JPH074838A - Drying furnace - Google Patents

Abstract

PURPOSE:To efficiently dry an article to be dried while reducing the number of infrared lamps in use. CONSTITUTION:A drying furnace comprises means for generating hot air for raising an ambient temperature in the drying furnace 11 to a level required for curing a coating, and an infrared source which comprises a plurality of infrared lamps 13 disposed adjacent one another, and in which one of the infrared lamps 13 is adapted to be selected for use in irradiating a coated article and to be dried, and other infrared lamp or lamps 13 provided nearby is used when the infrared lamp becomes out of order.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a drying oven. Specifically, it relates to a drying furnace that uses an infrared lamp and hot air together.

[0002]

2. Description of the Related Art Conventionally, there is known a drying furnace that uses a furnace such as a mountain furnace to blow hot air to dry an object to be dried.
Furthermore, the applicant has already proposed a drying furnace for irradiating infrared rays such as near infrared rays having a peak of a wavelength of around 1.2 μm to 1.5 μm to dry the material to be dried (Japanese Patent Application No. Hei 2). -310916 "Outside of drying method of coating film").

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, "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.

In addition, the October issue of the coating technology special issue has a description of "medium wavelength infrared radiator" (October 20, 1990, Riko Publishing Co., Ltd., pages 211-213). 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.

(1) 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 .

(2) 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.

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

Furthermore, in order to "2. Maximum efficiency medium-wave infrared rays" 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

(1) Radiant energy having a high infrared radiator temperature 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.

(2) The maximum energy wavelength is slightly shorter than the peak absorptance of the paint.

The maximum peak wavelength that can be used for industrial infrared heating of paint 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.

[0020]

However, the applicant can reduce the number of infrared lamps by raising the atmospheric temperature in the furnace by hot air without using infrared lamps for all heating. We have found that by reducing the number of infrared lamps, the number of infrared lamps, which are inferior in heating efficiency to the use of hot air, can be reduced and the drying efficiency can be improved.

On the other hand, actual Kaihei 1-151873, actual Kaihei 2-4321
7, USP 4,863,375, etc., describes that the coating film is dried using near infrared rays, but the properties of the near infrared rays used are generally described as being 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.

Further, in the above-mentioned "Painting Technology Special Issue October issue", the selection of infrared rays based on the relationship between the infrared rays and the absorption rate of the base material, or the selection of infrared rays based on the cause of pinhole generation In the coating drying, it is concluded that "the infrared radiator having the maximum energy wavelength around 2.5 μm absorbs well and penetrates, and the base material can be heated and heated from the inside."

On the other hand, the wavelength peak is 1.2 μm to 1.5 μm.
It is known that so-called near-infrared rays having a thickness of μm have a high infrared ray transmittance with respect to a plastic thin film and a high metal absorption rate.

[0024]

Means for Solving the Problems

Drying characterized by comprising hot air which raises the atmospheric temperature in the drying furnace to a temperature required for curing the coating film, and an infrared ray generator for irradiating the object to be dried on which the coating film is formed. Furnace,

And

A hot air which raises the ambient temperature in the drying furnace to a temperature required for curing the coating film and a plurality of infrared lamps are installed in close proximity to each other and one of them is selected and used to form the coating film. A drying furnace characterized by comprising an infrared generator that uses another infrared lamp installed in close proximity when the infrared lamp in use becomes unusable while irradiating the dried object.

And

Hot air for raising the atmospheric temperature in the drying furnace to a temperature required for curing the coating film, and an infrared ray generator installed at an interval of about 250 mm for irradiating the object to be dried on which the coating film is formed. A drying oven, characterized in that

And

Hot air for raising the atmospheric temperature in the drying furnace to a temperature required for curing the coating film and an infrared lamp group in which a plurality of infrared lamps are placed close to each other are installed at intervals of about 250 mm. Infrared rays that use one of them to irradiate the material to be dried on which a coating film has been formed and to use another infrared lamp that is installed close to the infrared lamp when it is not in use A drying oven, characterized by comprising a generator,

Providing

[0033]

[Function] The atmospheric temperature in the drying furnace is heated by hot air to a temperature required for curing the coating film of the material to be dried. An infrared lamp is radiated toward the material to be dried on which the coating film is formed, which is carried into the drying oven, and the coating film is dried by infrared rays together with hot air.

