is cured first, as described above, the paint film will be damaged. of the solvent is trapped in the form of bubbles in the coating film,
As mentioned above, the problem arises that the quality of the product is lowered and the yield of the product is lowered. In addition, in order to prevent air bubbles from forming in the coating film, it is necessary to sufficiently pre-dry the painted article before baking to minimize the solvent content in the coating film. If the pre-drying time is long, it will take a long time to complete the product after the paint is applied to the product itself, and if the product is manufactured in a continuous production system, there will be a problem that the amount of work in progress will increase. .

SUMMARY OF THE INVENTION Therefore, the present invention aims to propose a baking coating method that can improve the adhesion and finish of the paint and also allows baking coating to be done in a short time.

(Means for solving the problems) The present invention, as a means for solving the above problems,
The article is characterized in that the paint-coated article is coated with paint on one side of the article body to be baked and coated, and the paint is baked onto the surface of the article body by heating the article body from the opposite side of the article body to which the paint is applied using a heating device. It is said that

(Function) The present invention uses the above-mentioned means to heat an article coated with paint from the side opposite to the paint coated side, so that the temperature of the article body increases before the coating film applied to the article body. You will be able to tighten it. In this way, when the article body is heated before the coating film, the coating portion begins to harden from the inner layer portion that is in contact with the article body, and then heat is transferred to the surface layer portion of the coating film, causing the surface layer portion to harden. begins to harden.

Also, by heating from the side of the product body opposite to the paint coating, even if the paint film contains a solvent such as thinner and the solvent evaporates, the paint film surface will still be cured. This allows the vaporized solvent to be smoothly released from the coating surface into the atmosphere.

Furthermore, if the object is heated from the side opposite to the paint coating, the temperature rise rate of the object body will be faster than the temperature rise rate of the paint film part, so even if heated at high temperature, the paint film surface will be higher than the inner layer part of the paint film. There is no problem of curing first.

(Effects of the Invention) Therefore, according to the baking coating method of the present invention, by heating an article coated with paint from the opposite side of the article body to which the paint is applied, the temperature of the article body can always be raised before the coating film. This improves the adhesion of the paint to the surface of the product body, and even if the pre-drying of the paint-covered product is insufficient (even if a large amount of solvent remains in the paint film), the paint will not adhere to the surface after baking. No air bubbles remain in the coating film due to vaporized solvent, and the finish of the baked painted surface is good, making it possible to extremely reduce the incidence of defective products.

In addition, as mentioned above, it does not take much time to pre-dry an article with paint, and the baking time can be shortened by increasing the heating temperature during baking, so it is possible to shorten the baking time by applying the paint to the article itself. It has many benefits, such as being able to significantly shorten the time it takes to complete a product (complete baking) and being able to respond to urgent orders.

(Example) A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIGS. 1 and 2 show baking coatings suitable for carrying out the baking coating method of the present invention. An example of device Z is shown, and this device Z will first be described.

This baking coating device Z includes a base l, a heating device 10 mounted on the base I, an article holder 20 for holding an article 30 to be baked and coated, and an article holder 20 to hold the article 30. It is configured to include a heat shielding cover integral 26 that is placed over the outside of the article 30.

The base 1 is formed by connecting an upper plate 2 and a lower plate 3, each of which has a rectangular shape, with four connecting rods 8.about.8, vertically spaced apart from each other at appropriate intervals. A hole 4 for fitting the article holder 20 from above is formed in the upper plate 2 approximately at the center, and a hole 4 for inserting the article holder 20 from above is formed at approximately the center of the lower plate 3. An air intake lower is formed.

The heating device 10 includes an electric heater 12 and a fan 13 installed below the electric heater 12 in a cylindrical, vertically oriented exterior body It. The upper part of the exterior body 11 has a small diameter, and an annular step part 11a is formed at the lower end of the small diameter part. Further, an air outlet 15 is formed on the upper surface of the exterior body 11.

In this heating device IO, an exterior body 11 is installed and fixed on the lower plate 3 so as to surround an air intake lower. The heating device IO is configured to blow hot air upward from the air outlet 15 by energizing the electric heater 12 to generate heat and energizing the fan 13.

In this embodiment, a cylindrical container-like object such as a motor cover is used as the article body 30A to be baked and painted. At the bottom of this article body 30A is a hole 3 for inserting the motor shaft.
1 is formed. Incidentally, the outer surface of the article body 30A is baked and painted.

The article holder 20 is shaped like a cylindrical container with a bottom. The outer diameter of the article holder 20 is approximately the same as or slightly smaller than the inner diameter of the article main body 30A.

This article holder 20 has its opening side facing downward.
The article holder 20 is installed by inserting it into the hole 4 of the upper plate 2 from above and placing the lower end of the article holder 20 on the stepped portion 11a of the exterior body 11. A shelf 25 for supporting the article 30 is formed on the outer side of the article holder 20 closer to the bottom (or closer to the top in the installed state). Further, on the bottom plate 20a of the article holder 20, an article 30 set on the article holder 20 is mounted.
A hole 22 for discharging hot air is formed on the inner surface side.

