JP2022167225A - Method for manufacturing coated metal plate - Google Patents

Abstract

To provide a method for manufacturing a coated metal plate which easily bakes a coated film onto a metal substrate.SOLUTION: A method for manufacturing a coated metal plate includes a coating step, a first heating step, and a second heating step. The coating step is a step of coating a coating material 2 containing a resin, a pigment and a solvent onto a surface of a metal substrate 1. The first heating step is a step of heating the metal substrate 1 by heat conduction after the coating step. The second heating step is a step of blowing hot air to the coating material coated onto the surface of the metal substrate 1, and heating the coating material, after the first heating step.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to a method for manufacturing a coated metal sheet that can be used for building materials and the like.

Conventionally, there has been known a method for producing a flow-pattern coated metal plate (see, for example, Patent Document 1). This flow pattern coated metal plate manufacturing method is carried out by rotating the coating roll of a roll coater in the forward direction with respect to the conveying direction of the metal substrate, applying a high-viscosity vinyl chloride resin coating composition, and then baking. It is. The metal substrate onto which the coating composition has been transferred by the coating roll is continuously conveyed and undergoes the steps of drying, baking and cooling to become a coated metal plate.

JP-A-10-245519

In the conventional method for manufacturing a coated metal sheet, the metal substrate to which the coating composition has been transferred by the coating roll is generally transported into a furnace and the surface is heated by hot air to dry and bake. was taking place.

However, when the surface of the coating composition is heated first, the surface of the coating composition cures first, making it difficult for the solvent inside the coating composition to evaporate, making it difficult to bake the coating composition. rice field.

The present disclosure has been made in view of the conventional problems described above, and an object thereof is to provide a method of manufacturing a coated metal sheet that facilitates baking of a coating film onto a metal substrate.

In order to solve the above problems, a method for manufacturing a coated metal sheet according to one aspect of the present disclosure includes a coating step, a first heating step, and a second heating step. The coating process is a process of coating the surface of the metal substrate with a paint containing a resin, a pigment and a solvent. The first heating step is a step of heating the metal substrate by thermal conduction after the coating step. The second heating step is a step of heating the paint by blowing hot air onto the paint applied to the surface of the metal substrate after the first heating step.

In one aspect of the method for manufacturing a coated metal plate according to the present disclosure, in the second heating step, before the surface of the paint starts to harden, the metal substrate is heated by heat conduction in the first heating step, Solvent in the back of the paint surface evaporates easily, making it easy to bake the paint film onto the metal substrate.

FIG. 1 is a schematic configuration diagram of an apparatus used in the method for manufacturing a coated metal sheet according to the first embodiment. FIG. 2 is a schematic configuration diagram of an apparatus used in the method for manufacturing a coated metal sheet according to the second embodiment. FIG. 3 is a schematic configuration diagram of an apparatus used in a method for manufacturing a coated metal sheet according to a modification.

The present disclosure relates to a method for producing a coated metal plate that can be used as a building material, etc. More specifically, the present disclosure relates to a method for producing a coated metal plate that can be used as a building material, etc., more specifically, after applying a paint containing a resin, a pigment, and a solvent to the surface of a metal substrate, the solvent is evaporated to remove the pigment from the metal substrate. It relates to a method for manufacturing a coated metal plate formed by baking.

Hereinafter, a method for manufacturing a coated metal sheet according to the present disclosure will be described based on embodiments. The embodiment of the method for manufacturing a coated metal sheet according to the present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the technical idea of the present disclosure.

A method for manufacturing a coated metal sheet according to the first embodiment will be described with reference to FIG.

A method for manufacturing a coated metal sheet includes a coating step, a first heating step, and a second heating step. The coating process has a process of coating the surface of the metal substrate 1 with a paint 2 containing a resin, a pigment and a solvent.