[0034]

[Examples] As the base material of the material to be dried W, plastics other than metal can be used as long as they are materials that are not deformed by heating by selecting temperature conditions and the like. As the metal used for the base material, iron, aluminum, copper, brass,
Gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tanker, antimony, cadmium, chromium,
Consists of iridium, cobalt, magnesium, tungsten and other metals, but especially copper, aluminum,
Iron is preferred.

7 to 10 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 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. The peak wavelength of the near infrared lamp is 1.
4 μm, the peak wavelength of the far infrared lamp is 3.5 μm.

As a base material of the material to be dried W, iron, aluminum, copper, brass, gold, beryllium, molybdenum, nickel, lead, rhodium, silver, tanker, antimony, cadmium, chromium, iridium, cobalt, magnesium, tungsten are selected. When using a one-part urethane coating containing a so-called block material as a coating, the infrared lamp with a wavelength peak of 3 μm or less and the mid-infrared lamp with a wavelength peak of 2.5 μ are also used. Effective, but preferably 1.2 μm to 1.5 μm
It is desirable to use a so-called near-infrared lamp having infrared rays in a region having a high infrared ray transmittance with respect to the plastic coating film and a high absorptivity of the metal as a base material.

Reference numeral 11 is a drying furnace. The drying furnace 11 is composed of a drying booth, and a conveyor 12 for transporting the material to be dried W is installed inside. Reference numeral 13 denotes an infrared generator, which is a near infrared lamp in this embodiment. Infrared lamp 13
Installs two infrared lamp groups 14 arranged close to each other to form one unit at three locations on the inner surface of the drying furnace 11.

Reference numeral 21 is a gas discharge port, and 22 is a gas suction port. The heated gas generated by the hot air generator 23 is discharged from the gas discharge port 21 into the drying furnace 11 by the blower 24 to heat the inside of the drying furnace 11 and is sucked through the gas suction port 22. The hot air sucked through the gas suction port 22 is circulated.

Infrared lamp 13 which is an infrared generator
Is a metal of the object W to be heated, such as iron, aluminum, copper,
Brass, gold, beryllium, molybdenum, nickel,
When a metal plate made of lead, rhodium, silver, tantalum, antimony, cadmium, chromium, iridium, cobalt, magnesium, tungsten is used and a one-component urethane resin coating film is used as a thin film, the wavelength peak is 3 μm. The following infrared lamps, preferably 1.2 μm
It consists of a so-called near-infrared lamp of 1.5 μm, but a mid-infrared lamp having a wavelength peak of 2.5 μ is also effective. The distance from the surface of the infrared lamp 13 to the surface of the workpiece W to be heated, which is a work, was set at about 150 to 600 mm. A plurality of infrared lamps 13 are installed horizontally.

FIG. 3 shows an installation circuit of the infrared lamp 13 when a three-phase alternating current is used. An infrared lamp group is composed of two infrared lamps installed side by side. Infrared lamp 1
3 is connected via magnet switches 42, 42, while one of the infrared lamps 13 is being used, the current abnormality detector 41 senses non-conduction, and the sequencer 43 is operated to activate the other infrared lamp 13. Then, the infrared lamp used can be switched. Therefore, the infrared lamp 13 can always be irradiated.

Therefore, the atmospheric temperature in the drying furnace 11 is heated by hot air to a temperature required for curing the coating film of the article W to be dried. That is, 150 ° C for melamine paint, 180 ° C for acrylic paint, 210 ° for epoxy powder paint.
C, 230 ° C for polyester powder coatings. The infrared lamp 13 irradiates the material to be dried on which the coating film is formed, which has been carried into the drying oven 11, and the coating film is dried by infrared rays together with hot air.

