JPH07323257A - Short time heat treatment of organic coating - Google Patents

Abstract

PURPOSE:To produce a coated structural body having excellent characteristics with good workability by irradiating a coating surface with IR rays having peaks at specific wavelengths and forcibly cooling a coating base body at the time of heat treating the org. high-polymer coating on the base body. CONSTITUTION:This heat treatment method consists of a finish varnish applying stage A, a baking stage B and a cooling stage C. A metallic sheet 6 coated with finish varnish is transported by a conveyor 7 and many IR gas heaters 8 are arranged above this sheet in a plane form in the baking stage B. The IR gas heaters 8 radiate the IR rays having the peaks at the wavelengths 2.0 to 4.0mum. In addition, hoods 9 to cover these IR gas heaters 8 and the metallic sheet 6 coated with the finish varnish facing the heaters are installed. The hoods 9 are provided with an air feed port 10 and discharge port 11 for cooling air. The coated structural body having various excellent characteristics is produced by combining self-heat generation by IR absorption of the org. coating polymers and the force cooling of the coated base body.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a short-time heat treatment method for an organic coating, and more particularly to a combination of its own heat generation by infrared absorption of organic coating molecules and forced cooling of a coated substrate. , A method for efficiently producing a coated structure excellent in various characteristics with good workability.

[0002]

2. Description of the Related Art Providing various organic coatings on a substrate such as metal is widely used in the fields of painting, lamination, adhesion, lining and printing. When forming these organic coatings, heat treatment is indispensable, and this heat treatment involves drying, curing (curing) of the formed organic coating,
It is intended for gelation, film formation, fusion bonding and the like.

Conventionally, the heat treatment of the organic coating includes heating in a heating atmosphere in a hot air circulation furnace or the like, radiant heating by infrared rays or the like; direct heating; heating plate; heat conduction heating by heating rollers or the like; high frequency induction heating. Various means such as high-frequency dielectric heating; electric resistance heating by energization are used.

[0004]

The conventional heating of the coated substrate is to heat the entire coated substrate or to heat the entire coated substrate through the heating of the substrate. In terms of heat treatment efficiency and heat-treated product productivity, it was not yet satisfactory.

For example, in the case of coating or printing, discoloration, oxidation, thermal deterioration (disintegration), high temperature of the coating or the substrate due to excessive heating at high temperature or for a long time or exposure to a heating atmosphere for a long time. There is an effect of embrittlement.

Further, in the case of double-sided coating, there is a problem that the coating film or the like provided on the opposite surface is softened or causes scratches, sticking or the like to impair the product value.

Further, in the conventional heat treatment method, since the entire coated substrate is heated to a high temperature, it is also a problem that a long time is required for cooling after the treatment.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the conventional heat treatment method, to preferentially heat the organic polymer coating on the substrate, and to obtain a coating structure excellent in various physical properties of the coating. Another object of the present invention is to provide a heat treatment method for an organic coating that can be manufactured with good properties.

Another object of the present invention is to provide a novel heat treatment method for heat treatment of an organic coating by a combination of heat generation of the organic coating polymer itself by infrared absorption and forced cooling of the coating substrate.

[0010]

According to the present invention, when heat-treating an organic polymer coating applied on a substrate, an infrared ray having a peak at a wavelength of 2.0 to 4.0 μm is applied to the coating surface to be heat-treated. Provided is a heat treatment method for an organic coating, characterized in that the heat treatment is performed while radiating and forcibly cooling at least one surface of the coated substrate.

According to the present invention, a coating comprising a solution or dispersion of an organic polymer is applied onto a substrate, and when the applied coating is dried and cured, the coating surface has a wavelength of 2.0 to 4.0 μm. The coating film is dried by radiating infrared rays having a peak at a relatively low radiant energy, and then infrared rays having a peak at a wavelength of 2.0 to 4.0 μm are radiated at a relatively high radiant energy on the dried paint surface. There is provided a heat treatment method for an organic coating material, characterized in that at least one surface of a coating substrate is heated while being forcedly cooled at least during the curing step of the coating film.

