JPH1133475A - Method for coating metallic sheet with coating material coating granular material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to uniformly form a coating film of a coating material contg. granular materials even if the coating film thickness is small and to surely incorporate the granular materials in the coating material into the coating film. SOLUTION: This roll coater type coating device has four pieces of rolls consisting of a pickup roll 3, a doctor roll 4, a metering roll 5 and an applicator roll 6 at the time of coating a material sheet with the coating material contg. the granular materials by using this roll coater type coating device. The coating weight of the coating material ladled up by the pickup roll 3 is adjusted by passing the coating material in the spacing between the doctor roll 4 rotating naturally relative to the pickup roll 3 and the pickup roll 3. The coating material on the pickup roll 3 is then transferred onto the metering roll 5 rotating reverse from the pickup roll 3 and the coating material on the metering roll 5 is transferred onto the applicator roll 6 rotating reverse from the metering roll 5. The coating material on the applicator roll 6 is thereafter transferred onto the surface of the metallic sheet traveling in the direction reverse from the applicator roll 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a metal plate with a paint containing particulate matter, and more particularly, to a method for coating a metal plate with a paint containing large particulate matter.

[0002]

2. Description of the Related Art Painted metal sheets obtained by coating a steel sheet such as a cold-rolled steel sheet or a plated steel sheet, or a metal sheet such as an aluminum sheet with a coating made of a synthetic resin or the like have excellent corrosion resistance, weather resistance, and a beautiful colored appearance. Because it can be easily obtained, building materials,
Widely used for home appliances and steel furniture.
Generally, a coated metal plate used for these applications is a two-coated metal plate in which a coating thickness of 2 to 7 μm and an overcoat of 6 to 20 μm are applied.

[0003] As a method of manufacturing the coated metal plate at low cost and high efficiency, a continuous coating method using a roll coater type coating apparatus is usually adopted, and two to three coating rolls are provided for the top coating. Painting equipment is used.

[0004] The coating apparatus shown in Fig. 3 is a roll coater type coating apparatus having two coating rolls. In this coating apparatus, paint is pumped up from a paint pan 1 by a pickup roll 3, and the amount of application is adjusted between applicator rolls 6 rotating in the forward direction (hereinafter, natural rotation) with respect to the pickup roll 3, and then the applicator is rotated. The paint on the roll 6 is transferred onto a metal plate 8 supported by a backup roll 7 and running in a direction opposite to the rotation direction of the applicator roll 6, and painted (hereinafter, reverse painting).

According to this coating method, a large number of coated metal plates can be manufactured in a short time. However, when a paint with high viscosity and poor fluidity is used, a roping pattern is generated, and coating with high uniformity of the coating thickness cannot be performed, so that a beautiful appearance with excellent smoothness can be obtained after coating. In addition, there is a problem that the coating film performance such as corrosion resistance and weather resistance is lowered.

[0006] The roping pattern is a streak-like uneven pattern caused by unevenness of the coating thickness generated on the coating surface of the metal plate, and the film thickness (wet film thickness) of the coating generated on the applicator roll 6. Is a coating film defect generated by transferring the non-uniformity to a metal plate as it is.

When a coated metal plate having no roping pattern is required, a roll coater type coating apparatus using three coating rolls as shown in FIG. 4 is used.

In FIG. 4, 1 is a paint pan, 3 is a pickup roll, 4 is a doctor roll, 6 is an applicator roll, 7 is a backup roll, and 10 is a doctor blade. In this device, coating is performed as follows.

The paint pumped up by the pickup roll 3 is partially scraped by a doctor roll 4 rotating in the reverse direction (hereinafter, reverse rotation) with respect to the pickup roll 3 to reduce the amount of the paint on the pickup roll 3. adjust. The scraped paint on the doctor roll 4 is scraped off by the doctor blade 10 and removed from the doctor roll 4. The paint remaining on the pick-up roll 3 is transferred to the applicator roll 6 that is rotating reversely with respect to the pick-up roll 3, and is further transferred from the applicator roll 6 to a metal plate running in a direction opposite to the rotation direction of the applicator roll 6. Transfer the paint to the reverse coating.

