JP2733806B2 - Drying method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared transmittance of a coating material applied to a base material surface in advance before drying in a conventional drying oven such as a conventional hot air oven or a far infrared drying oven after coating. The present invention relates to a drying method of preheating in a drying furnace for drying a coating film formed on the surface of a base material using infrared rays in a region having a high base material and a high absorption rate of the base material.

[0002]

2. Description of the Related Art Conventionally, as a drying method for drying an object to be dried to which various paints have been applied, a drying method using a so-called hot air oven or a drying oven using far infrared rays is known.
The drying mechanism of these drying methods is understood as follows.

[0003] First, an object to be dried made of a metal plate or the like having a surface coated with a paint made of a resin such as a solvent or an acrylic resin is carried into a furnace. Next, hot air is blown or far infrared rays are irradiated. Then, the solvent on the surface of the paint applied to the object to be dried is first evaporated, and the surface loses fluidity and solidifies. When heat such as hot air propagates inside, that is, toward the base material side, the coating film is solidified by heating. Then, the solvent inside from the surface breaks through the already solidified coating film surface and evaporates. Then, traces of foaming remain on the surface and pinholes are formed. Therefore, in a conventional hot air oven or a drying oven using far-infrared rays, the solvent is diverged in a setting room without abrupt heating, followed by irradiating far-infrared rays with a small temperature gradient and blowing hot air.

However, the conventional drying method using these drying furnaces has a problem that it takes a long time to perform drying while maintaining the temperature at such a low temperature that foaming does not occur.

Particularly, in a heating furnace for short-time drying by a combination of hot air and infrared rays, the surface of the coating film becomes higher in temperature, and a temperature difference occurs between the coating film surface and the metal surface at the interface between the coating film and foaming occurs. There was a problem that easily occurred.

[0006] On the other hand, "Near-infrared liquids, powders, coatings, and stoves" (Japanese Utility Model Laid-Open No. 1-151873), "Light plates for paint baking furnaces" (Japanese Utility Model Application No. 2-43217), USP 4,863,375 "BA"
KINGMETHOD FOR USE WITH LIQUID OR POWDER VARNISHIN
G FURNACE ”(baking method for youth
With Liquid Or Powder Burnishing
Furnis) and the like are known. In these conventional examples,
There is a description of "a kind of near-infrared liquid, powder, coating, baking method of stove", "Improve the method of baking articles of stove by utilizing the characteristics of fast high temperature and strong penetration force of near infrared, paint A device that dries quickly and enhances the adhesion of the powder, that is, as a so-called liquid or powder liquid coating, powder, liquid paint, gas or fluid in the form of powder liquid is attached to the surface of the object as a transport medium. Then, a method of coating the coat evenly by heating and melting ”is described.

Alternatively, a drying oven using near infrared rays,
Alternatively, a drying method in which a high-temperature part and a low-temperature part are sequentially formed and dried in a drying furnace, or a ceramic reflector is provided behind a near-infrared lamp, and a heater is provided in the ceramic reflector. " There is a description.

In the October issue of the coating technology special edition, there is a description of "middle wavelength infrared radiator" (Oct. 20, 1990, pages 211-213, published by Riko Publishing Co., Ltd.). That is, "radiation energy that reaches the coating film is partially absorbed, partially reflected, and partially transmitted. The absorbed energy is converted into heat, and the coating film is heated and dried. In the case of, the radiant energy transmitted through the coating heats the base material because of the presence of the base material and the body, and heats the coating from the inside by heat conduction.

Near infrared ray: temperature 2000-2200 ° C. Maximum energy wavelength about 1.2 μm, large energy density, large reflection and transmission energies, fast rising speed (1-2 seconds), and short life of about 5000 hours.

Mid-infrared ray: temperature 850-900 ° C, maximum energy wavelength about 2.5 μm, energy density, absorption. The permeated energy is balanced and the energy penetrates into the coating film, and the life is long.

Far infrared rays: temperature 500-600 ° C., maximum energy wavelength about 3.5 μm, small energy density, well absorbed but tend to be absorbed and heated on the coating surface, long rise time (5-15 minutes), convection Large loss. It is said.

Furthermore, in order to “2. Mid-wavelength infrared ray with maximum efficiency, to dry faster and obtain better coating quality”, that is, to heat and dry with maximum efficiency, the following two conditions must be satisfied simultaneously. Need to be.

The high temperature radiant energy of the infrared radiator is proportional to the fourth power of the absolute temperature (T) of the radiator.

Eb∝T ⁴

The higher the temperature, the greater the radiant energy.