As shown in FIG. 15, banks 32 and 32 in which infrared lamps 12 are horizontally arranged at intervals of 50 mm are provided in a mountain furnace 31 having a distance 1 between the loading point and the desorption point, which is a horizontal portion, of 5000 mm. Install at 1800 mm intervals. In front of each bank 32, 32, width 300 mm, height 10
The test piece 33 having a thickness of 00 mm and a thickness of 1.5 mm and having a coating film formed thereon is passed through. The distance between each bank 32, 32 and the test piece 33 is 600 mm. The infrared lamp 12 has a wavelength peak of 1.2 μm to 1.5 μm, a filament length of 260 mm, and an output of 1 kw / 1. The following paints were applied to the test pieces, respectively.
Let's use electrostatic thinner as solvent for (1), melamine-based paint (Amilac (trademark) manufactured by Kansai Paint), (2), acrylic-based paint (Magicalon (trademark) manufactured by Kansai Paint), (1) and (2). (# 1220 manufactured by Daishin Chemical Co., Ltd.). The following paints were applied as powder paints. (3), Epoxy powder coating (Kubo Ken Paint, Theodur DM757-9
01 white (trademark)), (4), polyester powder coating (Theodur PE785-901 white (trademark)).

With respect to each test piece, the atmospheric temperature of the mountain furnace was heated by hot air to the curing condition of each paint, and the interval of the infrared lamp 12 to be turned on was changed to measure the hardness of each test piece coating film. .

(1) Melamine-based paint (curing condition 150 ° C x 5 minutes, hardness H according to paint specifications)

[0046]

(2) Acrylic paint (curing condition 180 ° C x 5 minutes, hardness 2H according to paint specifications)

Lamp pitch (mm) Achieved hardness (pencil hardness) 150 2H (a part of the armpit is generated. It is considered that the lamp interval is too short.) 200 2H 250 2H 300 2H 400 H 500 F

(3) Epoxy powder coating (curing condition 210 ° C x 5 minutes)

[0050]

(4) Polyester powder coating (curing condition: 230 ° C x 5 minutes)

[0052]

Therefore, the lamp pitch is 250 mm.
Even if the number is narrowed and the number of infrared lamps installed in the furnace is increased, there is no difference in effect at a pitch of 250 mm or more.

[0054]

Therefore, according to the present invention, it is possible to efficiently dry the material to be dried while reducing the number of infrared lamps used.

[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: Reflectivity of metal at each wavelength

FIG. 8: Reflectivity of metal at each wavelength

FIG. 9: Reflectivity of metal at each wavelength

FIG. 10: Reflectivity of metal at each wavelength

FIG. 11 is a front view of a drying oven according to an embodiment of the present invention.

FIG. 12 is a side view of the drying oven according to the embodiment of the present invention.

FIG. 13 is a circuit diagram of an infrared lamp used in a drying furnace according to an embodiment of the present invention.

FIG. 14 is a front view of an installed state of an infrared lamp used in the drying furnace according to the embodiment of the present invention.

FIG. 15 is a central cross-sectional view of a mountain furnace according to an embodiment of the present invention.

FIG. 16 is a central cross-sectional view of a bank of infrared lamps installed in a mountain furnace according to an embodiment of the present invention.

[Explanation of symbols]

 11 Drying furnace 13 Infrared generator (infrared lamp)

Claims (4)

[Claims] 1. A hot air which raises an atmospheric temperature in a drying furnace to a temperature required for curing a coating film, and an infrared ray generating device which irradiates an object to be dried on which the coating film is formed. Drying oven. 2. A coating film, wherein hot air for raising the atmospheric temperature in a drying furnace to a temperature required for curing a coating film and a plurality of infrared lamps are installed close to each other and one of them is selected and used. And an infrared generator for irradiating the formed object to be dried with another infrared lamp installed in close proximity when the infrared lamp in use becomes unusable. 3. Hot air for raising the ambient temperature in the drying furnace to a temperature required for curing the coating film, and infrared rays generated at an interval of about 250 mm for irradiating the object to be dried on which the coating film is formed. A drying furnace comprising a device. 4. An infrared lamp, wherein hot air for raising an atmospheric temperature in a drying furnace to a temperature required for curing a coating film and an infrared lamp group in which a plurality of infrared lamps are brought close to each other are installed at intervals of about 250 mm. Select one of the groups and use it to irradiate the material to be dried with a coating film on it and use another infrared lamp that is placed close to the infrared lamp when it is not in use. A drying furnace comprising: