JP2514178B2 - Infrared and hot air combined dryer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combined infrared and hot air dryer. More specifically, the infrared generator that irradiates infrared rays in a region where the coating of the paint applied on the surface of the base material has a high infrared transmittance and the absorptance of the base material is high, and the irradiation direction of the infrared generator intersects. The drying device is used together with hot air blown onto the material to be dried in a predetermined direction.

[0002]

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

That is, first, a material to be dried, which is composed of a metal plate or the like and whose surface is coated with a coating material such as a solvent and a resin such as an acrylic resin, is carried into a furnace. Next, hot air is blown or far infrared rays are irradiated. Then, in the former case, the solvent on the paint surface applied to the material to be dried first evaporates, and the surface loses fluidity and solidifies.

In the latter case, the solvent on the surface and in the vicinity of the surface first evaporates, loses fluidity and solidifies. When heat such as hot air propagates inside, that is, toward the base metal side, solidification of the coating film progresses due to heating. Then, the solvent in the coating film near the base material breaks through the already solidified coating film surface and evaporates. Then, the trace of foaming remains on the surface and pinholes occur. Therefore, in the conventional hot air oven or the drying oven using far infrared rays,
The solvent is diffused in the setting room without rapid heating, and then far infrared rays are radiated with a small temperature gradient or hot air is blown.

However, in the conventional drying method using these drying ovens, there is a problem that it takes a long time to dry while keeping the temperature difference at the interface between the surface of the coating film and the base material small to the extent that foaming does not occur. I had.

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

On the other hand, "near-infrared liquid, powder, coating, stove" (actual flat 1-151873), "light plate for paint baking oven" (real flat 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 varnishing
Furnace) and the like are known. In these conventional examples,
There is a description of "a kind of near-infrared liquid, powder, coating, stove baking method", "Using the fast high temperature and strong penetration characteristics of near-infrared rays, improving the method of baking products of stove, paint To quickly dry and enhance its adhesive force ", that is," the powder, powder paint, liquid paint, gas or fluid in the powder liquid state is adhered to the surface of the object as a transportation medium, just as the so-called liquid or powder liquid is coated. Then, the method of coating the coat evenly by heating and melting is described.

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

Further, the October issue of the coating technology special issue has a description of "medium wavelength infrared radiator" (October 20, 1990, pages 211-213, published by Riko Publishing Co., Ltd.). That is, "The radiant energy that reaches the coating film is partially absorbed, partially reflected, and partially transmitted. The absorbed energy is converted into heat to heat and dry the coating film. In the case of 1, since there is a base material and a body, the radiant energy transmitted through the coating film heats the base material, and the coating film is heated from the inside by heat conduction.

Near-infrared: Temperature 2000 to 2200 ° C. Maximum energy wavelength about 1.2 μm, large energy density, large reflected and transmitted energy, fast rising speed (1 to 2 seconds), short life of about 5000 hours.

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

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

Further, in order to "2. Maximum efficiency medium wavelength infrared ray""dry faster and obtain better coating quality", that is, to heat and dry at maximum efficiency, the following two conditions are simultaneously satisfied. Need to be

Radiant energy with a high temperature 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 maximum energy wavelength is somewhat shorter than the peak absorption of the paint

The maximum peak wavelength that can be used for industrial infrared heating of a coating is around 3 μm without exception. Therefore, the infrared radiator, which has the maximum energy wavelength around 2.5 μm, is well absorbed and transmitted, and the base material can be heated and heated from the inside.

The above relation, the Vienna displacement law, which represents 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, has a large effective energy, and has maximum efficiency. It is said that.

However, actual Kaihei 1-151873, actual Kaihei 2
-43217, USP 4,863,375, etc. have a description that the coating film is dried using near infrared rays, but the nature of the near infrared rays used is not generally described and it is applied to the metal surface. There is no description about the optimum range and selection of the infrared rays to be irradiated due to the relationship between the coating film and the near infrared rays.