[0012]

In the present invention, an organic polymer coating is applied on a substrate, and the coating is heat-treated, but the coating surface to be treated is irradiated with infrared rays having a peak at a wavelength of 2.0 to 4.0 μm. It is a remarkable feature that the above and the cooling step of forcibly cooling the coated substrate are performed in combination at the same time.

As the infrared absorption spectrum is widely used for the chemical structure analysis of organic polymers, all organic polymers have infrared absorption properties. In the present invention, by utilizing this characteristic of the organic polymer, the organic polymer coating has a wavelength of 2.0.
Irradiation with infrared rays having a peak at ˜4.0 μm. The organic polymer absorbs this infrared ray to generate stretching vibration or bending vibration peculiar to each functional group in the molecule, and self-heats due to this molecular vibration.

In the present invention, this self-heating is concentrated on the organic polymer coating to preferentially heat the organic coating, and the heating of the other portions of the substrate and the like is suppressed, so that the coated substrate is forcibly cooled. . In general, heating by infrared radiation has a delicate influence between the radiator temperature and the coating temperature. For example, when the temperature of the radiator is too low and the coating temperature becomes high, the absorbed energy sharply decreases, and thus it takes time to reach the desired temperature. On the contrary, if the temperature of the radiator is too high, the coating temperature rises rapidly,
Easy to cause foaming and burning. On the other hand, in the present invention,
By forcibly cooling the substrate or the like, it is possible to lower the temperature of the substrate or the backside coating film that is desired to avoid heating and control the plate temperature or coating film temperature. Further, in the case of a heat source of relatively high radiant energy, it is difficult to control the substrate temperature and the coating temperature from the heat source side as described above, but in the present invention, this temperature control is performed by forcibly cooling the coated substrate side. Will be easier.
According to the present invention, the following effects can be obtained by combining the heating of the organic polymer coating by self-heating and the forced cooling of the coated substrate.

(1) It is possible to prevent a portion other than the coating layer, that is, the substrate from being adversely affected by heating. For example, it is possible to prevent the coating film on the opposite surface of the substrate from being softened or from being scratched or sticking. (2) Since forced cooling is performed, when the irradiation of infrared rays is stopped, the coated substrate immediately returns to room temperature, so that the cooling time after heat treatment can be significantly shortened, the overall processing time can be shortened, and the productivity can be improved. be able to. (3) Since self-heating due to the molecular vibration of the organic polymer in the coating is used, the temperature can be strictly controlled, and the coating can be prevented from being overheated, for example, charring or discoloration of printing ink or paint can be prevented. The obtained coating is excellent in various physical properties. (4) Since it is self-heated from within the coating, the solvent and low molecular weight components are efficiently volatilized, and the volatilized solvent, fumes, low molecular weight components, etc. are oxidized on the spot, and these treatments are automatically performed at the same time. To be done. (5) Since infrared irradiation is performed under forced cooling, it is possible to use an infrared source with extremely high irradiation intensity, which enables heating and quenching in a significantly short time, improving workability and improving physical properties. It is possible to improve.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 1 (side view) for explaining an example in which the heat treatment method of the present invention is applied to a finish varnish coating process for a coated metal sheet for can manufacturing, this coating process is performed by a finish varnish coating process. It is composed of a work process A, a baking process B, and a cooling process C.

In the finishing varnish coating step A, the coating roller 1
And a support roller 2 are provided, and the finish varnish supplied from the varnish storage tank 3 via the fan-ten roller 4 is applied to the surface of the base coating metal plate 5 supplied to the nip positions of the rollers 1 and 2. Apply.

In the baking process B, a forcedly cooled conveyor 7 for transporting the finish varnish-coated metal plate 6 is arranged, and a plurality of infrared gas heaters 8 are arranged above it in a planar manner. A hood 9 is provided so as to cover the infrared gas heater 8 and the finishing varnish-coated metal plate 6 facing the infrared gas heater 8. The hood 9 has an inlet 10 for cooling air and an outlet 11 for heated air. It is provided.

