JP5396727B2 - Roll coating method and roll coating apparatus - Google Patents

Description

  The present invention relates to a roll coating method and a roll coating apparatus for performing a thin film coating process continuously on a long base material such as a steel strip using a roll coating apparatus.

  Conventionally, in order to impart performance such as corrosion resistance, workability, aesthetics, insulation, etc. to a continuously running base material (for example, a steel strip), various coating films are formed on the surface of the base material. Yes. As this processing method, a roll coater (roll coating apparatus) is generally used, and a two-roll coater using two rolls or a three-roll coater using three rolls is widely used. In particular, the three-roll coater is a mainstream coating method because it has excellent controllability of the coating film thickness and has a relatively beautiful surface appearance.

  As shown in FIG. 2, this type of coating apparatus (three-roll coater) includes a pickup roll 4 that draws up the coating liquid 3 from the coater pan 2 that is filled with the coating liquid, and a coating liquid amount that is pumped up by the pickup roll 4. And a applicator roll 6 for transferring the adjusted coating liquid amount from the pickup roll 4 to the steel strip.

  The rotation direction of each roll may be in the vicinity of the rolls, or in the case of natural rotation that rotates in the same direction at the close point, and in reverse rotation that rotates in the opposite direction. Since it is easy to obtain a coating film surface having a uniform film thickness along the surface unevenness of the substrate, the surface of the substrate has unevenness, and particularly when the uniform film thickness along the surface unevenness is desired, In many cases, reverse rotation is performed between the substrates 1. The applicator roll 6 is often a rubber roll in which rubber is lined on a steel roll so as not to damage the surface of the substrate 1.

In recent years, from the viewpoint of improving functionality, it has been required to reduce the thickness of the coating film so that the coating thickness after drying is less than 0.1 μm. When applied to a substrate with a roll coater, the wet film thickness after application is generally about 5 to 10 μm, and in order to make the film thickness after drying less than 0.1 μm, the dilution rate is increased. Although it is necessary, the surface tension increases due to the increase in the dilution rate, so that the wettability with the base material is deteriorated, and scumming easily occurs. Therefore, in order to reduce the coating thickness, it is necessary to reduce the thickness at the time of application to the substrate in a liquid state. As a thin film application method for that purpose, a micro gravure method using a small-diameter gravure roll (for example, Patent Document 1) and a die coater system (for example, Patent Document 2) are known. In the micro gravure method, it is possible to reduce the coating thickness to less than 3 μm and to a minimum of about 1 μm. Also in the die coater method, the coating thickness can be about 1 μm in recent years. .
Japanese Patent Laid-Open No. 11-197569 JP 2004-230361 A

  However, in the case of the micro gravure method, since the coating liquid is transferred to the substrate using a metal roll, wrinkles are generated on the surface of the substrate when the substrate is a metal.

  Also, when using the die coater method, in order to reduce the film thickness, it is necessary to bring the gap between the base material and the die that supplies the coating solution close to the desired coating film thickness, and a smooth glass substrate or the like is required. If it is a base material, it is possible to make it close, but in the case of a steel strip that runs continuously, shape variation occurs in both the width direction and the longitudinal direction, making it difficult to make the die close. In addition, when the die coater method is used, a defect called air entrainment occurs when high-speed application is performed, so that the application is limited to a low-speed region of about 10 mpm, and productivity is hindered.

  The present invention has been made in view of the above circumstances, and efficiently applies a thin film having a coating thickness of less than 0.1 μm after drying to a substrate that continuously runs at high speed without any defects. It is an object of the present invention to provide a roll coating method and a roll coating apparatus that can be used.

  In order to solve the above problems, the present invention has the following features.

[1] The amount of the coating liquid supplied to the pick-up roll is adjusted with a mitering roll, the adjusted amount of coating liquid is supplied to the applicator roll, and the applicator roll supplied with the coating liquid is In a roll coating method using a three-roll coater that contacts a continuously running substrate and applies a coating solution to the substrate surface,
In applying the coating solution so that the coating thickness after drying is less than 0.1 μm by running the substrate continuously at a high speed of 100 mpm or more, using the steel strip as the base material and the coating liquid as the water-based paint .
The concentration of the coating solution is set to 1% or more and 3.8% or less, and the coating film thickness is set to less than 3 μm. First, a pre-coater having at least one roll is used on the upstream side in the substrate running direction of the three-roll coater. Then, the surface of the base material to which the coating liquid is applied is precoated with a coating liquid having the same composition as the coating liquid applied with the three-roll coater, and then the coating liquid on the precoated base material is in a liquid state. A roll coating method, wherein a coating solution is applied to a substrate by the three-roll coater.