On the other hand, in the far infrared rays and the mid infrared rays which have been conventionally used for drying a coating film, a region having a high absorptivity of the coating film, that is, a region having a good infrared absorptivity of the coating film is selected and used. This is for the purpose of heating from the inside of the coating film itself. However, the use of infrared rays, which have a high absorptance in the coating film, essentially poses the problem of pinholes. Therefore, since drying is performed while maintaining a temperature difference that does not cause foaming, there is a problem that a rapid temperature rise cannot be performed and it takes time to dry.

Further, in the above-mentioned "Painting Technology Special Issue October issue", there is a description about the selection of infrared rays based on the relationship between infrared rays and the absorptance of the base material, or the selection of infrared rays based on the cause of pinhole generation. In addition, in the coating drying, it is concluded that "the infrared radiator having the maximum energy wavelength around 2.5 μm has good absorption and transmission, and the base material can be heated and heated from the inside."

On the other hand, the inventor, in the process of drying the coating film applied on the surface of the base material by near infrared rays, rather than selecting a region having a high infrared absorption rate by the applied coating film, transmits infrared rays of the coating film. It was found that pinhole generation can be suppressed by selecting near-infrared rays in a highly effective region. It is presumed that the base material surface located at the interface with the coating film is directly heated on the coated object, not the surface of the coating film, and the coating film is dried in reverse from the base material surface. To be done.

That is, in general, when a metal is used as a base material, the longer the wavelength of infrared rays, the higher the reflectance of the metal, and the shorter the wavelength, the higher the heat absorption rate of the metal. Regarding the coating film, when drying the coating film using near infrared rays, it is rather pinhole when drying is performed using near infrared rays, which has a high transmittance to the coating film, that is, a low absorption rate of the coating film. It is presumed that it is heated without being formed.

Therefore, the inventor previously filed Japanese Patent Application No. 2-3109.
In 16 "Drying method of coating film", "Infrared ray in a region where the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material is used to form on the surface of the base material. The method for drying a coating film is characterized in that the coating film is dried. "

On the other hand, it is known to irradiate an infrared lamp made of so-called far-infrared rays, mid-infrared rays, etc. for correcting a coating film of an automobile. However, when the infrared rays are radiated to the object to be coated using only the infrared lamp, the area irradiated with the infrared rays temporarily generates heat, but the outside of the irradiation range remains at a low temperature. There was a problem that the temperature rise took time due to the heat transfer to the glass and uneven temperature occurred.

On the other hand, the inventor uses hot air together with an infrared lamp for irradiating infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material. Therefore, it has been found that it is possible to shorten the drying time of the object to be coated. Therefore, the inventor
Proposed "Infrared and hot air combined dryer" of the patent application dated March 12, 2013.

The apparatus is provided with an infrared lamp for irradiating infrared rays in a region having a high infrared transmittance with respect to the coating film of the paint applied to the surface of the base material and a high absorptance of the base material, and an effective irradiation range of the infrared lamp. Infrared and hot air combined drying device characterized by being composed of hot air blown. "And" Infrared in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material. And a plurality of infrared lamps for irradiating the infrared rays, and hot air blown to the effective irradiation range from between the infrared lamps.

Therefore, "the surface of the object to be coated is irradiated with infrared rays in a region in which the coating of the paint applied to the surface of the base material has a high infrared transmittance and the absorptivity of the base material is high, and the infrared rays are effectively irradiated. Hot air is blown to the range, and in the infrared irradiation range, the temperature is maintained at a certain temperature or higher by the hot air, and the infrared rays are heated from between the base material and the coating film by passing through the coating film. Not only the hot air but also the hot air blown on the surface is irradiated with infrared rays in a region where the coating material of the paint applied to the surface of the base material has a high infrared transmittance and a high absorptivity of the base material. No pinholes or bubbles will be generated when the solvent evaporates and dries when dried.When hot air is blown to the effective irradiation range between multiple infrared lamps, the temperature of the hot air will be infrared. Those having an action of. "Which can be cooled infrared lamp together if low temperatures than heating.

However, in this apparatus, since the infrared irradiation direction and the blowing direction of the hot air are the same direction, it is necessary to blow the hot air from between the infrared lamps, and the condenser mirror cannot be installed around the infrared lamps. However, there was a problem in efficiency.

[0035]

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

An infrared generator (11) installed toward the object to be coated (21) and irradiating infrared rays having a wavelength peak of 2 μm or less, and an irradiation direction of the infrared generator (11) are covered in a crossing direction. An infrared and hot air combined drying device, characterized in that it comprises an air discharge port (13) for blowing hot air heated by a heating section (17) installed outside the furnace to the coated object (21),

And

Infrared ray generators (11) installed on both sides of the conveyed object to be coated (21) for irradiating infrared rays having a wavelength peak of 2 μm or less, and an object to be coated between the ceiling surface and the floor surface. An air discharge port (1) for blowing hot air heated by a heating section (17) installed outside the furnace toward (21)
3) a combined infrared and hot air drying device, characterized in that

Providing

[0040]

[Function] The surface of the object to be coated is irradiated with infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material, and intersects the infrared irradiation direction. Hot air is blown onto the coated object from the direction.
Then, in the infrared irradiation range, the temperature is maintained at a certain temperature or higher by hot air, and the infrared rays are heated from between the base material and the coating film by passing through the coating film.

Not only hot air but also infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material are irradiated not only to the hot air but also to the hot air blowing portion on the surface of the object to be coated. Therefore, when the surface of the coating film dries, pinholes and bubbles are not generated when the solvent evaporates and diffuses.

Since the irradiation direction of the infrared ray generator and the blowing direction of the hot air are not the same direction, a space can be created around the lamp while preventing the generation of pinholes, bubbles and the like, so that a mirror can be installed.

[0043]

[Example] When a metal plate is used as a base material on which a coating film is formed, examples of the metal plate include iron, aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tanker, antimony, It consists of cadmium, chromium, iridium, cobalt, magnesium, tungsten and other metals, with copper, aluminum and iron being especially preferred. Acrylic resin paints, urethane resin paints, epoxy resin paints, melamine resin paints, fluorine paints, and other paints can be used as the paint that forms the coating film applied to the metal surface. The coating film may be a coating film obtained by melting a so-called powder coating (polyester type, epoxy type, acrylic type, 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 absorptivity, and the lower the reflectance, the higher the absorptance.

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. Figure 3 shows MMA
It is an infrared absorption curve of a homopolymer (acrylic type). FIG. 4 is an EMA homopolymer (acrylic) infrared absorption curve. FIG. 5 is an infrared absorption curve of unsaturated polyester resin. FIG. 6 shows the characteristic curve of the near-infrared lamp used in this example and the characteristic curve of the far-infrared lamp used in the comparative example. Near infrared lamp has a peak wavelength of 1.4
The peak wavelength of the far infrared lamp is 3.5 μm.

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

Example 1

Near infrared lamp (output peak 1,4 μm)

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

Paint melamine resin (Kansai Paint Co., Ltd. Amylak No1531, 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 Bonde steel plate (plate thickness 1 mm, size 1
(00 mm x 100 mm)

Paint melamine resin (Kansai Paint Co., Ltd. Amylak No1531, white, alkyd melamine resin paint, viscosity 20 sec, Iwata Cup NK-2 viscometer)

Example 2

Near infrared lamp (output peak 1,4 μm)

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

Paint Acrylic resin (Magicalon No1531, 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 Bonde steel plate (plate thickness 1 mm, size 1
(00 mm x 100 mm)

Paint acrylic resin (Magicalon No1531, Kansai Paint Co., Ltd., white, acrylic / melamine / epoxy resin paint, viscosity 20 sec, Iwata Cup N
K-2 viscometer)

Regarding Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the atmospheric temperature and irradiation time were 130 ° C × 12 minutes and 140 ° C × 10 for the respective film thicknesses of 30 μm, 40 μm and 50 μm.
Min, 150 ° C × 8min, 160 ° C × 6min, 170 ° C × 5min, 180
Table 5 (Example 1), Table 6 (Comparative Example 1), Table 7 (Example 2), and Table 8 show foaming and pinhole numbers in each case of ° C x 4 minutes.
This is shown in (Comparative Example 2).