The infrared gas heater 8 emits infrared rays having a peak at a wavelength of 2.4 μm, and the irradiation intensity on the finish varnish coating is 11.4 w / cm ² . The finish varnish coating on the coated metal plate absorbs the infrared rays and self-heats. On the other hand, the air having a temperature of 30 ° C. is supplied into the hood 9 through the air supply port 10 and the back surface of the coated metal plate is brought into contact with the forced cooling conveyor to cool the entire finish varnish coated metal plate 6. The temperature of the finish varnish coating reaches 240 ° C or higher, but the temperature of the back surface of the metal plate 6 is suppressed to 150 ° C or lower, and the exhaust temperature is about 30 ° C.
It was 0 ° C. Under the above conditions, the time required for the finishing varnish-coated metal sheet 6 to pass through the baking step was 4 seconds, and the baking of the finishing varnish was completed.

In the cooling step C, a conveyor 13 for conveying the hardened finish varnish-coated metal sheet 12 is arranged, and a cooling water spray nozzle 14 is arranged above it, and the finish varnish is formed. The coated metal plate is sprayed with cooling water and cooled to form the product stack 15.

In the specific example shown in FIG. 1, the finishing varnish metal plate is forcibly cooled by introducing cold air from above, but it is forcibly cooled from below the finishing varnish metal plate by blowing cold air or spraying cooling water. You can also

In FIG. 2 (side view) and FIG. 3 (front view) for explaining such a mode of the baking process, a conveyor 7 for carrying the finish varnish-coated metal plate 6 and an infrared radiator 8 are vertically arranged. It is similar to the case of FIG. 1 provided in a facing relationship, but in this specific example, a large number of cooling nozzles 16 are arranged below the conveyor 7, and cooling water or cold air is supplied from the cooling nozzles 16. 17 is sprayed onto the finish varnish-coated metal plate 6 or the conveyor 7, whereby the finish varnish-coated metal plate 6 is forcibly cooled.

In the heat treatment method of the present invention, the heat treatment by infrared radiation and forced cooling can be performed in a single treatment area as described above or in a plurality of treatment areas.

When the coating material used is a solution or dispersion of an organic polymer, a treatment area for radiating the infrared rays with a relatively low radiant energy to dry the coating film, and a relatively high radiant energy for the infrared rays. It is effective to form a coating film having excellent physical properties by performing a two-step heat treatment in a treatment region where the coating film is radiated to cure the coating film.

Returning to FIG. 1 again, the hood 9 is provided with a coating film drying area B1 and a coating film curing area B2.
Those of the infrared gas heater 8 is relatively low radiant energy located in dry areas B1 (e.g. 2 to 6w / cm ^2), the infrared gas heater 8 'relatively high radiant energy (e.g., 6 to 23w / cm located hardening zone B2 ² ). Of course, in both of these regions, infrared radiation is performed under cooling as in the previous case.

With such an arrangement, the wet coating immediately after coating is gradually heated over time and dried by removing the solvent, and the coating after drying is heated to a predetermined high temperature for a short time. And the curing is completed within a short time.

Infrared heating under forced cooling in the present invention is
Drying or baking of printing ink or coating film provided on a substrate, curing of thermosetting resin film, film formation of resin emulsion particles, gelation of plastisol, film formation or curing of powder coating particles, fusion bonding of resin film It is effective for relaxation of the orientation of the oriented resin film and orientation crystallization or thermal crystallization of the resin film.

If a sizing layer, which also serves as a heat-blocking layer, is provided between the substrate and the organic polymer coating to be heat-treated, heat dissipation from the self-heating organic polymer layer to the substrate is prevented. The heating efficiency can be increased. Further, in the thermosetting resin, the curing reaction that occurs may differ depending on the temperature, but in the present invention, only the desired curing reaction can be selectively caused by strictly controlling the heating temperature. It is also possible to form a temperature distribution in the thickness direction of the organic polymer coating to form a desired degree of heat treatment distribution.

In the present invention, the substrate may be any substrate made of metal or plastic, or a substrate made of a composite material thereof. Examples of the metal substrate include a light metal plate or foil of aluminum or the like or a surface-treated steel plate or foil. Examples of the surface-treated steel sheet or foil include chromate surface-treated steel sheet, electrolytic chromic acid-treated steel sheet (TFS), nickel-plated steel sheet, tin-plated steel sheet, tin-nickel alloy-plated steel sheet, aluminum-plated steel sheet and foils thereof. These metal substrates are materials for three-piece cans such as adhesive cans and welded cans, materials for two-piece cans such as squeezed cans, squeezed and ironed cans, lids for winding up and down, lids for easy open cans, crowns, caps, or cups. It may be a container such as a rectangular container or a material for forming a lid. Further, the metal foil may be a flexible packaging forming material such as a retort pouch, a flexible heat seal lid, and a semi-rigid cup.

Examples of the plastic substrate include plastic films and molded products such as cups, trays, bottles and tubes. Examples of the film include biaxially stretched polyethylene terephthalate film, biaxially stretched nylon film, polycarbonate film and polypropylene. Examples thereof include films and thermoplastic resin films such as polyethylene. These films may be a laminate with the above metal plate or metal foil. The method of the present invention also has an advantage that thermal deformation of a plastic three-dimensional container can be prevented even when the container is coated and baked.

As the organic polymer coating provided on the substrate, various paints, inks, plastisols, coatings,
A film etc. can be mentioned. These coatings may be an undercoat (base coating) or a topcoat (top coating). As the paint, any of organic solvent-based paint, organosol paint, water-based paint, powder paint and the like can be used.

The coating material may be a thermosetting or thermoplastic resin coating material, for example, a modified epoxy coating material such as a phenol / epoxy coating material, an amino / epoxy coating material, or an epoxy / ester coating material; for example, a vinyl chloride-vinyl acetate copolymer,
Vinyl chloride-vinyl acetate copolymer partially saponified product, vinyl chloride-vinyl acetate-maleic anhydride copolymer, epoxy-modified, epoxyamino-modified or epoxyphenol-modified vinyl resin or vinyl-modified paint such as acrylic resin; acrylic Resin-based paints; oil-based paints; alkyd paints;
Polyester coatings; synthetic rubber coatings such as styrene-butadiene copolymers; polyurethane coatings; polyimide coatings, polyamideimide coatings, polyesterimide coatings and the like.

Of the above paints, epoxy resin-based paints are
By preliminarily providing this on the substrate, it can be used as a sizing layer which also serves as a heat insulating layer.

The present invention can also be applied to film formation of an aqueous paint or further baking, wherein the aqueous paint is an emulsion type synthetic resin or synthetic rubber aqueous paint such as ethylene-acetic acid copolymer or acrylic. A thermoplastic water-based paint such as a mold or an ionomer type, a thermosetting water-based paint such as an acrylic-epoxy type is used. A preferred water-based paint is composed of an epoxy resin component, a thermosetting resin as a coating film forming component containing a curing agent resin component for the epoxy resin component, and a carboxyl group-containing acrylic resin as a polymer dispersant. .

The method of the present invention can also be applied to gelation of plastisol of vinyl chloride resin. Plastisol refers to a mixture of a vinyl chloride resin and a plasticizer, which is made into a paste, which can be gelated by heating to form a uniform elastic body. As the vinyl chloride-based resin, in addition to a vinyl chloride homopolymer, a copolymer of vinyl chloride and a small amount of a comonomer such as vinyl acetate, vinylidene chloride, styrene, an acrylic ester, a methacrylic ester, and butadiene may also be used. Can be used. As the plasticizer, a plasticizer generally used for vinyl chloride resins, for example,
Phthalate ester-based plasticizer, aliphatic dibasic acid ester-based plasticizer, phosphate ester-based plasticizer, hydroxy polycarboxylic acid ester-based plasticizer, fatty acid ester-based plasticizer,
Polyhydric alcohol ester plasticizer, epoxy plasticizer,
A polyester plasticizer or the like is used. The plasticizer is 35 to 200 parts by weight per 100 parts by weight of vinyl chloride resin,
In particular, it is used in an amount of 60 to 160 parts by weight.