The metal substrate 1 used in this embodiment is not particularly limited, but examples thereof include an aluminum plated steel plate, a zinc plated steel plate, an aluminum-zinc plated steel plate, a stainless steel plate, and the like. Moreover, as such a metal substrate 1, a long substrate can be used.

In applying the coating to the metal substrate 1, the metal substrate 1 is fed out from a payoff reel (not shown) on which the long metal substrate 1 is wound in a coil shape, and is continuously transported while being subjected to various treatments and coating. This can be done by a continuous processing step in which the subsequent metal substrate 1 is cut to the desired size or coiled again without being cut.

Prior to such a coating process on the metal substrate 1, chemical conversion treatments such as chromate treatment and zinc phosphate treatment, and pretreatment such as removal of dirt such as oil and dust on the surface of the metal substrate 1 are performed as necessary. This may be followed by a painting step.

In addition, prior to applying the outer layer coating to the metal substrate 1 by applying the paint 2 (topcoat paint) for forming the topcoat film on the surface of the metal substrate 1, an appropriate undercoat film is formed as necessary. Alternatively, an appropriate intermediate coating film can be formed.

When forming an undercoat film, the paint (undercoat) may be thermosetting resin such as epoxy resin, epoxy urethane resin, polyester resin, extender pigment such as titanium oxide, fine powder clay, calcium carbonate, etc. An epoxy resin-based paint in which a rust pigment or the like is dispersed can be used. As the anticorrosion pigment, for example, one mainly containing chromate such as strontium chromate and calcium chromate can be used. In the undercoat coating, the undercoat paint having such a composition is applied to one surface of the metal substrate 1, and in some cases, the other surface of the metal substrate 1 is also coated with the undercoat paint. Also, the other surface of the metal substrate 1 may be coated with a backing paint having a composition different from that of the undercoat. The application of the undercoat paint and the backcoat paint can be carried out by an appropriate coating device comprising dip coating, spray coating, brush coating, roll coater, air knife, electrostatic coating, and the like.

After applying the undercoat paint, the undercoat paint can be cured on the metal substrate 1 by baking or the like to form an undercoat film.

The thickness of the undercoat film is not particularly limited and may be set appropriately, but is preferably in the range of 3 to 25 μm.

In addition, when forming an intermediate coating film, as the paint (intermediate coating), an appropriate liquid paint for precoating can be used. For example, polyester, urethane, alkyd, fluorine, acrylic , a vinyl chloride-based paint, or the like can be used. Application of the intermediate coating can be carried out by an appropriate coating device consisting of immersion, spraying, brush coating, roll coater, curtain coater, air knife, electrostatic coating, etc. After applying the intermediate coating, An intermediate coating film can be formed by curing the undercoat paint on the metal substrate 1 by baking or the like. The thickness of the intermediate coating film at this time is appropriately adjusted, but it is preferable that the dry coating film thickness is 5 to 40 μm, particularly 10 to 30 μm. By forming such an intermediate coating film, it is possible to improve the coating film performance such as corrosion resistance, weather resistance, chemical resistance, and hiding property of the coated metal plate within the range of the coating film thickness that can be applied by the paint. It is particularly suitable when the coated metal plate is used as an exterior building material.

In applying the outer layer coating to the metal substrate 1, as the paint 2, an appropriate liquid paint for pre-coating can be used in the same manner as the above intermediate paint. paints such as acrylic, vinyl chloride, etc. can be used.

Moreover, as the coating material 2, one containing an appropriate pigment in a solvent is used. Examples of such pigments include titanium oxide, carbon black, iron oxide yellow, iron oxide red (red iron oxide), aluminum flakes, mica flakes, colored glass flakes, and organic blue (phthalocyanine blue). The blending ratio of such pigments in the paint 2 can be set within an appropriate range, but is generally preferably 0.1 to 80% by weight, particularly preferably 0.5 to 50% by weight.

In particular, by including metal powder such as aluminum powder, nickel powder, copper powder, etc. as a pigment in the coating material 2, it is possible to impart a metallic appearance to the coating film. The metal powders also include metal-inorganic composite powders such as metal-coated glass powders.