The wavelength of maximum energy is somewhat shorter than the peak absorption of the paint

The maximum peak wavelength available for industrial infrared heating of paints is without exception around 3 μm. Therefore, an infrared radiator having a maximum energy wavelength of about 2.5 μm has good absorption and transmission, and can heat the base material and also from the inside.

The above relation, Wien's displacement law, representing the relationship between the temperature (T) of the infrared radiator and the maximum energy wavelength (λm),

From λm = 2897 / T

T = (t + 273) = 2897 / 2.5

T = 880 ° C.

The medium-wavelength infrared ray satisfies this condition and has a large effective energy and a maximum efficiency. It is said.

However, Japanese Utility Model 1-151873 and Japanese Utility Model 2
-43217, USP 4,863,375, etc., state that the coating film is dried using near-infrared light.However, the properties of near-infrared light used are generally described only and applied to metal surfaces. There is no description on the optimum range and selection of the infrared ray to be irradiated based on the relationship between the coating film to be formed and the near infrared ray.

On the other hand, in the case of far-infrared rays and mid-infrared rays conventionally used for drying a coating film, a region where the coating film has a high absorptivity, that is, a region where the coating film has a good infrared absorptivity, is selected and used. This is for the purpose of heating from the coating film surface.
However, when infrared rays having a high absorptance of the coating film are used, the problem of generation of pinholes is essentially encountered. For this reason, there is a problem that it takes a long time to perform drying while maintaining a low temperature that does not cause foaming.

In the above-mentioned “October Special Issue of Coating Technology”, there is no description about selection of infrared rays based on the relationship between infrared rays and the absorption rate of a base material or selection of infrared rays based on the cause of pinhole generation. It was concluded that there was no infrared radiation radiator with a maximum energy wavelength of around 2.5 μm, which had good absorption and transmission, and was able to heat the base material and also from inside.

On the other hand, in the process of drying a coating applied to the surface of a base material by near-infrared light, the inventor prefers to select a region having a high infrared absorptivity by the applied coating rather than to select a region having a high infrared absorption. It has been found that selecting a near-infrared ray in a region having high properties can suppress the occurrence of pinholes. It is presumed that the base material surface located at the interface with the coating is directly heated on the object coated with the coating rather than from the coating surface, and the coating is dried from the base material surface in reverse. Is done.

That is, in general, when a metal is used as a base material, the reflectance of the metal increases as the wavelength of infrared rays increases, and the heat absorption rate of the metal increases as the wavelength decreases. As for the coating film, if the coating film is dried using near infrared rays, it is rather pinhole if dried using near infrared light having high transmittance to the coating film, that is, poor absorption of the coating film. Is presumed to be heated without being formed.

Therefore, the inventor of the present invention has previously disclosed Japanese Patent Application No. 2-3109.
16 In the "method of drying the coating film", "the coating material applied to the surface of the base material is formed on the surface of the base material by using infrared rays in a region having a high infrared transmittance to the coating film and a high absorption rate of the base material. A method for drying a coating film characterized by drying the coated film. "

On the other hand, it is known to provide an air curtain at an opening of a drying oven such as a tunnel oven to the outside air. The air curtain is required to maintain the furnace temperature and prevent the heat in the tunnel furnace from leaking to the outside air. It is more effective that the wind speed of the air used for the air curtain is higher. In order to maintain the temperature, the air used for the air curtain is circulated and used, and cooling the air curtain installed at the opening of the tunnel furnace has not been used because it causes a temperature loss. .

[0029]

SUMMARY OF THE INVENTION The inventor of the present invention has proposed a method of applying an infrared ray to a coating film of a coating material previously applied to the surface of a base material before drying in a conventional drying oven such as a conventional hot air oven or a far-infrared drying oven after coating. Preliminary drying in a drying oven that dries the coating film formed on the surface of the base material using infrared rays in a region where the transmittance is high and the base material has a high absorption rate. It was found that the adhesion between the base material and the coating film was improved, the smoothness of the surface was improved, and the gloss was improved as compared with the case where the coating was dried.

[0030]

Means for Solving the Problems The present invention is based on these findings. That is,

The step of coating the object to be coated, and then the wavelength peak in the region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm.
Using near-infrared light having the following wavelengths, a step of preheating in a drying furnace for drying the coating film formed on the base material surface, and then a drying method characterized by comprising a step of further heating and drying.