As the printing ink, oleoresin, rosin, cellulose derivative, alkyd resin, phenol resin, amino resin, acrylic resin, as an ink vehicle,
Various inks using epoxy resin, urethane resin, etc. are used.

As the coating agent, in addition to the various resins described above, various emulsions of olefin resins, synthetic rubbers, fluorine resins and the like can be used.

The organic resin coating used in the present invention is not limited to the one applied as a liquid. That is, the resin coating may be an organic resin film. Examples of such a resin film include isotactic or syndiotactic polypropylene, low-, medium- or high-density polyethylene, linear low density or linear ultra-low density polyethylene, propylene-ethylene copolymer, propylene. -Ethylene-butene copolymers, ethylene-1-butene copolymers, ethylene-acrylate copolymers, olefin resins such as olefin ionomers; polyester films such as polyethylene terephthalate, polyethylene terephthalate / isophthalate, polyethylene naphthalate, Examples thereof include nylon films such as nylon 6, nylon 6,6, nylon 6 / nylon 6,6 copolymers, and polycarbonate film films. These films may be cast films or uniaxially or biaxially stretched films.

The thickness of the organic polymer coating is not particularly limited and varies depending on the application, but is generally 1 to 300 μm.
It is preferable to use those having a thickness of m, particularly 3 to 200 μm.

The infrared radiator used in the present invention may be any one as long as it has the above-mentioned peak wavelength, and the radiator includes an infrared radiation material made of various ceramics.
It consists of a heat source to heat this.

Such ceramics include alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), cordierite (2M).
gO ・ 2Al ₂ O ₃ / 5SiO ₂ ), titania (TiO
₂ ), oxide ceramics such as steatite (MgO · SiO ₂ ) silica, silica-alumina; silicon carbide (Si
C), tungsten carbide (WC), zirconium carbide (ZrC) and other carbide ceramics; boron nitride (B)
N), titanium nitride (TiN), silicon nitride (Si
₃ N ₄ ) and other nitride ceramics; zirconium boride (ZrB ₂ ), titanium boride (TiB ₂ ) and other boride ceramics; tungsten silicide (WSi ₂ ), silicide molybdenum (MOSi ₂ ) and other silicides Examples include ceramics. These ceramics are used as a radiation material in an arbitrary shape such as a linear shape, a planar shape or a tube shape.

On the other hand, combustion heat, electric resistance heat generation, high frequency induction heating or the like can be used as a heat source for heating the infrared radiation material. Thus, an infrared heating device in which the flame (flame) of the combustion burner is brought into contact with the ceramic radiant body, a ceramic radiant body is provided around the resistance radiant body such as a nichrome wire, or the resistance radiant body is embedded in the ceramic radiant body. Any infrared heating device, infrared heating lamp, or infrared heating device consisting of a combination of a high frequency induction coil and a ceramic coated steel plate is used.

The intensity of infrared radiation from the infrared radiator used varies remarkably depending on the type of the object to be infrared-heated and the purpose of the infrared heat treatment, but is generally 2 to 23 w.
/ Cm ² is preferable, and within this range, 2 to 13 w is used for drying or baking of printing ink or finishing varnish.
A relatively low output of / cm ² is suitable, and a high output of about 5 to 23 w / cm ² is desirable for drying or baking general coating films, while heat adhesion of the film or thermal relaxation of the orientation of the film. An output of about 3 to 11 w / cm ² is desirable for crystallization. Further, when performing the two-stage heat treatment, it is desirable to use low radiant energy of ² to 6 w / cm ² during drying and high radiant energy of 6 to 23 w / cm ² during curing.

On the other hand, for forced cooling performed simultaneously with infrared heating, a cooling gas such as cold air or liquid nitrogen gas is sprayed or introduced onto the coated surface, the opposite surface or both, or the opposite surface of the coated surface is cooled with cold water. Contact with spray, cooling roller,
A method of contacting with a heat transfer member such as a cooling conveyance member is adopted.

In the case of forced cooling, the temperature of the surface of the coated substrate opposite to the coating layer is at least 50 ° C. lower than the coating layer temperature, preferably at least 100 ° C. lower. Suitable for the purpose.

[0046]

The present invention will be described in the following examples.

[Example 1] An electric heating type surface heater provided above a metal net conveyor was heated to 800 ° C, and infrared rays having a peak wavelength of about 2.7 µm had an intensity of about 6.8.
Radiation was set to w / cm ² . On the other hand, C is applied to one side of a 0.19 mm-thick electrolytic chromic acid treated steel sheet (hereinafter abbreviated as TFS) coated and baked with epoxy paint on both sides.
A thermocouple was welded so that the temperature change could be traced, and the acrylic water-based paint was applied to the other surface and placed on the net of the conveyor so that the applied surface was on top. The conveyor was driven while blowing cool air of about 5 ° C. from below the net above the conveyor, and the coating surface was passed under the surface heater so as to face the surface heater. The distance between the surface heater and the coated surface was about 5 cm. The time for the sample to pass under the surface heater was adjusted to 4.0 seconds. The peak temperature of TFS measured with a thermocouple was 215 ° C, and the surface temperature of the coating film measured with an infrared thermometer immediately after heating was 245 ° C on the upper surface and 150 ° C on the lower surface.
As a result of observing this sample after cooling, no scratch due to friction with the net was observed in the coating film on the lower surface. Moreover, the pencil hardness of the coating film on the upper surface was 5H, and it was confirmed that the coating film was sufficiently hardened.

Comparative Example 1 A TFS coated with a water-based paint was heat-treated in the same manner as in Example 1 except that cold air was not blown from below the net. T measured with thermocouple
The peak temperature of FS was 225 ° C, and the surface temperature of the coating film measured using an infrared thermometer immediately after the heating was 250 ° C on the upper surface and 220 ° C on the lower surface. As a result of observing this sample after cooling, scratches due to friction with the net were found in the coating film on the lower surface. The pencil hardness of the top coating is 5
It was H, and it was confirmed that it was sufficiently cured.

Example 2 A metal sheet was prepared by laminating polyester biaxially stretched film mainly containing polyethylene terephthalate component on both sides of TFS under the condition that a part of the molecular orientation remains. This laminated metal plate was heat-treated with the heating device shown in Example 1. The processing condition is that the time for the sample to pass under the surface heater is 3.
Example 1 was followed except that the time was adjusted to 5 seconds. The peak temperature of TFS measured with a thermocouple was 200 ° C, and the surface temperature of the film measured with an infrared thermometer immediately after heating was 230 ° C on the upper surface and 195 ° C on the lower surface. After cooling, the polyester film was isolated and evaluated by dissolving the metal of this sample with hydrochloric acid.As a result, the molecular orientation of the film on the treated surface had completely disappeared, but the molecular orientation of the film on the opposite surface was completely lost. Remained about the same as before the heat treatment. No scratches due to friction with the net were observed on the film surface.

Comparative Example 2 A laminated metal plate was heat-treated in the same manner as in Example 2 except that cold air was not blown from below the net. As a result of observing this sample, scratches due to friction with the net were found on the film on the lower surface. In addition, the molecular orientations of the films on the upper and lower surfaces were completely lost.

Example 3 Vinyl chloride plastisol was applied to one side of a 0.25 mm-thick galvanized steel sheet having epoxy size coats on both sides to a thickness of about 0.2 mm, Heat treatment was performed according to the method described in Example 1. The processing conditions were the same as in Example 1 except that the time for the sample to pass under the surface heater was adjusted to 3.0 seconds. The peak temperature of galvanized steel sheet measured by thermocouple is 195
The surface temperature of the vinyl chloride film was 220 ° C. on the upper surface and 180 ° C. on the lower surface as measured by an infrared thermometer immediately after the heating. As a result of observation after cooling, the vinyl chloride film on the heat-treated surface was sufficiently gelled, and the adhesion to the size coat was good.