FIG. 7 is a central sectional view of the apparatus according to the embodiment of the present invention. FIG. 8 is a partially enlarged front view of the infrared lamp part,
9 is a sectional view taken along line XX of FIG. 7, FIG. 10 is a central sectional view of another embodiment, and FIG. 11 is a partially enlarged view of FIG.

Reference numeral 11 denotes an infrared ray generator, which is an infrared lamp in this embodiment. The infrared lamp 11, which is an infrared generator, uses iron,
Acrylic resin paint is used as a paint, using a metal plate made of aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tanker, antimony, cadmium, chromium, iridium, cobalt, magnesium, and tungsten. When a urethane resin-based paint, an epoxy resin-based paint, a melamine resin-based paint, or a fluorine-based paint is used, it is 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. The distance from the surface of the infrared lamp 11 to the surface of the object to be coated 21, which is a work, was set at about 250 to 300 mm. Reference numeral 12 is a condenser mirror. The focusing mirror 12 is
It is installed on the back surface of the infrared lamps 11 which are horizontally installed. Each bank of a plurality of infrared lamps 11 is installed so as to face the inner surface of the tunnel furnace 31 with the article 21 to be sandwiched therebetween on both sides of the article 21 in the conveying direction. In this embodiment, a pair of banks is installed in the tunnel furnace 31, but two or more banks may be installed. A is
A work carry-in port, and B is a work carry-out port.

Reference numeral 13 is an air discharge port installed on the floor of the tunnel furnace 31, and 14 is an air suction port installed on the ceiling surface of the tunnel furnace 31 so as to face the air discharge port. Are connected by. The circulation duct 15 includes a fan 16 for moving air from the air suction port 14 to the air discharge port 13, and a heating unit 17 for heating the moved air.
Is installed. The heating unit 17 is heated by a heat source using heating by electric resistance, but other means may be used as long as heating is possible. A filter 18 removes dust mixed in the circulation duct 15. Reference numeral 32 is a conveyor that conveys the object to be coated 21 into and out of the tunnel furnace 31.

In the case of melamine-based paint, hot air of 130 ° C. or higher, preferably 150 ° C. or higher, 1.0 m / sec or higher,
Desirably, it is supplied at 2.0 m / sec or more. In the case of acrylic resin, hot air of 100 ° C. or higher, preferably 170 ° C. or higher, is 1.0 m / sec or more, preferably 2.0 m / s.
Supply above ec. These temperature and wind speed are selected depending on the distance between the infrared lamp 11 and the object to be coated 21.

Next, the operation of the embodiment will be described. The infrared lamp 11 irradiates the surface of the object to be coated 21 with infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and the absorptivity of the base material is high. Irradiation of infrared rays is performed in a crossing direction, in this embodiment, a horizontal direction parallel to the conveying direction of the object to be coated 21, and hot air is blown in a vertical direction from the floor surface to the ceiling surface. Hot air is discharged from the air discharge port 13 so that the object 21 passes through. Then, within the effective irradiation range of infrared rays, the temperature is maintained at a certain temperature or higher by hot air, and the infrared rays are heated from between the base material and the coating film through the coating film. The hot air that has heated the object to be coated 21 is sucked into the air suction port 14, and the circulation duct 1
5 is circulated, heated again, and discharged from the air discharge port 13.

Since heating is performed not only by near infrared rays but by heating with hot air, a so-called peeled state is generated. Therefore, when heating is performed only by irradiation of near infrared rays, temperature unevenness due to delay in temperature rise occurs. It happens, but it is possible to avoid such things.

In addition, the infrared irradiation and the hot air blowing are simultaneously performed. When the hot air heated before being irradiated with infrared rays is sprayed on the object to be coated 21 in advance, it is heated from the base material side and is heated from the coating film surface side by the hot air,
Surface dryness (surface solidification) occurs, a thin diaphragm is generated on the surface,
After that, when heated from the base metal side, the solvent inside the surface is
The already solidified membrane surface pierces and evaporates, leaving traces of foaming on the surface, creating pinholes, which is not the case in this example.