And

The step of applying a coating on the object to be coated, and then the wavelength peak in the region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm.
Using near-infrared light having the following wavelengths, a step of preheating in a drying furnace for drying a coating film formed on the base material surface, a step of further applying a coating on the object to be coated, and then further heating and drying. A drying method, comprising:

And

The step of coating the object to be coated, and then the wavelength peak in the region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm.
Using near-infrared rays having the following wavelengths, a step of preheating in a drying furnace for drying a coating film formed on the base material surface, and then a step of further applying a coating on the object to be coated, which was applied to the base material surface Drying by drying the coating film formed on the surface of the base material using near-infrared light having a wavelength peak of 2 μm or less in a region where the infrared transmittance of the coating film is high and the base material has a high absorption rate. A drying method, comprising a step of preheating in a furnace, and a step of further heating and drying.

Is provided.

[0037]

[Function] In the painting process, paint is applied to the surface of the object to be painted. Next, in the preheating step, the peak of the wavelength in the region where the infrared transmittance to the coating film of the coating material applied to the base material surface is high and the base material has a high absorptance is 2 μm or less on the work surface. Irradiate near infrared rays. Then, the infrared light transmitted through the coating film is absorbed by the base material having the coating film formed on the surface, and the base material surface is heated. When the base material is heated, the coating film is heated from the base material side to disperse the solvent contained in the paint.
Next, heating is further applied in the main heating furnace. Heating in this heating furnace is performed from the coating film surface side, but the solvent in the coating film starts to solidify because the solvent in the coating film is diverged from the base material side in the preheating step, so the solvent in the coating film There is no foaming caused by further divergence.

After the preheating, a step of further coating the object to be coated, and then a step of performing main heating, or a step of further applying the coating to the object after the preheating, and a step of applying a coating of the coating applied to the surface of the base material. Using a near-infrared ray having a wavelength peak of 2 μm or less in a region having a high infrared transmittance and a high absorptivity of the base material, preheating is performed in a drying furnace for drying a coating film formed on the base material surface. In the case of a step followed by a main heating step, even if further coating is applied after the first coating, the infrared rays transmitted through the coating film in the preheating step are absorbed by the base material having the coating film formed on the surface and are absorbed by the base material. The surface of the base material is heated, and the coating is heated from the base material side by the heating of the base material to spread the solvent contained in the coating, and then applied and dried. Does not occur.

Further, after preheating, a step of further coating the object to be coated, the peak of the wavelength in the region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm. Using near-infrared rays consisting of the following wavelengths,
In the case of a step of preheating in a drying furnace for drying the coating film formed on the base material surface and then a step of performing main heating, the preheating is further absorbed by the base material having the coating film formed on the surface by new preheating. The surface of the base material is heated, and the coating film is heated from the base material side by heating the base material to spread the solvent contained in the paint, and then applied and dried. No dripping occurs.

[0040]

[Example] When a metal plate is used as a base material on which a coating film is formed, the metal plate may be iron, aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tankel, antimony, It consists of cadmium, chromium, iridium, cobalt, magnesium, tungsten and other metals, with copper, aluminum and iron being preferred. As a paint for forming a coating film applied to the metal surface, an acrylic resin paint, a urethane resin paint, an epoxy resin paint, a melamine resin paint, and other paints can be used. The coating film may be a coating film obtained by melting a so-called powder coating film (polyester, epoxy, acrylic, etc.).

Tables 1 to 4 show the reflectance of each metal at each wavelength (AMERICAN INSTITUTE OF PHYSICS HANDBOO).
K, American Institute of Physics Handbook 6-120). The higher the reflectance, the lower the absorption, and the lower the reflectance, the higher the absorption.

FIG. 1 is an infrared absorption curve of a butylated urea-butylated melamine resin. Figure 2 shows bisphenol A
It is an infrared absorption curve of a type epoxy resin. FIG.
It is an infrared absorption curve of a homopolymer (acryl type). FIG. 4 is an EMA homopolymer (acrylic) infrared absorption curve. FIG. 5 is an infrared absorption curve of the unsaturated polyester resin. FIG. 6 shows a characteristic curve of a near-infrared lamp used in this example and a characteristic curve of a far-infrared lamp used in a comparative example. The peak wavelength of the near infrared lamp is 1.4
μm, and the peak wavelength of the far-infrared lamp is 3.5 μm.

As a metal plate, iron, aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead,
Uses metal plate made of rhodium, silver, tankel, antimony, cadmium, chromium, iridium, cobalt, magnesium, tungsten, and uses acrylic resin paint, urethane resin paint, epoxy resin paint, melamine resin paint as paint If the wavelength peak is 2
μm or less infrared lamp, preferably 1.2 μm to 1.5 μm
It is desirable to use a so-called near-infrared lamp.

Embodiment 1

Near-infrared lamp (output peak 1,4 μm)

Metal plate Bonded steel plate (plate thickness 1 mm, size 1
(00mm x 100mm)

Paint Melamine resin (Amilac No.1531, manufactured by Kansai Paint Co., Ltd., white, alkyd melamine resin paint, viscosity 20 sec, Iwata Cup NK-2 viscometer)

Comparative Example 1

Far-infrared lamp (output peak 3.5 μm)

Metal plate Bonded steel plate (plate thickness 1 mm, size 1
(00mm x 100mm)

Paint Melamine-based resin (Amirac No1531, manufactured by Kansai Paint Co., Ltd., white, alkyd melamine resin paint, viscosity 20 sec, Iwata Cup NK-2 viscometer)

Embodiment 2

Near-infrared lamp (output peak 1,4 μm)

Metal plate Bonded steel plate (plate thickness 1 mm, size 1
(00mm x 100mm)

Paint Acrylic resin (Magiclon No.1531, manufactured by Kansai Paint Co., Ltd., white, acrylic / melamine / epoxy resin paint, viscosity 20 sec, Iwata Cup N
K-2 viscometer)

Comparative Example 2

Far-infrared lamp (output peak 3.5 μm)

Metal plate Bonded steel plate (plate thickness 1 mm, size 1
(00mm x 100mm)

Paint Acrylic resin (Magiclon No.1531, manufactured by Kansai Paint Co., Ltd., white, acrylic / melamine / epoxy resin paint, viscosity 20 sec, Iwatacup N
K-2 viscometer)

For Example 1, Example 2, Comparative Example 1, and Comparative Example 2, the ambient temperature and irradiation time were 30 ° C. × 12 minutes, 140 ° C. × 10 minutes for the respective film thicknesses of 30 μm, 40 μm, and 50 μm.
Min, 150 ° C x 8 minutes, 160 ° C x 6 minutes, 170 ° C x 5 minutes, 180
Table 5 (Example 1), Table 6 (Comparative Example 1), Table 7 (Example 2), Table 8 show the foaming and the number of pinholes in each case of ° C × 4 minutes.
This is shown in (Comparative Example 2).

The embodiments shown in FIGS. 7, 8 and 9 are based on the following findings. That is, `` drying the coating film formed on the surface of the base material using infrared rays in a region where the infrared transmittance of the coating film of the coating material applied to the base material surface is high and the absorption rate of the base material is high is used. A simple circulation type air curtain is installed at the opening to the outside air of the furnace using the method of drying the coating film, which is characterized by using the above method, and the coating film applied to the base material is dried in the furnace. It was found that many pinholes were generated.

Compared with a conventional drying oven such as a hot-air oven, “the infrared rays in the region where the transmittance of the coating material applied to the surface of the base material to the coating film is high and the base material has a high absorption rate are used. A method for drying a coating film characterized by drying a coating film formed on the surface of a material. " Therefore, the heat released from the furnace opening is large, and the temperature of the air supplied to the air curtain gradually rises. In advance, if the material to be dried is sprayed beforehand, it is heated from the surface side of the coating film by the hot air without being heated from the base material side, so that the surface is dried (solidified), and a thin diaphragm is generated on the surface. When heated from the material side, the solvent inside from the surface breaks through the already solidified diaphragm surface and evaporates. Then, it is presumed that traces of foaming remain on the surface and produce pinholes. That is, it has been found that it is more effective not to exert the influence of the air heated by the infrared irradiation on the work outside the effective infrared irradiation range.

In FIGS. 7, 8 and 9, reference numeral 11 denotes a tunnel furnace, and W denotes a work having a base material surface coated with paint.
The work W is made of a metal plate as a base material.
It consists of iron, aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tankel, antimony, cadmium, chromium, iridium, cobalt, magnesium, and tungsten. An acrylic resin paint, a urethane resin paint, an epoxy resin paint, or a melamine resin paint is applied on the base material of the work W.