[Embodiment 4] A chain conveyor connected to a stainless steel mat having a thickness of about 10 mm is immersed in ice water at the lower side, drained at the rising portion, and L at the upper portion.
It was set to be heated by a Schwann burner using PG as a fuel. The aqueous coating material was applied according to Example 1 except that the peak wavelength of infrared rays emitted from the burner was set to about 2.2 μm, and the time for the sample to pass under the burner was adjusted to 3 seconds. The TFS was heat treated. Here, the sample is forcibly cooled by contacting the cooled stainless mat. T measured with thermocouple
The peak temperature of FS was 280 ° C., and the surface temperature of the coating film measured with an infrared thermometer immediately after heating was 310 ° C. on the upper surface and 260 ° C. on the lower surface. As a result of observing this sample after cooling, no scratch due to friction with the net was observed in the coating film on the lower surface. Moreover, the pencil hardness of the coating film on the upper surface was 5H, and it was confirmed that the coating film was sufficiently hardened.

[Example 5] Above the net conveyor, water was sprayed from the lower side, and five ceramic sheath heaters were arranged from the upper side to prepare an infrared heating device. The water-based paint was applied according to Example 1 except that the peak wavelength of infrared rays emitted from the heater was set to about 3.3 μm, and the time for the sample to pass under the heater was adjusted to 7 seconds. The TFS was heat treated. Here, the sample is forcibly cooled by the sprayed water. The peak temperature of TFS measured by a thermocouple was 255 ° C., and the surface temperature of the coating film measured using an infrared thermometer immediately after heating was 280 ° C. on the upper surface and 185 ° C. on the lower surface.
As a result of observing this sample after cooling, no scratch due to friction with the net was observed in the coating film on the lower surface. Moreover, the pencil hardness of the coating film on the upper surface was 5H, and it was confirmed that the coating film was sufficiently hardened.

[Embodiment 6] An electric heating type surface heater provided above a metal net conveyor was heated and set so that infrared rays were radiated to the net. Cooling air was blown to set the net and the items on the net to cool. A water-based paint was applied to one side of TFS coated on both sides according to Example 1 and heat-treated under various conditions using the above apparatus. The results are shown in Table 1. In the table, the evaluation of the cured state is based on pencil hardness as a scale, and the water-based paint sample is heat-treated in an electric oven at 180 ° C. for 10 minutes. A sample having a slightly lower hardness is indicated by Δ, a sample having the same hardness as that of the reference product is indicated by ◯, and a sample having a hardness higher than this is indicated by ⊚. Further, regarding the scratches on the coating film on the back surface, the ones with severe scratches were evaluated as X, the scratches with slight scratches were evaluated as Δ, and the scratches with no scratches were evaluated as ○ by visual judgment. The results obtained are shown in Table 1.

[0055]

[Table 1]

[Embodiment 7] The first half of the drying / curing apparatus is a gas burner heating type heater provided above a metal net conveyor and has a peak wavelength of about 2.7 μm.
So that the infrared rays of about 4w / cm ² are radiated,
It was set so that hot air of about 130 ° C. was blown from the upper surface and cold air of about 5 ° C. was blown from the lower surface. On the other hand, in the latter half of the drying / curing device, an infrared ray with a peak wavelength of about 2.7 μm was radiated with an intensity of about 7 w / cm ² from a gas burner heating type heater installed above a metal net conveyor. The air was blown at room temperature from the upper surface, and cold air of about 5 ° C. was blown from the lower surface. In addition, the passage time of the first half and the second half is,
It was set to about 5 seconds and about 3 seconds. CA coated on one side of a 0.19 mm thick TFS with epoxy coating applied and baked on both sides.
Welded a thermocouple to make it possible to track temperature changes, applied acrylic water-based paint on the other side, placed it on the net of the conveyor so that the coated side was on top, and dried and cured it. .. The peak temperature of TFS measured with a thermocouple was 125 ° C at the outlet of the first half and 24 at the outlet of the second half.
The surface temperature of the coating film was 5 ° C. and was measured immediately after heating with an infrared thermometer.
It was 0 ° C. As a result of observing this sample after cooling, no scratch due to friction with the net was observed in the coating film on the lower surface. Moreover, the pencil hardness of the coating film on the upper surface was 5H, and it was confirmed that the coating film was sufficiently hardened.