The thickness of the coating film is adjusted by adjusting the roll gap between the pickup roll 3 and the doctor roll 4 and adjusting the rotation ratio of each roll. In this coating method, a beautiful painted appearance can be obtained without occurrence of a roping pattern.

In order to improve the design of the appearance by giving a metallic appearance or a low-gloss appearance, or to improve the performance of a coating film such as scratch resistance, it is necessary to add a granular material to the coating material. In recent years, there have been cases where larger particles, for example, aluminum powder having a size of about 100 μm, aggregates such as silica, and particles such as mica are added to the paint. Further, depending on the purpose of addition, a plurality of granules having different sizes may be added.

[0012] A paint containing particulate matter is inferior in roll coating suitability to a paint containing no particulate matter. This tendency becomes more pronounced as the size of the granules increases and as the thickness of the coating decreases. Therefore, in the coating method using the above-described coating apparatus, when a granular material having a size exceeding 80 μm is included, the coating thickness becomes uneven when the coating thickness becomes 13 μm or less, and a beautiful coating appearance is obtained. Can not do.

The following coating methods have been proposed in order to improve the paintability of paints to which particulate matter has been added. (1) Japanese Patent Application Laid-Open No. 57-204267 (Prior Art 1) In a continuous coating apparatus using a reverse roll coater shown in FIG. 5, a paint is formed by a doctor bar 11 installed above a pickup roll 3 and a pickup roll 3. After passing through the gap, a coating film is formed on the pick-up roll 3, and then a part or almost all of the paint on the pick-up roll 3 is transferred to the applicator roll 6 rotating in reverse with respect to the pick-up roll 3. Then, a part or all of the paint on the applicator roll 6 is transferred onto a metal plate surface running in a direction opposite to the rotation direction of the applicator roll 6,
It is described that a smooth and beautiful coating film can be obtained even with a poorly coatable coating containing a high-viscosity paint, an inorganic pigment such as aluminum powder having a particle diameter of 30 μm or more, and an organic pigment such as urethane beads. ing.

(2) Japanese Patent Application Laid-Open No. 62-254869 (Prior Art 2) In a coating apparatus shown in FIG. 6A, a paint in which coarse particles are uniformly dispersed in advance is sprayed with paint spray nozzles 15a to 15a.
15c to coating roll 12, paint supply roll 1
The coating material is supplied by spraying onto the three surfaces, and the coating material roll (wet film thickness) on the coating roll 12 is adjusted by a coating material supply roll 13 which rotates naturally with respect to the coating roll 12, and then the coating material on the coating roll 12 is reversed. The steel strip 8 is painted by painting. In the coating apparatus shown in FIG. 6B, a coating material in which coarse particles are uniformly dispersed in advance is sprayed from a coating spray nozzle 15d onto a contact portion between the coating material supply roll 13 and the film thickness regulation roll 14, and the coating material supply roll is formed. A paint pool is formed between the roll 13 and the film thickness regulating roll 14, and the thickness of the paint on the coating roll 12 is adjusted by the paint supply roll 13 so that the steel strip 8 is painted.

It is described that a predetermined amount of particles can be easily contained in a coating film in a coating material in which coarse particles of several tens of μm are dispersed by this coating method.

[0016]

In the coating method described in the prior art 1, it is impossible to accurately include particulate matter in the coating in the coating film for the following reasons.

Pickup roll 3 and doctor bar 11
Is set in consideration of both the size of the granular material and the thickness of the coating film. In the case of a thin film coating containing large particles, the gap needs to be widened according to the size of the particles,
The thickness of the paint on the pickup roll 3 is increased. In order to transfer the paint of the required film thickness to the applicator roll 6, a part of the paint is transferred to the applicator roll 6 with an interval between the pickup roll 3 and the applicator roll 6, and the remaining paint is adhered to the pickup roll 3. It is necessary to return to paint pan 1. Since the gap between the pick-up roll 3 and the applicator roll 6 is smaller than the gap between the pick-up roll 3 and the doctor bar 11, the proportion of small particles increases in the paint returning to the paint pan 1, while
In the paint transferred to the applicator roll 6, the proportion of large particulate matter increases, so that it is difficult to control the content ratio of the particulate matter in the coating film.