Also, the average particle size of the metal powder is preferably in the range of 5 to 80 μm, particularly in the range of 10 to 30 μm. If the particle size is too large, the coating properties of the coating material 2 are deteriorated, and uniform coating becomes difficult when using a roll coater. On the other hand, if the particle size is too small, it is not possible to impart a sufficient metallic effect to the outer layer coating film made of the pigment baked on the metal substrate 1, and if scale-like metal powder is used, its arrangement will be disturbed. In some cases, the change in light reflectivity due to is not sufficiently exhibited.

When such metal powder is used, it is preferable that the content of the powder in the paint 2 is in the range of 1 to 15% by weight.

In applying the coating material 2, after supplying the coating material 2 to the peripheral surface of the coating roll 3 while rotating it, the coating material 2 is applied by bringing the coating material 2 on the peripheral surface of the coating roll 3 into contact with the surface of the metal substrate 1, Next, this metal substrate 1 is conveyed toward the heating roll 71 .

In the example shown in FIG. 1, a pick-up roll 5 is arranged above a paint pan 4 in which paint 2 is stored. The pick-up roll 5 is arranged so that its lower part is dipped into the paint 2 in the paint pan 4 . Also, the pickup roll 5 is arranged so that the peripheral surface of the coating roll 3 is in contact with the peripheral surface of the pickup roll 5 . A long metal substrate 1 is conveyed between the coating roll 3 and a backup roll 6 arranged to face the coating roll 3 . At this time, the paint 2 is supplied to the peripheral surface of the pickup roll 5 by rotating the pickup roll 5 , and the paint 2 supplied to the peripheral surface of the pickup roll 5 is supplied to the peripheral surface of the coating roll 3 . Furthermore, by rotating the coating roll 3, the coating material 2 is supplied and applied to the surface of the metal substrate 1. As shown in FIG. Metal substrate 1 coated with paint 2 is conveyed toward heating roll 71 . Here, the direction of rotation of the coating roll 3 may be forward or reverse with respect to the conveying direction of the metal substrate 1, but in the example shown in FIG. .

The first heating step is a step of heating the metal substrate 1 by thermal conduction after the coating step. The heating of the metal substrate 1 in the first heating step is performed without the paint 2 applied to the surface of the metal substrate 1 . Heating of the metal substrate 1 in the first heating step is performed by the metal substrate heating device 7 .

The metal substrate heating device 7 does not indirectly heat the metal substrate 1 through the paint 2 , but directly heats the metal substrate 1 without the paint 2 . The metal substrate heating apparatus 7 of this embodiment has a heating roll 71 with which the metal substrate 1 contacts. The heating roll 71 is made of metal and has a heater 70 inside, and the heating roll 71 itself is heated by the heater 70 inside. The heated heating roll 71 heats the contacting metal substrate 1 by thermal conduction. The paint 2 is not directly heated by the heating roll 71 but is heated by heat conduction from the metal substrate 1 .

The heating roll 71 does not have to be made of metal as long as it is made of a material having a predetermined thermal conductivity. Various heaters including an electric heater can be appropriately used as the heater 70 for heating the heating roll 71 itself. Moreover, the heating roll 71 may not have the heater 70 inside, and may be heated by an external heat source.

In the first heating step, the paint 2 applied to the surface of the metal substrate 1 is not directly heated by the heating roll 71 . Therefore, the surface of the paint 2 applied to the surface of the metal substrate 1 (that is, the surface opposite to the side in contact with the surface of the metal substrate 1) is less likely to be heated, and hardening of the surface of the paint 2 is less likely to proceed.

The paint 2 is heated from the side in contact with the surface of the metal substrate 1 due to heat conduction from the metal substrate 1 . Therefore, the solvent inside the heated paint 2 easily escapes into the atmosphere from the surface of the paint 2 that has not yet cured, and evaporates easily from the paint 2 .