  [2] The roll coating method according to [1], wherein the roll in contact with the substrate is a rubber lining roll whose surface is polished.

[3] A roll coating apparatus used in the roll coating method according to [1] or [2],
A pickup roll supplied with the coating liquid, a metering roll for adjusting the amount of the coating liquid supplied to the pickup roll, and the coating liquid supplied from the pickup roll with the liquid amount adjusted A three-roll coater provided with an applicator roll for applying a coating solution to a continuously running substrate;
A coating liquid having the same composition as the coating liquid to be applied by the three-roll coater is pre-coated on the surface of the three-roll coater on the upstream side in the substrate running direction of the three-roll coater. And a pre-coater provided at a position where the pre-coated coating solution reaches the three-roll coater in a liquid state,
A roll coating apparatus, wherein the roll in contact with the substrate is a rubber lining roll whose surface is polished.

  In the present invention, a thin film having a coating film thickness of less than 0.1 μm after coating and drying can be efficiently coated without defects on a substrate that runs continuously at high speed.

  In order to reduce the film thickness after coating and drying, a method of diluting the coating liquid can be considered. However, it has been found that the appearance often deteriorates when diluted too much, and it is necessary to reduce the film thickness when it is applied to the substrate in a liquid state. The concentration that can be diluted varies slightly depending on the type of treatment liquid, and in some cases, even if there is an additive such as a surfactant, the film thickness is more uniform when applied at a concentration of about 1% or more. The result that it was easy to ensure the property and the good appearance was obtained. Therefore, in order to form a film having a film thickness of less than 0.1 μm after drying, it is considered that the thickness of the liquid film at the time of application needs to be less than 3 μm, preferably about 1 μm. We studied diligently.

  One embodiment of the present invention is described below.

  FIG. 1 is a diagram showing a roll coating apparatus used in an embodiment of the present invention. As shown in FIG. 1, the roll coating apparatus used in this embodiment applies (transfers) a coating solution by a roll to the surface of a substrate 1 that is continuously passed through, and includes a three-roll coater A, A precoater (precoat device) B is provided on the upstream side.

  The three-roll coater A includes a pickup roll 4 that draws up the coating liquid 3 from the coater pan 2, a metering roll 5 that adjusts the amount of the coating liquid on the pickup roll 4, and the adjusted coating liquid on the pickup roll 4. And an applicator roll 6 to be transferred to the substrate 1.

  The rotation direction of each roll 4, 5, 6 of the three-roll coater A is the reverse direction between each roll or between the applicator roll 6 and the substrate 1, and the blade that scrapes the coating liquid 3 on the mitering roll 5. 7 is installed.

  The applicator roll 6 that comes into contact with the substrate 1 uses a rubber lining roll whose surface is polished by lining rubber.

  On the other hand, the precoater B preliminarily applies the coating liquid to the substrate 1 at a position upstream of the three-roll coater A, and includes a precoat roll 9 and a coating liquid supply roll 10 that supplies the coating liquid to the precoat roll 9. The coater pan 12 filled with the coating liquid 13 is provided.

  The pre-coating roll 9 that comes into contact with the base material 1 uses a rubber lining roll that has a rubber lining and a polished surface. Further, a metal roll is used as the coating liquid supply roll 10.

  Here, the coater pan 12 is filled with the same type of coating solution 13 as the coating solution 3 applied to the substrate 1 with the three-roll coater A. Further, the precoater B is disposed at a position where the coating liquid 13 on the substrate 1 applied by the precoater B reaches the three-roll coater A while being in a liquid state.