Further, in the case of a high-viscosity paint, the occurrence of roping cannot be completely prevented, and when the low-viscosity paint or the rotation speed of the pickup roll is slow, there is a difficulty in adjusting the film thickness.

The coating method described in Prior Art 2 is intended for low-viscosity paints. In the case of a high-viscosity paint, the coating roll 12 is naturally rotated with respect to the paint supply roll 13, so that there is a problem that the occurrence of a roping pattern is inevitable, and that a coating defect due to bubbles caused by spraying is apt to occur. .

That is, in the coating method described in the above-mentioned prior art, a predetermined granular material contained in the coating is excellent in the uniformity of the coating film thickness and a certain granular material contained in the coating is reliably contained in the coating film. Cannot be obtained.

The present invention has been made in view of such circumstances, and a coating material containing particulate matter has excellent uniformity of the coating film even when the coating film thickness is small, and is added to the coating material. It is an object of the present invention to provide a coating method capable of surely including a granular material in a coating film.

[0022]

The gist of the present invention to solve the above-mentioned problems is that when a paint containing particulate matter is applied to a metal plate using a roll coater type coating apparatus, a pickup roll, a doctor roll, a meta roll, and the like are used. Ring roll, equipped with four rolls consisting of an applicator roll, the amount of paint that has been pumped by the pickup roll, the natural rotation with respect to the pickup roll is adjusted by passing through the gap between the doctor roll and the pickup roll, Transfer the paint on the pickup roll to a reverse rotating metalling roll with respect to the pickup roll, and then transfer the paint on the metalling roll to an applicator roll that reverse rotates with respect to the metalling roll, and then Liver against applicator roll It is a coating method of coating comprising particulates to the metal plate, which comprises transferring the coating on the applicator roll to the metal plate on a surface that travels in the scan direction.

Hereinafter, the operation of the present invention will be described. The thickness of the paint adhered to the pickup roll is related to the gap between the pickup roll and the doctor roll. The roll gap for setting the film thickness (wet film thickness) of the paint adhered to the pickup roll to a predetermined film thickness greatly differs depending on the rotation direction of the doctor roll.

Film thickness of paint adhered to pickup roll
(Wet film thickness) is t _p , paint film thickness adhering to the doctor roll (wet film thickness) is t _D , the roll gap when the doctor roll is reverse rotation with respect to the pickup roll is d _R , and when the natural rotation is natural rotation Roll gap d _N
For simplicity, consider the case where the peripheral speeds of the rolls are the same.

FIG. 1B shows a case where the doctor roll rotates reversely. The paint passing through the gap between the pickup roll 3 and the doctor roll 4
D _R = t _p because only the paint adheres to the surface. Therefore, if the paint is the magnitude comprising particulates in excess of the roll gap d _R, granules size exceeds d _R can not pass through the gap of the both rolls.

FIG. 1A shows that the doctor roll is Natura.
This is the case of the rotation of the robot. Pickup roll 3 and doctor
The paint passing through the gap between the rolls 4 is a pickup roll
Paint that adheres to the doctor roll
That is, d_N= T _p+ T_Dbecome. Sand
When the doctor roll is in natural rotation,
Roll spacing can always be made larger than in the case of base rotation.

Therefore, when the doctor roll is in natural rotation, larger particles can pass through the gap between the two rolls than in the case of reverse rotation. The same can be said for different roll peripheral speeds.

The paint adhered to the pickup roll is sequentially transferred to a metal plate via a metalling roll and an applicator roll. Therefore, the film thickness of the metal plate to a predetermined thickness, it is necessary to adjust the thickness t _p of the paint adhering to the pickup roll film a predetermined thickness corresponding to the thickness of the coated steel sheet.