The cover unit 26 is formed into a cylindrical container shape having an inner diameter considerably larger than the article 30 to be baked. A Suita opening 27 is formed in the bottom wall 26a of the cover unit 26. This cover unit 26 is installed on the upper plate 2 with the opening side facing downward and surrounding the outside of the article 30 held on the article holder 20.

A thermocouple 28 for measuring the atmospheric temperature within the space 4S is placed in a space S surrounded by the upper surface of the upper plate 2, the outer surface of the article holder 20, and the inner surface of the cover unit 26. This thermocouple 28 is connected to a control panel 40, and the thermocouple 28 is connected to a control panel 40.
8 detects the ambient temperature in the space S, and the power supply to the electric heater 12 and fan 13 can be automatically controlled based on the signal.

Use this baking coating device Z! - To explain the method of applying baking coating to the surface of an article, the article body 30 to be subjected to baking coating is
Paint 32 is applied to the outer surface 30a of A in advance, and the painted article 30 is placed in the article holder 2 as shown in FIG.
Set above 0. Incidentally, after the article 30 is set, a cover 26 is placed over the outside thereof. In this state, electric heater 1
2 and the fan 13, the air heated by the electric heater 12 is blown upward by the fan 13, and the hot air passes through the blow-off hole 15 of the exterior body 11 and the hole 22 of the article holder 20 and blows the paint-covered article. The hot air is blown into the inner cavity of 30, and the hot air causes the article 30 to become
Heating starts from the side opposite to the paint application surface 30b). The hot air blown into the interior cavity of the article 30 passes through the holes 31 in the article 30 and then through the holes 27 in the cover unit 26 to be released into the atmosphere. Further, a part of the hot air blown into the article holder 20 from the exterior body 11 side passes through the small hole 23 provided in the side wall of the article holder 20 and enters the space S inside the cover unit 26.
The paint is blown out to raise the temperature in the space S and heat the paint-covered article 30 from its outer surface as well. The reason for heating the space S in this way is to reduce the temperature difference between the temperature of the article 30 itself and the outside (the space S), and to reduce the heat radiation from the article 30. The diameter, number, etc. of the small holes 23 are set so that the atmospheric temperature within the space S does not become higher than the temperature of the article body 30A itself.

When the article body 30A is heated from its inner surface 30b side,
The article body 30A itself is always in a higher temperature state than the coating film 32 on its outer surface, and as the temperature of the article body 30A itself increases, the coating film 32 is heated by the heat from the article body 30A. At this time, since the coating film 32 is heated and cured from the inner layer side, even if some solvent remains in the coating film 32, the solvent will be vaporized and released to the outside.

When the temperature of the article body 30A itself is raised to about 180° C., the coating film 32 applied to the outer surface 30a of the article body is completely cured and firmly adheres to the outer surface 30a of the article body. At this time, the ambient temperature inside the space S is approximately 100°C, and when the inside of the space S reaches a predetermined ambient temperature (about 100°C), the thermocouple 28 detects the temperature. In response to this signal, the electricity to the electric heater 12 and fan 13 is turned off, and the baking coating is completed. Incidentally, when the baking temperature attainment signal is issued from the thermocouple 28, only the electric heater 12 is turned off, and the fan 13 is allowed to continue operating to blow cooling air onto the product 30, the cover assembly 26, etc. The cover unit 26 and the product 30 can be cooled down in a short time, and these members will not become hot when the product 30 is removed.

Figure 3 shows the elapsed time until the baking coating is completed when baking coating is applied to the surface of an article using the baking coating apparatus Z shown in Fig. 1. Item 30A to be treated has a diameter of 55 mm and a height of 18 mm.
A container-shaped die-cast molded product with a wall thickness of 3 mm was used, and the electric heater 12 was a heat-generating one. In this experimental example, it was possible to completely bake paint in about 40 seconds. When the physical properties of the paint film of the baked paint bath product were examined, good results were obtained in all tests such as adhesion, hardness, solvent resistance, and governance.

In addition, in the embodiment described in "-", the electric heater 12 is used as the heat source of the heating device IO; however, the electric heater 12 is used as the heat source.
Instead, it is possible to use a suitable device such as a gas burner.

Further, in the above embodiment, a method of applying baking paint to the outer surface of a cylindrical container-shaped article was shown, but the baking painting method of the present invention applies paint to the entire surface of an article having a shape other than a cylindrical container shape. It goes without saying that the present invention can be applied to articles of any appropriate shape as long as they can be heated from the surface on which the paint is applied.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a baking coating apparatus for carrying out the baking coating method of the embodiment of the present invention, FIG. 2 is an exploded perspective view of the apparatus shown in FIG. 1, and FIG. It is a characteristic graph of the article temperature, the atmospheric temperature in the space, and time when baking painting is performed using the . 1...Base 10...Heating device 30...Article with paint 3QA...Article main body 30a...Paint application surface 30b...Anti-paint application surface 32...Paint Figure 3

Claims (1)

[Claims] 1. One side (30a) of the article body (30A) to be baked and painted
) is heated by the heating device (10) from the side opposite to the paint application surface (30b) of the article body (30A) to coat the paint (32) on the article body ( A baking coating method characterized in that baking coating is applied to the surface of 30A).