  Then, using the roll coating apparatus configured as described above, the coating solution is applied to the continuously running substrate 1 so that the coating thickness after coating and drying is less than 0.1 μm. In this case, first, the coating liquid 13 is applied to the base material 1 by the precoater B, and then the coating liquid 13 on the base material 1 applied by the precoater B remains in a liquid state, on which the three-roll coater A is applied. The coating liquid 3 is applied by

  Usually, in the case of a roll coater that does not have a precoater as shown in FIG. 2, when a coating film thickness of less than 3 μm is applied to the substrate 1 (coating thickness after drying is less than 0.1 μm) In addition, streak patterns and blurring are likely to occur in the running direction of the substrate 1. The reason why the streaky pattern is generated is considered to be that the air flow accompanying the traveling substrate 1 disturbs the meniscus between the substrate 1 and the applicator roll 6. Further, the reason why the blur occurs is that when the applied film thickness is as thin as less than 3 μm, the amount of coating liquid transferred to the convex portion becomes extremely thin due to the influence of the irregularities on the surface of the substrate 1. This is thought to be due to the occurrence of liquid breakage. Therefore, in order to obtain a uniform coating film thickness in which no streak pattern is generated, the air accompanying the substrate 1 may be prevented from affecting the meniscus between the applicator roll 6 and the substrate 1.

  In one embodiment of the present invention shown in FIG. 1, the precoater B is installed on the upstream side of the three-roll coater A, and when the coating with a coating thickness of less than 0.1 μm is applied to the base material 1, Since the coating liquid 13 on the base material 1 applied with the precoater B remains in a liquid state and the coating liquid 3 is applied thereon with the three-roll coater A, the coating liquid previously applied to the base material 1 13 flows into the gap between the applicator roll 6 and the base material 1 and functions to block the air accompanying the traveling base material 1, thereby preventing the meniscus between the applicator rolls 6 from being disturbed and causing streaks. It is possible to obtain a uniform coating thickness without generating the pattern. In addition, since pre-coating is performed by the precoater B, it comes into contact with the applicator roll 6 in a state in which a coating film is formed on the surface of the base material 1, and generation of blurring is eliminated.

  In this manner, in this embodiment, a thin film having a coating thickness of less than 0.1 μm after drying can be efficiently applied to a substrate that continuously runs at a high speed without any defects.

  In addition, in said embodiment, although the case where the base material 1 is apply | coated to the single side | surface of the base material 1 in the state wound around the backup roll 8 as usual is shown, this invention is a base material. The present invention can also be applied to the case of simultaneous double-sided coating in which roll coaters are arranged on both sides of 1 and no backup roll is required. Furthermore, the plate-passing direction of the substrate 1 may be either a horizontal pass or a vertical pass.

  Moreover, although the case where 2 rolls are used as the precoater B is shown in the above embodiment, the number of rolls may be one or more, and a 1 roll coater or a 3 roll coater may be used. A three-roll coater is more desirable than a two-roll coater because it has higher film thickness controllability and is more advantageous, but it is expensive. If the liquid film thickness (precoat thickness) applied by the precoater B is less than 5 μm, the final film thickness is not affected. Therefore, when a coating liquid supply device capable of controlling the film thickness is provided, one roll But it's possible to achieve the goal. Moreover, although the rotation direction of the roll illustrated in the case of reverse rotation, it is not limited to this.

  Further, the supply method of the coating liquid in the precoater B may not be a method of pumping the coating solution 13 from the coater pan 12 but may be a method of spraying the coating solution from the nozzle to the roll.

  The invention is illustrated in detail by the following examples.

  As an embodiment of the present invention, a steel strip traveling speed of 100 mpm, an applicator roll is applied to a coil (steel strip) of a galvanized steel sheet having a thickness of 0.6 mm and a width of 1200 mm using the roll coating apparatus shown in FIG. The coating liquid is applied under the conditions of a peripheral speed of 120 mpm and a pick-up roll peripheral speed of 72 mpm, and the film thickness after drying and the evaluation of the coating appearance are evaluated, and the liquid film thickness at the time of application is determined from the coating liquid concentration, the film thickness after drying, and the film specific gravity. Was calculated. Coating liquids 3 and 13 are phosphoric acid-based water-based paints (containing phosphoric acid compound, Mg compound, silica, and tetravalent vanadium compound) (physical properties at a concentration of 3%, viscosity at a liquid temperature of 20 ° C .: 3 mPa · s, surface tension: 40 dyn / cm, specific gravity of the film: 1.2) was used by changing the concentration as appropriate. The same precoat liquid as the coating liquid was used. The film thickness of the precoat liquid is preliminarily performed in advance, and after the surface of the substrate 1 is dried, the film thickness after drying of the film formed on the surface is measured. Values calculated from specific gravity and coating solution concentration were used. The appearance of the coating was evaluated by visual observation under a sufficiently bright fluorescent lamp.