After the first heating process as described above, the second heating process is performed. The second heating step is a step of heating the paint 2 by blowing hot air onto the paint 2 applied to the surface of the metal substrate 1 . In this embodiment, the heating of the paint 2 in the second heating step is performed by the heating furnace 8 . The heating of the coating material 2 in the second heating step is widely and generally performed as disclosed in Patent Document 1, and detailed description thereof will be omitted.

In the second heating step, the surface of the paint 2 applied to the surface of the metal substrate 1 is directly heated. In the second heating step, the surface of the paint 2 is heated, and curing of the surface of the paint 2 proceeds. As the curing of the surface of the paint 2 progresses, the solvent inside the paint 2 becomes less likely to escape from the surface of the paint 2 and evaporate from the paint 2, but the evaporation of the solvent inside the paint 2 progresses in the first heating step. Therefore, the amount of solvent remaining inside the paint 2 is small in the second heating step, and there is no problem.

Through the first heating step and the second heating step, the solvent contained in the paint 2 is evaporated from the paint 2, the pigment is baked on the metal substrate 1, and an outer layer coating film is formed on the metal substrate 1. The outer layer coating film formed on the metal substrate 1 has a lower residual solvent content than the conventional example, and is in a good dry state.

Next, the manufacturing method of the coated metal plate of 2nd embodiment is demonstrated based on FIG. The manufacturing method of the coated metal sheet of the second embodiment is mostly the same as the manufacturing method of the coated metal sheet of the first embodiment. For this reason, explanations that overlap with the first embodiment will be omitted, and mainly different parts will be explained.

In the manufacturing method of the coated metal sheet of the first embodiment, the metal substrate heating device 7 has the heating roll 71 . On the other hand, in the manufacturing method of the coated metal sheet of the second embodiment, the backup roll 6 also serves as the metal substrate heating device 7 . The backup roll 6 is made of metal and has a heater 70 inside, and the backup roll 6 itself is heated by the heater 70 inside. The heated backup roll 6 heats the contacting metal substrate 1 by thermal conduction. The paint 2 is not directly heated by the backup roll 6, but is heated by heat conduction from the metal substrate 1. FIG.

The backup roll 6 does not have to be made of metal as long as it is made of a material having a predetermined thermal conductivity. Various heaters including an electric heater can be appropriately used as the heater 70 for heating the backup roll 6 itself. Moreover, the backup roll 6 may not have the heater 70 inside, and may be heated by an external heat source.

Also in the second embodiment, in the first heating step, the paint 2 applied to the surface of the metal substrate 1 is not directly heated. Difficult to harden. As a result, the solvent inside the heated coating material 2 easily escapes into the atmosphere from the surface of the coating material 2 that has not yet cured, and evaporates easily from the coating material 2 .

The outer layer coating film formed through the first heating step and the second heating step has a lower residual solvent content than the conventional example, and is in a good dry state.

In addition, in the second embodiment, the backup roll 6 also serves as the metal substrate heating device 7 , so there is no need to dispose a large-scale device separately as the metal substrate heating device 7 .

Next, the manufacturing method of the coated metal plate of 3rd embodiment is demonstrated. In addition, the manufacturing method of the coated metal plate of 3rd embodiment is the same as the manufacturing method of the coated metal plate of 1st embodiment and 2nd embodiment for the most part. For this reason, explanations overlapping those of the first embodiment and the second embodiment will be omitted, and mainly different parts will be explained.

The method of manufacturing a coated metal sheet according to the first embodiment and the second embodiment does not include the step of heating the metal substrate 1 before the coating step. On the other hand, the manufacturing method of the coated metal sheet of the third embodiment further includes a pre-coating heating step of heating the metal substrate 1 by thermal conduction before the coating step.

In the third embodiment, the metal substrate heating device 7 has a heating roll (not shown) with which the metal substrate 1 contacts upstream of the backup roll 6 . Like the heating roll 71, this heating roll is made of metal and has a heater inside, and the heating roll itself is heated by the internal heater. The heated heating roll heats the contacting metal substrate 1 by thermal conduction.

Thus, by providing the pre-painting heating step of heating the metal substrate 1 by heat conduction before the painting step, it becomes easier to apply the highly viscous paint 2 in the painting step, and the first heating step and the second heating step are performed. It becomes easy to shorten the heating time (drying time) in the second heating step. Further, when the temperature of the metal substrate 1 before coating is set to 140° C. or less, the paint 2 can be made to have a low viscosity without increasing the amount of solvent contained in the paint 2 .

Next, a method for manufacturing a coated metal plate as a modified example will be described with reference to FIG. In addition, the manufacturing method of the coated metal plate as a modified example is mostly the same as the manufacturing method of the coated metal plate of the first embodiment. For this reason, explanations that overlap with the first embodiment will be omitted, and mainly different parts will be explained.

In the manufacturing method of the coated metal sheet of the first embodiment, the metal substrate heating device 7 has the heating roll 71 . On the other hand, in the manufacturing method of the coated metal plate as a modified example, the metal substrate heating device 7 is composed of an electromagnetic induction heating device 72 . The electromagnetic induction heating device 72 heats the metal substrate 1 by induction heating. Since the heating roll 71 is not arranged in the modified example, the metal substrate 1 is conveyed from the backup roll 6 toward the heating furnace 8 . The electromagnetic induction heating device 72 is arranged between the backup roll 6 and the heating furnace 8 and heats the metal substrate 1 transported from the backup roll 6 toward the heating furnace 8 by electromagnetic induction heating.

Also in the modified example, since the paint 2 applied to the surface of the metal substrate 1 is not directly heated in the first heating step, the surface of the paint 2 is difficult to be heated, and the surface of the paint 2 is hardened. hard to progress. As a result, the solvent inside the heated coating material 2 easily escapes into the atmosphere from the surface of the coating material 2 that has not yet cured, and evaporates easily from the coating material 2 .

The outer layer coating film formed through the first heating step and the second heating step has a lower residual solvent content than the conventional example, and is in a good dry state.

In addition, in the modified example, since the metal substrate heating device 7 is composed of the electromagnetic induction heating device 72, there is no need to arrange a device such as a roll in the conveying path of the metal substrate 1, and the metal substrate can be heated as compared with the conventional example. There is no need to drastically change the transport path of 1.

Demonstration experiments were conducted on the manufacturing method of the coated metal sheet of the present disclosure, which will be described below.

<Steel plate>
A 0.35 mm thick hot-dip 55% aluminum-zinc-magnesium alloy plated steel sheet (SGL manufactured by Nippon Steel Sheet Co., Ltd.) is coated with 50 g / m Coat at a basis weight of ² .

<Undercoat>
A primer (model number: P667S, manufactured by Nippon Paint Industrial Coatings Co., Ltd.) is applied at a basis weight of 4.8 g/m ² and baked at 200° C. for 30 seconds to form an undercoat film.

<Outer layer paint>
As paint 2 (Kansai Paint Co., Ltd., model number: GHK01), there are two types: a low-viscosity paint with a paint viscosity of 60 sec (Ford cup, 20°C) and a high-viscosity paint with a paint viscosity of 180 sec (Ford cup, 20°C). are applied to the metal substrate 1 respectively.

<Production of evaluation test piece>
First, a plated steel sheet coated with coating-type chromate is prepared.

Next, the prepared plated steel sheet is coated with a primer and dried to form the metal substrate 1 .

Next, the paint 2 is overcoated on the metal substrate 1 . When the top coat film is a multi-layer coating film having two or more layers, the top coat process of applying the paint 2 to the metal substrate 1 is repeated.

<Examples and Comparative Examples>
Examples are a total of 10 examples of numbers 1 to 5 and 11 to 15, and comparative examples are a total of 6 examples of numbers 6 to 10 and 16. Examples 1 to 5, examples 11 to 15, and a comparative example are described below, respectively. Described as 6 to 10, 16.

Examples 1 to 5 and Comparative Examples 6 to 9 are examples that do not include a pre-painting heating step as in the first and second embodiments, and Comparative Examples 10, 11 to 15 and Comparative Example 16 are , is an example provided with a pre-coating heating step as in the third embodiment.

Further, Examples 1 to 5 and Comparative Examples 6 to 9 are examples in which a low-viscosity paint having a paint viscosity of 60 sec (Ford cup, 20° C.) was used as the paint 2. Comparative Example 10, Examples 11 to 15 and Comparative Example 16 is an example using a high-viscosity paint having a paint viscosity of 180 sec (Ford cup, 20° C.).

Further, Comparative Examples 6 to 9 are examples in which the first heating step is not provided.

Other test conditions and evaluation results are shown in [Table 1].

<Evaluation results>
As evaluation of appearance, the presence or absence of "armpits" was evaluated. A "waki" is a coating film defect that occurs when the solvent contained in the coating material 2 evaporates and escapes into the atmosphere during the drying process of the coating material 2 . This tends to occur when the surface layer of the topcoat film formed by drying the paint 2 hardens faster than the inside of the topcoat film. A case where no “popping” could be visually found on the surface of the overcoating film was evaluated as “good (good)”, and a case where “popping” could be found was evaluated as “x (poor)”.

In addition, the presence or absence of "roughness" was evaluated as the appearance evaluation. The "gritty" feeling means the feeling when palpating the surface of the overcoating film. Macroscopically, this cannot be recognized as "waki", but microscopically, it is one of the coating film defects that are formed when the solvent evaporates from the paint 2 and escapes into the atmosphere, similar to "waki". The less "gritty" feeling, the more beautiful the appearance of the top coat film. When the surface of the topcoat film is palpated directly with a finger, the case where "roughness" is not recognized is rated as "○ (good)", and the case where "roughness" is recognized is rated as "X (bad)". and

Moreover, the presence or absence of "roping" was evaluated as an evaluation of appearance. "Roping" is a phenomenon in which the thickness of the topcoat film changes in the width direction of the strip (metal substrate 1) like a Sine curve. It looks like there is a "streak" in the direction of travel of the strip. In the metal coating industry, these defects are called roping, ribbing, or roll marks. The evaluation of roping was performed using high viscosity paint 2, which tends to cause roping.

The surface appearance of the topcoat film in Examples 1-5 is superior to that in Comparative Examples 6-9. In addition, in Examples 5 and 6, the total heating time after coating the paint 2 was the same at 20 (sec), but not only the appearance but also the resistance of the top coat film to processing and boiling water Example 5 was superior to Comparative Example 6. As for the reason for this, it is presumed that the fact that the removal of the solvent from the coating material 2 in the first heating step due to heat conduction is promoted has brought some effect beyond the appearance improvement in the formation of the top coat film. The workability is a method (JIS K 3312 normal temperature 20 ° C) for measuring the limit of bending a steel plate coated with a topcoat film by 180 °. 1, 2, 3, . . . ). The number of spacers that can be sandwiched is 6T (6), which is smaller than that of 8T (8). Boiling water resistance is obtained by scratching the top coating film with a cutter, immersing it in boiling water for 5 hours, taking it out, and evaluating the adhesion of the top coating film using a cellophane tape. If peeling of the top coat film occurred with the cellophane tape, it was judged as "x (bad)", and if peeling did not occur, it was judged as "o (good)".

Examples 11 to 15 and Comparative Example 16 are all examples including a pre-painting heating process, but by changing the conditions of the plate temperature (metal substrate 1 temperature) in the pre-painting heating process, the presence or absence of "popping" and The presence or absence of "roping" was evaluated in addition to the feeling of "roughness".