[0057]

According to the present invention, an organic polymer coating is applied on a substrate and the coating is heat-treated, but the coated surface to be treated is irradiated with infrared rays having a peak at a wavelength of 2.0 to 4.0 μm. By simultaneously performing the self-heating step for cooling and the cooling step for forcibly cooling the coated substrate, the self-heating due to infrared rays is concentrated on the organic polymer coating to preferentially heat the organic coating, and It is possible to suppress the heating and heating of other portions. According to the present invention, the following effects can be obtained by thus combining the heating of the organic polymer coating by self-heating and the forced cooling of the coated substrate.

(1) It is possible to prevent a portion other than the coating layer, that is, the substrate from being adversely affected by heating. For example, it is possible to prevent the coating film on the opposite surface of the substrate from being softened or from being scratched or sticking. (2) Since forced cooling is performed, when the irradiation of infrared rays is stopped, the coated substrate immediately returns to room temperature, so that the cooling time after heat treatment can be significantly shortened, the overall processing time can be shortened, and the productivity can be improved. be able to. (3) Since self-heating due to the molecular vibration of the organic polymer in the coating is used, the temperature can be strictly controlled, and the coating can be prevented from being overheated, for example, charring or discoloration of printing ink or paint can be prevented. The obtained coating is excellent in various physical properties. (4) Since it is self-heated from within the coating, the solvent and low molecular weight components are efficiently volatilized, and the volatilized solvent, fumes, low molecular weight components, etc. are oxidized on the spot, and these treatments are automatically performed at the same time. To be done. (5) Since infrared irradiation is performed under forced cooling, it is possible to use an infrared source with extremely high irradiation intensity, which enables heating and quenching in a significantly short time, improving workability and improving physical properties. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a side layout view for explaining an example in which the heat treatment method of the present invention is used in a finish varnish coating process on a coated metal plate for can manufacturing.

FIG. 2 is a side view for explaining another embodiment of the baking process of the present invention.

FIG. 3 is a front view of the device of FIG.

[Explanation of symbols]

 A finish varnish coating process B baking process C cooling process 1 coating roller 2 support roller 3 varnish storage tank 4 fan ten roller 5 base coating metal plate 6 finish varnish coating metal plate 7 forced cooled conveyor 8, 8'infrared gas heater 9 Hood 10 Cooling air supply port 11 Heated air exhaust port 12 Finish varnish coating metal plate 13 Conveyor 14 Cooling water spray nozzle 15 Product stack 16 Cooling nozzle 17 Cooling water or cold wind

Claims (6)

[Claims] 1. When heat-treating an organic polymer coating applied on a substrate, the coating surface to be heat-treated radiates infrared rays having a peak at a wavelength of 2.0 to 4.0 μm, and at least one of the coated substrates. A heat treatment method for an organic coating, characterized in that heat treatment is performed while forcibly cooling the surface. 2. The irradiation intensity of infrared rays on the surface is 2 to 2.
The heat treatment method according to claim 1, wherein the coated surface is irradiated with 3 w / cm ² . 3. The heat treatment method according to claim 1, wherein the forced cooling of the coated substrate is performed by blowing cold air. 4. The heat treatment method according to claim 1, wherein the forced cooling of the coated substrate is performed by bringing the opposite surface of the coated substrate into contact with a cooled good thermal conductor. 5. The heat treatment method according to claim 1, wherein the coated substrate to be treated has an organic polymer coating provided on the substrate through a sizing layer which also serves as a heat insulating layer. 6. An infrared ray having a peak at a wavelength of 2.0 to 4.0 μm on the surface of a coating when a coating comprising an organic polymer solution or dispersion is applied on a substrate and the applied coating is dried and cured. Is radiated with relatively low radiant energy to dry the coating film, and then infrared rays having a peak at a wavelength of 2.0 to 4.0 μm are radiated with relatively high radiant energy to the coating surface after drying to cure the coating film. In addition to the above, at least at least one surface of the coated substrate is heated while being forcibly cooled at the stage of curing the coating film.