The thickness t _p of the paint adhering to the pick-up roll, in addition to the roll gap d _N of the pickup roll 3 and the doctor roll 4 described above can be performed by adjusting the rotation ratio of both rolls. Therefore, in consideration of the size of the granules is added to the coating first decide the roll gap d _N, then it may be the film thickness t _p to a desired thickness by adjusting the roll speed ratio. Even if the roll rotation ratio is changed, the composition of the paint pumped up by the pickup roll,
The composition of the paint adhered to the pickup roll does not change. Therefore, the particulate matter added to the paint can be reliably contained in the coating film.

Further, the paint adhered on the pickup roll is repeatedly transferred to a metalling roll, an applicator roll, and a metal plate, so that the thickness of the paint is made uniform on the metal plate sequentially. There is no roping pattern in the coating.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to a coating apparatus shown in FIG.

In FIG. 2, 1 is a paint pan, 3 is a pickup roll, 4 is a doctor roll, 5 is a metering roll, 6 is an applicator roll, and 7 is a backup roll. The direction of rotation of each roll is indicated by an arrow in the figure.
The doctor roll 4 rotates naturally with respect to the pickup roll 3, the metering roll 5 reverse rotates with respect to the pickup roll 3, the applicator roll 6 reverse rotates with respect to the metering roll 5, and the metal plate 8 rotates with the applicator. The vehicle runs in a direction opposite to the rotation direction of the roll 6. The metal plate 8 is supported by the backup roll 7.

Pickup Roll 3 and Doctor Roll 4
Roll gap d _N of is the gap does not hinder the passage of granules was added to the paint. This gap is preferably 90% or more of the maximum size of the granular material. The rotation speed of each roll is appropriately determined according to the application amount, the traveling speed of the metal plate, and the like.

The gap between the pick-up roll and the doctor roll and the rotation speed of each roll are, for example, to increase the thickness of the coating film, increase the gap between the applicator roll and the doctor roll, or rotate the applicator roll relative to the running speed of the metal plate. Increase the speed or, if necessary, reduce the rotation speed of the doctor roll.

When the thickness of the coating film is reduced, the gap between the applicator roll and the doctor roll is reduced or the rotation of the applicator roll with respect to the traveling speed of the metal plate within a range that does not hinder the passage of the particulate matter added to the paint. Reduce the speed or, if necessary, increase the rotation speed of the doctor roll.

The paint containing the particulate matter pumped up by the pip-up roll 3 adheres to the pickup roll 3 in a predetermined thickness without being changed in composition by the doctor roll 4.

The coating material containing the particulate matter adhered on the pickup roll 3 is then transferred to the metalling roll 5 and the applicator roll 6 sequentially, and then transferred to the metal plate 8, and the granular material is placed on the surface of the metal plate 8. To form a required coating film having excellent smoothness.

The present invention particularly relates to the addition of a granular material containing a granular material having a size of 80 μm or more to a thin coated metal plate having a coating thickness of 7 to 13 μm, which has been widely used in the past, for example, 30 μm. When obtaining a coated steel sheet to which a granular material having a size in the range of １００100 μm is added, that is, the size in the paint is 30 to 1
This is effective when a coated metal plate having a coating thickness of 7 to 13 μm is manufactured using a coating material to which particles having a size of 00 μm are added. In this case, the roll gap d _N = 90 to 140 μm,
Roll peripheral speed ratio: doctor roll peripheral speed / pickup roll peripheral speed = 0.1 to 0.3, metering roll peripheral speed / pickup roll peripheral speed = 0.8 to 1.0, applicator roll peripheral speed / metering Roll peripheral speed = 1.0-1.
3. Metal plate traveling speed / applicator roll peripheral speed = 0.
It is preferably 5 to 0.7.

In the above coated steel sheet, the paint used is not particularly limited. For example, as the base resin, a high-viscosity paint such as PTFE (tetrafluoroethylene) having excellent heat resistance and non-adhesiveness can be applied. There is no particular limitation on the granular material to be added.