As shown in Examples 11 to 15, when the heating conditions in the pre-coating heating step were appropriate, roping did not occur and good surface appearance was exhibited. On the other hand, when the heating temperature in the pre-painting heating step is low as in Comparative Example 10, roping occurs with the high-viscosity paint 2 . Conversely, if the heating temperature in the pre-painting heating step is too high, many defects in the topcoat film occur as in Comparative Example 16, and the surface of the topcoat film does not have a good appearance.

In the above-described first embodiment, second embodiment, and modified example, the paint 2 is blown with hot air in the second heating step, but the paint 2 is blown with hot air in the second heating step. It doesn't have to be. That is, in the above-described embodiments and modifications, prior to applying the coating material 2 to the surface of the metal substrate 1, the undercoat coating film and the intermediate coating film were formed. It is not necessary to form a coating film and an intermediate coating film. In this case, the hot air is blown in the second heating step to the same paint as the paint 2 in the first embodiment, the second embodiment, and the modification applied to the surface of the metal substrate 1 .

As is clear from the first embodiment, the second embodiment, and the modifications described above, the method for manufacturing a coated metal sheet according to the first aspect includes a coating step, a first heating step, and a second heating step. , provided. The coating process is a process of coating the surface of the metal substrate 1 with the paint 2 containing resin, pigment and solvent. The first heating step is a step of heating the metal substrate 1 by thermal conduction after the coating step. The second heating step is a step of heating the paint 2 by blowing hot air onto the paint 2 applied to the surface of the metal substrate 1 after the first heating step.

According to the first aspect, in the first heating step, since the paint 2 applied to the surface of the metal substrate 1 is not directly heated, the surface of the paint 2 applied to the surface of the metal substrate 1 is difficult to be heated, and hardening of the surface of the paint 2 is difficult to proceed. In addition, since the paint 2 is heated from the side in contact with the surface of the metal substrate 1, the solvent inside the heated paint 2 easily escapes into the atmosphere from the surface of the paint 2 that has not yet cured. Evaporation from the paint 2 proceeds easily. Through the first heating process and the second heating process, the solvent contained in the coating material 2 is evaporated from the coating material 2, and the outer layer coating film is baked on the metal substrate 1. The coating film formed on the metal substrate 1 has a low residual solvent content and is in a good dry state.

The second aspect can be realized by a combination with the first aspect. In the second mode, in the first heating step, the metal substrate 1 is heated by heat conduction via the heating roll 71 with which the metal substrate 1 is in contact.

According to the second aspect, the metal substrate 1 can be heated by a roll (heating roll 71 ) generally installed on the transport path of the metal substrate 1 .

The third aspect can be realized by a combination with the first or second aspect. The third aspect further includes a pre-painting heating step of heating the metal substrate 1 by thermal conduction before the painting step.

According to the third aspect, it becomes easier to shorten the heating time (drying time) in the first heating step and the second heating step.

REFERENCE SIGNS LIST 1 metal substrate 2 paint 3 application roll 4 paint pan 5 pickup roll 6 backup roll 7 metal substrate heating device 70 heater 71 heating roll 72 electromagnetic induction heating device 8 heating furnace

Claims (3)

A painting process of applying a paint containing a resin, a pigment and a solvent to the surface of the metal substrate;
After the coating step, a first heating step of heating the metal substrate by thermal conduction;
After the first heating step, a second heating step of blowing hot air onto the paint applied to the surface of the metal substrate to heat the paint;
A method of manufacturing a painted metal plate comprising: 2. The method for producing a coated metal sheet according to claim 1, wherein in said first heating step, said metal sheet is heated by heat conduction via a heating roll with which said metal sheet is in contact. 3. The method for producing a coated metal sheet according to claim 1, further comprising a pre-painting heating step of heating the metal substrate by thermal conduction before the painting step.

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