That is, the coating film is irradiated with an infrared lamp 11 made of infrared rays in a region having a high infrared transmittance and a high absorptivity of the base material. Then, the infrared rays transmitted through the coating film are absorbed by the base material having the coating film formed on the surface, and the surface of the base material is heated. Therefore, the coating film is heated and solidified from the coating film back surface close to the base material surface, hot air is blown in the infrared irradiation range C, the surface coating film is not formed even by the hot air, the solvent in the coating film Even if it evaporates, it does not break the solidified coating film surface to form pinholes. Painted object 21
The hot air blowing spot on the surface of the coating is not only hot air, but is also irradiated with infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material. Pinholes and bubbles do not occur when the solvent evaporates and diffuses due to the surface drying.

This embodiment may be installed in a furnace body such as a mountain furnace or a tunnel furnace. In that case, it is possible to reduce energy loss and it is effective for deodorization.

Next, Table 10 shows the equipment and materials used for the test and the room conditions at the time of the test, and Table 11 shows the comparison of the temperature and the time until the standard hardness in the hot air passage and the use of this example is reached. Now, a comparison between near infrared rays and hot air used together with the use of this example and only near infrared rays is shown.

That is, as shown in Table 11, the thermosetting paint was examined by using the apparatus according to the present invention, in comparison with the conventional hot air method, for the temperature and time until the standard hardness was reached.

Common test conditions

1. Paint viscosity = 16-18 sec

2. Coating thickness = 20μ (± 2)

3. Hardness measurement = pencil hardness

The temperature is the temperature of the atmosphere inside the furnace when a hot air stove is used, and in the present embodiment, the temperature of the atmosphere near the surface of the work. As a result, the time required for each curing was shortened by the present apparatus as follows as compared with the conventional hot air oven.

1. 1/10 with melamine

2. With acrylic, 1/18

3. Polyester, about 1 / 4.4

4. Approximately 1 / 3.6 in fluorine

By comparing the test results by these two kinds of drying methods, it was found that the effect of this device was remarkable.

Table 12 shows that the present apparatus was used to irradiate only the near infrared ray lamp, and to perform the near infrared ray irradiation and hot air jetting at the same time to select the acrylic paint for the relationship between temperature, time and coating film hardness, and the temperature conditions were 110 ° C and 170 ° C. Represents a table tested in two ways. As shown in Table 12, the time required for only the near infrared irradiation is as follows.

A. Based on the hardness H,

When hot air of 110 ° C. is blown out, about 1 /
4.6

When hot air of 170 ° C. is blown out, about 1 /
7

B. Based on hardness 2H,

When hot air of 110 ° C. is blown out, about 1 /
4.5

When hot air of 170 ° C. is blown out, about 1 /
9

As a result of the above, there is a clear difference in the curing speed of the coating film between the near infrared ray lamp irradiation and the hot air + near infrared ray irradiation, and the higher the temperature of the hot air, the shorter the curing time. found.

Both 110 ° C. and 170 ° C. in Table 12 indicate the temperatures of the hot air near the work surface.

Next, using this apparatus, only hot air was jetted, and the relationship between elapsed time and coating film hardness was examined for melamine paint and acrylic paint.

1. Sample plate Bonded steel plate 0.8mm
(Thickness) Size 600mm x 700mm

2. Hot air velocity 2.0m / sec

3. Paint viscosity 18-19sec / NK-
2 (Viscometer)

The measurements were made for 9 minutes, and both had hardnesses of B or less, which were not suitable for practical use.

Next, the embodiment shown in FIGS. 10 and 11 will be described. In this embodiment, an air curtain is installed in the opening of the embodiment shown in FIGS. The tunnel furnace 31 has two openings, a work carry-in port A and a work carry-out port B. Reference numeral 11 is an infrared lamp. Also in this embodiment, the infrared lamp 12 has a wavelength peak of 2 μm.
An infrared lamp of m or less, preferably a so-called near infrared lamp of 1.2 μm to 1.5 μm is used. Infrared rays in a region having a high infrared transmittance with respect to the coating film of the paint applied to the surface of the base material of the object to be coated 21 and a high absorptivity of the base material are shown in FIGS. 1-Select based on Table 8 and install in the required location in the furnace. 41 is an air curtain. The air curtains 41 are installed at the work inlet A and the work outlet B of the tunnel furnace 31, respectively. 44
Is an air outlet of the air curtain, and 45 is an air inlet thereof. Reference numeral 46 is a fan, and 47 is a circulation duct that connects the air outlet 44 and the air inlet 45. Reference numeral 48 denotes a filter installed on the air outlet 44 side of the fan 46 of the circulation duct 47. Reference numeral 51 is a cooling device. Fan 4
Reference numeral 6 designates the air blown out from the air sucked in through the air suction port 45.
Circulate the air so that it blows out from 4. C is the effective irradiation range of the infrared lamp 11. The air in the air blowing range D from the air blowing port 44 may collide with the partial effective irradiation range C as shown in FIG.

52 and 53 are modulo roll motors, 5
4 is a damper installed upstream of the fan 46 in the circulation duct 47 and operated by the mod roll motor 52; 55 is a damper driven by the mod roll motor 53; 56 is an exhaust fan; and 57 is an air outlet 44.
Is installed in the
It is a temperature controller that controls the operation of 53. These components constitute the air curtain and the cooling device 51.

Next, the operation of the embodiment will be described. The object 21 to which the paint is applied is carried into the tunnel furnace 31 from the work carrying-in port A. Then, the air curtain 41
, And air can be blown at the air outlet 44,
Since the air supplied from the air curtain is cooled by the cooling device 51 and its temperature rise is suppressed, even if the air comes into contact with the surface of the object to be coated 21, it acts on the surface of the coating film to form a coating film. There is no. That is, while the air curtain is being used, the temperature controller 57 that detects the temperature of the air outlet 44 as 110 degrees, for example, has 160 degrees inside the tunnel furnace 31, and is blown out from the air outlet 44. When the set temperature of air is 80 ° C., the mod roll motors 52 and 53 are operated to correct the temperature difference of 30 ° C. In this state, the temperature at the air intake port 45 is 130 ° C. Then, the mod roll motor 52 opens the damper 54 and introduces the outside air into the circulation duct 47. The mod roll motor 53 opens the damper 55 and operates the exhaust fan 56 to exhaust the air in the circulation duct 47 to the outside of the circulation duct 47. Temperature controller 57
However, when it senses that the temperature of the air blown out from the air outlet 44 is below the set temperature, the dampers 54, 5
5 is held at that opening to keep the temperature of the air curtain 41.

By the way, "the coating film formed on the surface of the base material is dried by using infrared rays in the region where the infrared transmittance of the coating material applied to the surface of the base material is high and the absorption rate of the base material is high. The method of drying the coating film is characterized in that the conventional simple air circulation curtain is installed in the opening to the outside of the furnace using the coating film applied to the base material in the furnace. When dried, many pinholes are generated.

Compared with a conventional drying oven such as a hot-air oven, "using infrared rays in a region where the coating material of the coating material applied to the surface of the base material has a high infrared transmittance and a high absorption rate of the base material, A furnace using "a method for drying a coating film, which comprises drying the coating film formed on the surface of the material" is efficient. Therefore, the heat radiated from the furnace opening is large, and the temperature of the air supplied to the air curtain gradually rises, and the air of the air curtain heated to the temperature inside the furnace before being irradiated with the infrared rays is heated to the opening of the furnace. In advance, when sprayed on the material to be dried, it is not heated from the base material side but is heated from the coating film surface side by hot air, so surface drying (surface solidification) occurs, a thin diaphragm occurs on the surface, and then the mother material When heated from the material side, the solvent inside the surface breaks through the already solidified membrane surface and evaporates. Then, it is speculated that the traces of foaming remain on the surface and cause pinholes. That is, the inventor has found that, outside the effective irradiation range of infrared rays, it is more effective not to affect the work by the air heated by infrared irradiation.

Therefore, with the structure of this embodiment, since the surface coating film is not formed even by the air curtain 41, even if the solvent in the coating film is evaporated, the solidified coating film surface is broken and pinholes are generated. Does not form.

Then, in the tunnel furnace 31, as shown in FIGS.
In the same manner as illustrated in FIG. 2, the base material surface of the object to be coated 21 is irradiated with the infrared lamp 11 composed of infrared rays in the region where the infrared transmittance of the coating film is high and the absorptance of the base material is high, and hot air is blown. To spray. Then, the infrared rays transmitted through the coating film are absorbed by the base material having the coating film formed on the surface, and the surface of the base material is heated. At the same time, since it is heated by hot air, temperature unevenness does not occur. Therefore, the coating film is heated and solidified from the back surface of the coating film close to the surface of the base material.

Table 9 shows the state of pinhole occurrence in the coating film at the air curtain wind speed and temperature in the embodiment shown in FIG. 10 and the comparative example using the air curtain without the cooling device. In order to prevent the occurrence of pinholes, it is desirable to keep the temperature below 80 ° C.

Setting conditions

Paint melamine resin

Article to be coated Bonde steel plate 1.2t

Coating thickness 30 microns

Indoor temperature 30 ° C

Furnace temperature 160 ° C

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

Air curtain wind speed

When the air outlet is 10 m / s, the air inlet is 4 m / s, when the air outlet is 7 m / s, the air inlet is 2.8 m / s, and when the air outlet is 4 m / s, the air intake is 4 m / s. It was 1.2 m / s by mouth.

Therefore, in this embodiment, by using near-infrared irradiation in combination with hot air and cold air, it is possible to further prevent foaming and pinholes.

[0117]

[Effects of the Invention] Therefore, curing can be performed in a relatively short time without using a furnace body, and foaming and pinholes do not occur. That is, even when heating is performed more rapidly than heating with only hot air, the material to be coated is heated from the base material side by irradiation of near infrared rays, and the atmospheric temperature is maintained by the hot air, so that drying is performed in a short time.

[Brief description of drawings]

[Figure 1] Infrared absorption curve of each resin

[Figure 2] Infrared absorption curve of each resin

[Figure 3] Infrared absorption curve of each resin

[Figure 4] Infrared absorption curve of each resin

FIG. 5: 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 an apparatus according to an embodiment of the present invention.

FIG. 8 is a partially enlarged view of an infrared lamp portion of the device according to the embodiment of the present invention.

9 is a sectional view taken along line XX of FIG.

FIG. 10 is a central sectional view of an apparatus according to another embodiment of the present invention.

FIG. 11 is a partially enlarged view of FIG. 10;

[Table 1] Metal reflectance at each wavelength

[Table 2] Metal reflectance at each wavelength

[Table 3] Metal reflectance at each wavelength

[Table 4] Metal reflectance 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 occurrence 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 the cooling device

[Table 10] Equipment and materials used for testing and room conditions during testing

[Table 11] Comparison of temperature and time required to reach standard hardness in hot air passage and use of this example

[Table 12] Comparison of near-infrared and hot-air combined use and near-infrared only use using this example for acrylic paint

[Explanation of Codes] 11 Infrared Generator 13 Air Discharge Port

Claims (2)

(57) [Claims] 1. The apparatus is installed toward an object to be coated (21),
An infrared generator (11) for irradiating infrared rays having a wavelength peak of 2 μm or less, and a heating unit (outside the furnace) installed outside the furnace in a direction intersecting the irradiation direction of the infrared generator (11). An infrared and hot air combined drying apparatus comprising an air discharge port (13) for blowing hot air heated in (17). 2. An infrared generator (11) installed on both sides of an object (21) to be conveyed, which irradiates infrared rays having a wavelength peak of 2 μm or less, and an object to be covered between a ceiling surface and a floor surface. An infrared and hot air drying device comprising: an air discharge port (13) for blowing hot air heated by a heating unit (17) installed outside the furnace toward the coated object (21).