The material of the roll used for coating is not particularly limited. However, if a rubber roll is used as the applicator roll, a uniform coating film can be obtained due to the elasticity of the rubber even if the metal plate has a defective shape. Is preferred.

[0041]

EXAMPLE A hot-dip galvanized steel sheet having a thickness of 0.60 mm and a width of 914 mm was subjected to water washing, degreasing, hot water washing, and drying treatment in a conventional manner, and then a 6 μm-thick primer layer was formed. A top coat was applied thereon using a paint having a component composition shown in Table 1 to produce a coated steel sheet having a 7 µm-thick top coat.

[0042]

[Table 1]

The appearance of the roping pattern was examined by visually observing the appearance of the coated steel sheet obtained as described above, and the state of the particulate matter was examined by observing the coating film under a microscope.

In the present invention example, the top coat was applied by the method specified in the present invention using the coating apparatus shown in FIG. For comparison, a doctor roll was reverse-rotated with respect to a pickup roll in the coating apparatus shown in FIG. 2 to perform coating (Comparative Example 1 and Comparative Example 2).

Table 2 shows the coating conditions. In Comparative Example 2, the roll gap between the pickup roll and the doctor roll was set to 70 μm, which is smaller than that of the invention, so that the roping pattern was reduced as much as possible and a coating film having a good appearance was obtained.

Table 3 shows the results of the investigation.

[0047]

[Table 2]

[0048]

[Table 3]

The coated steel sheet of the present invention has no roping pattern, and the size of the granular material contained in the coating film is not changed from that of the coating material before coating.

On the other hand, the coated steel sheet of Comparative Example 2 has a narrow roll gap between the pickup roll and the doctor roll, and therefore, as shown in FIG. 1 (B), large granular materials cannot be passed through the gap between both rolls and are clogged. . As a result, band-like coating unevenness caused by clogging of the granular material occurred. Also, no large particles exceeding 70 μm are contained in the coating film.

In the case of the coated steel sheet of Comparative Example 1, in addition to the occurrence of a somewhat conspicuous roping pattern, a light streaky coating unevenness due to a small but large granular material being unable to pass through the gap between the two rolls was generated. did.

[0052]

According to the present invention, a coating containing large granular materials has excellent uniformity of the coating film even when the coating film thickness is small, and the granular materials added to the coating material are surely applied. A coated steel sheet that can be contained in the film can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the operation of the present invention.

FIG. 2 is a view showing a coating apparatus for explaining an embodiment of the present invention.

FIG. 3 is a diagram showing a metal plate coating apparatus using two conventional coating rolls.

FIG. 4 is a view showing a conventional metal plate coating apparatus using three coating rolls.

FIG. 5 is a view showing a conventional coating apparatus using a doctor bar.

FIG. 6 is a view showing a conventional coating apparatus for coating by spraying a paint from a nozzle.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 paint pan 2 paint 3 pickup roll 4 doctor roll 5 metalling roll 6 applicator roll 7 backup roll 8 metal plate 9 granular material 10 doctor blade 11 doctor bar 12 coating roll 13 paint adjustment roll 14 film thickness regulation roll 15a, 15b, 15c , 15d paint spray nozzle

Claims (1)

[Claims] When coating a metal plate with a coating material containing particulate matter using a roll coater type coating apparatus, the coating apparatus includes four rolls including a pickup roll, a doctor roll, a metalling roll, and an applicator roll. Adjust the amount of paint that has been pumped up by passing the gap between the doctor roll and the pickup roll that rotates naturally with respect to the pickup roll,
Next, transfer the paint on the pickup roll to a reverse rotating metalling roll with respect to the pickup roll, and then transfer the paint on the metalling roll to an applicator roll that reverse rotates with respect to the metalling roll, A method for applying a paint containing a particulate matter to a metal plate, wherein the paint on the applicator roll is transferred onto a surface of a metal plate traveling in a reverse direction to the applicator roll.