The tunnel furnace 11 has two openings, a work entrance A and a work exit B. 12 is an infrared lamp. In this embodiment, the infrared lamp 12 is an infrared lamp having a wavelength peak of 2 μm or less, preferably 1.2 μm.
A so-called near-infrared lamp of μm to 1.5 μm is used.
FIGS. 1 to 6, Table 1 to FIG. Select based on Table 8 and install in necessary places in the furnace. 13 is an air curtain. The air curtain 13 is used for the tunnel furnace 1.
One work entrance A and one work exit B are installed. 14 is an air outlet of the air curtain, and 15 is the air inlet. 16 is a fan, 17 is an air outlet 1
4. A circulation duct for connecting the air suction port 15. 1
8 is an air outlet 14 from the fan 16 of the circulation duct 17.
It is a filter installed on the side. 21 is a cooling device. The fan 16 circulates the air so as to blow out the air sucked in from the air inlet 15 from the air outlet 14.

Reference numerals 22 and 23 denote modular roll motors,
Reference numeral 4 denotes a damper installed upstream of the fan 16 of the circulation duct 17 and operated by a mod roll motor 22; 25, a damper driven by a mod roll motor 23; 26, an exhaust fan; 27, an air outlet 14;
Is installed in the module and senses the temperature,
23 is a temperature controller for controlling the operation of 23. These constitute an air curtain and a cooling device 21.

In the embodiment shown in FIG. 8, the infrared lamp 12 is also installed at the place where the air curtain 13 is installed. In FIG. 9, reference numeral 31 denotes an effective irradiation range of the infrared lamp 12. In the effective irradiation range 31, the work W is heated from the base material side of the work W by an infrared lamp to dry the coating film. 32 is an air blowing range. In this embodiment, the effective irradiation range 31 slightly overlaps with the air blowing range.

Next, the operation of the embodiment shown in FIGS. 7, 8 and 9 will be described. Work W coated with paint
Is carried into the tunnel furnace 11 from the work entrance A.
Then, the air passes through the air curtain 13 and is blown by the air outlet 14. However, the air supplied by the air curtain is cooled by the cooling device 21 and the temperature rise is suppressed, so that the air is blown on the surface of the work W. Even if it abuts, it does not act on the coating film surface to form a coating film. That is,
During the use of the air curtain, the temperature controller 27 which detects the temperature of the air outlet 14 as, for example, 110 degrees, indicates that the temperature in the tunnel furnace 11 is 160 degrees,
If the set temperature of the air blown from 4 is 80 degrees, 30
Mod roll motor 22, to correct the temperature difference between degrees
Activate 23. In this state, the air intake port 15
In this case, the temperature is 130 ° C. Then, the mod roll motor 22 opens the damper 24 and introduces outside air into the circulation duct 17. Mod roll motor 23
The damper 25 is opened, and the exhaust fan 26 is operated to exhaust the air in the circulation duct 17 to the outside of the circulation duct 17. When the temperature controller 27 detects that the temperature of the air blown out from the air outlet 14 has become equal to or lower than the set temperature,
Each of the dampers 24 and 25 is held at the opening degree, and the temperature of the air curtain 13 is held.

Next, in the tunnel furnace 11, an infrared lamp 1 is formed on the surface of the base material of the work W, which is composed of infrared rays in a region having a high infrared transmittance to the coating film and a high absorption rate of the base material.
Irradiate 2. Then, the infrared light transmitted through the coating film is absorbed by the base material having the coating film formed on the surface, and the base material surface is heated. Therefore, the coating film is heated and solidified from the back surface of the coating film near the base material surface. Since the surface coating is not formed by the air curtain 13, even if the solvent in the coating evaporates, the solidified coating surface is not broken and no pinhole is formed.

As shown in FIG. 8, the air curtain 1
When an infrared lamp 12 that irradiates infrared rays in a region having a high infrared transmittance with respect to the coating film of the coating material applied to the base material surface and a high absorption rate of the base material is installed at the installation location of 3, the air curtain 13 Also at the installation location, the surface of the base material on which the coating film is formed is irradiated with infrared rays in a region where the infrared transmittance of the coating film is high and the absorption rate of the base material is high. Then, the infrared light transmitted through the coating film is absorbed by the base material having the coating film formed on the surface, and the base material surface is heated. Therefore, the coating film is heated and solidified from the back surface of the coating film near the base material surface, and the coating film is dried from the installation position of the air curtain 13.

Table 9 shows the embodiment illustrated in FIG.
FIG. 9 shows the air curtain wind speed and the pinhole generation state in the coating film at the temperature and the temperature in the comparative example using the air curtain without using the cooling device. To prevent the occurrence of pinholes, it is desirable to maintain the temperature at about 80 ° C. or less.

Setting conditions

Paint Melamine resin

Object to be coated Bonded steel sheet 1.2t

Film thickness 30 microns

Room temperature 30 ° C

Furnace temperature 160 ° C

Air curtain height (air outlet to air inlet) 2 m

Air curtain wind speed

At 10 m / s at the air outlet, 4 m / s at the air inlet, at 7 m / s at the air outlet, 2.8 m / s at the air inlet, and at 4 m / s at the air outlet. In the mouth, it was 1.2 m / s.