  For the three-roll coater A, the material of each roll is that the applicator roll 6 is a rubber lining roll, the pickup roll 4 is a metal roll, and the mitering roll 5 is a rubber lining roll. The roll diameter of each roll is the applicator roll. 6 and the pickup roll 4 were 300 mm, and the mitering roll 5 was 200 mm. The peripheral speed of the mitering roll 5 was adjusted in the range of 10 to 90 mpm so that the coating film thickness was constant.

  Regarding the precoater B, the material of each roll was such that the precoat roll 9 was a rubber lining roll, the coating liquid supply roll 10 was a metal roll, and the roll diameter was 250 mm. And it was made to become predetermined | prescribed coating film thickness (precoat thickness) by adjusting the peripheral speed and nip pressure of a roll.

  The results are shown in Table 1.

  As shown in Table 1, when the coating with the precoater B is not performed, the coating liquid film thickness is less than 3 μm, and when the film thickness after drying is less than 0.1 μm, a blur occurs (× mark), but the precoater B When the coating was applied (when the precoat thickness was 1.9 μm to 2.5 μm), no blur was generated even when the coating film thickness was less than 3 μm and the film thickness after drying was less than 0.1 μm (circle mark). ).

  In this example, a galvanized steel sheet was used as a base material. However, the present invention is not particularly limited to a steel sheet, and can be applied to other metal plates such as aluminum, paper, and films. .

It is a side view which shows the roll coating device used in one Embodiment of this invention. It is a side view which shows the conventional roll coating device.

Explanation of symbols

A 3 roll coater B precoater 1 substrate 2 coater pan 3 coating solution 4 pickup roll 5 mitering roll 6 applicator roll 7 blade 8 backup roll 9 precoat roll 10 coating solution supply roll 12 coater pan 13 coating solution

Claims (3)

The amount of the coating liquid supplied to the pick-up roll is adjusted with a metering roll, the adjusted amount of coating liquid is supplied to the applicator roll, and the applicator roll to which the coating liquid is supplied is continuously In a roll coating method using a three-roll coater that contacts a traveling substrate and coats the coating liquid on the substrate surface,
In applying the coating solution so that the coating thickness after drying is less than 0.1 μm by running the substrate continuously at a high speed of 100 mpm or more, using the steel strip as the base material and the coating liquid as the water-based paint .
The concentration of the coating solution is set to 1% or more and 3.8% or less, and the coating film thickness is set to less than 3 μm. First, a pre-coater having at least one roll is used on the upstream side in the substrate running direction of the three-roll coater. Then, the surface of the base material to which the coating liquid is applied is precoated with a coating liquid having the same composition as the coating liquid applied with the three-roll coater, and then the coating liquid on the precoated base material is in a liquid state. A roll coating method, wherein a coating solution is applied to a substrate by the three-roll coater.   The roll coating method according to claim 1, wherein the roll in contact with the substrate is a rubber lining roll whose surface is polished. A roll coating apparatus used in the roll coating method according to claim 1 or 2,
A pickup roll supplied with the coating liquid, a metering roll for adjusting the amount of the coating liquid supplied to the pickup roll, and the coating liquid supplied from the pickup roll with the liquid amount adjusted A three-roll coater provided with an applicator roll for applying a coating solution to a continuously running substrate;
A coating liquid having the same composition as the coating liquid to be applied by the three-roll coater is pre-coated on the surface of the three-roll coater on the upstream side in the substrate running direction of the three-roll coater. And a pre-coater provided at a position where the pre-coated coating solution reaches the three-roll coater in a liquid state,
A roll coating apparatus, wherein the roll in contact with the substrate is a rubber lining roll whose surface is polished.

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