Next, the embodiment shown in FIGS. 10, 11 and 12 will be described. 51 is the first painting booth, 5
Reference numeral 4 denotes a second painting booth. First painting booth 51, second
In the painting booth 54, iron,
Workpiece W made of aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tankel, antimony, cadmium, chromium, iridium, cobalt, magnesium, tungsten, etc. On the material, a coating film composed of an acrylic resin paint, a urethane resin paint, an epoxy resin paint, and a melamine resin paint is formed. FIG.
In the embodiment illustrated at 0, the painting booth consists of only the first painting booth. The second coating booth 54 has the same structure as that of the first coating booth 51, and further forms, for example, a 30 μm-thick coating film on the work W dried in the preheating furnace 52 to apply so-called thick coating.

Reference numeral 52 denotes a preheating furnace. Preheating furnace 52
Comprises a tunnel furnace or a mountain furnace. In this embodiment, an infrared lamp having a wavelength peak of 2 μm or less, preferably a so-called near-infrared lamp having a wavelength of 1.2 μm to 1.5 μm is used as the infrared lamp 12. Further, as the preheating furnace 52, the furnace illustrated in FIGS. 7 and 8 may be used. FIGS. 1 to 6, Table 1 to FIG. Select based on Table 8 and install in necessary places in the furnace. In the embodiment shown in FIG. 10, the preheating furnace 52 has an atmosphere temperature of 14 ° C.
The work W is heated at a temperature of 0 to 160 ° C. for 3 to 4 minutes, and the object temperature of the work W is set to 40 to 60 ° C. In the embodiment illustrated in FIGS.
Heat is applied to the work W for ~ 3 minutes to bring the object temperature of the work W to 50-70 ° C. In the preheating furnace 52, FIG.
An air curtain 13 as shown in FIG. 8 may be installed.

Reference numeral 53 denotes a main heating furnace. FIG. 10, FIG.
1, the embodiment shown in FIG. 12 comprises a conventional hot blast stove, or a far-infrared tunnel tunnel furnace or a chevron furnace. Further, as the heating furnace, the furnace illustrated in FIGS. 7 and 8 may be used. In the embodiment illustrated in FIG. 10, the main heating furnace 53 maintains the atmosphere at 130 to 150 ° C. and heats the work W for 20 to 30 minutes. In the embodiment illustrated in FIGS. 11 and 12, the workpiece W is heated for 30 to 50 minutes while maintaining the ambient temperature at 200 to 220 ° C.

Next, the operation of the embodiment will be described. FIG.
As shown in FIGS. 0, 11, and 12, a first coating booth 51, which is a coating step, applies a coating to the surface of a workpiece W, which is an object to be coated. Next, the surface of the work W is irradiated with infrared rays in a region having a high infrared transmittance and a high absorptivity of the base material with respect to the coating film of the coating material applied to the base material surface in the preheating furnace 52 which is a preheating step. Then, the infrared light transmitted through the coating film is absorbed by the base material having the coating film formed on the surface, and the base material surface is heated. When the base material is heated, the coating film is heated from the base material side to disperse the solvent contained in the paint. Next, heating is further applied in the main heating furnace 53. The heating in the heating furnace 53 is performed from the surface side of the coating film. However, the solvent in the coating film is diverged from the base material side in the preheating step. Does not occur as a result of the further divergence of.

As shown in FIG. 11, in the first painting booth 51 in the painting step, a paint is applied to the surface of the work W which is the object to be coated, and then the work W is further coated after preheating. 12, a step of performing main heating in the main heating furnace 53, or a step of performing secondary coating on the work W in the second coating booth after preheating in the preheating furnace 52 as shown in FIG. In a preheating furnace 52 for drying the coating film formed on the surface of the base material using infrared rays in a region having a high infrared transmittance to the coating film of the coating material applied to the surface of the material and a high absorption rate of the base material, In the case of the next preheating step and then the main heating step, even if a second coating is added after the first coating, the infrared rays transmitted through the coating film by the preheating step formed the coating film on the surface. The surface of the base material is heated by being absorbed by the base material. Coating by heating the base material to become to be applied and dried over to dissipate the solvent contained in the coating is heated from the base material side, no sagging of the coating film be thick coating.

Further, as shown in FIG. 12, a coating material is applied to the surface of the work W to be coated in a first coating booth 51 in a coating step, and a preheating furnace 52 is further heated after preheating. Applying a secondary coating to the base material, using a coating film formed on the base material surface using infrared rays in a region having a high infrared transmittance to the coating film of the coating material applied to the base material surface and a high absorption rate of the base material A second pre-heating step in a pre-heating furnace for drying the pre-heating furnace, and then a main heating step in the main heating furnace 53, the base material having a coating film formed on the surface by a new second pre-heating step. The surface of the base material is heated, and the coating film is heated from the base material side by heating the base material, so that the solvent contained in the paint is dispersed and applied and dried.
Even if it is applied thickly, no dripping will occur in the coating film. Since the divergence of the solvent further advances, it is possible to further raise the temperature of the hot blast stove and shorten the drying time.

FIGS. 13 and 14 are central sectional views of each embodiment in which the preheating and the main heating are performed in the same furnace, and the preheating is performed in the vicinity of the work entrance A of the same furnace. FIG.
FIG. 14 relates to a tunnel furnace 62 and FIG. Both furnaces are fully heated by hot air as a whole,
In the chevron furnace 61 shown in FIG. 13, the infrared lamp 12 is placed near the inside of the furnace connected to the work entrance A in the elevation portion 63 continuous to the work entrance A, and in the tunnel furnace shown in FIG. Install. Then, preliminary heating is performed by the infrared lamp 12 or by using hot air in combination with the operation of the infrared lamp 12. When the hot air is used together, the preheating time can be shortened. Further, preheating is performed by spraying a plurality of infrared lamps for irradiating infrared rays in a region having a high infrared transmittance to a coating film of the coating material applied to the base material surface and a high absorption rate of the base material, and an effective irradiation range of the infrared lamp. Composed of hot air.

Therefore, the surface of the object to be coated is irradiated with infrared rays in a region having a high infrared transmittance to the coating film of the coating material applied to the surface of the base material and a high absorption rate of the base material,
Hot air is blown into the effective irradiation range of infrared rays. Then, in the infrared irradiation range, the temperature is maintained at a certain temperature or more by hot air, and the infrared light is passed through the coating film and heated from between the base material and the coating film by the infrared light. The hot-air spraying point on the surface of the object to be coated is irradiated not only with hot air but also with infrared rays in a region where the infrared ray transmittance is high with respect to the coating film of the paint applied to the surface of the base material and the absorption rate of the base material is high. Therefore, it is possible to perform preheating without generating pinholes or bubbles when the solvent evaporates and evaporates due to drying of the coating film surface.

Next, in the mountain furnace 61 shown in FIG. 13, the main heating is performed by hot air at the center of the furnace, and in the tunnel furnace 62 shown in FIG. 14, the main heating is performed by hot air after the center.

Next, there will be described an embodiment in which preliminary heating and main heating using a hot air oven are performed after coating, and a comparative example in which drying is performed directly using a hot air oven after coating.

Embodiment 3

At the painting booth, a bond steel plate (plate thickness 1 mm,
An acrylic paint (Acrylite 100, manufactured by Chiyoda Paint Co., Ltd.) is applied to a size of 100 mm × 100 mm) at 30 μm. Next, it is carried into a tunnel furnace equipped with a near-infrared lamp having an output peak of 1.4 μm. Atmospheric temperature is 1
The passage time in the furnace at 50 ° C. was 3 minutes and 30 seconds, and the object temperature of the work was 50 ° C. Next, the ambient temperature is 140 °
C was placed in a hot blast stove for 25 minutes.

The height of the obtained work was 2H in pencil hardness, 100/100 in density, and no foaming or swelling was observed.

Comparative Example 3

At the painting booth, a bond steel plate (plate thickness 1 mm,
An acrylic paint (Acrylite 100, manufactured by Chiyoda Paint Co., Ltd.) is applied to a size of 100 mm × 100 mm) at 30 μm. Then, 25 ° C was placed in a hot-air
Placed for minutes.

The height of the obtained work was pencil hardness H, density was 100/100, and foaming and swelling were 20 pieces / 100c.
m2.

Next, there will be described an embodiment in which preliminary heating, secondary coating, and main heating using a hot air oven are performed after coating, and a comparative example in which drying is performed using a secondary coating direct hot air oven after primary coating.

Embodiment 4

At the painting booth, a bond steel plate (plate thickness 1 mm,
An acrylic paint (Acrylite 100, manufactured by Chiyoda Paint Co., Ltd.) is applied to a size of 100 mm × 100 mm) at 30 μm. Next, it is carried into a tunnel furnace equipped with a near-infrared lamp having an output peak of 1.4 μm. Atmospheric temperature is 1
The passage time in the furnace at 50 ° C. was 2 minutes and 30 seconds, and the object temperature of the workpiece was 60 ° C. Then, an acrylic paint (Acrylite 100 manufactured by Chiyoda Paint Co., Ltd.) was again applied to 30 μm.
Apply. Next, it was set in a hot blast stove at an ambient temperature of 210 ° C. for 40 minutes.

Almost no sagging or foaming of the coating film was observed, which was less than 1% of the manufactured work.

Comparative Example 4

At the painting booth, a bond steel plate (plate thickness 1 mm,
An acrylic paint (Acrylite 100, manufactured by Chiyoda Paint Co., Ltd.) is applied to a size of 100 mm × 100 mm) at 30 μm. Then, an acrylic paint (Acrylite 100 manufactured by Chiyoda Paint Co., Ltd.) is applied again at 30 μm. Then
It was placed in a hot air oven at an ambient temperature of 210 ° C. for 40 minutes.

Due to sagging and foaming, product care was required for about 10 percent of the manufactured workpieces.

Therefore, in these examples, the adhesion of the coating film, which is presumed to be due to the immediate release of the solvent and the crosslinking reaction in the preheating furnace, is improved. In addition, it is presumed that the fluidity between the coating film and the metal surface is increased and secondary leveling during the crosslinking reaction is good, and the coating film is smooth and the gloss of the surface is visually improved.

[0104]

Therefore, according to the present invention, even when the solvent in the coating film evaporates, the solidified coating film surface is not broken and no pinhole is formed.

[Brief description of the drawings]

FIG. 1 is an infrared absorption curve of each resin

FIG. 2 is an infrared absorption curve of each resin

FIG. 3 is an infrared absorption curve of each resin

FIG. 4 is an infrared absorption curve of each resin

FIG. 5 is an infrared absorption curve of each resin.

FIG. 6 is a characteristic curve diagram of an infrared lamp.

FIG. 7 is a central sectional view of the embodiment of the present invention.

FIG. 8 is a central sectional view of the embodiment of the present invention.

9 is a partially enlarged view of FIG. 7;

FIG. 10 is a schematic diagram of an embodiment of the present invention.

FIG. 11 is a schematic diagram of an embodiment of the present invention.

FIG. 12 is a schematic diagram of an embodiment of the present invention.

FIG. 13 is a central sectional view of another embodiment of the present invention.

FIG. 14 is a central sectional view of another embodiment of the present invention.

[Table 1] Reflectance of metal at each wavelength

[Table 2] Reflectance of metal at each wavelength

[Table 3] Reflectance of metal at each wavelength

[Table 4] Reflectance of metal at each wavelength

[Table 5] Number of pinholes generated in Example 1

[Table 6] Number of pinholes generated in Comparative Example 1

[Table 7] Number of pinholes generated in Example 2

[Table 8] Number of pinholes generated in Comparative Example 2

[Table 9] Pinhole generation state in the coating film at the air curtain wind speed and temperature in the example and the comparative example using the air curtain without using the cooling device

[Explanation of symbols]

 51 First coating booth 52 Preheating furnace 53 Main heating furnace 54 Second coating booth

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

Claims (3)

(57) [Claims] 1. A step of applying a coating on an object to be coated, and then a peak of a wavelength of 2 μm in a region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high.
A drying method, comprising: a step of preheating in a drying furnace for drying a coating film formed on the surface of a base material using near infrared rays having the following wavelengths; and a step of further heating and drying. 2. A step of applying a coating to an object to be coated, and then a wavelength peak in a region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm.
m, a step of preheating in a drying furnace for drying the coating film formed on the surface of the base material using near-infrared light having a wavelength of not more than m, a step of further coating the object to be coated, and a step of further heating and drying. A drying method, comprising a step of causing a drying process. 3. A step of applying a coating to an object to be coated, and then a wavelength peak in a region where the infrared transmittance to the coating film of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high is 2 μm.
m, using a near-infrared ray having a wavelength of not more than m, a step of preheating in a drying furnace for drying the coating film formed on the surface of the base material, and a step of further applying a coating on the object to be coated, Drying the coating film formed on the surface of the base material using near-infrared light having a wavelength peak of 2 μm or less in a region having a high infrared transmittance and a high absorptivity of the base material with respect to the coating film of the paint. A drying method, comprising a step of preheating in a drying furnace, and a step of further heating and drying.